Efficient Decontamination and Detoxification of Phenols by Photocatalytic Cqds@Ag3po4: Re-Insights into the Targeted Reduction and Coupling Processes of ·O2- and 1o2

Abstract

Photogenerated carrier separation, generation of active oxygen species, and effective utilization are critical factors in photocatalysis. Here we develop a carbon quantum dots-modified silver phosphate (CQDs@Ag3PO4) photocatalyst with a high visible light absorption threshold（λ ≤ 565 nm) and narrowed band gap (Eg = 2.25 eV). The photocatalyst exhibits a removal of 100% for micropollutant of p-nitrophenol (PNP) within 120 min under optimized conditions, simultaneously holds high photocatalytic stability via successive recycles. Quenching experiments, electron paramagnetic resonance spectroscopy characterizations, probe experiments, and comparative tests on TOC removal have confirmed photogenerated carrier was effectively separated. Besides photoinduced holes(h+), singlet oxygen (1O2) and superoxide anion (·O2-) induced by photoinduced electrons and molecular oxygen are the primary reactive species involved in the aerobic system. Through HPLC-MS and Fukui Function, it reveals the targeted reductionand advanced oxidation role of ·O2-, realizing decontamination and detoxification of PNP. Moreover, replacement of pollutant degradation by 1O2-induced coupling reaction provides a novel idea for water remediation. Accordingly, four PNP elemination pathways were proposed, and the key intermediates had low toxicity predicted by T.E.S.T. software.Conclusively, this work deepens the understanding of selective degradation of pollutant and provides a strategy for pollutant control with solar energy utilization.

Keywords: Visible photocatalysis, Silver phosphate, Carbon quantum dots, Superoxide anion, Singlet oxygen