Visible-light-enhanced Cr (VI) reduction and bioelectricity generation at MXene photocathode in photoelectrocatalytic microbial fuel cells

Photocatalysis coupled with microbial fuel cell (Photo-MFC) is a promising technology that can be applied for reducing pollutants (e.g. hexavalent chromium (Cr (VI)) while generating power with wastewater by photocathode under visible light. However, exploring effective and inexpensive catalysts for enhancing the photocathode performance is a challenge in a Photo-MFC system. Herein, ultrathin MXenes (Ti3C2) nanosheets were fabricated through ultrasonic etching of Ti3AlC2 for photocathode catalysts, and the reduction of Cr (VI) was also investigated by MXenes-modified photocathode under visible light. The result shows that the efficiency for the Cr (VI) reduction is approximately 72.84% in 72 h, and higher than that under dark condition (63.77%) or the one without MXenes cathode (60.45%). The maximum power density of Photo-MFC with MXenes-modified photocathode under visible light is 702.67 mW·m−2, which is higher 41.95% than that in the traditional MFC without MXenes cathode (495.02 mW·m−2). In addition, with initial concentration of 40 mg/L at pH 3, the Cr (VI) reduction efficiency of Photo-MFC could be as high as 100% after treating for 60 h under visible light. This study provides a train of thought for removing Cr (VI) pollution in the water environment.