Characterization and Visible Light Photocatalytic Activity of Cerium- and Iron-Doped Titanium Dioxide Sol−Gel Materials

Abstract

Cerium- and iron-based titanium dioxide catalysts are made at varying concentrations and cured at different temperatures to develop a new class of photocatalysts that displays catalytic activity for volatile organic compound destruction when irradiated with visible light. These catalysts are characterized using X-ray diffractometry, Raman spectroscopy, UV−vis diffuse reflectance spectroscopy and BET surface area analyses. The potential of these catalysts to destroy indoor air volatile organics is evaluated using a tubular reactor flow channel with visible light irradiated interior surfaces through which air contaminated with toluene, decane, ethanol, acetaldehyde, or linalool is reacted. It was found that both cerium- and iron-doped titania have lower band-gap energy than pure titania and can be activated with visible light. The anatase and rutile phase transitions of these doped titania is however similar to pure titania and is unaffected by dopants. The crystalinity is however altered and crystal sizes in the range of six to nine nanometers were obtained with the sol−gel type synthesis of the titania catalyst. Although both cerium- and iron-based titania show destruction of these volatile organics in visible light as compared to pure titania, cerium-based titania has better performance than iron-based titania. A photocatalytic oxidation reaction pathway for linalool is proposed on the basis of previous studies and compounds are identified in the exit stream of the reactor. Further, reaction rate constants for toluene, linalool, ethanol, and acetaldheyhde have been determined using a two-dimensional diffusion model (Sidheswaran and Tavlarides, 2008), and are compared with values from literature. It has been found that cerium-doped titania developed in this study performs comparably to the commercially available titania even when irradiated with visible light.