Selective surface nitridation of the self-supported Co oxide nanobushes catalytic electrode towards efficient oxygen evolution reaction

Oxygen evolution reaction (OER) with four-electron process is the bottleneck of water electrolysis to produce hydrogen. In this work, selective surface nitridation of the self-supported Co oxide nanobushes was conducted to form the Co5.47N@Co oxide nanobushes catalyst electrode for OER. During the surface thermo nitridation, the N atoms replaced the sites of O atoms, causing lattice expansion/distortion along with rich oxygen vacancies. Besides, the nitridation promoted the charge transfer on the catalysts surface. As a result, the electronic states of the Co centers were modified and their catalytic activities towards OER were optimized. Combined with the DFT calculations and the experimental results, it was suggested that compared with the Co oxide nanobushes, the intermediates evolution during OER process was more spontaneous in the Co5.47N@Co oxide nanobushes electrode and their charge transfer resistance was greatly reduced, which displayed excellent OER performances in alkaline electrolyte, with the overpotentials of 208/287 mV at the current densities of 10/100 mA cm-2 and stabilized at the high current density of 100 mA cm-2 for over 20 h.