Enhanced performance of microbial fuel cells using Ag nanoparticles modified Co, N co-doped carbon nanosheets as bifunctional cathode catalyst.

The slow kinetics of oxygen reduction reaction (ORR) and the formation of biofilm on cathode severely limited the performance of microbial fuel cells (MFCs). An efficient way to enhance the power-generation capacity and long-term stability of MFCs is to develop bifunctional catalyst by incorporating the efficient ORR catalysts with antibacterial ingredient. In this study, the Ag/Co-N-C nanosheets were designed and synthesized by decorating Ag nanoparticles (NPs) onto Co-N-C nanosheets, which were prepared from Zn/Co bimetallic metal-organic framework (ZIF-67/ZIF-8) precursor. The Zn/Co ratio, Ag doping amount and the calcination temperature of the precursor were systematically investigated. The optimum sample Ag/Co-N-C-30 revealed the excellent ORR performance with a half-wave potential of 0.80 V vs. RHE, which was slightly lower than that of Pt/C (0.82 V vs. RHE). The MFCs equipped with Ag/Co-N-C-30 cathode exhibited maximum power density of 548 ± 12.6 mW m-2 and superior durability even after 1600 h operation. Besides, the selective antimicrobial ability of Ag/Co-N-C-30 was further explored and the aerobic bacteria in cathode biofilm was found to be obviously inhibited by Ag/Co-N-C-30. The results suggested the Ag/Co-N-C nanosheets can serve as a promising cathode catalyst for practical applications of MFCs.