ZIF-8-derived Cu, N co-doped carbon as a bifunctional cathode catalyst for enhanced performance of microbial fuel cell

The development of bifunctional catalysts is an effective way to simultaneously address the slow kinetics of oxygen reduction reaction (ORR) on the cathode and biofilm contamination in the microbial fuel cells (MFC). Cu-N/C@Cu composites were synthesized as bifunctional cathode catalysts for MFC by doping, adsorption, and two calcinations by using Cu-ZIF-8 as the precursor. The higher Cu-N_x content confers excellent ORR catalytic activity to the optimized Cu-N/C@Cu-2 catalyst. The half-wave potential for Cu-N/C@Cu-2 in a neutral solution is 0.67 V vs. RHE, which is close to that of commercial 20% Pt/C (0.70 V vs. RHE). The maximum power density of the MFCs assembled with Cu-N/C@Cu-2 reached 581 ± 13 mW m^-2, which is even better than that using Pt/C (499 ± 13 mW m^-2). Moreover, the results of antimicrobial activity and biomass test show that the higher Cu content made Cu-N/C@Cu-2 effective against the contamination of cathode biofilm. And the 16S rDNA results find that the community structure of the biofilm is favorable for the power production and purification of MFC. This work shows that copper-based materials can be used as potential bifunctional catalysts to promote MFC applications in wastewater treatment.