- Solid state synthesis of binary metal chalcogenides
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Solid state reaction of metal halides MXn (n = 1 or 2) with stoichiometric amounts of sodium chalcogenide (Na2S2 or Na2E where E = S, Se or Te) at 300 °C for 48 h in evacuated ampoules affords a range of transition and main-group metal chalcogenides: ME2 (M = Fe or Co, E = S or Te); M(1-x)E (M = Fe or Co, E = S); Ag2E (E = S, Se or Te), Ni(1-xE (E = S, Se or Te); NiS2, MnS, FeSe, SnSe and SnTe along with co-formed salt. Washing of the highly sintered, fused product mixture with water resulted in isolation of crystalline binary chalcogenides, typically of a single phase in good yield (90%). The products were characterised by X-ray powder diffraction, scanning electron microscopy (SEM), energy dispersive X-ray analysis (EDXA) and infrared spectroscopy.
- Shaw, Graham A.,Morrison, Daniel E.,Parkin, Ivan P.
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- The preparation and phase transformation of nanocrystalline cobalt sulfides via a toluene thermal process
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Nanocrystalline cobalt sulfides were prepared by the reactions between cobalt chlorides and sodium polysulfide via a toluene thermal process in the temperature range 120-170°C. Two single phases of Co9S8 and CoS2 were obtained. TEM microphotos showed that the Co9S8 and CoS2 particles were both spherical in shape with sizes of about 20 nm. Chemical analysis gave the formulas Co9S7.93 and CoS1.97, respectively. The transformations among cobalt sulfides (Co9S8, Co3S4, and CoS2) with changing reaction conditions and precursors were studied.
- Qian,Zhang,Wang,Xie,Qian
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- On the synergism between La2O2S and CoS2 in the reduction of SO2 to elemental sulfur by CO
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In our study of the catalytic reduction of SO2 to elemental sulfur by CO in the presence of La2O2S and CoS2, a synergistic effect between the two sulfides was observed which not only increased the catalytic activity but also suppressed the formation of the side-product COS. It was also found that the crystal phase of CoS2, which can be easily reduced by CO, could be retained when La2O2S coexisted even in small quantities. A mechanism was proposed based on the COS intermediate mechanism and the remote control concept.
- Ma, Jianxin,Fang, Ming,Lau, Ngai Ting
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- A Solution-based Method for Synthesizing Pyrite-type Ferrous Metal Sulfide Microspheres with Efficient OER Activity
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Simple and stable synthesis of transition metal sulfides and clarification of their growth mechanisms are of great importance for developing catalysts, metal-air batteries and other technologies. In this work, we developed a one-step facile hydrothermal approach to successfully synthesize NiS2 microspheres. By changing the experimental parameters, the reason that affects the formation of nanostructured spheres is investigated and discussed in detail, and the formation mechanism of microspheres is proposed innovatively. Furthermore, electrochemical testing results show that the 7 h-NiS2 catalyst exhibits a remarkable oxygen evolution reaction (OER) activity with an overpotential of 311 mV at 10 mA cm?2 in 1.0 M KOH, superior to precious metal RuO2. The NiS2 catalyst also exhibits a robust durability. This work will contributes to the rational design and the understanding of growth mechanism of transition metal chalcogenide electrocatalysts for diverse energy conversion technologies.
- Deng, Yida,Han, Xiaopeng,Hu, Wenbin,Tian, Qianqiu,Xiang, Wendi,Zhong, Cheng
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- Synthesis and properties of cobalt sulfide phases: CoS2 and Co9S8
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Single phase cobalt disulfide (CoS2) nanoparticles were prepared by thermal decomposition of cobalt-thiourea complex at a low temperature (400 °C). CoS2 nanoparticles exhibit ferromagnetic ordering at 122 K below which the temperatur
- Kumar, Nitesh,Raman, Natarajan,Sundaresan, Athinarayanan
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- Magnetic properties of Co(S1-xSex)2 under high magnetic field and high pressure
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The magnetization of the metamagnetic Co(S1-xSex)2 system with 0 ≤ x ≤ 0.2 has been measured under high magnetic field and high pressure. The magnetic phase diagram is determined in the x-T plane. The magnetic properties a
- Goto,Shindo,Ogawa,Harada
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- X-RAY PHOTOELECTRON SPECTRA OF 3d TRANSITION METAL PYRITES.
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Photoelectron spectra of the synthetic compounds FeS//2, CoS//2, NiS//2, MnSe//2, CoSe//2, and NiSe//2 and of a natural crystal of MnS//2, all with the pyrite structure, are reported. The sulfur 3s and selenium 4s contributions are split into peaks for bonding and antibonding orbitals due to the covalent bonding in the molecular anion pairs. The difference in lineshape of the peaks for the bonding and antibonding orbitals is attributed to vibronic effects. The metal 2p//3/////2 spectra show the effects of multiplet splitting and satellites due to shake-up or shake-off processes. The valence band spectra consist of slightly overlapping contributions of anion p and metal 3d electrons. The metal 3d spectrum of FeS//2 has a single strong peak of width 0. 9 eV.
- van der Heide,Hemmel,van Bruggen,Hass
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- Pyrite formation via kinetic intermediates through low-temperature solid-state metathesis
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The preparation of materials with limited phase stabilities yet high kinetic activation barriers is challenging. Knowledge of their possible formation pathways aids in addressing these challenges. Metathesis reactions present an approach to circumvent these barriers; however, solid-state metathesis reactions are often too rapid from extensive self-heating to understand the reaction. The stoichiometric reaction of MCl2 salts (M = Mn, Fe, Co, Ni, Cu, Zn) with Na2S2 enables the formation of pyrite (FeS2), CoS2, and NiS2 at low temperatures (250-350 °C). Na2S2 has the same polyanionic dimer as found in the pyrite structure, which would suggest the possibility of a facile ion-exchange reaction. However, from high-resolution synchrotron X-ray diffraction and differential scanning calorimetry, the energetic driving force does not appear to result solely from NaCl formation but also from formation of intermediate and pyrite phases. It is apparent that the reaction proceeds through polyanionic disproportionation and formation of a low-density alkali-rich intermediate, followed by anionic comproportionation and atomic rearrangement into the pyrite phase. These results have profound implications for the use of low-temperature metathesis in achieving materials by design.
- Martinolich, Andrew J.,Neilson, James R.
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- In situ synthesis of CoS2/RGO nanocomposites with enhanced electrode performance for lithium-ion batteries
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This study reports a novel strategy of preparing CoS2/reduced graphene oxides (RGO) nanocomposites by employing graphene oxides (GO) as an oxidizing agent and Na2S2O3 as a reducing agent. CoS2 can be in situ synthesized with GO being reduced. X-ray diffraction (XRD), Raman spectrometry, scanning electron microscopy (SEM), transmission electron microscopy (TEM) and electrochemical test are used to characterize the nanocomposite. The CoS2 particles with the size of 150 nm are dispersed in the networks made from thin RGO nanosheets. The CoS 2/RGO nanocomposite as an anode material for lithium-ion batteries can deliver excellent reversible capacity retention (640 mA hg-1) after cycling 50 times when tested at 100 mA g-1 and rate performance. The enhanced electrochemical properties can be attributed to the nanoscale particles sizes of CoS2 in addition to the effects of RGO networks in preventing the agglomeration of CoS2 and absorbing lithium polysulfides during the charge-discharge processes.
- Qiu, Bin,Zhao, Xiuyun,Xia, Dingguo
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- Electronic effect of substituents on the hydrodesulfurization of ring substituted benzenethiols
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To clarify the electronic factors of the reactants affecting hydrodesulfurization (HDS) reactivity, the o-, m- and p-isomers of aminobenzenethiol (ABT), methoxybenzenethiol (MBT) and toluenethiol (TT) were hydrogenolyzed by a batch method over CoS2, NiS2 and a presulfided commercial HDS catalyst. In the hydrogenolysis of all the isomers of ABT, MBT and TT, HDS by cleavage of the C-S bond occurred selectively and was promoted by the presence of electron-releasing substituents in the ortho- and para-positions. Among the quantities obtained from the MINDO/3 calculation for a reactant, the next three are especially interesting: these are the coefficients of the ipso-carbon and the sulfur atoms in the highest occupied π-orbital (π-HOMO), CCHOMO and CSHOMO, and the energy level of π-HOMO. The differences in reactivity among the isomers of a substituted benzenethiol can be interpreted by use of the frontier π-electron densities (FED), 2(CCHOMO)2 and 2(CSHOMO)2. On the other hand, the differences in reactivity among the molecules, i.e., ABT, MBT, TT, and benzenethiol, shows a close correlation with the ratio of the two FEDs, (CCHOMO/CSHOMO)2, and also with the energy level of π-HOMO. It is suggested that the energy level and the FED assume an important role in the HDS reactivities and that the magnitudes of the FEDs on the positions of both the sulfur and the ipso carbon atoms affect the reactivities not independently but concertedly.
- Konuma,Takase,Kameda,Itabashi
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- Oxygen-Containing Amorphous Cobalt Sulfide Porous Nanocubes as High-Activity Electrocatalysts for the Oxygen Evolution Reaction in an Alkaline/Neutral Medium
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A novel OER electrocatalyst, namely oxygen-incorporated amorphous cobalt sulfide porous nanocubes (A-CoS4.6O0.6 PNCs), show advantages over the benchmark RuO2 catalyst in alkaline/neutral medium. Experiments combining with calculation demonstrate that the desirable O* adsorption energy, associated with the distorted CoS4.6O0.6 octahedron structure and the oxygen doping, contribute synergistically to the outstanding electrocatalytic activity.
- Cai, Pingwei,Huang, Junheng,Chen, Junxiang,Wen, Zhenhai
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- Copper dopants improved the hydrogen evolution activity of earth-abundant cobalt pyrite catalysts by activating the electrocatalytically inert sulfur sites
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Cobalt pyrite (CoS2) is considered to be a promising catalyst for the hydrogen evolution reaction (HER) due to its intrinsic metallicity and high catalytic activity. However, the catalytically inert S-sites and sluggish reaction kinetics severely impede its commercial application. Herein, combining systematic theoretical and experimental approaches, a highly active and stable Cu doped CoS2 catalyst for the HER is demonstrated. Cu dopants are proven to not only reduce the hydrogen adsorption free energy (ΔGH?) of the Co sites from 0.41 eV to -0.13 eV, but also arouse the inert S sites with the low ΔGH? of -0.11 eV. A large cathode current density (10 mA cm-2 at 52 mV), low Tafel slope (42 mV dec-1), large exchange current density (0.68 mA cm-2), and good stability were observed in the Co0.93Cu0.07S2 catalyst, which are better than those found for the previously reported CoS2-based catalysts. The success of improving the electrochemical performance via the introduction of Cu dopants offers new opportunities in the development of high performance CoS2-based electrodes for other energy-related applications.
- Zhang, Jingyan,Xiao, Baorui,Liu, Xiaoli,Liu, Peitao,Xi, Pinxian,Xiao, Wen,Ding, Jun,Gao, Daqiang,Xue, Desheng
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- Cobalt sulfide nanoparticles grown on nitrogen and sulfur codoped graphene oxide: An efficient electrocatalyst for oxygen reduction and evolution reactions
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Electrochemical oxygen evolution and reduction reactions have received great attention due to their importance in several key technologies such as fuel cells, electrolyzers, and metal-air batteries. Here, we present a simple approach to the preparation of cobalt sulfide nanoparticles in situ grown on a nitrogen and sulfur codoped graphene oxide surface. The particle size and phase were controlled by changing the treatment temperature. Cobalt sulfide nanoparticles dispersed on graphene oxide hybrids were successfully prepared by a solid-state thermolysis approach at different temperatures (400, 500, and 600 °C) using cobalt thiourea and graphene oxide. X-ray diffraction studies revealed that hybrids prepared at 400 and 500 °C result in pure CoS2 phase, whereas the hybrid prepared at 600 °C exhibits Co9S8 phase. X-ray photoelectron spectroscopy studies revealed that nitrogen and sulfur simultaneously codoped on the graphene oxide surface, and these sites act to anchor the CoS2 nanoparticles strongly on the GO surface. The strong coupling between CoS2 and N,S-GO was reflected in the improvement of the oxygen electrode potential. CoS2(400)/N,S-GO showed an outstanding oxygen electrode activity with a potential of about 0.82 V against a reversible hydrogen electrode in alkaline medium, which is far better than the performance of precious catalysts such as Pt/C (1.16 V), Ru/C (1.01 V), and Ir/C (0.92 V).
- Ganesan, Pandian,Prabu, Moni,Sanetuntikul, Jakkid,Shanmugam, Sangaraju
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- Preparation of CoS2 nanoflake arrays through ion exchange reaction of Co(OH)2 and their application as counter electrodes for dye-sensitized solar cells
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The cobalt sulfide nanoflake arrays prepared by the transformation of Co(OH)2 nanoflake arrays using the ion exchange reaction method were incorporated into Pt-free dye-sensitized solar cells (DSSCs). Morphologies and crystal structures of the cobalt sulfide and cobalt hydroxide nanoflakes arrays were characterized by SEM, TEM and XRD analyses. The electrochemical properties were determined by cyclic voltammetry (CV) measurement. The cobalt sulfide nanoflakes which were composed of CoS2 single crystals and their aggregates dispersing in the amorphous cobalt sulfide matrix were completely transferred by substitution of S2- for O2- in the ion exchange reaction. The DSSC assembled with cobalt sulfide nanoflake arrays as the counter electrode showed a photovoltaic conversion efficiency of 5.20%, which was close to that of DSSC with sputtered Pt as the counter electrode (5.34%). Therefore, the cobalt sulfide nanoflake array film can be considered as a promising alternative counter electrode for use in DSSCs due to its large surface area and high electrocatalytic performance.
- Tsai, Jung-Che,Hon, Min-Hsiung,Leu, Ing-Chi
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- Metal sulfide synthesis by self-propagating combustion of sulfur-containing complexes
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Coordination compounds of thiourea with cadmium(II), zinc(II), bismuth(III), and indium(III) nitrates were synthesized. The self-sustained combustion of these complexes, as well as that of thiosemicarbazide coordination compounds of nickel(II), cobalt(II)
- Tukhtaev,Boldyrev,Gavrilov,Larionov,Myachina,Savel'eva
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- New low-temperature preparations of some simple and mixed Co and Ni dispersed sulfides and their chemical behavior in reducing atmosphere
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A series of simple (CoS2, Co9S8, NiS2, NiS, Ni3S2) and mixed sulfides (NiCo2S4, Ni0.33Co0.67S2, Ni3Co6S8, CuCo2S4, Cu0.33Co0.67S2) was prepared using low-temperature procedures. To obtain the mixed sulfides, the mixtures of the solutions of the corresponding salts were precipitated by Na2S and then heated in a sulfiding atmosphere at 300 °C. It has been found that the product phase composition depends on the sulfiding atmosphere. Using a H2S/Ar mixture leads to pyrite type sulfides, whereas treatment in H2S/H2 flow allowed the preparation of Ni-Co and Cu-Co thiospinels. The as prepared highly dispersed single-phase materials were characterized by X-ray powder diffraction, scanning electron microscopy, temperature-programmed reduction (TPR), elemental analysis, and BET surface area measurements.
- Bezverkhyy,Danot,Afanasiev
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- New criteria for the applicability of combustion synthesis: The investigation of thermodynamic and kinetic processes for binary Chemical Reactions
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Combustion synthesis is a novel technique that utilizes the exothermic heat of a chemical reaction to maintain the reaction and to rapidly prepare materials. But, hitherto, none of unified criterion for the validation of combustion synthesis has been proposed. Herein, we proposed the conditions need to be met. In terms of kinetics, at the adiabatic temperature (Tad), the diffusion distance of atoms (lTad) within 0.1 s should be larger than the particle size of the reactants(d), that is, lTad≥d. For systems that satisfy Tad/Tm,L≥1(where Tm,L is the melting point of the low-melting point component of the reactants), the presence of a liquid phase significantly increases the atomic diffusion distance from nanometers to tens of microns, making the criterion lTad≥d simplified to Tad/Tm,L≥1 in most situations. In terms of thermodynamics, the system needs to ensure that the reaction components are in an activated state, that is, Tad/Tm,H ≥0.7, where Tm,H is the melting point of the high-melting point component. The criteria for the SHS reactions proposed in this study further improve the theoretical understanding of SHS reactions, and provide guidance for exploring the ultra-fast synthesis of binary and multicomponent compounds.
- Tan, Xiaoming,Su, Xianli,Yan, Yonggao,Uher, Ctirad,Zhang, Qingjie,Tang, Xinfeng
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- One-step synthesis of nickel cobalt sulphides particles: Tuning the composition for high performance supercapacitors
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NiS2-CoS2 composites with different Ni and Co molar ratios for supercapacitors (SCs) were synthesized by one-step hydrothermal co-deposition method using cheap Na2S2O3·5H2O as sulfur source. With the increase of Ni content, the composites particle size increases gradually and the hollow sphere structure becomes more obvious. The electrochemical measurements demonstrate that these composites possess a high specific capacitance (Cm) performance, good rate capability and long cycle stability. To be specific, the Cm of Ni/Co/S-1 composite is the largest, up to 954.3 F g-1 at 1 A g-1, and as high as 309.5 F g-1 even at large current density of 20 A g-1. Furthermore, the Ni/Co/S-1 maintains 99.9% of its initial Cm after 1000 cycles at 5 A g-1. Moreover, the asymmetric supercapacitors with Ni/Co/S-1 as positive electrode and active carbon as negative electrode are of prominent energy density of 29.3 W h-1 kg-1 at the power density of 0.7 kW kg-1, and superior cycling stability of 99.1% initial value retention after 1000 cycles.
- Zhang, Huaihao,Guan, Bing,Gu, Jiangna,Li, Yu,Ma, Chi,Zhao, Jing,Wang, Tianyi,Cheng, Changjing
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- Lattice-Matched CoP/CoS2Heterostructure Cocatalyst to Boost Photocatalytic H2Generation
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Transition-metal phosphides and sulfides are considered as promising cocatalysts for the photocatalytic hydrogen evolution reaction (HER), and the cocatalytic effect can be improved by directed heterostructure engineering. In this study, a novel lattice-matched CoP/CoS2 heterostructure having a nanosheet morphology was developed as an HER cocatalyst and integrated in situ onto graphitic carbon nitride (g-C3N4) nanosheets via a successive phosphorization and vulcanization route. First-principles density functional theory calculations evidenced that the construction of the lattice-matched CoP/CoS2 heterostructure resulted in the redistribution of interface electrons, enhanced metallic characteristics, and improved H? adsorption. As a result of these effects, the CoP/CoS2 heterostructure cocatalyst formed a 2D/2D Schottky junction with the g-C3N4 nanosheets, thus promoting photoelectron transfer to CoP/CoS2 and realizing fast charge-carrier separation and good HER activity. As expected, the CoP/CoS2 heterostructure exhibited excellent cocatalytic activity, and the optimal loading of the cocatalyst on g-C3N4 enhanced its HER activity to 3.78 mmol g-1 h-1. This work furnishes a new perspective for the development of highly active noble-metal-free cocatalysts via heterostructure engineering for water splitting applications.
- Hong, Xiaoyang,Yu, Xiaohui,Wang, Lele,Liu, Qinqin,Sun, Jingfang,Tang, Hua
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- Facet-controlled morphology of cobalt disulfide towards enhanced oxygen reduction reaction
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Catalytic activity has a significant contribution from exposed facets which are prominently correlated with morphology. It has been witnessed that even a small refinement in morphology alters the catalytic activity over several folds which is a key towards catalyst design. The present study thereby explores the design of octahedral CoS2 crystals with the aim of exposing highly active facets for the oxygen reduction reaction (ORR) which were carefully synthesized to incorporate carbon inherently. One-pot hydrothermal synthesis was employed using trisodium citrate and sodium thiosulfate. The resultant crystals of octahedral CoS2 with exposed {111} and {220} planes were revealed by HR-TEM and XRD studies. Detailed structure-activity insight regarding ORR was obtained using rotating ring disk electrode and electrochemical quartz crystal microbalance (EQCM) analysis and facet controlled octahedral CoS2 was shown to have the 50 fold increase in activity relative to other variants in an acidic medium and is comparable to a state-of-the-art Pt/C (20%) catalyst. The local catalytic activity of the CoS2 catalyst was visualized by the redox-competition mode of scanning electrochemical microscopy (RC-SECM).
- Singh, Vikram,Tiwari, Aarti,Nagaiah, Tharamani C.
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- A strongly coupled CoS2/ reduced graphene oxide nanostructure as an anode material for efficient sodium-ion batteries
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Sodium-ion batteries (SIBs) are highly attractive electrochemical devices for massive energy storage because of their low cost and abundance of sodium, but insufficient anode performance remains a key challenge for the commercialization of this attractive technology. In this study, a hierarchically porous CoS2/graphene composite with an architecture of CoS2 nanoparticles embedded in reduced graphene oxide (rGO) is synthesized through a one-step hydrothermal route allowing the growth of the CoS2 phase and the reduction of the graphene oxide simultaneously. This composite is applied as an anode material for SIBs, delivering favorable performance. The CoS2 phase consists of nanoparticles of ～10 nm that are uniformly anchored on the rGO, forming a CoS2/rGO hybrid with strong phase interaction. As a conversion-type anode for SIBs, the electrochemical testing results show significantly enhanced sodium-storage properties for the CoS2/rGO composite compared with that of bare CoS2. Impressively, the CoS2/rGO nanostructure exhibits a high discharge capacity of approximately 400 mAh g?1 after 100 cycles at specific current of 100 mA g?1, corresponding to approximately 80% of the discharge capacity in the second cycle. Such improvement may be due to the two-dimensional conductive network, homogeneous dispersion and immobilization of the CoS2 nanoparticles, as well as the enhanced wettability of the active material in the electrolyte by introducing rGO. The results suggest that this well-designed conversion-type CoS2 is a promising anode material for high-performance SIBs.
- Xie, Kongyan,Li, Li,Deng, Xiang,Zhou, Wei,Shao, Zongping
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- Hierarchical CoS2/Ni3S2/CoNiO:X nanorods with favorable stability at 1 A cm-2 for electrocatalytic water oxidation
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Herein, we have reported an easily synthesized CoS2/Ni3S2/CoNiOx water oxidation catalyst with excellent catalytic activity and superior durability. The as-prepared catalyst required overpotential (η) as low as 256 mV to exhibit a current density of 10 mA cm-2 in 1.0 M KOH. Remarkably, it sustained a current density of 1 A cm-2 for one week in 30% KOH solution with only 25 mV increment of η. Thus, it is a hopeful candidate as a highly-effective water oxidation electrode in practical applications.
- Lee, Husileng,Wu, Xiujuan,Ye, Qilun,Wu, Xingqiang,Wang, Xiaoxiao,Zhao, Yimeng,Sun, Licheng
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- A PEGylated deep eutectic solvent for controllable solvothermal synthesis of porous NiCo2S4 for efficient oxygen evolution reaction
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As ionic liquid analogues or quasi-ionic liquids, deep eutectic solvents (DESs) have been applied in many fields in the past few years. Herein, a novel PEGylated DES composed of PEG 200 and thiourea was formed for the first time and used for solvothermal synthesis of nickel cobalt sulfides. The structure and composition of the as-synthesized sulfides can be tuned by adjustment of the ratio of the reactants. The PEGylated DES plays multiple roles as a solvent, a shape-control agent, and a sulfur source in the synthesis of sulfides. Compared with traditional sulfuration routes, this proposed route is cost-effective and energy-efficient by combining solvothermal synthesis and the sulfuration process. The prepared sulfides were used as catalysts for electrochemical water oxidation and they exhibited excellent oxygen evolution reaction (OER) performance, especially for NiCo2S4 with hierarchical pores. The overpotential (η) demand was 337 mV for the current density reaching 10 mA cm-2 and the Tafel slope was 64 mV dec-1 in an alkaline medium (1 M KOH) for NiCo2S4. In addition, NiCo2S4 demonstrated long-term stability with little deactivation after either thirty hours of continuous operation or two thousand cycles and a high faradaic efficiency of 95.8%. Synergistic effects including a relatively high Brunauer-Emmett-Teller area, abundant active sites, easy diffusion of electrolytes and oxygen gas, and strong structural integrity contribute to the high activity and long-term stability of the catalyst for OER. This study provides a new method for the synthesis of hierarchically structured metal sulfides for energy conversion and storage applications.
- Jiang, Jingyun,Yan, Chuanyu,Zhao, Xinhui,Luo, Hongxia,Xue, Zhimin,Mu, Tiancheng
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- High-performance dye-sensitized solar cell based on an electrospun poly(vinylidene fluoride-co-hexafluoropropylene)/cobalt sulfide nanocomposite membrane electrolyte
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Electrospun poly(vinylidene fluoride-co-hexafluoropropylene) (PVdF-HFP) nanocomposite membranes incorporated with different weight percentages (1, 2 and 3 wt%) of cobalt sulfide (CoS) were prepared by an electrospinning technique. The surface morphology, crystallinity, porosity and electrolyte uptake of the electrospun nanocomposite membranes were examined. The prepared electrospun PVdF-HFP/CoS nanocomposite membranes (esCPM) were activated by an ionic liquid electrolyte containing 0.5 M LiI, 0.05 M I2, 0.5 M 4-tert-butylpyridine and 0.5 M 1-butyl-3-methylimidazolium iodide in acetonitrile to obtain electrospun PVdF-HFP/CoS nanocomposite membrane electrolytes (esCPMEs). The uniformly dispersed CoS nanoparticles increased charge transport and facilitated the diffusion of the redox couple in the electrolyte system. The electrochemical characteristics of the dye-sensitized solar cells depended on the amount of CoS incorporated into the esCPMEs. The photovoltaic performance of the dye-sensitized solar cell assembled using the esCPME incorporated with 1 wt% of CoS was measured and found to be 7.34%, which is higher than that of the dye-sensitized solar cell assembled using the esPME without CoS (6.42%).
- Vijayakumar,Subramania,Fei, Zhaofu,Dyson, Paul J.
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- Efficient Infrared-Light-Driven CO2 Reduction Over Ultrathin Metallic Ni-doped CoS2 Nanosheets
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Converting CO2 and H2O into carbon-based fuel by IR light is a tough task. Herein, compared with other single-component photocatalysts, the most efficient IR-light-driven CO2 reduction is achieved by an element-doped ultrathin metallic photocatalyst-Ni-doped CoS2 nanosheets (Ni-CoS2). The evolution rate of CH4 over Ni-CoS2 is up to 101.8 μmol g?1 h?1. The metallic and ultrathin nature endow Ni-CoS2 with excellent IR light absorption ability. The PL spectra and Arrhenius plots indicate that Ni atoms could facilitate the separation of photogenerated carriers and the decrease of the activation energy. Moreover, in situ FTIR, DFT calculations, and CH4-TPD reveal that the doped Ni atoms in CoS2 could effectively depress the formation energy of the *COOH, *CHO and desorption energy of CH4. This work manifests that element doping in atomic level is a powerful way to control the reaction intermediates, providing possibilities to realize high-efficiency IR-light-driven CO2 reduction.
- Xu, Jiaqi,Ju, Zhengyu,Zhang, Wei,Pan, Yang,Zhu, Junfa,Mao, Jiawei,Zheng, Xueli,Fu, Haiyan,Yuan, Maolin,Chen, Hua,Li, Ruixiang
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- Cobalt-Doped FeS2Nanospheres with Complete Solid Solubility as a High-Performance Anode Material for Sodium-Ion Batteries
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Considering that the high capacity, long-term cycle life, and high-rate capability of anode materials for sodium-ion batteries (SIBs) is a bottleneck currently, a series of Co-doped FeS2solid solutions with different Co contents were prepared by a facile solvothermal method, and for the first time their Na-storage properties were investigated. The optimized Co0.5Fe0.5S2(Fe0.5) has discharge capacities of 0.220 Ah g?1after 5000 cycles at 2 A g?1and 0.172 Ah g?1even at 20 A g?1with compatible ether-based electrolyte in a voltage window of 0.8–2.9 V. The Fe0.5 sample transforms to layered NaxCo0.5Fe0.5S2by initial activation, and the layered structure is maintained during following cycles. The redox reactions of NaxCo0.5Fe0.5S2are dominated by pseudocapacitive behavior, leading to fast Na+insertion/extraction and durable cycle life. A Na3V2(PO4)3/Fe0.5 full cell was assembled, delivering an initial capacity of 0.340 Ah g?1.
- Zhang, Kai,Park, Mihui,Zhou, Limin,Lee, Gi-Hyeok,Shin, Jeongyim,Hu, Zhe,Chou, Shu-Lei,Chen, Jun,Kang, Yong-Mook
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- Unusual CoS2 ellipsoids with anisotropic tube-like cavities and their application in supercapacitors
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Unusual CoS2 ellipsoids with anisotropic tube-like cavities have been synthesized from the simultaneous thermal decomposition and sulfidation of a preformed cobalt carbonate precursor. The as-prepared CoS2 ellipsoids show interesting supercapacitive properties with high capacitance and good cycling performance.
- Zhang, Lei,Wu, Hao Bin,Lou, Xiong Wen
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- One-step hydrothermal synthesis of a CoS2@MoS2 nanocomposite for high-performance supercapacitors
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A MoS2-coated CoS2 composite has been prepared successfully via a one-step hydrothermal method. This CoS2@MoS2 hybrid material has a distinct morphology with few-layer MoS2 wrapping the CoS2 nanoparticles. Serving as a supercapacitor electrode, the obtained CoS2@MoS2 hybrid material exhibits a remarkable specific capacitance of 1038 F/g, a high rate capability of 71.7%, and excellent cycling stability of 84.76% retention after 10000 cycles. The superior electrochemical properties of the CoS2@MoS2 nanocomposite are attributed to the synergistic effects between the layered MoS2 and conductive CoS2.
- Huang, Feng,Meng, Rongde,Sui, Yanwei,Wei, Fuxiang,Qi, Jiqiu,Meng, Qingkun,He, Yezeng
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- CdS nanorods anchored with CoS2 nanoparticles for enhanced photocatalytic hydrogen production
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Herein, we report the use of cobalt sulfide (CoS2) as efficient and inexpensive co-catalyst of CdS nanorods for photocatalytic water splitting. The aim is to explore the use of earth-abundant cobalt species to replace precious metals for the photocatalytic reactions. The results of first-principles DFT simulation and planar-averaged differential charge density calculation reveal that at the CoS2/CdS interface, CoS2 has zero band gap which is a class nature of precious metals, and functions as electron trap to enhance the transfer of hot electrons from CdS to CoS2. Owing to the merits of efficient charge separation, high exposure of active sites as well as large surface area, the CoS2/CdS composites exhibit outstanding photocatalytic activity in H2 production under visible light (?58 mmol·g?1 h?1), which is about 19 times that of CdS nanorods alone and 3 times that of 1 wt%Pt/CdS under the same conditions.
- Tang, Jie,Gao, Bin,Pan, Jinbo,Chen, Lang,Zhao, Zihao,Shen, Sheng,Guo, Jun-Kang,Au, Chak-Tong,Yin, Shuang-Feng
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- Synthesis of Lattice-Contracted Cobalt Disulfide as an Outstanding Oxygen Reduction Reaction Catalyst via Self-assembly Arrangement
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Identifying high-performance non-precious metal-based catalysts at the cathode is a major challenge for future practical applications. Herein, a soft-template route through a self-assembly arrangement of sulfur sources was successfully developed, facilitating the anion exchange. In addition, compared with pristine cobalt disulfide synthesized without templates, the cobalt disulfide prepared using the new method presented a lattice shrinking phenomenon due to the hindrance of cobalt hydroxide crystal cell. Based on X-ray absorption spectroscopy (XAS) and density functional theory (DFT) calculation, increased occupancy of eg orbitals was verified for the cobalt disulfide after shrinkage, which was the main factor for enhancing the intrinsic activity of the catalyst. Besides the microscopic morphologic structure, elementary composition, and the valence state of the elements, the possible growth process of the cobalt disulfide was also discussed in detail. As catalyst for the oxygen reduction reaction, CoS2 showed a similar half-wave potential (0.81 vs. 0.84 V for Pt/C) and higher diffusion-limiting current density (reaching 5.33 vs. 5.19 mA cm?2 for Pt/C) than a commercial Pt/C catalyst. Hence, our results provide a rational design direction for this type of catalysts.
- Zhang, Hao,Wang, Zhiqiang,Ma, Chenglong,Zhou, Zhenhua,Cao, Limei,Gong, Xueqing,Dong, Chunxiao,Yang, Ji
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- Experimental and computational investigation of structure and magnetism in pyrite Co1-xFexS2: Chemical bonding and half-metallicity
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Bulk samples of the pyrite chalcogenide solid solutions Co 1-xFexS2 (0≤x≤0.5), have been prepared and their crystal structures and magnetic properties studied by x-ray diffraction and SQUID magnetization measurements. Across the solution series, the distance between sulfur atoms in the persulfide (S22-) unit remains nearly constant. First principles electronic structure calculations using experimental crystal structures as inputs point to the importance of this constant S-S distance, in helping antibonding S-S levels pin the Fermi energy. In contrast hypothetical rock-salt CoS is not a good half metal, despite being nearly isostructural and isoelectronic. We use our understanding of the Co1-xFexS2 system to make some prescriptions for new half-metallic ferromagnetic.
- Ramesha,Seshadri, Ram,Ederer, Claude,He, Tao,Subramanian
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- Magnetocaloric effect of Co(S1-xSex) 2
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The magnetic entropy change, ΔSM, was measured for Co(S1-xSex)2 with 0≤x≤0.103, which is a system showing the itinerant electron metamagnetism (IEM). It was found that the peak value of -ΔSM shows a maximum at around x=0.08. The origin of this behavior is discussed in terms of the Clausius-Clapeyron relation.
- Wada,Tanaka,Tajiri
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- Formation of Hierarchical FeCoS2–CoS2 Double-Shelled Nanotubes with Enhanced Performance for Photocatalytic Reduction of CO2
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Hierarchical FeCoS2–CoS2 double-shelled nanotubes have been rationally designed and constructed for efficient photocatalytic CO2 reduction under visible light. The synthetic strategy, engaging the two-step cation-exchange reactions, precisely integrates two metal sulfides into a double-shelled tubular heterostructure with both of the shells assembled from ultrathin two-dimensional (2D) nanosheets. Benefiting from the distinctive structure and composition, the FeCoS2–CoS2 hybrid can reduce bulk-to-surface diffusion length of photoexcited charge carriers to facilitate their separation. Furthermore, this hybrid structure can expose abundant active sites for enhancing CO2 adsorption and surface-dependent redox reactions, and harvest incident solar irradiation more efficiently by light scattering in the complex interior. As a result, these hierarchical FeCoS2–CoS2 double-shelled nanotubes exhibit superior activity and high stability for photosensitized deoxygenative CO2 reduction, affording a high CO-generating rate of 28.1 μmol h?1 (per 0.5 mg of catalyst).
- Lou, Xiong Wen,Wang, Sibo,Wang, Yan,Zhang, Song Lin
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- Low-temperature molten salt synthesis of MoS2@CoS2 heterostructures for efficient hydrogen evolution reaction
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A versatile low-temperature molten salt approach has been developed for fabricating a MoS2@CoS2 heterostructure electrocatalyst, where low-cost molten KSCN serves as both the reaction medium and sulfur source. The as-obtained electrocatalyst with a defect-rich structure is highly efficient for the hydrogen evolution reaction (HER), delivering a low overpotential of 96 mV at an HER current density of 10 mA cm-2, a small Tafel slope of 60 mV dec-1, and outstanding durability. Density functional theory (DFT) calculations suggest that the heterostructures present an optimized Gibbs free energy of hydrogen adsorption (ΔGH?) close to zero, which is responsible for the excellent HER performance.
- He, Song,Du, Hongfang,Wang, Ke,Liu, Qianchi,Sun, Jinmeng,Liu, Yuhang,Du, Zhuzhu,Xie, Linghai,Ai, Wei,Huang, Wei
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- Taguchi based fuzzy logic optimization of multiple quality characteristics of cobalt disulfide nanostructures
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Cobalt sulfide nanostructures, with a formula of CoxS y, have recently received considerable attention due to their unique catalytic, electric, magnetic, optical, and mechanical properties. In this study, cobalt disulfide (CoS2) nanoparticles have been synthesized by the solvothermal method using cobalt chloride and sodium thiosulfate as the precursors. The Taguchi method has been implemented to investigate and optimize the affecting parameters involved in minimizing the band-gap energy. Then, the predictions used to model the anticipated results with fuzzy logic. It has been found that the reaction temperature and the precursor ratio are the most effective parameters when attempting to minimize the band-gap energy.
- Rajabloo,Ghafarinazari,Seyed Faraji,Mozafari
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- Single-step microwave mediated synthesis of the CoS2 anode material for high rate hybrid supercapacitors
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A short time microwave irradiation based synthesis method of phase pure cubic CoS2 nanoparticles is reported in this study for the first time. The energy density (ED) of hybrid supercapacitors based on CoS2 as an anode having activated carbon as a cathode has been enhanced by using the higher operating potential of organic electrolytes and by increasing the concentration of the mobile ionic species at the negative electrode, in addition to the lithium ions present in the electrolyte. The specific capacitance delivered by non-lithiated CoS2 nanoflakes was 52 F g-1 at a current rate of 0.7 A g-1 between 0 and 3 V using a LiPF 6-based electrolyte. Increasing the concentration of the mobile ionic species, i.e., lithium, at the anode enhanced the performance of the hybrid supercapacitor to 119 F g-1 at a current rate of 0.7 A g -1. The hierarchical arrangement of pores in the electroactive material allowed high electrolyte access and reduced the length of the ionic pathway. Consequently, the lithiated form exhibited an ED of 37 W h kg -1 with a power density of 1 kW kg-1 at a current rate of 0.7 A g-1, compared to only 15 W h kg-1 for the non-lithiated sample. Furthermore, both samples maintained superior stability over extended cycling for 10 000 cycles at a very high PD of 4 kW kg -1 with a capacitance retention of 100% for the lithiated sample and 80% for the non-lithiated sample. These results will be useful in the fabrication of high ED, high rate hybrid supercapacitors for electric vehicle applications.
- Amaresh,Karthikeyan,Jang,Lee
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- Magnetic properties of the itinerant metamagnetic system Co(S1-xSex)2 under high magnetic fields and high pressure
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The magnetization of the Co(S1-x-Sex)2 system with 0≤x≤0.2 has been measured under high magnetic fields and high pressure. Ferromagnetic CoS2 exhibits a second-order transition at T2=122 K. Substitution of 10% Se for S in CoS2 reduces the Curie temperature to Tc.=27 K and the transition to first order. Co(S1-xSex)2 with 0.12≤x becomes an exchange-enhanced Pauli paramagnet. The itinerant metamagnetic transition has been observed in the paramagnet. Co(S0.9Se0.1)2 also shows a transition just above Tc. Using the experimental data, the magnetic phase diagram of Co(S1-xSex)2 is determined. With increasing pressure, the Curie temperature of CoS2 decreases and the ferromagnetic transition changes to first order at P≈0.4 GPa. In the pressure regime of the first-order transition P>0.4 GPa, the metamagnetic transition is observed just above Tc. In Co(S0.9Se0.1)2, the ferromagnetism disappears at 0.25 GPa and paramagnetism appears. The observed magnetic properties and the magnetic phase diagram of Co(S1-x.Sex)2 can be qualitatively described with a theory of the itinerant electron metamagnetism at finite temperatures.
- Goto,Shindo,Takahashi,Ogawa
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- Ferromagnetic transition of heisenberg ferromagnetic metal of CoS 2 - Static critical properties
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The static magnetic properties near the Curie temperature in CoS 2 have been thoroughly studied by using various experimental techniques from high quality single crystals, which were grown by the chemical transport technique. A very small anisotropy in magnetization confirms that CoS2 is the best system to apply the Heisenberg Hamiltonian. The critical indices obey the static scaling hypothesis, which indicates negligible effect of the temperature-induced local moment on the ferromagnetic transition. However, the static critical properties suggest that the magnetic transition is close to the tricritical point, although the magnetic transition in CoS 2 is continuous.
- Hiraka, Haruhiro,Endoh, Yasuo
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- Hierarchical mesoporous CoS2 microspheres: Morphology-controlled synthesis and their superior pseudocapacitive properties
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A simple and novel strategy has been developed for the morphology-controlled synthesis of hierarchical CoS2 microspheres. The hierarchical mesoporous CoS2 architecture constructed by ultrathin nanosheets, when applied as electrode materials for supercapacitors, achieves a highest specific capacitance of 718.7 F g-1 at 1 A g-1 under a high mass loading, excellent rate capability (66.3% capacitance retention from 1 A g-1 to 20 A g-1), and good cycling stability (only a loss of 7.0% in the specific capacitance after 1000 cycles). Therefore, this work provides a promising approach for the rational design and synthesis of morphology-tunable micro/nanomaterials with superior properties for supercapacitors and other electrochemical applications.
- Xing, Jia-Chao,Zhu, Yan-Li,Li, Meng-Yao,Jiao, Qing-Jie
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- Hydrothermal synthesis of WO3/CoS2n-n heterojunction for Z-scheme photocatalytic H2evolution
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One of the most effective methods to improve electron-transfer efficiency and photocatalytic reaction activity is to construct a photocatalyst with a heterojunction interface. Herein, a WO3/CoS2 n-n heterojunction composite catalyst was synthesized, and used in photocatalytic hydrogen evolution, and was optimized by adjusting the pH of the triethanolamine solution, the amount of Eosin Y added, and the content of WO3 in the composite catalyst. After 5 h of photocatalytic reaction, WO3/CoS2 (WCS-2) had a H2 production of 221.15 μmol, which was 80.41 times that of single WO3 and 2.17 times that of CoS2, and had good stability. XRD, SEM, TEM, and XPS characterization results indicated that WO3/CoS2 was successfully prepared. Fluorescence test and electrochemical test results showed that the WO3/CoS2 catalyst had a higher photoelectron transfer efficiency. Finally, it is pointed out that WO3/CoS2 enhanced the photocatalytic activity, which may be due to the electron migration of WO3 and CoS2 following the Z-scheme mechanism. This work presents a new idea for constructing n-n heterojunction to enhance the activity in photocatalytic hydrogen production.
- Ma, Lijun,Xu, Jing,Li, Lingjiao,Mao, Min,Zhao, Sheng
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- Self-template synthesis of hierarchical CoMoS3 nanotubes constructed of ultrathin nanosheets for robust water electrolysis
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Exploration of pH-universal and durable catalysts with specific structure and high performance is desirable but challenging for electrochemical water splitting. Aiming at this goal, hierarchical CoMoS3 nanotubes constructed of ultrathin nanosheet subunits are prepared via a self-sacrifice template method. The conversion from CoMoO4 nanorods to hierarchical MoCoS3 nanotubes is successfully realized through a facile solvothermal process. The obtained sample simultaneously possesses advanced structural superiority and synergism of ternary Co-Mo-S. Endowed with these advantages, MoCoS3 can serve as a pH-universal and high-performance electrocatalyst for hydrogen evolution, delivering low onset overpotential, small overpotential required to generate current density of 10 mA cm-2, and good stability. Moreover, it exhibits excellent catalytic performance in the electrochemical oxygen evolution reaction, making it a promising dual-functional catalyst for water electrolysis.
- Zhang, Xiao,Guo, Jinxue,Zhang, Xinqun,Sun, Yanfang,Tang, Lin
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- Deep eutectic-solvothermal synthesis of nanostructured Fe3S4 for electrochemical N2 fixation under ambient conditions
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We report the synthesis of nanostructured Fe3S4 from deep eutectic solvents via a one-step solvothermal method. The as-obtained Fe3S4 catalyst was capable of electrochemically reducing N2 to NH3 under ambient conditions, and exhibits a high NH3 yield (75.4 μg h?1 mg?1cat.) and faradaic efficiency (6.45%) at ?0.4 V vs. a reversible hydrogen electrode.
- Zhao, Xinhui,Lan, Xue,Yu, Dongkun,Fu, Hui,Liu, Zhimin,Mu, Tiancheng
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- Synthesis of CuS@CoS2 Double-Shelled Nanoboxes with Enhanced Sodium Storage Properties
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Metal sulfides have received considerable attention for efficient sodium storage owing to their high capacity and decent redox reversibility. However, the poor rate capability and fast capacity decay greatly hinder their practical application in sodium-ion batteries. Herein, an elegant multi-step templating strategy has been developed to rationally synthesize hierarchical double-shelled nanoboxes with the CoS2 nanosheet-constructed outer shell supported on the CuS inner shell. Their structure and composition enable these hierarchical CuS@CoS2 nanoboxes to show boosted electrochemical properties with high capacity, outstanding rate capability, and long cycle life.
- Fang, Yongjin,Guan, Bu Yuan,Luan, Deyan,Lou, Xiong Wen (David)
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- Macrocyclic amines as structure-directing agents for the synthesis of three-dimensional antimony-sulfide frameworks
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A new family of antimony sulfides, incorporating the macrocyclic tetramine 1,4,8,11-tetraazacyclotetradecane (cyclam), has been prepared by a hydrothermal method. [C10N4H26][Sb4S7] (1), [Ni(C10N4H24)][Sb4S 7] (2), and [Co(C10N4H24)] x[C10N4H26]1-x[Sb 4S7] (0.08 ≤ x ≤ 0.74) (3) have been characterized by single-crystal X-ray diffraction, elemental analysis, thermogravimetry, and analytical electron microscopy. All three materials possess the same novel three-dimensional Sb4S72- framework, constructed from layers of parallel arrays of Sb4S8 4- chains stacked at 90° to one another. In 1, doubly protonated macrocyclic cations reside in the channel structure of the antimony-sulfide framework. In 2 and 3, the cyclam acts as a ligand, chelating the divalent transition-metal cation. Analytical and X-ray diffraction data indicate that the level of metal incorporation in 2 is effectively complete, whereas in 3, both metalated and nonmetalated forms of the macrocycle coexist within the structure.
- Powell, Anthony V.,Lees, Rachel J. E.,Chippindale, Ann M.
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- High performance electrocatalysis for hydrogen evolution reaction using nickel-doped CoS2 nanostructures: experimental and DFT insights
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Development of non-noble-metal electrocatalysts with high activity and durability is a competitive strategy for the practical applications of water splitting which including hydrogen evolution reaction (HER) as well as oxygen evolution reaction (OER). In this work, high-quality CoS2 ultrathin nanosheets were synthesized through a simple and efficient hydrothermal method. After merging 10% wt Ni, the bimetal catalyst (Co0.9Ni0.1S2) displays excellent catalytic activity (10 mA cm?2 at an overpotential of 156 mV and a small Tafel slope of 52 mV dec?1) as well as stability (over 3000 cycles without obvious decay) in acid condition. Based on the results of Density Functional Theory (DFT) calculations, H+ adsorbed competition, hydrogen formation energetic and kinetics are proposed to help us understand the high efficient HER process over the Co0.9Ni0.1S2 (CNS) ultrathin nanosheets.
- Cui, Yan,Zhou, Chunwu,Li, Xinze,Gao, Yuan,Zhang, Jian
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- TRANSITION METAL POLYSULFIDES AS BATTERY CATHODES.
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Amorphous polysulfides of iron, nickel, and cobalt were prepared and characterized. The resulting compounds, Co//2 S//7, Co//2S//9, Ni//2S//7, and Fe//3S//8 were evaluated as cathode materials in organic electrolyte lithium batteries. The cobalt compounds in particular delivered very high capacities of 1-1. 2 A-h/g at voltages around 1. 8v. The resulting cells possessed high gravimetric and volumetric energy densities.
- Bowden,Barnette,DeMuth
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- Magnetocaloric effect of Co(S1-xSex)2 under high pressure
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We examined the magnetocaloric effect of Co(S1-xSe x)2, which shows typical itinerant electron metamagnetism, under high pressures up to 1.2 GPa. It was found that the magnetic entropy change, δSM, of x = 0 incr
- Sadakuni, Osamu,Mituda, Akihiro,Wada, Hirofumi
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- Construction of CoS2/Zn0.5Cd0.5S S-Scheme Heterojunction for Enhancing H2 Evolution Activity Under Visible Light
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In the field of photocatalysis, building a heterojunction is an effective way to promote electron transfer and enhance the reducibility of electrons. Herein, the S-scheme heterojunction photocatalyst (CoS2/Zn0.5Cd0.5S) of CoS2 nanospheres modified Zn0.5Cd0.5S solid solution was synthesized and studied. The H2 evolution rate of the composite catalyst reached 25.15 mmol g?1 h?1, which was 3.26 times that of single Zn0.5Cd0.5S, whereas pure CoS2 showed almost no hydrogen production activity. Moreover, CoS2/Zn0.5Cd0.5S had excellent stability and the hydrogen production rate after six cycles of experiments only dropped by 6.19 %. In addition, photoluminescence spectroscopy and photoelectrochemical experiments had effectively proved that the photogenerated carrier transfer rate of CoS2/Zn0.5Cd0.5S was better than CoS2 or Zn0.5Cd0.5S single catalyst. In this study, the synthesized CoS2 and Zn0.5Cd0.5S were both n-type semiconductors. After close contact, they followed an S-scheme heterojunction electron transfer mechanism, which not only promoted the separation of their respective holes and electrons, but also retained a stronger reduction potential, thus promoting the reduction of H+ protons in photocatalytic experiments. In short, this work provided a new basis for the construction of S-scheme heterojunction in addition to being used for photocatalytic hydrogen production.
- Ma, Lijun,Xu, Jing,Zhao, Sheng,Li, Lingjiao,Liu, Ye
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- One-pot synthesis of MoS2/CoS2 yolk-shell nanospheres
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In this work, MoS2/CoS2 yolk-shell nanospheres are synthesized by a one-pot hydrothermal reaction. Furthermore, the yolk-shell spherical morphologies are characterized and confirmed by SEM, TEM characterizations; and the components of CoS2 and MoS2 are investigated by XRD and XPS analysis. It is revealed that the Co precursor and thiourea result in the formation of hollow CoS2 nanospheres, while the Co precursor, Mo precursor and thiourea lead to the fabrication of MoS2/CoS2 yolk-shell nanostructure. The possible growth mechanism of MoS2/CoS2 yolk-shell nanospheres is suggested based on the comparative experiments and characterization of intermediate samples. This research provides a feasible and new strategy to prepare the MoS2/CoS2 hybrid material with yolk-shell architecture.
- Jia, Yulong,Lin, Yinhe,Ma, Ying,Yin, Guoliang
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- MoS2/CoS2 heterostructures embedded in N-doped carbon nanosheets towards enhanced hydrogen evolution reaction
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MoS2/CoS2 heterostructures on nitrogen-doped carbon nanosheets as an efficient electrocatalyst for hydrogen evolution reaction (HER) are prepared using zeolitic imidazolate frameworks-67 as precursors. Two dimensional (2D)/2D MoSsub
- Ji, Kang,Matras-Postolek, Katarzyna,Shi, Ruixia,Chen, Ling,Che, Quande,Wang, Junpeng,Yue, Yunlong,Yang, Ping
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- Intercalation of cobalt cations into Co9S8interlayers for highly efficient and stable electrocatalytic hydrogen evolution
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Non-noble metal based electrocatalysts for the hydrogen evolution reaction (HER) hold great potential for commercial applications. However, effective design strategies are greatly needed to manipulate the catalyst structures to achieve high activity and stability comparable to those of noble-metal based electrocatalysts. Herein, we present a facile route to synthesize layered Co9S8 intercalated with Co cations (Co2+-Co9S8) (with interlayer distance up to 1.08 nm) via a one-step solvothermal method. Benefiting from a large interlayer distance and efficient electron transfer between layers, the Co2+-Co9S8 hybrid shows outstanding electrocatalytic hydrogen evolution performance in an acid electrolyte. The electrocatalytic performance is even better than that of 20% Pt/C at the a current density of 10 mA cm-2 in 0.5 mol L-1 H2SO4. More importantly, the system can maintain excellent stability for more than 12 h without obvious decay. This study not only presents a novel and efficient approach to synthesize cobalt sulfide intercalated with Co cations for stable electrocatalytic HER but also provides an avenue for the design of intercalated materials used in other energy applications.
- Cao, Dongmei,Cheah, Pohlee,Han, Fengxiang,Kolodziejczyk, Wojciech,Qu, Jing,Saloni, Julia,Tian, Bin,Zhao, Yongfeng,Zhu, Xianchun
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supporting information
p. 3522 - 3530
(2022/02/25)
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- Hydrothermal Synthesis of Mn3O4/CoS2 as a Promising Photocatalytic Material for Boosting Visible-Light Photocatalytic Hydrogen Production
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Photocatalytic hydrogen evolution has received extensive attention for energy conversion and storage of clean energy. Herein, the composite catalyst Mn3O4/CoS2 is successfully prepared by a hydrothermal method. Photocatalytic hydrogen evolution experiments are conducted by adjusting the amount of Mn3O4. The results show that the composite photocatalyst Mn3O4/CoS2 has higher photocatalytic hydrogen evolution performance. The hydrogen production of the 50 mg Mn3O4/CoS2 composite catalyst at 5 h is 14.95 times and 1.60 times that of pure Mn3O4 and CoS2, respectively, indicating that the 50 mg Mn3O4/CoS2 composite catalyst has good photocatalytic stability. In addition, the structure, morphology, and composition of the prepared catalysts are characterized by scanning electron microcopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Brunauer–Emmett–Teller (BET), electrochemical and PL techniques. Compared with Mn3O4 and CoS2, the photocatalytic response of the 50 mg Mn3O4/CoS2 composite catalyst is significantly enhanced, the current density is increased, the fluorescence quenching efficiency is accelerated, and the pore volume and pore size are increased. Therefore, the composite catalyst can accelerate the separation and transfer of photogenerated electrons and holes and improve the photocatalytic efficiency.
- Xu, Jing,Liu, Ye,Li, Xuanhao,Li, Yanru
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- Hollow ZIF-67 derived porous cobalt sulfide as an efficient bifunctional electrocatalyst for overall water splitting
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The design and construction of noble-metal free electrocatalysts with high efficiency for both hydrogen and oxygen evolution reactions holds promise for advancing the production of H2fuels through the overall water splitting process. Herein, we report a novel hollow near-spherical superstructure of a cobalt sulfide electrocatalyst (h-CoxSy)viathe accumulation of two-dimensional cobalt sulfide nanosheets in a sulfurization-pyrolysis process of hollow ZIF-67. Benefiting from the porous characteristics, a unique hollow superstructure and saw-toothed edges derived from the hollow ZIF-67 precursor, the h-CoxSyexhibited outstanding bifunctional electrocatalytic performances, with overpotentials of 320 and 295 mV to achieve 10 mA cm-2for the OER and HER, respectively. When h-CoxSywas employed as both the anode and cathode for overall water splitting, a current density of 10 mA cm-2can be obtained at a cell voltage of 1.88 V, along with impressive operation stability.
- Zhang, Zewu,Li, Shijia,Bu, Xiaohai,Dai, Yifan,Wang, Jingxi,Bao, Xuwen,Wang, Tong
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p. 17313 - 17319
(2021/10/04)
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- Rare earth material CeO2modified CoS2nanospheres for efficient photocatalytic hydrogen evolution
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The development of high-efficiency and low-cost photocatalysts for hydrogen production reactions is very important to solve energy problems. In this paper we study the photocatalytic H2 evolution activity of a CeO2/CoS2 heterojunction catalyst under visible light. Characterization studies such as XRD and XPS proved the successful synthesis of a CeO2/CoS2 catalyst. The composite catalyst with a CeO2 and CoS2 mass ratio of 1?:?20 had the best activity, and the hydrogen evolution rate reached 5172.20 μmol g-1 h-1. BET and UV-Vis DRS characterization showed that the introduction of CeO2 not only increased the specific surface area of the composite catalyst, but also improved the response of the photocatalyst to visible light. In addition, PL and electrochemical experiments showed that the electrons and holes of the CeO2/CoS2 catalyst could be quickly separated and transferred, thereby accelerating the kinetics of the hydrogen evolution reaction. This work provided an experimental basis for designing a composite photocatalyst with high stability and hydrogen production activity.
- Liu, Xinyu,Liu, Zhenlu,Ma, Lijun,Xu, Jing,Zhang, Juan
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p. 21795 - 21806
(2021/12/13)
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- Constructing high-performance H3PW12O40/CoS2counter electrodes for quantum dot sensitized solar cells by reducing the surface work function of CoS2
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A low cost H3PW12O40 (PW12)/CoS2 complex is prepared and used as a counter electrode (CE) to combine with sandwich quantum dot sensitized solar cells (QDSSCs) composed of a TiO2/CdS/CdSe/ZnS photoanode and polysulfide electrolyte to study their photovoltaic properties via a simple hydrothermal method. Under standard simulated sunlight, the photoelectric conversion efficiency (PCE) of 2%PW12 (PW12-2/CoS2) doped CEs was 6.29%, which was significantly 67.7% higher than those of QDSSCs based on undoped CoS2 CEs (3.75%). Due to the introduction of PW12, the nanoparticles forming the hollow structure of CoS2 changed from regular octahedra to rough nanoparticles, which increase the active sites. At the same time, the work function of CoS2 decorated with PW12 is decreased. This study and discovery demonstrate that POMs can be used to optimize CE materials and improve the photoelectric conversion efficiency of QDSSCs, which provide an experimental and theoretical basis for subsequent investigations.
- Zhang, Tingting,Zhang, Qiu,Wang, Yumeng,Li, Fengyan,Xu, Lin
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p. 12879 - 12887
(2021/10/12)
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- Enhancing the reversibility of SnCoS4 microflower for sodium-ion battery anode material
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As the demand of high-performance energy storage devices rises in many applications, sodium-ion batteries have gained widespread researching attention as an alternative of lithium-ion batteries. Because of the high theoretical capacity, SnS2 received intensive interests. Yet, the undesirable initial Coulombic efficiency and high hysteresis during charge and discharge reactions restrict their possible applications. To circumvent the poor initial Coulombic efficiency of tin sulfide anode materials and prevent the coarsening of Sn nanograins and reduction of the conversion reaction interface between Na2S and metallic Sn, SnCoS4 microflower was successfully designed and synthesized as anode material for sodium-ion batteries. The in situ formed Co nanoclusters restrict the coarsening of the materials and promote the sodiation and desodiation reactions, and therefore highly enhance the reversibility and initial Coulombic efficiency. The SnCoS4 composite shows a highly reversible capacity of 477.76 mA h/g at 100 mA/g with a lower charge-discharge hysteresis.
- Zhong, Jiayi,Xiao, Xuezhang,Wu, Zunchun,Zhang, Nan,Jiang, Ruicheng,Fan, Xiulin,Chen, Lixin
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- Metal-organic framework-derived hierarchical MoS2/CoS2 nanotube arrays as pH-universal electrocatalysts for efficient hydrogen evolution
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The exploitation of efficient earth-abundant electrocatalysts in a wide pH range is crucial for the practical application of the hydrogen evolution reaction (HER); but it still remains challenging. Here we demonstrate novel self-supported hierarchical MoS2/CoS2 nanotube arrays as efficient pH-universal electrocatalysts, where Co metal-organic frameworks (MOFs) are used as a precursor and sacrificial template to form one-dimensional CoS2 nanotubes surrounded by vertically aligned two-dimensional MoS2 nanosheets. Owing to the achievement of a unique hollow architecture with abundant exposed edges and accelerated reaction kinetics, the self-supported MoS2/CoS2 heterostructure exhibits a superior HER catalytic performance with long-term durability in acidic, neutral and alkaline electrolytes. Impressively, it delivers a current density of 10 mA cm-2 at low overpotentials of 90 mV in acidic media and 85 mV in alkaline media and small Tafel slope values of 30 mV dec-1 in acidic media and 34 mV dec-1 in alkaline media, respectively. Our first-principles calculations reveal that the strong interfacial interactions between MoS2 and CoS2 increase the electronic states at S-S edges and dramatically reduce the Gibbs free energy of hydrogen and the energy barrier for water dissociation. Overall, this work offers an exciting avenue for the rational design of hollow heterogeneous catalyst arrays by MOF-engaged interfacial engineering for scalable hydrogen generation.
- Tang, Baoshan,Yu, Zhi Gen,Zhang, Yaoxin,Tang, Chunhua,Seng, Hwee Leng,Seh, Zhi Wei,Zhang, Yong-Wei,Pennycook, Stephen John,Gong, Hao,Yang, Weifeng
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supporting information
p. 13339 - 13346
(2019/06/13)
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- Defect-rich (Co-CoS2)x@Co9S8 nanosheets derived from monomolecular precursor pyrolysis with excellent catalytic activity for hydrogen evolution reaction
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The construction of defects in two-dimensional ultrathin nanosheets will improve the activity of transition metal-based catalysts. CoSx-based electrocatalysts have attracted increasing attention because of their low cost. In this article, defec
- Zhang, Xinwen,Liu, Yanyan,Gao, Jie,Han, Guosheng,Hu, Meifang,Wu, Xianli,Cao, Huaqiang,Wang, Xiangyu,Li, Baojun
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supporting information
p. 7977 - 7987
(2018/05/14)
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- Boosting the oxygen evolution reaction performance of CoS2 microspheres by subtle ionic liquid modification
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Hierarchical CoS2 microspheres were prepared and modified with a cationic ionic liquid (IL). The composite shows enhanced oxygen evolution reaction (OER) performances attributed to the fact that the OER equilibrium is driven forward by the IL, according to Le Chatelier's principle, and by the electrostatic affinity generated at the CoS2/electrolyte interface.
- Ji, Siyuan,Li, Tongtong,Gao, Zhi-Da,Song, Yan-Yan,Xu, Jing-Juan
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supporting information
p. 8765 - 8768
(2018/08/09)
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- Graphene-supported CoS2 particles: An efficient photocatalyst for selective hydrogenation of nitroaromatics in visible light
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CoS2/graphene composites fabricated by a facile hydrothermal method exhibit excellent photocatalytic performance for selective hydrogenation of nitroaromatics to the corresponding aniline employing molecular hydrogen as a reducing agent under visible light irradiation (400-800 nm). The rate constant of the composite catalyst for nitrobenzene hydrogenation can achieve as high as 35.50 × 10-3 min-1 with a selectivity of 100% toward the target product under mild conditions (30°C and 0.25 MPa pressure of H2). The catalyst also shows high recyclability, and there is no decrease in the catalytic activity after five successive cycles. There exists a synergistic effect between the graphene support and the CoS2 particles: conductive graphene as the support can rapidly extract the photoexcited electrons and effectively suppress the recombination of photogenerated charges in CoS2 particles, and then improve the photocatalytic performance. The photocatalytic reduction of nitrobenzene over the CoS2/graphene catalyst to aniline occurs through the direct pathway in the presence of H2.
- Ma, Ben,Wang, Yingyong,Tong, Xili,Guo, Xiaoning,Zheng, Zhanfeng,Guo, Xiangyun
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p. 2805 - 2812
(2017/07/15)
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- Highly stable hollow bifunctional cobalt sulfides for flexible supercapacitors and hydrogen evolution
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Hollow structures of NiAs-type cobalt sulfide have been synthesized by a facile hydrothermal method. These hollow structured cobalt sulfides exhibit excellent electrochemical properties for supercapacitor applications (867 F g-1) and respectable hydrogen evolution activity. The symmetrical supercapacitor device fabricated using cobalt sulfide nanostructures showed an areal capacitance of 260 mF cm-2 with good flexibility and high temperature stability. The specific capacitance of the supercapacitor is enhanced over 150%, when the temperature is increased from 10 to 70 °C.
- Ranaweera,Wang,Alqurashi, Esam,Kahol,Dvornic,Gupta, Bipin Kumar,Ramasamy, Karthik,Mohite, Aditya D.,Gupta, Gautam,Gupta, Ram K.
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supporting information
p. 9014 - 9018
(2016/07/06)
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- Increased activity in hydrogen evolution electrocatalysis for partial anionic substitution in cobalt oxysulfide nanoparticles
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The functionality of an electrocatalyst depends sensitively on the surface chemistry. In the case of transition-metal compounds, both the transition metal cation and the anion must be controlled to maximize the electrocatalytic activity. This realization has driven many efforts devoted to engineering the cation chemistry, producing many state-of-the-art electrocatalysts. Motivated by the critical role the cation plays in electrocatalysis, we seek to understand whether a similar effect can be achieved with the anion. Herein, we present a study on the effect of the anion substitution on the hydrogen evolution reaction (HER) electrocatalysis on cobalt oxysulfide nanoparticles. To control the sulfur substitution, we use ammonium sulfide to introduce sulfur to the cobalt oxide nanoparticles at low temperature without inducing secondary phase formation. We find that a lightly doped oxysulfide catalyst, which has the composition CoOxS0.18, exhibits a metastable, distorted S-substituted CoO phase and is 2-3 times more active for the HER than either end-member of the substitution series. Our first-principles calculations attribute the HER enhancement to the stronger surface H adsorption which is maximally favorable at a relatively low doping level. Our work provides a protocol for synthesizing metastable mixed-anion materials and reveals the critical role of the anion on the surface physiochemical properties and the HER electrocatalysis.
- Nelson, Andrew,Fritz, Kevin E.,Honrao, Shreyas,Hennig, Richard G.,Robinson, Richard D.,Suntivich, Jin
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supporting information
p. 2842 - 2848
(2016/03/01)
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- In situ formation of flower-like CuCo2S4 nanosheets/graphene composites with enhanced lithium storage properties
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Flower-like CuCo2S4 nanosheets/graphene composites (abbreviated as CCS-G) were prepared by using a one-pot hydrothermal method. The morphology and structure of CCS-G were investigated by scanning electron microscope (SEM), transmission electron microscope (TEM), X-ray diffraction (XRD) and Raman spectroscopy. SEM and TEM images showed the hierarchical structure of CCS-G with flower-like morphology, which were composed of many nanosheets. As an anode material for the rechargeable lithium-ion batteries (LIBs), CCS-G exhibited the remarkably enhanced Li-storage performance in comparison with the pristine flower-like CuCo2S4 nanosheets (abbreviated as CCS). The reversible capacity of CCS-G is maintained to be 778.9 mA h g-1 at a current density 0.1C after 60 cycles. Even at a high current density of 1C, CCS-G retains a much high specific capacity of 866.3 mA h g-1 after 500 cycles.
- Nie, Longying,Wang, Huijun,Chai, Yaqin,Liu, Sheng,Yuan, Ruo
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p. 38321 - 38327
(2016/05/19)
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- Facile synthesis of CuCo2S4 as a novel electrode material for ultrahigh supercapacitor performance
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CuCo2S4 nanoparticles demonstrating outstanding electrochemical performances were firstly synthesized through a simple solvothermal approach without using any templates. CuCo2S4 synthesized in glycerol (CuCo2S4-glycerol) fulfills an ultrahigh capacitance of 5030 F g-1 at 20 A g-1 in a polysulfide electrolyte.
- Tang, Jianhua,Ge, Yuancai,Shen, Jianfeng,Ye, Mingxin
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supporting information
p. 1509 - 1512
(2016/01/25)
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- Synthesis and characterization of CoS2 nanostructures via hydrothermal method
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CoS2 nanostructures were synthesized successfully via hydrothermal approach with new precursor. The products were characterized with X-ray diffraction and scanning electron microscopy. The effect of different sulfur sources were investigated on
- Salavati-Niasari, Masoud,Sabet, Mohammad,Esmaeili, Elaheh
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p. 1159 - 1167
(2015/04/14)
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- A facile template-free approach for the solid-phase synthesis of CoS2 nanocrystals and their enhanced storage energy in supercapacitors
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Sphere-like CoS2 nanocrystals (NCs) with porous surfaces were prepared by a modified molten-salt synthesis (MSS) method under mild reaction conditions. Thiourea was used as a reactant, flux and structure-directing agent in the synthesis of CoS2 NCs, which led to mild reaction conditions, pure product and a porous spherical surface. The increase of reaction temperature and molar ratio of cobalt nitrate to thiourea results in larger CoS2 NCs and the change of their morphologies from spheroidal to angular. The synthesis mechanism of CoS2 nanocrystals includes three steps which are the formation of sphere-like CoS2 NCs at the early reaction stage, the formation of a porous structure on the CoS2 NC surface and the aggregation of NCs. The specific surface area of CoS2 NC electrodes reached 29.30 m2 g-1 which results in a specific capacitance as high as 654 F g-1. These results demonstrate that CoS2 NCs can be produced on a large scale through a simple solid-phase synthesis pathway and that they will be a promising electrode material for supercapacitors. This journal is
- Ji, Ying,Liu, Xiaoyang,Liu, Wei,Wang, Ying,Zhang, Hongdan,Yang, Min,Wang, Xiaofeng,Zhao, Xudong,Feng, Shouhua
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p. 50220 - 50225
(2014/12/10)
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