Boosting the oxygen evolution activity over cobalt nitride nanosheets through optimizing the electronic configuration

The electronic configuration plays a crucial role in the activity of catalyst toward OER according to Shao-Horn’s principle. Herein, we demonstrated a facile strategy to modulate the electrons of doubly degenerated (eg) orbital for Co ions in Co4Nx (0 < x < 1) nanosheets via simply altering the N content for the enhanced OER catalytic activity. The decrease of N content in Co4Nx nanosheets accompanied with the increased number of eg electrons of Co ions. When the x value was 0.82, the eg electrons was successfully tuned to 1.18, which was close to the optimal configuration of 1.2. Accordingly, the Co4N0.82 nanosheets exhibited a remarkable activity toward OER, with an extremely low overpotential of 190 mV at the current density of 10 mA cm−2. A mechanistic study demonstrates that the decrease of N content gave rise to the decreased energy barrier of *OH oxidation in OER process, which was responsible to the boosted OER performance.