Ruthenium-doped silver antimonate as a highly active and selective anode for acidic seawater electrolysis.

Direct seawater electrolysis enables on-site offshore renewable conversion, yet simultaneously achieving high activity, selectivity, and long-term stability for the oxygen evolution reaction (OER) under acidic conditions remains challenging. Herein, a series of Ru-doped silver antimonate catalysts are synthesized, among which AgSb0.97Ru0.03O3 delivers optimal performance: an overpotential as low as 92 mV, OER selectivity up to 85%, and robust stability exceeding 40 h at 100 mA cm-2 in acidic seawater. Theoretical calculations confirm that Ru doping creates new active sites with enhanced charge transfer, and the calculated *OOH adsorption energies correlate well with experimentally observed activity gains. The high selectivity stems from preferential OH- adsorption on Ru-OH sites and weakened Ag-Cl affinity that suppresses chlorine evolution, while exceptional stability arises from an insoluble Sb-O skeleton and corrosion-resistant Ru species reinforced by a surface Sb-OH protective layer, preventing structural collapse despite minor Ag+ leaching. The enhanced activity originates from intrinsically active Ru-OH centers, increased sites via surface hydroxylation, and optimized intermediate binding through d-band center modulation. Notably, compared with pure H2SO4 electrolyte, the presence of appropriate Cl- in acidic seawater kinetically synergizes both activity and selectivity by selectively etching inactive surface Ag to expose Sb-Ru-O interfacial sites, enriching local OH- via electric double layer modulation, stabilizing Ru oxidation states, and alleviating sulfate poisoning. This work offers a novel anode design strategy for water electrolysis in harsh marine environments, demonstrating promising prospects for direct offshore wind-to-hydrogen applications.