Zinc assisted epitaxial growth of N-doped CNTs-based zeolitic imidazole frameworks derivative for high efficient oxygen reduction reaction in Zn-air battery

Abstract

Development of non-precious metal-based catalysts for substituting precious catalysts as electrocatalytic oxygen reduction reaction (ORR) is crucial for energy devices, such as metal-air batteries and fuel cells. Herein, Co nanoparticles embedded in sea-urchin like N-doped carbon nanotubes (CoZn-NCNTs) composite is constructed by a facile zinc assisted epitaxial growth pyrolytic strategy of bimetallic zeolitic imidazole frameworks (ZIFs)-derived engineering. It does not require the introduction of additional carbon source and reducing ambient. During the pyrolytic process, the formation and decomposition of Co3ZnC accompanied with the volatilization of zinc play important role for the in-situ growth of CNTs. The synergizing of N-doped CNTs and embedded Co nanoparticles structures endows excellent ORR activity of a half-wave potential of 0.82 V, together with superior stability (only 11 mV negative shift for 5000 cycles). It is much higher than the benchmark catalysts respectively derived from zinc- and cobalt-based MOF precursors. A Zn-air battery assembled with CoZn-NCNTs as ORR catalyst delivers a high-power density of 214 mW cm−2, excellent rate capability and outstanding long-term stability with a voltage retention of 99.4%, surpassing state-of-the-art Pt/C catalyst.