Modification And Photocatalytic Properties Of BiVO₄ With Specific Facets

Semiconductor photocatalysis technology can effectively solve the problem of energy shortage and environmental pollution,and has broad application prospects in environmental management.Since the monoclinic phase BiVO₄ has narrow band gap and can be widely used in the photocatalysis field in response to visible light,it still has problems such as photo-generated carriers being easy to recombine.In this paper,BiVO₄ with specific morphology were prepared by adjusting the pH value of the precursor fluid.Based on BiVO₄ with specific facets,a Z-Scheme heterojunction of g-C₃N₄/{010}facets BiVO₄ interface,Ag-BiVO₄@RGO photocatalyst and Ag-BiVO₄-MnOx multi-level heterojunction photocatalyst were constructed.The separation rate of the photocatalyst photocarriers is improved,the photocatalytic activity of the photocatalyst under visible-near-infrared light is enhanced,and the utilization ratio of the photocatalyst to solar energy is improved.The main conclusions are as follows:?1?The effect of precursor pH on the formation and growth mechanism of BiVO₄ was studied.The proper amount of H⁺in the precursor liquid will be adsorbed on the active facets,which can effectively reduce the surface energy of the high active crystal surface and keep the active crystal surface in the final shape.The formation of the monoclinic BiVO₄ exposing the high active facets is nucleation-Ostwald ripening growth mechanism.The DFT theory calculates that the{010}and{110}facets of BiVO₄ can form surface heterojunctions.?2?The growth mechanism and photocatalytic mechanism of g-C₃N₄/{010}facets BiVO₄ interface Z-Scheme photocatalyst were studied.Under the induction of BiVO₄ surface heterojunction,photogenerated electrons are transferred to the{010}facets of BiVO₄,leading the{010}facets with negative charge and g-C₃N₄to be positively charged.The{010}facets of g-C₃N₄ and BiVO₄ form an interface Z-Scheme heterojunction by electrostatic attraction.The formation of the Z-Scheme heterojunction not only promotes the separation of photogenerated carriers,but also maintains strong redox ability.The degradation rate of photocatalyst can achieve 88.3%under 30 minutes visible light irradiation,and its mineralization capacity can reach 96.03%.?3?The effects of the RGO TE transverse wave and plasmonic Ag TM transverse wave on photocatalytic performance were investigated.The TE transverse wave of the RGO surface plasmon enables it to absorb near-infrared light,and the SPR effect of the plasmonic Ag enhances the light-absorbing ability of the photocatalyst.The SPR effect of plasmonic Ag nanoparticles can induce the generation of high-energy carriers.The local electric field generated by the surface plasmon of the RGO TE transverse wave and the local magnetic field generated by the plasmonic Ag TM transverse wave can enhance the photocatalytic activity of Ag-BiVO₄@RGO photocatalyst under visible and near-infrared light.?4?The oxidized cocatalyst MnOx and the reduced cocatalyst Ag were selectively deposited on the{110}and{010}facets of BiVO₄ by ultraviolet light irradiation.Three interface heterojunction is formed in the Ag-BiVO₄-MnOx composite photocatalyst,that is,the surface heterojunction formed by the{010}and{110}facets of BiVO₄,the formation of the metal Ag nanoparticles and the{010}facets of BiVO₄.The m-s heterojunction and the p-n heterojunction formed between the n-type BiVO₄ and the p-type MnOx.The formed multi-level interface heterojunction can enhance the separation rate of photogenerated carriers and inhibit their recombination.