Dodecahedral Ag3PO4 photocatalysis and biodegradation synergistically remove phenol and generate electricity

Microbial fuel cells as a device of treating organic pollutants, have a unique advantage, that is, they can recover energy from those pollutants. However, the energy recovery efficiency is limited when degrading toxic and refractory organic compounds. Here, an MFC assisted by photocatalysis, also known as the photo-MFC, is constructed to improve the decomposition and utilization of phenol for energy recovery. In this photo-MFC, dodecahedral Ag3PO4 is prepared as the photoanode to construct a parallel anode with the TiN bioanode. The synergistic effect between photocatalysis and biodegradation can degrade 89.88 % of phenol and generate a maximum power density of 3.343 W m−2. Not only that, the chemical oxygen demand (COD) removal of the coupled system is 85.36 %, which is much higher than that of the MFC without photoanode (68.21 %) and that of the pure photocatalytic system (38.94 %), reflecting the superiority of the photo-MFC system. Microbial community analysis shows that photocatalysis can increase the abundance of electroactive bacteria, up to 90.698 %, which is much more than that of MFC without photoanode (56.97 %). At the same time, the active bacteria rely on the internal electron transfer pathway of succinate dehydrogenase and cytochrome oxidase Cyta3 and the external electron transfer pathway of riboflavin, c-type cytochromes, flagella, and mediators. Moreover, the possible mechanism of photocatalytic degradation in this photo-MFC is confirmed through electrochemical tests, density-functional theory calculations, and radical trapping experiments.