Bionic Design of Ni4+ Lewis Acid Site Based on Selective Seawater Oxidation

The side reaction caused by chloride ions and the toxicity to the active site have always been the hindrance to the electrocatalyst of the oxygen evolution reaction (OER) for seawater splitting. Herein, inspired by the early flowering of damaged plants, we designed a catalyst rich in oxygen vacancies (O_vac) and proved that O_vac can accelerate the formation of Ni³⁺ and further oxidize it to Ni⁴⁺, which we named as the "ripening" mechanism of O_vac. O_vac reduces the hydrogen proton desorption energy by regulating local charge redistribution, thus realizing the rapid transformation of Ni²⁺→Ni³⁺→Ni⁴⁺. Meanwhile, the hard Lewis acid Ni⁴⁺ has strong selectivity to OH^-, avoiding the competitiveness and corrosiveness of chloride ions in seawater. This work provides an effective strategy for the simple and rapid construction of self-rebuilding high-valence Ni⁴⁺ electrocatalysts, and is expected to provide guidance for the development of seawater electrolysis.