Study On Modification And Photoelectrochemical Behavior Of α-Fe₂O₃ Composite Photoanode

Following the idea of artificial photosynthesis to convert the inexhaustible solar energy into chemical energy with high availability is of great significance to the adjustment of the future energy structure.Photoelectrochemical hydrogen production by hydrolysis has broad development prospects due to its high abundance of energy input,high theoretical energy conversion efficiency,and green and sustainable hydrogen energy.The oxygen production process of electrochemical hydrolysis is a rate-controlled step,so the research and development of photoanode is very important.As a potential candidate material for photoanode in photoelectrochemical hydrolysis systems,hematite has the advantages of excellent energy band structure,high theoretical photoelectrochemical performance,stable property and structure,as well as non-toxic and easy preparation.Meanwhile,due to the problems of poor intrinsic conductivity,short hole migration distance,and easy recombination of photogenerated carriers,the high theoretical energy conversion efficiency of hematite is greatly limited in practical photoelectrochemical hydrolysis reactions.Combined with the strengths and weaknesses of hematite,the work of this subject has prepared an hematite composite photoanode by adjusting the oxygen vacancy concentration on the surface of the photoanode,loading co-catalysts on the surface,and improving the surface state by acid solution etching,and achieved a significant improvement in photoelectrochemical performance.At the same time,it takes into account its advantages in stability and usability.（1）A great quantity of oxygen vacancies are introduced on the surface of hematite by the method of oxygen-depleted environment treatment,and the concentration of oxygen vacancies is regulated.The utilization efficiency of photogenerated holes is significantly improved,and the photoelectrochemical hydrolysis performance is improved by 80%.Through analysis and testing,the mechanism of oxygen vacancies on the surface of hematite photoanode was clarified.（2）In order to reduce the activation energy required for the catalytic reaction and improve the reaction activity,compare the different methods of loading cocatalysts.Electrodeposition method was used to load Co-Pi cocatalyst on the surface of hematite,which effectively improved the kinetics of water oxidation on the surface of the photoelectrode and achieved a negative shift of 100 m V in the onset potential.（3）In view of the poor conductivity ofα-Fe₂O₃ substrate and high interface energy barrier,the method of etching with acetic acid solution is used to improve the intrinsic conductivity ofα-Fe₂O₃,reduce the influence of surface state on the catalytic performance of hematite,and realize the performance in photoelectrochemical hydrolysis reaction.60%increase.Finally,combined with the three modification methods used in this project,theα-Fe₂O₃ composite photoanode with high carrier concentration,high hole utilization efficiency and low interfacial reaction energy barrier was prepared.The photocurrent density was increased by 165%（2.15 m A/cm²）,and the onset potential was reduced by200 m V with high photoelectrochemical performance,reliability and stability.