Preparation And Oxygen Evolution Performance Of Perovskite-based Catalyst For Electrolysis Of Water

The environmental problems caused by the excessive consumption of fossil energy are becoming more and more serious,and the development of clean and renewable energy is the solution.As an ideal carrier of green energy,hydrogen energy can free mankind from the rely on traditional energy sources.Hydrogen production by electrolysis of water has been widely noticed because of its simple process,mild conditions as well as high purity of hydrogen production.However,the overall efficiency of electrolytic water is mainly limited by the slow kinetics of the oxygen precipitation reaction involving four-electron transfer,which requires a highly active catalyst to accelerate its reaction process.Currently,noble metal-based catalysts are used as benchmark electrocatalysts for the electrolysis of water,but their low abundance and poor stability limit their large-scale application.Therefore,the development of highly active and low-cost non-precious metal electrocatalysts is crucial.In this thesis,the catalytic activity and stability of chalcogenide oxides are improved by modulating their crystal structure distortion,heterogeneous interface construction,electron configuration transformation and adsorption energy optimization based on the analysis of their reaction mechanism,decision speed steps and performance modulation strategies.The main work of this paper is as follows:（1）A series of Fe-doped chalcogenide oxide LaCoO₃ catalysts with precise molar ratios were synthesized using a ligand-assisted strategy.The preparation was accomplished by a solvent thermal reaction and an air thermal annealing process,in which the La Co_0.7Fe_0.3O₃chalcogenide oxides with 30 at%Fe doping exhibited excellent electrocatalytic activity in alkaline electrolytes,with a low overpotential of 352 mV at current density of 10 mA cm^-2,significantly outperforming the pristine LaCoO₃ performance.It showed good stability under55 h of continuous oxygen precipitation catalysis.Combined with a series of characterizations and theoretical calculations,the results show that doping proper amount of Fe in LaCoO₃perovskite makes the lattice expand,the metal-oxygen covalence degree and surface oxygen vacancy increase,and Co³⁺changes from low spin state to intermediate spin state,thus optimizing its electronic configuration and improving its oxygen evolution activity.（2）A series of coating structures LaNiO₃@FeOOH were synthesized by surface modification strategy to effectively improve oxygen evolution performance.By modifying the surface of LaNiO₃ with different amounts of FeOOH,it was found that the oxygen evolution performance of LaNiO₃@FeOOH-1:4 was the best when the molar ratio of LaNiO₃ and Fe²⁺was 1:4.It has a low overpotential of 315 mV and a low Tafel slope of 63 mV dec^-1 at 10 mA cm^-2,which is superior to the oxygen evolution performance of original LaNiO₃.Theoretical calculation results show that the coating of FeOOH reduces the reaction energy barrier for the conversion of oxygenated intermediates from^*O to^*OOH,and accelerates the conversion of oxygenated intermediates,which provides a feasible scheme for the preparation of high efficiency oxygen evolution catalysts.