Fe-N-C-based cathode catalyst enhances redox reaction performance of microbial fuel cells: Azo dyes degradation accompanied by electricity generation

Microbial fuel cell (MFC) is a promising technology for the treatment of textile industry wastewater and energy recovering. However, insufficient power for redox reaction and costly cathode catalyst limit the application of MFCs. Herein, we proposed an environmentally friendly and convenient approach for Fe-N-C-based catalysts synthesis and confirmed their satisfactory effects. The results showed that graphitized structures, pyridine-N and graphitic-N enhanced the conductivity of pomelo peel-derived carbon (PPC). In addition, the existence of Fe3C nanocrystals, Fe-N-x active sites and the rod-like carbon nanotubes (CNTs) was favorable for the synthetic catalyst. Meanwhile, the effective removal of Congo Red (CR) (99.0%) and COD (86.6%) was achieved at the precursor mass ratio was 2 under neutral conditions, accompanied by a maximum power output of 184 mW center dot m(-2). It was clarified that electrons preferentially break the azo bond (-N = N-) of CR and the intermediates mainly included the benzene ring and the naphthalene ring. Microbial community analysis showed that Proteobacteria (56.5%), Gammaproteobacteria (44.6%) and Acinetobacter (29.5%) dominated at the phylum, class and genus levels of the anodic biofilm, respectively. In general, this study provides an innovative substitute for cathode catalyst in MFCs and the synthesized Fe-N-C-based catalyst could be widely employed in engineering owing to its admirable intrinsic activity.