Photocatalytic NO_x removal with TiO₂-impregnated 3D-printed PET supports

In this work, we investigated the photocatalytic removal of NO_x using 3D-printed supports. Monolithic supports with internal channels were fabricated by Fused Modelling Deposition (FDM) using PET as the filament feedstock. The printing parameters of the supports were optimized to maximize the exposure of the photocatalyst to UV light throughout the monolithic PET printed supports. The removal experiments were carried out in a continuous gas phase flow reactor, which was custom designed in-house incorporating a 3D printed PET support impregnated with TiO₂ as photocatalyst. The impregnated and non-impregnated supports were characterized by diffuse reflectance spectrometry, SEM and AFM. The effect of several key-factors on the NO_x removal capacity was investigated, including the type of PET filament (native recycled, BPET vs. glycol-modified, PETG), the type of TiO₂ (P25 vs. Hombikat UV-100), the UV light source (LED vs. tubular lamps), and the number of deposited TiO₂ layers. The highest NO and NO_x removal were achieved by using PETG supports coated with a single layer of Hombikat UV-100 and irradiating the flat reactor from both sides using two sets of black light lamps. However, the highest selectivity toward nitrate formation was obtained when using P25 under the same experimental conditions. This work demonstrates that 3D printing is a reliable and powerful technique for fabricating photocatalytic reactive supports that can serve as a versatile platform for evaluating photocatalytic performance.