Thin interfacial film spontaneously produces hydrogen peroxide: mechanism and application on perfluorooctanoic acid degradation

An effective decontamination method for soils remediation is a long-standing challenge. Herein, hydrogen peroxide (H2O2) was spontaneously produced in thin films generated by evaporating almost all the water. H2O2-sensitive test strips and oxidation of 2-hydroxybenzophenone to 2-hydroxyphenyl benzoate confirmed the generation of H2O2. Experiments in which reaction time and temperature were varied and established dependence of H2O2 production on the long-lasting thin films. H2O2 production was independence of irradiation and oxygen from air or dissolved oxygen. Spin-trapping probe experiments suggested that electric fields at the thin interfacial films enabled OH- to hydroxyl radicals and further recombination to H2O2. As a proof-of-principle experiment, perfluorooctanoic acid (PFOA) was effectively degraded on the thin films without catalysts and UV irradiation could further facilitate the degradation. A degradation mechanism was proposed involving the PFOA radicals on thin interfacial films and the subsequent decomposition of the radicals with successive loss of CF2. These findings have important implications for the development of decontamination method for soils remediation based on thin films, because thin film formats are ubiquitous at the surface of soils and when aerosols falling onto a substrate.