The Constructing And Characteristic Study Of Heterostructure Photocatalyst Based On ZnIn₂S₄ And C₃N₄

It is an effective method to improve the activities of photocatalytic system by decrease the recombination of photo-generated carriers.One of the most useful way to decrease the recombination of photo-generated carriers is designing heterostructure photocatalysts.Many works had proved that the benefits of constructing heterostructure photocatalyst are reducing the rate of recombination and increasing the separation of carriers by building build-in electric field,enhancing the absorption of light and accelerating the catalytic conversion rate in the photocatalytic system.In the process of designing and synthesizing heterostructure photocatalysts based on Zn In₂S₄ and C₃N₄and studying the characterization of them,we finished the works as follows:（1）The ZnIn₂S₄/reduced graphene oxide（RGO）/MoS₂ heterostructure photocatalytic systems have been synthesized by solvothermal and photo-deposition methods.By the deposition of RGO/MoS₂,which both work as cocatalyst,they have a synergistic effect for the enhancement of photocatalytic activity.The synthesis condition in this work has been optimized specifically and up to 1.62 mmol/h/g of photocatalytic water splitting into hydrogen rate has been get in visible light.In this system,Zn In₂S₄ acts as the main part of photocatalyst,which absorbs the light and generates the photo-generated carriers.The special structure of RGO facilitates the separation of carriers and prevent them from recombination.The MoS₂ enhances the catalytic conversion rate tremendously.（2）The microwave-assisted method has been applied to prepare Zn In₂S₄/g-C₃N₄heterostructure photocatalyst.The build-in electric field in this structure was applied to spatial separate photogenerated carriers.Thus the influence of pH medium of solution in the preparing process was searched and proved that the（100）crystal facet is crucial for the formation of this heterostructure which further verify that the heptazine structure of carbon nitride is key to the compositing of catalyst.（3）Mesoporous carbon/C₃N₄（MC/C₃N₄）composite photocatalysts have been prepared by impregnation-chemical combined with calcination method.The photocatalytic activities of the MC/C₃N₄ sample,not only hydrogen evolution rate but also the MB degradation rate,have been improved.The enhancement of the highest hydrogen evolution rate is up to 48%by the introduction of MC.The existence of small amount of MC can facilitate the photogenerated carrier separation and be beneficial for improving electron delocalization,which thus enhancing the photocatalytic performance.（4）The Er³⁺doped CaSnO₃（CaSnO₃-Er）was introduced into the system of carbon nitride to form a heterostructure photocatalyst.The study proves that the doping of Er will decrease the impedance instead of effecting the band structure of CaSnO₃.In the composite formed by C₃N₄ and CaSnO₃-Er,CaSnO₃-Er passivates the recombination center of carbon nitride,decreases the recombination in CaSnO₃-Er/C₃N₄ system and thus enhances the photocatalytic efficiency of the system.