Investigation of the photoelectric properties of nanostructured CeO2/Cu2O heterojunction: Photocatalytic degradation of sulfadiazine in water

The rapid complexation of photogenerated electrons–holes with copper (Cu) greatly limits the large-scale application of cuprous oxide (Cu₂O) as a photocatalyst. Therefore, using a hydrothermal method, a type Ⅱ heterojunction structure was constructed by modifying Cu₂O with cerium (IV) oxide (CeO₂). The CeO₂/Cu₂O heterojunction photocatalyst effectively increased the photogenerated electron density and reduced the surface transfer impedance. The improved separation of photogenerated electron–hole pairs resulted in excellent photocatalytic activity. Consequently, the sulfadiazine (SDZ) degradation rate by CeO₂/Cu₂O reached 87.5%. Furthermore, after five cycles, the SDZ degradation rate remained as high as 78.5%, demonstrating the good stability of CeO₂/Cu₂O. The SDZ degradation intermediates were analyzed using high–performance liquid chromatography–tandem mass spectrometry, and possible degradation pathways were proposed. Trapping agent experiments, and energy band structure calculations revealed that CeO₂/Cu₂O photocatalyzes SDZ degradation via a type Ⅱ heterojunction charge transfer mechanism. Finally, the total organic carbon showed that SDZ eventually decomposed to CO₂ and H₂O, with complete SDZ degradation. This study provides a reference for the preparation of visible light–responsive photocatalysts.