Generation of Oxygen Vacancy and OH Radicals: A Comparative Study of Bi₂WO₆ and Bi₂WO_6−x Nanoplates

Abstract

A comparative study of visible‐light‐responsive Bi2WO6 and oxygen‐deficient Bi2WO6−x nanoplates was conducted. The formation of oxygen vacancy resulted in the band gap narrowing of oxygen‐deficient Bi2WO6−x, through an elevation of both of the conduction and valence band positions. FTIR spectra revealed that much more surface hydroxyl groups have been detected after the etching process. The scavengers tests confirmed the generation of ⋅OH radicals during photochemical reaction for Bi2WO6−x, whereas no .OH radicals can be detected for pure Bi2WO6. The photocatalytic activities of optimized Bi2WO6−x on the decomposition of Rhodamine B (RhB) was three times as high as that of pure Bi2WO6. The improvement of photocatalytic activity on degradation of RhB and phenol can be ascribed to the synergistic effect of oxygen deficiency‐induced band shifts, together with the large quantities of surface hydroxyl groups providing active sites for the generation of OH radicals (.OH).

Metallic Bi Nanocrystal‐Modified Defective BiVO4 Photoanodes with Exposed (040) Facets for Photoelectrochemical Water Splitting

“…After the reduction process, the peak signal located at g≈2.000 is much stronger than that of the pure one, which can be attributed to the Zeeman Effect of single‐electron trapped by oxygen vacancies, indicating that suitable oxygen vacancies are produced . The similar results have been observed in Bi 2 WO 6 and TiO 2 ‐based semiconductors meanwhile the oxygen vacancies at the surface of samples play the part of electron capture center to promote the separation of electrons and holes . In addition, a slightly shift of g value to low value is observed in EPR spectrum for BiVO 4 ‐60, which is probably because the effect of Bi crystals on the localized electrons in oxygen vacancy …”

“…The intensity is decrease especially the diffraction peaks at 30.5° in BiVO 4 ‐60, meanwhile the characteristic peak of metallic Bi is strengthened, demonstrating that the metallic Bi may be formed mainly in the (040) crystal planes. Figure (b) shows the enlarge view of 24–34° range, it can be seen that the peak position of 2θ angle shifts to low‐angle along with a slightly broadening on the full width at half‐maximum, which may be caused by the residual stress coming from the oxygen defects and the reduced crystalline size . Analogical peak position shifts, resulted from the generation of oxygen defects, were observed in ZnO and CeO 2 as well …”

Oxygen‐Deficient BiOBr as a Highly Stable Photocatalyst for Efficient CO2 Reduction into Renewable Carbon‐Neutral Fuels

“…Based on the Tauc plot of modified Kubelka–Munk (KM) function (Figure E), the band gap energies of pristine and oxygen‐deficient BiOBr were estimated to be 2.85 and 2.70 eV, respectively. This phenomenon of oxygen‐deficiency‐induced band gap narrowing was also observed in the literature; it can be ascribed to the overlapping of oxygen‐deficiency‐induced defect states with the band edge of the semiconductor . To ascertain the presence of such defect states, photoluminescence (PL) spectroscopy was conducted.…”

Facile Fabrication of Z-Scheme Bi2WO6/WO3 Composites for Efficient Photodegradation of Bisphenol A with Peroxymonosulfate Activation

“…The WO 3 and Bi 2 WO 6 could generate the photogenerated holes and electrons under visible light irradiation, because their band gaps are about 2.64 and 2.81 eV, respectively [22,39]. In addition, the CB and VB edge position of Bi 2 WO 6 is −1.04 and 1.77 eV (vs NHE), and the CB and VB edge position of WO 3 is 0.77 and 3.41 eV (vs NHE), respectively [22,47,48]. Therefore, two kinds of transfer and separation of carrier transfer might be possible, according to the band arrangement principle.…”