Comparative investigation of the molybdenum sulphide doped with cobalt and selenium towards hydrogen evolution reaction

Hydrogen evolution reaction (HER) using earth abundant catalyst is one of the most promising approaches to replace precious platinum (Pt) and Pt-based catalysts for a green-energy environment. In this work, the HER performance of pristine MoS₂ is enhanced by doping of Co and Se atoms, which serve as additional active sites and oxygen defects on HER performance respectively, thereby tuning the electronic structure of pristine MoS₂ and further optimizing its hydrogen adsorption energy. The structural and morphological characterizations reveal the presence of the cuboid and raspberry nanostructures with a high order of crystallinity and extended interlayer spacing. The Co- and Se-doped MoS₂, display enhanced HER activity than pristine MoS₂ with a low onset potential of 181 mV and 166 mV, and a low overpotential of 218 mV and 207 mV at a cathodic current density of 10 mA cm⁻². More importantly, the Se-doped MoS₂ shows good catalytic stability with a low Tafel slope of 44 mV dec⁻¹ as compared with that of Co-doped MoS₂ (50 mV dec⁻¹) and other reported values in the literature. Furthermore, the density functional theory calculations were carried out to get a fundamental understanding of electrocatalytic activity of Co and Se doping onto MoS₂. This work can serve as a general methodology to enhance HER activity for the upcoming potential catalysts in the future and may uncover several applications in the field of solar photo-electrochemical (PEC) water-splitting cells and proton exchange membrane (PEM) electrolyzers.