Synthesis Of Facet-dependent Heterostructures Based On BiVO₄ For Enhanced Photocatalytic Activity

The rapid development of semiconductor photocatalysis technology is expected to solve problems of energy and environmental.Traditional TiO₂ have been greatly restricted in the field of photocatalysis due to its wide band gap.BiVO₄ has attracted widespread attention because of its suitable band gap?².4eV?,easy preparation,low cost and no pollution.However,BiVO₄ has the shortcoming that photogenerated carriers are easy to recombine,resulting in low photocatalytic efficiency.Therefore,how to suppress the recombination of photogenerated carriers has become a hot issue in the field of photocatalysis.In this paper,the monoclinic phase BiVO₄ with different active crystal plane exposure ratios was first prepared by hydrothermal method,and then the hydrothermal method was used to deposit CdS and the photodeposition method was used to deposit Au@CdS to construct a heterojunction photocatalyst to study the effects of crystal plane regulation,precious metal deposition and heterojunction construction on their photocatalytic activity.The main research contents are as follows:?1?Crystal plane control Monoclinic phase bismuth vanadate samples can be controlled to synthesize highly exposed active crystal planes to improve the photocatalytic efficiency of the samplesThe activity of the semiconductor photocatalyst is greatly affected by the atomic structure of the material surface.Because the adsorption of reactants,the desorption of products,the transfer between photogenerated electrons and reactants are essentially affected by the arrangement of surface atoms.In addition,the difference in crystal plane orientation will change the arrangement order of surface atoms.This shows that the activity of the photocatalyst is very sensitive to the change of the exposure ratio of the active crystal plane.To this end,in this experiment,by adjusting the pH of the precursor solution and the hydrothermal reaction conditions,BiVO₄ with a crystal face exposure ratio of 40%and 80%was synthesized.Experimental studies have shown that the highly exposed{010}crystal surface of BiVO₄ sample is more conducive to the separation of photogenerated carriers.The oxygen generation rate of decomposed water under visible light conditions reaches1.813 mmol/g/h,and its degradation of organic pollutants is also higher than that of traditional BiVO4.?2?Crystal plane control monoclinic phase bismuth vanadate photocatalyst constructs heterojunction can effectively separate interface charge and improve photocatalytic efficiencyConstructing a heterojunction composite material system can effectively improve the photocatalytic activity of BiVO₄.Photogenerated electrons will be transferred from one semiconductor's high conduction band energy level to another semiconductor's lower conduction band energy level,overcoming the charge transfer barrier and thereby inhibiting the photogenerated electron-hole pair recombination and promoting the separation and migration of photo-generated carriers.To the end,this experiment uses hydrothermal deposition of CdS on the surface of BiVO₄ and Au@CdS by photodeposition.Studies have shown that the photo-generated holes generated by CdS deposited on the electron surface under light excitation will combine with the photo-generated electrons generated by BiVO₄ to promote the separation of photo-generated carriers.The construction of heterojunctions can significantly improve the catalytic activity of semiconductor photocatalysts.The rate of photocatalytic decomposition of water and oxygen production by BiVO₄-Au@CdS reached 3.265 mmol/g/h,and the rate of photocatalytic degradation of rhodamine B also increased.