Photoactivated Fe(III)/Fe(II)/WO₃–Pd fuel cell for electricity generation using synthetic and real effluents under visible light

Solar energy exploitation is one of the most challenging applications for sustainable energy production. In this work a photoactivated fuel cell was developed, using visible light and the Fe(III)/Fe(II) redox couple for the simultaneous production of electrical energy and oxidation of polluting organics (alcohols) contained in synthetic and real wastewaters. WO₃ was selected as a cheap and environmentally friendly photocatalyst more efficient than TiO₂ (i) under visible light irradiation and (ii) in the presence of in-situ photodeposited Pd. Pd photodeposition was found to reduce the band gap of bare WO₃, thus increasing visible light capture and limiting the occurrence of photogenerated hole/electron recombination. Higher photocatalytic performances were recorded over WO₃–Pd compared to TiO₂ and bare WO₃, despite the low BET superficial area of WO₃–Pd (2.34 m² g⁻¹). Optimal conditions were identified at pH = 2.0 with 2% w/w Pd load. The results also evidenced the influence of the selected sacrificial organics and water matrices. A quantum yield of 84.89% and an energy efficiency of 4.15% were the best results achieved so far for the proposed system. The present photoelectrochemical cell offers a very promising system for electrical energy production by using wastewater from wine manufacturing industry and solar light radiation.