A vertically configured photocatalytic-microbial fuel cell for electricity generation and gaseous toluene degradation.

A vertically configured photocatalytic-microbial fuel cell (photo-MFC) is developed by combining a nanodiamond-decorated ZnO (ZnO/ND) photocathode with a bioanode. The system can effectively couple the light energy with bioenergy to enhance the degradation of volatile organic compounds (VOCs) and boost electricity output. Results show that the composite system exhibits increased performance for toluene removal (60.65%), higher than those of individual parts (ZnO/ND-photocatalysis: 37.16%, MFC: 17.81%). Furthermore, its electrochemical performance is dramatically increased. The peak power density of 120 mW/m and the current density of 1.07 A/m are generated under light illumination, which are about 1.57-fold and 1.37-fold higher than that under dark (76 mW/m, 0.78 A/m), respectively. Microbial community analysis demonstrates Proteobacteria and Firmicute are dominant phyla, implying they play important roles on accelerating the extracellular-electron transfer and toluene degradation. In addition, the underlying mechanism for toluene degradation in the photo-MFC system is preliminary explored. Our results suggest that the photo-MFC has great potential for simultaneous treatment of VOCs with energy recovery.