Sensitivity of CO oxidation toward metal oxidation state in ceria-supported catalysts: an operando DRIFTS-MS study

Abstract

The oxidation of carbon monoxide has been studied on pristine CeO₂, Rh–CeO₂, and Pt–CeO₂ powders prepared in one step by solution combustion synthesis (SCS). The reaction was cycled between an oxygen-rich and a CO-rich feed with regard to the stoichiometric conditions. CO₂ production was monitored by mass spectrometry, while the surface species were probed by operando DRIFTS (Diffuse Reflectance Infrared Fourier Transform Spectroscopy). Whereas the reaction starts above 150 °C on CeO₂ and Rh–CeO₂ and does not depend on the state of the surface (oxidized or reduced), the reaction on Pt–CeO₂ shows strong dependency on the initial state and substantial activity is achieved at much lower temperatures with the CO-rich feed. We relate this result to the change in the oxidation state of Pt via strong interaction with ceria.