Macro-meso-porous TiO2, ZnO and ZnO-TiO2-composite thick films. Properties and application to photocatalysis

We report on a new and versatile method for preparing homogenous, crack-free and macro-meso-porous thick films of TiO2, ZnO and ZnO-TiO2 composites using a single step coating procedure and fairly low annealing temperatures of a maximum of 400 degrees C. The method relies on an oxide nanopowder filler in an optimized precursor solution. The films are well adherent to the substrate, show homogeneously distributed open porosity, and are hydrophilic. The photocatalytic activity of these films was characterized using methyl orange as a model dye. We show that the TiO2 films have better photocatalytic activity than ZnO and ZnO-TiO2 composite films. The advantages of these composite films over particulate photocatalysts lie in their robustness and ease of application as no filtration is needed. Furthermore it is possible to apply them on suitable large area membranes.