Preparation Of WO_3-x/BiVO₄ Composite Photoanodes And Study On The Photoelectrocatalytic Performance

With the rapid development of global industrialization,the shortage of fossil energy sources and environmental pollution become severe.By virtue of semiconductor materials,photoelectrocatalysis（PEC）has been considered as one of the effective ways to produce clean energy and purify sewage.BiVO₄exhibits extensive research interests in the photoelectrocatalytic field due to the ideal bandgap（about 2.4 e V）,suitable band location and long carrier lifetime.However,restricted by low carrier mobility and the recombination of photogenerated carriers,the photocurrent density of BiVO₄ photoanode is much lower than the theoretical value.Meanwhile,BiVO₄ photoanode possesses poor stability because of surface photocorrosion,restraining the large-scale application of BiVO₄ photoanode in photoelectrocatalytic field.Herein,BiVO₄as the basic material was applied to form a composite photoanode with WO₃.By designing appropriate oxygen vacancies and TANF amorphous protection layer,BiVO₄ photoanode realized enhanced the photoelectrocatalytic performance and stability.The optimized BiVO₄photoanode was applied in photoelectrochemical water splitting,preparation of high value-added production and pollutant degradation.The main studies are as follows:（1）A simple electrodeposition method was adopted to prepare the BiVO₄photoanode.Afterwards,a WO₃ layer was loaded on BiVO₄ surface by the electrodeposition method.After annealing in an inert atmosphere,oxygen vacancies were formed,thus realizing the preparation of WO_3-X/BiVO₄composite photoanode.As a result,the photocurrent density of WO_3-X/BiVO₄composite photoanode was 3.79 m A cm^-2,which was twice that of BiVO₄photoanode（at 1.23 V vs.RHE）.Meanwhile,the formation of H₂O₂ could be detected in the applied bias range.The H₂O₂ production rate of WO_3-X/BiVO₄composite photoanode was 2.7 times that of BiVO₄ photoanode,which could reach 0.419μmol min^-1 cm^-2.Assisted by H₂O₂,the removal rate of Rhodamine B for WO_3-X/BiVO₄ composite photoanode increased to 93%within 100minutes,superior to BiVO₄ photoanode（80%）.（2）The WO_3-X/BiVO₄ composite photoanode was synthesized based on the method described above.Then,a tannic acid coordinated with Ni and Fe ions（TANF）catalyst was immobilized on the surface of the composite photoanode by the solution impregnation method.The photocurrent density of as-prepared WO_3-X/BiVO₄@TANF composite photoanode was 3.40 m A cm^-2（at 1.23 V vs.RHE）,which was 4.5 times that of BiVO₄ photoanode.In the absence of vanadium source,the WO_3-X/BiVO₄@TANF composite photoanode could still maintain a photocurrent density of 90%after 65 h of reaction.