Cobalt (iron), nitrogen and carbon doped mushroom biochar for high-efficiency oxygen reduction in microbial fuel cell and Zn-air battery

Abstract

To improve the oxygen reduction reaction (ORR) kinetics in microbial fuel cell (MFC) and Zn-air battery, cobalt (iron), nitrogen and carbon doped mushroom biochar, i.e. CoNC@MC, FeNC@MC and CoFeNC@MC were prepared using metal-organic frameworks and mushroom as the precursors. The catalysts showed a mesopore-dominant structure with abundant Metal-N, Pyridinic-N and Graphitic-N catalytic active sites. Rotating disk electrode tests revealed that FeNC@MC performed the best ORR activity in neutral and alkaline solutions, which followed the four-electron transfer ORR pathway. Acid leaching could further improve the ORR activity of FeNC@MC in neutral conditions. In MFCs, the FeNC@MC and acid-leached FeNC@MC yielded maximum power densities of 1052.5 mW m−2 and 1126.3 mW m−2 respectively. The above catalysts also produced high power densities of 94.0 mW cm−2 and 93.7 mW cm−2 in the Zn-air battery, with high stability and good methanol tolerance. This article provides a new strategy to prepare low-cost and efficient non-noble ORR catalysts for microbial fuel cell and Zn-air battery.