Doping of titanium dioxide with p-block elements is typically described as an efficient pathway for the enhancement of photocatalytic activity. However, the properties of the doped titania films depend greatly on the production method, source of doping, type of substrate, etc. The present work describes the use of pulsed direct current (pDC) magnetron sputtering for the deposition of carbon-doped titania coatings, using CO2 as the source of carbon; ratios of O2/CO2 were varied through variations of CO2 flow rates and oxygen flow control setpoints. Additionally, undoped Titanium dioxide (TiO2) coatings were prepared under identical deposition conditions for comparison purposes. Coatings were post-deposition annealed at 873 K and analysed with scanning electron microscopy (SEM), X-ray diffreaction (XRD), atomic force microscopy (AFM), and X-ray photoelectron spectroscopy (XPS). The photocatalytic properties of the thin films were evaluated under ultraviolet (UV) and visible light irradiation using methylene blue and stearic acid decomposition tests. Photoinduced hydrophilicity was assessed through measurements of the water contact angle under UV and visible light irradiation. It was found that, though C-doping resulted in improved dye degradation compared to undoped TiO2, the UV-induced photoactivity of Carbon-doped (C-doped) photocatalysts was lower for both model pollutants used.

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Doping of TiO2 with carbon is known to be an efficient method of enhancing visible light photocatalytic activity. The present work describes the deposition of carbon-doped titania coatings deposited by reactive magnetron co-sputtering of Ti and C targets. Undoped titania coatings were produced under similar deposition conditions for comparison purposes. Following deposition, all coatings were annealed in air at 873K for 30 min to develop the required crystalline structure; and then analysed with EDS, XRD, AFM, XPS and UV-visible spectrophotometry. A number of tests, including methylene blue and stearic acid decomposition tests, and photo-induced hydrophilicity measurements, were employed for the assessment of the photocatalytic properties of the C-doped and un-doped titanium dioxide coatings under UV and visible light irradiation. It was found that carbon-doped titania coatings significantly outperformed undoped titania when using both visible and UV irradiation. Similar trends were observed for other properties. While excessive carbon doping has been shown to have a negative effect on the photocatalytic properties of the titanium dioxide, overall, carbon doping 2 via reactive co-sputtering has been confirmed as an efficient method of photocatalytic property enhancement. This is due to a narrowing of the bandgap and to extended lifetimes of the photogenerated charge carriers.

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