Hybrid seawater electrolysis offers a breakthrough strategy for simultaneously achieving energy-saving hydrogen production and the degradation of sulfur-containing wastewater by employing the thermodynamically favorable value-added sulfion oxidation reaction (SOR) to replace the sluggish anode oxygen evolution reaction (OER) in overall seawater electrolysis. However, the passivation of the catalyst surface by solid sulfur (S8) products leads to poor stability, and the absence of a sulfur removal mechanism remains a major challenge. Here, we report a rare earth metal gadolinium-doped cuprous sulfide superionic conductor catalyst (Gd-Cu₂S/MNF) grown on an MXene-decorated nickel foam substrate (MNF) to address the key issues of sulfur-passivated electrodes, thereby achieving enhanced SOR activity and stability. The incorporation of Gd significantly weakens the affinity of the Cu-S bond in the original Cu₂S through the triple mechanisms of introducing new hybrid orbitals (Gd-S 4f/5d-3p), charge redistribution and lattice distortion, which is conducive to the desorption and electron transfer of active sulfur species during the SOR. Therefore, Gd-Cu₂S/MNF catalyst only requires a catalytic SOR potential of 0.29 V vs. RHE under 100 mA cm-2, which is significantly lower than the OER potential (1.72 V) in traditional water electrolysis. And at this current density, it exhibits remarkable catalytic stability (100 h). This work provides an important theoretical basis and method for the design of efficient and stable SOR-assisted hybrid seawater electrocatalysts for hydrogen production and the treatment of sulfur-rich wastewater.

Hybrid Seawater Electrolysis, Hydrogen Production, Sulfion Oxidation Reaction, Rare Earth Elements, Superionic Conductor