Platinum-Iron(II) Oxide Sites Directly Responsible for Preferential Carbon Monoxide Oxidation at Ambient Temperature: An Operando X-ray Absorption Spectroscopy Study

Operando X-ray absorption spectroscopy identified that the concentration of Fe2+ species in the working state-of-the-art Pt-FeOx catalysts quantitatively correlates to their preferential carbon monoxide oxidation steady-state reaction rate at ambient temperature. Deactivation of such catalysts with time on stream originates from irreversible oxidation of active Fe2+ sites. The active Fe2+ species are presumably Fe+2O-2 clusters in contact with platinum nanoparticles; they coexist with spectator trivalent oxidic iron (Fe3+) and metallic iron (Fe-0) partially alloyed with platinum. The concentration of active sites and, therefore, the catalyst activity strongly depends on the pretreatment conditions. Fe2+ is the resting state of the active sites in the preferential carbon monoxide oxidation cycle.

Automated summary

Operando X-ray absorption spectroscopy identifies a quantitative correlation between the concentration of Fe2+ species in Pt-FeOx catalysts and their carbon monoxide oxidation steady-state reaction rate. Deactivation of the catalysts occurs due to irreversible oxidation of active Fe2+ sites. Active Fe2+ species, presumed to be Fe+2O-2 clusters in contact with platinum nanoparticles, coexist with spectator trivalent oxidic iron (Fe3+) and partially alloyed metallic iron (Fe-0). The concentration of active sites and catalyst activity strongly depend on the pretreatment conditions. Fe2+ is the resting state of the active sites in the carbon monoxide oxidation cycle.