Jing Liu¹, Lang Xiao¹, Shankui Luan¹, Shengchang Li¹, Shuo Li¹, Zhangrong Lou², Xuejing Cui¹, Luhua Jiang¹*

¹ College of Materials Science and Engineering, Qingdao University of Science and Technology, Qingdao, Shandong 266042, China.

² Dalian University of Technology, Dalian, 116024, P.R. China

* Corresponding author: luhuajiang@qust.edu.cn (L. Jiang)

Abstract:

Developing low-cost and highly efficient electrocatalysts for oxygen reduction reaction (ORR) is a critical challenge in advancing renewable energy technologies, particularly fuel cells and metal-air batteries. This study, for the first time, demonstrates the incorporation of Bi into Fe, N co-doped carbon shells encapsulating Fe3C (Fe3C@Fe/Bi-NC), resulting in enhanced ORR activity. Physical characterizations and theoretical calculations reveal that the incorporation of Bi-O units into the carbon shell along with the core Fe3C nanoparticles co-modulate the electronic structure of the Fe-N-C active site, while also increasing the electrochemically active surface area. The Fe3C@Fe/Bi-NC catalyst exhibited a half-wave potential E1/2 of 0.87 V, which is higher than that of Fe3C@Fe-NC (0.84 V), Bi-NC (0.73 V), and the commercial 20% Pt/C catalyst (0.86 V). Due to the protective carbon shell, Fe3C@Fe/Bi-NC shows good stability with E1/2 shifting negatively by only 24 mV inalkaline and 33 mV in acidic electrolytes after 5000 cycles. Furthermore, the Fe3C@Fe/Bi-NC-based Zn-Air battery achieves a peak power density of 226 mW cm-2 and a high specific capacitance of 801 mAh gZn-1. The work introduces a novel strategy for engineering core-shell catalysts by modifying the shell structure to significantly improve ORR performance.

Keywords: Oxygen reduction reaction, doping, synergy, Zn-air battery, non-noble catalyst