Enhancement of photocatalytic performance of P25-TiO₂ nanoparticles by 3D nanoporous anodic alumina at room temperature

The commercial Degussa P25-TiO₂ nanoparticles consisting of a mixed phase are a crucial environmental catalyst but encounter the robust coating problem onto the solid support for poor photocatalysis. Here, we have demonstrated a useful green method for greatly improving water-flushing robust coating as well as photocatalysis by over-etched three-dimensional (3D) nanoporous anodic aluminum oxide (AAO) that can be fabricated by large-scale electrochemical-anodic-oxidation processing at room temperature instead of high-temperature sintering for traditional ceramic foams up to 1200°C. Also, no additional high-temperature calcination of 400~900°C was needed. The 3D porous morphology exhibited more TiO₂ particles attachment on the rough surface and enlarged pore channels than the 2D. Moreover, the over-etched 3D AAO exhibited the most attachment of TiO₂ nanoparticles after water flushing due to high-porosity-and-contact-area 3D morphology which enhances the bonding between the substrate and nanoparticles for robust coating. XRD and SEM were used for analyzing the mixed phase and 2D-3D morphology of the P25-TiO₂ nanoparticles on AAO. After immersion in Methylene blue solution and 20 hour of UV illumination, TiO₂ nanoparticles on the over-etched 3D AAO with robust coating showed the best decomposition rate compared to other supports including Si wafer, typical 2D and 3D AAO.