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.