Recovery of sulfur, generation of electricity and hydrogen peroxide from sulfion-rich wastewater using a novel self-driving photocatalytic fuel cell

A novel photocatalytic fuel cell (PFC) with a sandwich-structure photoanode (ZnS@ZnO/ITO) was fabricated through electrodeposition-calcination to modulate the behavior of charge carriers and improve S^2- oxidation performance, which can effectively recover sulfur and generate electricity and hydrogen peroxide (H₂O₂) from sulfion-rich wastewater. ZnO was locate between ZnS and ITO in ZnS@ZnO/ITO to promote the separation of charge carriers and electron transfer, which can function as an electron transport bridge by forming a type-II heterostructure and acting as an electron transport layer. The PFC system was assembled by integrating ZnS@ZnO/ITO as the photoanode for S^2- oxidation, and graphite (Gr) as the cathode for oxygen reduction, given that Gr exhibits excellent catalytic activity for H₂O₂ generation. In the PFC, the removal efficiency of S^2-, H₂O₂ production, and the maximum power density were 93.4 %, 2.1 mmol/L, and 260 mW/m², respectively. After 24 cycles, the removal efficiency of S^2- and H₂O₂ production maintained 80.0 % and 1.6 mmol/L, respectively. The mechanism for sulfur recovery along with electricity generation and H₂O₂ production was proposed. Moreover, this PFC can effectively treat the actual shale gas wastewater and tannery wastewater, achieving the dual roles of wastewater treatment and resource recovery. This work opens up a brand-new avenue on PFC for purifying wastewater, meanwhile generating electricity and producing H₂O₂.