M.N. Tsampas

Role of Lattice Oxygen in the Propane Combustion Over Pt/Yttria-Stabilized Zirconia : Isotopic Studies

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 18O2 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.Graphical Abstract

Mixed Ionic–Electronic Conducting Catalysts for Catalysed Gasoline Particulate Filters

A catalyst based on Pd and Rh nanoparticles supported on a Gadolinia-Doped Ceria support, a mixed O2−/e− ionic electronic conductor (MIEC), has been prepared and washcoated in SiC catalyzed gasoline particulate filters (cGPF) prototypes. These filters have been prepared and tested for the aftertreatment of gasoline direct injection engine exhausts. Catalytic performances of various configurations of cGPFs (different catalyst loadings and locations) have been carried out near real conditions and compared with those of a commercial three-way converter TC as well as a monolith washcoated with the same MIEC-supported catalyst. Among all the samples tested, the most promising one is a GPF equipped with a SiC filtration membrane on which a catalytic layer has been washcoated. This cGPF combines good filtering efficiency, due to the membrane, and remarkable catalytic performances in presence of soot and water. The catalytic performance is greater than those of a commercial TC, in spite of a 9 times lower platinum group metal loading. This is attributed to both self-sustained electrochemical promotion and a higher availability of the active sites localized on the membrane.

Ionically Conducting Ceramics for Soot Oxidation Mechanistic Study with 18O2 Isotopic Exchange

This study shows that Yttria-Stabilized Zirconia (YSZ) is an effective catalyst for soot particles oxidation. Soot oxidation already occurs from 270 degrees C. Temperature-Programmed Oxidation experiments with O-18(2) demonstrate the key-role of bulk oxygen species in the oxidation process. To the best of our knowledge, this is the first time that such a result is reported for a purely O-2-ionically conducting ceramic without any redox property. We assume that the soot oxidation takes place via a fuel-cell type electrochemical mechanism at the nanometric scale. Electrochemical oxidation of the soot takes place at the soot/YSZ interface while oxygen electrochemical reaction occurs at the triple phase boundary.

Electrochemical Promotion of Propane Combustion on Highly Dispersed Pt Nanoparticles

Pt nanoparticles, in a size range which varies from 3 to 20 nm, were dispersed in the porosity of a 7.5 µm-thick layer of LSCF-GDC electrode interfaced on a dense GDC membrane. Small positive polarizations (200 µA / 0.8V - 1.2V) can strongly increase the Pt nanoparticles catalytic performance for propane deep oxidation at low temperatures (267°C-338°C). 40%-enhancement of the propane conversion was achieved with apparent Faraday efficiency values up to 85. These results clearly demonstrate that metallic nanoparticles dispersed in the porosity of a mixed ionic electronic conducting electrode can be electropromoted.