Nonmetal elements strictly govern the electrochemical performance of molybdenum compounds.Yet,the exact role played by nonmetals during electrocatalysis remains largely obscure.With intermetallic MoSi2comprising silicene subunits,we present an unprecedented hydrogen evolution reaction(HER)behavior in aqueous alkaline solution.Under continuous operation,the HER activity of MoSi2shows a more than one order of magnitude improvement in current density from 1.1 to 21.5 mA cmà2at 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 WSi2behaves almost the same as MoSi2,whereas other metal silicides with silicyne subunits,including CrSi2and TaSi2,do not exhibit any anomalous behavior.A thin amorphous shell of MoSi2is 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 MoSi2jointly 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.
supported by the National Key Research and Development Program of China(2016YFA0202603)
the National Basic Research Program of China(2013CB934103)
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).
Zechao Zhuang received his Master of Engineering degree from Fujian Normal University in 2015.He is currently a Ph.D.candidate under supervision of Prof.Liang Zhou and Prof.Liqiang Mai in Wuhan University of Technology.His research interests mainly focus on electron-structure-oriented design and synthesis of advance electrocatalysts for water splitting,fuel cell,and carbon dioxide reduction;Corresponding authors:Lyudmila V.Moskaleva is an Associate Professor at the Department of Chemistry,the University of the Free State,South Africa.She received her Ph.D.degree from Emory University,USA,in 2001 and carried out her postdoctoral research at Emory University in 2001 and Technical University of Munich,Germany,as a Humboldt Research Fellow in 2002–2006.Subsequently,she was a senior scientist at the Institute of Applied and Physical Chemistry at the University of Bremen,Germany,in 2009–2018.Her research interests include catalysis,electrocatalysis,theoretical chemistry,and surface chemistry.E-mail addresses:email@example.com;Corresponding authors:Liqiang Mai is Chang Jiang Scholar Chair Professor of Materials Science and Engineering at Wuhan University of Technology(WUT),Dean for School of Materials Science and Engineering at WUT,and Fellow of the Royal Society of Chemistry.He received his Ph.D.degree from WUT in 2004 and carried out his postdoctoral research in Prof.Zhonglin Wang’s group at Georgia Institute of Technology in 2006–2007.He worked as an advanced research scholar in Prof.Charles M.Lieber’s group at Harvard University in 2008–2011 and Prof.Peidong Yang’s group at University of California,Berkeley in 2017.His current research interests focus on new nanomaterials for electrochemical energy storage and micro/nano energy devices.E-mail addresses:firstname.lastname@example.org.