Visible-Light Responsive Photocatalytic Fuel Cell Based on WO₃/W Photoanode and Cu₂O/Cu Photocathode for Simultaneous Wastewater Treatment and Electricity Generation

A visible-light driven photocatalytic fuel cell (PFC) system comprised of WO₃/W photoanode and Cu₂O/Cu photocathode was established for organic compounds degradation with simultaneous electricity generation. The central idea for its operation is the mismatched Fermi levels between the two photoelectrodes. Under light illumination, the Fermi level of WO₃/W photoanode is higher than that of Cu₂O/Cu photocathode. An interior bias can be produced based on which the electrons of WO₃/W photoanode can transfer from the external circuit to combine with the holes of Cu₂O/Cu photocathode then generates the electricity. In this manner, the electron/hole pairs separations at two photoelectrodes are facilitated to release the holes of WO₃/W photoanode and electrons of Cu₂O/Cu photocathode. Organic compounds can be decomposed by the holes of WO₃/W photoanode due to its high oxidation power (+3.1–3.2 V_NHE). The results demonstrated that various model compounds including phenol, Rhodamine B, and Congo red can be successfully decomposed in this PFC system, with the degradation rate after 5 h operation were obtained to be 58%, 63%, and 74%, respectively. The consistent operation for continuous water treatment with the electricity generation at a long time scale was also confirmed from the result. The proposed PFC system provides a self-sustained and energy-saving way for simultaneous wastewater treatment and energy recovery.