Ruthenium-Doping-Induced Amorphization of VS₄ Nanostructures with a Rich Sulfur Vacancy for Enhanced Hydrogen...

The generation of pure H₂ from a neutral electrolyte solution represents a transformative route with low cost and environmentally friendly nature. However, the complex kinetics of hydrogen evolution reaction (HER) via water electrolysis make its practical application to be difficult. Herein, we have reported Ru-doping-induced formation of VS₄ nanostructures with a rich S vacancy for neutral HER in a 0.2 M phosphate buffer solution. The Ru-doped VS₄ demands an overpotential value of 160 mV at 10 mA/cm² current density with a lower catalyst loading of 0.1 mg/cm², while pristine VS₄ demands a 374 mV overpotential with the same mass loading. 60 hours of chronoamperometric study reveals the excellent stability of Ru-doped VS₄ materials, which is the highest amount of time ever reported for neutral HER. The marginal degradation of a catalyst under a long-term stability study was confirmed through inductively coupled plasma mass spectrometry (ICP-MS) analysis. The introduction of Ru to the VS₄ lattice leads to a 4.35-fold increase in the turnover-frequency values compared to those of bare VS₄ nanostructures. The higher HER activity of S-vacancy-enriched VS₄ materials is thought to originate through effective water adsorption in S vacancy and Ru³⁺ sites followed by the dissociation of a H₂O molecule, and S₂^2- efficiently converts H_ad to H₂. Also, post-HER characterization reveals that the transformation of some Ru³⁺ to Ru⁰ additionally favored the HER by providing a better H adsorption site under a static cathodic potential.