Synthesis of Visible-Light Active Monoclinic WO₃ by Thermal Oxidation of Tungsten Powder for Photoreduction of Cr(VI)

Abstract:

In this paper, visible-light-active monoclinic WO₃ powders were synthesized by thermal oxidation of W powders at 200 – 1000 °C in air atmosphere. Morphology and crystal structure of annealed W powders were characterized by Scanning Electron Microscopy (SEM) and X-ray Diffraction (XRD), respectively. Based on SEM and XRD results, a spherical orthorhombic-W₃O₈ obtained at 200 °C was transformed into a dendritic monoclinic WO₂ + tetragonal WO₃ + monoclinic WO₃ structures at 400 °C accompanied by a color transition from grey into green. At 600 °C, yellow monoclinic WO₃ + monoclinic WO_2.96 powder was produced that ascribed to oxygen vacancies. Photocatalytic activity of annealed W powders demonstrated 70.7% Cr (VI) removal after 150 min on sample annealed at 1000 °C. This ascribed to high photoactivity of monoclinic WO₃. Nevertheless, the dendritic monoclinic WO₂ + tetragonal WO₃ + monoclinic WO₃ obtained at 400 °C exhibited the lowest Cr (VI) photoreduction i.e. 45.2% implies less photoactive monoclinic WO₂ and sluggish electron transport at oxide-oxide interfaces.

• Periodical: Materials Science Forum (Volume 1010)
• Pages: 405-410
• DOI: https://doi.org/10.4028/www.scientific.net/MSF.1010.405
• Online since: September 2020
• Authors: Nurulhuda Bashirom*, Qiao Ling Lee
• Keywords: Hexavalent Chromium, Photoreduction, Thermal Oxidation, Tungsten, Tungsten Trioxide

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