Abstract
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.
Highlights
Titanium dioxide (TiO2) photocatalysts have attracted a lot of attention since the discovery of their properties through photocatalytic water splitting reactions in 1972 [1]
All undoped TiO2 thin films showed low rates of Methylene Blue (MB) decay under visible light irradiation with kinetic constants below 1 × 10−5 s−1, and no significant variation of the kinetic constant values was seen for undoped titania coatings produced at different Optical Emission Monitoring (OEM) setpoints
The ability to photodegrade MB under visible light irradiation increased with increasing OEM setpoint along with increasing CO2 flow rate
Summary
Titanium dioxide (TiO2) photocatalysts have attracted a lot of attention since the discovery of their properties through photocatalytic water splitting reactions in 1972 [1]. Despite a variety of applications of photocatalytic materials being proposed (e.g., building materials, antimicrobial surfaces, self-cleaning surfaces, waste water treatment, etc.), the practical application of photocatalytic materials still remains quite limited [2,3]. This is due to several drawbacks of titania, such as low photonic efficiency and the relatively high band gap value. As UV constitutes just under 4% of the solar spectrum, for many practical applications it is necessary to shift the photocatalytic activity of titanium dioxide into the visible range
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