Nonmetal elements strictly govern the electrochemical performance of molybdenum compounds.Yet,the exact role played by nonmetals during electrocatalysis remains largely obscure.With intermetallic MoSi_2comprising sili...Nonmetal elements strictly govern the electrochemical performance of molybdenum compounds.Yet,the exact role played by nonmetals during electrocatalysis remains largely obscure.With intermetallic MoSi_2comprising silicene subunits,we present an unprecedented hydrogen evolution reaction(HER)behavior in aqueous alkaline solution.Under continuous operation,the HER activity of MoSi_2shows a more than one order of magnitude improvement in current density from 1.1 to 21.5 mA cm^(à2)at 0.4 V overpotential.Meanwhile,this activation behavior is highly reversible,such that voltage withdrawal leads to catalyst inactivation but another operation causes reactivation.Thus,the system shows dynamics strikingly analogous to the legendary Sisyphus’labor,which drops and recovers in a stepwise manner repeatedly,but never succeeds in reaching the top of the mountain.Isomorphic WSi_2behaves almost the same as MoSi_2,whereas other metal silicides with silicyne subunits,including CrSi_2and TaSi_2,do not exhibit any anomalous behavior.A thin amorphous shell of MoSi_2is observed after reaction,within which the Si remains partially oxidized while the oxidation state of Mo is basically unchanged.First-principles calculations further reveal that the adsorption of hydroxide ions on silicene subunit edges and the subsequent Si vacancy formation in MoSi_2jointly lead to the anomalous HER kinetics of the adjacent Mo active centers.This work demonstrates that the role of nonmetal varies dramatically with the electronic and crystallographic structures of silicides and that silicene structural subunit may serve as a promoter for boosting HER in alkaline media.展开更多
基金supported by the National Key Research and Development Program of China (2016YFA0202603)the National Basic Research Program of China (2013CB934103)+3 种基金the Programme of Introducing Talents of Discipline to Universities (B17034)the National Natural Science Foundation of China (51521001, 51832004)the National Natural Science Fund for Distinguished Young Scholars (51425204)the Fundamental Research Funds for the Central Universities (WUT: 2017III008, 2017III009)
文摘Nonmetal elements strictly govern the electrochemical performance of molybdenum compounds.Yet,the exact role played by nonmetals during electrocatalysis remains largely obscure.With intermetallic MoSi_2comprising silicene subunits,we present an unprecedented hydrogen evolution reaction(HER)behavior in aqueous alkaline solution.Under continuous operation,the HER activity of MoSi_2shows a more than one order of magnitude improvement in current density from 1.1 to 21.5 mA cm^(à2)at 0.4 V overpotential.Meanwhile,this activation behavior is highly reversible,such that voltage withdrawal leads to catalyst inactivation but another operation causes reactivation.Thus,the system shows dynamics strikingly analogous to the legendary Sisyphus’labor,which drops and recovers in a stepwise manner repeatedly,but never succeeds in reaching the top of the mountain.Isomorphic WSi_2behaves almost the same as MoSi_2,whereas other metal silicides with silicyne subunits,including CrSi_2and TaSi_2,do not exhibit any anomalous behavior.A thin amorphous shell of MoSi_2is observed after reaction,within which the Si remains partially oxidized while the oxidation state of Mo is basically unchanged.First-principles calculations further reveal that the adsorption of hydroxide ions on silicene subunit edges and the subsequent Si vacancy formation in MoSi_2jointly lead to the anomalous HER kinetics of the adjacent Mo active centers.This work demonstrates that the role of nonmetal varies dramatically with the electronic and crystallographic structures of silicides and that silicene structural subunit may serve as a promoter for boosting HER in alkaline media.
