Surface\nS‑Doped Nanostructured RuO<sub>2</sub> and Its Anion Passivating\nEffect for Efficient Overall Seawater\nSplitting

Electrolysis\nof seawater for hydrogen (H<sub>2</sub>) production\nto harvest clean energy is an appealing approach. In this context,\nthere is an urgent need for catalysts with high activity and durability.\nRuO<sub>2</sub> electrocatalysts have shown efficient activity in\nthe hydrogen and oxygen evolution reactions (HER and OER), but they\nstill suffer from poor stability. Herein, surface S-doped nanostructured\nRuO<sub>2</sub> (S-RuO<sub>2</sub>) is rationally fabricated for efficient\noverall seawater splitting. Doping with S enhances the activity (overpotentials\nof 25 mV for the HER and 243 mV for the OER), long-term durability\n(1000 h at 100 mA cm<sup>–2</sup>), and achieves nearly 100%\nFaraday efficiency (FE). Moreover, the S-RuO<sub>2</sub>-based anion\nexchange membrane seawater electrolyzer requires 2.01 V to reach 1.0\nA cm<sup>–2</sup> under demanding industrial conditions. Experimental\nanalysis and theoretical calculations indicate that surface S introduction\ncould lower the valence state of Ru, thereby conferring enhanced activity\nand stability. Furthermore, the nanostructured S-RuO<sub>2</sub> electrocatalyst\nis highly protected by the S-doped surface, which repels Cl<sup>–</sup> in alkaline seawater. This investigation presents a feasible strategy\nfor designing RuO<sub>2</sub>-based seawater splitting catalysts with\nboth high performance and good resistance to anodic corrosion.