Carbon nanodot-modified FeOCl for photo-assisted Fenton reaction featuring synergistic in-situ H2O2 production and activation

Achieving efficient production and activation of H2O2 is a promising strategy to enhance the efficiency of heterogeneous Fenton reactions. For this purpose, an ideal heterogeneous Fenton platform was constructed though chemical embedding of carbon nanodots (CDots) onto the surface of iron oxychloride (FeOCl/CDots). Experimental results and theoretical calculations confirmed that CDots acted as the reactive sites for highly effective separation of photogenerated electrons and holes in the FeOCl substrate, whereby the O2 molecules in solution could be synchronously reduced to H2O2 via a two-electron pathway (O2 → O2H → H2O2) on the CDots. Under visible light irradiation, the concentration of H2O2 accumulated to ∼337.2 μmol L−1 in the FeOCl/CDots system, which was almost ∼14 times higher than that using FeOCl alone. Moreover, the FeOCl substrate with abundant Fe2+ could directly capture and activate the H2O2 to produce abundant hydroxyl radical (OH), thereby effectively avoiding the H2O2 mass transfer limitation encountered in traditional heterogeneous Fenton reactions. In experiments with a typical organic contaminant (p-chlorophenol), the oxidation rate and mineralization efficiency in this Fenton system were ∼4 and ∼6 times higher than that achieved using FeOCl alone.