Abstract
A novel powder handling technique was used to allow the deposition of bismuth tungstate coatings onto commercial titanium dioxide photocatalytic nanoparticles. The coatings were deposited by reactive pulsed DC magnetron sputtering in an argon/oxygen atmosphere. The use of an oscillating bowl with rotary particle propagation, positioned beneath two closed-field planar magnetrons, provided uniform coverage of the titania particle surfaces. The bismuth/tungsten atomic ratio of the coatings was controlled by varying the power applied to each target. The resulting materials were characterized by X-ray diffraction, energy-dispersive X-ray spectroscopy (EDX), Brunauer–Emmett–Teller (BET) surface area measurements, transmission electron microscopy (TEM), and UV-visible diffuse reflectance spectroscopy. Photocatalytic properties under visible light irradiation were assessed using an acetone degradation test. It was found that deposition of bismuth tungstate onto titania nanoparticles resulted in significant increases in visible light photocatalytic activity, compared to uncoated titania. Of the coatings studied, the highest photocatalytic activity was measured for the sample with a Bi/W atomic ratio of 2/1.
Highlights
In the past few decades, photocatalysis is often reported as a process of choice for the degradation of organic pollutants and surface disinfection
The present study describes the deposition of bismuth tungstate onto titania powders by pulsed DC
The microstructures of plain and coated titania further studied by transmission electron microscopy (TEM)
Summary
In the past few decades, photocatalysis is often reported as a process of choice for the degradation of organic pollutants and surface disinfection. Of the photocatalytic materials known, titanium dioxide, or titania, in anatase form is typically a photocatalyst of choice for various environmental remediation processes due to its low cost, chemical stability, and low toxicity. Titanium dioxide in the form of nanoparticles is much more efficient as a photocatalyst, compared to bulk material, as it provides much higher surface area and higher area of contact with the pollutant. Degussa P25 is reportedly the most widely used photocatalytic material to date. The relatively high band gap value of TiO2 (3.2 eV for the anatase phase) means that only the UV part of the spectrum (around 4% of sunlight) can be used for its activation. Various modifications of titanium dioxide have been proposed to date, with doping with transition metals [1,2,3] and non-metallic [3,4]
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