Activation Of O-O Bond By Self-doped Bismuth Tungstate (Bi_2.15WO₆) In Alkaline Condition

Bi_2+xWO₆（x=0-2.2）is a group of photocatalysts that have been extensively used to treat various contaminants because of their narrow bandgaps and special crystalline structure.However,till now,activation of the O-O bonds on the surface of Bi_2+xWO₆in the absence of light has been rarely reported yet.In this study,under alkaline conditions.The reactivity and mechanism of Bi_2.15WO₆ in the catalytic oxidation of bisphenol A（BPA）by persulfate（PS）will be investigated.In addition,the reactivity and mechanism involved in the activation of dissolved oxygen by Bi_2.15WO₆ to produce H₂O₂ during electrocatalysis will also be explored.In the absence of light,Bi_2.15WO₆ shows a high reactivity in the catalytic oxidation of BPA by PS under alkaline conditions,and 20 mg L^-1 BPA was completely removed within 60 min at p H 10.0 with the low stoichiometry ratio between consumed PS and removed BPA of only 1.79.The analysis of total TOC indicates that98.4%of soluble BPA has been oxidatively polymerized to BPA polymers.FTIR,Raman,XPS and electrochemical analyses confirm that surface Bi（III）is the reactive site for the adsorption of BPA and PS,which then initiates reactions between BPA and PS.DFT calculations reveal that the O-O bond in PS is activated from 1.397 to 1.555（?）after adsorbing on Bi（III）,followed by H atom transfer（HAT）from BPA to the activated O-O bond with the formation of phenoxy radicals,which then polymerize to BPA polymer.The lower energy barrier of adsorbed BPA（ΔG=0.056 e V）than that of dissolved BPA（ΔG=0.263 e V）further indicates that HAT is more likely to occur from adsorbed BPA than that from dissolved BPA to the activated O-O bond.To further explore the activation of dissolved oxygen on the surface of Bi_2.15WO₆in the absence of light under alkaline conditions,Bi_2.15WO₆ was used as the cathode material,and glucose was used to promote the production of H₂O₂.Our results show that more H₂O₂ is produced with increasing p H values when at the Bi_2.15WO₆electrode of 2.4 V.With the addition of 10 m M glucose,the production of H₂O₂ is greatly increased to 4.5 times（716.8μM）.and among various H donors（eg.sugars and phenolics）,glucose shows the highest reactivity in H donoation to promote the production of H₂O₂.Quenching experiments,UV analysis and electrochemical analyses show that dissolved oxygen is the main oxygen source in the electrocatalytic production of H₂O₂ by Bi_2.15WO₆.O-O forms O₂^·-on the surface of Bi_2.15WO₆,which is then converted to*OOH.In the absence of glucose,*OOH will continue to accept electrons from electrode and is transformed to H₂O via a four-electron pathway.On the other hand,*OOH is converted into adsorbed H₂O₂ after grabbing H from glucose,followed by the subsequent leave from the surface of the electrode with the production of H₂O₂.This study provides new insight for understanding the catalytic reactivity of Bi_2.15WO₆ in the absence of light.