Surface S-Doped Nanostructured RuO₂ and Its Anion Passivating Effect for Efficient Overall Seawater Splitting

Electrolysis of seawater for hydrogen (H₂) production to harvest clean energy is an appealing approach. In this context, there is an urgent need for catalysts with high activity and durability. RuO₂ electrocatalysts have shown efficient activity in the hydrogen and oxygen evolution reactions (HER and OER), but they still suffer from poor stability. Herein, surface S-doped nanostructured RuO₂ (S-RuO₂) is rationally fabricated for efficient overall seawater splitting. Doping with S enhances the activity (overpotentials of 25 mV for the HER and 243 mV for the OER), long-term durability (1000 h at 100 mA cm^-2), and achieves nearly 100% Faraday efficiency (FE). Moreover, the S-RuO₂-based anion exchange membrane seawater electrolyzer requires 2.01 V to reach 1.0 A cm^-2 under demanding industrial conditions. Experimental analysis and theoretical calculations indicate that surface S introduction could lower the valence state of Ru, thereby conferring enhanced activity and stability. Furthermore, the nanostructured S-RuO₂ electrocatalyst is highly protected by the S-doped surface, which repels Cl^- in alkaline seawater. This investigation presents a feasible strategy for designing RuO₂-based seawater splitting catalysts with both high performance and good resistance to anodic corrosion.