Photocatalytic fuel cell with cathodic P-BiVO4/CQDs and anodic WO3 for efficient Cr(VI) reduction and stable electricity generation

[Display omitted] •A novel PFC system based on WO3 and P-BiVO4/CQDs was constructed.•Superior Pmax and Cr(VI) reduction were simultaneously realized in the PFC.•Voc, Jsc and Pmax were respectively 0.83 V, 0.42 mA·cm−2 and 0.1 mW·cm−2.•The addition of CQDs remarkably hampered the recombination of charge carriers.•The optimized PFC displayed superior stability and practicability. Developing efficient and sustainable photoelectrodes in photocatalytic fuel cell (PFC) system remains a major challenge. In this work, a PFC system (WO3|P-BiVO4/CQDs) was established based on WO3 photoanode and P-BiVO4 photocathode loaded with carbon quantum dots (CQDs) for Cr(VI) reduction with simultaneous electricity production. The photocatalytic performance of the constructed PFC system was characterized by various analytical methods. With the introduction of CQDs, both Cr(VI) reduction and maximum power density (Pmax) have been significantly enhanced. When the loading amount of CQDs was 150 μL, its Cr(VI) reduction rate and maximum power density (Pmax) were respectively 90 % and 0.10 mW/cm2 within 180 min of illumination, superior to the WO3|P-BiVO4 system. This was attributed to the decoration of CQDs, which broadened the light absorption range, increased the isolation efficiency of charge carriers and ultimately enhanced the ability of the fabricated PFC system. The superior stability and practicability were also demonstrated by five cyclic experiments. In addition, the plausible mechanism was proposed. This work offers an important reference for the application of the PFC system in wastewater treatment.