Feasibility study of municipal wastewater removal synchronized with electricity generation via solar-driven photocatalytic fuel cell with Bi2WO6/ZnO nanorods array photoanode

The reclamation of energy from municipal wastewater treatment process is highly demanded and could resolve the two most formidable dilemmas of water pollution and energy crisis nowadays. In this study, a photocatalytic fuel cell (PFC) utilizing a Z-scheme heterojunction Bi2WO6/ZnO nanorod arrays (NRAs) photoanode was employed for efficient municipal wastewater treatment and electricity generation simultaneously under sunlight irradiation. Various characterization techniques, including energy dispersive X-ray (EDX), field-emission scanning electron microscopy (FESEM), X-ray diffraction (XRD), electrochemical impedance spectroscopy (EIS), transient photoresponse (TPR), and linear sweep voltammetry (LSV) were used to analyze the physical, chemical and photoelectrochemical characteristics of the as-synthesized photoanode. The results indicated that the Z-scheme heterojunction Bi2WO6/ZnO NRAs exhibited the excellent photocatalytic performance under sunlight irradiation as compared to pristine ZnO NRAs. Ergo, the PFC system achieved complete removal of COD and produced 3.30 μW cm−2, 37.10 μA cm−2 and 563 mV of maximum power density (Pmax ), short-current density (Jsc) and open-circuit voltage (Voc) within 4 h of sunlight irradiation, respectively. The boosted photoactivity was ascribed to the successful formation of the Z-scheme hybridization interface betwixt the Bi2WO6 and ZnO NRAs, that not only enhanced the visible light adsorption of ZnO NRAs, concomitantly significantly accelerated the spatial charge separation and restrained the electron-hole pair recombination.