Oxygen reduction reaction activity and the microbial community in response to magnetite coordinating nitrogen-doped carbon catalysts in bioelectrochemical systems.Biosens Bioelectron. 2018 Dec 30; 122:113-120.BB
A Fe-N-C catalyst is supposed to drive commercialization of microbial fuel cells (MFCs) because of its remarkable catalytic performance on oxygen reduction reaction (ORR). However, the catalyst suffers from unclear active site structure and unknown responses of the cathodic microbial community. Here, we prepared a mesoporous core-shell structure catalyst with a nitrogen doped matrix carbon shell, and a Fe3O4 core (Fe3O4@N-mC) as efficient cathode catalysts for the oxygen reduction reaction (ORR). The resulting hybrid electrocatalyst (Fe3O4@N-mC) showed higher limiting current density (2.94 mA cm-2), lower H2O2 yield (7.2-12.7%), and a higher electron transfer number (3.74-3.85) for ORR activity than its intermediates, including Fe3O4, polyaniline (PANI), nitrogen doped carbon (N-C), and magnetic polyaniline composite (Fe3O4@PANI). In MFC tests, Fe3O4@N-mC produced a power density of 0.73 W m-2, which was 2.14 times of N-C (0.34 W m-2), 3.84 times of Fe3O4@PANI (0.19 W m-2), and more than four times of Fe3O4 (4.29, 0.17 W m-2) and PANI (4.87, 0.15 W m-2). Illumina sequencing of 16S rRNA gene amplicons and non-metric multi-dimensional scaling (NMDS) indicated distinct separation of the cathode biofilm bacterial communities between MFCs with different cathodic catalysts. MFCs with the Fe3O4@N-mC cathode facilitated the enrichment of putative exoelectrogenic Dietzia. Our findings suggest that enhancing ORR performance of Fe3O4@N-mC in MFCs can be attributed to the co-effects of Fe and N, the core-mesoporous shell structure, and various nitrogen functionalities.