High-Efficiency Photocatalytic Reactors Fabricated via Rapid DLP 3D Printing: Enhanced Dye Photodegradation with Optimized TiO₂ Loading and Structural Design

The photocatalytic degradation of organic compounds is seen as a pivotal water treatment technology. While 3D printing has been proven to directly produce photocatalytic reactors, research in this area, especially utilizing mass-production-capable vat photopolymerization (VP)-based 3D printing, remains in its early stages. This study aimed to prepare high-solid content printing slurries (up to 50 wt %) using the common TiO₂ nanoparticle (P25) photocatalyst to rapidly print reactors with high photodegradation efficiency. The 3D-printed photocatalytic reactors, made by using the prepared slurry, successfully demonstrated complete 100% photodegradation of common organic synthetic dyes (methylene blue, safranin O, and brilliant green). Moreover, photocatalytic reactors with triply periodic minimal surface (TPMS) structures were successfully printed. The reactors with a Diamond structural (D-type) design showed a reaction rate constant of 0.0127 min^–1, which is 2.4 times higher than that of the Fischer-Koch S structural (F-type) reactors at 0.005 min^–1, underscoring the significant impact of reactor structural design on photodegradation efficiency. Finally, the study showcased the potential for direct manufacturing through the batch production of photocatalytic reactors via whole build-plate 3D printing. Achieving high-speed fabrication, the process was completed within 120 min on a 19.2 cm by 10.8 cm build platform, accommodating the batch printing of 10 photocatalytic reactors, each 1.3 cm in diameter and 2 cm in height.