Macroporous composite capacitive bioanode applied in microbial fuel cells

Interfacial electron transfer between electroactive biofilm and the electrode was crucial step for microbial fuel cells (MFCs). A three-dimensional multilayer porous sponge coating with nitrogen-doped carbon nanotube/polyaniline/manganese dioxide (S/N-CNT/PANI/MnO₂) electrode has been developed for MFC anode. Here, the S/N-CNT/PANI/MnO₂ anode can function as a biocapacitor, able to store electrons generated from the degradation of organic substrate under the open circuit state and release the accumulated electrons upon requirement. Thus, the mismatching of the production and demand of the electricity can be overcome. Comparing with the sponge/nitrogen-doped carbon nanotube (S/N-CNT) bioanode, S/N-CNT/PANI/MnO₂ capacitive bioanode displays a strong interaction with the microbial biofilm, advancing the electron transfer from exoelectrogens to the bioanode. The maximum power density of MFC with S/N-CNT/PANI/MnO₂ capacitive bioanode is 1019.5 mW/m², which is 2.2 and 5.8 times as much as that of S/N-CNT/MnO₂ bioanode and S/N-CNT bioanode (470.7 mW/m² and 176.6 mW/m²), respectively. During the chronoamperometric experiment with 60 min of charging and 20 min of discharging, the S/N-CNT/PANI/MnO₂ capacitive bioanode was able to store 10743.9 C/m², whereas the S/N-CNT anode was only able to store 3323.4 C/m². With a capacitive bioanode, it is possible to use the MFC simultaneously for production and storage of electricity