Optimization of Catalytic Sites in Cobalt‐Modified Nitrogen‐Doped Carbon towards High‐Performance Oxygen Reduction Electrocatalysts for Zinc‐Air Batteries

Abstract

AbstractEfficient yet low‐cost electrocatalysts for the oxygen reduction reaction (ORR) are highly desirable for energy systems such as metal‐air batteries and fuel cells. Herein, we report the synthesis of efficient cobalt‐modified nitrogen‐doped carbon (N−C/Co) electrocatalysts by using a one‐pot pyrolysis. The abundant source of N in g‐C3N4 contributes to the in situ N doping in the carbon matrix, which favors the formation of Co‐related catalytic active sites. The N−C/Co‐1 (prepared with 1 mmol Co salt) sample exhibits the best performance towards the ORR, with a positive half‐wave potential of 0.86 V (vs. the reversible hydrogen electrode, RHE), high stability and excellent methanol tolerance, which outperforms the commercial Pt/C catalyst. We find that the high performance is dependent on the optimal content of Co that can achieve the maximum amount of Co−Nx catalytic species. In addition, we reveal that the size effect of Co nanoparticles is not the determining factor for the ORR activity in the current system, as the kinetics of the ORR reaction is dominantly determined by the active sites derived from Co−Nx species. By exploiting the N−C/Co‐1 sample as an air cathode catalyst, the assembled Zn‐air battery presents a maximal power density of 153 mW cm−2 as well as good durability during continuous cycle tests.