Bifunctional Co 3 S 4 Nanowires for Robust Sulfion Oxidation and Hydrogen Generation with Low Power Consumption

Abstract Sulfion oxidation reaction holds great potential for replacing kinetically sluggish water oxidation to save power consumption and simultaneously purifying environmental sulfion‐rich sewage. However, it is still challenged by the insufficient mechanism understanding and questionable stability caused by sulfur passivation. Here, it is demonstrated that bifunctional Co 3 S 4 nanowires for assembling hybrid seawater electrolyzer that combines anodic sulfion oxidation and cathodic seawater reduction with an ultra‐low power consumption of 1.185 kWh m −3 H 2 under 100 mA cm −2 , saving energy consumption over 70% compared to the traditional water splitting system. Unlike water is oxidized into O 2 at high potentials under alkaline water splitting system, experiments combined with in situ characterizations uncover the stepwise oxidation of S 2− to short‐chain polysulfides and then to value‐added product of S 8 . Density functional theory calculations prove that Co 3 S 4 possesses reduced energy barriers in the rate‐determining S 3 2− to S 4 − oxidation step and S 8 desorption step, promoting conversion of short‐chain polysulfides and efficient desorption of S 8 . These findings reveal the catalytic mechanism of sulfion oxidation and inspire an economic approach toward the fabrication of bifunctional Co 3 S 4 for achieving energy‐saving hydrogen production from seawater while rapidly disposing sulfion‐rich sewage with boosted activity and stability.