Synergetic FeCo nanorods embedded in nitrogen-doped carbon nanotubes with abundant metal–NCNT heterointerfaces as efficient air electrocatalysts for rechargeable zinc–air batteries

Commercialization of rechargeable zinc–air batteries (ZABs) is blocked by low stability and battery performance. Herein, we synthesized a series of cobalt/iron nanorods embedded into nitrogen-doped carbon nanotubes and utilized them as air electrodes for rechargeable ZABs. The electrochemical results suggest that the FeCo-alloyed structure exhibits better stability and electrocatalytic activities toward the oxygen evolution reaction (OER) and oxygen reduction reaction (ORR) than the Fe-NR/NCNT and Co-NR/NCNT. This is ascribed to the presence of more metal–NCNT heterointerfaces, resulting in more active sites for catalyzing ORR and OER. The Fe0.33Co0.67-NR/NCNT requires only 285 mV overpotential to deliver 10 mA cm−2 in the OER catalysis indicating a better catalytic activity compared to Co-NR/NCNT (298 mV) and Fe-NR/NCNT (363 mV) as well as the benchmark of the IrO2 (313 mV). Moreover, Fe0.33Co0.67-NR/NCNT with a half-wave potential of 857 mV vs. RHE (comparable to commercial Pt/C (853 mV vs. RHE)) outperforms Fe-NR/NCNT (842 mV vs. RHE) and Co-NR/CNT (839 mV vs. RHE). Consequently, the assembled rechargeable ZAB from Fe0.33Co0.67-NR/NCNT (164 mW cm−2) exhibits higher battery performance and stability than Co-NR/NCNT (70 mW cm−2), Fe-NR/NCNT (89 mW cm−2) and Pt/C–IrO2 (71 mW cm−2). Furthermore, the all-solid-state ZAB fabricated from Fe0.33Co0.67-NR/NCNT shows a considerably high battery performance (54 mW cm−2) and stability.