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.