Real roles of FeOCl nanosheets in Fenton process

The discovery of valid catalytically active species in a catalytic system contributes to a more comprehensive understanding of the catalytic process and may improve its efficiency. Iron oxychloride (FeOCl) has been reported as an excellent novel Fenton-like catalyst. However, the nature of its outstanding activity remains highly uncertain. Herein, we clearly elucidate that FeOCl involves a homogeneous iron species in the Fenton and photo-Fenton processes, which plays a significant role in the reaction. It is also emphasized that the interaction of FeOCl with water is closely related to the dissolution of iron. Importantly, neglecting the acidic environment created by FeOCl when evaluating the contribution of dissolved iron-induced homogeneous reactions is a crucial reason for underestimating the homogeneous reactions. Hence, FeOCl can be considered a precatalyst for slow transformation in a homogeneous Fenton catalyst. This study contributes to the first insight into the role of dissolved iron in FeOCl-based AOP and suggests an extension of the role of structural features of FeOCl in catalytic processes. Most researchers believe that the high catalytic activity of FeOCl originates from its unique structure. In this study, we show that dissolved iron contributes significantly to the catalytic activity of FeOCl in the Fenton and photo-Fenton processes.