Simultaneous Sulfide Remediation and Low-Voltage Hydrogen Production Enabled by Ru-Doped CoNi Sulfide Catalysts

Abstract

Replacing the kinetically sluggish oxygen evolution reaction with sulfide oxidation provides an energy-efficient route for alkaline hydrogen production while enabling the simultaneous upgrading of sulfur-rich wastewater streams. Here we report a ruthenium-modified cobalt-nickel sulfide electrode grown on porous nickel foam (Ru-CoNiSx/NF). Structural analyses revealed intimate Co9S8/Ni3S2 coupling with highly dispersed Ru species, which induced local electronic modulation and optimized the surface reaction environment for sulfide oxidation and hydrogen evolution. In 1.0 M NaOH containing 1.0 M Na2S, Ru-CoNiSx/NF drived sulfide oxidation at 100 mA cm−2 with an ultralow potential of 0.282 V (vs. RHE) and a small Tafel slope of 20.3 mV dec−1. Ru-CoNiSx/NF also exhibited excellent alkaline HER performance, requiring only 32 mV to reach 10 mA cm−2. Density functional theory calculations indicated that Ru-CoNiSx/NF had lower energy barriers for the S3* oxidation and S8* desorption steps, thereby promoting polysulfide conversion and sulfur release and accounting for its outstanding SOR activity and stability. A two-electrode sulfide oxidation-hydrogen evolution electrolyzer assembled with Ru-CoNiSx/NF achieved 50 mA cm−2 at 0.651 V, which was 1.468 V lower than that of conventional water electrolysis. This system maintained stable operation for over 200 h and enabled polysulfide accumulation followed by sulfur recovery. This work demonstrated an efficient bifunctional sulfide electrocatalyst for energy-efficient hydrogen production coupled with sulfide valorization, providing a promising strategy for integrated sulfide-containing wastewater treatment and low-energy hydrogen generation.