Ion-sieve-mediated continuous lattice oxygen regeneration for stable seawater electrolysis

Abstract Oxygen evolution reaction (OER) following the lattice oxygen mechanism (LOM) can operate at significantly reduced overpotentials compared with the adsorbate evolution mechanism (AEM), enabling suppression of the parasitic chlorine evolution reaction (ClER) in seawater electrolysis. Nevertheless, in Cl−-rich environments, competitive Cl− adsorption depletes the local OH− supply required to refill LOM-generated lattice oxygen vacancies, making continuous lattice oxygen regeneration difficult to sustain. Here we report a boron-doped cobalt phosphide (B-CoP) that dynamically reconstructs into dual-oxyanion-anchored Co-based oxyhydroxide (PO43−-BO33−-CoOOH), which functions as an interfacial ion sieve, selectively regulating the OH−/Cl− distribution to sustain continuous lattice oxygen regeneration along LOM pathway. PO43− oxyanion establishes an electrostatically repulsive layer that effectively excludes Cl−, whereas BO33− oxyanion organizes an ordered interfacial hydrogen-bond network that enriches OH− and promotes its adsorption. Driven by the localized electric field between BO33− and CoOOH, the adsorbed OH− subsequently migrates stepwise towards lattice oxygen vacancies in a thermodynamically spontaneous and barrier-free manner, thereby promoting continuous lattice oxygen regeneration under operando conditions. Remarkably, PO43−-BO33−-CoOOH delivers 500 mA·cm−2 at an overpotential of 366 mV and remains stable for 2000 h in alkaline seawater. This work provides mechanistic guidance for constructing LOM-based catalysts that sustain seawater electrolysis at industrial-level current densities.