Regulating The Microstructure Of Transition-Metal Based Catalysts For Effective Oxygen Evolution Reaction Electrocatalysts

The excessive use of fossil energy has brought great damages for our environment.Therefore,it’s urgent to find an alternative for the use of fossil energy and in this regard,hydrogen energy is promising for its high energy density and environmentalfriendliness.However,generating hydrogen from overall water splitting has now been hindered by its anode reaction,that is the oxygen evolution reaction(OER).Therefore,it’s of vital importance for the rational design of highly active and robust OER electrocatalysts.In this paper,we focus on transition-metal based OER electrocatalysts in alkaline media.First,based on a large number of literatures,we started with nickel-based layered hydroxides because they have benign intrinsic activity.By improving its electronic conductivity and BET specific area by introducing porous ITO as conductive substrate,a large improvement can be reached.Then,we jumped out of the constraints of hydroxides and found that selenides have excellent conductivity.Further experiments proved that introducing heterostructure and phase-transition engineering can improve the OER catalytic activity of the as-prepared selenides.Last,we focus on one kind of selenides in order to find out how crystalline structure would influence the OER catalytic activity.We proved it both experimentally and theoretically that the OER catalytic activity had strong relation with the crystalline structure and electric structure of active sites.The research procedure of the paper was step by step,from macroscopic properties like morphology,conductivity and specific area to microscopic properties like crystalline structure and electric structure.The brief introduction of the works in the paper is shown as below:1)To improve the electronic conductivity and enhance the specific area,we introduced porous Indium Tin oxides(ITO)to be the substrate of Ni Fe LDH.Detailed structural characterizations proved that the porous ITO can lower the work function of the catalysts,so as to improve the conductivity.The various pore structure of porous ITO can further enlarge the BET specific area of the catalyst,leading to the better catalytic performance of Ni Fe LDH@ITO.2)Selenides with heterostructure were designed and synthesized through a facile hydrothermal method.After electrochemical excitation or a KOH assisted hydrothermal method,the as-prepared selenides would undergo a phase transition process.It was proved experimentally that the heterostructure in selenides might make them easier to form oxyhydroxides,which is the active sites for OER,as thus improving their activity.The catalytic activity of selenides can be further improved by phase transition.3)To get a clearer view of the influence of crystalline structure on the OER catalytic performance,we designed a series of selenides with different crystalline structure.Experimentally,it was proved that the coordinated structure of the central cobalt atoms,including coordinated number,atoms and distance,changed after the crystalline changing.The change of coordinated structure would result in the change of electronic structure,leading to the optimizing of adsorption/desorption energy and thus a favor OER performance.