Inorganic-organic hybrid cobalt spinel oxides for catalyzing the oxygen evolution reaction.

Abstract

Fully triggering the deep-seated potential of traditional nanomaterials, such as the classic spinel family, is of paramount importance in the field of materials science, which is yet believed to heavily depend on advanced conceptual designs and synthetic strategies. Herein, a type of inorganic-organic hybrid spinel oxide is designed using a π-conjugated azobenzene single-tooth coordination method to overcome their stubborn problems of moderate activity and phase instability in electrocatalytic reactions. Taking spinel Co₃O₄ nanocubes as a pre-catalyst, after subtle etching of the cube surfaces, some oxygen atoms in the tetrahedral Co-O coordination field are replaced and selectively linked to weakly polar azo-extended π-conjugated units (π*-N=N-π*) via electrophilic carboxyl groups. The π-conjugation structure in Co₃O₄ suppresses the covalency competition between the tetrahedral and octahedral Co-O coordination fields, successfully preventing the phase transition during the electrocatalytic process and improving the electrocatalytic activity and durability. This study not only expands the spinel family but also provides useful guidelines for developing advanced functional materials.