Review on 2D Molybdenum Diselenide (MoSe₂) and Its Hybrids for Green Hydrogen (H₂) Generation Applications

Hydrogen (H₂) is a green and economical substitute to traditional fossil fuels due to zero carbon emissions. Water splitting technology is developing at a rapid speed to sustainably generate H₂ through electro- and photolysis of water without the harmful emissions associated with steam methane reforming. Development of efficient catalysts for the hydrogen evolution reaction (HER) is pertinent for economical green H₂ generation. In this regard, 2D transition metal dichalcogenides (TMDCs) are considered to be excellent alternatives to noble metal catalysts. Among other TMDCs, 2D MoSe₂ is preferred due to the low Gibbs free energy for hydrogen adsorption, good electrical conductivity, and more metallic nature. Moreover, the physicochemical and electronic properties of MoSe₂ can be easily tailored to suit HER application by simple synthetic strategies. Herein, we comprehensively review the application of 2D MoSe₂ in the electrocatalytic HER, focusing on recent advancements in the modulation of the MoSe₂ properties through nanostructure design, phase transformation, defect engineering, doping, and formation of heterostructures. We also discuss the role of 2D MoSe₂ as a cocatalyst in the photocatalytic HER. The article concludes with a synopsis of current progress and prospective future trends.