A review on 2D MoS₂ cocatalysts in photocatalytic H₂ production

Owing to their unique physicochemical, optical and electrical properties, two-dimensional (2D) MoS₂ cocatalysts have been widely applied in designing and developing highly efficient composite photocatalysts for hydrogen generation under suitable light irradiation. In this review, we first elaborated on the fundamental aspects of 2D MoS₂ cocatalysts to include the structural design principles, synthesis strategies, strengths and challenges. Subsequently, we thoroughly highlighted and discussed the modification strategies of 2D MoS₂ H₂-evolution cocatalysts, including doping heteroatoms (e.g. metals, non-metals, and co-doping), designing interfacial coupling morphologies, controlling the physical properties (e.g. thickness, size, structural defects or pores), exposing the reactive facets or edge sites, constructing cocatalyst heterojunctions, engineering the interfacial bonds and confinement effects. In the future, the forefront challenges in understanding and in precise controlling of the active sites at molecular level or atomic level should be carefully studied, while various potential mechanisms of photogenerated-electrons interactions should be proposed. The applications of MoS₂ cocatalyst in the overall water splitting are also expected. This review may offer new inspiration for designing and constructing novel and efficient MoS₂-based composite photocatalysts for highly efficient photocatalytic hydrogen evolution.