Ag nanowires boost graphene aerogel as anode for charge-transfer in nonclassical electroactive microbial fuel cells

Abstract

Microbial fuel cells (MFCs) convert chemical energy stored in organic matter into electrical energy through the electrochemical action of microorganisms, making them highly relevant for wastewater treatment. However, the efficiency of generating bioelectricity using nonclassical electroactive bacteria such as Escherichia coli (E. coli), which commonly exist in the waste water, remains rather low. Herein, we improve the performance of MFCs by using graphene aerogel (GA) with dispersed Ag nanowires (AgNWs) as the anode material. Introducing AgNWs into GA lowers the charge-transfer resistance of the electrode and enhance the electrochemical active surface area (ECSA), which improves charge transfer efficiency of MFCs. However, the high release of Ag⁺ from AgNWs and overactive charge-transfer can inhibit the bacterial activity, which compromises the operation of MFCs. Hence, the GA/AgNWs need to be optimized to minimize charge-transfer resistance while preserving bacterial activity. It is demonstrated that the power density of the MFC using GA with 1 wt% AgNWs reaches 0.98 mW/cm², which is 60 % higher than the best-reported value of MFCs using carbon–metal composites. The results pave a new avenue for improving MFCs performance.