A one-pot synthesis of nanostructured mesoporous TiO2 films on graphite felt substrates for fast catalysis

Abstract

In the present paper we report a one-pot synthesis of nanocrystalline, crack-free and mesoporous thin TiO₂ films on graphite felt (GrF) and GrF terminated with NiO nanoleaflets. The films are obtained using an immersion method in an ethanolic solution of titanium isopropoxide containing small amounts of NH₃ catalyser. A short heat treatment at 450 °C yields pure phase anatase directly on GrF or on the NiO nanoleaflets. The method allows processing of a variety of TiO₂/metal oxide heterostructures and can be implemented for other catalysts. The supported films were tested for their photocatalytic activity using a continuous-flow set-up of an aqueous amido black solution under a cold UV diode at 360 nm. The results are compared to those of a thick macro-mesoporous P25-TiO₂ film on Si. Full discoloration of the dye is obtained within 50 to 120 minutes for the films on the GrF substrates. The discoloration kinetics show a non-linear behaviour that is interpreted in terms of the rapid rarefication of the dye molecules. In contrast, the P25-TiO₂ film on Si shows the usual linear behaviour with a small rate constant. The highest discoloration rate is obtained with TiO₂ directly deposited on GrF. Based on the latest literature findings, it is postulated that the high defect density of the graphite structure could promote better charge separation and higher photocatalytic activity in comparison to the GrF/NiO/TiO₂ heterostructure.