Enhanced Photocatalytic Efficiency Of Visible-light-driven Photocatalysts For Environmental Purification By SPR Effect Of Bismuth

Water and air pollution,as a serious problem inevitably accompanied by the rapid development of society and economy,not only endangers the ecological environment,but also poses a threat to human life and health.Semiconductor-based photocatalysis is considered to be one of the most promising technologies in the field of environmental purification in the 21st century due to its advantages such as low energy consumption and non-poisonous.The traditional titanium dioxide（TiO₂）photocatalyst has been widely studied because of its high oxidation efficiency and non-toxic.However,TiO₂ can only be excited by ultraviolet light,and thus the utilization efficiency of solar energy is low.Therefore,designing and developing a highly active visible-light-response catalyst is imperative.As two typical visible visible-light-driven catalysts,cadmium sulfide（CdS）and bismuth tungstate（Bi₂WO₆）have attracted more and more attention in the research field of environmental purification in recent years.However,they always have the problems of fast photo-generated carrier recombination and low quantum efficiency.Therefore,this paper mainly uses the Bi-based surface plasma resonance（SPR）effect to enhance the environmental purification performance of CdS and Bi₂WO₆.The details are as follows:Firstly,Cd₂SO₄（OH）₂ and Bi（NO₃）₃·5H₂O were used as the precursors of CdS hollow microspheres and Bi,respectively.Under the strong reducibility of NaBH₄,Bi and Cd were anchored on the surface of CdS hollow microspheres.The photocatalytic activity of the Bi/Cd/CdS composite was evaluated by degrading dye X₃B under visible light.When the introduction amount of Bi nanoparticles in the composite is 10wt%,the sample exhibited the highest photocatalytic activity for the X₃B degradation,and the rate constant reached 0.11 min^-1,which is nearly three times higher than that of the Cd/CdS sample.The main reason for the significant increase in the photocatalytic activity is the enhancement of visible-light absorption and the increase of the specific surface area of the Bi/Cd/CdS composite material,as well as the improvement of the internal photogenerated electron-hole separation and transmission efficiency induced by the SPR effect of Bi.Secondly,the Bi-spherical modified Bi₂WO₆ was successfully prepared by heating the Bi₂WO₆ powder in a solution of Bi（NO₃）₃,using ethylene glycol as the reducing agent.The photocatalytic performance of sample was evaluated by the photocatalytic oxidation of NO under visible light.Both Bi nanospheres and Bi2WO6exhibited very poor photocatalytic activity,and the NO removal rates were only 7.7%and 8.6%,respectively.When the loading amount of the Bi nanosphere in the composite was 10 wt%,the NO oxidation removal efficiency achieved the highest（53.1%）.The enhancement of the visible light performance of the Bi/Bi₂WO₆composite was mainly attributed to the Bi SPR-induced enhancement of interface charge separation efficiency.