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

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 H 2 O 2 to switch from the formation of Fe III complexes towards direct generation of Fe IV . Fe IV intermediates oxidize H 2 O 2 to &z.rad;O 2 − / 1 O 2 , 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 &z.rad;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. WO 3− x switched the reaction of Fe II with H 2 O 2 from the formation of Fe III towards the direct generation of Fe IV . Fe IV was reduced to Fe III /Fe II by electrons localized in the t 2g orbitals of WO 3− x , which favored the generation of &z.rad;O 2 − , &z.rad;OH, and 1 O 2 .