Visible-light-driven Cu₂O/TiO₂ heterojunction photocatalysts for wastewater purification: synthesis, mechanisms and...

Energy shortages and environmental pollution are the most urgent challenges in the contemporary world. Photocatalysis with solar energy for the degradation of pollutants in wastewater provides a promising solution. Cu₂O/TiO₂ heterojunction photocatalysts with wide visible-light harvesting, suitable band alignment and efficient charge carrier separation exhibit great potential for visible-light-driven wastewater purification. This review summaries the controllable synthesis and modification strategies for Cu₂O/TiO₂ heterojunction, aimed at enhancing the degradation activity and structural stability through crystal facet engineering, defect engineering, interfacial coupling and protective coatings. Subsequently, The examination of various preparation methods (e.g., hydrothermal, in-situ growth, deposition), structural characteristics and catalytic performance reveal the influence of microstructural features on light harvesting, charge carrier separation and reaction kinetics. The charge carrier's separation and transport in Type-II, Z-scheme, S-scheme and n-n heterojunctions are compared to reveal the effects of band alignments and built-in electric fields on regulating electrons/holes migration and suppressing interfacial recombination. Finally, the degradation of representative organic pollutants over Cu₂O/TiO₂ photocatalysts is summarized and strategies of optimizing light harvesting, charge separation, and stability are proposed. Furthermore, a design framework of efficient, stable and economical industrial photocatalytic systems is established via optimizing and scaled-up reactors toward practical wastewater treatment.