Surface configuration modulation for FeOx-CeO2/γ-Al2O3 catalysts and its influence in CO oxidation.

• The influence of surface configuration over FeCe/Al catalysts was studied. • The existence states and content for each coordinated FeO x species was determined. • Clustered FeO x was identified as the main active species for CO oxidation. The surface configuration of a catalyst, including the present state, coordination environment and related content of the active and additive species, has dominant effect on its physicochemical properties and catalytic performance. Herein, two types of FeCe/Al catalysts with different surface configurations, FeCe/Al-CI (co-impregnation) and FeCe/Al-SI (stepwise impregnation) were synthesized by adjusting the preparation conditions. Both catalysts together with the reference sample Fe/Al and Ce/Al were characterized by means of XRD, BET, TEM, EPR, UV–vis, Mössbauer spectra, H 2 -TPR and XPS. The results showed that (1) in both impregnation modes, ceria presented as small particles, while the iron species existed in two forms: the isolate state (tetrahedral coordination), cluster state (octahedral coordination); (2) iron species in different existence state can be characterized qualitatively or quantitatively via EPR, UV–vis and Mössbauer spectra, and the contents of FeO x clusters follows: FeCe/Al-SI < FeCe/Al-CI < Fe/Al. (3) With the help of HNO 3 leaching operation, FeO x clusters were identified as the main active species for CO oxidation. Although Fe/Al sample contained the highest concentration of active cluster FeO x species, the deficiency of Fe-O-Ce structures led to the lowest number of surface oxygen, Ce3+ and Fe2+ species, which resulted in poor CO oxidation activity for Fe/Al catalyst. [ABSTRACT FROM AUTHOR]