A major challenge in heterogeneous photocatalysis is the need to increase charge separation efficiency of a photocatalyst, under illumination, without any applied electrical potential. Regularly patterned TiO2 films were formed on a SnO2-film coated soda lime glass substrate by using an organically modified sol-gel method: This bilayer-type photocatalyst exhibited a very high photocatalytic activity for gas-phase reactions. Efficient interfacial electron transfer from the TiO2 overlayer to the SnO2 underlayer was demonstrated by labeling and visualizing the reduction sites with Ag particles.