Soft-template assisted synthesis of Fe/N-doped hollow carbon nanospheres as advanced electrocatalysts for the oxygen reduction reaction in microbial fuel cells

Heteroatom-doped hollow carbon nanospheres (HCNs) have drawn significant attention as alternative catalysts towards the oxygen reduction reaction (ORR). However, the simple and environmentally friendly synthesis of heteroatom-doped HCNs is a great challenge. Herein, an Fe/N-doped porous HCN (Fe/N-HCN) has been fabricated via a simple pyrolysis method using one-step synthesized poly(aniline- co -pyrrole) copolymer hollow nanospheres as precursors. The prepared Fe/N-HCN exhibited excellent ORR activity (onset potential of 0.02 V and half-wave potential of −0.12 V vs. Ag/AgCl), comparable to that of the Pt/C catalyst (onset potential of 0.01 V and half-wave potential of −0.14 V vs. Ag/AgCl) and superior to those of most of the reported noble metal-free carbon catalysts with hollow structures. The catalytic proficiency of the as-prepared catalyst was attributed to the abundant N and Fe atoms within the carbon lattice and a high surface area due to its hollow morphology. The as-prepared Fe/N-HCN also exhibited remarkable ORR activity in neutral solution, displaying potential application as a cathode catalyst in a microbial fuel cell (MFC). A maximum power density of 1300 ± 64 mW m −2 was achieved from an MFC equipped with the resultant Fe/N-HCN cathode, which outperformed that of the MFC with a Pt/C cathode. In this study, we reported a new approach for the production of Fe/N-doped carbon materials with a hollow morphology that exhibited high performance towards ORR.