| Photoelectrochemical（PEC）water splitting hydrogen production technology can convert solar energy into clean,high-calorific hydrogen energy,thereby alleviating the exhaustion of fossil energy and improving some environmental pollution problems.As one of the core parts of this technology,the photoanode has always been a hotspot of widespread concern and research.Bismuth vanadate（Bi VO4）,as an n-type indirect narrow band gap semiconductor,is considered an ideal photoanode material due to its abundant raw materials,low price,non-toxicity and controllable morphology.However,its low photogenerated carrier separation and transfer rate and slow surface water oxidation reaction kinetics have severely restricted the development and application of Bi VO4 in the field of PEC water splitting.In this work,Bi VO4 thin film photoanodes were prepared by sol-gel and dip-coating method.The chemical reaction process and film formation mechanism of the system were analyzed.The influence rules and related mechanism of the technological parameters such as the pulling times and immersion time on the micro-morphology structure and photoelectrocatalytic performance were studied.The separation efficiency and dynamic characteristics of carriers were also discussed.Then,the cheap double transition metal-based cocatalysts Co Ni O2 and Ni Fe OOH were loaded on the surface of Bi VO4 by chemical hydrothermal and water bath methods.The carrier separation and utilization efficiency of the system were discussed,and the mechanism of the double transition metal-based cocatalysts to improve the photoelectric properties of Bi VO4 was revealed.The results show that the pulling times and immersion time have important effects on the microstructure and photoelectric properties of Bi VO4 thin film photoanodes.The former mainly determines the thickness of the film,which in turn affects the concentration of carriers,while the latter mainly determines the density of the film,thereby affecting the mobility of carriers.The best photoelectric performance can be obtained by pulling times of 5 and immersing for 30 s.The maximum photocurrent density is 0.521 m A/cm2（1.23 V vs.RHE）.Then,by providing more active sites,lower overpotential and capturing photogenerated holes on the surface in time,Bi VO4 photoanodes were modified with Co Ni O2,which promoted the separation and migration of carriers and improved the kinetics of water oxidation reaction.As a result,higher photocurrent density（1.16m A/cm2,1.23 V vs.RHE）,larger ABPE（0.163%）and IPCE（34.37%）,better stability,better hydrogen evolution rate(0.0148μmol?cm-2?min-1)and oxygen generation rate(0.0076μmol?cm-2?min-1)were obtained.Finally,Ni Fe OOH with semiconductor properties was used to modify Bi VO4 photoanodes.By constructing heterojunction structure,the spectral response range was widened,the absorption and utilization of photoenergy were enhanced,and the carrier separation was promoted.Therefore,the Bi VO4/Ni Fe OOH photoanode achieved a photocurrent density of 1.20 m A/cm2（1.23 V vs.RHE）,ABPE of 0.202%and IPCE of 34.51%,a hydrogen evolution rate of 0.0675μmol?cm-2?min-1,and an oxygen generation rate of 0.0366μmol?cm-2?min-1. |
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