Oxygen-Vacancy-Rich Fe@Fe3O4 Boosting Fenton Chemistry

Iron-based materials are widely applied in Fenton chemistry, and they have promising prospects in the processing of wastewater. The composition complexity and rich chemistry of iron and/or oxides, however, hamper the precise understanding of the active sites and the working mechanism, which still remain highly controversial. Herein, iron oxides of four different model systems are designed through a conventional precipitation method plus H-2 reduction treatment. These systems feature Fe@Fe3O4 with abundant oxygen vacancy, Fe-0 and Fe3O4 particles with interface structures, and Fe3O4-dominated nanoparticles of different sizes. These materials are applied in the decomposition of methyl orange as a model reaction to assess the Fenton chemistry. The Fe@Fe3O4 with core-shell structures exhibits significantly higher decomposition activity than the other Fe3O4-rich nanoparticles. A thin Fe3O4 layer formed by auto-oxidation of iron particles when exposed to air can boost the activity as compared with the Fe-0 and Fe3O4 particles with interface structures but poor oxygen vacancy. The unique hetero-structure with the co-existence of both metallic iron and oxygen vacancy displays excellent redox propensity, which might account for the superior Fenton activity. This finding provides a new perspective to understand and design highly efficient iron-based Fenton catalysts.