Improvement of photocatalytic activity of TiO₂ coating by the modified sol-gel method

Photocatalytic TiO₂ was coated on a stainless steel (SUS316L) substrate via a sol-gel method at a calcination temperature of 600°C. The sol-gel precursor (titanium isopropoxide) solution was modified by adding crystalline (anatase or rutile) TiO₂ particles to control the crystal phase of the TiO₂ coated on the substrate. The effect of the number of TiO₂ coatings was also evaluated. The TiO₂ coating was characterized by scanning electron microscopy, X-ray diffraction, and X-ray photoelectron spectroscopy. The photocatalytic activity was evaluated from the degradation of methylene blue solution on the TiO₂ coating after UV irradiation. The amount of bacteria adhered on the substrate was also evaluated. The TiO₂ coating comprising a binary phase (anatase/rutile weight ratio = 4.9/5.1) showed the highest photocatalytic activity, which improved after increasing the number of coatings. The amount of bacteria adhered on each TiO₂-coated substrate was not significantly different from that on the uncoated substrate.