Hydrothermal synthesis and characterization of surface-modified δ-MnO2 with high Fenton-like catalytic activity

•Surface modified δ-MnO2 was synthesized by a simple hydrothermal method.•It exhibited high Fenton-like catalytic activity.•The adsorbed C6H5–COO− on δ-MnO2 enhanced its catalytic activity.

Surface-modified δ-MnO2 with a hierarchical structure was synthesized via a hydrothermal redox reaction between toluene and KMnO4. Toluene is oxidized to produce benzoic acid which rapidly adsorbs onto the surface of δ-MnO2. The δ-MnO2 sample prepared with toluene exhibited a much higher catalytic activity for the Fenton-like oxidation of methylene blue in aqueous solution than that prepared without toluene. The enhanced catalytic activity might be attributed to the surface-bound persistent free radicals produced from the electron transfer from the adsorbed C6H5–COO− to Mn(IV).