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 ZIFderived 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 similar to 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.