Correlation of Optical Properties, Electronic Structure, and Photocatalytic Activity in Nanostructured Tungsten Oxide

• Published in: Advanced materials interfaces Vol. 4; no. 18
• Main Authors: Ling, Min, Blackman, Christopher S., Palgrave, Robert G., Sotelo‐Vazquez, Carlos, Kafizas, Andreas, Parkin, Ivan P.
• Format: Journal Article
• Language: English
• Published: Weinheim John Wiley & Sons, Inc 22.09.2017
• Subjects: AACVD; Carrier recombination; Catalytic activity; Chemical vapor deposition; defect engineering; Defects; dislocation loop; Electronic structure; Energy gap; Nanorods; NIR absorption; Optical properties; Oxidation; Photocatalysis; Photonic band gaps; Photons; Stearic acid; tungsten oxide; Tungsten oxides; Widening
• ISSN: 2196-7350; 2196-7350
• DOI: 10.1002/admi.201700064

Tungsten trioxide nanorod arrays are deposited using aerosol assisted chemical vapor deposition. The electronic structure, defect chemistry, optical bandgap, and photocatalytic activity are found to vary progressively with nanorod length. Nanorods less than 1 µm in length show a widening of the optical bandgap (up to 3.1 eV), more disorder states within the bandgap, an absence of reduced tungsten cation states, and increased photocatalytic activity for destruction of a test organic pollutant (stearic acid) compared to nanorods of 2 µm length or greater which possessed bandgaps close to the bulk value for tungsten oxide (2.6–2.8 eV), the presence of reduced tungsten states (W4+), and lower photocatalytic activity. The results indicate that for maximum photocatalytic performance in organic pollutant degradation, tungsten oxide should be engineered such that the bandgap is widened relative to bulk WO3 to a value above 3 eV; although less photons are expected be absorbed, increases in the overpotential for oxidation reactions appear to more than offset this loss. It is also desirable to ensure the material remains defect free, or the defect concentration minimized, to minimize carrier recombination. Electronic structure, defect chemistry, optical bandgap, and photocatalytic activity are found to vary progressively with nanorod length and width of tungsten trioxide nanorod arrays deposited using aerosol assisted chemical vapor deposition.