Unravelling of sulphur selenium unsaturation in 𝑴𝒐𝑺(𝟐−𝒙)𝑺𝒆𝒙 with efficient acidic and alkaline hydrogen evolution reaction (her)

Abstract

The need for clean and renewable hydrogen energy and fuel cells is substantial due to their ample availability, significant energy density, and environmentally sustainable characteristics. In this abstract, a strategy has been presented for the synthesis of hierarchical MoS(2-x)Sex by the manipulation of varying amounts of sulphur and selenium throughout the synthesis process. The reactive site for intermediate hydrogen (H*) adsorption in the overall hydrogen evolution process (HER) is confirmed by structural characterization and electrochemical experiments, which demonstrate the significance of S and Se unsaturation as well as their ratio. In the experimental study, it was observed that the introduction of a tiny amount of selenium (Se) into sulphur (S) resulted in a compound with the formula MoS1.8Se0.2. This compound exhibited improved catalytic activity for both acidic and alkaline hydrogen evolution reactions (HER), characterized by a low overpotential of -170 mV and -180 mV compared to the reversible hydrogen electrode (RHE) reference. At a current density of 10 mA/cm2, the compound had a Tafel slope of 40 mV/decade for the acidic HER and 43 mV/decade for the alkaline HER. The facile hydrogen evolution reaction (HER) performances have been compared to those of pure MoS2, MoSe2, and MoS(2-x)Sex materials with varying sulfur (S) and selenium (Se) ratios. Nevertheless, the enhanced electrode kinetics, increased density of catalytic active sites, and improved durability make MoS1.8Se0.2 a very competitive catalyst for the hydrogen evolution reaction, mainly due to its abundance in the Earth's crust.