Mechanism insight into oxygen vacancy-dependent effect in Fe₁/TiO₂ single-atom catalyst for highly enhanced photo-Fenton mineralization of phenol

This study develops a highly efficient Fe₁/TiO₂-O_V single-atom catalyst to explore the synergistic effect in the photo-Fenton mineralization of phenol. Via using diverse in-situ spectroscopies and density functional theory calculations, the catalytic mechanism is unraveled. That is, oxygen vacancies can significantly accelerate photogenerated charge separation and oriented delivery to Fe₁ single atoms for fast generation of reactive oxygen species, as well as promote the selective adsorption/activation of phenol. As a result, the C-H bonds on phenol were deeply oxidized (conversion: > 91%), accompanied by the mineralization of the benzene ring, with CO₂ and H₂O as end products (mineralization rate: 66%). Such concerted catalysis between Fe single atoms and oxygen vacancies results in a high reactivity for phenol photo-Fenton mineralization, which is superior to most reported transition-metal-based catalysts. Our finding is expected to provide guidance for designing high-efficiency heterogeneous catalysts in the photo-Fenton catalytic process.