Dual Lewis Acid Sites Enabling Passivation-Resistant Sulfur Oxidation Coupled Hydrogen Evolution Reaction

The coupling of the sulfide oxidation reaction (SOR) with the hydrogen evolution reaction (HER) is a promising approach for energy-saving hydrogen production and sulfide-containing wastewater treatment. However, transition metal-based catalysts suffer from sluggish kinetics and sulfur passivation at high current densities. Herein, an oxygen-coordinated iridium single-atom anchored on a nickel surface (Ir₁O-Ni/C) is designed to generate adjacent dual Lewis-acid sites, thereby constructing a species-selective catalytic surface. Mechanistic analysis reveals that the dual Lewis acid sites polarize interfacial water, reconstructing hydrogen bonding networks to promote water supply and enhancing their dissociation for HER, while strong Lewis acid-base interactions expedite the adsorption and conversion of sulfide ions during SOR. Meanwhile, the electron-deficient Ni alleviates the excessive adsorption of neutral S₈* and H*, thereby suppressing sulfur accumulation and accelerating hydrogen release. The optimized Ir₁O-Ni/C catalyst achieves a current density of 1 A cm^-2 at an overpotential of 280 mV for HER, and requires only 0.67 V to deliver 500 mA cm^-2 for SOR, with stable flow cell operation for over 50 h. The versatility of the approach is demonstrated by Ru/Pt_xO-Ni/C, which all show improved activity compared with the conventional Ni/C catalysts, providing atomic-level insights into the development of bifunctional catalytic systems.