Solar photocatalytic fuel cell using CdS–TiO2 photoanode and air-breathing cathode for wastewater treatment and simultaneous electricity production

• Photocatalytic fuel cell was designed for wastewater treatment and electricity production.
• CdS–TiO2 nanorods were used as effective photoanode for solar photocatalytic fuel cell.
• Air-breathing cathode was first reported in solar photocatalytic fuel cell.
• Our experimental study facilitates quantitative understanding of PFC wastewater treatment.

Solar photocatalytic fuel cell (PFC) is a promising technology for environmental-friendly wastewater treatment and simultaneous production of electricity. In this study, PFC was enhanced by using CdS quantum-dot-sensitized TiO2 nanorod array deposited onto FTO glass as effective photoanode. Moreover, gas diffusion electrode was employed to improve oxygen reduction reaction at the cathode. The material characterization shows that an array of 1.2-μm TiO2 nanorods is decorated with 10-nm CdS quantum dots, which significantly improve solar light harvesting ability. The results of the PFC performance study indicate that light irradiation, acetic acid concentration, electrolyte pH and conductivity have significant influence on the short-circuit current and maximum power density. When the PFC operates at the optimum pH of 4.6, the short-circuit current and maximum power density are 1.79 mA/cm2 and 1134 mW/cm2, respectively. It is found that increasing the electrolyte conductivity is an effective approach to improve the PFC performance. The highest short-circuit current of 5.1 mA/cm2 and maximum power density of 3980 mW/cm2 are obtained with electrolyte having a conductivity of 63.1-mS/cm. In addition, the test results of various pure and practical organic substances in PFC further suggest that it is feasible to use sunlight as a driving force to clean up wastewater with simultaneous electricity production.