Preparation Of Two-dimensional MoS₂-based Composite Catalysts And Performance For Photoelectrocatalytic Hydrogen Evolution

In recent years, energy crisis, environmental deterioration and climate change have become the most concerned spots in the world. In response to the change of global climate and ecology change, it is imperative to establish sustainable energy system with renewable and new energy system.The product of hydrogen combustion is water, which leads to neither air pollution nor greenhouse effect. Therefore, the hydrogen is always known as environmental friendly and renewable future energy.Photoelectrocatalytic hydrogen evolution reaction is one of the most efficient approaches to prepare hydrogen on account to its high efficiency and simple technology and so on. However, the traditional photoelectrocatalytic hydrogen materials have low utilization of sunlight and high energy consumption, therefore, designing and developping photoelectrocatalysts with high light utilization and high activity have become the research focus. Two-dimensional molybdenum disulfide with narrow band gap has been proved as two-dimensional nonmetal cathode catalyst with superior activity close to the noble metal platinum. However,low conductivity, fewer active sites of the edges, compounded easily photogenerated electrons and holes of MoS₂ materials limit its extensive application and development.In order to overcome the disadvantage of molybdenum disulfide above, we designed and prepared MoS₂-based composite catalysts and explored the morphology, structure and photoelectrocatalytic performance. The research achievements of this paper are as follows:The MoS₂/N-rGO （nitrogen-doped reduced graphene oxide）nanosheets, as cathodic HER catalyst, was directly prepared via a simple and ficile one-pot hydrothermal method. The added N-rGO improves the material conductivity and facilitates the charge separation and transfer efficiency. The photoelectrochemical performances for HER suggested that the electrochemical catalytic performance of MoS₂/N-rGO catalysts are much better than pure MoS₂ in acidic system, while their photocatalytic performance is unconspicuous.MoS₂/In₂S₃, as low-price and highly active electrode material, was designed and systhesised in order to solve the question of photogenerated charge recombination. MoS₂ and In₂S₃ catalysts with forming nanoscale heterojunction structure can greatly enhance the charge generation and effectively suppress the recombination of photogenerated charge, which is responsible for enhancement of photoelectrocatalyic hydrogen generation. The photoelectrochemical measurement of MoS₂, In₂S₃ and MoS₂/In₂S₃ catalysts shows that MoS₂/In₂S₃ catalyst has more excellent performance for HER, including higher electrochemically active surface area （ECSA） and smaller Tafer slope.The morphology and structure of MoS₂/In₂S₃ catalysts were regulated by adjusting the ratio of sodium molybdate and indium chloride precursors. The MoS₂/In₂S₃ sample with Mo:In ratios of 1:2 exhibited best photoelectrochemical activity for HER.Applying sodium molybdate and sodium tungstate as precursors, we prepared petal-like nanosheet MoS₂/WS₂ composite catalyst. Compared with the individual MoS₂ and WS₂, MoS₂/WS₂ composite catalyst had wider absorption range and Greater intensity for visible light. The photoelectrochemical measurement of catalysts suggests MoS₂/WS₂ catalyst exhibits outstanding photocatalytic performance for HER under the synergistic effect of MoS₂ and WS₂. The effects of different Mo:W ratios on MoS₂/WS₂ catalysts were investigated. The results indicated that MoS₂/WS₂ sample with Mo:In ratio of 1:1 exhibited best electrocatalytic and photocatalytic properties.