Influence of the thickness of the capacitive layer on the performance of bioanodes in Microbial Fuel Cells

Abstract

Earlier it was shown, that it is possible to operate a Microbial Fuel Cell with an integrated capacitive bio-anode with a thickness of 0.5 mm and thereby to increase the power output. The integrated capacitive bioanode enabled storage of electricity produced by microorganisms directly inside an MFC. To increase the performance of this integrated storage system even more; the thickness of the capacitive electrode was varied: 0.2 mm, 0.5 mm and 1.5 mm. Each of these capacitive electrodes was tested in the MFC setup during polarization curves and charge–discharge experiments for the steady-state current density and the maximum charge recovery.The capacitive electrode with a thickness of 0.2 mm outperformed the other electrodes in all experiments: it reached a maximum current density of 2.53 Am−² during polarization curves, and was able to store a cumulative total charge of 96013 cm−² during charge–discharge experiments. The highest relative charge recovery for this electrode was 1.4, which means that 40% more current can be gained from this capacitive electrode during intermittent operation compared to continuous operation of a noncapacitive electrode. Surprisingly it was possible to increase the performance of the MFC through decrease of the thickness of the capacitive electrode.