Intensified Accumulation of OH− and Improved Electron Transfer by Reactive Chlorine-Resistant Layer Achieve High-Durability Seawater Electrolysis

Abstract

The stability and efficiency of direct seawater electrolysis are constrained by competitive Cl− adsorption and corresponding chlorine oxidation reaction, which further restricts diffusion and accumulation of OH−, as well as transfer of electrons involved in counterpart oxygen evolution reaction (OER), leading to severe Cl−-corrosion. Herein, intensified popular-OH− accumulation and electron transfer are achieved through Ag-mediated reactive chlorine-resistant AgCl layer integrated onto NiCo-oxyhydroxide (AgCl/NiCo-OOH). Specifically, under external electric field driving, Ag species on the NiCo-OOH surface undergo electrochemical transformation and free Cl−-immobilization via in situ formation of robust AgCl layer, subsequently leveraging common-ion repulsion effect to sieve and control composition of ions in Stern layer, and thereby preventing Cl− corrosion. Simultaneously, the AgCl with high-curvature induces electric fields across scales, incorporating mesoscale proximal-tip and microscale built-in electric fields, which significantly accelerates OER kinetics by intensifying diffusion and accumulation of reactant OH− and transfer of electron. Resultantly, the AgCl/NiCo-OOH achieves an ultralow overpotential of 331 mV in alkaline simulated seawater and sustains stable operation for over 2200 h at Ampere-level current density in alkaline seawater without Cl−-related corrosion. Further, the corresponding anion-exchange membrane electrolyzer demonstrates a low energy consumption (4.50 kWh m−3 H2) and long-term durability (over 1500 h) at 500 mA cm−2.