N/B Co-doped carbon as metal-free cathode catalyst for high-performance asymmetric neutral-alkaline microbial fuel cell.

Microbial fuel cells (MFCs) is a device that uses microorganisms as biocatalysts to directly convert the chemical energy of waste organic into electrical energy. The sluggish kinetics and the high cost of oxygen reduction reaction (ORR) are the major factors hindering the development of MFCs, especially in neutral electrolyte that is widely used in common MFCs. Therefore, it is highly desirable either to explore cheap cathode ORR catalysts with high catalytic activity and stability, or to develop newly MFCs system that can significantly enhance cathode kinetic. In this study, we develop a metal-free N/B-co-doped carbon-based catalyst (denoted as PANI/B-8) by pyrolysis of mixtures of polyaniline and boric acid, which show remarkably improved kinetic and activity toward ORR in alkaline electrolyte relative to neutral electrolyte, inspiring us to develop an asymmetric neutral-alkaline microbial fuel cell (ANA-MFCs) with microbial as neutral anode catalysts and PANI/B-8 as alkaline cathode catalysts, between the two chambers are separated by a proton exchange membrane (PEM) to prevent mixing of anolyte and catholyte while to ensure ion conductivity. The present ANA-MFCs notably deliver an output power density twice higher than that of the symmetric MFCs, thanks to the remarkably enhanced ORR kinetic in alkaline cathode reaction. The asymmetric neutral-alkaline microbial fuel cell with N/B Co-doped carbon exhibits prominent battery performance compared to conventional neutral-neutral device. And it delivers a current value twice higher than that of the symmetric device, thanks to the remarkably enhanced ORR kinetic in alkaline cathode reaction. [Display omitted] [ABSTRACT FROM AUTHOR]