Study On Transition Metal Sulfide As Co-catalyst For ZnIn₂S₄ Photocatalytic Water Splitting System

As the development of the global population, the consumption of primary energy will increase exponentially. In the near future, it is foreseeable that the deletion of limited fossil energy resources. Furthermore, a large of pollutants can be released through combustion of fossil fuels. These pollutants have caused enormous global environment crisis. These problems faced by human are the grand challenges in the creation of a sustainable society. Development of new energy technologies as fuel will be one of the major challenges faced by scientists. However, conventional TiO2-based photocatalysts can utilize no more than 5% of the total solar energy impinging on the surface of the earth due to its wide band gap, and its quantum efficiency is low, which all these limit the large-scale application of photocatalytic technology. Therefore, it is a challenging topic that developing novel photocatalysts with higher efficiency and stability in the photocatalytic field and exhibite a great significance for the sustainable development of photocatalytic science. The ternary sulfides with narrow band gap that strongly absorpt visible region may be a good candidate for photocatalytic water splitting and degradation dyes. But, metal sulfides are not stable during the photocatalytic reaction which commonly believed for people. Improving the stability of metal sulfide catalyst for photocatalysis is challenging.In this paper, we choice the ternary chalcogenide ZnIn2S4 as research object. According to the structure characteristic of ZnIn2S4, we modified the study object that introduced non-noble-metal NiS and MoS2 as co-catalyst loaded on the surface of ZnIn2S4. NiS/ZnIn2S4 nanocomposites were successfully prepared via a facile two-step hydrothermal process. MoS2/ZnIn2S4 nanocomposites were prepared by impregnating the hydrothermally prepared hexagonal ZnIn2S4 microspheres with an aqueous solution of (NH4)2MoS4, followed by a treatment in H2S flow at high temperatures. The photocatalysts were characteristic by XRD, XPS, UV-vis DRS, TEM and HRTEM. The influence of the loading amount of NiS(0.2 wt%-2.0 wt%) and MoS2(0.3 wt%-5.0 wt%) were studied. And an optimum NiS, MoS2 loading amount are found at 0.5 wt% and 0.6 wt%, which exibit the highest photocatalytic hydrogen evolution activity. The results showed that non-precious NiS and MoS2 replace the precious metal as a co-catalyst to improve the photocatalytic activity of ZnIn2S4 is promising.The innovations of this study are as follows:(1) Non-noble-metal NiS and MoS2 as co-catalysts are introduced into ZnIn2S4 semiconductor photocatalytic hydrogen evolution system, which can provide a new idea and path for the non-noble-metal replace Pt as co-catalyst application to photocatalytic hydrogen evolution; (2) The non-noble-metal co-catalyst may be also applied to any other photocatalytic reaction systems, which provides a new idea and direction for improving the catalytic activity.