Efficient Degradation of Trimethylamine via Vacuum Ultraviolet Irradiation with Morphology-Tuned CeO₂

Trimethylamine (TMA) is a common malodorous compound that poses serious environmental and health risks. Four different structures of cerium oxide (CeO2), namely, cubes, hollow spheres, octahedrons, and spindles, were successfully synthesized via a hydrothermal method and then used for TMA degradation in a vacuum ultraviolet photocatalytic oxidation system. All the synthesized catalysts exhibited enhanced activity compared with commercial CeO2. The hollow-sphere CeO2 demonstrated high catalytic performance, achieving 75.9% mineralization of TMA within 90 min and substantially reduced ozone generation (stable 0 ppm in outlet). Additionally, the total outlet concentration of secondary nitrogenous pollutants (NOx and NH3) remained below 2.5 ppm. In situ infrared spectroscopy was employed to elucidate the degradation pathway of TMA under vacuum ultraviolet irradiation, comparing sphere CeO2 with commercial CeO2. The superior TMA degradation performance of the hollow-sphere CeO2 was attributed to its higher Ce3+ ratio as well as increased oxygen, increased charge separation efficiency, and radical generation. This study provides new insights into the optimization of CeO2-based photocatalysts to efficiently degrade TMA and offers promising solutions for odor control and environmental protection.