N‑Doped and CdSe-Sensitized 3D-Ordered TiO₂ Inverse Opal Films for Synergistically Enhanced Photocatalytic Performance

An efficient method for fabricating a novel visible-light-driven photocatalyst by uniformly decorating CdSe nanoparticles on the framework of an N-doped TiO₂ inverse opal (CdSe/N-TiO₂ IO) is reported. Effects of different pore sizes, calcination temperature for nitrogen doping, and loading amount of CdSe nanoparticles are investigated, and the optimal conditions are obtained. The highly ordered mesoporous inverse opal structure exhibits excellent light-harvesting efficiency and fast mass transport. The incorporation of nitrogen into the TiO₂ lattice and sensitization with CdSe nanoparticles effectively decrease the recombination rate of electron–hole pairs. UV–vis DRS reveals that the absorbance edge of CdSe/N-TiO₂ IO is red shifted to the visible-light region, and the band gap is determined to be 2.2 eV. The degradation experiment using RhB as a model substance revealed that the N-doping and CdSe sensitization synergistically enhanced the photocatalytic efficiency of CdSe/N-TiO₂ IO heterostructure by 5.5 times for photocatalytic degradation of RhB in water under visible light. The remarkable photocatalytic ability of CdSe/N-TiO₂ IO can be attributed to the combination of chemical and morphological modifications of TiO₂, which synergistically improve the visible-light absorption ability. The cycling experiments indicate the favorable photostability and excellent cycling stability of CdSe/N-TiO₂ IO. The effects of the active species participated in photocatalytic process have also been tested, and the possible reaction mechanism of degradation of RhB with CdSe/N-TiO₂ IO was investigated. Moreover, the CdSe/N-TiO₂ IO films have good adhesion to FTO glass, which makes it a promising material for photoelectrocatalysis.