Preparation And Modification Of MoS₂ As Cocatalyst For Photocatalytic Hydrogen Production

Graphite-like structure Molybdenum disulfide?MoS₂?is a photocatalytic material worth exploring because of its unique band characteristics and excellent stability as a cocatalyst for visible light response.In this paper,four modification schemes were used to design and prepare MoS₂ and its composites with excellent photocatalytic properties through simple hydrothermal method and heat treatment method.The effects of structural morphology,element doping and vacancies on photocatalytic properties were investigated by various characterization methods.The main research works are as follows:?1?The hydrothermal method and different alcohols?ethanol,ethylene glycol?were used as reaction solvents to control the morphology of MoS₂.And the flake MoS₂ with rich active sites and the worm-like MoS₂ were successfully synthesized.The method can effectively control the morphology and photocatalytic performance of MoS₂.The obtained MoS₂ showed a regular microscopic morphology and more excellent photocatalytic degradation properties.?2?A high performance MoS₂/G-TiO₂ composite was prepared by hydrothermal method.MoS₂ adsorbs on the surface of graphene,increasing the efficiency of transport and separation of photogenerated electron holes.The morphology and interfacial properties of TiO₂ were modified with hydrofluoric acid.Glucose was used as a surfactant to enhance the interaction of the MoS₂/G-TiO₂ composite interface.MoS₂/G-TiO₂ composite has high H₂ production efficiency under visible light and has good stability.MoS₂/G-TiO₂composites exhibited the highest photocatalytic H₂ production efficiency(1989?molg^-1h^-1)when the loadings were 5 wt%and 1 wt%?5MT-1G?of MoS₂ and graphene,respectively.The H₂ production efficiency of 5MT-1G was about 13.1,5.6 and 4.1 times that of pure TiO₂,1GT and 5MT,respectively.The excellent structure and morphology of MoS₂/G-TiO₂ composite help to improve the hydrogen production efficiency under visible light.?3?In order to further improve the photocatalytic performance of MoS₂.MoO₃@MoS₂material with high photocatalytic activity was prepared by hydrothermal synthesis and quenching.The results show that under the same conditions,MoS₂-340?/TiO₂ has excellent photocatalytic hydrogen production efficiency(4669?molg^-1h^-1),which was 5.8times that of unquenched MoS₂/TiO₂.Partial oxidation occurs on the surface and edges of MoS₂,producing MoO₃ and creating more traps at the interface locations where it binds.More photogenerated electrons can be enriched during the photocatalytic reaction,thereby achieving the purpose of exposing more active sites.?4?The surface of MoS₂ was treated by hydrothermal method using NaBH₄ as a reducing agent.MoS₂ with Mo vacancies was successfully prepared,and the amount of Mo vacancies was controlled by adding the concentration of NaBH₄.The surface and edge of MoS₂ after processing produced a lot of Mo vacancy defects,so more unsaturated S atom dangling bonds were exposed.These unbonded S atoms can act as adsorption sites for H⁺,greatly increasing the reaction site of MoS₂.The hydrogen production performance of MoS₂/TiO₂ composites was studied by photocatalytic evaluation system.The promoting effect of Mo vacancies on MoS₂ was studied.The results show that under the same conditions,the MoS₂ as a cocatalyst can significantly improve the photocatalytic hydrogen production activity of the composite.The photocatalytic hydrogen production efficiency of MoS₂-0.09/TiO₂ nanocomposites was 6.8 times that of untreated MoS₂/TiO₂.The Mo vacancy MoS₂ obtained by NaBH₄ reduction treatment can greatly improves the photocatalytic hydrogen production efficiency.