Superiority of boron, nitrogen and iron ternary doped carbonized graphene oxide-based catalysts for oxygen reduction in microbial fuel cells

The exploration of highly active and cost-effective catalysts for the oxygen reduction reaction is vitally important to facilitate the improvement of metal–air batteries and fuel cells. Herein, super-active catalysts made from an interesting metal–polymer network (MPN) that consist of Fe–Nx–C, B–N and Fe3O4/Fe3C alloys were prepared via facile one-pot carbonization. The achieved catalysts possessed an amazing porous structure that was derived from the MPN with the assistance of a “bubble-template”. Remarkably, the content of highly active Fe–Nx–C can be regulated by introducing graphene, and the ORR activity of the catalyst was enhanced dramatically with an increase in the Fe3O4/Fe3C alloy content. The most active BNFe–C–G2 catalyst exhibited superior ORR activity/stability, and was then employed as an air cathode electrocatalyst in a microbial fuel cell. The results showed that the output voltage and power density of BNFe–C–G2 were significantly improved to 575 ± 11 mV and 1046.2 ± 35 mW m−2, respectively. These values are 4.5% and 44.44% higher than those of commercial Pt/C. Thus, due to the synergistic electrocatalysis of the Fe–Nx–C, B–N and Fe3O4/Fe3C alloys, the super-active and low-cost BNFe–C–G2 material should be a promising ORR catalyst for application in biofuel cells, and in many other energy conversion and storage devices.