Tracking accelerated oxygen evolution reaction enabled by explosive reconstruction of active species based on Co<sub><i>x</i></sub>N@NC

Abstract

Although tremendous efforts have been devoted to enhancing the electrocatalytic activity and stability of TMN with carbon composites, advances in a detailed study of a strategic method to improve the electrochemical performance of either metal nitrides or carbon are rather limited. Herein, we report a strategic design of hierarchically d-band center modulated cobalt nitride nanoparticles in N-doped carbon nanoboxes (Co/Co4N@NC) in terms of improving the electrocatalytic activity of cobalt nitride and N-doped carbon. The d-band center of Co/Co4N@NC was strategically modulated simply through polydopamine (PDA) coating and nitridation temperature control. The electronically modulated Co/Co4N@NC showed the lowest overpotentials of 262 mV and 408 mV at current densities of 10 mA cm(-2) and 100 mA cm(-2), respectively, with a Tafel slope of 130 mV dec(-1) for the oxygen evolution reaction (OER), which is superior to RuO2 (overpotentials of 284 mV and 470 mV). Furthermore, the density functional theory (DFT) calculations exhibit the Gibbs free energy for each OER step and the density of states (DOS) reveals the modulation of the electronic structure, which identifies the movement of the d-band center boosting the oxygen electrocatalytic performance. Finally, the in situ XANES in an OER mechanism demonstrated that the modulated electronic structure of Co/Co4N@NC electrocatalysts boosts the electrocatalytic activity due to reconstruction of Co2+ into Co3+.