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SSCI-VIDE+CARE+CCA:MTS:FSA:PVE; International audience; Nanoparticles of platinum were dispersed on an oxygen ionically conducting support, Yttria-Stabilized Zirconia (YSZ), on non-doped zirconia and on silica. The role of the support oxygen lattice in the mechanism of propane deep oxidation was investigated by using O-18(2) Temperature-Programmed Desorption, catalytic activity measurements using isotopic oxygen, and isotopic exchange experiments. The results emphasize that the propane combustion mechanism on Pt/YSZ presents a different pathway compared with that involved on Pt/SiO2 and Pt/ZrO2 because, propane is preferentially oxidized by lattice YSZ oxygen species on Pt/YSZ. Strong Pt nanoparticles/YSZ interactions generate a promoted state similar to that observed on polarizations during electrochemical promotion of catalysis.

The effect of electrochemical promotion of catalysis was investigated for the water–gas shift reaction over porous Pt catalyst electrodes interfaced with 8%mol Yttria-stabilized Zirconia. A fuel cell type electrochemical reactor was used at temperatures from 300 °C to 400 °C, under P H 2 O / P CO ratio values from 2.85 to 31. A negative order dependence of the catalytic reaction rate on P CO and a positive one on P H 2 O was found under open-circuit and polarization conditions. Positive potential application (+2.5 V), i.e., O 2− supply to the catalyst surface, causes a small decrease in the catalytic reaction rate, while negative potential application (−1.5 V) results in a pronounced rate increase, up to 200%, with apparent faradaic efficiency values up to 110. The rate increase obtained with negative polarization can be attributed to the weakening of the Pt–CO bond strength but also, to the increase in surface concentration of oxygen ion vacancies near the Pt-gas-support three-phase boundaries necessary for water dissociation.

International audience; Platinum nanoparticles were dispersed by wet impregnation on YSZ (8 mol% Y2O3) an ionically conducting support. The Pt dispersion of a series of catalysts was determined by using H-2 pulse chemisorption. Temperature Programmed Reduction (TPR) experiments were performed to characterize the pre-reduction step before dispersion measurements. Finally, a fast and reliable procedure was defined for the Pt dispersion measurements consisting in a pre-reduction step in hydrogen at 500 degrees C before the H-2 pulse chemisorption performed at -28 degrees C. Reproducible Pt dispersion values were obtained in good agreement with those measured by pulse CO chemisorptions and static volumetric titration. In addition, the combination of Diffuse Reflectance Infrared Fourier Transform (DRIFT) spectroscopy and TPR has evidenced the role of surface oxygen vacancies on YSZ support for both H-2 and CO chemisorptions.