Evaluation of the Photocatalytic Activity of TiO₂-Coatings Prepared by Different Thermal Spray Techniques

The metastable anatase structure of titanium dioxide (TiO₂) is photocatalytically active and thus able to purify air and water. This makes anatase TiO₂ a desirable material for instance in environmental technology. The present work provides a comparative study on the photocatalytic activity of TiO₂ coatings, prepared by different spray methods: conventional atmospheric plasma spraying, HVOF spraying, suspension spraying and cold spraying. The spray experiments were performed with anatase powder as feedstock and the spray parameters were optimized in order to obtain coatings with high photocatalytic performance. With respect to spray technique and spray conditions, different amounts of the photocatalytic active anatase phase could be retained. The photocatalytic activity of the coatings was evaluated by degradation of dichloroacetic acid. The results show that the photocatalytic activity is highly dependent on the amount of preserved anatase structure obtained under the different spray techniques.