Engineering Zeolitic Imidazolate Framework Derivatives via Cation-Etching Strategy for Efficient Seawater Oxidation

Coupling renewable energy with seawater electrolysis is a highly promising strategy for sustainable hydrogen production. However, the practical application of direct seawater electrolysis remains challenging due to severe anode corrosion and the competitive chlorine evolution reaction (CER) induced by chloride ions. Herein, we report a facile cation-etching strategy to synthesise Fe@ZIF-67 catalysts at room temperature, using ZIF-67 as the sacrificial template and Fe2+ salts as the etching agent. The as-prepared Fe@ZIF-67 exhibits superior electrocatalytic activity for the oxygen evolution reaction (OER) in a simulated alkaline saline electrolyte (1.0 M KOH + 0.5 M NaCl). Specifically, it achieves a current density of 10 mA cm−2 at a low overpotential of 259 mV, outperforming commercial RuO2. Furthermore, an alkaline saline electrolyser assembled with Fe@ZIF-67 as the anode and Pt/C as the cathode requires a cell voltage of only 1.57 V to reach 10 mA cm−2, which is significantly lower than that of the RuO2||Pt/C benchmark (1.65 V). This work demonstrates that the cation-doping strategy effectively modulates the surface electronic structure of metal–organic frameworks (MOF)-based catalysts, providing a new perspective for optimising their performance in seawater electrolysis.