Controlled Synthesis And Photocatalytic Properties Of Sulfide Semiconductor Nanocomposites

Recently,with the rapid economic development,energy shortages and environmental pollution problems have become increasingly prominent.Therefore,the development of renewable and clean energy is urgent.The inexhaustible use of solar energy has huge application potential.The hydrogen energy has a large energy density,pollution-free water from combustion products,and can be recycled,and is considered to be the most ideal green energy source.Therefore,solar photolysis of water to produce hydrogen is considered to be one of the best ways to solve energy and environmental problems.The use of semiconductors as photocatalysts to direct use of solar energy for produce hydrogen is considered to be one of the most promising technologies.Traditional semiconductors such as Ti O₂and Zn O have low synthesis cost,are non-toxic,and have high chemical stability,but these oxide semiconductor materials can only respond to ultraviolet light due to their large band gaps,which leads to low utilization of sunlight.Compared with other traditional semiconductor photocatalysts,Cd S has more efficient visible light absorption capacity and more suitable band gap,which is a more ideal catalyst for photocatalytic hydrogen production.However,many shortcomings still exist in the bare Cd S,such as photo-corrosion,rapid recombination between photo-generated electrons and holes,which undoubtedly greatly limit its photocatalytic activity.In order to overcome the above defects and further improve its photocatalytic hydrogen production performance,a series of sulfide semiconductor nanocomposites were mainly synthesized as photocatalysts by ultrasonic water bath and solvothermal method in this thesis.The specific research contents are as follows:(1)Cd_0.5Zn_0.5S/Ni-MoS₂ nanocomposite photocatalysts were prepared by ultrasonic water bath and physical adsorption,which were uniform sphere with rough surface.The photocatalytic hydrogen production performance improved by doping Ni in Cd_0.5Zn_0.5S and co-catalyst MoS₂were supported to form type I heterogeneous,which can lead to the effective separation of photo-generated electrons and holes in space and greatly improve the photocatalytic activity of the material.(2)Dual co-catalysts system of Cd_1-xZn_xS-Ni₂P-MoS₂photocatalysts were prepared by ultrasonic water bath and physical adsorption.By controlling the doping amount of Zn,the band gap of Cd_1-xZn_xS can be continuously adjusted,and an appropriate amount of doping was helpful to improve photocatalytic activity.Ni₂P and MoS₂were used as dual cocatalysts to promote the effective separation of photogenerated electrons and holes.And the influence of the coupling sequence of cocatalysts on the migration and separation of charge carriers ware analyzed.(3)Cd_0.5Zn_0.5S@ZnS-Ni₂P/g-C₃N₄ photocatalysts were prepared by ultrasonic water bath,solvothermal and physical adsorption.Cd_0.5Zn_0.5S were covered with a layer of ZnS as a protective layer to form type-I core@shell structure.The surface of Cd_0.5Zn_0.5S@ZnS were more rough compared with Cd_0.5Zn_0.5S,which conducive to the anchoring of cocatalyst.The effective transfer and separation of photo-generated charges were achieved by supporting Ni₂P and g-C₃N₄as cocatalysts,can inhibit the recombination of photo-generated electrons and holes,thereby significantly improved the photocatalytic performance.