Study On Preparation Of Monoclinic Bivo₄/CuInS₂ Composites And Relationship Between Their Structur And Photoelectric Performance

Semiconductor photoelectrocatalytic technology can use solar energy to reduce CO2 into liquid chemical products with high added value,such as methanol.In addition to alleviating the greenhouse effect,it can bring CO2 into a new carbon cycle,which is promising.However,due to the lower photocarrier separation efficiency of semiconductor catalysts and the higher dynamic barrier in the reaction process,CO2 photoelectrocatalytic reaction is insufficient.In this paper,the direct Z-scheme heterojunction composite material,mBiVO4(monoclinic BiVO4)/CuInS2 is constructed.CuInS2 is a semiconductor material of good optical absorption performance.Many researchers have reported that CuInS2 has the ability of reducing CO2 into methanol.The energy band gap of mBiVO4(2.5 eV)is a bit larger than that of CuInS2(1.5 eV),and the position of energy band is a bit more positive.The Z-scheme heterojunction can not only enhance the photocarrier separation efficiency,but also enhance the overall redox capacity of the composite.The CuInS2 thin film is prepared by electrodeposition method and mBiVO4 nanoparticles are fabricated by solvothermal method,respectively;then the mBiVO4/CuInS2 composite is prepared by loading mBiVO4 nanoparticles on CuInS2 thin film.Phase structure research shows that Z-scheme heterojunction has been constructed successfully.The results of Mott-Schottky test show that the flatband potential of CuInS2 and BiVO4 are 0.22 V(vs SCE)? 0.56 V(vs SCE)respectively,proving the Fermi level of CuInS2 is higher than that of BiVO4.As a result,the energy band of CuInS2 in the space charge layer bends upward,while that of BiVO4 bends downward.It provides a theoretical basis for the construction of Z-scheme heterojunction.The study on photoelectric property shows that the separation mode of photo-generated carriers in the composite conforms to Z-scheme heterojunction mechanism.Without reducing the redow ability,the composite material has higher photocarrier separation efficiency and lower interfacial charge transfer resistance.A series of researches have been carried out on their properties of photocatalytic reduction of CO2 to methanol.Under the optimal conditions,the methanol yield rate of composites is 3.75 ?mol/(h · cm2),while the yield rate of pure CuInS2 film is only 1.40 ?mol/(h · cm2);and the composites still have strong catalytic ability after continuous reaction for 10 h,exhibiting the methanol formation rate of twice of that on pure CuInS2 thin film.