Ultrathin nitrogen-doped defective carbon layer embedded with NiFe for solid zinc-air batteries

Abstract

Developing a simple oxygen evolution reaction (OER) and oxygen reduction reaction (ORR) bifunctional catalyst construction strategy for zinc-air batteries (ZABs) has been a major challenge. Therefore, this study synthesized an ultrathin nitrogen-doped defective carbon layer embedded with nickel-iron (NiFe) (ZGNiFe@NG) by introducing zinc gluconate to the precursor. In situ generated NiFe nanoparticles facilitated the OER catalyzation kinetics process, nitrogen-doped graphene demonstrated a large specific surface area, providing more active sites to boost electron transfer and mechanical support for the NiFe nanoparticles. Additionally, the introduction of Zn ions can enrich carbon vacancies in the structure of composite catalyst, which is beneficial to the further improvement of catalytic activity. The investigations revealed that the obtained ZGNiFe@NG catalyst possessed a higher ORR half-wave potential of 0.81 V and a lower OER potential of 1.65 V of 10 mA cm−2, presenting a bifunctional catalytic activity toward ORR and OER than that of catalysts lacking the Zn ion precursor. Moreover, as expected, the fabricated solid-state flexible ZAB with ZGNiFe@NG catalyst delivered a high power density of 84.95 mW cm−2 at a current density of 112 mA cm−2 and could operate 65 h steadily. In summary, this work paves a way for designing a carbon matrix with dopants and defects to load NiFe nanoparticles as superior cathode materials of ZABs.