Enhanced oxygen reduction upon Ag/Fe co-doped UiO-66-NH2-derived porous carbon as bacteriostatic catalysts in microbial fuel cells

As a promising energy storage/conversion technology, the microbial fuel cell (MFC) is generally restricted by the biofouling on the cathode and the sluggish kinetics of oxygen reduction reaction (ORR). Consequently, developing bacteriostatic and high-performance ORR catalysts is critical for the large-scale application of MFC. Herein, we prepare an electrocatalyst of porous octahedral zirconium-based metal organic framework (MOF) UiO-66-NH2 with dispersed Ag and Fe3C nanoparticles (Ag/Fe–N–C) through a facile impregnation and pyrolysis method for an efficient alkaline and neutral ORR. Systematic experimental results demonstrate that the synergistic effect of Ag and Fe can optimize the d-band center of catalyst to boost the interfacial charge transfer, thus resulting in an increased ORR kinetics. As expected, the catalyst with Ag/Fe–N–C-2:1 exhibits outstanding onset potential (1.01 V vs. RHE) and half-wave potential (0.58 V vs. RHE) in neutral electrolyte, which is comparable to Pt/C catalyst. Meanwhile, Ag/Fe–N–C-2:1 indicates obvious antibacterial activity, inhibiting the biofouling on the cathode surface. The MFC with the Ag/Fe–N–C-2:1 as the cathode catalyst can achieve a maximum power density of 1261.1 ± 24 mW m−3, outperforms the MFC with Pt/C (1087.5 ± 14 mW m−3). In summary, Ag/Fe–N–C-2:1 composite can serve as a feasible alternative cathode catalyst for MFC.