Design of Cu–Ce co-doped TiO₂ for improved photocatalysis

The fast recombination of photo-generated conduction band electrons (e _cb ⁻ ) and valance band holes (h _vb ⁺ ) of TiO₂ results in an unsatisfactory photocatalytic performance for organic degradation. To increase the efficiency of charge separation, TiO₂ was modified by Cu–Ce co-doping considering the better redox properties of copper–ceria oxide with respect to the single oxide, i.e., an easier electron capturing ability. An optimal Cu–Ce co-doped TiO₂ with the initial molar ratio of Cu/Ce at 3:1 was prepared by a hydrothermal method with the aim to greatly promote the charge separation, and characterized by XRD, BET, DRS, PL, HR-TEM, and XPS techniques. Upon ultraviolet light irradiation, it exhibits significantly enhanced photocatalytic activity, about 5.8 times that of Ti–HF. The presence of Cu²⁺ and Ce³⁺/Ce⁴⁺ benefits electrons captured by molecular oxygen, while an increased hydroxyl groups upon Cu–Ce co-doping consume more holes, resulting in prolonged lifetime of photo-generated carriers. Moreover, it is proved that electron transfers preferably from conduction band (CB) of TiO₂ to CB of CuO and then to nearby CeO₂.