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.