Study On Preparation Of Bismuth Vanadate Based Photoelectrode And Its Photoelectrochemical Water Splitting Performance

Practical solar energy conversion has aroused great interest in renewable energy.Photoelectrochemical（PEC）water splitting is considered to be a promising and sustainable hydrogen production technology,and the development of new semiconductor materials is the key to achieving efficient solar-hydrogen conversion.Bismuth vanadate（Bi VO₄）is considered to be one of the most promising semiconductor materials because of its suitable band gap（about 2.4 e V）for good light absorption and conduction band position（low onset potential for triggering water oxidation）.However,Bi VO₄ suffers from severe electron-hole recombination and slow water oxidation kinetics,making its PEC performance be less than the theoretical maximum.Various methods have been developed to modify Bi VO₄ semiconductors to improve their overall PEC performance.It can be improved by introducing defect sites,crystal plane engineering,supported catalyst and heterostructure control.This topic aims at some shortcomings of Bi VO₄semiconductor,three schemes are proposed to improve the efficiency of photocatalytic decomposition of water.（1）Fe Bi/E-Bi VO₄ photoelectrode was successfully prepared through electrochemical treatment and immersion deposition methods.XPS and EPR analysis showed that there were abundant oxygen vacancies in Bi VO₄ after electrochemical treatment compared with pure Bi VO₄.The amorphous Fe Bi nanoparticles were further modified on the surface of the electrochemically treated-Bi VO₄ photoelectrode,which effectively promoted the charge transfer and separation.Under potassium borate（p H 9.5）electrolyte solution and 1.23 V（vs RHE）,the photocurrent density of Fe Bi/E-Bi VO₄ photoelectrode is as high as 3.2 m A cm^-2,which is 7 times that of pure Bi VO₄.（2）The photochemical and electrochemical pretreatment methods are combined to introduce abundant oxygen vacancies on the surface of Bi VO₄.Based on the slow water oxidation kinetics of the Bi VO₄ photoelectrode,（P+E）-Bi VO₄/Ni Fe Ox composite photoanode was successfully prepared by the photo-assisted deposition method.We found through the PEC performance test that the charge separation and transfer efficiency of the（P+E）-Bi VO₄/Ni Fe Ox composite photoanode was significantly improved,and the photocurrent density of the（P+E）-Bi VO₄/Ni Fe Ox photoelectrode reached 6.42 m A cm^-2（1.23 V vs.RHE）,creating a new photocurrent density record.（3）Porous wormlike Bi VO₄ photoelectrode was prepared by electrochemical deposition and high temperature calcination,and then PL-Bi VO₄ photo electrode was prepared by potentiostatic photochemical etching.In this work,the materials were characterized by SEM,XRD,HR-TEM and XPS,and a series of photoelectrochemical tests were carried out.The experimental results show that constant potential photochemical etching can produce oxygen rich vacancies on the semiconductor surface,which promotes charge transport and reduces numbers of carrier recombination,and significantly increases the photocurrent density.