Study On Electronic Structure And Electrochemical Properties Of Transition Metal Oxygen Compounds

Clean energy is a high demand for achieving green and sustainable development.Hydrogen is considered to be an ideal substitute for traditional fossil fuels due to its high energy density and environmentally friendly characteristics.At present,the use of catalysts to electrolyze water is one of the most effective methods for generating hydrogen.However,the decomposition of water is composed of two half reactions:?I?hydrogen evolution reaction?OER?and?II?oxygen evolution reaction?OER?;the OER process is a key part that determines the efficiency of electrolyzed water due to the existence of four electron-proton coupled processes.Therefore,finding an efficient and economical OER catalyst has become a necessary requirement for the development of hydrogen energy systems.Due to the advantages of abundant reserves and low prices,transition metals and compounds have received extensive attention as OER catalysts.Based on SrRuO₃,we prepared SrRuO₃thin films by laser pulsed deposition method to study its OER performance.The details are as follows:?1?By changing the growth temperature of the films or selecting different substrates,amorphous,polycrystalline and different orientations?<100>/<110>/<111>?films with high quality were prepared by laser pulse deposition method film.Through electrochemical tests,we found that the amorphous SrRuO₃film exhibited excellent OER catalytic performance.The overpotential at a current density of 1m A/cm² was only 28m V,which was about 5 times higher than the performance of single crystal SrRuO₃.Subsequently,through the electronic structure test of SrRuO₃ films with different structures,it is found that the surface oxygen content of the amorphous SrRuO₃ film is twice that of the crystalline SrRuO₃ film.And in the test,it was found that due to its special amorphous state,it will show adaptability in the catalysis process.?2?When the laser pulse deposition method is used to grow an oxide film,the oxygen partial pressure is a key factor affecting the quality of the film.By changing the oxygen partial pressure during film growth,we found that the OER catalytic activity of the amorphous SrRuO₃ film does not change linearly with the increase of the oxygen partial pressure.Interestingly,when the oxygen partial pressure is at 1m Torr,the sample exhibits optimal OER catalytic activity.This reason is also related to the change in the internal electronic structure of the sample.When the oxygen partial pressure changes,the two factors that determine the catalytic activity of OER,such as the valence state ofRuand the active site on the surface of the sample,compete with each other,so the final sample shows OER catalytic activity is the result of the combined action of these two factors.?3?In previous research results,we found that although SrRuO₃ has excellent OER catalytic activity,its catalytic stability performance is not satisfactory.So how to improve the catalytic stability of SrRuO₃is the key to its application to commercial catalysts.In our work,the surface of the amorphous SrRuO₃ film is covered with a layer of amorphous La Ni O₃film.Result shows that the overpotential of prepared samples at 1m A/cm² is on the same level with commercialRuO₂,but the electrochemical stability is improved by nearly ten times.