Electricity generation and storage in microbial fuel cells with porous polypyrrole-base composite modified carbon brush anodes

Microbial fuel cells (MFCs) equipped with three-dimensional (3D) electrodes are widely used in wastewater treatment. However, the power output and energy storage of MFCs with 3D anodes are still limited in application. Here, a biocompatible, capacitive, and adhesive polypyrrole, carboxymethyl cellulose, carbon nanotube/carbon brush (PPy-CMC-CNTs/CB) material was prepared, that was integrated into a composite to obtain a high-capacitance 3D anode. An SEM showed that the composite anode had a 3D-macroporous structure that had a large surface area, providing more places for the attachment and growth of microorganisms. The power density of the MFC with a PPy-CMC-CNTs/CB composite anode (2970 mW/m2) was 4.34 times greater than that of an MFC with a bare anode (683 mW/m2). In the tests with a charge for 15 min and discharge for 45 min, it was observed that the stored charge of the bioanode (333 mC/cm2) was 23.67 times higher than that of the bare anode (14.07 mC/cm2). High-throughput sequencing revealed that the modified composite anode had excellent biocompatibility and selective enrichment of electrogenic bacteria. This study provided a simple and environmentally-friendly modification to enable a PPy-CMC-CNTs/CB composite anode to promote energy storage and output performance of MFCs.