The aim of this study is to further the understanding between photocatalytic activity (PCA) and micro structures of DC-magnetron sputtered thin TiO2 films. The different microstructures were obtained by changing the sputtering conditions (0.25 and 0.4A) and the post annealing treatment (500°C-600°C;2-4h). AzureB was chosen as model compound and the PCA was evaluated as an apparent 1st order reaction rate on a surface area basis. The film morphology and surface area were determined by SEM, XPS and contact angle measurements. The PCA of the films were compared with solgel films and Degussa P25.

DC-MS thin films were 100-150nm thick with a specific surface area of 5.2-5.8cm2cm-2. No/little PCA activity was observed for the films without oxygen, but with oxygen, the thin films degraded about 20% of the AzureB solution(5ppm) in 300 minutes. The solgel films showed the highest PCA/surface area , but a low reusability. Degussa P25 showed a similar PCA /surface area (5.8*10-5cm-2min-1) as the MS2500°C@4h and MS2600°C@4h films (5.2 and 4.5*10-5cm-2min-1). This was followed by, MS2500°C@2h and MS1500°C@4h (3.0 and 1.5*10E-5cm-2min-1). This indicates that the duration of heat treatment affects the PCA more than the temperature at this temperature range. All DC-MS films became more hydrophobic after the reaction, and the lower the initial wettability, the higher the PCA. SEM and XPS showed that the films were degraded in the form of swelling and a reduction in surface area after 3-6 runs. However, this was only translated in a small decrease in photo catalytic activity.