Capacitive Bioanodes Enable Renewable Energy Storage in Microbial Fuel Cells

We developed an integrated system for storage of renewable electricity in a microbial fuel cell (MFC). The system contained a capacitive electrode that was inserted into the anodic compartment of an MFC to form a capacitive bioanode. This capacitive bioanode was compared with a noncapacitive bioanode on the basis of performance and storage capacity. The performance and storage capacity were investigated during polarization curves and charge–discharge experiments. During polarization curves the capacitive electrode reached a maximum current density of 1.02 ± 0.04 A/m², whereas the noncapacitive electrode reached a current density output of only 0.79 ± 0.03 A/m². During the charge–discharge experiment with 5 min of charging and 20 min of discharging, the capacitive electrode was able to store a total of 22 831 C/m², whereas the noncapacitive electrode was only able to store 12 195 C/m². Regarding the charge recovery of each electrode, the capacitive electrode was able to recover 52.9% more charge during each charge–discharge experiment compared with the noncapacitive electrode. The capacitive electrode outperformed the noncapacitive electrode throughout each charge–discharge experiment. With a capacitive electrode it is possible to use the MFC simultaneously for production and storage of renewable electricity.