Cooperative effect of Pt and Cu on CeO2 for the CO-PROX reaction under CO2–H2O feed stream

Abstract

Catalyst improvement for the preferential oxidation of CO (CO-PROX) is essential in developing efficient fuel cell technologies. Here, we investigate the promotion of the Cu/CeO2 system with Pt, prepared by impregnation and alcohol-reduction methods, in the CO-PROX reaction under ideal and realistic feed compositions. The high Pt dispersion in PtCu/CeO2 prepared by impregnation led to a CO conversion of 62% and CO2 selectivity of 83% at 50 °C under a feed stream composed of H2/CO/O2, while monometallic Cu/CeO2 and Pt/CeO2 showed negligible activity at these conditions. By adding CO2–H2O to the feed stream, PtCu/CeO2 catalysts prepared by both methods presented similar activity. The maximum CO conversion temperature was shifted to 100 °C. Under these conditions, Cu/CeO2 was inactive, and Pt/CeO2 showed identical conversion but lower CO2 selectivity. In-situ XANES revealed that fast oxidation of Cu species at low temperatures is responsible for Cu/CeO2 deactivation, while preferential adsorption of CO on Pt0 sites in PtCu/CeO2 avoided deactivation. The use of deactivation-resistant Pt sites as complimentary sites for CO activation associated with improved oxygen mobility over Cu–CeO2 surface proved to be an effective strategy for CO-PROX under H2O/CO2 feed stream at low temperatures.