Preparation And Catalytic Activity Of Molybdenum Disulfide Doped Photocatalyst

Nowadays, the gradual depletion of fossil fuels has become a tough issue to us. Being aware of it, people start to pay their attenion to find a perfect substitution of fossil fuels, a clean and efficient new energy. Based on the photoelectric converting and photogenerated charge separation of semiconductor, photocatalytic technology, which brings us an effective way to transform solar radiant energy into chemical energy, may be the solution of the energy issues. As a narrow bandgap semiconductor, molybdenum disulfide (MoS2), which is able to convert visible light into photogenerated charges and transfer these photogenerated charges freely within its microscopic monolayer, has been noticed by many scientists. However, photocatalytic activity of pure MoS2 photocatalyst is limited by its electronic band structure. As a compromise, MoS2 usually be combined with other wide bandgap semiconductor, and works as a cocatalyst.With a view to the different light response in heterojunction, we choose cadmium sulfide (CdS) and zinc sulfide (ZnS), two of the semiconductors with wider bandgap and more active light response, as substrate for doping MoS2. As the result, MoS2-CdS and MoS2-CdS/ZnS are generated and used as photocatalyst in hydrogen evolution reaction under visible light irradiation. The main contents of our study are shown as follows.(i) To get early insights into the preparations for MoS2-CdS, some pre-experiments via hydrothermal and solvothermal processes are done before the formal experiments. With the experiences gained from pre-experiments, CdS nanoparticles with good water dispersibility are generated via hydrothermal processes, employing cadmium acetate and thiourea as the raw material and cetyltrimethyl ammonium bromide as structure promoter. MoS2-CdS products are generated by loading MoS2 on previous CdS nanoparticles via further hydrothermal processes with ammonium paramolybdate and thiourea.Through the study and optimizing of factors in the hydrothermal processe for MoS2-CdS, we find that the photocatalytic properties of MoS2-CdS is be mostly decided by the growth of MoS2, and change significantly in the period of reaction time reaching 21-24 hour because of the explosive appearance of MoS2.(ⅱ) Following the generation of MoS2-CdS via hydrothermal processe, CdS/ZnS nanoparticals are generated via hydrothermal assisted coprecipitation, using zinc acetate as zinc sources. These CdS/ZnS nanoparticals are proven to be a solid solution of CdS and ZnS. By loading MoS2 on CdS/ZnS nanoparticals via further hydrothermal processes, MoS2-CdS/ZnS photocatalyst is generated originality. Used as photocatalyst in hydrogen evolution reaction under visible light irradiation, MoS2-CdS/ZnS shows great catalytic activity and photochemical stability. Under the optimal conditions, the rate of H2 evolution reaches up to 12.30mmol·h-l·gcat-1, and stay the same after reuse without any treatment.