Defect Control Of Oxides Photoanode And Its Application In Double Photoelectrode Catalytic Reaction

As a kind of sustainable green energy,solar energy is gradually becoming a trend in the future for conversion of new energy and sewage treatment.Photoelectrochemical（PEC）water splitting,as one of the most promising technologies to capture solar energy into chemical fuels,has attracted extensive scientific interest.In this paper,WO₃-based and Ti O₂-based metal oxide semiconductor photoelectrodes are main research objects.The photoelectrochemical performance of the photoelectrodes can be improved by adjusting the nano morphology,constructing heterojunction,introducing oxygen vacancies,modifying surface cocatalyst and other optimizing strategies.Si-based photocathode materials are prepared to develop a Fermi level matched double electrode system and build a self-driving photocatalytic fuel cell.The aim is to realize hydrogen production and degradation of organic pollutants without external potential,which provides a significant strategy for the development of new energy and new sewage treatment technology.The main contents of this paper are as follows:（1）We report an effective and facile strategy to promote the PEC performance by fabricating a WO₃ photoanode rich in oxygen vacancies（Ov）modified by Ni Fe-based layered double hydroxide（LDH）.When WO₃-Ov/Ni Fe-LDH is used as photoanode,the maximum photocurrent density at 1.23 V vs.RHE has been significantly enhanced to 2.0 m A·cm^-2,which is 4.3 times higher than that of bare WO₃.According to electrical impedance spectroscopic,X-ray photoelectron spectroscopy and Mott-Schottky analysis,the built-in electronic field in WO₃ homojunction,along with the accelerated hole capture by Ni Fe-LDH cocatalyst contributes to the improved charge carriers separation and transport in WO₃-Ov/Ni Fe-LDH electrode.（2）We develop an oxygen vacancies（Ov）enriched WO₃/Bi VO₄ photoanode modified by cobalt phosphate（Co Pi）cocatalysts for significant enhancement in PEC performances.Experimental results and theoretical calculations based on density functional theory（DFT）demonstrate that the Ov penetrated from WO₃ to Bi VO₄ layer will act as a highway for the charge transfer between semiconductor interfaces.Meanwhile,Co Pi as oxygen evolution cocatalysts can further accelerate transport of holes to electrode surface for the oxidation of water.Benefitted from this,（WO₃/Bi VO₄）-Ov/Co Pi photoanode yields a photocurrent of 2.3m A cm^-2 at 1.23 V vs.RHE with long-time stability.（3）TiO₂ nanowires are grown on carbon fiber substrate.m-V_O-Ti O₂ photoanode rich in oxygen vacancies is preparated by high temperature annealing in argon hydrogen atmosphere.The maximum photocurrent density at 1.23 V vs.RHE has been significantly enhanced to 1.6m A·cm^-2,which is 8 times higher than m-Ti O₂ and slightly higher than pl-Ti O₂.In addition,WO₃ photoanode rich in oxygen vacancies is preparated on carbon fiber substrates.The maximum photocurrent density at 1.23 V vs.RHE has been significantly enhanced to 1.2m A·cm^-2.In other hands,the silicon nanowire arrays are fabricated by hydrofluoric acid etching.A large number of Pt nanoparticles are uniformly deposited on the surface of p-Si by mild photodeposition method as hydrogen evolution cocatalyst of p-type semiconductor photocathode.Finally,m-Vo-Ti O₂ photoanode and Pt/p-Si photocathode are combined to form an integrated photocatalytic fuel cell,which generate a short-circuit current of 0.5 m A cm^-2 by simulating sunlight.The degradation rate of methyl orange and rhodamine B is more than 90%,while the average hydrogen production of cathode is 87.9μmol/cm³ per hour.The results indicate the feasibility of hydrogen production and organic pollutants degradation by double photoelectrodes self-driving photocatalytic fuel cell.