Enhanced System Photocatalytic Activity With Mo S₂/Graphene As Cocatalyst

As an effective strategy in lessening the energy shortage and environment pollution,semiconductor-based photocatalysis has already attracted extensive attention.Therein,developing excellent photocatalysts gives a top priority.Bi₂WO₆ is considered as a novel visible-light photocatalysts by virtue of the advantages just as environmentally friendly,unexpensive,and suitable for mass production.However,pure Bi₂WO₆ has low photocatalytic efficiency,easy agglomeration,small specific surface area,and low photoelectron-hole separation efficiency.In addition,g-C₃N₄has graphite-like layered structure and unique electronic structure which is excited by visible light.The development and application of g-C₃N₄ is restricted due to fast photogenerated electron hole pair recombination rate,strong fluorescence effect and low utilization efficiency of solar energy as a photocatalytic material.Recently,it has received wide attention that two-dimensional MoS₂/graphene composite is adopted as a hybrid cocatalyst to enhance system photocatalytic performance because of high conductivity,large specific surface area,favourable adsorbability and more active sites.In this paper,we introduced binary MoS₂/graphene cocatalyst into Bi₂WO₆ and g-C₃N₄ system to construct two kinds of ternary nano photocatalyst Bi₂WO₆/MoS₂/graphene and g-C₃N₄/MoS₂/graphene and build faster gradual charge transferred pathway from the perspective of band structure,which could effectively improve the photocatalytic performance of the system.The main research contents are as follows:?1?We prepared graphite oxide and MoS₂/graphene cocatalyst via the improved Hummers and hydrothermal method,respectively.Then Bi₂WO₆/MoS₂/graphene ternary photocatalyst was obtained by a two-step hydrothermal method.After MoS₂/graphene cocatalyst modified,the ternary photocatalyst inhibited Bi₂WO₆nanosheets agglomeration and had larger specific surface area,narrower band gap,stronger light absorption efficiency and faster photoproduction carrier separation and transfer efficiency.In the ternary system,MoS₂/graphene built a gradual charge transferred pathway depending on unique band position which accelerated the photoproduction carrier separation and transfer.Based on the experiment of degradation Rhodamine B under visible light irradiation,Bi₂WO₆/MoS₂/graphene photocatalyst showed the strongest degradation ability and the best total organic carbon removal ability.?2?The g-C₃N₄ nanosheets was obtained through a simple two-step thermal oxidation procedure by using melamine powder as the precursor.Different from bulk C₃N₄,g-C₃N₄ nanosheets had larger specific surface area,more surface active sites,and faster electron transfer ability along the direction of the plane because of quantum size effect.The ternary g-C₃N₄/MoS₂/graphene photocatalyst was prepared adopting an in-situ adsorption method.The ternary photocatalyst showed best photocatalytic activity in the degradation of Rhodamine B and antibiotic tetracycline experiments under visible light irradiation.MoS₂/graphene cocatalyst played a key role in ternary photocatalyst on account of the two-dimensional layered structure,which benefited the formation of well-contacted interfaces with g-C₃N₄ nanosheets and consequently facilitate the electron transportation during photoreduction reaction.