Facilely Prepared Carbon Dots as Effective Anode Modifier for Enhanced Performance of Microbial Fuel Cells.

Microbial fuel cells (MFCs) are a promising technology for obtaining energy in wastewater. Effective extracellular electron transfer is one of the key factors for its practical application. In this work, carbon dots (CDs) enriched with oxygen-containing groups on the surface were synthesized as an efficient anode modifier using a simple hydrothermal method and common reactants. The experimental findings indicated that anodes modified with CDs exhibited increased electrical conductivity and greater hydrophilicity. These modifications facilitated increased microorganism loading and contributed to enhancing electrochemical processes within the anode biofilm. The CD-modified MFCs exhibited higher maximum power density (661.1 ± 42.6 mW·m-2) and open-circuit voltage (534.50 ± 6.4 mV), which were significantly better than those of the blank group MFCs (484.1 ± 14.1 mW·m-2 and 447.50 ± 12.1 mV). The use of simple carbon materials to improve the microbial loading on the MFCs anode and the electron transfer between the microbial-electrode may provide a new idea for the design of efficient MFCs.

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-Nx 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.