Preparation of visible-light-responsive TiO2 coatings using molten KNO3 treatment and their photocatalytic activity

- Molten KNO3 treatment are used to prepare K-doped TiO2 photocatalyst coatings.
- The coatings show good antibacterial activity even in absence of light.
- The photocatalytic activity is increased with the amount increase of K-doping.
- The good antibacterial activity should come from the doping and release of K ions.

In this work, the process of mechanical coating followed by molten KNO3 treatment is given to prepare visible-light-responsive K+-doped TiO2. X-ray diffraction (XRD), scanning electron spectroscopy (SEM), Energy dispersive spectrometer (EDS) and X-ray photoelectron spectroscopy (XPS) were conducted to characterize these TiO2 coatings. The results showed that K+-doped anatase TiO2/Ti composite coatings formed after molten KNO3 treatment at elevated temperatures. Meanwhile, their photocatalytic degradation of methylene blue (MB) and the antibacterial activity against Escherichia coli (E. coli) was also studied. The visible-light-responsive photocatalytic activity of the coatings in MB degradation increased with increase of K+ ions when holding temperature was raised from 673 to 773 K. An excellent antibacterial activity of the K+-doped TiO2/Ti coatings against E. coli was also obtained even in absence of light. The antibacterial activity in dark should attribute to the release of K+ ions from the coatings. The photocatalytic activity under visible-light irradiation should result from the absorption spectrum extension due to the doping of K+ ions into the lattice of TiO2.

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