Electricity generation and energy storage in microbial fuel cells with manganese dioxide capacitive electrode

A composite manganese dioxide@carbon felt (MnO2@CF) electrode is hydrothermally prepared by loading rod-like MnO2 on the CF. The power density of microbial fuel cell (MFC) with MnO2@CF bioanode (2754.15 mW m−2) is 6.21 times higher than that with CF bioanode. The stored charge of the MnO2@CF bioanode (2625.23C m−2) is 2.82 times higher than that of the CF bioanode (930.81C m−2) by the chronoamperometric tests within a 30 min charging-discharging process. Furthermore, analysis of extracellular polymeric substance (EPS) shows that modification with rod-shaped MnO2 displays a significant positive response and coordination ability to the accumulation and allocation of EPS components of the electrochemical active biofilm matured on MnO2@CF bioanode, especially the aromatic proteins facilitate the extracellular electron transfer. High-throughput sequencing reveals that the dominant phyla on MnO2@CF bioanode are Proteobacteria (40.15%, a well-known electrochemical active microorganism) and Bacteroidetes (22.68%), which contributes to the anaerobic metabolism of electron donors to facilitate the operation of MFC systems. This work shows that modification with MnO2 on the CF precursor significantly improves the capacitance of MnO2@CF electrode and the electrochemical properties of MFCs, which provides an idea for assembling MFCs with highly capacitive bioanodes to generate and store renewable energy simultaneously.