Fabrication Of Bismuth Vanadate Heterojunction Photoelectrode And Performance Study On Solar Energy Photoelectrochemical Water Splitting

Photoelectrochemical（PEC）water splitting for hydrogen production is a new energy conversion technology to solve energy crisis and environmental pollution problems,and has made great progress.Metal oxide semiconductors have been widely used in the preparation and research of PEC photoelectrodes due to their abundant raw materials,controllable micro-morphology and abundant energy level structure.Among many semiconductor materials,bismuth vanadate（BiVO₄）semiconductor has become one of the most promising oxide-based photoelectrodes for hydrogen production from water splitting of PEC due to its many superior performance.However,BiVO₄ also has some obvious shortcomings,such as serious photogenerated electron-hole pair recombination and slow kinetics of water oxidation,which limits its practical industrial application of PEC.At present,many strategies have been developed to modify BiVO₄ semiconductor to improve its overall PEC performance.The main improvement methods include noble metal modification,element doping,narrow band semiconductor recombination,micro-nanostructure modification and so on.Based on the problems existing in BiVO₄ semiconductor,three schemes for improving BiVO₄ semiconductor are proposed.By means of a series of characterization,the morphological structure,optical properties and PEC performance of BiVO₄ photoelectrodes are analyzed in depth.The construction of a excellent performance PEC water splitting system has been realized.（1）Ag₂S/BiVO₄ heterostructure photoelectrode was successfully prepared by electrochemical deposition and ionic layer adsorption/reaction method.XRD,FESEM,HRTEM,XPS and other characterization methods proved that the heterostructure photoelectrode was successfully synthesized.In this work,Ag₂S quantum dots were modified on the surface of BiVO₄ photoelectrode for the first time,which effective improved the charge transfer rate and inhibited the photogenerated electron-hole pair recombination.The photocurrent density and photoelectric conversion efficiency（IPCE）of Ag₂S/BiVO₄ heterostructure photoelectrode was significantly improved by PEC performance test.（2）With polydopamine（PDA）as the medium,Ag nanoparticles were successfully uniformly deposited on the surface of BiVO₄ photoelectrode.Then the photoelectrode was calcined under argon protection,and the PDA was carbonized into N-doped carbon.Finally,a new-type BiVO₄-C/N-Ag heterostructure photoelectrode was formed.In this work,we discussed the role of Ag nanoparticles and N-doped carbon in the photoelectrode system,and studied the charge transfer mechanism of the photoelectrode.The experimental results show that the modification of BiVO₄semiconductor by Ag nanoparticles and N-doped carbon can promote charge transfer and improve the stability of the photoelectrode.（3）In order to solve the problem of slow kinetics of water oxidation of BiVO₄photoelectrode,we first used Fe-doped CoP（Fe/CoP）oxygen evolution catalyst to sensitize the photoelectrode.The water splitting performance of BiVO₄-Fe/CoP photoelectrode under ultraviolet-visible irradiation was systematically studied.The PEC performance test showed that the coupling of BiVO₄ photoelectrode and Fe/CoP oxygen evolution catalyst could improve the charge injection efficiency and charge separation efficiency,thus significantly improving the photocurrent density and IPCE value.