Fe/Fe3C nanoparticles encapsulated in ZIF-8-derived carbon nanotubes as a cathode oxygen reduction catalyst for microbial fuel cells

Abstract

Insufficient catalytic activity and weak stability of the oxygen reduction reaction (ORR) hinder the efficient and durable operation of microbial fuel cells (MFCs). In this work, an ORR catalyst, Fe/Fe₃C@NiNC, is prepared by one-step pyrolysis using Fe, Ni co-doped ZIF-8 as the precursor. Carbon nanotubes (CNTs) functioned as a protective barrier to encapsulate the Fe/Fe₃C nanoparticles (NPs) to improve the long-term durability of the catalyst. Fe clusters and NiNC associated with CNTs accelerated the electron transfer from Fe to NiNC. Nickel doping optimized the electronic structure, leading to increased pyridinic nitrogen content and enhanced catalyst stability. Fe and Fe₃C synergistically enhanced the ORR activity with a half-wave potential of 0.87 V and an onset potential of 0.95 V. The MFC with Fe/Fe₃C@NiNC showed an excellent power density of 1600 mW m⁻² and a long-term stability of 120 hours. This work offers a strategy for the design of ORR catalysts to improve their catalytic activity and long-term stability.