Oleyl Phosphate-Modified Crystalline-Amorphous TiO2/Ce2O3 heterojunction nanoparticles with significantly reduced photocatalytic activity as stable UV-Shielding fillers

As a stable and inexpensive UV-absorber, TiO2 is widely used in UV-shielding products. However, its poor compatibility with matrix polymers and photocatalytic degradation hazard still limit its performance. Herein, we construct the crystalline-amorphous TiO2/Ce2O3 heterojunctions with an average size of 15 nm via an in-situ solvothermal process, significantly reducing the photocatalytic activity through the carrier redistribution be-tween TiO2 and Ce2O3. In the photocatalytic experiments for the degradation of three dyes (RhB, MB, and RR-120), the apparent reaction rate constants (k) of the optimal sample TiO2/Ce2O3-3 % are 33.92, 28.54, and 24.78 times lower than those of pure TiO2, respectively. The characterizations and theoretical calculations together reveal that the photogenerated carriers accumulate on the amorphous Ce2O3 with rich defects, promoting the recombination of electron-hole pairs and reducing the carriers' redox potential. Additionally, oleyl phosphate (OP) is used for surface modification to achieve TiO2/Ce2O3 organic solvent-dispersible and improve its compatibility with matrix polymers, thus the UV-shielding OP-TiO2/Ce2O3/fluorocarbon hybrid coating is pre-pared with high transparency.