Identifying the Role of Surface Hydroxyl on FeOCl in Bridging Electron Transfer toward Efficient Persulfate Activation.

FeOCl is a highly effective candidate material for advanced oxidation process (AOP) catalysts, but there remain enormous uncertainties about the essence of its outstanding activity. Herein, we clearly elucidate the mechanism involved in the FeOCl-catalyzed perdisulfate (PDS) activation, and the role of surface hydroxyls in bridging the electron transfer between Fe sites and PDS onto the FeOCl/H 2 O interface is highlighted. ATR-FTIR and Raman analyses reveal that phosphate could suppress the activity of FeOCl via substituting its surface hydroxyls, demonstrating the essential role of hydroxyl in PDS activation. By the use of X-ray absorption fine structure and density functional theory calculations, we found that the polar surface of FeOCl experienced prominent hydrolyzation, which enriched abundant electrons within the microarea around the Fe site, leading to a stronger attraction between FeOCl and PDS. As a result, PDS adsorption onto the FeOCl/H 2 O interface was obviously enhanced, the bond length of O-O in adsorbed PDS was lengthened, and the electron transfer from Fe atoms to O-O was also promoted. This work proposed a new strategy for PDS-based AOP development and a hint of building efficient heterogeneous AOP catalysts via regulating the hydroxylation of active sites.