1 Department of Mechanical Engineering, Technical University of Denmark2 Materials and Surface Engineering, Department of Mechanical Engineering, Technical University of Denmark3 Université Lille Nord de France4 National Institute of Materials Physics5 Danish Technological Institute6 Danish Fundamental Metrology7 Centre for oil and gas – DTU, Center, Technical University of Denmark8 Danish Technological Institute
The photocatalytic performance of magnetron-sputtered titanium dioxide (TiO2) coatings of different thickness in anatase crystalline structure deposited on aluminium 1050 alloy substrates was investigated using a combination of photo-electrochemistry, methylene blue decomposition, and microscopic and spectroscopic methods, such as high resolution scanning and transmission electron microscopy, atomic force microscopy and ellipsometry. The reaction resistance was measured by AC impedance, while photocurrent measurements were carried out using the zero resistance ammetry (ZRA) method. The results showed that the TiO2 grains grow in dipyramidal columns having a linear increase in surface area with increased coating thickness. The refractive index values indicate also an evolutionary growth. The refractive index values obtained for the thin coatings on aluminium substrate were well below the values reported for monocrystalline anatase. The photocatalytic performance increased with increased coating thickness, though more rapidly over a range of 100 - 500 nm thickness. The dielectric constant also increased linearly with coating thickness.