Photocatalytic evaluation of ATO/TiO2 heterojunction films fabricated by a nanoparticle deposition system

Antimony-doped tin oxide (ATO), titanium dioxide (TiO2) and ATO/TiO2 mixtures (30:70, 50:50, 70:30 vol%) powders were deposited using a nanoparticle deposition system (NPDS). X-ray diffraction (XRD) data and field-emission scanning electron microscope (FE-SEM) images confirmed that the phases and morphologies of the deposited ATO and TiO2 were similar to those of their pristine structures. Photoelectrochemical (PEC) measurements showed the highest photocurrent of 1.5 mA for the 50:50 vol% ATO/TiO2 film, which compared with 1.2 mA for the other (30:70 and 70:30 vol% ATO/TiO2) hybrid samples, and 0.35 and 0.04 mA for pure TiO2 and ATO, respectively. Methylene blue (MB) dye was degraded in the presence of the 50:50 vol% ATO/TiO2 film, which had the best photocatalytic activity after 7 h of ultraviolet (UV) irradiation. The kinetic rate constant of this film was 0.15 h−1, which was double that of the TiO2 film (0.06 h−1). The photoluminescence intensity of the 50:50 vol% ATO/TiO2 film was low over a wide range of wavelengths, which indicated that its recombination rate was less than that of the ATO and TiO2 films. Finally, the recycle results demonstrated that the 50:50 vol% ATO/TiO2 film was stable to photodegradation for up to six cycles. These heterojunction films containing ATO and TiO2 thus had better photocatalytic properties than the pure TiO2 and ATO films due to the reduction in recombination. Our facile method of preparing heterojunction films by a dry deposition method provided films with good photocatalytic properties.