Homogeneous water oxidation catalysts play a crucial role in the efficient utilization of hydrogen energy.The exploration of cost-effective metal catalysts based on redox-active ligands represents a promising approach...Homogeneous water oxidation catalysts play a crucial role in the efficient utilization of hydrogen energy.The exploration of cost-effective metal catalysts based on redox-active ligands represents a promising approach in this field.Non-precious metal catalysts,especially copper-based complexes,have emerged as viable alternatives,addressing the challenges associated with precious metals.In this study,theoretical calculations were employed to deeply investigate the catalytic mechanism of electrochemical water oxidation reactions mediated by a copper complex with redox-active ligands.Our theoretical research reveals the reaction sequence of proton-coupled electron transfer(PCET)oxidation,where the ligand undergoes PCET oxidation first,followed by the coordination of water to the copper center.The calculated redox potentials are in close agreement with experimental values.We considered two possible active species,Cu^(II)-OH·and CuII^(-)O··,and the calculation results indicate that the reaction pathway of Cu-O··has a lower activation energy barrier.For the critical O-O bond formation process,the catalyst guides the reaction through a unique single-electron transfer-water nucleophilic attack(SET-WNA)mechanism.It is noteworthy that the copper center of all the intermediates remains at the+2 oxidation state,highlighting the redox inertness of copper.These findings provide theoretical guidance for optimizing copper-based water oxidation catalysts.展开更多
Although the use of transition metals as bifunctional catalysts for zinc-air batteries(ZABs)has obvious economic advantages,their performance in ZABs still fails to meet expectations due to the uncontrollable loading ...Although the use of transition metals as bifunctional catalysts for zinc-air batteries(ZABs)has obvious economic advantages,their performance in ZABs still fails to meet expectations due to the uncontrollable loading caused by the rapid nucleation rate of transition metals.In this study,controllable loading of an Fe/Co alloy on heteroatom-doped hollow graphene spheres(FeCo@NGHS)was realized via the regulation of small molecules.Sodium citrate,which served as a metal complexing agent and reaction buffer,effectively suppressed the excessive loading of Fe/Co alloy particles and facilitated the formation of Fe(Co)Nx active sites.Melamine,which served as a precursor for doping N atoms,provided anchor points for the loading of Fe/Co alloy particles and participated in the generation of Fe(Co)Nx.The fabricated catalyst had active sites with different chemical structures,such as pyridine-N,graphite-N,Fe(Co)Nx and Fe/Co alloy particles,all of which benefit the improvement of the oxygen reduction reaction/oxygen evolution reaction(ORR/OER)performance.Results showed that the fabricated FeCo@NGHS,which possesses the appropriate amount of Fe/Co alloy particles combined with the highest amount of formed Fe(Co)Nx active sites,exhibited the best ORR/OER bifunctional catalytic performance in alkaline electrolytes and excellent electrocatalytic stability.The ORR onset potential and half-wave potential were 0.961 V and 0.846 V(vs.RHE),respectively.The OER could achieve a low overpotential level of 391 mV at a current density of 10 mA cm-2.Furthermore,the rechargeable liquid ZAB and flexible all-solid-state(ASS)ZAB assembled by FeCo@NGHS exhibited higher discharge power density and longer charge-discharge cycle performance.FeCo@NGHS-based air cathodes exhibited outstanding performance in flexible ASS-ZABs,showing high open circuit voltage(1.45 V)and peak power density(74.06 mW cm-2).Thus,in clean energy storage and conversion technologies,a new synthetic strategy for constructing excellent bifunctional oxygen electrocatalysts is proposed in this work.展开更多
基金supported by the NSFC(22263004)the National Natural Science Foundation of Guangxi Province(AD22035152).
文摘Homogeneous water oxidation catalysts play a crucial role in the efficient utilization of hydrogen energy.The exploration of cost-effective metal catalysts based on redox-active ligands represents a promising approach in this field.Non-precious metal catalysts,especially copper-based complexes,have emerged as viable alternatives,addressing the challenges associated with precious metals.In this study,theoretical calculations were employed to deeply investigate the catalytic mechanism of electrochemical water oxidation reactions mediated by a copper complex with redox-active ligands.Our theoretical research reveals the reaction sequence of proton-coupled electron transfer(PCET)oxidation,where the ligand undergoes PCET oxidation first,followed by the coordination of water to the copper center.The calculated redox potentials are in close agreement with experimental values.We considered two possible active species,Cu^(II)-OH·and CuII^(-)O··,and the calculation results indicate that the reaction pathway of Cu-O··has a lower activation energy barrier.For the critical O-O bond formation process,the catalyst guides the reaction through a unique single-electron transfer-water nucleophilic attack(SET-WNA)mechanism.It is noteworthy that the copper center of all the intermediates remains at the+2 oxidation state,highlighting the redox inertness of copper.These findings provide theoretical guidance for optimizing copper-based water oxidation catalysts.
基金support from the Zhejiang Provincial Natural Science Foundation(no.LR22E070001)the National Natural Science Foundation of China(no.12275239 and 11975205)+2 种基金the Guangdong Basic and Applied Basic Research Foundation(no.2020B1515120048)the Fundamental Research Funds of Zhejiang Sci-Tech University(no.23062096-Y)the Fundamental Research Funds of Ningbo University of Technology(no.2022TS17).
文摘Although the use of transition metals as bifunctional catalysts for zinc-air batteries(ZABs)has obvious economic advantages,their performance in ZABs still fails to meet expectations due to the uncontrollable loading caused by the rapid nucleation rate of transition metals.In this study,controllable loading of an Fe/Co alloy on heteroatom-doped hollow graphene spheres(FeCo@NGHS)was realized via the regulation of small molecules.Sodium citrate,which served as a metal complexing agent and reaction buffer,effectively suppressed the excessive loading of Fe/Co alloy particles and facilitated the formation of Fe(Co)Nx active sites.Melamine,which served as a precursor for doping N atoms,provided anchor points for the loading of Fe/Co alloy particles and participated in the generation of Fe(Co)Nx.The fabricated catalyst had active sites with different chemical structures,such as pyridine-N,graphite-N,Fe(Co)Nx and Fe/Co alloy particles,all of which benefit the improvement of the oxygen reduction reaction/oxygen evolution reaction(ORR/OER)performance.Results showed that the fabricated FeCo@NGHS,which possesses the appropriate amount of Fe/Co alloy particles combined with the highest amount of formed Fe(Co)Nx active sites,exhibited the best ORR/OER bifunctional catalytic performance in alkaline electrolytes and excellent electrocatalytic stability.The ORR onset potential and half-wave potential were 0.961 V and 0.846 V(vs.RHE),respectively.The OER could achieve a low overpotential level of 391 mV at a current density of 10 mA cm-2.Furthermore,the rechargeable liquid ZAB and flexible all-solid-state(ASS)ZAB assembled by FeCo@NGHS exhibited higher discharge power density and longer charge-discharge cycle performance.FeCo@NGHS-based air cathodes exhibited outstanding performance in flexible ASS-ZABs,showing high open circuit voltage(1.45 V)and peak power density(74.06 mW cm-2).Thus,in clean energy storage and conversion technologies,a new synthetic strategy for constructing excellent bifunctional oxygen electrocatalysts is proposed in this work.
