Performance of an air-cathode microbial fuel cell under varied relative humidity conditions in the cathode chamber

The performance of an air-cathode microbial fuel cell (MFC) with a cap arrangement was significantly affected by humidity conditions in the cathode. An MFC at a relative humidity (RH) of 88% produced a highest cell voltage of 0.42 V (600 Ω) compared to other operations at 50% (0.34 V) and 30% (0.29 V) RHs. During polarization analysis, MFC operation at 88% RH produced a maximum power density of 0.377 W/m² (a current density of 1.5 A/m²), which was 1.8 and 2.9 times higher than with 50% and 30% RHs, respectively. Cyclic voltammogram analysis revealed a higher reduction current of − 0.073 A with 88% RH. Furthermore, no increase in dissolved oxygen concentration in the anode chamber was observed with 88% RH. This result suggests that control of humidity conditions in cathode chamber could maximize power generation from an air-cathode MFC.