Strengthening covalency on metal corrosion engineering NiFe-layered double hydroxide electrocatalysts with hard Lewis acid to achieve stable and efficient seawater splitting.

Undesirable adverse reactions caused by chloride ions (Cl-) and the corrosion of active sites are obstacles to the oxygen evolution reaction (OER) in seawater splitting. Herein, we design a molybdate anion (MoO42-)-intercalated NiFe-layered double hydroxide (NiFe-LDH) electrocatalyst and demonstrate that the introduction of MoO42- generates more abundant oxygen vacancies, enhances the M-O covalency, and accelerates the formation of nickel (III) ion (Ni3+) and further oxidation to nickel (IV) ion (Ni4+). Meanwhile, the hard Lewis acid MoO42- exhibits strong selectivity toward OH-, avoiding the competitiveness and corrosiveness of Cl- in seawater. The intercalation of MoO42- modulates the electronic structure of nickel (Ni) and iron (Fe) active sites, optimizing the adsorbate evolution mechanism (AEM) pathway. Simultaneously, moderate activation of lattice oxygen favors the lattice oxygen evolution mechanism (LOM) pathway, facilitating a delicate balance between the AEM and LOM. In a 1.0 M KOH + 0.5 M NaCl electrolyte, the catalyst shows an overpotential of only 224 mV at a current density of 50 mA cm-2 and can operate stably for 1500 h. This work provides a simple and effective method for preparing high-efficiency OER catalysts through corrosion strategies, which can be widely applied to seawater electrolysis.