Light Fuel Cell (LFC): A Novel Device for Interpretation of Microorganisms-Involved Mineral Photochemical Process

Abstract

Geophotocatalysis of natural semiconducting minerals plays key roles in driving redox reactions on the earth's surface. Whether it is related to microbial metabolism remains unknown. This study proposed a novel device, light fuel cell (LFC) to investigate a new aspect of microbe-mineral interactive pathway involved by both microorganisms and semiconducting minerals. When using O2 as the cathodic electron acceptor, the volumetric power density of a LFC with a microbial anode and a visible light-irradiated rutile-cathode was 12.1 W/m3, 1.6 times higher than that obtained in the dark (7.5 W/m3). Electrochemical impedance spectroscopy (EIS) data indicated that the cathodic polarization resistance of the LFC in light was 196 Ω, while that operated in the dark was 2820 Ω. These results manifested the bio-photo-electrochemically interactive pathway between the microorganisms and semiconducting minerals, in which the semiconductor photocatalysis significantly improved the electron transfer efficiency. A thorough investigation was then performed on a LFC to evaluate the parameters such as catholyte pH, electron acceptor concentration, equipment configuration, electrode preparation method and the type of semiconducting minerals that affected its performance. The results reported in this study showed that further improvements of LFCs with the special purpose of minimizing ohmic resistances, maximizing solar to chemical energy conversion efficiency and enhancing the rates of photocatalytic reaction, will finally lead to potential applications of LFCs in wastewater treatment.