Photocatalytic fuel cell (PFC), a fuel cell which is capable to produce electricity from organic compounds when irradiated by light, proves to be one of the most promising alternative in energy recovery from organic wastewater. However, numerous studies have been reported on small scale PFC based on the TiO₂ photoanode. A single-chambered PFC which comprised of a zinc oxide (ZnO) photoanode and a platinum loaded carbon cathode was constructed using diazo dye Reactive Green 19 (RG 19) as organic pollutant. Zinc oxide (ZnO) photoanode was fabricated by using anodizing and immobilization method. Efficiency of the photoanodes, for example, the anodized ZnO loaded Zn plate (ZnO/Zn), immobilized ZnO loaded Zn foil (ZnO/Zn) and immobilized ZnO loaded carbon plate (ZnO/C), were investigated. Besides, the fundamental and operating parameter study on the factors governing the performance of PFC such as the effect of photolysis, open and closed circuit, different types of supporting electrolytes, initial dye concentration, pH, light source and dissolved oxygen concentration were evaluated. As compared to photolysis alone, the color removal efficiency of RG 19 was enhanced when ZnO photoanode was employed in the PFC system. The PFC based on anodized ZnO/Zn photoanode showed color removal efficiency with 73 % in 10 mg L-1 of RG 19 after UV irradiation for 8 h, whereas the PFC system using immobilized ZnO/Zn as photoanode yielded complete color removal after 7 h. The increase of initial RG 19 concentration from 10 to 30 mg L-1 had resulted in a reduction of short-circuit current (Jsc) and maximum power density (Pmax) of PFC based on anodized ZnO/Zn photoanode with the presence of supporting electrolytes. Meanwhile, the Jsc and Pmax of PFC based on immobilized ZnO/Zn photoanode increased with increasing initial dye concentration from 5 to 30 mg L-1 and dropped at 40 mg L-1. Electricity generation and degradation efficiency were investigated in the presence of sodium chloride (NaCl), sodium sulfate (Na₂SO₄) and magnesium sulfate (MgSO₄), respectively, as supporting electrolyte in PFC based onanodized ZnO/Zn photoanode. Results revealed that the addition of Na₂SO₄ as supporting electrolyte yielded the highest Jsc of 2.64 mA cm−2 and Pmax of 1.27 mW cm−2. However,in terms of photocatalytic degradation, the presence of NaCl as supporting electrolyte led to the highest dye degradation efficiency. For PFC system based on immobilized ZnO/Zn as photoanode, almost complete decolorization could be achieved in 8 h when 30 mg L-1 of RG19 was treated in a PFC without any supporting electrolyte. Besides, the feasibility of PFC in treating Acid Orange 7 (AO7) and Methylene Blue (MB) using immobilized ZnO/Zn photoanode was investigated too. The effect of dissolved oxygen (DO) concentration on the performance of PFC based on immobilized ZnO/C photoanode in terms of degradation efficiency and electricity generation was investigated. Complete decolorization of RG 19 was accomplished at the end of 8 h when the air flow rate of the PFC was fixed at 200 mL min-1.The presence of dissolved oxygen could efficiently retain the electron-hole pair separation of ZnO and enhanced the degradation efficiency and electricity generation of PFC. In conclusion, the results strongly proved that PFC was able to produce electricity for a long period of time through utilizing light and organic waste as fuel.
