Preparation And Photocatalytic Properties Of Semiconductor Nanocomposites Based On Graphene

With the rapid development of economy and society,the problem of environmental pollution is becoming increasingly serious.The control and treatment of environmental pollution has become a major problem to be solved in twenty-first Century.Photocatalytic technology is considered as an ideal new type of environmental pollution control technology since it has many advantages such as simple degradation process,directly using solar energy as the light source to drive the reaction,complete degradation of organic pollutants and no secondary regeneration pollution.However,semiconductor photocatalysts also have some urgent problems to be solved in the process of photocatalytic application,such as easy to clusters for nano-semiconductors which cannot be effectively adsorbed by organic contaminant molecules,the wide band gap of the semiconductor itself can only absorb the limited ultraviolet part of the solar light,the fast recombination of photo generated carriers leads to lower photo quantum yield and so on.Graphene is a new carbon material with a two-dimensional honeycomb lattice structure and tightly packed by a single layer of carbon atoms through the SP2 hybrid mode.Graphene is usually introduced and integrated with traditional semiconductor photocatalyst due to its unique properties of high specific surface area,high electronic conductivity and regular two-dimensional planar structure.On the one hand,it can reduce agglomeration of nanoparticles,and increase the photocatalytic reaction sites;on the other hand,it can also separate and transfer of photo-induced carrier to reduce the light-generated electron-hole pair recombination rate,so that the photocatalytic performance of composite catalyst can be improved effectively.Based on the above background,semiconductor photocatalyst based on graphene was prepared by one-step solvent thermal method due to the special functional properties of graphene in this paper.The optimal preparation route of composite photocatalytic materials was explored,and the crystal structure,microstructure,surface defect and photocatalytic degradation properties of the composites were also studied in detail.In addition,the mechanism of photocatalytic enhancement of the composite photocatalyst was discussed in-depth.The main research contents and results of this paper are as follows:?1?A series of ZnS/RGO nanocomposites have been successfully synthesized by using GO aqueous solutions,zinc acetate,sodium sulfide as raw materials and by adjusting the time and temperature of the solvent thermal reaction.The results show that the composite materials prepared under the initial reaction conditions at 180? and 10 h have the highest degree of crystallinity,the most uniform surface distribution and the most excellent photocatalytic degradation properties.?2?ZnS/RGO nanocomposites have been successfully synthesized by using sodium sulfide and thiourea as raw materials under the optimization initial reaction conditions?180? and 10h?,and the effects of the hydrolysis rate of thiourea and sodium sulfide on the preparation and photocatalytic activity of the composite were analyzed and compared in detail.The results show that ZnS/RGO nanocomposites prepared by using sodium sulfide as precursors has the best crystallinity,relatively more uniform surface distribution,the lowest surface defect and the highest photocatalytic degradation efficiency.?3?ZnS-TiO₂/RGO ternary nanocomposites have been successfully synthesized by using titanium dioxide powder?P25?and tetra butyl titanate?TBOT?as raw materials,and the mechanism of enhanced photocatalytic degradation of the ternary composite materials is discussed.The results show that the photocatalytic degradation performance of ZnS-TiO₂/RGO nanocomposites is better than that of ZnS/RGO nanocomposites.In addition,the photocatalytic degradation efficiency of ZnS-TiO₂/RGO nanocomposites prepared by TBOT is significantly higher than that of the composite materials prepared by P25.