Ion-selective rare-earth gating enables compatible dual-site electrocatalysis for robust seawater splitting

The passivation layer for retaining electrocatalysts’ structural integrity during alkaline seawater splitting has gained abundant attention in recent years. Nevertheless, the exact reaction mechanism is still understudied, as the complex structural evolution of heterostructures lacks systematic investigation. Here, we elucidated a compatible adsorbate evolution-oxides pathway mechanism (AEM-OPM) on dual active sites in NiFe-LDHs triggered by electrochemically deposited (EPD) CeO_2-x permselective layer (<4 nm, LDHs/CeO_2-x). Such a reaction pathway can occur at Ni-Fe dual sites in reconstructed NiFe (oxy)hydroxides (NiFeOOH), arising from an elongated interatomic distance, induced by CeO_2-x layer confinement. Operando spectrometric techniques combined with mass spectroscopy and chemical probe confirm the localized OH^– groups on the surface of dynamically formed NiFeOOH, which promotes the ultimate *O-O* bond formation. Further theoretical calculations suggest an energetically favorable OPM route on Ni-Fe dual sites, bypassing the Δ_*OOH–_*OH linear scaling relation. Consequently, the LDHs/CeO_2-x OER catalyst exhibits a superior performance (η₁₀₀ = 260 mV) and stability (1 A cm⁻² over 1 month) in 1 M KOH. More importantly, such an EPD layer was successfully extended to the seawater electrolyzer [(−) NiMo/CeO_2-x||LDHs/CeO_2-x (+)] with a negligible potential deterioration (0.18 mV/hr) operating at 1 A cm⁻².