“Ir-in-ceria”: A highly selective catalyst for preferential CO oxidation

Abstract

An Ir-in-ceria catalyst has been developed, in which most of the iridium particles are embedded in the ceria matrix through the redox reaction between Ce 3+ and Ir 4+, which occurred during co-precipitation (CP). This Ir-CP catalyst exhibited high activity for preferential CO oxidation under excess hydrogen conditions, and the selectivity to CO 2 remained nearly constant, at around 70%, with increasing reaction temperature. Temperature-programmed reduction and in situ diffuse reflectance infrared spectroscopy techniques were used to explore the structure of the Ir-CP catalyst and to correlate it with the catalytic performance. It was found that the CeO 2 support was activated by iridium and formed on the surface the active sites for CO oxidation. Due to the absence of extensively exposed Ir species on the Ir-CP catalyst, H 2 oxidation occurring on the Ir species and the ceria support at high temperatures was significantly suppressed, thus keeping the selectivity to CO 2 at a high level.