Oxygen evolution reaction(OER)and hydrogen evolution reaction(HER)are the key processes in water splitting.Compared with the two-electron process in HER,the four-electron process of OER is slow because of the more com...Oxygen evolution reaction(OER)and hydrogen evolution reaction(HER)are the key processes in water splitting.Compared with the two-electron process in HER,the four-electron process of OER is slow because of the more complex series of reactions.Therefore,a good understanding of the direct O_(2) evolution mechanism(DOEM)in OER is crucial to design high-efficiency catalysts to overcome the limitations imposed by the conventional adsorption evolution mechanism.In this work,honeycomb Ni_(3)N-Co_(3)N was prepared on carbon cloth(Ni_(3)N-Co_(3)N/CC)to investigate the DOEM.Density functional theory and in situ Raman scattering spectroscopy demonstrated that the OER process on Ni_(3)N-Co_(3)N/CC proceeded via the DOEM pathway,in which Ni_(3)N and Co_(3)N share the roles of dragging OH^(-),splitting off H-O bonds,and adsorbing other OH^(-),leading to significantly reduced Gibbs’s energy barriers of ΔG_(*OH) to ΔG_(O*)and ΔG_(O*)to ΔG_(O*OH).Moreover,the vertical honeycomb structure and conductive CC substrate contributed to the structural stability,conductivity,and quick O_(2) release capability.The Ni_(3)N-Co_(3)N/CC required low overpotentials of 320 and 495 mV to reach a current density of 10 and 100 mA cm^(-2),respectively.Moreover,the Ni_(3)N-Co_(3)N/CC delivered excellent stability with>90% retention of the initial current density over an 80-h-long test.展开更多
基金financially supported by the City University of Hong Kong HK Tech 300(SF202109174)the National Natural Science Foundation of China(51902118)the International Postdoctoral Exchange Fellowship program(PC2021026)。
文摘Oxygen evolution reaction(OER)and hydrogen evolution reaction(HER)are the key processes in water splitting.Compared with the two-electron process in HER,the four-electron process of OER is slow because of the more complex series of reactions.Therefore,a good understanding of the direct O_(2) evolution mechanism(DOEM)in OER is crucial to design high-efficiency catalysts to overcome the limitations imposed by the conventional adsorption evolution mechanism.In this work,honeycomb Ni_(3)N-Co_(3)N was prepared on carbon cloth(Ni_(3)N-Co_(3)N/CC)to investigate the DOEM.Density functional theory and in situ Raman scattering spectroscopy demonstrated that the OER process on Ni_(3)N-Co_(3)N/CC proceeded via the DOEM pathway,in which Ni_(3)N and Co_(3)N share the roles of dragging OH^(-),splitting off H-O bonds,and adsorbing other OH^(-),leading to significantly reduced Gibbs’s energy barriers of ΔG_(*OH) to ΔG_(O*)and ΔG_(O*)to ΔG_(O*OH).Moreover,the vertical honeycomb structure and conductive CC substrate contributed to the structural stability,conductivity,and quick O_(2) release capability.The Ni_(3)N-Co_(3)N/CC required low overpotentials of 320 and 495 mV to reach a current density of 10 and 100 mA cm^(-2),respectively.Moreover,the Ni_(3)N-Co_(3)N/CC delivered excellent stability with>90% retention of the initial current density over an 80-h-long test.
