A spherical multishell hollow carbon-based catalyst with a controllable N-species content for the oxygen reduction reaction in air-breathing cathode microbial fuel cells

Abstract

Spherical micro- and mesoporous carbon-based catalysts are often surprisingly effective for the oxygen reduction reaction (ORR). Herein, a self-template strategy was proposed to fabricate a spherical MOF (S-terephthalic acid-MOF, S–Co–Ni–PTA–MOF) via thermal transformation from a crystalline-sheet MOF. The as-prepared spherical MOF with a controllable size has an ultrahigh specific surface area (increased by 2.43 times), abundant pore distribution and good crystallinity. Multifarious morphological, spectral and dimensional techniques were implemented to understand the formation mechanism and influencing factors of the spherical MOF. S–Co–Ni/N–C-T with hierarchical pores yielded a hollow carbon sphere with a complicated surface during carbonization in N₂ with melamine supplementation. Co–Ni and N-doped micro- and mesoporous carbon were applied to enhance the ORR performance to improve the power generation of microbial fuel cells. The MFCs with S–Co–Ni–N–C-850 as a cathode catalyst exhibit excellent power generation with the highest cell voltage output (0.63 ± 0.3 V).