Preparation And Photoelectrocatalytic Application Of Polyoxometalate/Semiconductor Photoelectrodes

The effective use of solar energy has been considered as an important way to solve the energy crisis.Photoelectrochemical technology based on semiconductor materials is an important method to convert solar energy into chemical energy or achieve organic conversion.However,the recombination of photo-generated electrons and holes in semiconductor materials is a serious problem,which limits the photoelectrochemical performance of semiconductor materials.Today,improving the photoelectrochemical performance has become an important research.Polyoxometalates?POMs?are a type of metal oxygen clusters based on Mo,W,and V.They can effectively transfer photo-generated electrons or holes in semiconductor materials,promote photo-generated electron-hole separation,then,suppress recombination.In this thesis,we introduced different POMs into BiVO₄ photoanode,organometal halide perovskite photoanode,organometal halide perovskite photocathode and CuBi₂O₄ photocathode to improve their photoelectrochemical performance,respectively.The specific works are presented as follows:1.Ag₁₀[Co₄?H₂O?₂(PW₉O₃₄)₂]?PW₉Co?,as a hole extraction layer,was used to modified the surface of the BiVO₄ photoanode for suppressing the fast electron-hole recombination.The experimental results show that BiVO₄/PW₉Co photoanode shows higher photocurrent of 3.06 mA/cm² at 1.23 V vs.RHE than pure BiVO₄photoanode,which indicates that the introduction of PW₉Co can significantly improve the separation and transfer of photogenerated charges and photogenerated charges recombination has been suppressed.Furthermore,we performed a photoelectrochemical reaction of oxidizing benzyl alcohol into benzaldehyde,in which the reaction yield of using BiVO₄/PW₉Co photoanode is significantly superior to the pure BiVO₄ photoanode.2.We have prepared an organometal halide perovskite photoanode.PW₁₂was used to induce perovskite grain growth and the density of defect states in perovskite is greatly reduced and the carrier transport is promoted.In addition,Ag₁₀[{Co?H₂O?₃}₂{CoBi₂W₁₉O₆₆?OH?₄}]?CoPOM?was employed to modified the surface of the perovskite photoanode for improving the separation and transfer of photogenerated charges and suppressed photogenerated charges recombination.And the prepared photoanode was used to oxidize benzene into phenol.The photoelectrochemical reaction results showed that after modifying of PW₁₂and CoPOM,the yield of phenol was significantly enhanced compared with pure perovskite photoanode.3.We have prepared an organometallic halide perovskite photocathode.The perovskite photocathode was modified by using g-C₃N₄/PW₁₁composite.The prepared photocathode was used to photoelectrochemical O₂ reduction to H₂O₂.The results showed that the g-C₃N₄/PW₁₁modified perovskite photocathode exhibits better performance in the photoelectrochemical O₂ reduction to H₂O₂.The g-C₃N₄/PW₁₁can transfer the photo-generated electrons in the perovskite photocathode,which facilitates O₂ reduction to H₂O₂.4.The nanoporous structure CuBi₂O₄ photocathode was prepared by using PEG-20000.Based on this CuBi₂O₄ photocathode,PMo₁₁V was used to dope the bulk of CuBi₂O₄,and Ag₆[P₂W₁₈O₆₂](P₂W₁₈)was used for surface modification of CuBi₂O₄ photocathode.PMo₁₁V and P₂W₁₈were used to suppress photo electron-hole recombination in bulk and surface of CuBi₂O₄.Compared with pure CuBi₂O₄ photocathode,the modified photocathode shows higher photocurrent of-0.41 mA/cm² at 0.3 V vs.RHE.The performance of photoelectrochemical hydrogen production of CuBi₂O₄ photocathode has also been enhanced.