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The non-faradaic electrochemical modification of catalytic activity (NEMCA effect) or the electrochemical promotion of catalysis (EPOC) has been investigated thoroughly for more than 120 catalytic reaction systems [1,2]. In electrochemical promotion studies, the conductive catalyst-electrode is in contact with an ionic conductor and the catalyst is electrochemically promoted by applying a current or potential between the catalyst film and a reference electrode. Numerous surface science and electrochemical techniques have shown that EPOC is due to the electrochemically controlled migration of promoting or poisoning ionic species (O2-in case of YSZ) between the ionic conductor and the gas exposed catalytic surface [1]. Propene is one of the major unburnt hydrocarbons containing in diesel cars exhausts. The most effective materials for propene combustion are Platinum-Group Metals. In spite of their high efficiency, these catalysts cannot be considered in the medium-term due to their excessive cost, which makes necessary stages of recovery and recycling [1]. Ag-based catalysts represent a possible alternative. This study reports the electrochemical promotion of the propene combustion on Ag films deposited on 8 mol% Y2O3 stabilized ZrO2 solid electrolyte, an O2-ionic conductor. Nanostructured electrochemical catalysts were prepared by screen-printing and reactive Physical Vapor Deposition (PVD) method. Screen-printing technique is a flexible tool to prepare few µm thick porous films at low cost whereas extremely thin coatings of Ag can be produced by PVD. Thickness and porosity of Ag coatings were modified by changing the deposition parameters (duration and pressure for PVD, nature of the ink and calcination temperature for screen-printing) to optimize the catalytic properties. Catalytic and electrocatalytic tests have been carried out in a quartz reactor [3] which operated under continuous flowing conditions at atmospheric pressure. The catalytic activity was monitored in a temperature range of 100 to 400oC under lean-burn conditions, as encountered in Diesel exhausts. The most active Ag films were also evaluated under closed circuit conditions (± 2V) in order to measure the effect of polarisation between the silver working electrode and an Au reference electrode. Both electrodes were exposed to the same atmosphere in a single chamber configuration. The catalytic activity of samples is depicted in Figure 1. All Ag coatings are effective from around 200°C. The catalytic performances were correlated with the microstructure of the films. Furthermore, the propene combustion was found to be electropromoted on the most active Ag films at low temperature with Faradaic efficiencies larger than 100. References: [1] C.G. Vayenas, S. Bebelis, C. Pliangos, S. Brosda and D. Tsiplakides, Electrochemical Activation of Catalysis: Promotion, Electrochemical Promotion, and Metal-Support Interactions, Kluver Academic / Plenum Plublishers, New York, 2001. [2] A. Katsaounis, J. Applied Electrochemistry 40 (2009) 885-902. [3] P. Vernoux, F. Gaillard, L. Bultel, E. Siebert and M. Primet, Journal of Catalysis 208 (2002) 412-421. Figure 1

MICROSCOPIE+ATARI:CARE:ECI2D+FCA:MAO:GFE:SLO:CGE:PVE:LMA:PGE; International audience; High spatial resolution studies of ceria and ceria based catalysts by aberration corrected Environmental Transmission Electron MicroscopyF.J. Cadete Santos Aires1, T. Epicier2, M. Bugnet2, M. Aouine1, Z.Wu3, A. Gänzler4, G. Ferré1, M. Casapu4, J.D. Grunwaldt4, S. Loridant1, C. Geantet1, P. Vernoux1, L. Massin1, P. Gélin11 Université de Lyon, UCBL Lyon 1, IRCELYON UMR 5256 CNRS, 2 Avenue Albert Einstein, 69626– Villeurbanne Cedex, France.2 Université de Lyon, INSA-Lyon, UCBL Lyon 1, MATEIS UMR 5510 CNRS, 7 Avenue Jean Capelle, 69626 – Villeurbanne Cedex, France.3 Chemical Science Division, Center for Nanophase Materials Science, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA.4 Institute for Chemical Technology and Polymer Chemistry (ITCP), Karlsruhe Institute of Technology (KIT), Engesserstraße 20, 76131 Karlsruhe, Germany.Ceria (CeO2) is a rather versatile material extensively used in catalysis (as a catalyst or as a catalyst support) due to its redox properties and oxygen mobility capabilities. Despite exhaustive literature on its structural and chemical properties, in depth atomic scale surface analysis in environmental (realistic) conditions is lacking. This is essential to gain crucial, and otherwise unavailable, insight into the surface reactivity mechanisms driving the catalytic performance (activity, selectivity, stability, active sites and species, …). The advent of environmental transmission electron microscopes (ETEM) equipped withadvanced accessories such as an aberration corrector and a high speed camera opened these perspectives. It is now possible to follow in situ (variable P and T), almost in real-time and at subnanometer resolution the evolution of the morphology, the structure and the chemistry of the supported nanoparticles, of the support and of their interface. In particular, the termination of the surfaces, the mobility of the surface atoms, the local chemical composition and the redox state can be analysed down to the atomic level in most favourable cases.Here we present dynamic in situ studies dealing with issues directly related with the surface termination and mobility of ceria and with the evolution of metallic species supported on ceria for different catalyticapplications:(i) Atomic scale study of the surface mobility of CeO2 nanocubes under gaseous environments;(ii) Tuning in situ the noble metal dispersion in Pt/CeO2 diesel oxidation catalysts;(iii) Evolution of Ir/CeO2 catalysts during methane steam reforming.The studies were performed within the Ly-EtTEM (Lyon Environmental and tomographic Transmission Electron Microscope), a 80-300 kV TITAN objective lens Cs-corrected Environmental TEM from FEI, equipped with a GATAN high resolution Imaging Filter (GIF), a SDD XMaxN EDX spectrometer (Oxford Instruments) and a high-speed CCD Gatan OneViewTM camera, in varying pressure and temperature conditions using a Wildfire sample holder and SiNx nanochips from DENS Solutions.The authors are thankful for funding from INSA Lyon through a BQR project THERMOS, from the IMUST project at University of Lyon and IFPen (Solaize, F), from the German Federal Ministry for Economic Affairs and Energy (BMWi: 19U15014B) as well as from the DFG (High-Output Catalyst Development Platform, INST 121384/16-1), from the French National Research Agency for financial support of the ORCA and 3DCLEAN projects 14-CE22-0011-02 and 15-CE09-0009-0 respectively) and from the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, Chemical Sciences, Geosciences, and Biosciences Division. The electron microscopy work presented here was performed on a FEI Titan ETEM at the Centre Lyon–St-Etienne de Microscopie (www.clym.fr).

SSCI-VIDE+CARE+AGF:PVE; International audience; None

SSCI-VIDE+CARE+IKL:PVE; International audience; Studies of CH4 oxidation are of special interest due to the difficulty in activating this particular hydrocarbon, to the demand of an active catalyst at low temperatures (T50 at 300oC) as well as due to possible deactivation of the catalyst upon exposure at higher temperatures. To address these issues, we have used Electrochemical Promotion of Catalysis (EPOC) which was discovered in the early 80's and has been studied for more than 100 catalytic systems. EPOC allows the controlled enhancement of the catalytic activity by potential or small current application between a catalyst (working electrode) supported on a solid electrolyte and an auxiliary electrode. In this study, the use of Pd nanoparticles (2-4 nm) as well as the use of nanodispersed Pd/Co3O4 and Pd/MnO2 catalysts deposited on O2- conductors (YSZ and CGO) is described. The aim is to demonstrate the feasibility of EPOC with nanodispersed catalysts and to enhance the reaction rate at temperatures lower than those that have been observed in previous studies.

SSCI-VIDE+CARE+PVE:ABO:AMV:DLG:SPR:CGO:BDA; International audience; Nature chimique des émissions particulaires, primaires et secondaires

SSCI-VIDE+CARE+DLG:SNS:PVE; National audience; La réduction sélective catalytique (RSC) des NOx par le CH4 se présente comme une technologie très intéressante par la dépollution des NOx émis par moteurs à combustion interne au gaz naturel. Des zéolithes contenant différents métaux (Pd, Co, In ou Ga) sont considérées comme des matériaux prometteurs grâce à des paramètres structuraux et chimiques ajustables sur mesure, comme la taille et forme des pores, l’acidité ou la possibilité de modifier le cation compensateur par échange ionique ou imprégnation [1]. Dans ce travail, nous proposons différentes structures zéolitiques (FER, MOR, ZSM-5, BEA) en systèmes monométalliques (Co ou Pd) ou bimétalliques (Co et Pd) pour la RSC des NOx par le CH4. Les performances catalytiques sont mesurées entre 300°C et 700°C et les catalyseurs ont été vieillis sous mélange réactionnel à 700 ºC (12 heures). Les catalyseurs synthétisés associent du Pd à l’état cationique (échange ionique ≈ 0,5 % wt.) au Co déposé sur la surface (imprégnation ≈ 2 % wt.) sur différentes supports zéolitiques. La Figure 1 montre les performances catalytiques des différentes formulations zéolitiques étudiées. L’oxydation de CH4 commence vers 350 °C et atteint 80 % à 500 °C. L’activité catalytique est similaire pour toutes les zéolithes. Par rapport à la production de N2, les catalyseurs à base de MOR (2-Co-0.5Pd-MOR) et FER (2-Co-0.5Pd-FER) présentent les meilleures performances (33 % et 28 % de réduction de NOx en N2, respectivement) avec une pauvre activité du catalyseur à base de ZSM-5 (2-Co-0.5Pd-ZSM5). Par contre, à l’état vieilli, le catalyseur devient moins sélectif et produit plus de NO2 (pas montré) et la conversion de NOx descend à 3 % et à 17 % pour MOR et FER, respectivement. La désactivation si différente entre les deux catalyseurs peut être expliqué par la différent taille des pores (les rapports Si/Al ainsi que les surfaces spécifiques sont similaires (Figure 1)). Les petits pores peuvent servir pour mieux stabiliser les métaux échangés et pour protéger du frittage. Ces hypothèses ont été confirmées par la microscopie électronique en transmission (MET) réalisée sur ces catalyseurs après réaction. D’abord, le Co reste sous forme de nanoparticules en surface des cristallites de zéolithe sur le catalyseur à base de FER. La majorité des nanoparticules présentent une petite taille (< 2 nm). De plus, aucune particule de Pd n’a pas été observée, ce qui suggère que le Pd reste à l’état cationique. Au contraire, sur le catalyseur à base de MOR après vieillissement, de grosses particules agglomérées de Pd (> 20 nm) sont clairement observées, démontrant que le Pd n’est plus dans le réseau de la zéolithe. Cette étude a permis d’évaluer les performances catalytiques des catalyseurs zéolitiques dans des conditions proches à ceux des moteurs au gaz naturel travaillant en excès d’oxygène. Ces catalyseurs permettent d’obtenir une conversion des NOx en N2 élevée. Après vieillissement, l’activité baisse fortement, ce qui a été liée à la différente structure poreuse des zéolithes. [1] F. Lonyi, H.E. Solt, Z. Paszti, J. Valyon, Appl. Catal. B. 150-151 (2014) 218-229.

SSCI-VIDE+CARE+PVE; International audience; None

SSCI-VIDE+CARE+PVE; National audience; Le défi des oxydes d’azote (NOx) consiste à développer des catalyseurs capables de sélectivement réduire les NOx en azote dans un échappement Diesel qui contient un large excès d’oxygène et des traces de réducteurs (hydrocarbures imbrûlés et monoxyde de carbone). Deux solutions technologiques ont été développées et équipent les véhicules Diesel Euro 6 en Europe : le procédé de stockage-réduction des NOx (NSR : NOx Storage-Reduction) et la réduction catalytique sélective des NOx par l’urée (Urea-SCR). Ces deux systèmes catalytiques utilisent une post-injection d’agent réducteur, l’urée (SCR) ou le gazole (NSR), pour réduire les NOx. De plus, le procédé SCR nécessite un réservoir supplémentaire d’urée et un injecteur tandis que le système NSR engendre une surconsommation de carburant. Cette présentation comparera les deux technologies et discutera notamment des récentes études publiées sur les mesures d’émissions de véhicules Diesel Euro 6 en condition réelle de roulage.

SSCI-VIDE+CARE+PVE; International audience; Electrochemical Promotion of Catalysis (EPOC), also called Non-Faradaic Electrochemical Modification of Catalytic Activity (NEMCA), is a promising concept for boosting catalytic processes and advancing the frontiers of catalysis [1]. This innovative field aims to modify in-operando both the activity and the selectivity of catalysts, in a reversible and controlled manner. EPOC utilizes solid electrolyte materials (ionically conducting ceramics) as catalytic carriers. Ions contained in these electrolytes are electrochemically supplied to the catalyst surface and act as promoting agents to modify the catalyst electronic properties in order to achieve optimal catalytic performance. It thus provides a unique means of varying promoter levels at the metal surface under reaction conditions by simply changing the potential of the catalyst film. The main advantage of EPOC is that the electrochemical activation magnitude is much higher th an that predicted by Faraday’s law. Therefore, EPOC requires low currents or potentials. Moreover, promoting species such as O2- cannot be formed via gaseous adsorption and cannot be easily dosed by chemical ways. The EPOC technology consists in the implementation of catalysis in an electrochemical cell by using electrochemical catalysts which consist of a catalytic layer interfaced on an ionically conducting ceramic support. The latter serves as an electrically controlled source or sink of ionic promoter species that activate and modulate the behavior of the catalytic surface. Figure 1a displays a typical EPOC reactor. The catalytic layer, typically 40 nm to 10 m thick, is deposited on a dense solid electrolyte membrane (Figure 1a). This catalytic layer must be electronic conductor to allow the polarization. Therefore, the catalyst is also an electrode and is then named catalyst-electrode. A counter-electrode and a reference electrode, both catalytically inert, are dep osited on the other side of the membrane (Figure 1a). An electrical current density (1-500 µA/cm2) or potential (2 V) is applied between the catalyst and the counter electrode. The reactants are co-fed over the porous electrochemical catalytic layer. Figure 1b displays a typical example of an EPOC experiment for the propane deep oxidation. The electrochemical catalyst was composed of a Pt thin film deposited by Physical Vapor Deposition (PVD) on a dense membrane of Yttria-Stabilized Zirconia (YSZ), an O2- ionic conductor. A positive current (from +10 up to +500µA) can strongly increase the propane conversion with a non-Faradaic manner, since the activation is up to 300 times higher than that predicted by the Faraday’s law through the electrochemical oxidation of propane. This lecture will give an overview of recent advances of EPOC for environmental applications, such as hydrocarbon oxidation, soot combustion and NOx abatement.

SSCI-VIDE+CARE+PVE; International audience; None

International audience

SSCI-VIDE+CARE+ASR:AGF:AWS:PVE; International audience; ntroductionThanks to the excellent oxygen storage capacity (OSC) ceria-based oxides have gained attention for automotive catalysts, such as Three-Way Converters and diesel soot oxidation catalysts [1]. Some kind of synergistic effects between CuO-CeO2 and CoOx-CeO2 have been reported in ceria-based mixed oxides for soot oxidation [2,3].On these bases and considering our experience in Co3O4-CeO2 mixed oxides for low-temperature VOCs and methane oxidation [4,5], we have considered Co3O4/CuO-CeO2 mixed oxides as good candidate catalysts for diesel soot oxidation. ExperimentalCo3O4-Cu0.05Ce0.95O2- mixed oxides with cobalt loading equal to 10.0, 7.5, 5.0 and 2.5 wt% have been prepared by one pot citrate acid complex sol-gel method and calcined at 550 °C for 5 h. For comparison reason, Co-free Cu0.05Ce0.95O2- oxide was also prepared.Characterizations by XRD, BET, TPR, XPS, Raman and SEM techniques have been performed. Soot oxidation tests were carried out under tight contact by flowing O2 (5% in He) over 25 mg of a mixture of catalyst plus soot, at mass ratio 4:1.Results & discussionCharacterizations of the Cobalt-Cu0.05Ce0.95O2- mixed oxides display the presence of Co3O4 at the surface of the copper-doped ceria. Co3O4 is clearly identified in Raman and XRD spectra as the only Cobalt-present specie. Samples display specific surface between 47 and 63 m2/g with the exception of pure Co3O4 (14 m2/g).Decomposition of Co3O4 is observed during TPR starting at 200°C and under O2-TPD at 650°C. Over Co3O4-Cu0.05Ce0.95O2- samples, three reductions peaks occurs at temperature below 200°C indicating the presence of at least 3 different reducible species. As evidenced by TPO results obtained under tight contact, the presence of Copper in the ceria enhances the performances for soot oxidation: diminution of the T10 (temperature at which 10% of the soot is oxidized) from 440°C to 400°C. Further addition of Cobalt appears to have a positive effect for 2.5 and 5% mass loading (TPO profiles shifted toward lower temperatures) with a maximal performance obtained for 5% loading (T10 of 385°C). Pure Co3O4 is active for soot oxidation as displayed by the cyan curve in figure 1 although not quite much as the 5%Co3O4-Cu0.05Ce0.95O2- formulation. At higher cobalt loading (7.5 and 10%), performances appear to decrease which might be related to the sintering of Cobalt at the catalyst surface. Figure 1 : CO2 production versus temperature during TPO experiments under tight contact and 5%O2/HeFigure 2 : T10 and T50 obtained during TPO experimentsConclusionWe prepared and characterized Co3O4-Cu0.05Ce0.95O2- samples at various cobalt loading (2.5 to 10%) to assess their performances toward soot oxidation. Co3O4 is confirmed as the only cobalt-specie present and is located at the surface of the copper-doped ceria. Co3O4-Cu0.05Ce0.95O2- samples display highly reducible species under TPR experiment which might be involved is soot oxidation activity. The results obtained during TPO indicate that not only does copper-doped ceria displays increased performances toward soot oxidation, but the presence of Co3O4 at a maximum ratio of 5%wt seem to lower again the soot ignition temperature to 385°C.Reference(s)[1] Catalytic Science Series-Vol. 12, Catalysis by Ceria and Related Materials, second edition edited by A. Trovarelli and P. Fornasiero, 2013, Imperial College Press.[2] K. N. Rao, P. Venkataswamy, B. M. Reddy, Ind. Eng. Chem. Res. 50 (2011) 11960.

RX+CARE:ECI2D+GFE:AWS:FBS:SLO:CGE:PVE; International audience; 1. IntroductionEnvironmental regulations on NOx emissions of mobile sources are becoming increasingly demanding. The NOx storage-reduction (NSR) catalytic technology is one of the solution lean-burn engines. NSR catalysts work in cyclic gas-composition conditions. During the first step (lean phase), NSR materials store emitted NOx as nitrates until the surface reaches the saturation threshold. A pulse of fuel post-injection then triggers the short second step (rich phase), during which the reducing conditions lead to nitrate decomposition and release as well as subsequent NOx reduction into N2 and surface regeneration. Ceria is an interesting material since it plays a double function first as a high specific surface area support [1] for platinum group metal (PGM) dispersion and secondly as a NOx trap at low temperature until 350°C. Below 200°C, the NOx storage capacity of ceria is higher than that of barium which is commonly used as a storing agent [2]. In addition, ceria can limit the thermal sintering of Pt nanoparticles [3]. This study aims to deeply characterize the impact of the nature of dopant (Zr and Pr) on the redox properties of ceria-based oxides.2. Experimental/methodologyDifferent compositions of commercial ceria-based oxides were provided by the Solvay Special Chem Company : CeO2, Ce0.49Zr0.51O2 (CZ)) and Ce0,80Pr0,20O2 (CP20). All samples have been calcined at 800°C for 2 h. In-situ X-Ray Diffraction measurements were carried out in an atmosphere-controlled Anton Paar XRK 900 reactor chamber, either under air, N2 or H2, using a Versatile Panalytical X’Pert Pro MPD Diffractometer equipped with a diffracted beam graphite monochromator (Cu Kα radiation) and a 1-dimensional multistrip detector (X’Celerator). Diffractograms were collected at several temperatures from 25 to 750°C and crystallographic parameters were determined by the Rietveld method. Surface and bulk reducibility was characterized by Temperature-Programmed Reduction (TPR) in H2 from room temperature up to 850°C. Oxygen-Temperature-Programmed Desorption (TPD) experiments were also performed to quantify the surface reactivity of the different oxides toward oxygen. Oxygen was adsorbed at 500°C while the desorption was followed in He from RT up to 800°C with an heating ramp of 10°C/min. In-situ Raman spectroscopy was used to determine structural/electronic defects and surface oxygen species of the samples after reducing/oxidizing treatments. Spectra were recorded with a LabRam HR Raman spectrometer (Horiba-Jobin Yvon) at low temperature after oxidation or reduction at 525°C. Three exciting wavelengths were used (514, 633 and 785 nm) and the laser spot was focused using a ×50 long working distance objective. The in-situ Raman spectra were recorded using a THMS600 cell (Linkam) between -196°C and 525°C under 10 % H2-N2, N2 and 10% O2-N2.3. Results and discussionXRD patterns have evidenced the cubic structure (Fm-3m) for CeO2 and CP20 while CZ alsocontains a t’ tetragonal phase. The lattice parameters were extracted from in-situ patterns inair, N2 and H2 as a function of the temperature. The increase of the lattice parameter withrespect to the one measured in air at a given temperature was used to estimate the bulkreducibility. Figure 1a clearly shows that CP20 is reduced in pure H2 from 300°C, instead of400°C for CZ and above 700°C for CeO2. These results are in good agreement with TPRexperiments which evidenced that the surface reduction of doped ceria is promoted by theinsertion of Pr. By the same way during O2-TPD experiments, a low O2 desorption peakbelow 400°C was only observed on CP20. In addition, the capacity of the ceria oxide tochemisorb oxygen was strongly improved in the presence of Pr.Beyond confirming the XRD structural characterization, Raman mappings evidenced a highhomogeneity at the micrometer scale. Furthermore, structural defects and oxygen specieswere observed with this technique. In particular, Raman spectra of CP20 oxide highlighted adefects band at 570 cm-1 (Figure 1B) which can be explained by a resonance effect involvinga particular defect stabilized at the oxidized state. The reduction of cations contained in suchdefect modifies its electronic properties inhibiting the resonance effect. Concerning CZsupport, a typical band of Ce3+ was visible after reduction whereas peroxo species wereobserved after re-oxydation contrarily to the other solids.Figure 1. (A) Variation of the fluorite lattice parameter as a function of temperature in pure H2 (B) Evidence of a newdefects band enhanced by Raman Resonance effect for CP20.4. ConclusionStructure, surface and bulk properties of three different ceria oxides have been deeplyinvestigated in both oxidized and reduced states. The role of the dopants, i.e. Pr and Zr, onthe redox properties in cycling lean/rich conditions encountered in NSR processes will bediscussed.5. References[1] Z. Say, E.I. Vovk, V.I. Bukhtiyarov, E. Ozensoy, Appl. Catal. B Environ. 142-143 (2013) 89–100.[2] E. Rohart, V. Bellière-Baca, K. Yokota, V. Harlé, C. Pitois, Top. Catal. 42-43 (2007) 71–75.[3] Y. Nagai, T. Hirabayashi, K. Dohmae, N. Takagi, T. Minami, H. Shinjoh, S. Matsumoto, J. Catal. 242 (2006) 103–109.

SSCI-VIDE+CARE+AWS:PVE; International audience; None

SSCI-VIDE+CARE+MBH:FDA:CGU:PVE; International audience; None

SSCI-VIDE+CARE+ACV:PVE; International audience; None

ANALYSE:MICROSCOPIE+ATARI:CARE+DLG:MAO:LMA:PMA:PVE; International audience; 1.IntroductionCatalytic combustion of propane is a key reaction for power generation and engine exhausts control emissions. The interest for ceria-based materials as supports for PGM nanoparticles is growing due to their redox properties. The elucidation of Pd/ceria interactions is crucial to design a catalyst with optimum performances, find proper pretreatments that could boost catalytic performances or setting effective regeneration strategies. This study aims to investigate the impact of a reduction step in H2 at 500°C on the catalytic performance of Pd supported doped ceria catalysts in the propane combustion reaction. Two different oxides based on ceria zirconia (CZ), as a reference TWC support, and GDC, a mixed ionic electronic conductor, have been used to disperse Pd nanoparticles. The catalytic activity of the catalysts was characterized by stoichiometric C3H8 oxidation measurements. The samples were characterized by temperature programmed reduction, H2 static volumetric chemisorption, CO titration and XPS. In addition, the reduction step in H2 was in-situ observed by environmental transmission electron microscopy. Finally, the catalytic results obtained were compared with those of a Pd/ γ-Al2O3 reference catalyst.2.Experimental/methodologyPowdered catalysts were prepared by dispersing Pd nanoparticles (1 %wt.) on a GDC (Pd_GDC) (Ce0.8Gd0.2O2) and a CZ (Pd_CZ) (Ce0.62Zr0.38O2) powder using incipient wetness impregnation. C3H8 catalytic combustion was evaluated under stoichiometric conditions (2000 ppm C3H8 and 10000 ppm O2). The total flow was 300 Nml/h (GHSV=229.300 h-1). Prior to catalytic measurements, the samples were reduced under pure H2 (500 ºC, 1 hour). After cooling down to 25 °C in He, the flow was changed to the reaction mixture. The catalytic combustion of C3H8 was evaluated in two consecutive cycles. Between both cycles, the samples were left under one hour on stream at 500 °C and cooled down in the same reactive atmosphere. Reactants and products were recorded by an IR analyzer and a microGC.3.ResultsFigure 1.a depicts the light-off curves of the Pd_GDC and Pd_CZ catalysts. After the reduction step, catalytic performances of Pd_CZ are slightly better than those of Pd_GDC until reaching 10% of conversion. Then, the two light-off curves intersect and the catalytic properties of Pd_GDC become greater. After the stabilization step (one hour on stream at 500°C), the catalytic performances of the two catalysts drastically decrease. A third light-off curve was recorded (after a second reduction step) that shows that the catalytic performance of Pd_GDC was almost fully recovered. The impact of a reduction step in H2 has been in-situ observed by ETEM on both Pd_CZ and Pd_GDC catalysts (Figure 1b, 1c and 1d). Before reduction, it has been difficult to detect metallic particles (Figure 1.b), suggesting that most of the Pd is oxidized in accordance with TPR and XPS experiments. In H2 at 450°C, a re-dispersion of metallic Pd nanoparticles was observed. On GDC, Pd particles are more flattened shape rather than spherical particles and seem to be in strong interaction with the support (Figure 1.d).Figure 1.- a) Propane conversion curves for the Pd_GDC and Pd_CZ catalysts, and In situ ETEM for the b) Pd_CZ catalyst (20 °C, vacuum), c) Pd_CZ catalyst (450 °C, 1 mbar H2) and d) Pd_GDC catalyst (450 °C, 1 mbar H2)4.DiscussionThe results obtained in this study indicate a beneficial effect of the catalytic activity of the activation in H2 which might be linked to the stabilization, anchoring and high dispersion of metallic Pd particles onto the ceria surface upon reduction in linked with the surface reducibility of GDC and CZ confirmed by TPR experiments. On the other hand, after one hour on stream under the reacting mixture, the higher decay on the catalytic activity for the Pd_GDC catalyst was ascribed to a higher decoration of metallic nanoparticles inside the GDC support and/or by the formation of a Pd-ceria solid solution. This latter assumption is supported by TPR results, ETEM and XPS. Indeed, XPS spectra confirmed that Pd is predominantly in a solid solution form (PdxCeO2-δ), after oxidation step. 5.ConclusionThe catalytic activity can be strongly promoted by a reduction step at 500°C in H2. This effect was not observed on a non-reducible support such as alumina. Surface characterizations of the samples, including in-situ observations in H2 with an environmental transmission electron microscope, have shown that this activation process, in particular on GDC, is linked to the reduction of a surface interaction phase, PdxCeO2-δ. The surface reduction of this oxide allows to finely disperse metallic Pd nanoparticles. AcknowledgmentsThis work was performed in the “Triptic-H” project, partially funded by the French National Research Agency (ANR), ANR-2011-VPTT-003.

SSCI-VIDE+CARE+PVE; International audience; None

SSCI-VIDE+CARE+PVE; International audience; None

SSCI-VIDE+CARE+ASR:ABO:PVE; International audience; As Particulate Matter (PM) vehicle emissions are regulated by US/EU standards, the use of DPF (Diesel Particle Filter) has been widely spread to comply with the regulations. The main problematic associated with DPF comes from its regeneration. Numerous silver supported catalysts have been reported as active materials for soot oxidation [1,2]. Such activity is explained by the ability to provide oxygen to the soot and by the mobility of silver at the surface of the catalyst. We investigated the soot oxidation mechanism by silver nanoparticles supported over a non-reducible, ionic conductor oxide: Yttria-Stabilized Zirconia (YSZ). YSZ is an active support for soot oxidation thanks to its bulk oxygen mobility [3,4]. This study reports the mechanism of soot on Ag/YSZ catalysts by using isotopic temperature programmed oxidation (TP18O2), isotopic isotherm and isotopic oxygen exchange.

SSCI-VIDE+CARE:ECI2D+AWS:CGE:PVE:SLO; International audience; In this work, the origin of the Raman defects band at 570cm(-1) of praseodymium-doped ceria was revisited from in situ spectra using six different exciting lines between 458 and 785nm at low temperatures after oxidizing or reducing treatment. The observation of overtones and the fast change of relative intensity with excitation wavelength were explained by a resonance effect around 514nm, which involved a Pr4+ containing defect stabilized at the oxidized state leading to an absorption band around 530nm. The reduction of Pr4+ cations contained in such defects modifies the electronic properties of praseodymium doped ceria inhibiting the resonance effect. Additionally, the number of D1 defects that involved Pr3+ cations and oxygen vacancies increased allowing them to be distinguished. Copyright (c) 2016 John Wiley

SSCI-VIDE+CARE+ABO:PVE:CGO:BDA; International audience; None

RX+CARE:ECI2D+GFE:AWS:FBS:SLO:CGE:PVE; International audience; Environmental regulations on NOx emissions of mobile sources are becoming increasingly demanding. The NOx storage-reduction (NSR) catalytic technology is one of the solution lean-burn engines. NSR catalysts work in cyclic gas-composition conditions. During the first step (lean phase), NSR materials store emitted NOx as nitrates until the surface reaches the saturation threshold. A pulse of fuel post-injection then triggers the short second step (rich phase), during which the reducing conditions lead to nitrate decomposition and release as well as subsequent NOx reduction into N2 and surface regeneration. Ceria is an interesting material since it plays a double function first as a high specific surface area support1 for platinum group metal (PGM) dispersion and secondly as a NOx trap at low temperature until 350°C. Below 200°C, the NOx storage capacity of ceria is higher than that of barium which is commonly used as a storing agent2. In addition, ceria can limit the thermal sintering of Pt nanoparticles3. This study aims to deeply characterize the impact of the nature of dopant (Zr and Pr) on the redox properties of ceria-based oxides.

International audience; The effect of a reduction step on the catalyticactivity of Pd supported doped ceria catalysts was investigatedfor the propane combustion. Two different oxidesbased on ceria zirconia (CZ), as a reference three-waycatalyst support, and Gadolinia doped ceria (GDC), amixed ionic electronic conductor, have been used to supportPd nanoparticles. The samples were characterized byH2–CO chemisorption, temperature programmed reduction,and XPS. In addition, the reduction step in H2 wasin situ observed by environmental transmission electronmicroscopy. It was found that the catalytic activity of Pdsupported on ceria-based supports can be strongly promotedby a reduction step whereas it does not change onalumina. This effect was attributed, in particular on GDC,to the reduction of a surface interaction phase, PdxCeO2-d,which induces a re-dispersion of metallic Pd nanoparticles.

SSCI-VIDE+CARE+BRM:ABO:NCA:PVE:BDA; National audience; Les émissions des véhicules à moteur thermique sont réglementées par des normes édictées par des états ou groupements d'états. En Europe, toutes les voitures diesel produites à partir de 2011 ont été équipées d'un filtre à particules (FAP), pour respecter la norme Euro 5 puis l’actuelle norme Euro 6 (nombre limite d’émission de particules de diamètre supérieur à 23 nm, PN = 6,0 × 1011 #/km ; masse limite, PM = 4,5 mg / km). La présente étude (Projet CAPPNOR supporté par l’ADEME) vise à acquérir de nouvelles connaissances relatives aux substances à ce jour encore non réglementées (particules ultra fines -Dp < 23 nm-, HAP, NO2…) émises par les véhicules particuliers dans des conditions d'utilisation aussi proches que possible du réelles. Pour ce faire, les émissions de deux voitures à moteur diesel (équipées chacune d’un FAP spécifique) ont été caractérisées sur différents point de fonctionnement, cycles de conduite et phases de régénération. La caractérisation a porté sur la masse et le nombre de particules émises, leur répartition granulométrique, leur morphologie, leur nature chimique ainsi que sur les gaz polluants. Un large panel d'instruments a pour cela été implémenté : un système de dilution, des granulométres, un spectromètre de masse à aérosol, un photomètre pour la mesure en masse du carbone noir et un système de prélèvement sur grille MET pour des analyses par microscopie électronique. Les moteurs diesel équipés d’un FAP émettent des particules principalement lors du démarrage à froid, lors de fortes accélérations et pendant les phases de régénération du FAP. Typiquement, ces particules sont constituées d'un mélange complexe de suie de carbone et de gouttelettes (Dp ~ 200 à 700 nm) contenant des inclusions métalliques (Fe, Ni, Cr, Mn,...). Par ailleurs, les phases de régénération du FAP s’accompagnent d’une forte émission de fines gouttelettes soufrées (Dp < 20 nm) issues d’un processus de nucléation post-échappement et d’une augmentation progressive de la masse émise du carbone noir, Ce dernier correspond à des suies de carbone qui sont émises en raison d’une réduction progressives de l’efficacité du FAP due à sa régénération et contiennent une phase adsorbée d’acide sulfurique hydraté et de composés organiques.

SSCI-VIDE+CARE+DLG:ABO:PVE; International audience; Future changes in Europe regulation (Euro 6c in 2017) concerning particle matter (PM) abatement will probably lead to the implementation of filter devices in direct injection gasoline(GDI) engines. Catalyzed-Gasoline Particulate Filter (cGPF) can be combined with conventional three way converter (TWC) to meet pollutants standards. Electro-promotednano-dispersed catalysts for vehicles exhaust after-treatment is getting growing attention since they can combine electrochemical promotion of catalysis and high metallic active siteavailability. Nano-cell catalysts are composed of nano-electrodes (two different natures of metallic nanoparticles) supported on a mixed ionic-electronic conductor (MIEC). Washcoated MIEC-based catalysts inside mini-GPFs have been tested for GDI exhaust aftertreatment using a bench scale plant. The presence of a membrane in GPFs modifies both, their catalytic and filtering performance. The impact of the membrane, the catalystloading and location as well as the presence of soot particles on the catalytic properties willbe discussed.

SSCI-VIDE+CARE+PVE; International audience; This study reports isotopical labelling experiments during propane oxidation on nanodispersed Pt nanoparticles supported either on Yttria-Stabilized Zirconia, an O2- ionic conductor, or on non-conductive ceramics (ZrO2, SiO2) showing high metallic dispersions. 18O2 Temperature-Programmed Desorption and oxygen exchange experiments have shown that YSZ lattice oxygen species continuously migrate toward the Pt surface to such an extent that the gas phase oxygen adsorption is strongly inhibited [1]. This is not the case when the Pt nanoparticles are supported on ZrO2 or SiO2, where the propane mainly reacts with gaseous oxygen. This underlines the strong impact of the YSZ oxygen species on the propane combustion mechanism. The oxygen ions containing in the support can act as predominant oxidizing species. This finding open new routes to design smart and efficient high surface specific area metal-supported catalysts for hydrocarbon oxidation reactions involved in environmental catalysis.

MICROSCOPIE+ATARI:CARE+MAO:FCA:PVE; International audience; None

SSCI-VIDE+CARE+PVE; International audience; None

National @ CARE+ASR:MAO:FCA:PVE; International audience; Depuis 2011 (norme EURO 5), l'utilisation d'un filtre à particules (FAP) à l'échappement de tous les véhicules Diesel est obligatoire. La présence du FAP permet de grandement diminuer les émissions de particules. Cependant, le filtre doit être régénéré après un certain temps d'utilisation. Cette étude porte sur l'utilisation d'un catalyseur conducteur ionique : la zircone yttriée (YSZ) pour oxyder la suie. Cette céramique, stable chimiquement et thermiquement, est capable d'oxyder la suie via les ions oxygènes de son réseau selon un mécanisme électrochimique de type pile à combustible [1]. Afin de préciser le mécanisme d'oxydation des suies par les ions oxygènes, nous avons réalisé des observations in-situ, à l'aide d'un microscope électronique en transmission environnemental (METE, FEI TITAN), d'un mélange de suie et de catalyseur. Chauffé à 550°C sous vide, aucune oxydation de la suie n'a été observée. Une faible pression d'oxygène a ensuite été introduite, permettant de visualiser in-situ l'oxydation des particules. De nombreuses séquences vidéo ont été réalisées avec une résolution de 1 nm (figure 1). Les résultats soulignent l'importance du contact suie-catalyseur, la réaction d'oxydation se produisant à l'interface suie/catalyseur. Les particules de suie sans contact avec les grains de YSZ ne sont pas oxydées même après plusieurs minutes (figure 1, d). Lors de l'oxydation, les particules de suie se déplacent dans la direction du catalyseur et sont consommée à l'interface. Les lignes de contact entre le catalyseur et les particules de suie ont été estimées entre 20 et 40 nm. Des observations haute résolution ont permis de démontrer que la surface du catalyseur reste inchangée avant et après oxydation. Les différentes observations de l'oxydation de la suie à l'interface suie-catalyseur confirme l'hypothèse selon laquelle le mécanisme d'oxydation fait intervenir les oxygènes du réseau plutôt que ceux du milieux gazeux, en bon accord avec des expériences d'échange isotopique de l'oxygène.

National @ CARE+PVE; International audience; Le post-traitement des véhicules Diesel nécessite, à cause du renforcement des normes européennes, l’utilisation de plusieurs briques successives de dépollution. Depuis la mise en place de la norme Euro6 en 2014, la ligne de post-traitement est composée d’un catalyseur d’oxydation (DOC : pour Diesel Oxidation Catalyst), d’un catalyseur pour la réduction des NOx et d’un filtre à particules (FAP). Deux technologies de réduction des oxydes d’azotes sont actuellement utilisées. La première utilise l’ammoniac comme réducteur (NH3-SCR pour Selective Catalytic Reduction) et la seconde un matériau capable de stocker les NOx sous forme de nitrates et de les réduire en azote lors de post-injections courtes de carburant (catalyseurs NOxTRAP). Les catalyseurs d’oxydation et de réduction des oxydes d’azote contiennent des nanoparticles actives, à base de métaux nobles (Pt, Pd, Rh) ou de transition (Fe, Cu), finement dispersées sur un matériau support de grande surface spécifique. Les performances catalytiques dépendent fortement de l’accessibilité aux gaz polluants des nanoparticules et de leur interaction avec le support. L’adsorption d’impuretés présentes dans l’échappement sur les sites actifs peut entraîner une chute brutale des performances catalytiques. Ces impuretés comme le calcium, le sodium, le magnésium, le phosphore, le potassium, le soufre et le zinc sont issues des carburants, notamment des biodiesel, et des huiles. La suie peut également encrasser les DOC placés en amont des FAP. L’autre principale source de désactivation est le grossissement des sites actifs à cause des phénomènes de coalescence entre nanoparticules qui se déroulent à haute température. Ces pics de températures élevées, notamment atteints lors des régénérations de FAP, peuvent entraîner des réactions entre les nanoparticules métalliques et le support pour former des alliages moins actifs. Un changement de phase cristallographique des supports peut également induire une baisse de porosité et même des phénomènes d’encapsulation des phases actives. Le filtre à particules peut également souffrir de la présence des impuretés inorganiques qui vont s’accumuler sous forme de cendres dans les canaux et encrasser progressivement la zone de filtration. Cette présentation donnera une vision globale des problèmes d’empoisonnement et d’encrassement dans la ligne de post-traitement Diesel au travers de quelques exemples d’études.

SSCI-VIDE+CARE+ABO:LRE:PVE; International audience; Performances of Solid Oxide Fuel Cells (SOFCs) were investigated in triode operation mode under methane steam reforming in presence of H2S. Both the catalytic performances for methane steam reforming and the electrochemical properties of the anode are drastically dropped by the presence of H2S impurities introduced through the use of fuels such as natural gas. Indeed, typically 1-30 ppm H2S content can be observed in natural gas. Conventional Ni-based cermet anode exhibit strong deactivation when exposed to few ppm H2S. This loss is generally attributed to sulfur adsorption on Ni active sites.Triode operation is a novel approach for enhancing the performances of fuel cells and electrolysers. This concept is based on the introduction of a third electrode (auxiliary electrode) in addition to the conventional anode and cathode. This auxiliary electrode is located at the cathode side, as shown in the following figure: Electrodes were deposited by screen printing of commercial powders (Marion Technologies) on YSZ discs (Dynamic Ceramic, 8% mol Y2O3-ZrO2) with diameter of 20 mm and 1.6 mm thickness. The anode electrode was a Ni/GDC film of 40 µm thickness and a surface area of 1.76 cm2 and was sintered at 1250°C for 2 hours. The cathode and the auxiliary electrodes were composed of LSM oxides (La0.65Sr0.35MnO3 - fuel Cell Materials, LSM35) mixed with YSZ (Tosoh). The cathode was a ring shaped electrode at the periphery of 0.93 cm2 surface area, and the auxiliary was a circular dot electrode of 0.31 cm2 surface area at the center of the cathode but separated from the cathode. They were sintered at 1150°C for 2 hours.To study the performances of the bottom cells, we have used a test rig (ProboStat, NorECs, Netherland). The sealing between the anodic and cathodic compartments was ensured by a gold ring which was annealed at 1040°C for 4 days under air. For current collection, Pt meshes were used for cathode and auxiliary while Ti mesh, catalytically inactive,was used for anode. Prior to the experiments, the catalysts were reduced under pure H2 at 900oC for 2 hours. The effect of the addition of H2S in the reaction mixture has been investigated (1 ppm of H2S/He, 2%CH4/He – Air Liquide, 5% H2O added with a thermostated water saturator regulated at 33 °C) under 200cc/min flow while cathode and auxiliary were exposed under synthetic air (Linde 99,995%). The products of the reaction were analyzed by using a Hiden Analytical HPR20 quadripole mass spectrometer.H2S poisoning was followed in open circuit mode, in fuel cell mode and in triode operation mode at 900°C. Triode operation cannot avoid or limit the catalytic degradation of the SOFC cell exposed to 1 ppm H2S but can maintain higher anodic electrochemical performances. This confirms that active sites for catalytic conversion (methane steam reforming) and those for electrochemical oxidation of hydrogen are not the same. The cell performances loss is mainly attributed to the degradation of the catalytic activity, then decreasing the concentration of electroactive species, i.e. hydrogen. Triode operation can slightly compensate the deactivation of the catalytic sites most probably with a local production of H2, from H2O electrolysis. Some specific triode operations can be found to achieve a thermodynamic efficiency close to the unity to avoid any energy overconsumption.Acknowledgements: this work was financed by the EU 7th Framework Program, Fuel Cells and Hydrogen Joint Technology Initiative, under the frame of the T-CELL project (grant agreement 298300).

MICROSCOPIE+ATARI:CARE+ASR:MAO:FCA:PVE; International audience; None

SSCI-VIDE+CARE+ABO:NCA:BDA:PVE; International audience; None

International @ CARE+BRM:BDA:ABO:NCA:PVE; International audience; Les émissions des véhicules à moteur thermique sont réglementées par des normes édictées par des états ou groupements d'états. En Europe, toutes les voitures diesel produites à partir de 2011 ont été équipées d'un filtre à particules (FAP), pour respecter la norme Euro 5 puis l’actuelle norme Euro 6 (nombre limite d’émission de particules de diamètre supérieur à 23 nm, PN = 6,0 × 10^11 #/km ; masse limite, PM = 4,5 mg / km). Pour les véhicules à injection directe d’essence (IDE) le nombre limite d’émission de particules est de, PN = 6,0 × 10^12 #/km pour une masse limite, PM = 4,5 mg / km (Euro 6b) et ce, jusqu'en 2017. Au-delà, ce nombre sera réduit à PN = 6 × 10^11 #/ km (Euro 6c) pour joindre celui des véhicules diesel. 2017 verra également l'introduction d’un nouveau cycle d’homologation (WLTP), conçu pour être aussi proche que possible des conditions réelles de conduite.La présente étude (Projet CAPPNOR supporté par l’ADEME) vise à acquérir de nouvelles connaissances relatives aux substances à ce jour encore non réglementées (particules ultra fines -Dp < 23 nm-, HAP, NO2…) émises par les véhicules particuliers dans des conditions d'utilisation aussi proches que possible du réelles. Pour ce faire, les émissions de deux voitures à moteur diesel (équipées chacune d’un FAP spécifique) et d’une voiture à moteur IDE ont été caractérisées sur différents point de fonctionnement, cycles de conduite et phases de régénération. La caractérisation a porté sur la masse et le nombre de particules émises, leur répartition granulométrique, leur morphologie, leur nature chimique ainsi que sur les gaz polluants. Un large panel d'instruments a pour cela été implémenté : un système de dilution, des granulométres, un spectromètre de masse à aérosol, un photomètre pour la mesure en masse du noir de carbone et un système de prélèvement sur grille MET pour des analyses par microscopie électronique.Les moteurs diesel équipés d’un FAP émettent des particules principalement lors du démarrage à froid, lors de forte accélération et pendant les phases de régénération du FAP. Typiquement, ces particules sont constituées d'un mélange complexe de suie de carbone et de particules sous forme de gouttelettes contenant des inclusions métalliques (Fe, Ni, Cr, Mn ...). Par ailleurs, de petites particules soufrées sous forme de fines gouttelettes (Dp < 20 nm) ont été identifiées uniquement lors de la régénération du FAP et peuvent ainsi être liées à la post-injection qui commande celle-ci. Les moteurs IDE peuvent quant-à-eux émettre des concentrations significativement élevées de particules de diamètre supérieur à 23 nm (2-20 × 10^14 #/m3). Ces particules sont principalement de la suie de carbone avec une petite quantité de particules métalliques composites

International @ AIR+MTS:FSA:ABO:PVE; International audience; Metal-Support Interactions (MSI) refers to the effect of the support on the catalytic properties of the supported metal. The phenomenon of Electrochemical Promotion of Catalysis (EPOC) deals with the modification of catalytic activity and selectivity of a catalyst film deposited on a solid electrolyte (ionic conductor) via the application of small electrical potentials or currents. Recent studies on metal-supported catalyst on TiO2 or Yttria-Stabilized Zirconia (YSZ) showed that these two phenomena can be associated with the migration of ionic promoting species containing in the support onto the metallic active sites. These species are responsible for the formation of an effective double layer at the metal-gas interface which affects the binding strength of adsorbed reactants and reaction intermediates. This study reports isotopical labelling experiments during propane oxidation on two different catalytic systems: (a) nanodispersed Pt nanoparticles supported either on ionic conductors (YSZ) or on non-conductive ceramics (ZrO2, SiO2) showing high metallic dispersion and area of triple phase boundary (TPB), (b) Pt catalyst-film deposited on a YSZ membrane (electrochemical catalyst) presenting rather low TPB surface .

International @ AIR+MTS:CZA:ABO:PVE; International audience; European standards for Diesel cars restrict the particulate matter emissions by combining a limit number (PN: 6.0×1011 particulates/km) with a limit mass (PM: 4.5 mg/km) as well as durability of after-treatment system. From 2014, PN and PM limits are also introduced for the approval of gasoline-fuelled vehicles. While conventional Port Fuel Injection (PFI) gasoline vehicles can easily comply with these limits, their Direct Injection (GDI) counterparts are found to emit systematically above this threshold by up to 1.5 orders of magnitude [1,2]. The Euro 6b legislations will tolerate a PN limit at 6.0×1012 particulates/km for these GDI vehicles but this standard will be strengthened from 2017 (Euro 6c) to reach the level of Diesel cars. It is therefore expected that GDI vehicles may require the installation of Gasoline Particulate Filters (GPF). At the same time, the penetration of GDI vehicles is expected to rapidly grow in the near future in both the European and the US markets. This is due to their improved fuel efficiency compared to the conventional PFIs as well as their ability to be implemented in hydride cars. Therefore, it is of strong interest to develop catalysts for the regeneration of GPF. Comparing to Diesel ones, GDI exhausts contain much lower amounts of oxygen. The scientific issue consists in the development of catalysts effective for soot oxidation at low oxygen levels. For cost and sustainability reasons, it is also necessary to avoid the utilization of noble metals. This study examines the use of Ag-modified manganites and ferrites as soot oxidation catalysts for GPF.

International @ AIR+MAO:TEP:MTS:ASR:PVE; International audience; Investigations of soot combustion on Yttria-Stabilized Zirconia by Environmental Transmission Electron Microscopy (ETEM) M. Aouine1, T. Epicier1,2, E. Obeid1, M. Tsampas1, A. Serve1, K. Pajot3, P. Vernoux1* 1Université de Lyon, Institut de Recherches sur la Catalyse et l’Environnement de Lyon, UMR 5256, CNRS, Université C. Bernard Lyon 1, 2 avenue A. Einstein, 69626 Villeurbanne, France 2Université de Lyon, MATEIS, UMR 5510, CNRS, INSA de Lyon, 69621 Villeurbanne Cedex, France 3PSA PEUGEOT CITROËN, Centre technique de Vélizy, Route de Gisy 78943 Vélizy-Villacoublay, France *corresponding author:philippe.vernoux@ircelyon.univ-lyon1.fr Introduction Diesel Particulate Filters (DPFs) equip all Diesel light vehicles in Europe to remove toxic Particulate Matter (PM). They present high filtering efficiency (>99%) but must be periodically regenerated due to soot particles accumulation. In addition, from 2014, EURO 6 standards require the utilization of a NOx catalytic after-treatment device [1], preferentially placed between the Diesel Oxidation Catalyst (DOC) and the DPF [1]. Therefore, NO2 cannot anymore be utilized as an oxidant for soot combustion. This makes crucial the development of effective and durable catalysts for soot combustion with oxygen. We have recently reported that Yttria-stabilized Zirconia (YSZ), a pure oxygen ion ceramic conductor without any redox property, can continuously oxidize soot with oxygen in Diesel exhaust conditions [2]. It was proposed that the ignition of the soot oxidation on YSZ involves a fuel-cell-type electrochemical mechanism at the nanometric scale. Electrochemical oxidation of the soot could occur at the soot/YSZ interface while oxygen electrochemical reaction takes place at the triple phase boundary (tpb) soot/gas/YSZ. To get further insights of this mechanism, Environmental Transmission Electron Microscopy (ETEM) was used to in-situ follow the soot combustion at the interface with YSZ. Materials and Methods In situ, environmental experiments were performed in the Ly-EtTEM microscope, a last generation ETEM (TITAN 80-300 kV from FEITM) equipped with an aberration corrector. Pure oxygen was introduced owing to the high precision leaking valves at low pressure, up to typically 3 mbar. Samples prepared as a mixture of soot and YSZ particles (as described below) were deposited on titania grids with and without supporting film. These grids were subsequently mounted on a GatanTM heating stage in inconel; the temperature was raised up to typically 550°C. The microscope was operated at 80 and 300 kV. Soot was obtained from a mini Combustion Aerosol Standard (miniCAST, Jing Ltd. Switzerland) soot generator. The soot particles were produced with a mini-CAST burner from a propane/air flame. This mini-CAST soot shows an EC (Elemental Carbon) /TC (Total Carbon) ratio of ~0.95, closed to that reported in the literature for real Diesel soots [3]. Yttria-stabilized Zirconia (YSZ) powder, containing 8 mole % of Yttria from TOSOH, (ZrO2)0.92(Y2O3)0.08, was used as purchased. Collected soot and YSZ powder were mixed with a weight ratio of 1:4 and crushed for 20 minutes in a mortar in order to improve the soot/YSZ agglomerate contact, conventionally denoted as tight contact mode. Significance These in-situ ‘ETEM’ observations confirm that bulk YSZ oxygens are the active species for soot oxidation at the soot/YSZ interface. Acknowledgements We acknowledge the CLYM (Centre Lyonnais de Microscopie, www.clym.fr) for its guidance in the Ly-EtTEM project which was financially supported by the CNRS, the Région Rhône-Alpes, the ‘GrandLyon’ and the French Ministry of Research and Higher Education. The authors are grateful to the ANR (Agence National de la Recherche) for funding “PIREP2” project (N° ANR-2010-VPTT 006-01) and ADEME (Agence de l’Environnement et de la Maîtrise de l’Energie) for the PhD grants of E. Obeid and A. Serve. References 1B.A.A.L. van Setten, M. Makkee, J.A. Moulijn, Catalysis Reviews 2001, 43 (4), 489. 2.E. Obeid, L. Lizarraga, M.N. Tsampas, A. Cordier, A. Boréave, M.C. Steil, P. Vernoux, Journal of Catalysis 2014, 309, 87. 3.T. Ferge, E. Karg, A. Schroppel, K.R. Coffee, H.J. Tobias, M. Frank, E.E Gard, R. Zimmermann, Environmental Science & Technology 2006, 40 (10), 3327.

International @ AIR+BRM:ABO:BDA:PVE:NCA:MTS:AMM; International audience; Epidemiological studies have linked exposure to particles matter less than 2.5 microns in diameter (PM2.5) with adverse health effects as cardiovascular or pulmonary diseases that cause premature death. The contribution of the transportation sector to the average total emission of PM2.5 in the ambient air is 1 2% [1]. This latter value is likely higher in areas near emission sources (i.e. urban area). Since 2011, all Diesel cars are equipped with a Diesel Particulate Filter (DPF) and respect European standards (Euro 6) for particulate matter emissions which combine a limit number (PN: 6.0×10^11 particulates/km) with a limit mass (PM: 4.5 mg/km). For gasoline direct injection (GDI) light vehicles, there is a limit number of 6.0×10^12part/km (Euro 6b) until 2017. Beyond, PN will be limited to 6×10^11 part/km (Euro6c) as Diesel vehicles with the introduction of the WLTC cycle, designed to be as close as possible to the real driving conditions. In this study, which is part of CAPPNOR project (supported by ADEME), we used a new particle collection technique, a MSP (Mini - Particles Sampler) [2], based on filtration through one class of TEM dedicated supports, namely TEM porous grids,to directly collect and characterize particles emitted from Euro5 vehicles: two Diesel vehicles equipped with two DPF technologies (a DPF regenerated with a Fuel Borne Catalyst (FBC) and a Catalytic Diesel Particulate Filter (CDPF)) and one Gasoline Direct Injection (GDI) vehicle. Collections were carried out during various engine operations and three driving cycles (NEDC, WLTP and ARTEMIS). Characterizations were performed with TEM coupled with EDX analysis and were focused on the physical size distribution, the morphology, the mass and the chemical compositions of particles emitted during cold and hot start and also during DPF regenerations for Diesel vehicles. Diesel engines equipped with DPF mainly emit particles during cold start and DPF regenerations. During cold start particles emitted are mainly carbon soot. During the DPF regenerations, PM size distributions are classified as bimodal, mainly consisting of the nucleation and accumulation modes. Typically, these particles are composed of a complex mixture of soot and droplet like particles. The increase of engine speeds during cycles resulted in increase of fractions of metal contents (Ni, Fe, Cr, Mn...) in particulate matters. GDI engines can emit significantly high PN concentration, mainly carbon soot, depending on the engine operating conditions. GDI will need additional improvements to reach the threshold of Euro 6c, whether by engine calibration and/or by implementing a particulate filter.

International @ AIR+PVE; International audience; Electrochemical gas sensors are particularly suitable for the on-board diagnostic of the car exhaust after treatment efficiency. The catalytic properties of the sensitive electrodes are involved in the detection mechanism of gaseous pollutants such as NOx, CO and hydrocarbons. In addition, a catalytic filter deposited on the surface of these electrodes can strongly improve both the selectivity and the sensitivity of the sensor. On the other hand, electrochemical gas sensors can also be used to monitor the catalytic activity of a process.

National @ AIR+ABO:BRM:NCA:LRE:BDA:PVE; International audience; None

International @ AIR+ABO:LRE:PVE:MTS; International audience; Solid oxide fuel cells have the flexibility, due to their high operating temperature, to use natural gas directly as the fuel in the anodic compartment. A typical problem in this process is the significant degradation in cell voltage and in the catalytic direct internal reforming activity due to H2S poisoning, which is present in natural gas [1]. The aim of this study is to enhance the sulphur tolerance of SOFCs operated under 2%CH4-5%H2O in presence of 1-10 ppm H2S at 800-900oC. The first aim of this study is the development of novel modified Ni/GDC anodes with improved sulphur tolerance during catalytic CH4 reforming. The second approach entails the use of triode operation in order to enhance the SOFC performance.