Surface engineering strategy to synthesize bicomponent carbons for rechargeable zinc-air batteries

Abstract

Atomic Fe-Nx moieties and nanosized FeCo species anchored on carbons have each been demonstrated to be among the most effective active components for oxygen reduction and evolution reactions (ORR/OER), respectively in rechargeable zinc-air batteries (ZABs). However, incorporating both of these components in a single catalyst presents a great challenge due to the trade-off in formation between them during high-temperature preparation. Herein, we integrate them into a bicomponent carbon through a surface engineering strategy. In this process, K3[Fe(CN)6] is engineered on the surface of a precursor mixture consisting of polyaniline-coated graphene oxide and ZIF-67. This is followed by pyrolysis to produce the bicomponent carbon catalyst of FeCo nanoparticles modified carbon polyhedron (for accelerating the OER), supported on atomically dispersed Fe-N-doped carbon nanosheet (for boosting the ORR). The catalyst exhibits a small potential gap of 0.69 V for OER/ORR. In situ Raman spectroscopy demonstrates that spinel FeCo oxides may be responsible for OER. The use of this catalyst in ZABs achieves high power densities of 225 mW cm−2 in aqueous electrolyte and 164 mW cm−2 in solid-state electrolyte. Additionally, a small and stable voltage gap of 0.712 V at 10 mA cm−2 is maintained after 1035 discharge-charge cycles demonstrating the great application potential in energy devices.