Cr doping induces the valence state reconstruction of Co3S4 enabling sulfion oxidation coupling seawater electrolysis for hydrogen production

The sulfion oxidation reaction (SOR) presents an efficient pathway for hydrogen production via seawater electrolysis, as its anode voltage is substantially lower than that of the oxygen evolution reaction (OER). This thermodynamic advantage significantly reduces energy consumption while effectively suppressing chlorine evolution and related side reactions, thereby improving both the efficiency and economic feasibility of seawater electrolysis systems. Nevertheless, to achieve the practical application of SOR in real seawater electrolysis, it is still necessary to develop electrocatalysts with both high activity and long-term stability to withstand the harsh seawater environment under high current density. Herein, this study successfully synthesized Cr-doped Co 3 S 4 (Cr-Co 3 S 4 ) nanowires for the SOR. Cr doping reduces part of Co 3+ to active Co 2+ , and the high reducing property of Co 2+ accelerates the progress of SOR. In-situ Raman spectra and Density functional theory (DFT) calculations show that Cr doping optimized the adsorption of sulfion and polysulfide ions on Co 3 S 4 and the efficient desorption of S 8 , which improved the catalytic activity and stability. Furthermore, Cr-Co 3 S 4 only requires 0.596 V to achieve a current density of 100 mA cm −2 in the SOR-HER coupled system and maintains stability for 250 h. This work demonstrates a promising strategy for hydrogen production via sulfion-oxidizing mixed electrolysis of seawater, enabling energy-efficient hydrogen generation alongside sulfion-containing wastewater treatment. It thus provides a synergistic approach to green hydrogen production and environmental remediate.