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

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.