A solar regenerable cathodic electron acceptor for microbial fuel cells

In this study, a high performance and solar regenerable cathodic electron acceptor, I3−, was incorporated into a microbial fuel cell (MFC). Linear sweep voltammetry showed that a current density of 4.2 mA cm−2 can be obtained from the electroreduction of I3−. This value was approximately twice that of ferricyanide (Fe(CN)63−) and was independent of the pH of the electrolyte. The effect of regeneration conditions, such as the pH of the KI solution, KI concentration, oxygen flow rate and the Xe light intensity, on the I3− yield and performance of the MFC was investigated. A sufficient supply of I3− was achieved when the concentration of an air-saturated KI solution was greater than 0.2 M and its pH was around 2.0, under an irradiation higher than 300 mW cm−2. Extended operation of the MFC showed that I3− is capable of supporting the MFC for long-term electricity generation. The maximum power output of the MFC using a catholyte containing 1.2 mM I3− + 0.2 M KI solution was 484.0 mW m−2. This performance was greater than that (307.1 mW m−2) when using a catholyte containing 1.2 mM Fe(CN)63− + 0.2 M KCl solution under the same conditions.