Critical role of oxygen vacancies in heterogeneous Fenton oxidation over ceria-based catalysts.

This study examined the relationship between surface oxygen vacancies (OVs) and ceria-based heterogeneous Fenton catalytic activity. Compared with pure iron oxide and ceria, iron-doped ceria with abundant OVs (FeCeOx) exhibits higher rhodamine B (RhB) degradation efficiency (98%) and has a wider applicable pH range (3.0-9.0). The surface hydroxyl radicals are proved to be the predominant reactive species in the oxidation of RhB. Annealing the FeCeOx in an oxygen atmosphere appears to eliminate the OVs, significantly inhibiting the decomposition of H2O2 and the degradation of target pollutants. As multifunctional active sites, OVs are energetically more favorable for the adsorption of reactants than other sites, due to their high electron density. They not only accelerate the Fe(III)/Fe(II) cycle, they also immediately activate H2O2, dissolved oxygen or even water molecules to produce oxidative species, which accounts for the ideal degradation of RhB in the heterogeneous Fenton system. This study clarifies the mechanism of the ceria-based heterogeneous Fenton and provides a better understanding of the surface design of heterogeneous Fenton catalysts.