Photoelectrochemical and photocatalytic activity of nanocrystalline TiO2 thin films deposited by chemical bath deposition method

The thin films of nanocrystalline TiO2 were synthesized using titanium isopropoxide as a source of Ti on fluorine-doped tin oxide (FTO) and commercial glass substrates by chemical bath deposition method. The resultant films were annealed at different temperatures (300, 400 and 500 °C) for 3 h. The annealed nanocrystalline thin films were thoroughly characterized by XRD, SEM, UV–Vis. DRS, PL, FT-IR, Raman and TEM. The XRD study shows the average crystallite size of TiO2 is 15 nm having anatase phase, while as temperature increases crystallite size increases. SEM and TEM results show elongated spherical shape of TiO2 nanocrystals. Optical absorption spectra show the band gap energy decreases from 3.2 to 3.1 eV as annealing temperature increases. From the PL spectra, an emission peak observed at 600 nm is due to the indirect band gap and defects present in the material. The FT-IR spectrum of TiO2 thin film annealed at 400 °C shows the band at 532 cm−1 due to O–Ti–O stretching vibrations confirms the formation of anatase TiO2. The Raman spectrum shows an intense peak at 149 cm−1 and four weaker peaks are characteristics of anatase phase of TiO2. The photodegradation efficiency of methyl orange (MO) was observed to be 92% by using TiO2 thin film within 90 min under UV–Vis. light. It shows enhanced photoconversion efficiency of 1.02% under UV light.