Microwave-assistant Hydrothermal Synthesis And Photocatalytic Performance Of G-C₃N₄/MoS₂ Semiconductor Compounds

Nowadays,the problem of energy shortage and environmental pollution is getting worse,and the non-renewable energy resources of the earth are gradually depleting.Besides,various pollutants from industry are causing great harm to the environment such as natural water bodies,ecosystems and so on.Therefore,there is an urgent need to develop pollution-free environmental remediation technologies.Among these technologies,the photocatalytic technology has received greater attention for its environmental-friendly,simple operation and easy to widely applicatied.Recently,semiconductor photocatalysis technology has developed rapidly,especially as g-C₃N₄ and MoS₂ semiconductor materials,which have suitable band gap and excellent carrier separation ability.In this thesis,the g-C₃N₄/MoS₂ composite（hereinafter referred to as CM）was successfully prepared via a microwave hydrothermal method.The influence of growth conditions on the photocatalytic performance of the material was systematically studied to improve the degradation ability of the CM composite under visible light.Firstly,urea was used as a raw material to prepare g-C₃N₄ through a calcination method,and the obtained samples were characterized by XRD and SEM.The preparation process parameters of g-C₃N₄ were determined as:the heating rate was 3℃/min,the calcination temperature was 500℃and the holding time was 4 h.Then,the g-C₃N₄ material prepared by calcination was acid-washed in concentrated hydrochloric acid to increase the interlayer spacing.The CM composite was prepared by the microwave hydrothermal method using the acid-washed g-C₃N₄ material as the substrate.Orthogonal experiments and single factor experiments were used to systematically study the growth conditions of the CM composite,and the XRD,SEM and TEM were used to characterize the prepared materials.The performance of degrading methylene blue（MB）solution for 1 h was used to optimize the preparing process of CM composite.The optimized process conditions are as following:the reaction time was 35 min,the mass ratio of Mo:g-C₃N₄was 0.6%,the reaction temperature was set to 200℃,the precursor p H was 5 and the atomic ratio of Mo:S was 1:2.5.The photocatalytic performance of the CM composite under the optimized process has been further studied.The degradation performance against other pollutants and the stability of photocatalytic performance of the optimized CM composite was investigated.And the main active substances in the photocatalytic degradation process were explored through the carrier capture experiment.The experimental results show that the CM composites has a good photocatalytic ability against MB solution,rhodamine B（Rh B）solution and congo red（CR）solution.The photocatalytic degradation rates based on CM composites were all reaches over93%after 1 h,and the degradation rate of MB solution has reached 99.3%.In addition,the photocatalytic performance of the CM composite was stable,which indicates this composite can be used as a stable and recyclable photocatalyst.Combined with the photocatalytic experiments and the characterization processes,the photocatalytic mechanism of the CM composite was explored.The results show that the reason for the excellent photocatalytic performance is the type II heterostructure composed of the composite.