Facet‐Dependent Activity of Fe ₃ S ₄ Crystal in Peroxydisulfate Activation for Organic Pollutants Degradation

ABSTRACT Iron sulfides (Fe _x S _y ) possess excellent capacities for activating peroxydisulfate (PDS) to degrade organic pollutants from wastewater owing to their highly efficient circulation of Fe(III)/Fe(II), but the intrinsic facet‐activity relations are still unclear to date. Herein, we employed the FLO‐Fe ₃ S ₄ with a flower‐like structure and exposed [001] facet, and OCT‐Fe ₃ S ₄ with octahedral morphology and exposed [1‐21] facet as catalysts for activating PDS to degrade clothianidin (CLO). Results show that FLO‐Fe ₃ S ₄ exhibits significantly enhanced catalytic activity, with a CLO degradation rate of 0.4270 min ⁻¹ , which is 4.4 times higher than that of OCT‐Fe ₃ S ₄ . The superior reactivity of FLO‐Fe ₃ S ₄ can be attributed to its longer Fe−S bonds, making them more prone to breaking and releasing more Fe ions for boosting homogeneous PDS activation. Moreover, the shorter Fe−S bond of OCT‐Fe ₃ S ₄ alleviates Fe dissolution, thereby enhancing its catalytic stability and heterogeneous catalytic reaction. Theoretical simulations reveal that the [001] facet of FLO‐Fe ₃ S ₄ favors the adsorption of PDS and provides more electrons to decompose PDS compared with the [1‐21] facet of OCT‐Fe ₃ S ₄ . Overall, this work delves into the intrinsic facet‐activity relations for Fe ₃ S ₄ crystals on PDS activation and further unravels the overlooked role of crystal Fe−S length on catalytic reaction.