Fabrication and characterization of meso-macroporous anatase TiO2 films

A porous TiO2 film possessing both meso-sized (2-50 nm) pores and macro-sized (100-300 nm) pores has been fabricated for the first time by coating an SnO2 substrate with a paste consisting of secondary TiO2 submicroparticles, poylethylene glycol, hydroxypropyl cellulose and water, followed by calcination. The macropores are formed most probably by phase separation between the TiO2 particles and the polymers in the course of drying of the coated paste. The meso-macroporous TiO2 film thus prepared has a thickness of ca. 10 mu m by four-fold coating, and is characterized by a large surface area arising from the mesopores in the secondary TiO2 particles, and by the presence of wide channels within the film. The film fabricated by calcination at 550 degrees C for 30 min was composed of pure anatase with high crystallinity. These features are favorable to construct an electrode for dye-sensitized photoelectrochemical cells.