• • F-Ru-MnO2-TH achieves overpotentials of 280 mV (alkaline water) and 200 mV (simulated seawater) at 10 mA cm−2, outperforming commercial RuO2 and addressing the activity bottleneck for seawater electrolysis.
• • The catalyst retains ~100% of initial activity after 200 h in alkaline media and >95% after 300 h in simulated seawater, demonstrating exceptional long-term stability critical for industrial deployment.
• • The two-step dry-wet milling strategy enables throughout lattice F− doping and atomic Ru anchoring via Ru–O/F hybrid bonds, maximizing noble metal utilization and reducing cost.
• • Strengthened Mn 3d–O/F 2p hybridization and surface F− negative charge shield suppress ClOR and enhance Cl− tolerance, solving the selectivity and corrosion issues in seawater electrolysis.