Formation of hydroperoxo (–OOH) species on the surface of self-doped Bi_2.15WO₆: reactivity towards As(iii) oxidation

Abstract

The formation of –OOH groups and their high reactivity for As(iii) oxidation under visible light and alkaline conditions are demonstrated.

Contribution of H-Abstraction to Photocatalytic Oxidation of As(III) by Bi2.15WO6

“…By contrast, no H 2 O 2 could be detected in the reaction system of Bi 2.15 WO 6 and 20 mg L −1 As(III) under the low light intensity (0.18 mW cm −2 ) at pH 11.6. 7 When 20 mg L −1 As(III) was replaced with 20 mg L −1 As(V) at pH 6.0, no H 2 O 2 could be detected (Figure 2), indicating some correlation between As(III) oxidation and H 2 O 2 production. In the pH range of 3.0−9.0, pH 6.0 seems to be the optimal pH to produce more H 2 O 2 , and 130.5 μM H 2 O 2 was produced after 80 min (Figure 2).…”

“…Our previous study also showed that the oxidation of As(III) was more favorable at the higher pH in the Bi 2.15 WO 6 system under a low light intensity (0.18 mW cm −2 ), and an apparent oxidation of As(III) could only be detected when pH > 7.0. 7 Apart from the oxidation of As(III), H 2 O 2 was also produced during the photocatalytic oxidation of As(III) by Bi 2.15 WO 6 , whereas no H 2 O 2 could be detected in the oxidation systems in the absence of visible light (Figure 2), indicating the importance of the photocatalytic reduction of dissolved oxygen to H 2 O 2 during the photocatalytic oxidation of As(III). Figure 2 also shows that no H 2 O 2 is detected in the absence of As(III) at pH 6.0, whereas 130.5 μM H 2 O 2 was produced after 80 min at pH 6.0 after 20 mg L −1 As(III) was added into the reaction system, indicating that the hydrogen resource is from the hydroxyl group of As(III) instead of H 2 O.…”

“…Kinetic experiments were also conducted in the N 2 atmosphere to determine the contribution of dissolved oxygen to As(III) oxidation. 7 2.4. Chemical Analyses and Characterizations.…”

“…31,32 The electrochemical analyses including Mott−Schottky analysis, electrochemical impedance spectroscopy (EIS), transient photocurrent, Tafel plots, and cyclic voltammetry (CV) were carried out using an electrochemical workstation (CHI 660E, Chenhua Instruments Ins., China) in a standard three-electrode cell containing 0.1 M Na 2 SO 4 aqueous solution with a platinum plate as the counter electrode, a conducting glass [fluorine-doped tin oxide (FTO)] coated with Bi 2.15 WO 6 as the working electrode, and a saturated Ag/AgCl electrode as the reference electrode. 7,26 In preparing the working electrode, a suspension containing 4.0 mg of Bi 2.15 WO 6 and 10 mL of polyvinylidene fluoride/N-methylpyrrolidone (PVDF/NMP) (0.1 g of PVDF dissolved in 10 mL of NMP) was coated on a 1 × 1 cm FTO glass substrate, which was then dried in an oven at 60 °C. During the electrochemical analyses, the electrode cell was irradiated by the same light source used for kinetic experiments, and all electrochemical analyses were conducted at 25.0 ± 1.0 °C.…”

“…Our recent study also suggested that the  Bi−OOH peroxo species on Bi 2.15 WO 6 formed via the reduction of dissolved oxygen at the CB played an important role in As(III) oxidation at pH 11.6. 7 However, the correlations between the formation of the Bi−OOH peroxo species and the oxidation of As(III) are still not clear. In addition, the interactions between As(III) and photocatalysts have not been paid more attention to investigate the adsorption of As(III) on its subsequent oxidation.…”