▎ 摘　　要

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-N-x-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-N-x-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-N-x-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.