Solar-Driven Photoreactor for Water Remediation Based on n‑Type TiO₂ and p‑Type Ag/AgBiW₂O₈/Bi₂WO₆ Light-Responsive Air-Fed Gas Diffusion Electrodes

Photocathodes with multiphasic Ag/AgBiW₂O₈/Bi₂WO₆ (Ag/ABW/BW) particles, obtained by hydrothermal synthesis, were evaluated for light-assisted oxygen reduction reaction (ORR). Under irradiation, electrodes of Ag/ABW/BW deposited on FTO exhibited ORR cathodic photocurrent enhancement and impedance decreasing (p-type semiconducting behavior). The Ag/ABW/BW particles were deposited on graphite sintered with PTFE; under irradiation and flow of compressed air, this gas diffusion electrode (GDE) produced H₂O₂ from ORR. The air-fed GDE|Ag/ABW/BW photocathode was associated with an FTO|TiO₂ photoanode and externally connected with a silicon solar cell. Irradiated by a solar simulator, this photoreactor was used for remediation of amoxicillin (AMX) aqueous solution. After 3 h, 53% of AMX was degraded, while with a bare GDE, the AMX removal was 30%. Smaller values (<15%) were obtained using Pt or a GDE|Ag/ABW/BW under N₂ flow as the cathode, since these configurations preclude the H₂O₂ production from ORR. Thus, association of photoactive electrodes in this innovative solar-driven photoreactor provides a sustainable system for water remediation.