Design, Preparation And Properties Of Two Heterojunction Photocatalytic Materials Based On The Regulation Of Carriers

In the rapidly developing modern society,environmental pollution and energy crisis have gradually become important issues that affect human production and life.Therefore,searching for efficient and environment-friendly technology to develop clean energy and tackle environmental pollution has been considered to be a pressing mission for scientists in the whole world.The photocatalytic technology utilizing solar energy can not only convert solar energy into pollution-free hydrogen energy by the way of splitting water,but also can purify pollutants in the environment through redox reaction.Semiconductor photocatalytic technology shows great advantages in environmental protection and energy development,which makes it a crucial technology to bring about the sustainable development of environment and energy of human society.Up to now,photocatalytic technology has made significant progress and development in energy development and pollutant degradation,but the low separation efficiency and poor transfer capacity of photogenerated carriers still have been the problems that limit its development and practical application.Thus,the development of new photocatalytic materials with high separation efficiency and transfer capacity of carriers has turned into the concentration and hotspot to promote the practical development of photocatalytic technology.In order to achieve the efficient separation and transfer of photogenerated charge carriers in materials,this paper designed and prepared two different types of heterojunction composite photocatalytic materials,studied their carriers separation and transfer characteristics in detail,and for the sake of heightening the reaction efficiency of photocatalytic water splitting to produce hydrogen and pollutants degradation.The possible mechanism of photocatalytic reaction of composites was revealed by studying the structure of heterojunction and the separation and transfer of charge carriers.The specific research contents mainly include the following two aspects:（1）Design,preparation and properties of S-scheme Ti_0.7Sn_0.3O₂/g-C₃N₄heterojunction composite photocatalytic materials.In this work,a typical non-metallic polymer semiconductor photocatalytic material,g-C₃N₄,is taken as the specific research object.Aiming at the matter of opting to recombination and poor transfer capacity of charge carriers in bulk g-C₃N₄,it was combined with Ti_0.7Sn_0.3O₂ with core-shell structure by magnetic stirring to form S-scheme Ti_0.7Sn_0.3O₂/g-C₃N₄heterojunction composite photocatalytic materials.Due to the successful construction of S-scheme heterojunction,Ti_0.7Sn_0.3O₂/g-C₃N₄ composite photocatalytic material exhibits more efficient separation efficiency and transfer capacity of carriers than the pristine Ti_0.7Sn_0.3O₂ and g-C₃N₄,and the S-scheme heterojunction also retains strong redox capacity,which makes S-scheme Ti_0.7Sn_0.3O₂/g-C₃N₄ heterojunction composite photocatalytic material has significantly improved photocatalytic reaction activity,in which 10 wt%Ti_0.7Sn_0.3O₂/g-C₃N₄（GST-10）composite sample has the most efficient separation efficiency and transfer ability,and thus shows the best photocatalytic reaction activity in the process of pollutants degradation and H₂ evolution.The hydrogen production rate of this composite under ultraviolet light was 476.98μmolg^-1h^-1,and the degradation efficiency of Rhodamine B was 98.5%within 20 min and that of tetracycline hydrochloride was 88.2%within 40 min.（2）Design,preparation and properties of Z-scheme WS₂/In₂S₃ heterojunction composite photocatalytic materials.In this work,the two-dimensional sheet-like In₂S₃nano photocatalytic material is taken as the specific research object.Aiming at the matter of easy recombination and poor transfer capacity of its charge carriers,a Z-scheme WS₂/In₂S₃ heterojunction composite photocatalytic material with bi-layered sheet-like structure was constructed by combining it with WS₂ nanosheets via condensation reflux method.The two-dimensional bi-layered sheet-like structure provided by WS₂/In₂S₃ heterojunction composite photocatalytic material can not only shorten the transfer distance of charge carriers,but also furnished a larger reaction area to promote the photocatalytic redox reaction.In addition,the Z-scheme heterojunction structure further promote the separation and transfer of charge carriers,and retains strong redox capacity.Thus,the Z-scheme WS₂/In₂S₃ heterojunction composite photocatalytic material exhibits a higher efficiency for the separation and transfer of photogenerated charge carrier and higher photocatalytic activity than the pure WS₂and In₂S₃.Among the prepared series of composite photocatalytic materials,the 50 wt%WS₂/In₂S₃ composite sample shows the best photocatalytic activity,and the hydrogen production rate under visible light irradiation was 592.9μmolg-1h^-1,the degradation efficiency of tetracycline hydrochloride can reach 90%within 60 min.