Annealing Temperature-Dependent Effects of Fe-Loading on the Visible Light-Driven Photocatalytic Activity of Rutile TiO2 Nanoparticles and Their Applicability for Air Purification

Commercial rutile TiO2 particles (200–300 nm) were modified by the temperature-regulated chemical vapor deposition (tr-CVD) of Fe-oxide and subsequent annealing at various temperatures (300~750 °C). As a result of the modification, the photocatalytic activity of the TiO2 regarding acetaldehyde removal under visible light was enhanced, and the enhancement effects were dependent on the annealing temperature. Specifically, the enhancement effects of the modification were most pronounced when Fe-TiO2 was annealed at 375 °C, whereas the effects were significantly reduced by annealing at higher temperatures (525 and 750 °C). The analytical results with various techniques, including two surface-sensitive methods (XPS (X-ray photoelectron spectroscopy) and TOF-SIMS (time of fight-secondary ion mass spectrometry)), revealed that the stronger metal support interaction between TiO2 and the loaded Fe-oxide at high temperature (>375 °C) resulted in the decreased charge separation efficiency and photocatalytic activity of the Fe-TiO2 under light irradiation. The production scale for the Fe-TiO2 photocatalysts can be easily increased (from 200 g to 8 kg per the unit process) by upsizing the reactor volume. The mass-produced samples exhibited similar activity to the samples produced at small scale, and they were photocatalytically active after being spread on a cement block (stainless steel plate) using a surface hardening agent (paint), showing the high applicability in real applications.