MoS2-Based Nanocomposites for Photocatalytic Hydrogen Evolution and Carbon Dioxide Reduction

Photocatalysis is a facile and sustainable approach for energy conversion and environmental remediation by generating solar fuels from water splitting. Due to their two-dimensional (2D) layered structure and excellent physicochemical properties, molybdenum disulfide (MoS2) has been effectively utilized in photocatalytic H2 evolution reaction (HER) and CO2 reduction. The photocatalytic efficiency of MoS2 greatly depends on the active edge sites present in their layered structure. Modifications like reducing the layer numbers, creating defective structures, and adopting different morphologies produce more unsaturated S atoms as active edge sites. Hence, MoS2 acts as a cocatalyst in nanocomposites/heterojunctions to facilitate the photogenerated electron transfer. This review highlights the role of MoS2 as a cocatalyst for nanocomposites in H2 evolution reaction and CO2 reduction. The H2 evolution activity has been described comprehensively as binary (with metal oxide, carbonaceous materials, metal sulfides, and metal-organic frameworks) and ternary composites of MoS2. Photocatalytic CO2 reduction is a more complex and challenging process that demands an efficient light-responsive semiconductor catalyst to tackle the thermodynamic and kinetic factors. Photocatalytic reduction of CO2 using MoS2 is an emerging topic and would be a cost-effective substitute for noble catalysts. Herein, we also exclusively envisioned the possibility of layered MoS2 and its composites in this area. This review is expected to furnish an understanding of the diverse roles of MoS2 in solar fuel generation, thus endorsing an interest in utilizing this unique layered structure to create nanostructures for future energy applications.