Interfacial Stannate Regulation Enables 1500 h Chloride-Resistant Seawater Oxidation

Direct seawater electrolysis at industrially relevant current densities is constrained by chloride adsorption, competing chlorine oxidation, and accelerated anode corrosion. Here, we identify interfacial stannate formed during anodic operation as a key species responsible for suppressing Cl- adsorption and competing chlorine evolution. Operando Raman spectroscopy, inductively coupled plasma mass spectrometry, and time-of-flight secondary ion mass spectrometry reveal the partial dissolution of incorporated Sn species and the enrichment of stannate at the reconstructed catalyst-electrolyte interface, while density functional theory calculations further support its role in weakening Cl- adsorption. The resulting Sn-containing NiFe anode requires an overpotential of 377 mV to reach 1 A cm-2 and sustains operation at 1 and 2 A cm-2 for 1500 and 850 h, respectively. An anion-exchange-membrane electrolyzer further delivers 1 and 4 A cm-2 at cell voltages of 1.90 and 2.54 V at 80 °C, operates continuously for 1000 h at 1 A cm-2, and withstands 4500 start-shutdown cycles over 250 h. These results establish a direct link between working-state stannate chemistry and long-term chloride resistance under ampere-level seawater electrolysis.