Evaluation of Bi–W‐oxides for visible light photocatalysis

Abstract

Photocatalytic solar water splitting has the potential to become a low‐carbon source of hydrogen fuel over the coming decades if the issue of low visible light absorption can be addressed without sacrificing chemical stability. We report on an investigation into the potential of the Bi–W‐oxides, Bi2WO6 and Bi6WO12, as visible light photocatalysts. X‐ray diffraction and Raman spectroscopy have been used to assess the structure of the oxides, whilst UV–vis diffuse reflectance spectroscopy analysed with the Kubelka–Munk function has been used to identify their optical band gaps. It has been revealed that Bi6WO12 shows significantly higher optical absorption in the region above 440 nm than either Bi2O3 or WO3, raising the possibility of enhanced photocatalytic activity under solar illumination. Bi2WO6 has a marginally lower band gap at 2.59 eV than Bi2O3 or WO3 but the results reported herein raise doubts concerning its chemical stability under aqueous, illuminated conditions for protracted periods of time. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

(Photo)electrochemical Methods for the Determination of the Band Edge Positions of TiO2‐Based Nanomaterials

“…Therefore, as will be discussed below in more detail, the determination of the conduction band edge often translates into the measurement of the position of the quasi-Fermi level of electrons. Once this is known, the position of the valence band edge can be simply calculated by adding the value of bandgap energy, that is, typically determined by optical [128,[141][142][143][144][145][146][147][148][149][150][151] or photoelectrochemical methods [152][153][154][155][156].…”

Nanoporous‐Walled Tungsten Oxide Nanotubes as Highly Active Visible‐Light‐Driven Photocatalysts

“…The quantum efficiency of nitrogen-doped TiO 2 under visible light is therefore much lower than that under UV illumination. [8] In contrast, tungsten trioxide (WO 3 ), which possess a small bandgap of between 2.4 and 2.8 eV, has many advantages for visible-light-driven photocatalysis, including a deeper valence band (+ 3.1 eV), strong adsorption within the solar spectrum, stable physicochemical properties, and resilience to photocorrosion effects. [10] However, pure WO 3 has a lower light energy conversion efficiency than the more widely used TiO 2 as the reduction potential of the electrons in WO 3 is low due to its low conduction band level.…”

BiOCl/ultrathin polyaniline core/shell nanosheets with a sensitization mechanism for efficient visible-light-driven photocatalysis

“…Thus, it can be deduced that the presence of PANI significantly affects the visible-light absorption of BiOCl/PANI. The band-gap energies of PB-1 and PB, estimated from a plot of (αhν) 1/2 versus the photon energy (hν) [33], are approximately 3.25 and 2.8 eV, respectively (Supplementary information (SI) Fig. S1).…”