Activating and Identifying the Active Site of RuS₂ for Alkaline Hydrogen Oxidation Electrocatalysis

Searching for highly efficient and economical electrocatalysts for alkaline hydrogen oxidation reaction (HOR) is crucial for the development of alkaline polymer membrane fuel cells. Here, we report a valid strategy to active pyrite-type RuS₂ for alkaline HOR electrocatalysis by introducing sulfur vacancies. The obtained S-vacancies modified RuS_2-x exhibits outperformed HOR activity with a current density of 0.676 mA cm^-2 and mass activity of 1.43 mA μg^-1, which are 15-fold and 40-fold improvement than those of Ru catalyst. In situ Raman spectra demonstrate the formation of S-H bond during the HOR process, identifying the S atom of RuS_2-x is the real active site for HOR catalysis. Density functional theory calculations and experimental results including in situ surface-enhanced infrared absorption spectroscopy suggest the introduction of S vacancies can rationally modify the p orbital of S atoms, leading to enhanced binding strength between the S sites and H atoms on the surface of RuS_2-x, together with the promoted connectivity of hydrogen-bonding network and lowered water formation energy, contributes to the enhanced HOR performance.