Improved Texturing and Photocatalytic Efficiency in TiO2 Films Grown Using Aerosol‐Assisted CVD and Atmospheric Pressure CVD

Abstract

Four different TiO2 films are formed on glass at 500°C by aerosol‐assisted (AA)CVD, atmospheric pressure (AP)CVD, AACVD followed by APCVD, and APCVD followed by AACVD. The APCVD films are formed from reaction of TiCl4(g) whilst the AACVD films are made by decomposing Ti[OCH(CH3)2]4 contained in an aerosol. The film composition is studied using X‐ray photoelectron spectroscopy (XPS) to ascertain the purity of the films, and no Cl traces can be found on any of the surfaces. The use of different combinations of CVD gives rise to significant changes in microstructure and preferred orientations. X‐ray diffraction (XRD) patterns and Raman spectroscopy (RS) confirm that TiO2 in the anatase form is the dominant phase on all samples. All films show superhydrophilicity after 50 min of black‐light irradiation. The photocatalytic efficiencies of the films are assessed qualitatively by an ink test based on Resazurin, and quantitatively studied by measuring formaldehyde formation from tris(hydroxymethyl)aminomethane (Tris). Both methods show that the AACVD film and the film seeded by APCVD are the most photocatalytically efficient ones, both having an apparent quantum yield (AQY) of around 4.2%, while the APCVD film and the film seeded by AACVD have an AQY of 0.8% and 1.5%, respectively. The changes in photocatalytic activity are explained in part by changes in film microstructure and the accessible surface area.