The Performance And Stability Of AgBr Based Composite Photocatalysts

Recently,environmental pollution and energy shortages have arisen more and more prominent contradictions between social development and human settlements.The development of pollution-free technologies for both environmental remediation and alternative clean energy supplies is an urgent task which human faced.Semiconductor photocatalysis,which can directly utilize solar energy to degrade pollutant or produce hydrogen,has received more and more attention in recent decades for its easy operation,environmental friendliness and broad prospects in application.Silver bromide(AgBr),as a traditional semiconductor with excellent photosensitivity,is instable under illumination that prevent its practical application in photocatalysis.AgBr based composite photocatalysts are mainly focused on Ag/AgBr,however,it still suffers serious photocorrosion,which makes the study on the properties and stablility of AgBr based photocatalysts meaningful to its application.In this paper,CuO particles with dozens of nanometers were successfully modified on the surface of AgBr microparticles by slowly decomposition of Cu(OH)2.The result turns out that the final degradation rate of MO by CuO/AgBr sample reaches 91.8%,and the photodegradation constant is 4.3 times that of pure AgBr,showing improved photocatalytic performance.The pH value of the dye solution after photocatalytic progress reveals that the combination of Br-and photogenerated holes,which would result in the decomposition and recrystallization of AgBr,has beed reduced.For this reason,CuO/AgBr sample degrades 85.1%of MO in the third cycling experiment,which shows great enhanced photocatalytic stability.Further experiments indicate that holes play a dominate role in the catalytic system,and the holes come from AgBr since the inner-field from n-AgBr to p-CuO is established in the heterojunction by the close contact of CuO and AgBr.Hence,the transportation of holes is the key of the improved photocatalytic performance and stability of CuO/AgBr composites.In addition of the above-mentioned work,we wrapped the few layers of MoS2 that obtained by ultrasonic exfoliation on KBr surface,and then synthesized MoS2/Ag/AgBr photocatalyst with MoS2 of an everage thickness of 4 nm by ion exchange and reduction process.The phase structure and morphologic properties were characterized by XRD and SEM,and the layer of MoS2 was determined by laser Raman spectrum.UV-Vis absorption spectrum revealed that the absorption of MoS2/Ag/AgBr was superior to Ag/AgBr.The photocatalytic experiments reveal that the performance of MoS2/Ag/AgBr has improved by 50%.In the further study of the photocatalytic mechanism,we found that ultrathin MoS2 could transport the photogenerated electrons in Ag/AgBr.Therefore,the photocatalytic performance of Ag/AgBr has been improved.