Persulfate promoted visible photocatalytic elimination of bisphenol A by g-C3N4-CeO2 S-scheme heterojunction: The dominant role of photo-induced holes

In the last few years, coupling heterogeneous photocatalysis with persulfate (PDS) activation process is an efficient approach to generate abundant reactive oxidative species towards organic contaminant removal in water, however, the key role of PDS in photocatalytic process remains ambiguous. Herein, a novel g-C3N4-CeO2 (CN-CeO2) step-scheme (S-scheme) composite was constructed to photo-degrade bisphenol A (BPA) with the presence of PDS under visible irradiation. At 2.0 mM PDS, 0.7 g/L CN-CeO2 and natural pH 6.2, 94.2% of BPA could be eliminated in 60 min under visible light (Vis) illumination. Aside from the previous view of free radical generation, it tends to assume that most of PDS molecules acted as electron sacrificial agents for capturing photoinduced e(-) to form sulfate ions, greatly improving the charge carrier separation and thus enhancing the oxidation capacity of nonradical hole (h(+)) for the removal of BPA. Good correlations are further found between the rate constant and descriptor variables (i.e., Hammett constant sigma(-)/sigma(+) and half-wave potential E1/2), exhibiting selective oxidation for organic pollutants in the Vis/CN-CeO2/PDS system. The study brings more insights into mechanistic understanding of persulfate-enhanced photocatalytic process for addressing water decontamination.