Dual-Phasic Carbon with Co Single Atoms and Nanoparticles as a Bifunctional Oxygen Electrocatalyst for Rechargeable Zn-Air Batteries

The great interest in rechargeable Zn-air batteries (ZABs) arouses extensive research on low-cost, high-active, and durable bifunctional electrocatalysts to boost the sluggish oxygen reduction reaction (ORR) and oxygen evolution reaction (OER). It remains a great challenge to simultaneously host high-active and independent ORR and OER sites in a single catalyst. Herein a dual-phasic carbon nanoarchitecture consisting of a single-atom phase for the ORR and nanosized phase for the OER is proposed. Specifically, single Co atoms supported on carbon nanotubes (single-atom phase) and nanosized Co encapsulated in zeolitic-imidazole-framework-derived carbon polyhedron (nanosized phase) are integrated together via carbon nanotube bridges. The obtained dual-phasic carbon catalyst shows a small overpotential difference of 0.74 V between OER potential at 10 mA cm(-2) and ORR half-wave potential. The ZAB based on the bifunctional catalyst demonstrates a large power density of 172 mW cm(-2). Furthermore, it shows a small charge-discharge potential gap of 0.51 V at 5 mA cm(-2) and outstanding discharge-charge cycling durability. This study provides a feasible design concept to achieve multifunctional catalysts and promotes the development of rechargeable ZABs.