- Modulating Single-Atom Palladium Sites with Copper for Enhanced Ambient Ammonia Electrosynthesis
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The electrochemical reduction of N2 to NH3 is emerging as a promising alternative for sustainable and distributed production of NH3. However, the development has been impeded by difficulties in N2 adsorption, protonation of *NN, and inhibition of competing hydrogen evolution. To address the issues, we design a catalyst with diatomic Pd-Cu sites on N-doped carbon by modulation of single-atom Pd sites with Cu. The introduction of Cu not only shifts the partial density of states of Pd toward the Fermi level but also promotes the d-2π* coupling between Pd and adsorbed N2, leading to enhanced chemisorption and activated protonation of N2, and suppressed hydrogen evolution. As a result, the catalyst achieves a high Faradaic efficiency of 24.8±0.8 % and a desirable NH3 yield rate of 69.2±2.5 μg h?1 mgcat.?1, far outperforming the individual single-atom Pd catalyst. This work paves a pathway of engineering single-atom-based electrocatalysts for enhanced ammonia electrosynthesis.
- Cheng, Hao,Han, Lili,Lin, Lili,Liu, Xijun,Luo, Jun,Ou, Pengfei,Ren, Zhouhong,Rui, Ning,Song, Jun,Sun, Jiaqiang,Xin, Huolin L.,Zhuo, Longchao
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- Efficient electrochemical reduction of nitrate to nitrogen on tin cathode at very high cathodic potentials
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The electrochemical reduction of nitrate on tin cathode at very high cathodic potentials was studied in 0.1 M K2SO4, 0.05 M KNO3 electrolyte. A high rate of nitrate reduction (0.206 mmol min-1 cm-2) and a high selectivity (%S) of nitrogen (92%) was obtained at -2.9 V versus Ag/AgCl. The main by-products were ammonia (8%) and nitrite (2O and traces of NO were also detected. As the cathodic potential increases, the %S of nitrogen increases, while that of ammonia displays a maximum at -2.2 V. The %S of nitrite decreases from 65% at -1.8 V to A cathodic corrosion of tin was observed, which was more intensive in the absence of nitrate. At potentials more negative than -2.4 V, small amounts of tin hydride were detected.
- Katsounaros,Ipsakis,Polatides,Kyriacou
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- Synthesis, Pharmacological, and Biological Evaluation of 2-Furoyl-Based MIF-1 Peptidomimetics and the Development of a General-Purpose Model for Allosteric Modulators (ALLOPTML)
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This work describes the synthesis and pharmacological evaluation of 2-furoyl-based Melanostatin (MIF-1) peptidomimetics as dopamine D2 modulating agents. Eight novel peptidomimetics were tested for their ability to enhance the maximal effect of tritiated N-propylapomorphine ([3H]-NPA) at D2 receptors (D2R). In this series, 2-furoyl-l-leucylglycinamide (6a) produced a statistically significant increase in the maximal [3H]-NPA response at 10 pM (11 ± 1%), comparable to the effect of MIF-1 (18 ± 9%) at the same concentration. This result supports previous evidence that the replacement of proline residue by heteroaromatic scaffolds are tolerated at the allosteric binding site of MIF-1. Biological assays performed for peptidomimetic 6a using cortex neurons from 19-day-old Wistar-Kyoto rat embryos suggest that 6a displays no neurotoxicity up to 100 μM. Overall, the pharmacological and toxicological profile and the structural simplicity of 6a makes this peptidomimetic a potential lead compound for further development and optimization, paving the way for the development of novel modulating agents of D2R suitable for the treatment of CNS-related diseases. Additionally, the pharmacological and biological data herein reported, along with >20a000 outcomes of preclinical assays, was used to seek a general model to predict the allosteric modulatory potential of molecular candidates for a myriad of target receptors, organisms, cell lines, and biological activity parameters based on perturbation theory (PT) ideas and machine learning (ML) techniques, abbreviated as ALLOPTML. By doing so, ALLOPTML shows high specificity Sp = 89.2/89.4%, sensitivity Sn = 71.3/72.2%, and accuracy Ac = 86.1%/86.4% in training/validation series, respectively. To the best of our knowledge, ALLOPTML is the first general-purpose chemoinformatic tool using a PTML-based model for the multioutput and multicondition prediction of allosteric compounds, which is expected to save both time and resources during the early drug discovery of allosteric modulators.
- Sampaio-Dias, Ivo E.,Rodríguez-Borges, José E.,Yá?ez-Pérez, Víctor,Arrasate, Sonia,Llorente, Javier,Brea, José M.,Bediaga, Harbil,Vin?, Dolores,Loza, Mariá Isabel,Caaman?, Olga,Garciá-Mera, Xerardo,González-Diáz, Humberto
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- New insight into hydroxyl-mediated NH3 formation on the Rh-CeO2 catalyst surface during catalytic reduction of NO by CO
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Vibrational IR spectra and light-off investigations show that NH3 forms via the “hydrogen down” reaction of adsorbed CO and NO with hydroxyl groups on a CeO2 support during the catalytic reduction of NO by CO. The presence of water in the reaction stream results in a significant increase in NH3 selectivity. This result is due to water-induced hydroxylation promoting NH3 formation and the competitive adsorption of H2O and NO at the same sites, which inhibits the reactivity of NO reduction by NH3.
- Wang, Chengxiong,Xia, Wenzheng,Zhao, Yunkun
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- Cerium and tin oxides anchored onto reduced graphene oxide for selective catalytic reduction of NO with NH3 at low temperatures
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A series of cerium and tin oxides anchored on reduced graphene oxide (CeO2-SnOx/rGO) catalysts are synthesized using a hydrothermal method and their catalytic activities are investigated by selective catalytic reduction (SCR) of NO with NH3 in the temperature range of 120-280 °C. The results indicate that the CeO2-SnOx/rGO catalyst shows high SCR activity and high selectivity to N2 in the temperature range of 120-280 °C. The catalyst with a mass ratio of (Ce + Sn)/GO = 3.9 exhibits NO conversion of about 86% at 160 °C, above 97% NO conversion at temperatures of 200-280 °C and higher than 95% N2 selectivity at 120-280 °C. In addition, the catalyst presents a certain SO2 resistance. It is found that the highly dispersed CeO2 nanoparticles are deposited on the surface of rGO nanosheets, because of the incorporation of Sn4+ into the lattice of CeO2. The mesoporous structures of the CeO2-SnOx/rGO catalyst provides a large specific surface area and more active sites for facilitating the adsorption of reactant species, leading to high SCR activity. More importantly, the synergistic interaction between cerium and tin oxides is responsible for the excellent SCR activity, which results in a higher ratio of Ce3+/(Ce3+ + Ce4+), higher concentrations of surface chemisorbed oxygen and oxygen vacancies, more strong acid sites and stronger acid strength on the surface of the CeSn(3.9)/rGO catalyst.
- Wang, Yanli,Kang, Ying,Ge, Meng,Zhang, Xiu,Zhan, Liang
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- Reduction of nitrate and nitrite ions over Ni-ZnS photocatalyst under visible light irradiation in the presence of a sacrificial reagent
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Ni-doped ZnS photocatalysts (Zn0.999Ni0.001S) with a 2.4 eV energy gap showed activities for the reduction of nitrate and nitrite ions to nitrite, ammonia, and dinitrogen under visible light irradiation (λ > 420 nm) in the presence of methanol as a reducing reagent. The reduction of nitrate ions competed with that of water to form dihydrogen. The concentration of nitrate ions and loading a platinum cocatalyst affected the selectivity for the reduction products of nitrate ions.
- Hamanoi, Osamu,Kudo, Akihiko
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- Boosted electrocatalytic N2 reduction on fluorine-doped SnO2 mesoporous nanosheets
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The development of highly active and durable electrocatalysts toward the N2 reduction reaction (NRR) holds a key to ambient electrocatalytic NH3 synthesis. Herein, fluorine (F)-doped SnO2 mesoporous nanosheets on carbon cloth (F-SnO2/CC) were developed as an efficient NRR electrocatalyst. Benefiting from the combined structural advantages of mesoporous nanosheet structure and F-doping, the F-SnO2/CC exhibited high NRR activity with an NH3 yield of 19.3 μg h-1 mg-1 and a Faradaic efficiency of 8.6% at-0.45 V (vs RHE) in 0.1 M Na2SO4, comparable or even superior to those of most reported NRR electrocatalysts. Density functional theory calculations revealed that the F-doping could readily tailor the electronic structure of SnO2 to render it with improved conductivity and increased positive charge on active Sn sites, leading to the lowered reaction energy barriers and boosted NRR activity.
- Liu, Ya-Ping,Li, Yu-Biao,Zhang, Hu,Chu, Ke
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- Built-in Electric Field Triggered Interfacial Accumulation Effect for Efficient Nitrate Removal at Ultra-Low Concentration and Electroreduction to Ammonia
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A built-in electric field in electrocatalyst can significantly accumulate higher concentration of NO3? ions near electrocatalyst surface region, thus facilitating mass transfer for efficient nitrate removal at ultra-low concentration and electroreduction reaction (NO3RR). A model electrocatalyst is created by stacking CuCl (111) and rutile TiO2 (110) layers together, in which a built-in electric field induced from the electron transfer from TiO2 to CuCl (CuCl_BEF) is successfully formed. This built-in electric field effectively triggers interfacial accumulation of NO3? ions around the electrocatalyst. The electric field also raises the energy of key reaction intermediate *NO to lower the energy barrier of the rate determining step. A NH3 product selectivity of 98.6 %, a low NO2? production of ?1 is achieved, which are all the best among studies reported at 100 mg L?1 of nitrate concentration to date.
- Sun, Wu-Ji,Ji, Hao-Qing,Li, Lan-Xin,Zhang, Hao-Yu,Wang, Zhen-Kang,He, Jing-Hui,Lu, Jian-Mei
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- NO + H2 reaction on Pt(100). Steady state and oscillatory kinetics
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The reaction of NO + H2 on Pt(100) was studied in the 10-6 mbar range between 300 and 800 K with mass spectrometry, work-function measurements, and video LEED. Both multiple steady states and kinetic oscillations were found. The principal reaction products were N2, H2O and NH3, and the activity and selectivity of the reaction were seen to depend on the partial pressure ratio pH(2)/pNO, on the surface temperature, and on the degree of surface reconstruction. Whereas the 1 × 1 surface of Pt was active for both N2 and NH3 formation, a well-annealed hex phase exhibited a low catalytic activity. The occurrence of defects during the 1 × 1 hex transition was shown to lead to enhanced N2 formation. At low pH(2)/pNO ratios, N2 formation was favored, while for large pH(2)/pNO ratios NH3 production was enhanced. Kinetic oscillations, as determined from variations in the N2, H2O and work-function signals, were found between 430 and 445 K.
- Slinko, M.,Fink, T.,Loeher, T.,Madden, H. H.,Lombardo, S. J.,et al.
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- Putting ammonia into a chemically opened fullerene
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We put ammonia into an open-cage fullerene with a 20-membered ring (1) as the orifice and examined the properties of the complex using NMR and MALDI-TOF mass spectroscopy. The proton NMR shows a broad resonance corresponding to endohedral NH3 at δH = -12.3 ppm relative to TMS. This resonance was seen to narrow when a 14N decoupling frequency was applied. MALDI spectroscopy confirmed the presence of both 1 (m/z = 1172) and 1 + NH3 (m/z = 1189), and integrated intensities of MALDI peak trains and NMR resonances indicate an incorporation fraction of 35-50% under our experimental conditions. NMR observations showed a diminished incorporation fraction after 6 months of storage at -10°C, which indicates that ammonia slowly escapes from the open-cage fullerene.
- Whitener Jr., Keith E.,Frunze, Michael,Iwamatsu, Sho-Ichi,Murata, Shizuaki,Cross, R. James,Saunders, Martin
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- Catalytic Cleavage of the Amide Bond in Urea Using a Cobalt(III) Amino-Based Complex
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The urease mimetic activity of CoIII amine complexes with respect to cleavage of urea was explored using SCXRD and spectroscopic techniques. The reaction of [CoIII(tren)Cl2]Cl [tren = tris(2-aminoethyl)amine] with urea results in the formation of an isocyanato complex {[CoIII(tren)(NH3)(NCO)]Cl2} and ammonia, following the cleavage of the amide bond. The reaction progress and the subsequent formation of cleavage products were confirmed by SCXRD analysis of the reactants as well as the products obtained during the reaction. The reaction was found to be pH and temperature dependent, and the reaction conditions were optimized to maximize conversion. The reaction kinetics was followed spectroscopically (1H NMR and UV/Vis), following the decrease in urea concentration or the increase in pH succeeding ammonia formation. A detailed kinetic study revealed an overall second order rate law and kobs was found to be 3.89 × 10–4 m–1 s–1.
- Uprety, Bhawna,Arderne, Charmaine,Bernal, Ivan
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- Ruthenium(III)-aminopolycarboxylato complexes active for the reduction of the N-N bond of hydrazine and phenylhydrazine in aqueous acidic media
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Interactions of hydrazines N2H4X+ (X = H or Ph) with tri-, tetra- and penta-chelated ruthenium(III)-aminopolycarboxylic acid complexes giving the respective monomeric hydrazinium (RuIII-N2H4X+) adducts have been investigated by potentiometry, spectrophotometry and voltammetry in aqueous acidic solution at 25°C. The deprotonation and metal hydrolysis constants of the complexes and their N2H4X+ adducts in 0.1 M Na2SO4 solution were determined. At pH 2.8, the complexes exhibited a quasi-reversible one-electron reduction wave of RuIII→ RuII in sampled dc in the potential range between -0.16 and -0.37 V vs. SCE, while their hydrazinium adducts obtained in situ by adding an excess of N2H4X+ showed an additional two-electron reduction wave assigned to RuIII-N2H4X+ → RuI-N2H4X+ in the potential range of -0.02 to -0.35 V vs. SCE. The species RuI-N2H4X+ on successive decomposition and hydrolysis give one mole of each of NH3, NH2X and ruthenium(III) species. Further, the RuIII-N2H4X+ complexes have been used as electro-catalysts for the reduction of N2H4X+ to NH3 and NH2X at a mercury pool cathode in acidic solutions of pH 1.9 and 2.8. The quantity of ammonia produced in all cases is linear with time. The E1/2 of RuIII-N2H4X+ → RuI-N2H4X+ and the turnover number are correlated with the sigma basicity (∑pKa) of the aminopolycarboxylic acids and the results are discussed in terms of the hydrolytic tendency of the metal, the number of co-ordinating groups and the steric repulsion caused by the increase in size of the aminopolycarboxylic acid. The Royal Society of Chemistry 2000.
- Prakash, Raju,Ramachandraiah, Gadde
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- Vanadia directed synthesis of anatase TiO2 truncated bipyramids with preferential exposure of the reactive {001} facet
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Anatase TiO2 truncated bipyramids that dominantly exposed the reactive {001} facet were hydrothermally synthesized using vanadia as the structure-directing agent. The exposed fraction of the {001} facet approached 53% upon adjusting the V/Ti mo
- Shi, Quanquan,Li, Yong,Zhan, Ensheng,Ta, Na,Shen, Wenjie
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- NiMn mixed oxides with enhanced low-temperature deNOx performance: Insight into the coordinated decoration of MnOx by NiO phase via glycine combustion method
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Herein, a facile glycine combustion method was utilized to prepare a series of Ni and Mn based single/double metal oxides, which were evaluated as catalysts for low temperature selective catalytic reduction of NO with NH3. The NiMn-T samples presented superior catalytic performance especially for NiMn-400, with ～100 % NOx conversion, >85 % N2 selectivity within 90-300 °C, and better SO2 resistance. The superior catalytic activity might be related to the coordination of Ni and Mn, which afforded higher Mn4+/Mnn+ ratio, larger SBET, more suitable acid site amounts and redox capacity. The improved SO2 resistance of NiMn-400 catalyst can be ascribed to the less ammonium (bi)sulfate deposition and metal sulfation. In-situ DRIFTS revealed that the Ni doping could deliver more reactive species (NH2, monodentate nitrite, bidentate nitrate), and the surface acidity is less affected by SO2, which can account for the enhanced low temperature activity and SO2 resistance of the NiMn-400 catalyst.
- Du, Yali,Hou, Benhui,Liu, Jiangning,Liu, Lili,Wu, Xu,Xie, Xianmei
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- Conversions of coordinated ligands by reducing thermolysis of some double complex compounds
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Thermal decomposition of binary complexes [M(NH3) k]x[M'Ln]y (M = Ni, Co; M' = Fe, Cr, Cu; L = CN-, SCN-, C2O42 -) in a hydrogen atmosphere showed conversion of coordinated CN-groups into ammonia and hydrocarbons; SCN-into ammonia, hydrogen sulfide, and hydrocarbons; and C 2O42 - into hydrocarbons and CO2. In all cases, methane prevails in the resulting hydrocarbons; ethylene is the second in relative yield, which however strongly depends on the temperature and combination of the central ions of double complex salts. The yield of ethylene is especially high from the reduction of Co-Fe complexes at 350°C, Co 4-Fe3 complexes at 500°C, Ni3-Fe 2 and Ni3-Cr2 complexes at 350°C. The observed conversions of coordinated groups can be interpreted as arising from the catalytic effect caused by the reduced forms of the central atoms in the binary complexes to the interaction of ligands with hydrogen. Pleiades Publishing, Ltd., 2010.
- Pechenyuk,Domonov,Avedisyan,Ikorskii
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- NH3 formation from N2 and H2 mediated by molecular tri-iron complexes
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Living systems carry out the reduction of N2 to ammonia (NH3) through a series of protonation and electron transfer steps under ambient conditions using the enzyme nitrogenase. In the chemical industry, the Haber–Bosch process hydrogenates N2 but requires high temperatures and pressures. Both processes rely on iron-based catalysts, but molecular iron complexes that promote the formation of NH3 on addition of H2 to N2 have remained difficult to devise. Here, we isolate the tri(iron)bis(nitrido) complex [(Cp′Fe)3(μ3-N)2] (in which Cp′ = η5-1,2,4-(Me3C)3C5H2), which is prepared by reduction of [Cp′Fe(μ-I)]2 under an N2 atmosphere and comprises three iron centres bridged by two μ3-nitrido ligands. In solution, this complex reacts with H2 at ambient temperature (22 °C) and low pressure (1 or 4 bar) to form NH3. In the solid state, it is converted into the tri(iron)bis(imido) species, [(Cp′Fe)3(μ3-NH)2], by addition of H2 (10 bar) through an unusual solid–gas, single-crystal-to-single-crystal transformation. In solution, [(Cp′Fe)3(μ3-NH)2] further reacts with H2 or H+ to form NH3. [Figure not available: see fulltext.].
- Baabe, Dirk,Bontemps, Sébastien,Coppel, Yannick,Freytag, Matthias,Jones, Peter G.,Münster, Katharina,Maron, Laurent,Reiners, Matthias,Rosal, Iker del,Walter, Marc D.,Zaretzke, Marc-Kevin
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- Silica-Assisted Fabrication of N-doped Porous Carbon for Efficient Electrocatalytic Nitrogen Fixation
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Here we demonstrate a silica-assisted strategy for the synthesis of N-doped porous carbon nanoparticles from zeolitic imidazolate framework precursors. As a metal-free electrocatalyst for N2 reduction to NH3 at ambient conditions, such porous carbon shows an improved catalytic performance compared with the counterpart without the assistance of silica, delivering a higher NH3 formation rate of 7.22 μg h?1 mgcat?1 and a Faradic efficiency of 7.42 % in 0.1 M HCl solution. The mesopores involved in the carbon catalyst are supposed to be responsible for the efficient electroreduction of N2.
- Hu, Chao,Liang, Sucen,Bai, Silin,Yang, Juan,Zhang, Xu,Qiu, Jieshan
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- Infrared spectra and molecular dynamics simulations of cis-HONO isomer in an argon matrix
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Temperature dependent infrared spectra of cis-HONO trapped in an argon matrix are presented. All observed cis-HONO fundamental bands appear as doublets in the spectra. Both components of each doublet show reversible temperature broadening. Molecular dynamics simulations of cis-HONO trapping in an argon matrix suggest that the molecule is trapped in a one-atom substitutional cage in solid argon; no evidence of non-equivalent trapping sites was found. Experimental and theoretical results are discussed.
- Talik, Tadeusz,Tokhadze, Konstantin G.,Mielke, Zofia
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- Adsorption and decomposition of hydrazine on Pd(100)
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The adsorption and decomposition of N2H4 on Pd(100) has been studied by measuring the sticking coefficient and by thermal desorption spectroscopy. Well-defined molecular beam dosing has been employed to limit the interaction of hydra
- Dopheide,Schroeter,Zacharias
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- Ammonia formation over Pd/Al2O3 modified with cerium and barium
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We report experimental results for ammonia formation from nitric oxide and either a direct source of hydrogen or from a mixture of carbon monoxide and water over palladium based catalysts. Specifically, the addition of barium or cerium into an alumina supported palladium sample was studied. Static and transient flow reactor experiments were performed in order to identify the effects of temperature and the presence of oxygen on the activity for ammonia formation. Modification of Pd/Al2O3 with cerium proved to be beneficial for the activity due mainly to its enhancement of the water-gas-shift reaction, thus providing a higher availability of hydrogen for ammonia formation, but also because it remains active in the presence of slightly oxidizing global conditions when hydrogen is provided directly to the feed. Although the modification of Pd/Al2O3 with barium did not affect the ammonia formation during static conditions, the activity during lean/rich cycling increased. This is important for applications of passive selective catalytic reduction.
- Adams, Emma Catherine,Skoglundh, Magnus,Gabrielsson, P?r,Laurell, Mats,Carlsson, Per-Anders
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- Relayed hyperpolarization from: Para -hydrogen improves the NMR detectability of alcohols
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The detection of alcohols by magnetic resonance techniques is important for their characterization and the monitoring of chemical change. Hyperpolarization processes can make previously inpractical measurements, such as the determination of low concentration intermediates, possible. Here, we investigate the SABRE-Relay method in order to define its key characteristics and improve the resulting 1H NMR signal gains which subsequently approach 103 per proton. We identify optimal amine proton transfer agents for SABRE-Relay and show how catalyst structure influences the outcome. The breadth of the method is revealed by expansion to more complex alcohols and the polarization of heteronuclei.
- Rayner, Peter J.,Tickner, Ben. J.,Iali, Wissam,Fekete, Marianna,Robinson, Alastair D.,Duckett, Simon B.
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- Intramolecular Hydrogen Bonding Facilitates Electrocatalytic Reduction of Nitrite in Aqueous Solutions
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This work reports a combined experimental and computational mechanistic investigation into the electrocatalytic reduction of nitrite to ammonia by a cobalt macrocycle in an aqueous solution. In the presence of a nitrite substrate, the Co(III) precatalyst, [Co(DIM)(NO2)2]+ (DIM = 2,3-dimethyl-1,4,8,11-tetraazacyclotetradeca-1,3-diene), is formed in situ. Cyclic voltammetry and density functional theory (DFT) calculations show that this complex is reduced by two electrons, the first of which is coupled with nitrite ligand loss, to provide the active catalyst. Experimental observations suggest that the key N-O bond cleavage step is facilitated by intramolecular proton transfer from an amine group of the macrocycle to a nitro ligand, as supported by modeling several potential reaction pathways with DFT. These results provide insights into how the combination of a redox active ligand and first-row transition metal can facilitate the multiproton/electron process of nitrite reduction.
- Xu, Song,Kwon, Hyuk-Yong,Ashley, Daniel C.,Chen, Chun-Hsing,Jakubikova, Elena,Smith, Jeremy M.
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- The adsorption of gases on the surface of solid solutions and binary compounds of the GaSb-ZnTe system
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The adsorption of ammonia, carbon monoxide, and oxygen on solid solution and binary compound films of the GaSb-ZnTe system was studied. The mechanism of adsorption and rules governing adsorption processes depending on adsorption conditions and system comp
- Kirovskaya,Novgorodtseva,Vasina
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- Kinetics and mechanism of thermal decomposition of ammonium nitrate and sulfate mixtures
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Fundamental kinetic aspects of the decomposition of mixtures and double salts of ammonium nitrate and ammonium sulfate were studied. The effect of water and sulfuric acid additives on the thermal decomposition rate of ammonium nitrate and sulfate mixtures was examined. The constant of proton exchange between nitric acid and the sulfate anion in molten ammonium nitrate was estimated.
- Kazakov,Ivanova,Kurochkina,Plishkin
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- Iron Porphyrin-based Electrocatalytic Reduction of Nitrite to Ammonia
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Electrocatalytic reduction of nitrite to ammonia has been demonstrated using a water-soluble iron porphyrin as catalyst.
- Barley, Mark H.,Takeuchi, Kenneth,Murphy, W. Rorer,Meyer, Thomas J.
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- Fixation of Molecular Nitrogen in Aqueous Solution Induced by Nitrogen Arc Plasma
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Argon Arc Plasma containing nitrogen gas (nitrogen arc plasma) was directly introduced into water, and a disproportionation reaction of molecular nitrogen took place in aqueous solution to form ammonia, nitrous acid, and nitric acid.The redox reaction of molecular nitrogen is interesting on the chemical evolutionary point of view as a possible route for the formation of ammonia under nonreducing conditions.
- Takasaki, Michiaki,Harada, Kaoru
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- Interaction of nitric oxide with cobalt(II) tetrasulfophthalocyanine
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The interaction of nitric oxide (NO) with cobalt(II) tetrasulfophthalocyanine [Co(II)TSPc]4-) has been studied. Coordination of NO is accompanied by electron transfer from the central metal in [Co(II)TSPc]4-, the resulting complex being represented as [(NO-)Co(III)TSPc]4-. The rate constant for the formation of this species is k(f)-= 142 ± 7 dm3 mol-1 s-1 and an equilibrium constant of 3.0 ± 0.5 x 105 dm3 mol-1 was obtained. When adsorbed to a glassy carbon electrode, [Co (II) TSPc]4- catalyses the oxidation and reduction of NO, with a detection limit of the order of 10-9 mol dm-3. Ammonia and hydroxylamine are some of the reduction products obtained for the reduction of NO on [Co(II)TSPc]4- -modified glassy carbon electrodes. (C) 2000 Elsevier Science Ltd.
- Vilakazi, Sibulelo,Nyokong, Tebello
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- Ti3C2Tx (T = F, OH) MXene nanosheets: Conductive 2D catalysts for ambient electrohydrogenation of N2 to NH3
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The Haber-Bosch process for industrial-scale NH3 production suffers from high energy consumption and serious CO2 emission. Electrochemical N2 reduction is an attractive carbon-neutral alternative for NH3 synthesis but is severely restricted due to N2 activation needing efficient electrocatalysts for the N2 reduction reaction (NRR) under ambient conditions. Here, we report that Ti3C2Tx (T = F, OH) MXene nanosheets act as high-performance 2D NRR electrocatalysts for ambient N2-to-NH3 conversion with excellent selectivity. In 0.1 M HCl, such catalysts achieve a large NH3 yield of 20.4 g h-1 mgcat.-1 and a high faradic efficiency of 9.3% at -0.4 V vs. reversible hydrogen electrode, with high electrochemical and structural stability. Density functional theory calculations reveal that N2 chemisorbed on Ti3C2Tx experiences elongation/weakness of the NN triple bond facilitating its catalytic conversion to NH3 and the distal NRR mechanism is more favorable with the final reaction of ?NH2 to NH3 as the rate-limiting step.
- Zhao, Jinxiu,Zhang, Lei,Xie, Xiao-Ying,Li, Xianghong,Ma, Yongjun,Liu, Qian,Fang, Wei-Hai,Shi, Xifeng,Cui, Ganglong,Sun, Xuping
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- An Iodido-Bridged Dimer of Cubane-Type RuIr3S4 Cluster: Structural Rearrangement to New Octanuclear Core and Catalytic Reduction of Hydrazine
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Nitrogen-fixing enzymes contain octanuclear metal–sulfur clusters at the active site, which are constructed on the basis of combined two cubic M4S3C skeletons. In this study, the dimer of cubane-type RuIr3S4 cluster [{(Cp*Ir)3(μ3-S)4Ru}2(μ2-I)3]I (2: Cp* = η5-C5Me5) was synthesized via oxidation of [(Cp*Ir)3(μ3-S)4(CymRu)] (Cym = η6-p-iPrC6H4Me) with I2 followed by ligand exchange. Two cubane cores are bridged by three iodido ligands in 2, while these cubes are fused into a unique Ru2Ir6S8 framework by 2e-reductuion to give [(Cp*Ir)6Ru2(μ3-S)8][I]2. Addition of excess PhNHNH2 to 2 cleaved the dimer structure to form the hydrazine adduct of single cubane [(Cp*Ir)3(μ3-S)4{RuI(NH2NHPh)2}]I. Reduction of N2H4 with Cp2Co and [HNEt3][BF4] was catalyzed by 2 in much higher rate than disproportionation of N2H4. The molecular structures of all new cluster compounds were characterized by X-ray diffraction studies.
- Seino, Hidetake,Hirata, Keiichi,Arai, Yusuke,Jojo, Risa,Okazaki, Masaaki
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- Synthesis, characterization and reactivity of thiolate-bridged cobalt-iron and ruthenium-iron complexes
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Thiolate-bridged hetero-bimetallic complexes [Cp*M(MeCN)N2S2FeCl][PF6] (2, M = Ru; 3, M = Co, Cp* = η5-C5Me5, N2S2 = N,N'-dimethyl-3,6-diazanonane-1,8-dithiolate) were prepared by self-assembly of dimer [N2S2Fe]2 with mononuclear precursor [Cp*Ru(MeCN)3][PF6] or [Cp*Co(MeCN)3][PF6]2 in the presence of CHCl3 as a chloride donor. Complexes 2 and 3 exhibit obviously different redox behaviors investigated by cyclic voltammetry and spin density distributions supported by DFT calculations. Notably, iron-cobalt complex 3 possesses versatile reactivities that cannot be achieved for complex 2. In the presence of CoCp2, complex 3 can undergo one-electron reduction to generate a stable formally CoIIFeII complex [Cp*CoN2S2FeCl] (4). Besides, the terminal chloride on the iron center in 3 can be removed by dehalogenation agent AgPF6 or exchanged with azide to afford the corresponding complexes [Cp*Co(MeCN)N2S2Fe(MeCN)][PF6]2 (5) and [Cp*Co(MeCN)N2S2Fe(N3)][PF6] (6). In addition, complexes 2, 3 and 4 show distinct catalytic reactivity toward the disproportionation of hydrazine into ammonia. These results may be helpful to understand the vital role of the heterometal in some catalytic transformations promoted by heteromultinuclear complexes.
- Guo, Chao,Su, Linan,Yang, Dawei,Wang, Baomin,Qu, Jingping
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- Graphdiyne Interface Engineering: Highly Active and Selective Ammonia Synthesis
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A freestanding 3D graphdiyne–cobalt nitride (GDY/Co2N) with a highly active and selective interface is fabricated for the electrochemical nitrogen reduction reaction (ECNRR). Density function theory calculations reveal that the interface-bonded GDY contributes an unique p-electronic character to optimally modify the Co-N compound surface bonding, which generates as-observed superior electronic activity for NRR catalysis at the interface region. Experimentally, at atmospheric pressure and room temperature, the electrocatalyst creates a new record of ammonia yield rate (Y (Formula presented.)) and Faradaic efficiency (FE) of 219.72 μg h?1 mgcat.?1 and 58.60 percent, respectively, in acidic conditions, higher than reported electrocatalysts. Such a catalyst is promising to generate new concepts, new knowledge, and new phenomena in electrocatalytic research, driving rapid development in the field of electrocatalysis.
- Chen, Xi,Fang, Yan,Gao, Yang,Huang, Bolong,Hui, Lan,Li, Yongjun,Li, Yuliang,Liu, Yuxin,Wang, Zhongqiang,Xing, Chengyu,Xue, Yurui,Yu, Huidi,Zhang, Chao,Zhang, Danyan
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- Photocatalytic reduction of hydrazine to ammonia catalysed by [RuIII(edta)(H2O)]- complex in a Pt/TiO2 semiconductor particulate system
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The illumination of aqueous suspensions of Pt/TiO2 semicondutor photocatalyst with [RuIII(edta)(H2O)]- led to the reduction of hydrazine to ammonia. Coordination of hydrazine to [RuIII(edta)(H2O)]- lowered the energy barrier significantly for the reduction of hydrazine. The rate controlling step of photocatalytic process was probably a surface chemical step (electron transfer) possibly coupled with adsorption of reactants and desorption of ammonia molecule. A working mechanism involving the formation of a [(RuIII(edta)(N2H5)] species (adsorbed onto TiO2 surface) that underwent two-electron transfer reduction followed by cleavage of the N-N bond of coordinated hydrazine was proposed.
- Chatterjee
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- Reactive Ionic Liquid Enables the Construction of 3D Rh Particles with Nanowire Subunits for Electrocatalytic Nitrogen Reduction
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Until now, the synthesis of Rh particles with unusual three-dimensional (3D) nanostructures is still challenging. A 3D nanostructure enables fast ion/molecule transport and possesses plenty of exposed active surface, and therefore it is of great interest to construct 3D Rh particles catalysts for the N2 reduction reaction (NRR). Herein, we proposed a reactive ionic liquid strategy for fabricating unusual 3D Rh particles with nanowires as the subunits. The ionic liquid n-octylammonium formate simultaneously worked as reaction medium, reductant and template for the successful construction of 3D Rh particles. The as-prepared 3D Rh particles demonstrated excellent activity for electrocatalytic N2 fixation in 0.1 M KOH electrolyte under ambient conditions with a high NH3 yield of 35.58 μg h?1 mgcat. ?1 at ?0.2 V versus reversible hydrogen electrode (RHE), surpassing most of the state-of-the-art noble metal catalysts. Our reactive ionic liquid strategy thus holds great promise for the rational construction of high-performance electrocatalysts toward NRR.
- Chen, Tingting,Hao, Jingcheng,Li, Zhonghao,Liu, Shuai,Ying, Hao
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- REDUCTION OF NITRIC OXIDE BY CARBON MONOXIDE AND WATER IN AN AQUEOUS ALKALINE SOLUTIONS OF HEXARHODIUM HEXADECACARBONYL AND TETRARHODIUM DODECACARBONYL COMPLEXES
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The reduction of nitric oxide to ammonia was examined in an aqueous KOH solution of Rh6(CO)16 or Rh4(CO)12 complex.It is confirmed that the water gas shift reaction is incorporated with this reaction, providing hydrogen for ammonia formation.
- Naito, Shuichi,Tamaru, Kenzi
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- Ligand-field photolysis of [Mo(CN)8]4- in aqueous hydrazine: Trapped Mo(II) intermediate and catalytic disproportionation of hydrazine by cyano-ligated Mo(III,IV) complexes
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The substitutional photolysis of K4[Mo(CN)8] ·2H2O in 98% N2H4·H2O has been investigated in detail. A molybdenum(II) intermediate, K 5[Mo(CN)7]·N2H4, is isolated in the primary stage of the reaction that involves the oxidation of N 2H4 to N2, as evidenced by the analysis of evolving gases. The powder X-ray crystal structure of K5[Mo(CN) 7]·N2H4 indicates the pentagonal bipiramidal geometry of the anion and the presence of N2H4 in proximity to the CN- ligands. The salt is characterized by means of EDS, IR, UV-vis, and EPR spectroscopy as well as cyclic voltammetry measurements. The secondary stages of photolysis, involving the catalytic decomposition of N2H4 into NH3 and N 2, lead to the formation of a molybdenum(IV) complex, [Mo(CN) 4O(NH3)]2-. The monitoring of the amounts of evolving gases combined with UV-vis and EPR spectroscopic measurements at various stages of photolysis indicate that the molybdenum(III,IV) couple is catalytically active. The scheme of the catalytic decomposition of hydrazine is presented and discussed.
- Szklarzewicz, Janusz,Matoga, Dariusz,Klys, Agnieszka,Lasocha, Wieslaw
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- Three-way catalytic reactions on Rh-based catalyst: Effect of Rh/ceria interfaces
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Rh-based catalysts were prepared by various methods and it was found that preparation methods play an important role in metal-support interaction (MSI) control which affects the catalytic performance of catalyst. The results suggest that the catalytic reduction of NO is mainly achieved by C3H6 in exhaust and H2 generated from the water-gas shift reaction as well as the steam reforming of C3H8 and CH4. Concentration of water in reaction stream has a significant influence on the water-gas shift and steam reforming reactions. The removal of C3H6 is accomplished by oxygen-induced oxidation instead of steam reforming reaction. In addition, Rh/ceria interactions promote the formation of active oxygen species and surface oxygen vacancy that respectively favors CO oxidation and NO reduction with a high N2 selectivity. Rh@CeO2 system shows high thermal stability due to Rh/ceria interaction.
- Wang, Chengxiong,Zheng, Tingting,Lu, Jun,Wu, Xiaodong,Hochstadt, Harold,Zhao, Yunkun
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- A thiolate-bridged FeIVFeIV μ-nitrido complex and its hydrogenation reactivity toward ammonia formation
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Iron nitrides are key intermediates in biological nitrogen fixation and the industrial Haber–Bosch process, used to form ammonia from dinitrogen. However, the proposed successive conversion of nitride to ammonia remains elusive. In this regard, the search for well-described multi-iron nitrido model complexes and investigations on controlling their reactivity towards ammonia formation have long been of great challenge and importance. Here we report a well-defined thiolate-bridged FeIVFeIV μ-nitrido complex featuring an uncommon bent Fe–N–Fe moiety. Remarkably, this complex shows excellent reactivity toward hydrogenation with H2 at ambient conditions, forming ammonia in high yield. Combined experimental and computational studies demonstrate that a thiolate-bridged FeIIIFeIII μ-amido complex is a key intermediate, which is generated through an unusual two-electron oxidation of H2. Moreover, ammonia production was also realized by treating this diiron μ-nitride with electrons and water as a proton source. [Figure not available: see fulltext.].
- Chen, Hui,Mei, Tao,Qu, Jingping,Wang, Baomin,Wang, Junhu,Yang, Dawei,Ye, Shengfa,Zhang, Yixin,Zhao, Jinfeng,Zhou, Yuhan
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- A highly active defect engineered Cl-doped carbon catalyst for the N2reduction reaction
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eNRR is a promisingly environment-friendly strategy to obtain ammonia under ambient conditions. For metal-based catalysts, the competitive adsorption of H+over N2remains the primary hurdle for high ammonia yield and faradaic efficiency. Carbon-based metal-free catalysts attract our attention for the potential of being promising NRR catalysts due to their natural low HER activity. In this study, we prepared a modified Zn-based metal-organic framework (Zn-BTC) decorated with Cl ions by simply adding NaCl in the synthetic process. The existence of Cl ions in the framework contributes to the generation of large pores during thermolysis. Moreover, -Cl and -COCl species were formedin situand connected with carbon atoms in the defect area. Benefitting from such a structure, this catalyst achieves a high ammonia yield rate of 103.96 μg h?1mgcat?1and a faradaic efficiency of 21.71% at room temperature. Theoretical results also proved that the newly produced -COCl and -Cl functional groups could attract more electrons from adjacent carbon atoms due to their stronger electronegativity, thus improving its affinity towards N2while lowering the HER activity as reactive sites.
- Huang, Minxue,Gong, Shipeng,Wang, Sini,Yang, Kang,Chen, Shi,Wang, Changlai,Kong, Xiangkai,Chen, Qianwang
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supporting information
p. 5807 - 5814
(2021/03/16)
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- Boosting the Electrocatalytic Conversion of Nitrogen to Ammonia on Metal-Phthalocyanine-Based Two-Dimensional Conjugated Covalent Organic Frameworks
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The electrochemical N2 reduction reaction (NRR) under ambient conditions is attractive in replacing the current Haber-Bosch process toward sustainable ammonia production. Metal-heteroatom-doped carbon-rich materials have emerged as the most promising NRR electrocatalysts. However, simultaneously boosting their NRR activity and selectivity remains a grand challenge, while the principle for precisely tailoring the active sites has been elusive. Herein, we report the first case of crystalline two-dimensional conjugated covalent organic frameworks (2D c-COFs) incorporated with M-N4-C centers as novel, defined, and effective catalysts, achieving simultaneously enhanced activity and selectivity of electrocatalytic NRR to ammonia. Such 2D c-COFs are synthesized based on metal-phthalocyanine (M = Fe, Co, Ni, Mn, Zn, and Cu) and pyrene units bonded by pyrazine linkages. Significantly, the 2D c-COFs with Fe-N4-C center exhibit higher ammonia yield rate (33.6 μg h-1 mgcat-1) and Faradaic efficiency (FE, 31.9%) at -0.1 V vs reversible hydrogen electrode than those with other M-N4-C centers, making them among the best NRR electrocatalysts (yield rate >30 μg h-1 mgcat-1 and FE > 30%). In situ X-ray absorption spectroscopy, Raman spectroelectrochemistry, and theoretical calculations unveil that Fe-N4-C centers act as catalytic sites. They show a unique electronic structure with localized electronic states at Fermi level, allowing for stronger interaction with N2 and thus faster N2 activation and NRR kinetics than other M-N4-C centers. Our work opens the possibility of developing metal-nitrogen-doped carbon-rich 2D c-COFs as superior NRR electrocatalyst and provides an atomic understanding of the NRR process on M-Nx-C based electrocatalysts for designing high-performance NRR catalysts.
- Zhong, Haixia,Wang, Mingchao,Ghorbani-Asl, Mahdi,Zhang, Jichao,Ly, Khoa Hoang,Liao, Zhongquan,Chen, Guangbo,Wei, Yidan,Biswal, Bishnu P.,Zschech, Ehrenfried,Weidinger, Inez M.,Krasheninnikov, Arkady V.,Dong, Renhao,Feng, Xinliang
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supporting information
p. 19992 - 20000
(2021/11/30)
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- Electrocatalytic nitrate reduction with Co-based catalysts: comparison of DIM, TIM and cyclam ligands
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Over the past century, the global concentration of environmental nitrate has increased significantly from human activity, which has resulted in the contamination of drinking water and aquatic hypoxia around the world, so the development of effective nitrate-reducing agents is urgent. This work compares three potential macrocycle-based nitrate reduction electrocatalysts: [Co(DIM)]3+, [Co(cyclam)]3+and [Co(TIM)]3+. Although all three complexes have similar structures, only [Co(DIM)]3+has been experimentally determined to be an active electrocatalyst for selective nitrate reduction to produce ammonia in water. While [Co(cyclam)]3+can reduce aqueous nitrate to ammonia and hydroxylamine at heavy metal electrodes, [Co(TIM)]3+is inactive for the reduction of nitrate. As an initial step to understanding what structural and electronic properties are important for efficient electrocatalysts for nitrate reduction, density functional theory (DFT) was employed to investigate the electronic structure of the three Co complexes, with the reduction potentials calibrated to experimental results. Moreover, DFT was employed to explore four different reaction mechanisms for the first steps of nitrate reduction. The calculated reaction barriers reveal how a combination of electron transfer in a redox non-innocent complex, substrate binding, and intramolecular hydrogen bonding dictates the activity of Co-based catalysts toward nitrate reduction.
- Braley, Sarah E.,Jakubikova, Elena,Kwon, Hyuk-Yong,Madriaga, Jose P.,Smith, Jeremy M.
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supporting information
p. 12324 - 12331
(2021/09/20)
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- Cobalt phosphide nanorings towards efficient electrocatalytic nitrate reduction to ammonia
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High-quality CoP nanorings (CoP NRs) are easily achieved using a phosphorating treatment of CoOOH nanorings, and reveal high activity towards the hydrogen evolution reaction and the nitrate electrocatalytic reduction reaction due to substantial coordinately unsaturated active sites, a high surface area, and available mass transfer pathways. Consequently, the CoP NRs can achieve a faradaic efficiency of 97.1% towards NO3?-to-NH3conversion and provide an NH3yield of 30.1 mg h?1mg?1catat a ?0.5 V potential.
- Hong, Qing-Ling,Zhou, Jia,Zhai, Quan-Guo,Jiang, Yu-Cheng,Hu, Man-Cheng,Xiao, Xue,Li, Shu-Ni,Chen, Yu
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supporting information
p. 11621 - 11624
(2021/11/12)
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- Synthesis, Structures, and Reactivities of Iron Complexes Bearing an Isoindoline-Based, Polyprotic Pincer-Type Pyrazole Ligand
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The synthesis and properties of polyprotic NNN pincer-type bis(pyrazole) iron complexes derived from a 1,3-bis(pyrazol-3-ylimino)isoindoline 1 were investigated. When 1 was treated with iron(II) chloride, the paramagnetic, square-pyramidal complex [FeCl2(LH3)] (2; LH3=3-(5-tert-butylpyrazol-3-ylamino)-1-(5-tert-butylpyrazol-3-ylimino)-1H-isoindole) was obtained. Reaction of 2 with two equiv. of silver triflate followed by addition of two equiv. of trimethylphosphine yielded the diamagnetic, octahedral complex [Fe(OTf)(PMe3)2(LH3)]OTf (3), which was converted to the carbonyl complex [Fe(CO)(PMe3)2(LH3)](OTf)2 (4). Treatment of 4 with triethylamine led to deprotonation of the chelate backbone to give the isoindolin-2-yl complex [Fe(CO)(PMe3)2(LH2)]OTf (5). The structures of the LH3 and LH2 ligands were compared in details. The NH groups in the pincer ligand in 2–5 are accompanied by hydrogen bonds, showing their Br?nsted acidic nature. In addition, 3 catalyzed disproportionation of hydrazine, although the catalytic activity was lower than that of a related pyridine-based pincer complex 6 a.
- Toda, Tatsuro,Kuwata, Shigeki
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p. 1471 - 1477
(2021/05/21)
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- A tuned Lewis acidic catalyst guided by hard-soft acid-base theory to promote N2electroreduction
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The electrocatalytic N2reduction reaction (NRR) to ammonia (NH3) driven by intermittent renewable electricity under ambient conditions offers an alternative to the energy-intensive Haber-Bosch process. However, as a distinct core of the process, the design strategy of the electrocatalyst for enhancing the N2activation ability is still in a trial-and-error stage due to the absence of theoretical guidance. As a result, the corresponding NH3yield rate and selectivity are much lower than that required for implementation at scale. In this work, on the basis of the hard-soft acid-base theory, we report a paradigm for the design of an electrocatalyst with tuned Lewis acidity to efficiently activate and reduce N2to NH3. As a proof of concept, it is revealed that enhancing the Lewis acidity of the molybdenum sulfide (MoSx) model catalyst supported on carbon nanotubes can greatly improve its activation ability toward the N2molecule. Accordingly, a high faradaic efficiency of 21.60 ± 2.35% and NH3yield rate of 40.4 ± 3.6 μg h?1mgcat.?1are obtained over the modified MoSx, which are ～2 times enhanced in comparison with the original MoSx, respectively. Density functional theory calculations verify that the electron transfer from the occupied σ orbitals of N2to the empty d orbitals of Mo sites within MoSxcan be greatly accelerated by tuning the Lewis acidity of MoSxto match with the basicity of N2, thereby enhancing the N2activation processviathe σ → d donation mechanism.
- Ding, Yiwang,Hong, Jiafu,Qiu, Jieshan,Ren, Yongwen,Song, Xuedan,Tan, Xinyi,Wei, Qianbing,Yu, Chang,Zhou, Fengyi
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supporting information
p. 13036 - 13043
(2021/06/16)
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- Trinuclear nickel(II) amino acid Schiff base complex containing phenolato and acetato bridges: Structural and functional resemblance of urease
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A novel phenolato and acetato bridged trinuclear Ni(II) complex [Ni3L2] was synthesized by the reaction between the amino acid Schiff base, N-o-vanillylidene-L-histidine(L) and Ni(OAc)2·2H2O. Single crystal X-ray analysis reveals that the trinuclear structure of Ni3L2 is built by linking two terminal NiN2O4 cores with one NiO6 centre core (NiN2O4?NiO6?NiN2O4) and each Ni(II) ion exists in an octahedral environment. Variable-temperature magnetic susceptibility data represent the antiferromagnetic interactions of the Ni3L2 mediated by a single Ni-O-Ni bridge. The bond length and bond angles around each terminal nickel centre match the nickel centre in urease enzyme of native bacteria Klebsiella aerogenes, Bacillus pasteurii and Helicobacter pylori. The catalytic activity of Ni3L2 on the hydrolysis of urea into ammonia and carbon dioxide was established by the absorption spectral method. The urea binding propensity of the nickel complex Ni3L2 was compared with jack bean urease by using molecular docking studies.
- Thalamuthu,Neelakantan
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- Rapid in situ synthesis of MgAl-LDH on η-Al2O3 for efficient hydrolysis of urea in wastewater
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A rapid and efficient synthesis strategy of MgAl-LDH was proposed. MgAl-LDH with high specific surface area was synthesized in situ by using η-Al2O3 as carrier, and the synthesis time was greatly shortened by both increasing temperature and introducing ethanol as co-solvent. Besides, the growth process of MgAl-LDH on the surface of η-Al2O3 is also revealed. Under optimized conditions, the specific surface area of the MgAl-LDH is as high as 172.4 m2/g, the crystalline size is as small as 12.82 nm, and the basicity can reach 1.795 mmol/g. The urea wastewater was degraded from 8000 mg/L to 6.85 mg/L over the catalyst synthesized by the rapid method, and the catalyst still maintains high activity after four uses. Also, it was found that there is a good linear relationship between the urea removal rate and the basicity of MgAl-LDH.
- Guo, Chenyuan,Shen, Shuguang,Li, Meina,Wang, Ying,Li, Jing,Xing, Yuanquan,Wang, Cui,Pan, Huajie
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- Unveiling the urease like intrinsic catalytic activities of two dinuclear nickel complexes towards thein situsyntheses of aminocyanopyridines
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Designing metal complexes as functional models for metalloenzymes remains one of the main targets in synthetic bioinorganic chemistry. Furthermore, the utilization of the product(s) derived from the catalytic reaction for subsequent organic transformation
- Kundu, Bidyut Kumar,Pragti,Biswas, Soumen,Mondal, Abhijit,Mazumdar, Shyamalava,Mobin, Shaikh M.,Mukhopadhyay, Suman
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p. 4848 - 4858
(2021/04/22)
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- Integrated selective nitrite reduction to ammonia with tetrahydroisoquinoline semi-dehydrogenation over a vacancy-rich Ni bifunctional electrode
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The development of efficient electrocatalysts for nitrite reduction to ammonia, especially integrated with a value-added anodic reaction, is important. Herein, Ni nanosheet arrays with Ni vacancies (Ni-NSA-VNi) were demonstrated to exhibit outstanding electrocatalytic performances toward selective nitrite reduction to ammonia (faradaic efficiency: 88.9%; selectivity: 77.2%) and semi-dehydrogenation of tetrahydroisoquinolines (faradaic efficiency: 95.5%; selectivity: 98.0%). The origin and quantitative analyses of ammonia were performed by 15N isotope labeling and 1H NMR experiments. The decrease in electronic cloud density induced by the Ni vacancies was found to improve the NO2- adsorption and NH3 desorption, leading to high nitrite-to-ammonia performance. In situ Raman results revealed the formation of NiII/NiIII active species for anodic semi-dehydrogenation of tetrahydroisoquinolines on Ni-NSA-VNi. Importantly, a Ni-NSA-VNi Ni-NSA-VNi bifunctional two-electrode electrolyzer was constructed to simultaneously produce ammonia and dihydroisoquinoline with robust stability and high selectivity.
- Wang, Changhong,Zhou, Wei,Sun, Zhaojun,Wang, Yuting,Zhang, Bin,Yu, Yifu
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supporting information
p. 239 - 243
(2021/01/15)
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- Schottky Barrier-Induced Surface Electric Field Boosts Universal Reduction of NOx? in Water to Ammonia
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NOx? reduction acts a pivotal part in sustaining globally balanced nitrogen cycle and restoring ecological environment, ammonia (NH3) is an excellent energy carrier and the most valuable product among all the products of NOx? reduction reaction, the selectivity of which is far from satisfaction due to the intrinsic complexity of multiple-electron NOx?-to-NH3 process. Here, we utilize the Schottky barrier-induced surface electric field, by the construction of high density of electron-deficient Ni nanoparticles inside nitrogen-rich carbons, to facilitate the enrichment and fixation of all NOx? anions on the electrode surface, including NO3? and NO2?, and thus ensure the final selectivity to NH3. Both theoretical and experimental results demonstrate that NOx? anions were continuously captured by the electrode with largely enhanced surface electric field, providing excellent Faradaic efficiency of 99 % from both electrocatalytic NO3? and NO2? reduction. Remarkably, the NH3 yield rate could reach the maximum of 25.1 mg h?1 cm?2 in electrocatalytic NO2? reduction reaction, outperforming the maximum in the literature by a factor of 6.3 in neutral solution. With the universality of our electrocatalyst, all sorts of available electrolytes containing NOx? pollutants, including seawater or wastewater, could be directly used for ammonia production in potential through sustainable electrochemical technology.
- Chen, Jie-Sheng,Gao, Peng,Li, Qi-Yuan,Li, Xin-Hao,Xu, Dong,Xue, Zhong-Hua,Zhai, Guang-Yao,Zhang, Shi-Nan
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p. 20711 - 20716
(2021/08/25)
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- The highly efficient removal of HCN over Cu8Mn2/CeO2catalytic material
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In this work, porous CeO2flower-like spheres loaded with bimetal oxides were prepared to achieve effective removal of HCN in the lower temperature region of 30-150 °C. Among all samples, the CeO2loaded with copper and manganese oxide
- Yi, Zhihao,Sun, Jie,Li, Jigang,Yang, Yulin,Zhou, Tian,Wei, Shouping,Zhu, Anna
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p. 8886 - 8896
(2021/03/06)
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- Visible light enables catalytic formation of weak chemical bonds with molecular hydrogen
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The synthesis of weak chemical bonds at or near thermodynamic potential is a fundamental challenge in chemistry, with applications ranging from catalysis to biology to energy science. Proton-coupled electron transfer using molecular hydrogen is an attractive strategy for synthesizing weak element–hydrogen bonds, but the intrinsic thermodynamics presents a challenge for reactivity. Here we describe the direct photocatalytic synthesis of extremely weak element–hydrogen bonds of metal amido and metal imido complexes, as well as organic compounds with bond dissociation free energies as low as 31 kcal mol?1. Key to this approach is the bifunctional behaviour of the chromophoric iridium hydride photocatalyst. Activation of molecular hydrogen occurs in the ground state and the resulting iridium hydride harvests visible light to enable spontaneous formation of weak chemical bonds near thermodynamic potential with no by-products. Photophysical and mechanistic studies corroborate radical-based reaction pathways and highlight the uniqueness of this photodriven approach in promoting new catalytic chemistry. [Figure not available: see fulltext.].
- Park, Yoonsu,Kim, Sangmin,Tian, Lei,Zhong, Hongyu,Scholes, Gregory D.,Chirik, Paul J.
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p. 969 - 976
(2021/07/25)
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- Ammonia Formation Catalyzed by a Dinitrogen-Bridged Dirhenium Complex Bearing PNP-Pincer Ligands under Mild Reaction Conditions**
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A series of rhenium complexes bearing a pyridine-based PNP-type pincer ligand are synthesized from rhenium phosphine complexes as precursors. A dinitrogen-bridged dirhenium complex bearing the PNP-type pincer ligands catalytically converts dinitrogen into ammonia during the reaction with KC8 as a reductant and [HPCy3]BArF4 (Cy=cyclohexyl, ArF=3,5-(CF3)2C6H3) as a proton source at ?78 °C to afford 8.4 equiv of ammonia based on the rhenium atom of the catalyst. The rhenium-dinitrogen complex also catalyzes silylation of dinitrogen in the reaction with KC8 as a reductant and Me3SiCl as a silylating reagent under ambient reaction conditions to afford 11.7 equiv of tris(trimethylsilyl)amine based on the rhenium atom of the catalyst. These results demonstrate the first successful example of catalytic nitrogen fixation under mild reaction conditions using rhenium-dinitrogen complexes as catalysts.
- Egi, Akihito,Kuriyama, Shogo,Meng, Fanqiang,Nishibayashi, Yoshiaki,Tanaka, Hiromasa,Yoshizawa, Kazunari
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supporting information
p. 13906 - 13912
(2021/05/13)
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- Oxygen Vacancies of CeO2Nanospheres by Mn-Doping: An Efficient Electrocatalyst for N2Reduction under Ambient Conditions
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The electrochemical N2 reduction reaction (NRR) demonstrates a process of NH3 synthesis from N2 molecules under ambient conditions, which is environmentally friendly and recyclable. However, it requires an efficient electrocatalyst to activate inert N2 molecules, which is still difficult to satisfy. Recently, as an active NRR electrocatalyst and a typical metal oxide, CeO2 has featured ultrahigh thermal stability and the ability to apply heteroatom doping, which is an imperative approach importing oxygen vacancy by replacing metal ions with selective elements to greatly influence the activity of catalysts. Here, we analyze the unique properties of manganese dopants in modulating the activity of CeO2 nanospheres for NRR. It attains a larger NH3 yield of 27.79 μg h-1 mgcat-1 and a higher Faradaic efficiency of 9.1% than pure CeO2 at -0.30 V in 0.1 M HCl, with high electrochemical and structure stability. With calculations by density functional theory, the performance enhancement of Mn-doped CeO2 is also proved mathematically.
- Cheng, Wendong,Ji, Yuyao,Li, Chengbo,Liu, Xingquan
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supporting information
(2022/01/14)
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- Single-atom metal-N4site molecular electrocatalysts for ambient nitrogen reduction
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Electrochemical N2reduction to NH3is an emerging energy technology, attracting much attention due to its features of mild reaction conditions and being non-polluting. In this work, we demonstrate that a well-defined cobalt tetraphenylporphyrin (CoTPP) molecule as a model catalyst exhibits good electrocatalytic nitrogen reduction activity in 0.1 M HCl electrolyte with an ammonia yield of 15.18 ± 0.78 μg h-1mg-1cat.calculated by the indophenol blue method and a Faraday efficiency (FE) of 11.43 ± 0.74%. The catalyst also has satisfactory electrolytic stability and recycling test reusability. The activity displayed by the porphyrin molecular catalysts is attributed to the full exposure of the metal-N4sites. To trace the source of ammonia, an isotope labeling experiment (15N2as the feed gas) is used to calculate the ammonia yieldvia1H nuclear magnetic resonance (NMR), which is close to that of the indophenol blue method. In addition, we replace the central metal to prepare CuTPP and MnTPP, and they also show electrocatalytic nitrogen reduction reaction (NRR) ability. This work proves the feasibility and versatility of using metalloporphyrin molecules as model electrocatalysts for NRR and offers a new strategy for the further development of molecular NRR catalysts.
- Sun, Sai,Yang, Xiaoxuan,Li, Siqi,Chen, Xinyu,Li, Ke,Lv, Jiaqi,Wang, Wenwen,Cheng, Dongming,Wang, Yong-Hui,Zang, Hong-Ying
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p. 2589 - 2596
(2021/04/22)
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- Unveiling the genesis of the high catalytic activity in nickel phthalocyanine for electrochemical ammonia synthesis
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Electrochemical ammonia synthesis by the nitrogen reduction reaction (NRR) using an economically efficient electrocatalyst can provide a substitute for the Haber-Bosch process. However, identification of active sites responsible for the origin of catalytic activity in transition metal phthalocyanine is a difficult task due to its complex structure. Herein, density functional theory (DFT) is applied to identify the probable active sites of nickel phthalocyanine (NiPc) for the NRR as well as the origin of catalytic activity which is associated with the d band center and density of states (DOS) of Ni in NiPc. Accordingly, NiPc nanorods (NRs), synthesized by a solvothermal method in large scale, exhibit an NH3yield rate about 85 μg h?1mgcat?1and a faradaic efficiency (FE) of 25% at ?0.3 Vvs.RHE. Moreover, the catalyst shows long term stability up to 30 hours while maintaining the NH3yield and FE. The isotopic labelling experiment and other control investigation led to validation of the nitrogen source in NH3formation. This study provides brand new insightful understanding of the active sites and the origin of the catalytic activity of NiPc for their NRR applications.
- Bhattacharyya, Dibyendu,Chattopadhyay, Santanu,Ghorai, Uttam Kumar,Jha, Shambhu N.,Kapse, Samadhan,Murmu, Shyamal,N., Abharana,Paul, Sourav,Thapa, Ranjit
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p. 14477 - 14484
(2021/07/02)
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- Efficient N2reduction with the VS2electrocatalyst: Identifying the active sites and unraveling the reaction pathway
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The electrochemical nitrogen reduction reaction (NRR) is an effective method for sustainable production of NH3. However, a robust NRR electrocatalyst is predominantly required in order to activate the inert N2 molecule. In this article, we report the synthesis of flower-like VS2 (FL-VS2) as a high-performance NRR electrocatalyst. FL-VS2 shows the highest NH3 yield of 34.62 μg h-1 mgcat-1 with a faradaic efficiency (FE) of 2.09%, which is higher than that of the counterparts. By using first-principles calculations, we identify that the S edge site and V edge site of VS2 easily chemisorb H+ and N2, respectively. A typical poisoning experiment verifies that the V site at the edge of FL-VS2 is the active site for the NRR. The conversion of N2 to NH3 is more inclined to follow a hybrid pathway at the VS2 electrocatalyst. This research not only provides an efficient electrocatalyst for the NRR, but also offers theoretical support for identifying the active sites and reaction mechanism of the NRR on transition metal dihalide-based materials.
- Chi, Xinyue,Li, Cheng,Wang, Huaizhi,Wang, Xiaoxuan,Xiong, Yuanyuan,Yan, Yi-Ming,Yang, Zhiyu,Zhao, Liang,Zhao, Rui,Zhao, Yufei,Zhou, Yixiang
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supporting information
p. 24985 - 24992
(2021/11/27)
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- Atomic defects in pothole-rich two-dimensional copper nanoplates triggering enhanced electrocatalytic selective nitrate-to-ammonia transformation
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The development of efficient catalysts for electrocatalytic selective conversion of nitrate pollutants into valuable ammonia is a project of far-reaching importance. This work demonstrated thein situelectroreduction of pre-synthesized CuO nanoplates into defect-rich metallic Cu nanoplates and evaluated their electrocatalytic nitrate-to-ammonia activity. Concentrated atomic defects in the as-converted Cu nanoplates could favor the adsorption, enrichment and confinement of nitrate ions and pivotal reaction intermediates, selectively promoting eight-electron reduction (NH3formation). Consequently, the resultant defect-rich Cu nanoplates exhibit a significant ammonia production rate of 781.25 μg h?1mg?1, together with excellent nitrate conversion (93.26%), high ammonia selectivity (81.99%) and good electrocatalytic stability, superior to the defect-free Cu nanoplate counterpart. Isotope labelling experiments demonstrated that the source of ammonia was from nitrate. Both1H NMR and colorimetric methods were used to quantify the ammonia yield.
- Li, Xiaonian,Liu, Mengying,Ren, Kaili,Ren, Tianlun,Wang, Hongjing,Wang, Liang,Wang, Mingzhen,Wang, Ziqiang,Xu, You
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supporting information
p. 16411 - 16417
(2021/08/09)
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- Total Synthesis of Laucysteinamide A, a Monomeric Congener of Somocystinamide A
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Laucysteinamide A (4) is a marine natural product isolated from the cyanobacterium Caldora penicillata and contains structural motifs found in promising cancer drug leads. The first total synthesis of 4 and its analogues was achieved, which also enabled a concise formal synthesis of somocystinamide A (3), a dimeric congener of 4 that previously showed extremely potent antiproliferative activities. This work provides further insights on structure-activity relationships in this class of natural products.
- Taylor, Kimberly S.,Zhang, Chen,Glukhov, Evgenia,Gerwick, William H.,Suyama, Takashi L.
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p. 865 - 870
(2021/04/02)
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- Sequentially prepared Mo-V-Based SCR catalyst for simultaneous Hg0 oxidation and NO reduction
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Molybdenum (Mo)-vanadium (V)-based selective catalytic reduction (SCR) catalyst synthesized by the sequential impregnation of Mo and W followed by V was investigated for simultaneous elemental mercury (Hg0) oxidation and nitrogen oxide (NO) red
- Li, Can,Sriram, Vishnu,Liu, Zhouyang,Brewe, Dale,Lee, Joo-Youp
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- High-Performance Electrochemical NO Reduction into NH3 by MoS2 Nanosheet
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Electrochemical reduction of NO not only offers an attractive alternative to the Haber–Bosch process for ambient NH3 production but mitigates the human-caused unbalance of nitrogen cycle. Herein, we report that MoS2 nanosheet on graphite felt (MoS2/GF) acts as an efficient and robust 3D electrocatalyst for NO-to-NH3 conversion. In acidic electrolyte, such MoS2/GF attains a maximal Faradaic efficiency of 76.6 % and a large NH3 yield of up to 99.6 μmol cm?2 h?1. Using MoS2 nanosheet-loaded carbon paper as the cathode, a proof-of-concept device of Zn-NO battery was assembled to deliver a discharge power density of 1.04 mW cm?2 and an NH3 yield of 411.8 μg h?1 mgcat.?1. Calculations reveal that the positively charged Mo-edge sites facilitate NO adsorption/activation via an acceptance–donation mechanism and disfavor the binding of protons and the coupling of N?N bond.
- Alshehri, Abdulmohsen Ali,Gao, Shuyan,Guo, Xiaodong,Li, Na,Li, Tingshuai,Liang, Jie,Lin, Yiting,Liu, Qian,Liu, Yang,Luo, Yonglan,Ma, Dongwei,Mou, Ting,Sun, Xuping,Tang, Bo,Wang, Yuanyuan,Yue, Luchao,Zhang, Longcheng
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supporting information
p. 25263 - 25268
(2021/11/01)
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- Rational design of bimetallic Rh0.6Ru0.4nanoalloys for enhanced nitrogen reduction electrocatalysis under mild conditions
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As a carbon-free reaction process, the electrocatalytic nitrogen reduction reaction (eNRR) under mild conditions has broad prospects for green and sustainable NH3 production. In this work, bimetallic RhRu nanoalloys (NAs) with cross-linked curly nanosheets were successfully prepared and exhibited exciting results in the eNRR process. Furthermore, the composition effect of RhRu NAs on eNRR activity was studied systematically, and the results showed that Rh0.6Ru0.4 NAs/CP exhibited the highest NH3 yield rate of 57.75 μg h-1 mgcat.-1 and faradaic efficiency of 3.39%. As an eNRR catalyst with great potential, Rh0.6Ru0.4 NAs extend the possibility of alloy-nanomaterials in the eNRR field and further provide an idea for the precise structure of more effective and stable electrocatalysts.
- Zhao, Lei,Liu, Xuejing,Zhang, Shen,Zhao, Jie,Xu, Xiaolong,Du, Yu,Sun, Xu,Zhang, Nuo,Zhang, Yong,Ren, Xiang,Wei, Qin
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supporting information
p. 259 - 263
(2021/01/14)
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- A shape-memory V3O7·H2O electrocatalyst for foldable N2fixation
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Shape-memory materials can retain their functionalities during mechanical deformation, and thus hold great promise for utilizations in versatile, wearable and portable systems. Here, we report a shape-memory V3O7·H2O monolith that works as a new emerging foldable electrocatalyst for nitrogen reduction reaction (NRR). Remarkably, the electrocatalyst has been designed according to our unexpected observation that metal oxides, commonly considered as a class of tough and brittle materials, can show shape-memory properties after anisotropic alignment of their microstructures via an ice-Templated freeze-casting method. We demonstrate the V3O7·H2O electrocatalyst for promoting the NRR characteristic of excellent performances, including an ammonia yield rate of 36.42 μg h-1 mg-1, faradaic efficiency of 14.20% at-0.55 V (vs. RHE), and operation for seven cycles without activity or structural degradation. Remarkably, NRR faradaic efficiencies do not change during electrode deformations, while ammonia yield rates only show a slight decline even after significant foldings. We further elucidate through density function theory that NRR proceeds at vanadium active sites of V3O7·H2O via the associative distal pathway with ?N2 + H+ → ?N2H as the rate-limiting step. This journal is
- Sun, Yuntong,Ding, Shan,Zhang, Chen,Duan, Jingjing,Chen, Sheng
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p. 1603 - 1609
(2021/02/03)
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- Enhancing electrocatalytic nitrogen reduction to ammonia with rare earths (La, Y, and Sc) on high-index faceted platinum alloy concave nanocubes
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Surface structure effect is the key subject in electrocatalysis, and consists of the structure dependence of interaction between reaction molecules and the catalyst surface in specifying the surface atomic arrangement, chemical composition and electronic structure. Herein, we develop a controllable synthesis of Pt-RE (RE = La, Y, Sc) alloy concave nanocubes (PtRENCs) with {410} high-index facets (HIFs) by an electrochemical method in a choline chloride-urea based deep eutectic solvent. The PtRENCs are used as an efficient catalyst in electrocatalytic nitrogen reduction to ammonia (NH3). Owing to the high density of low-coordinated Pt step sites (HIF structure) and the unique electronic effect of Pt-RE, the as-prepared PtRENCs exhibit an excellent electrocatalytic performance for the nitrogen reduction reaction (NRR) under ambient conditions. The NH3 yield rate and faradaic efficiency (FE) share the same trend of Pt-La (rNH3: 71.4 μg h-1 μgcat-1, FE: 35.6%) > Pt-Y (rNH3: 65.2 μg h-1 μgcat-1, FE: 26.7%) > Pt-Sc (rNH3: 48.5 μg h-1 μgcat-1, FE: 19%) > Pt (rNH3: 25.8 μg h-1 μgcat-1, FE: 10.7%). Moreover, the PtRENCs demonstrate high selectivity for N2 reduction to NH3 and high stability retaining 90% of the NH3 yield rate and FE values after 12 h continuous NRR tests. Density functional theory (DFT) calculations indicate that the rate determining step of the NRR process is the formation of N2H2? from N2 with the transfer of two proton-coupled electrons, and the upshift of the d-band center boosts the NRR activity by enhancing the bonding strength of reaction intermediates on the high-index faceted Pt-RE (RE = La, Y, Sc) alloying surface. In addition, the introduction of RE (RE = La, Y, Sc) on the Pt step surface can effectively suppress the HER process and provide appropriate sites for the NRR. This journal is
- Chen, You-Hu,Jiang, Xin,Liao, Hong-Gang,Liu, Feng,Mao, Yu-Jie,Sheng, Tian,Sun, Shi-Gang,Wei, Lu,Ye, Jin-Yu,Zhao, Xin-Sheng
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p. 26277 - 26285
(2021/12/10)
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- Biochemical Characterization, Phytotoxic Effect and Antimicrobial Activity against Some Phytopathogens of New Gemifloxacin Schiff Base Metal Complexes
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String of Fe(III), Cu(II), Zn(II) and Zr(IV) complexes were synthesized with tetradentateamino Schiff base ligand derived by condensation of ethylene diamine with gemifloxacin. The novel Schiff base (4E,4′E)-4,4′-(ethane-1,2-diyldiazanylylidene)bis{7-[(4Z
- Mohamed, Amira A.,Elshafie, Hazem S.,Sadeek, Sadeek A.,Camele, Ippolito
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- Enhanced N2affinity of 1T-MoS2with a unique pseudo-six-membered ring consisting of N-Li-S-Mo-S-Mo for high ambient ammonia electrosynthesis performance
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The Haber-Bosch process is widely used to convert atmospheric nitrogen (N2) into ammonia (NH3). However, the extreme reaction conditions and abundant carbon released by this process make it important to develop a greener NH3 production method. The electrochemical nitrogen reduction reaction (NRR) is an attractive alternative to the Haber-Bosch process. Herein, we demonstrated that molybdenum sulfide on nickel foil (1T-MoS2-Ni) with low crystallinity was an active NRR electrocatalyst. 1T-MoS2-Ni achieved a high faradaic efficiency of 27.66% for the NRR at -0.3 V (vs. RHE) in a LiClO4 electrolyte. In situ X-ray diffraction and ex situ X-ray photoemission analyses showed that lithium ions were intercalated into the 1T-MoS2 layers during the NRR. Moreover, theoretical calculations revealed the differences between six membered rings formed in the 1T-MoS2 and 2H-MoS2 systems with Li intercalation. The bond distances of d(Mo-N) and d(N-Li) of in Li-1T-MoS2 were found to be shorter than those in Li-2H-MoS2, resulting in a lower energy barrier of N2 fixation and higher NRR activity. Therefore, 1T-MoS2-Ni is promising as a scalable and low-cost NRR electrocatalyst with lower power consumption and carbon emission than the Haber-Bosch process.
- Patil, Shivaraj B.,Chou, Hung-Lung,Chen, Yu-Mei,Hsieh, Shang-Hsien,Chen, Chia-Hao,Chang, Chia-Che,Li, Shin-Ren,Lee, Yi-Cheng,Lin, Ying-Sheng,Li, Hsin,Chang, Yuan Jay,Lai, Ying-Huang,Wang, Di-Yan
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supporting information
p. 1230 - 1239
(2021/01/25)
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- Nitrogen reduction through confined electro-catalysis with carbon nanotube inserted metal-organic frameworks
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Carbon-based nanomaterials are widely used in electro-catalysis because of their low cost, high conductivity and stability. However, their application towards selective electrochemical reduction of nitrogen to ammonia suffers from low activity and faradaic efficiency (FE). Here, we report a confined electrocatalysis strategy for enhanced ammonia production and FE in the electrochemical nitrogen reduction reaction (eNRR), by the construction of a carbon nanotube (CNT or NCNT) inserted porous metal-organic framework (MOF). The CNT/NCNT serves as the catalytic center and ensures an efficient pathway for electron conduction that is essential to electrocatalysis, while the general relative hydrophobicity within the MOF enriches the local concentration of N2 near the catalyst active sites, and more importantly suppresses the hydrogen evolution reaction (HER) to facilitate the FE. Among the systematically screened MOF and carbon nanotubes, NCNT@MIL-101(Fe) demonstrates the highest activity of 607.35 μg h-1 mgNCNT-1 and CNT@MIL-101(Fe) achieves the best FE of 37.28%. The significantly improved NRR performance of CNT@MOFs and NCNT@MOFs demonstrates the successful employment of confined catalysis in electrochemical reactions, which provides an alternative strategy for catalyst design in nitrogen fixation. This journal is
- Lv, Yang,Wang, Yiqi,Yang, Miao,Mu, Zhangyan,Liu, Shengtang,Ding, Weiping,Ding, Mengning
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supporting information
p. 1480 - 1486
(2021/02/03)
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- High-performance ammonia fixation electrocatalyzed by ReS2nanosheet array
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The industrial-scale NH3 production still heavily depends on the Haber-Bosch process, which not only demands high energy consumption but also emits a large amount of CO2. The electrochemical fixation of N2 to NH3 under ambient conditions is regarded as an eco-friendly and sustainable approach, but stable and efficient electrocatalysts are demanded for the N2 reduction reaction under ambient conditions. In this communication, ReS2 nanosheet array on carbon cloth (ReS2/CC) is first utilized in NRR. This ReS2/CC exhibits high catalytic activity and strong long-term electrochemical durability. The Faraday efficiency of ReS2/CC is 0.78% and the NH3 yield of ReS2/CC is 3.61 × 10-10 mol s-1 cm-2 at -0.4 V versus reversible hydrogen electrode in 0.1 M HCl.
- Zhang, Lunwen,Xue, Xiaodong,Gao, Min,Zhao, Jinxiu,Yan, Tao,Yu, Cuiping,Zhao, Lei,Ren, Xiang,Wei, Qin
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supporting information
p. 11457 - 11460
(2021/07/13)
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- Trends in the Series of Ammine Rare-Earth-Metal Borohydrides: Relating Structural and Thermal Properties
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Ammine metal borohydrides display extreme structural and compositional diversity and show potential applications for solid-state hydrogen and ammonia storage and as solid-state electrolytes. Thirty-two new compounds are reported in this work, and trends in the full series of ammine rare-earth-metal borohydrides are discussed. The majority of the rare-earth metals (RE) form trivalent RE(BH4)3·xNH3 (x = 7-1) compounds, which possess an intriguing crystal chemistry changing with the number of ammonia ligands, varying from structures built from complex ions (x = 5-7), to molecular structures (x = 3, 4), one-dimensional chains (x = 2), and structures built from two-dimensional layers (x = 1). Divalent RE(BH4)2·xNH3 (x = 4, 2, 1) compounds are observed for RE2+ = Sm, Eu, Yb, with structures varying from molecular structures (x = 4) to two-dimensional layered (x = 2, 1) and three-dimensional structures (Yb(BH4)2·NH3). The crystal structure and composition of the compounds depend on the volume of the rare-earth ion. In all structures, NH3 coordinates to the metal, while BH4- has a more flexible coordination and is observed as a bridging and terminal ligand and as a counterion. RE(BH4)3·xNH3 (x = 7-5, 4) releases NH3 stepwise during thermal treatment, while mainly H2 is released for x ≤ 3. In contrast, only NH3 is released from RE(BH4)2·xNH3 due to the lower charge density on the RE2+ ion and higher stability of RE(BH4)2. The thermal stability of RE(BH4)3·xNH3 increase with increasing cation charge density for x = 5, 7, while it decreases for x = 4, 6. For x = 3, the thermal stability decreases with increasing charge density, due to the destabilization of the BH4- group, making it more reactive toward NH3. This research provides a large number of novel compounds and new insight into trends in the crystal chemistry of ammine metal borohydrides and reveals a correlation between the local metal coordination and the thermal stability.
- Grinderslev, Jakob B.,Jensen, Torben R.
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p. 2573 - 2589
(2021/02/16)
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- Crystal structure of the high-temperature polymorph of C(NH2)3PbI3 and its thermal decomposition
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The synthesis of guanidinium lead iodide, C(NH2)3PbI3 (GUAPbI3), was conducted by slow evaporation of the mixture obtained by dissolving PbI2 and C(NH2)3I in acetonitrile. When the evaporation is done at 40 oC, a yellow needle-like crystals are being formed. The sample was characterized by elemental analysis, density measurements, scanning electron microscopy, thermal analyses, high-temperature X-ray powder diffraction and infrared spectroscopy measurements. The elemental analysis of the obtained crystals confirmed the proposed stoichiometry. The performed thermal analyses showed an endothermic peak associated with structural transition around 160 oC. On the other hand, the endothermic temperature effects above 300 oC are accompanied with mass loss and were interpreted as compound degradation. The crystal structure of high temperature polymorph between 160 oC and 300 oC was determined using high-temperature powder diffraction data measurements at 280 oC using simulated annealing technique in order to obtain initial structural model. The structure was refined using the Rietveld method. At temperatures higher than 160 oC, C(NH2)3PbI3 crystallizes in hexagonal space group P63mc with unit cell parameter a increasing from 9.269 ? to 9.337 ? between 160 oC and 300 oC and c parameter increasing from 15.211 ? to 15.287 ? in the same temperature range. The structure consists of PbI6 octahedra couples sharing a common face, linked with corners. Guanidinium cations are situated in the channels between Pb2I9 couples in a manner that the plane of the molecule is perpendicular to the c-axis.
- Dimitrovska-Lazova, Sandra,Bukleski, Miha,Tzvetkov, Peter,Aleksovska, Slobotka,Kovacheva, Daniela
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- In Vitro Reconstitution of a Five-Step Pathway for Bacterial Ergothioneine Catabolism
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Ergothioneine is a histidine-derived sulfur metabolite that is biosynthesized by bacteria and fungi. Plants and animals absorb ergothioneine as a micronutrient from their environment or nutrition. Several different mechanisms of microbial ergothioneine production have been described in the past ten years. Much less is known about the genetic and structural basis for ergothioneine catabolism. In this report, we describe the in vitro reconstitution of a five-step pathway that degrades ergothioneine to l-glutamate, trimethylamine, hydrogen sulfide, carbon dioxide, and ammonia. The first two steps are catalyzed by the two enzymes ergothionase and thiourocanate hydratase. These enzymes are closely related to the first two enzymes in histidine catabolism. However, the crystal structure of thiourocanate hydratase from the firmicute Paenibacillus sp. reveals specific structural features that strictly differentiate the activity of this enzyme from that of urocanate hydratases. The final two steps are catalyzed by metal-dependent hydrolases that share most homology with the last two enzymes in uracil catabolism. The early and late part of this pathway are connected by an entirely new enzyme type that catalyzes desulfurization of a thiohydantoin intermediate. Homologous enzymes are encoded in many soil-dwelling firmicutes and proteobacteria, suggesting that bacterial activity may have a significant impact on the environmental availability of ergothioneine.
- Beliaeva, Mariia A.,Leisinger, Florian,Seebeck, Florian P.
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p. 397 - 403
(2021/03/08)
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- Preparation of g-C3N4 Nanosheets/CuO with Enhanced Catalytic Activity on the Thermal Decomposition of Ammonium Perchlorate
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The thermal oxidation etching assisted g-C3N4 nanosheets/CuO was prepared through a facile co-precipitation strategy. In this work, the structure, morphology, and composition of g-C3N4 (UCN, prepared by urea), g-C3N4 nanosheets (TCN, prepared by thermal oxidation etching of UCN), g-C3N4/CuO (UCN/CuO), g-C3N4 nanosheets/CuO (TCN/CuO) were characterized via X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), X-ray photoelectron spectroscopy (XPS) and transmission electron microscopy (TEM). Furthermore, the catalytic effect of the obtained samples on the thermal decomposition of ammonium perchlorate (AP) was examined by thermal gravimetric analysis (TGA). As a result, in the case of 5 wt% TCN/CuO, the high decomposition temperature of AP decreased by 120.6 °C, which is much lower than that of UCN, TCN, CuO and UCN/CuO. In addition, the exothermic heat released from the decomposition of AP increased from 430.64 J g?1 to 2856.08 J g?1. This evident catalytic activity may be related to the synergistic effect of CuO and TCN. This work provides a novel strategy for the construction of composite catalyst for the thermal decomposition of AP, which is supposed to possess significant potential in the solid propellant field.
- Ma, Dan Na,Li, Xiao Meng,Wang, Xiao Qing,Luo, Yun Jun
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p. 982 - 988
(2021/02/26)
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- Copper (II) complexes with novel Schiff-based ligands: synthesis, crystal structure, thermal (TGA–DSC/FT-IR), spectroscopic (FT-IR, UV-Vis) and theoretical studies
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This study aimed to synthesize two novel Schiff-base ligands through the condensation between N-(2-aminoethyl)pyrazoles and 2-hydroxy-1-naphthaldehyde, which are: NaphPz ((E)-1-(((2-(1H-pyrazol-1-yl)ethyl)imino)methyl)naphthalen-2-ol)) and NaphDPz ((E)-1-(((2-(3,5-dimethyl-1H-pyrazol-1-yl)ethyl)imino)methyl)naphthalen-2-ol). These novel pyrazole-imines were synthesized, characterized and used as copper (II) ion complexing agents. Different synthetic routes have been adapted to obtain the [Cu(NaphPz)Cl], [Cu(NaphDPz)Cl] and [Cu(NaphPz)2] complexes in the solid state, the first two in the crystalline form and the latter as a powder. The minimum metal–ligand stoichiometry for the three complexes was defined by TGA–DSC thermoanalytical data and by single-crystal X-ray diffraction for the crystalline samples which belong to the P21/n space group. The products of the thermal decomposition of the material were also monitored by TGA–DSC/FT-IR in air and N2 atmospheres in order to suggest how thermal decomposition of the organic portion of the complex occurs. Density functional theory (DFT) and time-dependent density functional theory (TD-DFT) calculations compared to experimental results (UV-Vis and FT-IR) show a high degree of correlation. From HOMO/LUMO orbitals, the main major charge distributions, responsible for the absorption bands of the complexes, were determined.
- Campos, Guilherme Fava,Martins, Gabriel Rodrigues,Moreira, Jeniffer Meyer,Schwalm, Cristiane Storck,Tirloni, Bárbara,de Campos Pinto, Leandro Moreira,de Carvalho, Cláudio Teodoro
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- Fixation of Dinitrogen at an Asymmetric Binuclear Titanium Complex
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A new type of dititanium dinitrogen complex supported by a triphenolamine (TPA) ligand is reported. Analysis by single-crystal X-ray diffraction and Raman and NMR spectroscopy reveals different coordination geometries for the two titanium centers. Hence, coordination of TPA and a nitrogen ligand results in trigonal-bipyramidal geometry, while an octahedral titanium center is obtained upon additional coordination of an ethoxide generated upon C-O bond cleavage in a diethyl ether solvent molecule. The titanium complex successfully generates ammonia in the presence of an excess amount of PCy3HI and KC8 in 154% yield (per titanium atom). A titanium complex with a bulkier TPA does not form a dinitrogen complex, and mononuclear titanium dinitrogen complexes were not accessible, presumably because of the high tendency of early transition metals to form binuclear dinitrogen complexes.
- Bae, Dae Young,Lee, Gunhee,Lee, Eunsung
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supporting information
p. 12813 - 12822
(2021/09/06)
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- Electrochemical Nitric Oxide Reduction on Metal Surfaces
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Electrocatalytic denitrification is a promising technology for removing NOx species (NO3?, NO2? and NO). For NOx electroreduction (NOxRR), there is a desire for understanding the catalytic parameters that control the product distribution. Here, we elucidate selectivity and activity of catalyst for NOxRR. At low potential we classify metals by the binding of *NO versus *H. Analogous to classifying CO2 reduction by *CO vs. *H, Cu is able to bind *NO while not binding *H giving rise to a selective NH3 formation. Besides being selective, Cu is active for the reaction found by an activity-volcano. For metals that does not bind NO the reaction stops at NO, similar to CO2-to-CO. At potential above 0.3 V vs. RHE, we speculate a low barrier for N coupling with NO causing N2O formation. The work provides a clear strategy for selectivity and aims to inspire future research on NOxRR.
- Bagger, Alexander,Rossmeisl, Jan,Wan, Hao
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supporting information
p. 21966 - 21972
(2021/09/02)
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- Reduction of highly bulky triphenolamine molybdenum nitrido and chloride complexes
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Transition metal nitrides are key intermediates in the catalytic reduction of dinitrogen to ammonia. To date, transition metal nitride complexes with the triphenolamine (TPA) ligand have not been reported and the system with the ligand has been much less studied for ammonia formation compared with other systems. Herein, we report a series of molybdenum complexes supported by a sterically demanding TPA ligand, including a nitrido complex N Mo(TPA). We achieved the stoichiometric conversion of the nitride moiety into ammonia under ambient conditions by adding proton and electron sources to N Mo(TPA). However, the catalytic turnover for N2reduction to ammonia was not observed in the triphenolamine ligand system unlike the Schrock system-triamidoamine ligand. Density functional theory calculation revealed that the molybdenum center favors binding NH3over N2by 16.9 kcal mol?1and the structural lability of the trigonal bipyramidal (TBP) molybdenum complex seems to prevent catalytic turnover. Our systematic study showed that the electronegativity and bond length of ancillary ligands determine the preference between N2and NH3, suggesting a systematic design strategy for improvement.
- Bae, Dae Young,Lee, Eunsung,Lee, Gunhee
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supporting information
p. 14139 - 14143
(2021/10/25)
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- The Crucial Role of Charge Accumulation and Spin Polarization in Activating Carbon-Based Catalysts for Electrocatalytic Nitrogen Reduction
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Cost-effective carbon-based catalysts are promising for catalyzing the electrochemical N2 reduction reaction (NRR). However, the activity origin of carbon-based catalysts towards NRR remains unclear, and regularities and rules for the rational design of carbon-based NRR electrocatalysts are still lacking. Based on a combination of theoretical calculations and experimental observations, chalcogen/oxygen group element (O, S, Se, Te) doped carbon materials were systematically evaluated as potential NRR catalysts. Heteroatom-doping-induced charge accumulation facilitates N2 adsorption on carbon atoms and spin polarization boosts the potential-determining step of the first protonation to form *NNH. Te-doped and Se-doped C catalysts exhibited high intrinsic NRR activity that is superior to most metal-based catalysts. Establishing the correlation between the electronic structure and NRR performance for carbon-based materials paves the pathway for their NRR application.
- Chen, Ping,Hu, Zhenpeng,Ling, Tao,Mao, Jing,Qiao, Shi-Zhang,Qiu, Kangwen,Tang, Cheng,Wang, Ruguang,Yang, Yuanyuan,Zhang, Lifu,Zheng, Yao
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supporting information
p. 4525 - 4531
(2020/02/11)
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- Low-Coordinate Step Atoms via Plasma-Assisted Calcinations to Enhance Electrochemical Reduction of Nitrogen to Ammonia
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The electrochemical N2 reduction reaction (NRR) is emerging as a promising alternative to the industrial Haber–Bosch process for distributed and modular production of NH3. Nevertheless, developing high-efficiency catalysts to simultaneously realize both high activity and selectivity for the development of a sustainable NRR is very critical but extremely challenging. Here, a unique plasma-assisted strategy is developed to synthesize iridium diphosphide nanocrystals with abundant surface step atoms anchored in P,N-codoped porous carbon nanofilms (IrP2@PNPC-NF), where the edges of the IrP2 nanocrystals are extremely irregular, and the ultrathin PNPC-NF possesses a honeycomb-like macroporous structure. These characteristics ensure that IrP2@PNPC-NF delivers superior NRR performance with an NH3 yield rate of 94.0 μg h?1 mg?1cat. and a faradaic efficiency (FE) of 17.8percent. Density functional theory calculations reveal that the unique NRR performance originates from the low-coordinate step atoms on the edges of IrP2 nanocrystals, which can lower the reaction barrier to improve the NRR activity and simultaneously inhibit hydrogen evolution to achieve a high FE for NH3 formation. More importantly, such a plasma-assisted strategy is general and can be extended to the synthesis of other high-melting-point noble-metal phosphides (OsP2@PNPC-NF, Re3P4@PNPC-NF, etc.) with abundant step atoms at lower temperatures.
- Yang, Xiaohui,Ling, Faling,Zi, Xiangrong,Wang, Yanwei,Zhang, Han,Zhang, Huijuan,Zhou, Miao,Guo, Zaiping,Wang, Yu
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- Ru-doped, oxygen-vacancy-containing CeO2 nanorods toward N2 electroreduction
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Electrochemical N2 reduction (N2RR) in aqueous solutions under ambient conditions is extremely challenging; thus, a rational design of electrocatalytic centers is required to effectively adsorb and activate N2. Herein, we report Ru cluster-doped, oxygen vacancy-rich CeO2 (Ru/CeO2-VO) nanorods as an efficient N2 reduction electrocatalyst. The high-density oxygen vacancies inside CeO2 are beneficial for the adsorption of N2, and the unsaturated, low-valence Ru nanoclusters provide active sites for N2 activation and subsequent electron transfer for N2 reduction. The Ru/CeO2-VO catalyst exhibits a high ammonia production rate of 9.87 × 10-8 mmol s-1 cm-2 and a partial current density of 32 μA cm-2 at -0.25 V versus reversible hydrogen electrode in 0.05 M H2SO4 solution, corresponding to a faradaic efficiency of 11.7%. Our work suggests that the synergistic effects between Ru nanoclusters and oxygen vacancies in CeO2 for efficient N2 fixation.
- Ding, Yu,Guan, Anxiang,Huang, Linsong,Qian, Linping,Wang, Qihao,Zhang, Junbo,Zhang, Lijuan,Zheng, Gengfeng
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supporting information
p. 7229 - 7234
(2020/04/22)
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- Boosting Electrocatalytic Ammonia Production through Mimicking “π Back-Donation”
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Electrocatalytic dinitrogen reduction reaction (N2RR) is an emerging route for ammonia synthesis at ambient conditions. Albeit the “π back-donation” process enables N2RR activity on transition metals with empty d-orbitals, given its dilemma in overcoming hydrogen evolution reaction (HER) competition, exploring p-block-element-based catalysts with relatively inferior HER activity is achievable for high selectivity. The challenge lies in designing rational structure to improve N2RR activity. Here, we synergistically integrate oxygen vacancy (VO) with hydroxyl on Bi4O5I2 (VO-Bi4O5I2-OH), which render this p-block-element-based material active to mimic “π back-donation” behavior because of sufficient vacant orbitals. In neutral media, the electrocatalytic N2RR performance of VO-Bi4O5I2-OH in terms of splendid faradic efficiency (32.4%) is superior to most of the prior reports using p-block-element-based catalysts. Our findings show a new strategy toward standout N2RR activity, which holds great potential in exploiting other p-block-element-based electrocatalysts. Producing ammonia through an economical, sustainable approach has a profound impact on underpinning global agriculture. Electrocatalytic N2 reduction reaction (N2RR) is emerging as an alternative technology for synthesizing NH3 at ambient conditions. The poor hydrogen evolution ability of p-block-element catalysts emerge as promising candidates to produce ammonia with high selectivity (faradic efficiency [FE]). Due to the absence of d-orbitals, nevertheless, N2 activation and protonation are difficult on p-block-element catalysts. Employing rational surface electronic structure modulation can induce sufficient vacant orbitals, which promote N2 reduction through mimicking the “π back-donation” process. A standout electrocatalytic N2RR performance in terms of NH3 rate (20.44 μg h?1 mg?1cat.) and high FE of 32.4% is achieved in neutral electrolyte. This work motivates in-depth study to shed light on the new chemistry of ambient N2RR not relying on Haber-Bosch. Mimicking “π back-donation” is proposed as a facile, feasible, and generalizable approach to boost electrocatalytic ammonia production from dinitrogen on p-block-element catalysts, which lack d-orbitals. Such behavior is realized by providing sufficient empty orbitals on the surface of Bi4O5I2. The integrated modification of oxygen vacancy with hydroxyl achieves the generation of empty orbitals to reduce the energy barrier for N2 protonation. The intriguing strategy that takes advantage of the electronic structure modulation endows this p-block-element catalyst with a relatively high ammonia synthesis of 20.44 μg h?1 mg?1cat. in neutral media at a high faradic efficiency of 32.4%.
- Lv, Chade,Zhong, Lixiang,Yao, Yao,Liu, Daobin,Kong, Yi,Jin, Xiaoli,Fang, Zhiwei,Xu, Wenjie,Yan, Chunshuang,Dinh, Khang Ngoc,Shao, Minhua,Song, Li,Chen, Gang,Li, Shuzhou,Yan, Qingyu,Yu, Guihua
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supporting information
p. 2690 - 2702
(2020/09/02)
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- Metal–Sulfur Linkages Achieved by Organic Tethering of Ruthenium Nanocrystals for Enhanced Electrochemical Nitrogen Reduction
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Inspired by the metal–sulfur (M-S) linkages in the nitrogenase enzyme, here we show a surface modification strategy to modulate the electronic structure and improve the N2 availability on a catalytic surface, which suppresses the hydrogen evolution reaction (HER) and improves the rate of NH3 production. Ruthenium nanocrystals anchored on reduced graphene oxide (Ru/rGO) are modified with different aliphatic thiols to achieve M-S linkages. A high faradaic efficiency (11 %) with an improved NH3 yield (50 μg h?1 mg?1) is achieved at ?0.1 V vs. RHE in acidic conditions by using dodecanethiol. DFT calculations reveal intermediate N2 adsorption and desorption of the product is achieved by electronic structure modification along with the suppression of the HER by surface modification. The modified catalyst shows excellent stability and recyclability for NH3 production, as confirmed by rigorous control experiments including 15N isotope labeling experiments.
- Ahmed, Muhammad Ibrar,Chen, Sheng,Chen, Xianjue,Liu, Chuangwei,Ren, Wenhao,Zhao, Chuan,Zhao, Yong
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supporting information
p. 21465 - 21469
(2020/09/21)
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- Preparation of Nafion Membranes for Reproducible Ammonia Quantification in Nitrogen Reduction Reaction Experiments
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This study highlights the importance of following a strict protocol for Nafion membrane pretreatment for electrochemical nitrogen reduction reaction experiments. Atmospheric ammonia pollution can be introduced to the experimental setup through membranes and interpreted falsely as catalysis product from N2. The sources of ammonia contamination vary drastically between locations worldwide and even within the same location between days depending on temperature, wind direction, fertilizer use, and manure accumulation in its vicinity. The study shows that significant amounts of ammonium is accumulated in the membranes after commonly practiced pretreatment methods, where the amount depends on the ammonia concentration in the surrounding of the experiment. Therefore, we introduce a new pretreatment method which removes all the ammonium in the membrane. The membranes can be stored for several days but a short final step in the method needs to be carried out right before NRR experiments.
- Canales, Camila Pía,Flosadóttir, Helga D?gg,Hanifpour, Fatemeh,Skúlason, Egill,Sveinbj?rnsson, Arnar
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supporting information
p. 22938 - 22942
(2020/10/12)
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