- A high performance solid state asymmetric supercapacitor device based upon NiCo2O4 nanosheets//MnO2 microspheres
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A high performance solid state asymmetric supercapacitor (SSASCs) device is successfully fabricated by combining NiCo2O4 as positive and MnO2 as negative electrode materials. Herein, we also report a facile strategy to synthesize mesoporous layered NiCo2O4 nanosheets and 3D hierarchical MnO2 microspheres by a simple microwave heating method. Both materials exhibit excellent electrochemical performance due to their unique morphological features along with nanocrystallite size, high specific surface area, narrow pore size distribution and large pore volume. The SSASCs device operates within the potential window of 1.5 V and exhibits high volumetric capacity and energy density of 0.954 mA h cm-3 (2.3 F cm-3) and 0.715 mW h cm-3 at 1 mA cm-2 respectively. The device also demonstrates excellent cyclic stability with capacity retention of 83% by the end of 10000 cycles at a current density of 2 mA cm-2. This work constitutes the first demonstration of using 3D hierarchical MnO2 microspheres as a high energy negative electrode for a SSASCs device. A SSASCs device with high volumetric capacity and energy density has significant potential applications in portable electronics and electrical vehicles.
- Khalid, Syed,Cao, Chuanbao,Wang, Lin,Zhu, Youqi,Wu, Yu
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- Mesoporous β-MnO2 air electrode modified with pd for rechargeability in lithium-air battery
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The electrochemical performance and electrode reactions using ordered mesoporous β-MnO2 modified with Pd as a cathode catalyst for rechargeable Li-air batteries was reported. Well-ordered mesoporous β-MnO2 was prepared using mesoporous silica KIT-6 as a template under hydrothermal synthesis of Mn(NO3)2H2O. The obtained mesoporous β-MnO2 shows narrow pore size distribution of 1 nm. With the dispersion of small amounts of Pd to β-MnO2, mesoporous β-MnO2 exhibited a high initial discharge capacity of 817 mAhg-cat. with high reversible capacity. Charging potential is suppressed at 3.6 V vs. LiLi, which is highly effective for preventing the decomposition of organic electrolyte. The mesoporous β-MnO2Pd electrode shows good rate capability and cycle stability. Ex-situ and in-situ XRD results suggested that the observed capacity comes primarily from the oxidation of Li to Li2O 2 followed by Li2O after discharge to 2.0 V vs. LiLi. Electron spin resonance measurements suggest that the formation of superoxide anion radicals contributs to the oxidation of Li and the radicals were recovered during charge. Ex-situ FTIR measurement suggested that no electrolyte decomposition was observed and no Li2CO3 was formed during discharge when ethylene carbonate (EC)-diethyl carbonate (DEC) (3:7), which is highly stable for Li-air battery, was used as the electrolyte.
- Thapa, Arjun Kumar,Hidaka, Yuiko,Hagiwara, Hidehisa,Ida, Shintaro,Ishihara, Tatsumi
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- A new 3D supramolecular manganese(II) complex constructed from benzimidazole-5,6-dicarboxylate and Oxalate: Synthesis, structural, and magnetic properties
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A new manganese(II) complex [Mn3(bidc)2(C 2O4)(H2O)10]n (1) (bidc = benzimidazole-5,6-dicarboxylate) was synthesized and characterized by X-ray crystallography. X-ray diffraction shows that complex 1 has a neutral, one-dimensional (1D) brick wall chain structure. With the intramolecular and intermolecular hydrogen bonding interactions, the adjacent chains are joined into a 3D suparmolecular architecture. IR spectroscopy and variable temperature magnetic susceptibility measurements were made, which indicated weak antiferromagnetic coupling between the MnII ions in complex 1.
- Geng, Jin-Peng,Wang, Zhao-Xi,Wu, Qiong-Fang,Li, Ming-Xing,Xiao, Hong-Ping
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- Sonochemical preparation of stable porous MnO2 and its application as an efficient electrocatalyst for oxygen reduction reaction
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Porous MnO2 as a non-noble metal oxygen reduction reaction (ORR) electrocatalyst was prepared by a simple sonochemical route. The as-prepared porous MnO2 exhibited higher electrocatalytic activity, superior stability and better methanol tolerance than commercial Pt/C catalyst in alkaline media. Furthermore, the ORR proceeded via a nearly four-electron pathway. Cyclic voltammetry (CV) and rotating-disk electrode (RDE) measurements verified that the ORR enhancement was attributed to the porous structure and good dispersity, which facilitated sufficient transport of ions, electrons, O2 and other reactants in the process of ORR. The results indicated that a facile and feasible sonochemical route could be used to prepare highly active porous MnO2 electrocatalyst for ORR, which might be promising for direct methanol fuel cells.
- Zuo, Ling-Xia,Jiang, Li-Ping,Abdel-Halim,Zhu, Jun-Jie
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- Controllable explosion: fine-tuning the sensitivity of high-energy complexes
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Tuning the sensitivity of energetic materials has always been a research topic of interest. A lot of attention has been paid on changing the ligands previously used in traditional high energy density materials (HEDMs). Recently, we have stepped further along this path by thinking from another angle, i.e., changing the metal centre. Herein, we report 4 transition metal complexes bearing the 1,5-diaminotetrazole ligand, which have similar structures but drastically different sensitivities. These differences are apparently due to the different metal centres used.
- Wang, Kun,Zeng, Dihao,Zhang, Jian-Guo,Cui, Yan,Zhang, Tong-Lai,Li, Zhi-Min,Jin, Xin
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- Local atomic arrangement and electronic structure of nanocrystalline transition metal oxides determined by X-ray absorption spectroscopy
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The local crystal structure and electronic configuration of transition metal in X-ray amorphous MnO2 and CrO2 nanocrystals have been examined by using X-ray absorption (XAS) spectroscopy at Mn K and Cr K-edges. The Mn K-edge XAS study reveals that tetravalent manganese ions are stabilized in ?±-MnO2-type local atomic arrangement consisting of the intergrowth of edge- and corner-shared MnO6 octahedra. On the other hand, it is found from Cr K-edge XAS results that nanocrystalline CrO2 possesses two different kinds of local structures around chromium, that is, Cr2O3-type with octahedral site and CrO3-type with tetrahedral site. The presence of Cr+VI species on the surface would be helpful for Li grafting process, giving rise to excellent electrochemical performances. This work can be regarded as a strong evidence for the usefulness of XAS to study nanocrystalline electrode materials.
- Hwang, Seong-Ju,Choy, Jin-Ho
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- Kinetics of lab prepared manganese oxide catalyzed oxidation of benzyl alcohol in the liquid phase
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The oxidation of benzyl alcohol in the liquid phase was studied over manganese oxide catalyst using molecular oxygen as an oxidant. Manganese oxide was prepared by a mechanochemical process in solid state and was characterized by chemical and physical techniques. The catalytic performance of manganese oxide was explored by carrying out the oxidation of benzyl alcohol at 323-373 K temperature and 34-101 kPa partial pressure of oxygen. Benzaldehyde and benzoic acid were identified as the reaction products. Typical batch reactor kinetic data were obtained and fitted to the Langmuir-Hinshelwood, Eley-Rideal, and Mars-van Krevelene models of heterogeneously catalyzed reactions. The Langmuir-Hinshelwood model was found to give a better fit. Adsorption of benzyl alcohol at the surface of the catalyst followed the Langmuir adsorption isotherm. The heat of adsorption for benzyl alcohol was determined as -18.14 kJ mol-1. The adsorption of oxygen followed the Temkin adsorption isotherm. The maximum heat of adsorption for oxygen was -31.12 kJ mol-1. The value of activation energy was 71.18 kJ mol-1, which was apparently free from the influence of the heat of adsorption of both benzyl alcohol and oxygen.
- Saeed, Muhammad,Ilyas, Mohammad,Siddique, Mohsin
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- A novel self-assembly approach for synthesizing nanofiber aerogel supported platinum single atoms
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A great challenge in catalyst engineering is precisely assembling and positioning nanoscale active metals at desired locations while constructing robust functional architectures. This article presents a novel approach for constructing macroscopic Ag-doped manganese oxide aerogels (up to 2 L) while homogeneously incorporating active Pt single atoms (Pt/Ag-MnO2) based on a solution-solid-solid (SSS) mechanism. AgOx seeds were identified as key species for triggering the octopus-like growth of MnO2 nanofibers and inserting Ag and Pt into the MnO2 crystalline framework. The interconnection and entanglement among nanofibers allowed the formation of mechanically strengthened hierarchical structures, leading to one of the most robust manganese-based aerogels to date. Impressively, the Pt/Ag-MnO2 aerogel also possessed promising selectivity and stability toward the electrocatalytic oxygen reduction reaction, with Pt showing a high mass activity of 1.6 A/(mgPt) at 0.9 V vs. RHE. Experimental characterization and theoretical calculation confirmed Pt single atoms to be located at substitutional lattice sites, which reduced the overall oxygen reduction barriers. Our approach suggests that SSS or other analogous nanofiber or nanowire growth strategies are powerful in controlling structural formation over the entire range of length scales while being applicable to fabricating single-atom catalysts.
- Jiang, Zheng,Kato, Kenichi,Li, Xiaopeng,Lin, Chao,Sun, Yu,Xu, Qing,Yamauchi, Miho,Yang, Ruoou,Zhang, Hao,Zhang, Haojie,Zhao, Yonghui
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- Synthesis of NaxMnO2+δ by a reduction of aqueous sodium permanganate with sodium iodide
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Reduction of sodium permanganate with sodium iodide in aqueous solutions has been investigated systematically. The products formed have been characterized by X-ray diffraction, wet-chemical analysis, and surface area and magnetic susceptibility measurements after firing at various temperatures. The results reveal that the sodium content x in the reduction products NaxMnO2+δ depends strongly on the reaction pH and mildly on the relative concentrations of the reactants. Na0.7MnO2+δ obtained at pH>11 followed by firing at T>500°C adopts the P2 layer structure (hexagonal) with cation vacancies arising from a δ≈0.3. Na0.7 MnO2+δ crystallizing in a distorted P2 structure (orthorhombic) without cation vacancies (δ≈0) could be obtained by annealing the hexagonal Na0.7MnO2+δ (δ≈0.3) in N2 atmosphere around 600°C. While the orthorhombic Na0.7MnO2+δ (δ0.7MnO2+δ (δ≈0.3) transforms to spinel-like phases due to the presence of cation vacancies. Na0.5MnO2+δ obtained at a controlled pH of 9.3 adopts a metastable layer structure on firing at 500°C and a tunnel structure isostructural with Na4Mn4Ti5O18 on firing at T≥600°C. The tunnel structure is stable to ion-exchange reactions without transforming to spinel-like phases. In addition, washing the reduction products with various organic solvents before firing at higher temperatures is found to influence the reaction kinetics, composition, and crystal chemistry.
- Jeong,Manthiram
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- Synthesis of boron/nitrogen substituted carbons for aqueous asymmetric capacitors
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Boron/nitrogen substituted carbons were synthesized by co-pyrolysis of polyborazylene/coal tar pitch blends to yield a carbon with a boron and nitrogen content of 14 at% and 10 at%, respectively. The presence of heteroatoms in these carbons shifted the hydrogen evolution overpotential to -1.4 V vs Ag/AgCl in aqueous electrolytes, providing a large electrochemical potential window (～2.4 V) as well as a specific capacitance of 0.6 F/m2. An asymmetric capacitor was fabricated using the as-prepared low surface area carbon as the negative electrode along with a redox active manganese dioxide as the positive electrode. The energy density of the capacitor exceeded 10 Wh/kg at a power density of 1 kW/kg and had a cycle life greater than 1000 cycles.
- Tomko, Timothy,Rajagopalan, Ramakrishnan,Aksoy, Parvana,Foley, Henry C.
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- Capacitive properties of PANI/MnO2 synthesized via simultaneous-oxidation route
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Polyaniline (PANI) and manganese dioxide (MnO2) composite (PANI/MnO2) was synthesized via a simultaneous-oxidation route. In this route, all reactants were dispersed homogenously in precursor solution and existed as ions and molecules, and involved reactions of ions and molecules generating PANI and MnO2 simultaneously. In this way, PANI molecule and MnO2 molecule contact each other and arrange alternately in the composite. The inter-molecule contact improves the conductivity of the composite. The alternative arrangement of PANI molecules and MnO2 molecules separating each other, and prevents the aggregation of PANI and cluster of MnO2 so as to decrease the particle size of the composite. The morphology, structure, porous and capacitive properties are characterized by scanning electron microscopy, X-ray diffraction spectroscopy, X-ray photoelectron spectroscopy, Branauer-Emmett-Teller test, thermogravimetric analysis, Fourier transform infrared spectroscopy, cyclic voltammetry, charge-discharge test and the electrochemical impedance measurements. The results show that MnO2 is predominant in the PANI/MnO2 composite and the composite exhibits larger specific surface area than pure MnO2. The maximum specific capacitance of the composite electrode reaches up to 320 F/g by charge-discharge test, 1.56 times higher than that of MnO2 (125 F/g). The specific capacitance retains approximately 84% of the initial value after 10,000 cycles, indicating the good cycle stability.
- Zhang, Jie,Shu, Dong,Zhang, Tianren,Chen, Hongyu,Zhao, Haimin,Wang, Yongsheng,Sun, Zhenjie,Tang, Shaoqing,Fang, Xueming,Cao, Xiufang
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- Sorption and oxidation of tetravalent plutonium on Mn oxide in the presence of citric acid
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Sorption experiments of PuIV on synthetic Mn oxide were made in 0.1 M NaCl + 0.1 mM sodium citrate solutions under acidic to alkaline pH conditions. As the results of the sorption experiments, Pu was efficiently removed from the solutions under neutral pH conditions, where Pu forms the stable 1:2 PuIVcitrate complex. Furthermore, it was demonstrated that Pu IV was oxidized to Puv and PuVI on Mn oxide. Copyright
- Tanaka, Kazuya,Suzuki, Yoshinori,Ohnuki, Toshihiko
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- A comparison study of MnO2and Mn2O3as zinc-ion battery cathodes: An experimental and computational investigation
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The high specific capacity, low cost and environmental friendliness make manganese dioxide materials promising cathode materials for zinc-ion batteries (ZIBs). In order to understand the difference between the electrochemical behavior of manganese dioxide materials with different valence states, i.e., Mn(iii) and Mn(iv), we investigated and compared the electrochemical properties of pure MnO2 and Mn2O3 as ZIB cathodes via a combined experimental and computational approach. The MnO2 electrode showed a higher discharging capacity (270.4 mA h g-1 at 0.1 A g-1) and a superior rate performance (125.7 mA h g-1 at 3 A g-1) than the Mn2O3 electrode (188.2 mA h g-1 at 0.1 A g-1 and 87 mA h g-1 at 3 A g-1, respectively). The superior performance of the MnO2 electrode was ascribed to its higher specific surface area, higher electronic conductivity and lower diffusion barrier of Zn2+ compared to the Mn2O3 electrode. This study provides a detailed picture of the diversity of manganese dioxide electrodes as ZIB cathodes. This journal is
- Shen, Hongyuan,Liu, Binbin,Nie, Zanxiang,Li, Zixuan,Jin, Shunyu,Huang, Yuan,Zhou, Hang
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- Self-organized honeycomb structures of Mn12 single-molecule magnets
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In this paper, Mn12-based ordered honeycomb structures were successfully constructed from a simple solution casting process at high relative humidity through the modification of fatty acids to Mn12 clusters. Mn12-fatty aci
- Sun, Hang,Li, Wen,Wollenberg, Lance,Li, Bao,Wu, Lixin,Li, Fengyan,Xu, Lin
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- Catalytic effects of metal oxides on the decomposition of Potassium perchlorate
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Catalytic effects of metal oxides with comparable surface areas on the decomposition of potassium perchlorate were studied by thermogravimetric analysis. The catalytic mechanism is discussed based on the relative activity of the metal oxides. It is found
- Zhang, Yunchang,Kshirsagar, Girish,Ellison, John E.,Cannon, James C.
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- Structure and electrochemical performance of hollow microspheres of LiFexNi1/3-xCo1/3Mn1/3O2 (0.000 ≤ x ≤ 0.267) as cathodes for lithium-ion batteries
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LiFexNi1/3-xCo1/3Mn1/3O2 (0.000 ≤ x ≤ 0.267) hollow microspheres have been synthesized by an approach using manganese carbonate microspheres as self-templates and substituting stoichiometric iron for nickel. XRD analysis shows that the obtained materials have a layered α-NaFeO2 structure (rhombohedral lattice, R3m space group). With the addition of iron, the lattice parameters of these samples increase in the low-x region (x ≤ 0.133) and reach their maximum values at x = 0.133. The behavior of the lattice parameters is consistent with their specific capacities at 0.1 C rate, which means moderate substitution of iron can enhance the performance. Meanwhile, the iron substitution destroys the hollow microspheres and results in microsphere aggregation, which can be found from their surface morphologies using the SEM analysis. Compared with the others, when x is equal to 0.133, the sample exhibits a relatively superior electrochemical performance.
- Chang, Qing,Zhang, Heng,Wang, Xujun,Shao, Weiquan,Li, Hongliang,Yuan, Feng,Xu, Xiangang,Xu, Sheng
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- Ethanol tolerant precious metal free cathode catalyst for alkaline direct ethanol fuel cells
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La0.7Sr0.3(Fe0.2Co0.8)O3 and La0.7Sr0.3MnO3 ?based cathode catalysts are synthesized by the sol-gel method. These perovskite cathode catalysts are tested in half cell configuration and compared to MnO2 as reference material in alkaline direct ethanol fuel cells (ADEFCs). The best performing cathode is tested in single cell setup using a standard carbon supported Pt0.4Ru0.2 based anode. A backside Luggin capillary is used in order to register the anode potential during all measurements. Characteristic processes of the electrodes are investigated using electrochemical impedance spectroscopy. Physical characterizations of the perovskite based cathode catalysts are performed with a scanning electron microscope (SEM) and by X-ray diffraction showing phase pure materials. In half cell setup, La0.7Sr0.3MnO3 shows the highest tolerance toward ethanol with a performance of 614 mA cm?2 at 0.65 V vs. RHE in 6 M KOH and 1 M EtOH at RT. This catalyst outperforms the state-of-the-art precious metal-free MnO2 catalyst in presence of ethanol. In fuel cell setup, the peak power density is 27.6 mW cm?2 at a cell voltage of 0.345 V and a cathode potential of 0.873 V vs. RHE.
- Grimmer, Ilena,Zorn, Paul,Weinberger, Stephan,Grimmer, Christoph,Pichler, Birgit,Cermenek, Bernd,Gebetsroither, Florian,Schenk, Alexander,Mautner, Franz-Andreas,Bitschnau, Brigitte,Hacker, Viktor
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- Factors influencing the structure of electrochemically prepared α-MnO2 and γ-MnO2 phases
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The α- and γ-phases of MnO2 prepared by electrolysis of MnSO4 and MxSO4 (where M = Li+, Na+, K+, Rb+, Cs+ or Mg2+) in aqueous solutions at various pH and voltage Ev values under ambient conditions have been systematically studied. The structures of powdery MnO2 produced are found to depend on the radius of the Mz+ counter cation in addition to the pH and Ev conditions. In order to achieve the α-phase for MnO2 formation under neutral pH condition, the radius of counter cation must be equal to or greater than 1.41 A?, the size of the K+ cation. The relative concentration ratio of [MnO4-]transient/[Mn2+], which is related to the pH-Ev conditions, also affects the structure of MnO2 produced with counter ions smaller than K+. For samples prepared in acidified solution with the counter ions of Li+, Na+ or Mg2+ at 2.2 V, the electrolysis products display the γ-MnO2 phase while those prepared at 2.8 V electrolysis produce a mixture of γ-MnO2 and α-MnO2 phases. Single phase of α-MnO2 is identified in the 5 V electrolysis products. Furthermore, the valence state of manganese was found to decrease as the applied voltage was reduced from 5.0 to 2.2 V. This implies that the lower [MnO4-]transient/[Mn2+] ratio or the less oxidative condition is responsible for the non-stoichiometric MnO2 structure with oxygen deficiency.
- Lin,Sun,Weng,Yang,Suen,Liao,Huang,Ho,Chong,Tang
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- Disordered Co1.28Mn1.71O4 as a visible-light-responsive photocatalyst for hydrogen evolution
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Catching the sunlight: The disordered Co1.28Mn 1.71O4 was synthesized by a facile reduction method in the presence of amorphous MnO2 precursors and Co2+. It exhibits relatively high hydrogen-production activity under visible-light irradiation (see figure). The larger number of active sites in the bulk catalyst endow nanoparticles with improved water-reduction activity. This is the first demonstration of disordered ternary oxides for visible-light-driven hydrogen evolution in the absence of a cocatalyst. Copyright
- Chen, Zu Peng,Xing, Jun,Jiang, Ha Bo,Yang, Hua Gui
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- MnO2-coated Ni nanorods: Enhanced high rate behavior in pseudo-capacitive supercapacitor
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Ni nanorods prepared by electrochemical growth through an anodized aluminium oxide membrane were used as substrate for the electrodeposition of MnO2 either in potentiostatic mode or by a pulsed method. Electrochemical deposition parameters were chosen for an homogeneous deposit onto Ni nanorods. Resulting Ni supported MnO2 electrodes were tested for electrochemical performances as nanostructured negative electrodes for supercapacitors. They exhibited initial capacitances up to 190 F/g and remarkable performances at high charge/discharge rates.
- Lei,Daffos,Taberna,Simon,Favier
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- LiNi0.5Mn1.5O4 nano-submicro cubes as high-performance 5?V cathode materials for lithium-ion batteries
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High-voltage spinel LiNi0.5Mn1.5O4 is considered the most promising cathode materials for large-scale lithium-ion batteries to meet the fast increasing high energy and power density requirements. However, its commercial applications are restricted due to rigorous capacity fading, particularly at high temperatures. Herein, we propose novel highly uniform nano/submicro LiNi0.5Mn1.5O4 cubes for the first time using cubic MnCO3 precursors, which are prepared via a facile co-precipitation route. The as-synthesized LiNi0.5Mn1.5O4 demonstrates excellent cycle stability and superior rate capability. Specifically, the materials retain a nearly 100% capacity retention after 100 cycles at 25?°C. Moreover, under the elevated temperature of 55?°C, it can deliver a discharge capacity of 131.7?mAh?g?1 with the specific energy of 605.1?Wh?Kg?1 and even over 98.4% of primal discharge capacity can be maintained for up to 100 cycles.
- Wu, Yu,Zhang, Junting,Cao, Chuanbao,Khalid, Syed,Zhao, Quanqing,Wang, Ran,Butt, Faheem K.
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- Sodium-ion-assisted hydrothermal synthesis of γ-MN O2 and its electrochemical performance
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A γ-Mn O2 nanomaterial was synthesized by hydrothermally treating an amorphous manganese oxide, which was obtained by the reaction between NaMn O4 and MnS O4 at ambient conditions. It is only in a narrow range of adding an
- Lv, Dongping,Huang, Xingkang,Yue, Hongjun,Yang, Yong
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- Photocurrent generation from semiconducting manganese oxide nanosheets in response to visible light
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Unilamellar nanosheet crystallites of manganese oxide generated the anodic photocurrent under visible light irradiation (?? a??0.5 nm may facilitate the charge separation of excited electrons and holes, which is generally very difficult for strongly localized d-d transitions. The monolayer film of MnO2 nanosheets exhibited the incident photon-to-electron conversion efficiency of 0.16% in response to the monochromatic light irradiation (?? = 400 nm), which is comparable to those for sensitization of monolayer dyes adsorbed on a flat single-crystal surface. The efficiency declined with increasing the layer number of MnO2 nanosheets, although the optical absorption was enhanced. The recombination of the excited electron-hole pairs may become dominant when the carriers need to migrate a longer distance than 1 layer through multilayered nanosheets. ? 2005 American Chemical Society.
- Sakai, Nobuyuki,Ebina, Yasuo,Takada, Kazunori,Sasaki, Takayoshi
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- A template-free method for preparation of MnO2 catalysts with high surface areas
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High surface-area manganese oxides catalysts are widely employed in catalytic oxidation of volatile organic compounds (VOCs) because of their high efficiency and good stability. However, template agents are usually introduced to the synthesis process to create the high surface area (>150 m2/g). It is quite expensive and complicated, restricting the widespread applications. Herein, a template-free method was reported here to prepare high surface-area MnO2 catalysts by selectively removing La elements from LaMnO3 perovskites using acid treatment. The obtained MnO2 catalysts possessed excellent catalytic activity in toluene oxidation. Besides, the reserved La elements after acid treatment could be recycled to repeat the preparation process. After three cyclic processes, the catalytic performances were improved gradually, which may provide the possibility for the practical application in VOCs elimination.
- Wei, Yonghui,Ni, Lei,Li, Minxia,Zhao, Jili
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- Oxidative Cleavage of S–S Bond During the Reduction of Tris(pyridine-2-carboxylato)manganese(III) by Dithionite in Sodium Picolinate–Picolinic Acid Buffer Medium
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The reduction of tris(pyridine-2-carboxylato)manganese(III) by dithionite has been investigated within the temperature window 288–303 K and at pH range 5.22–6.10 in sodium picolinate–picolinic acid buffer medium. The reaction obeys the following stoichiometry: S2O2- 4 + 2MnIII + 2H2O → 2HSO- 3 + 2MnII + 2H+ The reaction is described in terms of a mechanism that involves an initial complex formation between S2O4 2? and [MnIII(C5H4NCO2)3] followed by S–S bond cleavage to give 2HSO3 ? and [MnII(C5H4NCO2)2(H2O)2] as the products via the formation of SO2 ●? radical anion. Kinetics and spectrophotometric evidences are cited in favor of the suggested mechanism. Thermodynamic parameters associated with the equilibrium step and the activation parameters with the rate-determining step have been computed.
- Sen Gupta, Kalyan K.,Bhattacharjee, Nandini,Pal, Biswajit
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- Spectroscopic and electrochemical properties of mononuclear Mn(III) complex and of binuclear di-μ-oxo bridged Mn(III) and Mn(IV) complex with isocyclam
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trans-[MnIIIisocyclamCl2]Cl·2H2O and [MnIIIMnIV(μ-O)2isocyclam 2](ClO4)3·2H2O (isocyclam = 1,4,7,11-tetraazacyclotetradecane) were synthesised an
- Tomczyk,Andrijewski,Nowak,Urbaniak,Sroczyński
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- Synthesis, spectroscopic characterization, thermal, and photostability studies of 2-(2′-hydroxy-5′-phenyl)-5-aminobenzotriazole complexes
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Three Mn(II), Co(II), and Cu(II) new transition metal complexes of the fluorescence dye: 2-(2′-hydroxy-5′-phenyl)-5-aminobenzotriazole/PBT derived from o-aminophenol and m-phenylenediamine have been synthesized. The structural interpretations were confirmed from elemental analyses, magnetic susceptibility and molar conductivity, as well as from mass, IR, UV-Vis spectral studies. From the analytical, spectroscopic, and thermal data, the stoichiometry of the mentioned complexes was found to be 1:2 (metal:ligand). The molar conductance data revealed that all the metal chelates are non-electrolytes and the chloride ions exist inside the coordination sphere. The thermal stabilities of these complexes were studied by thermogravimetric (TG/DTG) and the decomposition steps of these three complexes are investigated. The kinetic parameters such as the energy of activation (E*), pre-exponential factor (A), activation entropy (ΔS*), activation enthalpy (ΔH*), and free energy of activation (ΔG*) have been reported. Photostability of phenyl benzotriazole as fluorescence dye and their metal complexes doped in polymethyl methacrylate/PMMA were exposed to UV-Vis radiation and the change in the absorption spectra was achieved at different times during irradiation period.
- Refat, Moamen S.
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- Synthesis, Crystal Structures, Reactivity, and Magnetochemistry of a Series of Binuclear Complexes of Manganese(II), -(III), and -(IV) of Biological Relevance. The Crystal Structure of IV(μ-O)3MnIVL'>(PF6)2*H2O Containing an Unprecedented Short Mn...Mn Distance of 2.296 Angs...
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The disproportionation reactions of two binuclear complexes of manganese(III) containing the oxo-bis(acetato)dimanganese(III) core and two 1,4,7-triazacyclononane (L) capping ligands (1) or two N,N',N''-trimethyl-1,4,7-triazacyclononane (L') ligands (2) in aqueous solution under anaerobic conditions lead to a variety of novel binuclear MnIIIMnIV and MnIV2 dimers.These are the following: IIIMnIV(μ-O)2(μ-CH3CO2)>2*CH3CN (5); IIIMnIV(μ-O)(μ-CH3CO2)2>(ClO4)3 (6); IV2(OH)2(μ-O)2>II3(C2O4)4(OH2)2>*6H2O (7); and IV2(μ-O)3>(PF6)2*H2O (9).A tetranuclear species IV4O6>Br4*5.5H2O (8) is generated as a thermodynamically very stable product from a MnII containing aqueous solution of L in the presence of oxygen.In the absence of oxygen methanolic solutions of Mn(ClO4)2*2H2O or manganese(II) acetate react with L' to form II2(μ-OH)(μ-CH3CO2)2>(ClO4) (3) and II2(μ-CH3CO2)3> (4).The oxo- and acetato-bridges in 1 and 2 are labile; addition of anions X- (X=Cl, Br, NCS, N3) to acetonitrile solutions of 1 or 2 yields the monomers LMnX3 and L'MnX3.The electrochemistry of all compounds has been investigated; for example, 2 is reversibly oxidized by two one-electron processes to generate MnIIIMnIV and MnIV2 dimers in liquid SO2.The crystal structures of 4, 7, 8, and 9 have been determined by X-ray crystallography: 4, orthorhombic Pcab, a = 17.368(5) Angstroem, b = 17.538(5) Angstroem, c = 33.21(1) Angstroem, Z = 8; 7, monoclinic C2/c, a = 13.391(3) Angstroem, b = 16.571(4) Angstroem, c = 19.312(4) Angstroem, β = 109.82(2) degree, Z = 4; 8, monoclinic P21/c, a = 17.548(8) Angstroem, b = 13.118(7) Angstroem, c = 212.56(1) Angstroem, β = 105.63(4) degree, Z = 4; 9, orthorhombic Pnma, a = 10.057(5) Angstroem, b = 16.12(1) Angstroem, c = 19.237(8) Angstroem, Z = 4. 9 consists of the cofacial bioctahedral cation IV(μ-O)3MnIVL'>2+ and PF6 anions.The Mn...Mn distance is unusually short (2.296(2) Angstroem).Bulk magnetic properties of all compouds have been studied between 100 and 298 K, and in some instances 4 and 298 K.In 2 the MnIII ions are ferromagnetically coupled, J = +18(1) cm-1; whereas the MnII centers in 4 are weakly antiferromagnetically coupled, J = -3.5(2) cm-1.Very strong intramolecular antiferromagnetic coupling is observed in 9 (J = -780 cm-1).
- Wieghardt, Karl,Bossek, Ursula,Nuber, Bernhard,Weiss, Johannes,Bonvoisin, J.,et al.
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- An ellipsometric study of manganese oxide films: In situ characterization of the deposition and electroreduction of MnO2
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The electrodeposition of manganese oxide films onto a platinum substrate was investigated by means of in situ ellipsometry. In the thickness range from 0 to 150 nm, the anodic oxide behaves as an Isotropic single layer with optical constants that are independent of thickness. Deviations at higher thickness are explained in terms of anisotropic properties of the film. The electroreduction of thin films (up to ca. 150 nm) in an alkaline electrolyte leads to a decrease in both the refractive index and the extinction coefficient and is accompanied by a thickness increase of ca. 10%. The Mn(IV) to Mn(III) conversion takes place from the oxide/electrolyte interface inwards.
- Ubeda, M. Hernandez,Perez,Mishima,Villullas,Zerbino,De Mishima, B.A. Lopez,Teijelo, M. Lopez
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- Bifunctional pyrimidine-amino-acid ligands: Solution study and crystal structure of a Mn(II) chain alternating six- and sevenfold coordination environments
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The acid-base characterization in aqueous solution of the N-2-[4-amino-1,6-dihydro-1-methyl-5-nitroso-6-oxopyrimidinyl)methionine, a member of a family of bifunctional N-pyrimidine α-amino acids ligands, has been carried out by potentiometric and UV-Vis techniques in the 2.5-9.0 pH range, indicating a quasi-zwitterionic structure. The solution study of the HL/Mn(II) system at 1:2, 2:1 and 4:1 molar ratios (25°C and pHA solid complex with MnL2·612H2O stoichiometry was isolated from an aqueous 1:3 [HL]/[Mn(II)] mixture at pH 6. The X-ray single-crystal characterization has revealed that this complex can be formulated as {[Mn(H 2O)4(μ-L)2Mn(L)2(H 2O)]·8H2O}n, an infinite chain in which two different Mn(II) ions having six- and sevenfold coordination environments alternate along the chain. The asymmetric unit contains two ligands coordinating in different fashion. One of these coordinates monodentately through the oxygen atom belonging to the exocyclic nitroso group while the other exhibits a 3η-bridging pattern between the six- and sevenfold Mn(II) arrangements. The versatile coordination modes of this ligand is discussed and compared to other complexes of this bifunctional family of ligands.
- López-Garzón,Arranz-Mascarós,Godino-Salido,Gutiérrez-Valero,Cuesta,Moreno
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- A New Permanganate-Nitrite-Formic Acid-Methanol Oscillater
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Sustained oscillation and birhythmicity have been observed when aqueous solutions of potassium permanganate, potassium nitrite, formic acid, and methanol were mixed in a continuous-flow stirred tank reactor.A detailed phase diagram is shown.This new oscillator is composed of non-halogen compounds and the first example of the nitrogen-based oscillator.
- Morita, Makoto,Iwamoto, Kazutoshi,Seno, Manabu
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- Cathodic behavior of alkali manganese oxides from permanganate
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The reaction of potassium, sodium, and lithium permanganate in water at 170°C leads directly to potassium, sodium, and lithium manganese dioxides, AyMnO · nH2O, with a R3m rhombohedral structure. These crystalline layered structures after dehydration readily and reversibly react with lithium through an intercalation mechanism. The capacity for lithium is a function of the alkali ion present, and the larger potassium ion maintains the capacity best. For lithium there is a tendency to convert to the spinel structure which leads to loss of capacity.
- Chen, Rongji,Whittingham, M. Stanley
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- 1D slide-fastener-like coordination polymers of Mn(II) derived from pyrazine-2,3,5,6-tetracarboxylic acid
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Two new 1D slide-fastener-like coordination polymers {[Mn2(pztc)(phen)2(H2O)2]·4H2O}n (1) and {[Mn2(pztc)(bpy)2(H2O)2]·2H2O}n (2) have been synthesized by the reactions of pyrazine-2,3,5,6-tetracarboxylic acid (pztcH4) and Mn(OAc)2·4H2O in the presence of 1,10-phenanthroline (phen) or 2,2′-bipyridine (bpy) under hydrothermal conditions and characterized by elemental analyses, FT-IR, TGA and X-ray diffraction. In complex 1 and 2, metal ions are bridged by pyrazine-2,3,5,6-tetracarboxylate, coordinating in a hexadentate manner, so forming 1D polymeric chains. The remaining coordination sites of the metal ions are occupied by one O atom of water molecule and two N atoms of the terminal ligand (phen or bpy). IR spectra and thermal analysis data are in agreement with the crystal structure.
- Gao, Hong-Ling,Zhang, Yan-Ping,Yang, Ai-Hong,Fang, Su-Rong,Cui, Jian-Zhong
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- Enhanced anode performance of manganese oxides with petal-like microsphere structures by optimizing the sintering conditions
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Herein, the rational design and synthesis of manganese oxides (MnO2 and MnO) have been achieved and both of them show petal-like microsphere structures. As anodes for LIBs, MnO exhibits a higher capacity of 751.4 mA h g-1 after 400 cycles (492.7 mA h g-1 for MnO2 after 300 cycles) at 2000 mA g-1.
- Yu, Wei,Jiang, Xiaojian,Meng, Fanhui,Zhang, Zhonghua,Ma, Houyi,Liu, Xizheng
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- Double-Exchange Effect in Two-Dimensional MnO2 Nanomaterials
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Electronic state transitions, especially metal-insulator transitions (MIT), offer physical properties that are useful in intriguing energy applications and smart devices. But to-date, very few simple metal oxides have been shown to undergo electronic state transitions near room temperature. Herein, we demonstrate experimentally that chemical induction of double-exchange in two-dimensional (2D) nanomaterials brings about a MIT near room temperature. In this case, valence-state regulation of a 2D MnO2 nanosheet induces a Mn(III)-O-Mn(IV) structure with the double-exchange effect, successfully triggering a near-room-temperature electronic transition with an ultrahigh negative magneto-resistance (MR). Double-exchange in 2D MnO2 nanomaterials exhibits an ultrahigh MR value of up to -11.3% (0.1 T) at 287 K, representing the highest reported negative MR values in 2D nanomaterials approaching room temperature. Also, the MnO2 nanosheet displays an infrared response of 7.1% transmittance change on going from 270 to 290 K. We anticipate that dimensional confinement of double-exchange structure promises novel magneto-transport properties and sensitive responses for smart devices.
- Peng, Xu,Guo, Yuqiao,Yin, Qin,Wu, Junchi,Zhao, Jiyin,Wang, Chengming,Tao, Shi,Chu, Wangsheng,Wu, Changzheng,Xie, Yi
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- Incorporation of impurity metal ions in electrolytic manganese dioxide
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The amounts of impurity metal ions incorporated into electrolytic manganese dioxide (EMD) during its preparation were measured as a function of metal ion concentrations and current densities. The amount of incorporated ions increased in proportion to the concentration in solution, and at a fixed concentration it was different from ion to ion: Ni2+2+2+2+3+ 2+. The specific surface area of the formed EMD was larger for impurity ions with higher incorporation affinity. Further, the adsorption of ions on the surface of a ready-made manganese dioxide sample (IC12) was examined, and modeling of the adsorption behavior was attempted. The amounts of adsorbed ions at a fixed concentration in solution and pH 0.7 (where EMD is produced) were obtained by the ion-adsorption model. There was a strong correlation between the amount incorporated and the amount of adsorption, suggesting a mechanism in which EMD is contaminated through adsorption on its new growing surface. The increase in specific surface area of EMD with contaminants was interpreted to be due to a suppression of the growth of EMD at the adsorbed foreign ion sites, resulting in EMD with many defects or smaller particle sizes. The opposite effect of current density on incorporation for the two groups of metal ions was discussed.
- Tamura,Ishizeki,Nagayama,Furuichi
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- Power loss and energy density of the asymmetric ultracapacitor loaded with molybdenum doped manganese oxide
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Ultracapacitors of asymmetric configuration have been prepared with activated carbon (AC) and undoped or Mo-doped manganese oxide (MnO2) in 1.0 M Na2SO4 electrolyte. Phase analysis shows the AC powder, 1-15 μm in size, contains both disordered and graphitic structures, and the undoped and Mo-doped oxide powder, 0.05-0.20 μm in particle size, mainly involves amorphous MnO2 and MoO2. CV results indicate the single electrode of AC plus 10 wt% Mo-doped MnO2 (A9OM1) is superior to the electrode with undoped MnO2 or high content of doped MnO2, exhibiting features of double layer capacitance at high scan rate and pseudocapacitance characteristics at low scan rate. When assembled with a negative electrode of AC, the capacitor of positive A9OM1 electrode demonstrates the least power loss among three asymmetric capacitors. This asymmetric capacitor also shows a higher capacitance than the symmetric AC capacitor when the current density is less than 8.0 A g-1 in 1.8 V potential window. But a higher electrode resistance of A9OM1, in contrast with AC, compromises its capacitance plus. When the energy density of A9OM1 asymmetric capacitor is compared with that of symmetric AC capacitor at the same power level, the capacitance benefit on energy density is restricted to current density ≤ 3.0 A g-1.
- Wang, Yue-Sheng,Tsai, Dah-Shyang,Chung, Wen-Hung,Syu, Yong-Sin,Huang, Ying-Sheng
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- Cycle stability of birnessite manganese dioxide for electrochemical capacitors
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A combination of step potential electrochemical spectroscopy (SPECS) and electrochemical impedance spectroscopy (EIS) has been used to examine the electrochemical cycling behaviour of a well-characterized birnessite-phase manganese dioxide sample for use in electrochemical capacitors. The resistance and interfacial properties of the macroscopic electrode were found to be irreversible with cycling. However, the corresponding properties for the individual particles were more reversible, although they did show substantial hysteresis in their behaviour during cycling. This behaviour was discussed in terms of the structural, conductivity and morphological characteristics of the birnessite at different depths of discharge.
- Cormie, Ariana,Cross, Andrew,Hollenkamp, Anthony. F.,Donne, Scott W.
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- One-step synthesis of hollow urchin-like Ag2Mn8O16 for long-life Li-O2 battery
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To solve the critical issues like high polarization and unstable cycle ability, it is vital to design low-cost, stable and efficient catalytic cathode material for nonaqueous Li-O2 batteries (LOBs). Herein, a hollow urchin-like hollandite Ag2Mn8O16 electrocatalyst is fabricated by one-step hydrothermal method. The mixed bimetallic oxide with diverse valences (Mn3+ and Mn4+) and active oxygen defects provide sufficient active sites, and Ag[sbnd]Mn[sbnd]O bonds accelerate charge transformation. LOBs with the well-designed porous Ag2Mn8O16 cathode show superior electrochemical performances in LOBs, including ultrahigh specific capacity (7912 mAh gc?1 at 100 mA gc?1), good rate performance (5076 mAh gc?1 at 250 mA gc?1, 64.16%) and long-term cycle stability (320 cycles at 100 mA gc?1 within a limited capacity of 250 mAh gc?1 and 133 cycles at 200 mA gc?1 within a limited capacity of 500 mAh gc?1). This work provides a positive effect on designing better catalytic cathode materials for LOBs and push forward the commercialization progress.
- Ci, Lijie,Dai, Linna,Guo, Huanhuan,Li, Deping,Li, Jianwei,Liao, Jialin,Lu, Jingyu,Nie, Xiangkun,Sun, Qing,Xiao, Shenyi,Yao, Yuqing
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- Technetium(I) Carbonyl Chemistry with Small Inorganic Ligands
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[Tc(OH2)(CO)3(PPh3)2](BF4) has been used as a synthon for reactions with small inorganic ligands with relevance for the treatment of nuclear waste solutions such as nitrate, nitrite, pseudohalides, permetalates (M = Mn, Tc, Re), and BH4-. The formation of bond isomers and/or a distinct reactivity has been observed for most of the products. [Tc(NCO)(CO)3(PPh3)2], [Tc(NCS)(CO)3(PPh3)2], [Tc(CN)(CO)3(PPh3)2], [Tc(N3)(CO)3(PPh3)2], [Tc(NCO)(OH2)(CO)2(PPh3)2], [Tc(η2-OON)(CO)2(PPh3)2], [Tc(η1-NO2)(CO)3(PPh3)2], [Tc(η2-OONO)(CO)2(PPh3)2], [Tc(η1-ONO2)(CO)3(PPh3)2], [Tc(η2-OO(CCH3))(CO)2(PPh3)2], [Tc(η2-SSC(SCH3))(CO)2(PPh3)2], [Tc(η2-SSC(OCH3))(CO)2(PPh3)2], [Tc(η2-SSC(CH3))(CO)2(PPh3)2], [Tc(η2-SS(CH))(CO)2(PPh3)2], [Tc(OTcO3)(acetone)(CO)2(PPh3)2], [Tc(OTcO3)(CO)3(PPh3)2], and [Tc(η2-HHBH2)(CO)2(PPh3)2] have been isolated in crystalline form and studied by X-ray crystallography. Additionally, the typical reactivity patterns (isomerization, thermal decomposition, hydrolysis, or decarbonylation) of the products have been studied by spectroscopic methods. 99Tc NMR spectroscopy has proved to be a particularly useful tool for the evaluation of such reactions of the diamagnetic technetium(I) compounds in solution.
- Abram, Ulrich,Elsholz, Laura,Roca Jungfer, Maximilian
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p. 2980 - 2997
(2022/02/16)
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- High-Energy-Density Magnesium-Air Battery Based on Dual-Layer Gel Electrolyte
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Mg-air batteries are explored as the next-generation power systems for wearable and implantable electronics as they could work stably in neutral electrolytes and are also biocompatible. However, high corrosion rate and low utilization of Mg anode largely impair the performance of Mg-air battery with low discharge voltage, poor specific capacity and low energy density. Here, to the best of our knowledge, we first report a dual-layer gel electrolyte to simultaneously solve the above two problems by preventing the corrosion of Mg anode and the production of dense passive layer, respectively. The resulting Mg-air batteries produced an average specific capacity of 2190 mAh g?1 based on the total Mg anode (99.3 % utilization rate of Mg anode) and energy density of 2282 Wh kg?1 based on the total anode and air electrode, both of which are the highest among the reported Mg-air batteries. Besides, our Mg-air batteries could be made into a fiber shape, and they were flexible to work stably under various deformations such as bending and twisting.
- Chen, Hao,Gao, Rui,He, Er,Jiao, Yiding,Li, Luhe,Lu, Jiang,Peng, Huisheng,Wang, Jiacheng,Wang, Lie,Ye, Tingting,Zhang, Ye
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supporting information
p. 15317 - 15322
(2021/06/14)
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- Stretching the: C-axis of the Mn3O4lattice with broadened ion transfer channels for enhanced Na-ion storage
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Mn3O4 is a typical electrode material for supercapacitors with high theoretical energy density. However, the electrochemical performance of Mn3O4 is hindered by the sluggish charge transfer kinetics and poor cycling lifetimes. Herein, Mn3O4 with c-axis stretched lattice distortion (oxygen vacancy, Ov-Mn3O4) was prepared through a simple sulfurization/desulfurization treatment. The resultant Ov-Mn3O4 displays a high capacity of 331.1 F g-1 at 1 A g-1, a significant rate capability of 258.2 F g-1 at 20 A g-1, and a promising cycling stability with 83% capacity retention after 15?000 cycles. An asymmetric supercapacitor with Ov-Mn3O4 as the cathode delivers an energy density of 52.5 W h kg-1 at a power density of 1000 W kg-1. In situ Raman results demonstrate that Ov-Mn3O4 can effectively suppress and accommodate the cooperative Jahn-Teller distortion, contributing to a prolonged cycling life. DFT results suggest that the c-axis stretched lattice distortion induces electron delocalization, thus facilitating the electron transfer. Moreover, Na+ exhibits accelerated transfer kinetics in c-axis stretched lattice distorted Ov-Mn3O4 with broadened ion transfer channels. This work highlights the advantage of c-axis stretched lattice distortion for Na ion storage in Mn3O4, which can be expanded to optimize the electronic configuration of other metal oxides.
- Fu, Zhenzhen,Hu, Lingyuan,Li, Bingcan,Liu, Ruochen,Liu, Xia,Wang, Dewei,Wang, Shiyu,Yan, Yi-Ming,Yang, Ru,Yang, ZhiYu,Yao, Shuyun,Zhang, Anqi,Zhao, Rui
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supporting information
p. 23506 - 23514
(2021/11/04)
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- Study of reactions in the solid phase leading to the formation of SrSn0.9Mn0.1O3 perovskite oxide
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The perovskite solid solution described by the formula SrSn0.9Mn0.1O3 was obtained through a solid-state reaction. Thermal decomposition processes and the reaction route of the perovskite solid solution formation were studied using a thermal analysis method with help from X-ray diffraction analysis. The mechanochemical activation of initial reagents accelerates the reaction course and supports the formation of SrSnO3 and SrMnO3, which together form a solid solution at 1200 °C. The reaction process of nonactivated initial reagents SrCO3, SnO2, and MnO2, respectively MnCO3 leads to the formation of SrSn0.9Mn0.1O3 through the formation of the intermediate phases Sr7Mn4O15 and Sr2SnO4. The color hues of the samples go from light brown to dark brown as the calcining temperature rises.
- Hroch,Dohnalová,?ulcová
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- Interfacial effect of Pd supported on mesoporous oxide for catalytic furfural hydrogenation
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Highly dispersed Pd is loaded onto different types of mesoporous oxide supports to investigate the synergetic metal-support effect in catalytic furfural (FAL) hydrogenation. Ordered mesoporous Co3O4, MnO2, NiO, CeO2, and Fe2O3 are prepared by the nanocasting and the supported Pd on mesoporous oxide catalysts are obtained by the chemical reduction method. It is revealed that mesoporous oxides play an important role on Pd dispersion as well as the redox behavior of Pd, which determines the final FAL conversion. Among the catalysts used, Pd/Co3O4 shows the highest conversion in FAL hydrogenation and distinct product selectivity toward 2-methylfuran (MF). While FAL is converted via two distinct pathways to produce either furfuryl alcohol (FA) via aldehyde hydrogenation or MF via hydrogenolysis, MF as a secondary product is derived from FA via the hydrogenolysis of C–O over the Pd/Co3O4 catalyst. It is revealed that FAL is hydrogenated to FA preferentially on the Pd surface; then the secondary hydrogenolysis to MF from FA is further promoted at the interface between Pd and Co3O4. We confirm that the reaction pathway over Pd/Co3O4 is totally different from other catalysts such as Pd/MnO2, which produces FA dominantly. The characteristics of the mesoporous oxides influence the Pd-oxide interfaces, which determine the activity and selectivity in FAL hydrogenation.
- Lee, Hojeong,Nguyen-Huy, Chinh,Jeong Jang, Eun,Lee, Jihyeon,Yang, Euiseob,Lee, Man Sig,Kwak, Ja Hun,An, Kwangjin
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p. 291 - 300
(2020/03/05)
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- Effect of Manganese Valence on Specific Capacitance in Supercapacitors of Manganese Oxide Microspheres
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Manganese oxides have attracted great interest in electrochemical energy storage due to high theoretical specific capacitance and abundant valence states. The multiple valence states in the redox reactions are beneficial for enhancing the electrochemical properties. Herein, three manganese microspheres were prepared by a one-pot hydrothermal method and subsequent calcination at different temperatures using carbon spheres as templates. The trivalent manganese of Mn2O3 exhibited multiple redox transitions of Mn3+/Mn2+ and Mn4+/Mn3+ during the intercalation/deintercalation of electrolyte ions. The possible redox reactions of Mn2O3 were proposed based on the cyclic voltammetry and differential pulse voltammogram results. Mn2O3 microsphere integrated the advantages of multiple redox couples and unique structure, demonstrating a high specific capacitance and long cycling stability. The symmetric Mn2O3//Mn2O3 device yielded a maximum energy density of 29.3 Wh kg?1 at 250 W kg?1.
- Chen, Xing,Li, Lei,Wang, Xiaoli,Xie, Kun,Wang, Yuqiao
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p. 9152 - 9159
(2021/05/17)
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- New Mn(II), Co(II), Ni(II) and Cu(II) homoleptic complexes with 6-chloro-5-7-dimethyl-4oxo-4H-chromene-3-carbaldehydes and its heteroleptic complexes with quinoline-8 ol: synthesis, characterization and antimicrobial activity
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In the present study, the synthesis of ligand 6-chloro-5-7-dimethyl-4oxo-4H-chromene-3-carbaldehydes by three steps from the substituted phenol. The formed product in the first step was further processed by fries rearrangement reaction and subsequently Vilsmeier–Haack reaction. Then, its homoleptic and heteroleptic complexes with Mn(II), Co(II), Ni(II) and Cu(II) metal ions by using second ligand quinolin-8-ol were synthesized. The ligand and complexes were characterized by different techniques, such as electron dispersive spectroscopy and elemental analysis (CHN), Fourier transform infrared (FTIR), electronic spectroscopy and magnetic susceptibility, 1H-Nuclear magnetic resonance spectroscopy and mass spectra of ligand, electron spin resonance (ESR), thermogravimetric analysis, powder X-ray diffraction, scanning electron microscopy (SEM) and molar conductivity. The spectroscopic analysis like NMR and the FTIR shows that the both ligands are bidentate in nature. The UV–visible spectra show the homoleptic complex of Cu(II) shows square planer, while M = Ni(II), Co(II) and Mn(II) shows octahedral in nature. While the complexes with heteroleptic ligands from square planer geometry with Cu(II) and Ni(II) while Co(II) and Mn(II) show octahedral geometries. The geometry was also supported by magnetic susceptibility and FTIR spectra. The ESR spectra of Cu(II) complexes shows both are square planer geometry and the G-value was more than 4 indicating the absence of exchange interaction between Cu(II) metal ions in the solid state. The powder X-ray diffraction was used to determine the crystal system of all the complexes, while supporting to this X-ray diffraction the SEM was also taken for the nanostructure of complexes was developed or not. Then, the solution state conductivity of the complexes shows electrolytic in nature. Further, these complexes were evaluated for its antimicrobial activity by agar well diffusion method and structure–activity relationship. The ligands show antimicrobial activity against S.typhi. The Ni(II) does not show antibacterial activity, while complexes Cu(II), Co(II) and Mn(II) shows good activity against the gram-positive and the gram-negative bacteria. The heteroleptic ligand complex (6) of Cu(II) shows higher antifungal activity as compared with Ni(II), Co(II) and Mn(II) complexes.
- Kolhe, Nitin H.,Jadhav, Shridhar S.,Thube, Dilip R.,Takate, Sushma J.,Bankar, Ashok V.,Moharekar, Sanjay T.,Pawar, Hari R.,Moharekar, Shubhangi S.
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p. 459 - 481
(2020/10/13)
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- Enhancement of the OER Kinetics of the Less-Explored α-MnO2 via Nickel Doping Approaches in Alkaline Medium
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Development of a low-cost transition metal-based catalyst for water splitting is of prime importance for generating green hydrogen on an industrial scale. Recently, various transition metal-based oxides, hydroxides, sulfides, and other chalcogenide-based materials have been synthesized for developing a suitable anode material for the oxygen evolution reaction (OER). Among the various transition metal-based catalysts, their oxides have received much consideration for OER, especially in lower pH condition, and MnO2 is one of the oxides that have widely been used for the same. The large variation in the structural disorder of MnO2 and internal resistance at the electrode–electrolyte interfaces have limited its large-scale application. By considering the above limitations of MnO2, here in this work, we have designed Ni-doped MnO2 via a simple wet-chemical synthetic route, which has been successfully applied for OER application in 0.1 M KOH solution. Doping of various quantities of Ni into the MnO2 lattices improved the OER properties, and for achieving 10 mA/cm2 current density, the Ni-doped MnO2 containing 0.02 M of Ni2+ ions (coined as MnO2-Ni0.002(M)) demands only 445 mV overpotential, whereas the bare MnO2 required 610 mV overpotential. It has been proposed that the incorporation of nickel ions into the MnO2 lattices leads to an electron transfer from the Ni3+ ions to Mn4+, which in turn facilitates the Jahn–Teller distortion in the Mn–O octahedral unit. This electron transfer and the creation of a structural disorder in the Mn sites result in the improvization of the OER properties of the MnO2 materials.
- Bera, Krishnendu,Karmakar, Arun,Karthick, Kannimuthu,Kumaravel, Sangeetha,Kundu, Subrata,Madhu, Ragunath,Sankar, Selvasundarasekar Sam
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p. 19429 - 19439
(2021/12/09)
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- Hollow spherical 0.5Li2MnO3·0.5LiMn1/3Ni1/3Co1/3O2 prepared by facile molten salt method for enhanced long-cycle and rate capability of lithium-ion batteries
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Molten salt method has been widely adopted in preparation of a series of battery materials. The formula of the molten salts has a great influence on the morphology and property of the product. In this work, a hollow spherical lithium-rich cathode material (0.5Li2MnO3·0.5LiMn1/3Ni1/3Co1/3O2, LMO) was successfully prepared using a mixed molted salt method. The hollow LMO possesses a higher crystallinity and more Li+ diffusion channels in comparison with the LMO prepared using single salt or no salt, because the mixed salts have a much lower melting point. These structural features endow the hollow LMO with remarkably high initial discharge capacity (280.9 mAh g?1 at 0.1C) and coulombic efficiency, excellent rate performance as well as good cycling stability (500 cycles at 5C). Notably, the hollow LMO exhibits outstanding cycling stability at high temperature (60 °C at 1C over 100 cycles). Further kinetic analyses reveal that the Li+ diffusion coefficient is obviously enhanced, and the charge transfer resistance is reduced by the mixed molten salt method. This work proposes an effective strategy to improve the electrochemical performance of Li-rich cathode materials by regulating the formula of the molten salt method.
- Ding, Zhiyu,Li, Kaikai,Li, Leyuan,Liu, Xingjun,Liu, Yanchen,Sun, Ruiting,Wu, Junwei,Yu, Haobin,Yuan, Qunhui
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- Immobilizing ultrafine bimetallic PtAg alloy onto uniform MnO2 microsphere as a highly active catalyst for CO oxidation
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Herein, a facile glycol reduction route is successful employed to synthesize bimetallic PtAg alloys with homogeneous distribution of sizes and elements. Experimental studies reveal that the ultrafine PtAg alloys with well-defined sizes from around 3.3 nm to 5.8 nm are immobilized onto MnO2 microsphere, which remarkably enhances the catalytic performances for CO oxidation. Importantly, quasi in-situ X-ray photoelectron spectroscopy (XPS) result reveals that both Mn and Pt ions on the surface of catalysts would realize alternating reduction-oxidation by CO and O2 molecules, and the oxygen vacancy sites could be replenished and excited by gas-phase O2.
- Mo, Shengpeng,Peng, Peng,Pei, Yinchang,Shen, Taiming,Xie, Qinglin,Fu, Mingli,Chen, Yunfa,Ye, Daiqi
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supporting information
p. 2057 - 2060
(2021/03/15)
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- Exemption of lattice collapse in Ni-MnO2birnessite regulated by the structural water mobility
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Lattice collapse and associated mechanical fracture frequently occur in Li-intercalated metal oxide cathodes at the deep charge state upon Li-ion removal, governed by chemical compositions and the resulting electron density of the oxygen atoms. However, similar lattice collapse for metal oxide electrodes in aqueous storage and its mitigation have not been well studied. Herein, we reported the lattice collapse of MnO2 layered birnessite during the aqueous de-sodiation process at high voltage due to the structural water motion, as evidenced by in situ XRD. Unlike non-aqueous Li-intercalated electrodes, Ni-dopants mitigated the lattice collapse of birnessite at deep charge states. Moreover, density functional theory (DFT) calculations showed that Ni doping induces charge depletion of lattice oxygen due to its higher electronegativity than Mn. This charge reduction, in turn, yields a significant decrease in electrostatic repulsion between the oxygens belonging to lattice and structural water. Classical molecular dynamics simulations based on atomic charges obtained from DFT elucidate that Ni-doping facilitates immobilization of structural water in (Ni)MnO2 and prevents lattice collapse upon Na-ion removal. (Ni)MnO2 exempted from lattice collapse shows an improved storage capacity relative to MnO2 while maintaining similar cycling stability.
- Abeykoon, Milinda,Kim, SaeWon,Kwon, Gihan,Narayanan, Badri,Olds, Daniel,Pidathala, Ranga Teja,Shan, Xiaoqiang,Teng, Xiaowei,Xu, Wenqian
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supporting information
p. 23459 - 23466
(2021/11/04)
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- Challenges in the Application of Manganese Oxide Powders as OER Electrocatalysts: Synthesis, Characterization, Activity and Stability of Nine Different MnxOy Compounds
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Manganese oxides are seen as potential electrocatalysts for the alkaline oxygen evolution reaction (OER). To find the most suitable OER catalyst among the large number of known manganese oxide compounds, several comparative studies of selected MnxOy materials in water oxidation catalysis were reported in recent years with, in some cases, conflicting results. In this study, nine different manganese oxide powders differing in structure and/or composition were synthesized, characterized and compared regarding their OER activity and stability using a consistent set of experimental parameters. It turned out that the activity generally depends strongly on the manganese oxide compound. α-MnO2 manganese oxides of the hollandite-type were found to be more active than those with a lower oxidation state or other crystal structures. The most active catalyst cryptomelane, α-(K)MnO2, reached a current density of 10 mA/cm2 at 1.77±0.02 V in LSV measurements. At a potential of 1.8 V, the current density was approximately 15 mA cm?2. In contrast, the samples with the lowest activity exhibited values less than 1 mA cm?2 at the same potential. The stability experiments revealed a fast decrease in activity of all samples within the first minutes of measurement and an almost complete activity loss after 60 min. Conductivity differences are discussed as a likely reason for the observed differences in performance.
- Heese-G?rtlein, Justus,Rabe, Anna,Behrens, Malte
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p. 1363 - 1372
(2021/05/27)
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- Practical synthesis of ethyl 3-fluoro-1-pyrrole-2-carboxylate: A key fragment of a potent drug candidate against hepatitis b virus
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We report herein the development of two efficient synthetic routes for the preparation of a key fragment required for the synthesis of potent drug candidates of Hepatitis B virus. The ethyl 3-fluoro-1-H-pyrrole-2-carboxylate scaffold was synthesized from readily available starting materials in good overall yields. The scalability of one of the developed routes was demonstrated and afforded the desired target in good yield and excellent purity (99%).
- René, Adeline,Quilan, Maxime,Deng, Yicheng,Cheng, Yang,Teleha, Christopher A.,Raboisson, Pierre,Bonfanti, Jean-Fran?ois,Fortin, Jér?me,Charette, André. B.,Pannecoucke, Xavier,Poisson, Thomas,Jubault, Philippe
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p. 792 - 801
(2019/10/16)
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- A high-energy-density aqueous zinc-manganese battery with a La-Ca co-doped ?-MnO2cathode
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Aqueous zinc-manganese dioxide batteries (Zn//MnO2) are gaining considerable research attention for energy storage taking advantage of their low cost and high safety. However, the capacity and cycling stability of the state-of-the-art devices are still utterly disappointing because of the inevitable MnO2 dissolution and its low conductivity. In this work, to elevate the energy density of Zn//MnO2, a La-Ca co-doping strategy is proposed to boost the electrochemical performance of the ?-MnO2 cathode. Specifically, the introduction of heteroatoms, La3+ and Ca2+, is achieved via a facile one-step liquid coprecipitation method. Our experimental results reveal that Ca2+ significantly improves the stability of ?-MnO2 while Ca2+ and La3+ both contribute to the capacity and reversibility enhancement. Therefore, the overall performance of the La-Ca co-doped ?-MnO2 cathode exceeds the pristine sample, as demonstrated by its commendable capacity of 297.3 mA h g-1 at 0.2 A g-1, superior cycle stability (up to 76.8% capacity retention after 200 cycles) and excellent rate capability (161 mA h g-1 when the current density increased to 1.6 A g-1). Besides, the assembled Zn//?-MnO2 device delivers a maximum energy and power density of 401.22 W h kg-1 and 5.2 kW kg-1 respectively, outperforming most of the recently reported Zn//MnO2 counterparts. This journal is
- Liu, Jie,Liu, Xiaoqing,Lu, Xihong,Luo, Jiawei,Wu, Weixing,Yang, Yangyi,Zhang, Haozhe,Zhang, Manshu
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p. 11642 - 11648
(2020/07/02)
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- Layered Ca0.28MnO2·0.5H2O as a High Performance Cathode for Aqueous Zinc-Ion Battery
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Aqueous zinc-ion batteries are promising candidates for grid-scale energy storage because of their intrinsic safety, low cost, and high energy intensity. However, lack of suitable cathode materials with both excellent rate performance and cycling stability hinders further practical application of aqueous zinc-ion batteries. Here, a nanoflake-self-assembled nanorod structure of Ca0.28MnO2·0.5H2O as Zn-insertion cathode material is designed. The Ca0.28MnO2·0.5H2O exhibits a reversible capacity of 298 mAh g?1 at 175 mA g?1 and long-term cycling stability over 5000 cycles with no obvious capacity fading, which indicates that the per-insertion of Ca ions and water can significantly improve reversible insertion/extraction stability of Zn2+ in Mn-based layered type material. Further, its charge storage mechanism, especially hydrogen ions, is elucidated. A comprehensive study suggests that the intercalation of hydrogen ions in the first discharge plat is controled by both pH value and type of anion of electrolyte. Further, it can stabilize the Ca0.28MnO2·0.5H2O cathode and facilitate the following insertion of Zn2+ in 1 m ZnSO4/0.1 m MnSO4 electrolyte. This work can enlighten and promote the development of high-performance rechargeable aqueous zinc-ion batteries.
- Sun, Tianjiang,Nian, Qingshun,Zheng, Shibing,Shi, Jinqiang,Tao, Zhanliang
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- PROCESS OF PREPARATION OF 1,2-PENTANEDIOL FROM FURFURAL
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The present invention relates to hydrogenolysis process for preparation of 1,2-pentanediol from furfural. In particular, the present invention provides a conversion of 1,2-pentanediol from furfural in presence of methanol and using a catalyst based on Rhodium on porous Manganese dioxide octahedral molecular sieve in a single step carried out at temperature range between 130 °C to 170 °C. The advantages of present invention is that it avoids formation of Intermediate-2 and directly give product 1,2-pentanediol with good selectivity over 1,5-pentanediol.
- -
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Page/Page column 7-8
(2020/08/22)
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- TRI-CYCLE COMPOUND AND APPLICATIONS THEREOF
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Disclosed in the present invention are a compound represented by formula (I), a tautomer thereof or a pharmaceutically acceptable salt, and applications thereof in the preparation of drugs for treating HBV-related diseases.
- -
-
Paragraph 0156-0157; 0161; 0214-0216
(2020/01/22)
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- Silver doping in lanthanum manganite materials: structural and electrical properties
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Ag-doped LaMnO3 nanoparticles have been synthesized through sol–gel process using citric acid as a chelating agent. Silver effect on physicochemical properties was studied. The physicochemical properties and electrical performance of the obtained materials were also investigated, using thermogravimetric analysis (TGA) and X-ray diffraction (XRD)?techniques. Thermogravimetric analysis shows that for the studied materials a decomposition stage between 3.7% and 4.1% can be observed, and mass increases from the LMN-Ag1 to the LMN-Ag3 sample. Also, in all those three situations an endothermic process with a maximum around 600?°C is observed. The diffractograms of the perovskite materials showed single-phase crystalline with high purity and rhombohedral structure with R-3c space group. The electrical measurements show that the conductivity spectrum is formed by both the static component σDC corresponding to the low frequencies and the component σAC corresponding to high frequencies. The values of σDC of samples are significantly influenced by the silver ions concentration.
- Sfirloaga, Paula,Vlase, Gabriela,Vlase, Titus,Malaescu, Iosif,Marin, Catalin Nicolae,Vlazan, Paulina
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p. 1817 - 1823
(2020/08/05)
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- Insight into Ce Doping Induced Oxygen Vacancies over Ce-Doped Mno2 Catalysts for Imine Synthesis
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The pursuit of modern sustainable chemistry has stimulated the development of innovative catalytic processes that enable chemical transformations to be performed under mild and clean conditions with high efficiency. Here, an amorphous sheet-like MnO2 (Ce-doped MnO2: CMBO) was obtained after Ce doping, which exhibits excellent catalytic performance for the oxidation coupling of alcohol and aniline. Conversion of 99% and a selectivity of 99% could be achieved within 6 h at 60 oC under air atmosphere, and the formation rate of target product was up to 30.2 μmol·h–1·m–2. Based on a series of characterizations, it was found that the doping of Ce into the MnO2 could increase the concentration of the oxygen vacancies, thus forming abundant active surface oxygen species and favoring the mobility of lattice oxygen, which are the main reasons for the greatly enhanced catalytic performance of CMBO. This work indicates that increasing oxygen vacancy by element doping may serve as a facile and efficient way to enhance catalytic performance of transition metal oxide.
- Shen, Haidong,Bu, Jun,Wang, Wenbin,Wu, Chen,Cao, Yueling,Zhang, Baoliang,Zhang, Qiuyu,Zhang, Hepeng
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supporting information
p. 1353 - 1359
(2020/08/25)
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- Porous manganese-cobalt oxide microspheres with tunable oxidase mimicking activity for sulfide ion colorimetric detection
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Here, we report the controllable synthesis of porous MnxCo1-xO microspheres and tunable catalytic activity in the oxidase mimicking reaction. Mn0.6Co0.4O possesses the best oxidase mimicking activity and can be used successfully in sulfide ion colorimetric detection with a low detection limit of 0.1 μM. This journal is
- Wang, Xue,Feng, Shiya,He, Daiping,Jiang, Ping
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supporting information
p. 14098 - 14101
(2020/11/20)
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- Synthesis and research of MnO2–NiO composite as lithium-ion battery anode using spent Zn–Mn batteries as manganese source
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In this work, we have successfully synthesized porous flower-like MnO2–NiO anode material for lithium ion batteries by facile hydrothermal method using the manganese source that is recovered from spent Zn–Mn batteries through hydrometallurgy recycling technology. Scanning electron microscopy (SEM) reveals that such an architecture provides short paths for lithium diffusion and large material/electrolyte contact area. The electrochemical measurements exhibit that the initial discharge capacity of MnO2–NiO composite is 2981 mAh·g?1 at a current density of 100 mA g?1 and retains at 502 mAh·g?1 after 100 cycles, much higher than that of pure MnO2. Even at a high current rate of 400 mA g?1, the specific capacity still remains at 297 mAh·g?1 after 50 cycles. The electrode exhibits excellent cycling performances and high capacity. Furthermore, the lithiation and delithiation processes of MnO2–NiO anode material have been studied in detail by X-ray diffraction characterization. We found that during the lithiation process, MnO2 reacts with lithium ions to form the intermediate product of Mn2O3, which is further reduced to Mn metal. NiO directly reacts with lithium ions to form Ni metal.
- Guo, Guanghui,He, Bowen,Qiu, Jianghua,Wu, Jie,Zhang, Ningsheng,Zhu, Jiaxin
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- Anomalous Chromophore Disruption Enables an Eight-Step Synthesis and Stereochemical Reassignment of (+)-Marineosin A
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An eight-step asymmetric synthesis of (+)-marineosin A is described. The route proceeds by condensing fragments of reversed polarity relative to conventional prodiginine constructions. The resultant unstable chromophore is disrupted by a unique cycloisomerization promoted at a tailored manganese surface. This provides a premarineosin and subsequently marineosin A in a particularly concise manner. A pyridinophane N-oxide photorearrangement in flow and structural isomers of premarineosin are discussed, as is the reassignment of marineosin stereochemistry. The route gives access to the natural product as well as diastereomers, congeners and analogs that are currently inaccessible by other means.
- Feng, Zhengao,Allred, Tyler K.,Hurlow, Evan E.,Harran, Patrick G.
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supporting information
(2019/02/14)
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- Boosting the Zn-ion storage capability of birnessite manganese oxide nanoflorets by La3+ intercalation
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To develop aqueous rechargeable Zn-ion batteries (ZIBs) with high capacity and good rate capability, the focus is on cathode improvement. Herein, birnessite δ-MnO2 nanoflorets with La3+ intercalation (LMO) were reported as high-energy and high-rate cathodes for ZIBs. The intercalation of La3+ within the δ-MnO2 nanoflorets was readily achieved by a simple, scalable and effective precipitation process. Benefiting from the larger interlamellar spacing, reduced Zn2+ (de)insertion resistance and increased surface area after La3+ intercalation, the Zn-ion storage capability of the δ-MnO2 nanoflorets was significantly boosted, resulting in high reversible capacity of 278.5 mA h g-1 at 100 mA g-1 and superb rate capability of 121.8 mA h g-1 at 16-fold higher current density (only 3.4 mA h g-1 for pristine δ-MnO2 nanoflorets) as well as good durability. Moreover, the maximum energy and power densities of the as-obtained Zn//LMO battery reached 375.9 W h kg-1 and 4.8 kW kg-1 (based on the cathode mass), respectively. Considering the new design of La3+ intercalation, this study hopes to provide an insightful guide for exploring next-generation Mn-based cathode materials for ZIBs.
- Zhang, Haozhe,Liu, Qiyu,Wang, Jing,Chen, Kunfeng,Xue, Dongfeng,Liu, Jie,Lu, Xihong
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p. 22079 - 22083
(2019/10/14)
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- Origins of boron catalysis in peroxymonosulfate activation and advanced oxidation
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Metal-free materials have exhibited great merits as substitutes for toxic and scarce metals/oxides in environmental catalysis. In this work, amorphous boron (A-Boron) is exploited as a nonmetal catalyst for peroxide activation. It is discovered that A-Boron is exclusively reactive for peroxymonosulfate (PMS) activation for the degradation of a diversity of organic contaminants in water, including benzenes, phenolics, dyes and antibiotics. Moreover, comparative tests show that A-Boron stands out among diverse heterogeneous catalysts, such as transition metal oxides, nanocarbons and non-carbonaceous materials (sulfur, phosphorus, boron nitride, and boron carbide). Competitive radical scavenging tests and in situ radical capture analysis by electron paramagnetic resonance (EPR) revealed that both sulfate (minor contribution) and hydroxyl radicals (dominant contribution) are generated and account for the organic oxidation. Advanced characterisation techniques suggest that the boron-based catalysis stems from the short-range ordered grain boundaries and amorphous domains in A-Boron. This is further evidenced by the fact that after thermal treatment, the surface-tailored boron samples (A-B-400 to 1000) exhibit inferior activities, with 10.4% to 28.3% phenol removal compared with A-Boron (74.3%); this is due to the formation of surface boric acid/hydroxide, which blocks the active boron phases. Theoretical calculations illustrate that the (1 0 0), (1 0 1) and (1 1 0) terminations and amorphous regions of elemental boron can directly cleave the peroxide O-O bond and decompose PMS to produce reactive hydroxyl radicals, which is in agreement with the experimental discoveries. This study provides a novel metal-free catalytic system for wastewater treatment and provides the first mechanistic insights into the origins of boron-based catalysis.
- Duan, Xiaoguang,Li, Wenlang,Ao, Zhimin,Kang, Jian,Tian, Wenjie,Zhang, Huayang,Ho, Shih-Hsin,Sun, Hongqi,Wang, Shaobin
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supporting information
p. 23904 - 23913
(2019/11/05)
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- Hollow microspherical layered xLi2MnO3·(1-x)LiNiO2 (x=0.3–0.7) as cathode material for lithium–ion batteries
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Li-rich layered Li2MnO3 is of great attraction for high energy lithium ion batteries. However, its cycling is still needed for improvements. Here we report a hollow microsphere-structured xLi2MnO3·(1-x)LiNiO2 (x = 0.3–0.7) that is synthesized by using in-situ template-sacrificial strategy. Powder X-ray diffraction (XRD) and scanning electron microscope (SEM) characterizations prove that the xLi2MnO3·(1-x)LiNiO2 (x = 0.3–0.7) are based on monoclinic Li2MnO3 with α-NaFeO2 layered structure in which Li+ ions are orderly arranged in the transition metal layers, and the hollow-microspheres have diameters of ～3 μm. Electrochemical results show that the optimal ratio of Li2MnO3/LiNiO2 is 0.6/0.4. As a consequence, the stabilized discharge capacity of 0.6Li2MnO3·0.4LiNiO2 (0.6LLMNO) is ～210 mAh g?1 after the first few cycles. This shows that appropriate amount Ni substitution for Mn in Li2MnO3 helps to improve the specific capacity and cycling stability.
- Zhang, Kai,Zhang, Lei,Liu, Junjie,Wu, Xiongwei,Zhou, Chunjiao,Yan, Wenqi,Zhou, Congshan,Fu, Lijun,Wu, Yuping
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p. 1034 - 1042
(2019/03/28)
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- One-for-All strategy to design oxygen-deficient triple-shelled MnO2 and hollow Fe2O3 microcubes for high energy density asymmetric supercapacitors
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Intrinsically poor conductivity, sluggish ion transfer kinetics, and limited specific area are the three main obstacles that confine the electrochemical performance of metal oxides in supercapacitors. Engineered hollow metal oxide nanostructures can effectively satisfy the increasing power demand of modern electronics. In this work, both triple-shelled MnO2 and hollow Fe2O3 microcubes have been synthesized from a single MnCO3 template. The oxygen vacancies are introduced in both the positive and negative electrodes through a facile method. The oxygen vacancies can not only improve the conductivity and facilitate ion diffusion but also increase the electrode/electrolyte interfaces and electrochemically active sites. Consequently, both the oxygen-deficient triple-shelled MnO2 and hollow Fe2O3 exhibit larger capacitance and rate capability than the samples without oxygen vacancies. Moreover, due to the matchable specific capacitance and potential window between the positive and negative electrodes, the asymmetric supercapacitor exhibits high specific capacitance (240 F g-1), excellent energy density of 133 W h kg-1 at 1176 W kg-1, excellent power density (23529 W kg-1 at 73 W h kg-1), and high cycling stability (90.9% after 5000 cycles). This strategy is highly reproducible in oxide-based electrodes, which have the potential to meet the requirements of practical application.
- Jia, Henan,Liang, Haoyan,Wang, Zhaoyue,Li, Chun,Zheng, Xiaohang,Cai, Yifei,Qi, Junlei,Cao, Jian,Feng, Jicai,Fei, Weidong
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supporting information
p. 8623 - 8632
(2019/06/24)
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- Synthesis, characterization and biological activity of mixed ligands complexes of quinolin-8-ol and substituted chromones with Mn(II), Co(II), Ni(II) and Cu(II) metal ions
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The mixed ligand complexes were synthesized using quinolin-8-ol and substituted chromone derivative with transition metals like Mn(II), Cu(II), Ni(II) and Co(II). These complexes were characterized using elemental analysis by electron dispersive spectroscopy, Fourier transforms infrared, ultraviolet–visible, proton nuclear magnetic resonance, liquid chromatography coupled with mass spectrometry, electron spin resonance spectra, magnetic susceptibility, powder X-ray diffraction, thermogravimetric analysis and scanning electron microscopy. The complexes were screened by biological activities such as antioxidant activity by 2, 2-Diphenyl-1-picrylhydrazyl, antimicrobial activity by the agar well-diffusion method and anticancer activity by yellow tetrazolium (3-(4, 5-dimethylthiazolyl-2)-2,5-diphenyltetrazolium bromide methods. The synthesis of mixed ligand complexes were synthesized by using homoleptic complexes of respective metal complexes of chromones. The FTIR spectra show νM–O the νM–N frequencies are obtained at 515–645?cm?1 and 431–496?cm? 1 respectively. The NMR spectra of Ni(II) complexes were indicating the complexes are paramagnetic in nature. The ESR spectra of copper complexes shows singlet signal, and they indicate that the copper has 2 + oxidation state in complexes. The complexes showed a well-defined crystal system indicated by powder-X-ray diffraction patterns. The thermogram studies show formation of metal oxides residues at the end product of decomposition of complexes. The scanning electron microscope showed complexes were nanocrystalline in nature. The mixed ligand complex of Ni(II) shows 80.73% antioxidant activity as compared to both the ligands and other metal complexes. The antibacterial activity result obtained clearly showed that all complexes were effective against all the microorganisms of Staphylococcus aures, Bacillus subtilis, Escherichia coli and Pseudomonas aeruginos. The inhibition of the cancerous cell is more the case of Ni (II) complexes as compared with other complexes.
- Kolhe, Nitin H.,Jadhav, Shridhar S.
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p. 973 - 996
(2018/11/23)
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- Biodiesel production via esterification of oleic acid catalyzed by MnO2@Mn(btc) as a novel and heterogeneous catalyst
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The main objective of this study is to develop efficient and environmentally benign heterogeneous catalysts for biodiesel production. For this purpose, a heterogeneous MnO2@Mn(btc) catalyst was prepared by the solvothermal method, and the prepared catalyst was tested for the esterification of oleic acid. Various techniques such as X-ray diffraction, scanning and transmission electron microscopy, Brunauer–Emmett–Teller (BET) method, infrared spectroscopy, thermogravimetry, and NH3-TPD (temperature programmed desorption) analysis were employed for the characterization of the solid catalyst. The solid catalyst with MnO2@Mn(btc) loading of 15% showed high catalytic activity and long durability in the esterification of oleic acid, in which the fatty acid methyl ester yield reached 98% consecutively for at least five cycles under mild conditions.
- Amouhadi, Elham,Fazaeli, Razieh,Aliyan, Hamid
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p. 608 - 613
(2019/01/19)
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- Reasonably retard O2 consumption through a photoactivity conversion nanocomposite for oxygenated photodynamic therapy
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Photodynamic therapy (PDT) brings excellent treatment outcome while also causing poor tumor microenvironment and prognosis due to the uncontrolled oxygen consumption. To solve this issue, a novel PDT strategy, oxygenated PDT (maintain the tumor oxygenation before and after PDT) was carried out by a tumor and apoptosis responsive photoactivity conversion nanocomposite (MPPa-DP). Under physiological conditions, this nanocomposite has a low photoactivity. While at H2O2-rich tumor microenvironment, the nanocomposite could react with overexpressed H2O2 to produce O2 and release high photoactivity chimeric peptide PPa-DP for oxygenated tumor and PDT. Importantly, when the PDT mediates cell apoptosis, the photoactivity of PPa-DP be effectively quenched and the O2 consumption appeared retard, which avoided further consumption of residual O2 on apoptotic cells. In vitro and vivo studies revealed that this nanocomposite could efficiently change photoactivity, reasonable control O2 consumption and increase residual O2 content of tumor after PDT.
- Zhang, Jin,Xu, Mengqing,Mu, Yongli,Li, Jinjie,Foda, Mohamed F.,Zhang, Weiyun,Han, Kai,Han, Heyou
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- Polyoxometalates as bifunctional templates: Engineering metal oxides with mesopores and reactive surfaces for catalysis
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Mesoporous metal oxides with optimized porosity and active surfaces usually exhibit unexpected performance in many applications. However, sacrificial templates and complicated processes are generally required to generate mesopores. Herein, we discover the bifunctional templating talent of polyoxometalates (POMs) for generating not only mesopores but also reactive surfaces in metal oxides, and a facile, recyclable, and general method is reported. By mechanochemical ion-sharing between metal salts and POMs, metal precursors undergo pyrolysis around large POM clusters, which can incorporate abundant mesopores into metal oxides (e.g., Co3O4, Fe3O4, NiO, La2O3, MnO2, CeO2, ZrO2, and CuO) with ultrahigh specific surface areas (up to 210 m2 g-1) after simply being recycled by water washing. Unexpectedly, the oxidative feature of POMs naturally contributes to the formation of high valence metal cations on the material surface. As an example, the Co3O4 sample with both mesopores and enriched surface Co3+ species was more active than Co3O4 derived from a silica template (T100 = 200 °C) and commercial Co3O4 (T100 = 250 °C), in CO oxidation. The current strategy may provide a promising route for the commercialization of mesoporous metal oxides with preferred surface features.
- Leng, Yan,Liu, Jixing,Zhang, Zihao,Chen, Hao,Zhang, Pengfei,Dai, Sheng
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p. 27297 - 27303
(2019/12/25)
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- MnO2 and biomass-derived 3D porous carbon composites electrodes for high performance supercapacitor applications
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MnO2/biomass-derived porous carbon (BPC) composites have been prepared by a hydrothermal method, in which the BPC 3D porous carbon structure was based on a banana peel. The banana peel, after freeze drying, can maintain its hierarchical natural porous structure, which provides enough growth space for MnO2 and reduces the agglomeration of MnO2 particles. The MnO2/BPC composites were characterized by XRD, FT-IR, XPS, TGA, SEM, TEM, BET. The electrochemical performance of the composites was tested in three-electrode supercapacitors using 1 M Na2SO4 aqueous solution as an electrolyte. Due to the large amounts of hierarchical pores and large pore volume, the as-prepared composites exhibited good electrochemical performance. Electrochemical measurements indicated that the MnO2/BPC composites applied in supercapacitors had a specific capacitance of 139.6 F g?1 at 300 mA g?1, and exhibited a good cycling stability with a capacitance retention ratio of 92.3% after 1000 cycles (at 1 A g?1). The MnO2/BPC composites with 3D porous structure are promising materials in the application of supercapacitors.
- Yang, Guijun,Park, Soo-Jin
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p. 360 - 367
(2018/02/06)
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- High performance composites of spinel LiMn2O4/3DG for lithium ion batteries
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A highly crystalline nanosized spinel LiMn2O4/3DG composite cathode material for high rate lithium ion batteries was successfully prepared by mixing spinel LiMn2O4 particles with reduced graphene oxide (3DG). Spinel LiMn2O4 and reduced three-dimensional graphene oxide were synthesized using a hydrothermal method and freeze-drying technology, respectively. The structure, morphology and electrochemical performance of the synthesized materials were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS) and galvanostatic charge-discharge techniques. The results showed that the LiMn2O4/3DG composites exhibited excellent rate capability and stable cycling performance. The discharge capacity was 131 mA h g-1 and the capacity remains at 89.3% after 100 cycles at a 0.5 C rate, while the discharge capacity was 90 mA h g-1 at 10 C. Compared with spinel LiMn2O4 materials, the LiMn2O4/3DG composites showed obvious improvement in electrochemical performance.
- Luo,Yin,Yuan,Zeng,Lin,Huang,Li,Xiao
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p. 877 - 884
(2018/01/17)
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- Activating Inert Alkali-Metal Ions by Electron Transfer from Manganese Oxide for Formaldehyde Abatement
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Alkali-metal ions often act as promoters rather than active components due to their stable outermost electronic configurations and their inert properties in heterogeneous catalysis. Herein, inert alkali-metal ions, such as K+ and Rb+, are activated by electron transfer from a Hollandite-type manganese oxide (HMO) support for HCHO oxidation. Results from synchrotron X-ray diffraction, absorption, and photoelectron spectroscopies demonstrate that the electronic density of states of single alkali-metal adatoms is much higher than that of K+ or Rb+, because electrons transfer from manganese to the alkali-metal adatoms through bridging lattice oxygen atoms. Electron transfer originates from the interactions of alkali metal d–sp frontier orbitals with lattice oxygen sp3 orbitals occupied by lone-pair electrons. Reaction kinetics data of HCHO oxidation reveal that the high electronic density of states of single alkali-metal adatoms is favorable for the activation of molecular oxygen. Mn L3-edge and O K-edge soft-X-ray absorption spectra demonstrate that lattice oxygen partially gains electrons from the Mn eg orbitals, which leads to the upshift in energy of lattice oxygen orbitals. Therefore, the facile activation of molecular oxygen by the electron-abundant alkali-metal adatoms and active lattice oxygen are responsible for the high catalytic activity in complete oxidation of HCHO. This work could assist the design of efficient and cheap catalysts by tuning the electronic states of active components.
- Gao, Jiayi,Huang, Zhiwei,Chen, Yaxin,Wan, Jing,Gu, Xiao,Ma, Zhen,Chen, Jianmin,Tang, Xingfu
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p. 681 - 689
(2017/12/26)
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- Mn Self-Doping of Orthorhombic RMnO3 Perovskites: (R0.667Mn0.333)MnO3 with R = Er-Lu
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Orthorhombic rare-earth trivalent manganites RMnO3 (R = Er-Lu) were self-doped with Mn to form (R0.667Mn0.333)MnO3 compositions, which were synthesized by a high-pressure, high-temperature method at 6 GPa and ab
- Zhang, Lei,Gerlach, Dominic,D?nni, Andreas,Chikyow, Toyohiro,Katsuya, Yoshio,Tanaka, Masahiko,Ueda, Shigenori,Yamaura, Kazunari,Belik, Alexei A.
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p. 2773 - 2781
(2018/03/13)
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- High capacitance LiMn2O4 microspheres with different microstructures as cathode material for aqueous asymmetric supercapacitors
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Asymmetric supercapacitors (ASCS) with a battery-type electrode and a capacitor-type electrode have been regarded as the most promising energy-storage devices with high-energy and high-power densities. In this paper, the porous and hollow LiMn2O4 microspheres were prepared using MnCO3 microspheres as template and subsequently an ASCS with the as-prepared LiMn2O4 as cathode and activated carbon (AC) as anode in Li2SO4 aqueous electrolyte (designated by AC//LiMn2O4 ASCS) was assembled and investigated electrochemically. The results indicate that the porous LiMn2O4 exhibits a higher reversible capacity and rate capability compared to hollow LiMn2O4 microspheres, and delivers a specific capacitance of 536 F g?1 at 1 mV s?1. The assembled AC//porous LiMn2O4 ASCS presents a high energy density of 33.12 Wh kg?1 at the power density of 90 W kg?1. All these might be attributed to the unique microstructure of the as-prepared porous LiMn2O4 microspheres.
- Xiao, Haowen,Wang, Yourong,Xie, Kai,Cheng, Siqing,Cheng, Xianzhong
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- Synthesis of hollow peanut-like hierarchical mesoporous LiNi1/3Co1/3Mn1/3O2 cathode materials with exceptional cycle performance for lithium-ion batteries by a simple self-template solid-state method
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Despite being one of the most promising cathode materials for lithium-ion batteries, LiNi1/3Co1/3Mn1/3O2 has been plagued by its low electronic conductivity and Li+/Ni2+ cation mixing, which lead to poor rate capacity and cycle stability. In this paper, hollow peanut-like hierarchical mesoporous LiNi1/3Co1/3Mn1/3O2 has been synthesized by a simple self-template solid-state method, and the influence of calcination times on the electrochemical performances was also investigated. The results suggest that L2 sample calcined at 850 °C for 10 h shows the highest rate capability and superior cycle stability as compared to L1 sample calcined for 8 h and L3 sample calcined for 12 h. The initial discharge capacity of L2 is 155.1 mAh g?1, and maintains 107.8 mAh g?1 after 500 cycles at 1 C. Surprisingly, its initial discharge capacity is 144.7 mAh g?1 even when cycled at 10 C, and still retains 97 mAh g?1 after 300 cycles. The significant performance improvement of L2 is ascribed to the hollow peanut-like hierarchical mesoporous structure, which can not only buffer the volume changes during the repeated charge/discharge processes, but also shorten the ion transport distance.
- Fang, Yingchun,Huang, Yudai,Tong, Wei,Cai, Yanjun,Wang, Xingchao,Guo, Yong,Jia, Dianzeng,Zong, Jun
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p. 707 - 715
(2018/02/14)
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- Ethyl and butyl acetate oxidation over manganese oxides
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Mangenese oxides were synthesized using two new methods, a novel solvent-free reaction and a reflux technique, that produced cryptomelane-type products (K-OMS-2). Oxides were also synthesized using conventional methods and all specimens were applied to the oxidation of ethyl acetate and butyl acetate, acting as models for the volatile organic compounds found in industrial emissions. The catalysts were also characterized using N2 adsorption, X-ray diffraction, scanning electron microscopy, temperature programmed reduction and X-ray photoelectron spectroscopy. Each of the manganese oxides was found to be very active during the oxidation of both esters to CO2, and the synthesis methodology evidently had a significant impact on catalytic performance. The K-OMS-2 nanorods synthesized by the solvent-free method showed higher activity than K-OMS-2 materials prepared by the reflux technique, and samples with cryptomelane were more active than those prepared by the conventional methods. The catalyst with the highest performance also exhibited good stability and allowed 90% conversion of ethyl and butyl acetate to CO2 at 213 and 202 °C, respectively. Significant differences in the catalyst performance were observed, clearly indicating that K-OMS-2 nanorods prepared by the solvent-free reaction were better catalysts for the selected VOC oxidations than the mixtures of manganese oxides traditionally obtained with conventional synthesis methods. The superior performance of the K-OMS-2 catalysts might be related to the increased average oxidation state of the manganese in these structures. Significant correlations between the catalytic performance and the surface chemical properties were also identified, highlighting the K-OMS-2 properties associated with the enhanced catalytic performance of the materials.
- Soares, Olívia Salomé G.P.,Rocha, Raquel P.,órf?o, José J.M.,Pereira, Manuel F.R.,Figueiredo, José L.
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- Effect of Ethanedioic Acid Additives on the Dissolution of Manganese Oxides in Sulfuric Acid Solution
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The effect of ethanedioic acid additives on the rate of manganese(IV) oxide dissolution in sulfuric acid solutions was studied by kinetic and electrochemical methods. Interaction modes were established, and some details of the studied process mechanism we
- Godunov,Izotov,Gorichev
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p. 314 - 318
(2018/04/12)
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- Cultivating crystal lattice distortion in IrO2: Via coupling with MnO2 to boost the oxygen evolution reaction with high intrinsic activity
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Here, we report an effective strategy to lower Ir consumption and boost the OER performance in acid by loading IrO2 onto MnO2, in which the IrO2 crystals are well dispersed and undergo a so-called z-extension Jahn-Teller distortion in the octahedral structure. Compared with IrO2, the mass activity and intrinsic activity for IrO2/MnO2 were largely increased.
- Zhou, Zhenhua,Zaman, Waqas Qamar,Sun, Wei,Cao, Li-Mei,Tariq, Muhammad,Yang, Ji
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supporting information
p. 4959 - 4962
(2018/05/23)
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- Direct Molten Polymerization Synthesis of Highly Active Samarium Manganese Perovskites with Different Morphologies for VOC Removal
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A morphology-controlled molten polymerization route was developed to synthesize SmMnO3 (SMO) perovskite catalysts with netlike (SMO-N), granular-like (SMO-G), and bulk (SMO-B) structures. The SMO perovskites were formed directly by a molten polymerization method, and their morphologies were controlled by using the derivative polymers as templates. Among all catalysts, the porous SMO-N exhibited the highest activity, over which the toluene, benzene, and o-xylene were completely oxidized to CO2 at 240, 270, and 300 °C, respectively, which was comparable to that of typical noble-metal catalysts. The apparent activation energies of toluene over SMO-N (56.4 kJ·mol-1) was much lower than that of SMO-G (70.8 kJ·mol-1) and SMO-B (90.1 kJ·mol-1). Based on the results of scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy, and H2 temperature-programmed reduction characterization, we deduce that the excellent removal efficiency of volatile organic compounds (VOCs) over SMO-N catalyst was attributable to the special structure, high surface Mn4+/Mn3+ and Olatt/Oads molar ratios, and strong reducibility. Due to the high activity, low cost, and simple preparation strategy, the SMO catalyst is a promising catalyst for VOC removal.
- Liu, Lizhong,Zhang, Hongbo,Jia, Jinping,Sun, Tonghua,Sun, Mengmeng
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p. 8451 - 8457
(2018/07/25)
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- Application of Mesoporous Metal Oxide Immobilized Gold–Palladium Nanoalloys as Catalysts for Ethanol Oxidation
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Gold–palladium nanoalloys (AuPd) were synthesized by a dendrimer templating method and the as-prepared nanoalloys were immobilized on several reducible mesoporous metal oxides (MMOs). The MMOs of MnO2, Co3O4 and CeO2 exhibited low catalytic activity in gas-phase oxidation of ethanol. Upon immobilization of the AuPd nanoalloys the activity increased significantly, with high acetaldehyde selectivity at 120?°C. However, this activity increase from pure MMOs to AuPd/MMOs was accompanied by decrease in selectivity to acetaldehyde. One other interesting observation lies on the amount of gold in the nanoalloy. Increasing the ratio of Au:Pd in the nanoalloy from 1:1 to 10:1 lowered the activity by a factor of six but had a positive effect on selectivity. From this, we postulate dissociation absorption of molecular oxygen to the reactive oxides occurs more effectively on the Pd metal surface. With higher Au loading, the acetaldehyde selectivity remained above 90% even at higher reaction temperatures of 160?°C. This led to a postulation of quick desorption of acetaldehyde from the Au surface more than it does on the Pd surface. Graphical Abstract: [Figure not available: see fulltext.].
- Bingwa, Ndzondelelo,Antonels, Nathan C.,Williams, Marc B.,Haumann, Marco,Meijboom, Reinout
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p. 2957 - 2966
(2018/08/21)
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- Self-assembled hierarchical porous NiMn2O4 microspheres as high performance Li-ion battery anodes
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Hierarchical structured porous NiMn2O4 microspheres assembled with nanorods are synthesized through a simple hydrothermal method followed by calcination in air. As anode materials for lithium ion batteries (LIBs), the NiMn2O4 microspheres exhibit a high specific capacity. The initial discharge capacity is 1126 mA h g-1. After 1000 cycles, the NiMn2O4 demonstrates a reversible capacity of 900 mA h g-1 at a current density of 500 mA g-1. In particular, the porous NiMn2O4 microspheres still could deliver a remarkable discharge capacity of 490 mA h g-1 even at a high current density of 2 A g-1, indicating their potential application in Li-ion batteries. This excellent electrochemical performance is ascribed to the unique hierarchical porous structure which can provide sufficient contact for the transfer of Li+ ion and area for the volume change of the electrolyte leading to enhanced Li+ mobility.
- Zhao, Shuang,Li, Honglei,Jian, Zhixu,Xing, Yalan,Zhang, Shichao
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p. 41749 - 41755
(2019/01/03)
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- On the Origin of the Enhanced Performance of Pt/Dendrite-like Mn3O4 for Methanol Electrooxidation
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The interaction between precious metal nanoparticles and the support plays an important role in improving poisoning tolerance of Pt-based catalysts and thus maintaining their activity and stability. Here, a dendrite-like Mn3O4 was fabricated and used as a support for Pt nanoparticles towards the methanol electrooxidation reaction. The nanoparticles were deposited chemically on surfaces of the dendritic Mn3O4, which was prepared through calcination of MnO2 hollow microspheres. The Mn3O4 support not only provided an appropriate base for the formation of nanosized and homogeneous platinum particles (about 2.6 nm in size), but also increased Pt0 binding energy owing to a strong electronic interaction. By combining the advantages of the small-size, fine dispersion and enhanced binding energy of Pt nanoparticles, the Pt/Mn3O4 composite exhibited enhanced catalytic activity, poisoning tolerance and stability for methanol electrooxidation.
- Chi, Hong Zhong,Wu, Yongqiang,Xiong, Qinqin,Zhang, Chunxiao,Qin, Haiying
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p. 3546 - 3553
(2018/09/09)
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- Catalyst-free microwave-promoted one pot synthesis of 2-aryl benzoxazoles using MnO2 nanoparticles as a convenient oxidant under mild condition
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Abstract: An efficient and facile protocol for one pot synthesis of a series of 2-aryl benzoxazoles through coupling of o-aminophenol with aromatic aldehydes under microwave irradiation in the presence of MnO2 nanoparticles as oxidant reagent was demonstrated. The MnO2 nanoparticles were prepared via a solid-state chemical reaction technique. The structure of oxidant was assigned by Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), and scanning electron microscopy (SEM). The target molecules were obtained in good to high yields, high purity and short reaction times. The pure products were identified and characterized by physical and spectral data such as; melting point, IR, 1H NMR and 13C NMR. Graphical Abstract: An efficient and facil protocol for one pot synthesis of a series of 2-aryl benzoxazoles through coupling of o-aminophenol with aromatic aldehydes under microwave irradiation in the precense of MnO2 nanoparticles as oxidant reagent was demonstrated.
- Naeimi, Hossein,Rouzegar, Zahra,Rahmatinejad, Soraya
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p. 4745 - 4758
(2017/07/22)
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- Improved synthetic method of 2-amino-9-fluorenone
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The invention discloses an improved synthetic method of 2-amino-9-fluorenone. The improved synthetic method comprises the following steps: (1) adding dimethyl sulfoxide which is used as a solvent and 2-amino fluorine which is used as a solute into a reactor under an alkaline condition, and adding an oxidizing agent; (2) stirring for 1 hour to 5 days under a room temperature; (3) fractionally filtering, thus obtaining a brown solid 2-amino-9-fluorenone product. According to the improved synthetic method disclosed by the invention, the technical scheme is simple and economic, raw materials are easy to obtain, the preparation time is short, the yield is up to 98 percent, the content of byproducts is smaller than or equal to 2 percent, the improved synthetic method is particularly suitable for a pilot scale test and a large scale production of the 2-amino-9-fluorenone, and a good industrial application prospect is obtained.
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Paragraph 0029; 0030
(2017/10/07)
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- Porous waxberry-like MnO2/La2O3 microspheres for high performance asymmetric supercapacitor
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In this paper, porous waxberry-like microspheres structures of MnO2/La2O3 (Mn-La) composites were synthesized via a facile two-pot hydrothermal method. The microstructure and chemical composition of as-prepared Mn-La composites were characterized by a series of techniques such as XRD, SEM, TEM, HRTEM, XPS and BET. The results show that the pure MnO2 microspheres were covered with its large amount of well-ordered nanorods, and La2O3 was distributed evenly on MnO2 surface to constitute Mn-La composites. Meanwhile, the electrochemical tests reveal that sample Mn-La10 (molar ratio nMnO2:nLa2O3?=?1:0.1) exhibited the highest specific capacitance (Cm) (245.4?F?g?1 at a current density of 0.3?A?g?1, 1.5 times of MnO2), good rate performance and excellent cycling stability (97.5% capacitance retention after 3000 cycles at current density of 2.0?A?g?1). In general, suitable amount of La2O3 doping, based on the synergistic effect between MnO2 and La2O3, is helpful to improve the capacitance performance of composites. Furthermore, an asymmetric supercapacitor (Mn-La10//AC), with Mn-La10 as the positive electrode and activated carbons as the negative electrode, displays high energy density of 25.8 Wh kg?1 with a maximum power density of 0.3?kW?kg?1 under potential window of 2.0?V.
- Li, Yu,Guan, Bing,Maclennan, Aimee,Hu, Yongfeng,Li, Dandan,Zhao, Jing,Wang, Yaqiong,Zhang, Huaihao
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p. 395 - 405
(2017/05/12)
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