CoN4 active sites in locally distorted carbon structure for efficient oxygen reduction reaction via regulating coordination environment

Abstract

Adjusting the coordination environment of active sites for oxygen reduction reaction (ORR) is a desired method to realize efficient energy conversion. Herein, we synthesized a single atom Co catalyst (Co-SA/NC) with CoN4 active sites in locally distorted carbon configuration via a coordination-intercalation assisted strategy. The distinctive existing form of CoN4 structure has been confirmed according to X-ray absorption fine spectroscopy. The Co-SA/NC displays satisfactory ORR performance with higher half-wave potential of 0.89 V and kinetic current density (Jk) of 15.4 mA cm−2 at 0.85 V in alkaline solution, than those of Pt/C (0.87 V and 8.7 mA cm−2). Density functional theory calculations demonstrate that locally distorted CoN4 sites are instrumental in adsorption/desorption of oxygen species, promoting the reaction kinetics of ORR. Furthermore, the fast ORR kinetics is proved by small Tafel slope of 57.9 mV/dec. Applying Co-SA/NC as air electrode in Al-air battery, it presents high specific capacity (1992.7 mAh gAl−1) and energy density (2466.7 Wh kgAl−1) at 200 mA cm−2. The electrocatalyst with unique coordination configuration for M-N4 active sites at atomic level will have wide applications in regulating its intrinsic activity.