KOH-promoted in-situ construction of zeolitic imidazolate framework-derived CoO/Co-N-C hybrids jointly boosting oxygen reduction reaction

Abstract

Rational design of advanced cobalt oxides/carbon nanocomposites toward electrocatalytic oxygen reduction has received increasing research attention largely due to the potential synergism between cobalt oxides and carbon support. An efficient CoO/Co-N-C hybrid electrocatalyst has been prepared by high-temperature pyrolysis of ZIF-8 (ZIF = Zeolitic Imidazolate Framework) involving cage-encapsulation of CoCl2 followed by KOH treatment. In the alkaline solution (0.1 M KOH), the optimal CoO/Co-N-C hybrid catalyst (namely C-Co(OH)2@ZIF-8–10%−1000) delivers a half-wave potential (E1/2) of 0.84 V (vs. RHE), and a high four-electron reduction selectivity. The control experiments reveal that the superb ORR activity with C-Co(OH)2@ZIF-8–10%−1000 is jointly contributed by strongly coupled CoO NPs and Co-Nx moieties. Compared to the Pt/C benchmark, C-Co(OH)2@ZIF-8–10%−1000 exhibits comparable ORR performance but better methanol tolerance and electrochemical stability. Besides, the home-made zinc-air battery with C-Co(OH)2@ZIF-8–10%−1000 as the air-cathode catalyst displays an open-circuit voltage of 1.43 V and a maximal power density of 96 mW cm−2.