Fe-Nx sites coupled with core-shell FeS@C nanoparticles to boost the oxygen catalysis for rechargeable Zn-air batteries

The development of efficient single-atom catalysts (SACs) for the oxygen reduction reaction (ORR) remains a formidable challenge, primarily due to the symmetric charge distribution of metal single-atom sites (M-N-4). To address such issue, herein, Fe-N-x sites coupled synergistic catalysts fabrication strategy is presented to break the uniform electronic distribution, thus enhancing the intrinsic catalytic activity. Precisely, atomically dispersed Fe-N-x sites supported on N/S-doped mesoporous carbon (NSC) coupled with FeS@C core-shell nanoparticles (FAS-NSC@950) is synthesized by a facile hydrothermal reaction and subsequent pyrolysis. Due to the presence of an in situ-grown conductive graphitic layer (shell), the FeS nanoparticles (core) effectively adjust the electronic structure of single-atom Fe sites and facilitate the ORR kinetics via short/long-range coupling interactions. Consequently, FAS-NSC@950 displays a more positive half-wave potential (E-1/2) of 0.871 V with a significantly boosted ORR kinetics (Tafel slope = 52.2 mV dec(-1)), outpacing the commercial Pt/C (E-1/2 = 0.84 V and Tafel slope = 54.6 mV dec(-1)). As a bifunctional electrocatalyst, it displays a smaller bifunctional activity parameter (Delta E) of 0.673 V, surpassing the Pt/C-RuO2 combination (Delta E = 0.724 V). Besides, the FAS-NSC@950-based zincair battery (ZAB) displays superior power density, specific capacity, and long-term cycling performance to the Pt/C-Ir/C-based ZAB. This work significantly contributes to the field by offering a promising strategy to enhance the catalytic activity of SACs for ORR, with potential implications for energy conversion and storage technologies. (c) 2023 Science Press and Dalian Institute of Chemical Physics, Chinese Academy of Sciences. Published by ELSEVIER B.V. and Science Press. All rights reserved.