Generation of H₂O₂ and OH Radicals on Bi₂WO₆ for Phenol Degradation under Visible Light

Abstract

In thermodynamics, the one-electron reduction of O 2 by the conduction band electrons of Bi 2 WO 6 or WO 3 is not allowed. However, many studies have reported that Bi 2 WO 6 is photocatalytically active for organic degradation in aerated aqueous suspension. In this work, the photocatalytic activities of Bi 2 WO 6 and WO 3 under visible light have been compared by using phenol degradation as a model reaction. In aerated aqueous solution, Bi 2 WO 6 and WO 3 were indeed active and inactive, respectively, as reported. However, by using Pt as a catalyst for O 2 reduction, or by using H 2 O 2 as an electron scavenger, Bi 2 WO 6 became much less active than WO 3 . Similar results were also obtained in the production of H 2 O 2 under visible light, and in the generation of • OH radicals under UV light, measured by a spin-trapping electron paramagnetic resonance (EPR) spectroscopy. Moreover, in the presence of catalase to completely remove H 2 O 2 , the EPR signal due to • OH radical was reduced, but not disappeared. These observations indicate that the irradiated Bi 2 WO 6 is not only active for water oxidation to • OH but also active for the two-electron reduction of O 2 to H 2 O 2 , the latter of which hardly occurs with the irradiated WO 3 .

Fabrication of platinum-deposited carbon nitride nanotubes by a one-step solvothermal treatment strategy and their efficient visible-light photocatalytic activity

“…In recent decades, the development of semiconductor photocatalytic materials and photocatalytic technique brought new opportunities and challenges for solving the energy and environmental problems [4][5][6][7]. Various photocatalytic systems have been widely studied such as hydrogen evolution, organic pollutant degradation, and carbon dioxide reduction [8][9][10]. Since its discovery in 2008, the application of the visible-light photocatalytic activity of graphite carbon nitride (g-C 3 N 4 ) as an effective metal-free semiconductor photocatalyst was extensively developed [11][12][13][14][15].…”

Promotion of multi-electron transfer for enhanced photocatalysis: A review focused on oxygen reduction reaction

“…Surprisingly, Bi 2 WO 6 has a photocatalytic activity superior to that of WO 3 . [55][56][57][58][59] To find out the origin of such activity difference, Sheng et al [60] examined the produced amount of H 2 O 2 determined by a colorimetric DPD method in the presence of phenol solution and catalyst under visible light. The results were shown in Figure 5.…”

Heterostructured Bi2O3/Bi2MoO6 nanocomposites: simple construction and enhanced visible-light photocatalytic performance

“…8,9 Cu 2 O is also unsatised due to its wide size distribution and the high recombination rate of electron-hole pairs. 10 As typical visible-light photocatalysts, Bibased semiconductor materials, such as Bi 2 WO 6 , BiVO 4 , Bi 2 MoO 6 , and BiOX (X ¼ Br, Cl, I), [11][12][13][14] have been paid much attention in recent years because of their layer structures and high catalytic properties. Among them, Bi 2 MoO 6 is an n-type semiconductor with the layered Aurivillius structure, which consists of [Bi 2 O 2 ] 2+ layers sandwiched between MoO 4 2À slabs.…”