Dual-chamber photocatalytic fuel cell utilizing ZIF-67/PPy composite for enhanced polyvinyl alcohol degradation

A dual-chamber photocatalytic fuel cell (PFC) was constructed using commercial P25 TiO₂ as the photoanode and a zeolitic imidazolate framework-67-polypyrrole (ZIF-67/PPy) composite as the cathode. The incorporation of ZIF-67 into PPy altered the cathodic oxygen reduction reaction from a 4-electron transfer route to a 2-electron pathway, with H₂O₂ as the primary product. Under irradiation, the ZIF-67/PPy composite outperformed both bare ZIF-67 and PPy cathodes, achieving the fastest degradation of polyvinyl alcohol (PVA) in both chambers and the highest photoelectrical conversion performance in the PFC. However, the absence of Fe³⁺ ions in the cathode chamber significantly hindered the degradation rate. Radical quenching tests confirmed the production of OH· radicals during the cathodic reaction, highlighting the role of the Fenton-like reaction between Fe ions and H₂O₂ generated from oxygen reduction reactions, alongside other oxidative species such as O₂^−· and h⁺ from the photocatalytic reaction. In summary, the novel ZIF-67/PPy composite cathode demonstrated excellent performance in wastewater purification, photoelectrical conversion, and long-term stability, making it a promising candidate for practical PFC applications.