Significantly enhanced photocatalytic activity of TiO2/TiC coatings under visible light

Abstract

Rutile TiO2 forms on TiC coatings (TiO2/TiC coatings) during carbon-embedding heat treatment (cHT) for TiC coatings. The photocatalytic activity of TiO2/TiC coatings has been significantly enhanced, especially under visible light. The influence of cHT temperature for TiC and Ti coatings on surface morphology, formed compounds, and photocatalytic activity has also been investigated. In general, rutile TiO2 forms on TiC coatings, whereas TiCxOy forms on Ti coatings. By raising the cHT temperature for TiC coatings, the surface morphology of TiO2/TiC coatings with a pore-like structure significantly changes from nano-size to micro-size, inevitably resulting in the reduction of the accessible surface area. However, the influence of cHT temperature on the Ti coatings is insignificant, demonstrating a smooth surface morphology. Notably, owing to the increased accessible surface area and formed heterojunction of TiO2/TiC, the photocatalytic activity of TiO2/TiC coatings has been significantly enhanced approximately 6 times especially under visible light, compared with that of TiCxOy/Ti coatings. Furthermore, when the cHT temperature has been raised, the photocatalytic activity of TiO2/TiC coatings initially increases and then decreases, achieving their most satisfaction at 1073 K, which is attributed to the narrowed band gap of TiO2 owing to the shifted O 1s spectra.