A novel photocatalytic device consisting of a sol-gel (SG) TiO2 film coated on an internal lightguide (quartz rod) was prepared. The SG-TiO2 (anatase) film was revealed to have a dual particle structure with a large surface area of 117.1 m(2) g(-1). The significantly higher efficiency of the device compared to the TiO2 particulate system was obtained in both the photodeposition of Pt and the decomposition of HCOOH. The kinetic analysis suggests that the photodeposition proceeds via the Langmuir-Hinshelwood mechanism. Ultrafine particles of Pt (similar to 2 nm) dispersed on TiO2 acted as a good promoter of the photodecomposition of HCOOH. The rate of the reaction continued to increase with the increasing amount of Pt loaded up to 16.1 weight percent (w/o), whereas it had a maximum al 2.2 w/o in the particle system. This result was rationalized in terms of the feature that the device is not influenced by light shielding due to the surface deposits of Pt, which was observed in the particulate system.