High-density defects in ordered macroporous-mesoporous CoNiFe-LDHs for efficient and robust oxygen evolution reaction

As a result of the agglomeration of layered double-metal hydroxides (LDHs), their electrocatalytic activity of oxygen evolution reaction (OER) is usually suppressed. Herein, we propose simple co-precipitation and surface etching for the preparation of ordered macroporous-mesoporous CoNiFe-LDHs with high-density defects. The ordered structure avoids the agglomeration of single-layer nanosheets. Meanwhile, the high-density defects on the nanosheet surface generate abundant metal vacancies and oxygen vacancies, distorting the single-layer nanosheets significantly and altering the electronic properties around the metal (M)–M and M–O bonds, which enhances the adsorption of intermediates and accelerates the rate-controlling reaction step of O∗ → OOH∗. This new material shows an extremely low overpotential of 197 mV at a current density of 10 mA cm−2 and a surprising stability of over 70 h in alkaline media. This work provides a new synthesis protocol for hierarchical porous LDHs with excellent OER catalytic activity.