Nanostructured Tungsten Oxysulfide as an Efficient Electrocatalyst for Hydrogen Evolution Reaction

Transition metal oxysulfides (TMOS) exhibit promising catalytic properties for hydrogen evolution reactions (HER). However, the development of facile and controllable routes for obtaining nanostructured TMOS under ambient conditions still remains a significant challenge. Here we report a simple and controllable route to synthesize nanoparticles of tungsten oxysulfides (WOxSy) that exhibit enhanced electrocatalytic activity toward HER with outstanding stability. The sulfur-rich tungsten oxysulfides with engineered anionic species can offer multiple functionalities, including abundant active sites and improved conductivity that synergistically contribute to enhanced electrocatalytic activity for HER. The optimized WOxSy electrocatalyst shows low overpotential of 103 mV at a current density of 10 mA cm–2, along with a Tafel slope of 54 mV decade–1 and 5.89 × 10–2 mA cm–2 exchange current density. Density functional theory (DFT) based calculations further establish the improved catalytic activity of tungsten oxysulfide (WOxSy), compared to the pristine 1T-WS2, based on the free energy calculations. The present work demonstrates a highly promising approach toward the development of cost-effective, efficient, and durable electrocatalysts to replace precious metals for electrocatalytic hydrogen generation.