Composite Modification Of Bismuth Vanadate Nanosheets And Improvement Mechanism Of Visible Light Catalytic Activity

With the consumption of fossil fuel,as a result,the global energy crisis has also caused the increase of greenhouse gas emissions?mainly CO₂?and the accompanying environmental pollution,which has become an important problem to be solved urgently in human society,fortunately,the semiconductor photocatalytic technology is an effective strategy to solve these problems.Solar energy,one of clean and environmentally friendly energy mode,is drawing more and more attention to meet the increasing demands in this century.Visible light occupies about 44%in the solar spectrum,hence,it is very meaningful to develop visible-light-responsed photocatalyst.Bismuth vanadate?BiVO₄?is currently considered one of the most promising photocatalytic materials due to a series of desirable properties,including adequate absorption from the visible light region in solar spectrum?bandgap between 2.2 and 2.4eV?,excellent stability in an aqueous environment,etc.However,it usually exhibits weak photocatalytic performance,mainly owing to small specific surface area,the low carrier mobility and very short excited-state lifetime.Thus,we carry out this work,in which the visible-light activities of BiVO₄ are improved by morphology control of two-dimensional?2-D?structure,constructing nanocomposite?SnO₂?and silicate bridges modification,while the influences of them on charge carrier properties and activities are investigated in detail.First,2-D BiVO₄ nanoplates were facile prepared via a hydrothermal conversion with the pre-prepared BiOCl nanosheets as precursors and construct composite with SnO₂.The as-prepared 2-D BiVO₄ nanoplates exhibit better photocatalytic activity and photogenerated charge separation compared to BiVO₄ nanoparticles,it can be attributed to the special two-dimensional structure and the improvement of specific surface area.We further fabricated SnO₂ nanoparticle coupled Bi VO₄ by a wet-chemical process.The results of steady-state and time-resolved surface photovoltage responses,hydroxyl radical test reveal that coupling with a proper amount of SnO₂ could prolong the lifetime of charge carrier of BiVO₄ and improve the separation,which are mainly attributed to the visible photogenerated energetic electron transfer from Bi VO₄ to SnO₂,by which the high reduction activity of the electron of BiVO₄ is kept effectively and the charge carriers are separated spatially.The improved charge carrier properties lead to remarkable promoted photocatalytic activities of BiVO₄ for CO₂ conversion and2,4-DCP degradation.Secondly,we have successfully constructed silicate bridges in a SnO₂/Bi VO₄nanocomposite using wet-chemical processes to improve the connection situation between Bi VO₄ and SnO₂ and then promote the energetic electron transfer.The results of steady-state and time-resolved surface photovoltage responses,hydroxyl radical test and photo-electrochemical experiments show that the introduction of silicate bridges remarkable prolongs the lifetime of charge carriers of nanocomposite,leading to greatly enhanced photocatalytic activities of BiVO₄.The results of atmosphere controlled surface photovoltage responses,electrochemical impedance spectra and single wavelength photocurrent action spectra exhibit that the improved charge carrier properties of SnO₂/BiVO₄ nanocomposite are mainly attributed to that the energetic electron transfer from BiVO₄ to SnO₂ is promoted at the aid of introduced silicate bridge.This work opens up a feasible route to synthesize 2D visible-light-driven BiVO₄-based nano-photocatalysts with high photocatalytic activities for efficient fuel production and environmental remediation.