Co/Ni dual-metal embedded in heteroatom doped porous carbon core-shell bifunctional electrocatalyst for rechargeable Zn-air batteries

Abstract

Rational construction of highly efficient and cheap bifunctional electrocatalysts to boost both oxygen evolution reaction (OER) and oxygen reduction reaction (ORR) is extremely essential for the wide application of rechargeable metal-air battery. In this work, we design a core-shell structural catalyst of CoNi dual-metal embedded in nitrogen doped porous carbon (NPC, CoNi@NPC), which is developed via the pyrolysis of CoNi-MOFs, assisting by mesoporous SiO₂ to effectively inhibit the aggregation of metal sites. Consequently, the as-prepared CoNi@NPC manifests good ORR activity with half-wave potential up to 0.77 V. Specifically, the CoNi@NPC gives a very low OER over-potential of merely 101 mV in 6 M KOH along with high stability, outperforming the commercial Pt/C-RuO₂. Moreover, the home-made zinc air battery with CoNi@NPC air cathode demonstrates excellent stability over long-term charging–discharging test, and delivers the maximum power density of 224 mW cm⁻². The enhanced high performance of CoNi@NPC bifunctional catalyst for both ORR and OER can be ascribed to its unique core-shell structure and strong synergistic effect between the dual-bimetal active sites and the heteroatom doped carbon. This work opens a new avenue for the rational design of nonprecious metal bifunctional catalysts for rechargeable metal-air battery.