Synergy between hydrogen and ceria in Pt-catalyzed CO oxidation: An investigation on Pt-CeO2 catalysts synthesized by solution combustion

Pt-CeO2 catalysts were prepared by solution combustion synthesis (SCS), a simple and fast one-pot method, using glycine or oxalyl dihydrazide (ODH) as the fuel and Pt chloride,or nitrate as the metal precursor. The samples were characterized by ICP-OES, N-2 volumetry, XRD, XPS, aberration-corrected (S)TEM, CO-DRIFTS and microRaman spectroscopy. The SCS catalysts were evaluated in CO oxidation and preferential oxidation (PROX) of CO in H-2 excess, and compared to PtiCeO(2) and Pt/Al2O3 catalysts prepared by incipient wetness impregnation. The glycine fuel yields better results than ODH in terms of Pt dispersion and catalytic performance. The fresh Cl-containing catalysts consist of PtO nanopartides poorly active in CO oxidation, while the catalysts synthesized from Pt nitrate contain highly active Pt delta+ (0 < delta < 2) species in interaction with ceria. Consistently, the most efficient catalyst for H-2-free CO oxidation is the one synthesized from glycine and Pt nitrate. For PROX, the selectivity to CO2 is 100% at low temperature and decreases in a similar way for all the Pt-CeO2 catalysts above ca. 100 degrees C. With respect to H-2-free conditions, the CO PROX activity of the Pt-CeO2 catalysts is considerably enhanced (activity multiplied by up to 60 at 110 degrees C), while the activity gairvis comparatively minor for Pt/Al2O3. We conclude that hydrogen, by increasing the mobility of oxygen species at the surface of ceria, promotes the support-assisted pathway of CO oxidation. (C) 2016 Elsevier B.V. All rights reserved.