Abstract
Bismuth complex oxides, in particular, bismuth tungstate, have recently attracted attention as promising photocatalytic materials for water treatment processes. In the present work, photocatalytic bismuth tungstate films were prepared by pulsed direct current (DC) reactive magnetron sputtering of Bi and W targets in an Ar/O2 atmosphere onto spherically-shaped glass beads. The uniform coverage of the substrate was enabled by the use of oscillating bowl placed underneath the magnetrons. The atomic ratio of Bi/W was varied through the variation of the power applied to the magnetrons. The deposited coatings were analyzed by the scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD), X-ray photoelectron spectroscopy and atomic force microscopy. The photocatalytic properties of the films were studied via the methylene blue (MB) degradation process under artificial (fluorescent light) and natural (sunlight) irradiation, and compared to the photocatalytic performance of titanium dioxide coatings deposited onto identical substrates. The results showed that the photocatalytic performance of bismuth tungstate and bismuth oxide-coated beads was superior to that exhibited by TiO2-coated beads. Overall, reactive magnetron co-sputtering has been shown to be a promising technique for deposition of narrow band gap bismuth-based semiconducting oxides onto irregularly-shaped substrates for potential use in water treatment applications.
Highlights
Since the discovery of the photocatalytic phenomenon in 1969 [1], it has become the subject of extensive research work, and proposed as a promising and sustainable method for decontamination of air, water and soil [2,3]
Compositional data of the coatings are in good agreement with the earlier publications, as increasing the power applied to the bismuth target resulted in deposition of significantly bismuth-rich coatings, as compared to increasing the power applied to the tungsten target
The present work discusses a novel technique for the reactive magnetron sputter deposition of bismuth tungstate coatings onto spherically-shaped glass beads with subsequent use of the coated beads for water treatment under direct solar irradiance
Summary
Since the discovery of the photocatalytic phenomenon in 1969 [1], it has become the subject of extensive research work, and proposed as a promising and sustainable method for decontamination of air, water and soil [2,3]. A wide range of titanium dioxide-based materials have been successfully applied as photocatalysts for water treatment [7,8,9]. Titanium dioxide, as the most widely available and studied photocatalytic material, is typically characterized with a relatively high. The high band gap value results in titania photocatalysts being activated only with ultraviolet (UV) irradiation (less than 5% of the solar spectrum), for practical use, additional irradiation sources are required. The use of a photocatalyst in powdered form results in high surface area, but presents significant difficulties in recovering the powder from the treated water. Photocatalytic coatings deposited onto flat substrates do not require complicated recovery, they are characterized with low surface area values, compared to powdered photocatalysts and are, not suitable for high-throughput processes
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