Dual interface-reinforced built-in electric field for chlorine-free seawater oxidation

It is imperative but challenging for the development of oxygen evolution reaction (OER) catalysts suitable for high-current density seawater electrolysis without detrimental chlorine chemistry. Herein, we report a (Ni, Fe)OOH@NixP heterogeneous catalyst comprising the (Ni, Fe)OOH/Ni12P5/Ni2P dual-interface, in which the Ni12P5/Ni2P interface can enhance intrinsic driving force to propel the interfacial electron transport and form a strong built-in electric field (BEF) with asymmetric charge distribution at the (Ni, Fe)OOH/Ni12P5 interface, simultaneously promoting the OER kinetics and weaking the Cl- adsorption ability. As a result, the (Ni, Fe)OOH@NixP catalyst requires ultralow overpotential of 318 mV to achieve the current density of 500 mAcm−2 with outstanding stability in alkaline seawater. Notably, almost no hypochlorite is detected in the lab-scale seawater electrolyzer even if the cell voltage exceeds 1.72 V for a long term. This work highlights a design principle for heterogeneous catalysts and makes an important step forward for industrial seawater electrolysis. [Display omitted] •A (Ni, Fe)OOH/Ni12P5/Ni2P dual-interface has been proposed and constructed to catalyze chlorine-free seawater oxidation.•The dual-interface effect can form a strong built-in electric field (BEF) with asymmetric charge distribution.•The promotion mechanism of (Ni, Fe)OOH/Ni12P5 and Ni12P5/Ni2P has been revealed, respectively.•Almost no chlorine is formed during OER process at high current density.