Iodine-induced formation of C–pyridinic-N–Co sites on carbon-encapsulated cobalt nanocrystals as electrocatalyst for rechargeable Zn-air batteries

Although transition metal and N co-doped carbon (M-N-C) materials are regarded as the promising electrocatalysts for oxygen reduction reaction (ORR), they still suffer from unsatisfactory activity and stability. Herein, a novel strategy for halogen atom inducing the formation of highly active and stable C–pyridinic-N–Co sites is presented. The iodine doped Co-N-C catalysts formed via a chemical vapor deposition process, which shows a high half-wave potential of 0.85 V and remarkable durability. The introduction of iodine not only lowers the d band center of surface Co atoms and also makes the electronic rearrangement of Co-N-C structure. The unique structure promotes O2 adsorption strength and generate of OOH*, accelerating the ORR process on the surface of catalytically active sites surface. Moreover, as an air electrode in rechargeable Zn-air battery, the catalyst shows a large peak power density of 120 mW cm−2 and high stable cyclability. Even as flexible batteries, the cathode exhibits good stability and flexibility under different bending states.