Spectral Selective Solar Light Enhanced Photocatalysis: TiO2/TiAlN Bilayer Films

• Published in: Topics in catalysis Vol. 61; no. 15-17; pp. 1607 - 1614
• Main Authors: Österlund, Lars, Mattsson, Andreas, Brischetto, Martin, Byberg, Joel Johansson, Stefanov, Bozhidar I., Ji, Yu-Xia, Niklasson, Gunnar A.
• Format: Journal Article
• Language: English
• Published: New York Springer US 01.10.2018; Springer Nature B.V
• Subjects: Absorption; Acetaldehyde; Aluminum; Anatase; Bilayers; Catalysis; Catalytic activity; Characterization and Evaluation of Materials; Chemistry; Chemistry and Materials Science; Free surfaces; Heterojunctions; Industrial Chemistry/Chemical Engineering; Light; Magnetic properties; Magnetron sputtering; Multilayers; Optical properties; Original Paper; Oxidation; Pharmacy; Photocatalysis; Photovoltaic cells; Physical Chemistry; Raman spectroscopy; Reaction kinetics; Relative humidity; Solar energy absorbers; Substrates; Thin films; Titanium dioxide; Water film; Water gas; X-ray diffraction; TiO; Photocatalysis; TiAlN; Spectral selective films
• ISSN: 1022-5528; 1572-9028
• DOI: 10.1007/s11244-018-1011-5

We demonstrate that spectral selective photocatalytic multilayer films can be tailored such that they can harness the full solar spectrum for enhanced photocatalytic gas-phase oxidation of acetaldehyde. Thin films of anatase TiO 2 were deposited on a thin solar absorber TiAlN film to fabricate bilayer TiO 2 /TiAlN films by dc magnetron sputtering on aluminium substrates. The structural and optical properties of the films were characterized by X-ray diffraction and Raman spectroscopy. The reaction rate and quantum yield for acetaldehyde removal was measured and an almost tenfold enhancement of the quantum yield was observed for the TiO 2 /TiAlN films compared with the single TiO 2 film, on par with enhancements achieved with new heterojunction photocatalysts. The results were interpreted by a temperature-induced change of the reaction kinetics. Absorption of simulated solar light illumination resulted in a temperature increase of the TIAlN film that was estimated to be at most 126 K. We show that a concomitant temperature increase of the top layer TiO 2 by 100 K shifts the water gas-surface equilibrium from multilayer to submonolayer coverage. We propose that this is the main reason for the observed enhancement of the photocatalytic activity, whereby gas phase molecules may come in direct contact with free surface sites instead of having to diffuse through a thin water film. The implications of the results for judicious control of temperature and relative humidity for efficient gas-phase photocatalysis and exploitation of selective solar absorbing films are discussed.