Peroxydisulfate Activation and Singlet Oxygen Generation by Oxygen Vacancy for Degradation of Contaminants

Oxygen vacancies (OVs) play a crucial role in the catalytic activity of metal-based catalysts; however, their activation mechanism toward peroxydisulfate (PDS) still lacks reasonable explanation. In this study, by taking bismuth bromide (BiOBr) as an example, we report an OV-mediated PDS activation process for degradation of bisphenol A (BPA) employing singlet oxygen (O-1(2)) as the main reactive species under alkaline conditions. The experimental results show that the removal efficiency of BPA is proportional to the number of OVs and is highly related to the dosage of PDS and the catalyst. The surface OVs of BiOBr provide ideal sites for the inclusion of hydroxyl ions (HO-) to form Bi-III-OH species, which are regarded as the major active sites for the adsorption and activation of PDS. Unexpectedly, the activation of PDS occurs through a nonradical mechanism mediated by O-1(2), which is generated via multistep reactions, involving the formation of an intermediate superoxide radical (O-2(center dot-)) and the redox cycle of Bi(III)/Bi(IV). This work is dedicated to the in-depth mechanism study into PDS activation over OV-rich BiOBr samples and provides a novel perspective for the activation of peroxides by defective materials in the absence of additional energy supply or aqueous transition metal ions.

Automated summary

This study presents a mechanism of PDS activation over OV-rich BiOBr samples, where a nonradical mechanism mediated by O-1(2) is utilized for BPA degradation. The surface OVs of BiOBr provide ideal sites for the inclusion of hydroxyl ions, leading to the formation of Bi-III-OH species that act as active sites for PDS activation. This work offers a novel perspective for the activation of peroxides by defective materials without additional energy supply or aqueous transition metal ions.