Oxygen vacancy modulated interface chemistry: identifying iron(iv) in heterogeneous Fenton reaction

Abstract

Introducing transition-metal oxides as co-catalysts into classical Fenton chemistry holds great promise for improving the recycling of iron species. However, the underlying chemistry that controls the generation and transformation of ferryl species (Fe^IV) during such heterogeneous Fenton reactions is not fully understood. Herein, we modulated oxygen-vacancy-enriched WO_3−x and identified surface Fe^IV species using in situ spectroscopy and density functional theory calculations. Direct spectroscopic evidence shows that WO_3−x caused the reaction of Fe^II with H₂O₂ to switch from the formation of Fe^III complexes towards direct generation of Fe^IV. Fe^IV intermediates oxidize H₂O₂ to ˙O₂⁻/¹O₂, accompanied by the production of Fe^III. Fe^III is reduced to Fe^II by the electrons localized in the t_2g orbitals of WO_3−x, stimulating the generation of ˙OH. This study opens a new chapter in the mechanistic understanding of Fe^IV formation and extends the development of co-catalysts via surface engineering in remediation techniques.