Enhanced photocatalytic activities of Bi₂WO₆ by introducing Zn to replace Bi lattice sites: a first-principles study

Abstract

The geometry structure, electronic structure, and band edge positions of Zn-doped Bi 2 WO 6 have been studied using first-principles method. Bi 1.75 Zn 0.25 WO 6 has a high quantum efficiency (QE) caused by the large mobility along different orientations and the efficient photogenerated-electron trap. It exhibits the enhanced visible-light absorption capability (α) owing to the large increase of the density of electrons in the valence band maximum (VBM) and decrease in the band gap. The interactions are both strengthened between layers and among atoms within (Bi 2 O 2 ) n layers. These strengthened interactions induce enhanced stereochemically active Bi lone pair effect, which is identified as the cause of its unique electronic structure. Furthermore, the valence band (VB) and conduction band (CB) edges of Zn-doped Bi 2 WO 6 are slightly shifted upwards. This indicates that the dominant active species during photocatalytic reaction for Bi 1.75 Zn 0.25 WO 6 are not only hole and electron but also ·O 2 − ion and ·OH radical. PACS: 71.15.Mb

Low temperature synthesis and characterization of substitutional Na-modified K2Ti6O13 nanobelts with improved photocatalytic activity under UV irradiation

“…[49][50][51] From this angle, a possible mechanism for improved photocatalytic activity of NKTO nanobelts was tentatively proposed and illustrated in Fig. Except the low temperature synthesis resulting in high S BET , the substitutional Na-modifying changes the phase composition and band structure, which is deemed to play a vital role in improving the photocatalytic activity.…”

Structural and spectroscopic comparison between polycrystalline, nanocrystalline and quantum dot visible light photo-catalyst Bi2WO6

“…The UV-VIS spectra of PC, NC and QD samples of Bi2WO6 along with their respective Tauc [38] and DASF [39] [18]). The bandgap calculated from DFT differs from the experimental values in two ways.…”

“…The 6s of bismuth (d 10 ) is susceptible to hybridize O-2p, constituting a shifted/preferable hybridized valence band, which then favors the mobility of photon-induced holes in the valence band and can enhance the photocatalytic performance of the Bi-based oxides. Moreover, the stereochemical activity of 6s 2 lone electron pair was demonstrated playing important roles for the catalytic enhancement [18]. Studying over a number of Bi-W-oxides it has been found that Bi2WO6the simplest member of the Aurivillius [19] family, exhibits photocatalytic activity under visible light irradiation [20][21] [22].…”

First-principles study on the electronic and optical properties of Bi2WO6

“…4 Bismuth tungsten oxide Bi 2 WO 6 belongs to this class of Wbased photocatalytic materials, which has already been explored experimentally 5 and theoretically. 6 It has lower photocatalytic activity as compared to TiO 2 ; however, it's lower band gap makes it photo-active even at visible frequencies, albeit at the higher frequency end of the visible spectrum. However, it's band gap can be tuned, 6 apart from it being photostable and environment-friendly.…”

“…5 However, there are still unanswered questions as the theoretical results do not fully explain observations from absorption and emission spectroscopy of this material system. A multitude of theoretical calculations have also been reported on Bi 2 WO 6 , most of them are studies carried out to enhance the photocatalytic activity via doping, 6,[8][9][10] or making heterostructure. However, almost all the previous study aims toward the relative study of Bi 2 WO 6 with respect to the doped or modied system, and hence the comparison with the measured data was oen overlooked.…”