Simultaneous Tuning Band Gaps of Cu₂ O and TiO₂ to Form S-Scheme Hetero-Photocatalyst

Photocatalytic Z or S scheme merits higher redox potentials and faster charge separation. However, heterostructure photocatalysts with band gaps of bulk materials often have a type I band structure leading to poor photocatalytic activity. In view of this, we report simultaneous tuning of band gaps of Cu₂ O and TiO₂ , where quantum dot Cu₂ O nanoparticles were formed on doped TiO₂ with Ti³⁺ . The reduced size of Cu₂ O made its conduction band more negative, whereas the introduction of Ti³⁺ made the absorption edge red shift to the visible light region. The as-formed heterostructure enabled an S-Scheme mechanism with remarkable activity and stability for visible light photodegradation of 4-chlorophenol (4-CP). The as-obtained photocatalysts' activity demonstrated ca. 510-fold increase as compared to individual ones and a mechanical blend. The as-obtained photocatalysts maintained over 80 % for 5 cycles and 2 months exposure to O₂ did not decrease the degradation rate. ESR characterization and scavenger experiments proved the S-Scheme mechanism.