Graphene-supported Fe/Ni single atoms and FeNi alloy nanoparticles as bifunctional oxygen electrocatalysts for rechargeable zinc-air batteries

The development of inexpensive and high-performance bifunctional electrocatalysts for oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) is of crucial significance for rechargeable metal-air batteries, but remains challenging. Herein, we report an ingenious bifunctional oxygen electrocatalyst integrating ZIF-derived carbon-anchored Fe/Ni single atoms, FeNi alloy nanoparticles, and graphene support (denoted as Fe/Ni-NC||FeNi@G). Synergizing highly active Fe single atoms for the ORR and highly efficient FeNi alloy nanoparticles for the OER, the as-constructed Fe/Ni-NC||FeNi@G catalyst exhibits outstanding bifunctionality; the potential gap between the OER potential at 10 mA cm–2 and the ORR half-wave potential is only 0.618 V, outperforming the benchmark Pt/C + Ir/C catalyst and most transition metal-based bifunctional catalysts reported in the literature. More importantly, the Fe/Ni-NC||FeNi@G-driven zinc-air battery (ZAB) delivers a maximum power density of ∼200 mW cm–2, a specific capacity of 876 mAh g–1, and excellent cycling stability with negligible voltage decay up to 500 hours (3000 cycles). This work provides an effective approach to designing highly efficient non-noble metal multifunctional catalysts for practical applications in rechargeable metal-air batteries.