Photocatalytic visible-light active bismuth tungstate coatings deposited by reactive magnetron sputtering

Abstract

Photocatalytic bismuth tungstate thin films with visible-light activity were deposited via reactive pulsed DC magnetron sputtering onto soda-lime glass substrates. Varying the power delivered to the bismuth and tungsten targets allowed control over the Bi/W ratio in the coatings, and therefore the structural and optical properties of the coatings. Asdeposited coatings were characterised with amorphous microstructures and were annealed at 673K to develop crystallinity. The visible light photocatalytic activity of the coatings, which was analysed using the methylene blue degradation test, was found to be superior to that of a commercial titania-based photocatalytic product. \

A Novel Technique for the Deposition of Bismuth Tungstate onto Titania Nanoparticulates for Enhancing the Visible Light Photocatalytic Activity

“…As can be seen from the data presented in Table 1, variation of the power applied to the bismuth and tungsten targets resulted in variations in coating composition, in a similar manner to the deposition of bismuth complex oxides onto flat substrates reported earlier [26,27]. BET surface area measurements of PC500 titania were in good agreement with the manufacturer's information of 350 m 2 /g.…”

“…Of the samples studied, the highest level of activity was recorded for the coating BWO2, nevertheless the band gap value of this sample was not the lowest of those tested here. The lower photocatalytic activity of sample BWO3, despite its lower band gap, can possibly be explained by the presence of amorphous tungsten in this tungsten-rich sample, which could inhibit the photoactivity [26]. …”

“…Of the samples studied, the highest level of activity was recorded for the coating BWO2, nevertheless the band gap value of this sample was not the lowest of those tested here. The lower photocatalytic activity of sample BWO3, despite its lower band gap, can possibly be explained by the presence of amorphous tungsten in this tungsten-rich sample, which could inhibit the photoactivity [26]. It should be noted that, at this stage of the work, it is not known whether the observed increase of visible light photocatalytic activity is solely due to the red shift of the band gap and more efficient charge carrier separation of the composite material, rather than the intrinsic photocatalytic properties of bismuth tungstate that are often reported.…”

Reactive Magnetron Sputter Deposition of Bismuth Tungstate Coatings for Water Treatment Applications under Natural Sunlight

“…Bismuth complex oxides have recently attracted researchers' attention as promising candidates for visible light photocatalysis due to the fact that they are typically characterized with low band gap values, as the result of the hybridization between the Bi 2p and O 2s states [11]. Bismuth tungstate, Bi 2 WO 6 , is one of the most widely studied and reportedly efficient photocatalytic materials [12][13][14][15][16]. However, there are very few reports to date describing the use of bismuth tungstate for water purification [17,18].…”

“…In the present work, this process was used for the deposition of photocatalytic bismuth tungstate coatings onto spherically-shaped glass beads, as opposed to the flat substrates reported in earlier work of the authors, to provide considerably higher surface area. Bismuth tungstate coatings are often described as efficient visible light-activated photocatalytic materials [15], however, they are usually produced by chemical methods, e.g., hydrothermal methods [13,14] or electrospinning [22]. Use of photocatalyst-coated particulates is frequently reported for water treatment applications, however, chemical methods are typically used for the coating's deposition [23][24][25].…”