Preparation Of Transition Metal Oxide Thin Films By Electrodeposition And Electrocatalytic Properties

As one of the half-reactions of water splitting,oxygen evolution reaction(OER)limits the overall efficiency of water electrolysis due to its sluggish kinetics.Thus,developing highly efficient OER electrocatalysts has received extensive attention because this process has become a core technology of renewable energy sources.Oxides and(oxy)hydroxides of the first-row transition metals,including Mn,Fe,Co,Ni and Cu,single or mixed metal elements,have shown excellent performance for OER.Based on a scalable,simple and fast electrodeposition approach,the active performances toward OER are realized on catalyst films through negative/oxidative electrodeposition in bath solutions(contained a single ion,mixed metal ions,or metal-complex precursors).Electrochemical technique can accurate control the nucleation,growth,purities,structures and morphologies of catalysts,which is beneficial to industrial production.Therefore,A detailed study of preparing highly active transition-metal oxides catalysts by low-cost electrodeposition method is of great significance.And the main research results are presented:1.The Fe-based thin film catalysts,containing either single or multiple metal elements,were prepared by a direct anodic cyclic voltammetry(CV)method onto indium tin oxide glass(ITO)substrate.For instance,during the electrodepositon process of binary FeNiOx thin films,the deposition potential window,deposition time and the Fe/Ni molar ratio in baths were explored to obtain the optimized electrodeposition conditions.In this basis the deposited binary,ternary,and multicomponent metal oxides,including CoFeOx,FeNiOx,NiCoFeOx,CuNiFeOx,CuCoFeOx,and CuCoNiFeOx,demonstrate efficient catalytic activities toward OER in alkaline conditions.Additionally,the iron-free Ni-Co binary oxides were also prepared for comparison,resulting in excellent OER activities compared to FeNiOx.The structures,surface morphologies,composition,and valence states of different metal oxides films were evaluated by XRD,SEM,EDS,and XPS analysis,and the impact of the metal doping on OER performance was further investigated in our experiment.The essentially catalytic activity was evaluated through the comparison of both charge-transfer resistance(Rct)and electrochemical active surface area(ECSA).2.The indium tin oxide glass(ITO)and Ni foam(NF)were used as substrates,respectively.On the basis of anodic CV electrodeposition,we developed a stepwise electrodeposition strategy:the Ni-based or Co-based film was prepared through negative electrodeposition followed by an oxidative CV electrolysis in baths containing Fe3+ ions.The morphologies of samples prepared by this method are different from the direct CV electrodeposition.The as-prepared Fe-based thin films exhibit both efficient OER activities and durabilities in alkaline conditions.It’s noteworthy that the Fe-based catalysts,deposited on NF substrate,demonstrate excellent OER performances,due to the unique hierarchical porosities offer large active sites and gas bubble dissipation ability during the electrocatalytic process.