Surface State And Interface Effect Of Transtion Metal (Ni/Co) Selenide Catalyzing The Oxygen Evolution Reaction

Precious metal-based catalysts are currently outstanding catalysts for the oxygen evolution reaction(OER)in water splitting.However,these catalysts have problems such as poor catalytic performance,high cost,and poor stability,which seriously hinder their development and commercialization.Therefore,the development of low-cost anode catalysts with good catalytic activity and stability is necessary to the practical application of hydrogen production by water splitting.The purpose of this thesis is to construct a new type of efficient and stable anode catalyst for water splitting.The surface state and interface effects of the catalysts are studied by using transition metal selenide which is abundant in the earth as catalyst for OER.The structure and morphology of catalysts were studied by physical characterization.The electrocatalytic properties of catalysts were systematically studied by electrochemical test.The specific research contents are listed as follows:(1)A one-step solvothermal method was used to prepare urchin-like CoSe2 catalysts with rich metallic Co-Se bonds and rough surface.The suitable synthesis temperature makes the catalyst surface have the best surface chemical state.It is found that a metal oxide/hydroxide layer will be formed on the surface of the original catalyst during the catalytic process.According to DFT theoretical calculations,metallic Co-Se bonds exposed on the surface can enhance the adsorption of oxygen-containing species,while metallic Co-Se bonds can increase the charge transfer rate during the electrochemical reaction,thereby improving its catalytic performance of the oxygen evolution reaction.(2)A three-dimensional NiSe2 nanoparticle/two-dimensional NiO nanosheet composite catalyst was prepared by simple annealing method,and the hybrid structure of NiSe2 nanoparticles/NiO nanosheets connected to each other is observed through physical characterization.It has excellent catalytic activity and stability for the oxygen evolution reaction,which is attributed to the strong synergetic coupling effects between NiSe2 nanoparticles and NiO nanosheets,interface effects due to the unique structure,rough surfaces and a large number of inherent Ni3+active site.Compared with NiSe2 and NiO catalysts,the catalytic activity of NiSe2 nanoparticles/NiO nanosheets catalysts for oxygen evolution is significantly improved.(3)We used NiCo(OH)x as a precursor and synthesize a NiSe2-CoSe2 composite catalyst by simple annealing treatment,and tested its performance of the oxygen evolution reaction with NiSe2 and CoSe2.The results show that NiSe2-CoSe2 composed of three-dimensional nanoparticles/one-dimensional nanorods has the best catalytic activity and stability.This is because the interface effect caused by special structure makes the surface of NiSe2-CoSe2 have more metallic Ni-Se bonds and Co-Se bonds,which improves the charge transfer rate during the electrochemical reaction,thereby increasing the catalytic effect for the oxygen evolution reaction.