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International audience; In the present study, Au-V2O5 sensing material was tested as a sensing electrode for developing mixed-potential ammonia gas sensors. The results of gas sensing measurements indicated selective responses to NH3 while this selectivity was highly dependent on the temperature. Different V2O5 contents were tested in the sensing electrode. The results showed that by increasing V2O5 content from 15 wt.% to 50 wt.%, selective ammonia sensors could be achieved at 550 °C. The selectivity of Au-50%V2O5 sensor was also confirmed in gas mixtures of CO, NH3, NO, and NO2 gases. Modeling of the sensor responses in the ammonia concentration range 2-40 ppm at four oxygen concentrations was performed based on mixed-potential theory. Nernst and Butler-Volmer equations with an electron transfer assumption were used for data modeling.

International audience; In recent years, printed and flexible gas sensors have quickly emerged as an innovative area of great interest because of their lightness and low cost. These flexible sensors can be easily integrated into autonomous systems for many applications such as smart food packaging and premature disease detection. In this paper, a novel approach was applied to manufacture a fully inkjet-printed gas sensor on a flexible polymeric foil. Platinum heater and gold electrodes were printed on the top side of the substrate, separated by a thin insulating layer of printed polyimide. An aqueous sol-gel process was adopted to synthesize nanosized SnO2-based sol that guaranty a crystallization at 350 °C, which is entirely consistent with the polyimide foil. Then, the sol was transformed into a stable ink and inkjet printed over the gold electrodes. The printability of different inks was optimized to ensure flawless ejection of droplets, and the complex physico-chemical interactions between the inks and different interfaces were controlled to get well-defined patterns with high resolution. Finally, electrical measurements of the printed sensor were performed to characterize the response and the sensitivity to different concentrations of ethanol, ammonia and carbon monoxide gases, at working temperature of 300 °C, in dry and wet air.

International audience; In this contribution brownmillerite-based nanocomposite cathode for Single-Chamber Solid Oxide Fuel Cells is developed. These cells can be very attractive especially for small and cheap devices because of the absence of seals. The efficiency of SC-SOFCs is strictly connected to the selectivity of anode and cathode, the bottleneck for this technology. The development of a cathode inert in fuel oxidation is particularly challenging. Our strategy is to start from a catalytically un-active support (CFA = Ca2FeAl0.95Mg0.05O5) and induce the formation of iron oxide based nanoparticles, expected to activate oxygen. Symmetric (CFA + FeOx/CGO/CFA + FeOx) and complete cells (CFA + FeOx/CGO/Ni-CGO) are studied in air and methane/oxygen 2:1 mixture. The Area Specific Resistance of CFA + FeOx is less than 1/3 that of CFA. The high selectivity allows to reach an efficiency of 25%; power still needs to be increased but we demonstrated the possibility to develop selective low cost electrodes. The effect of air, methane/oxygen exposure and the heat treatments were carefully investigated.

This study reports the catalytic properties of Ag nanoparticles dispersed on mixed ionic and electronic conducting layers of LSCF (La0.6Sr0.4Co0.2Fe0.8O3) for propene combustion. A commercial and a synthesized LSCF powder were deposited by screen-printing or spin-coating on dense yttria-stabilized zirconia (YSZ) substrates, an oxygen ion conductor. Equal loadings (50 &micro, g) of Ag nanoparticles were dispersed via drop-casting on the LSCF layers. Electrochemical and catalytic properties have been investigated up to 300 &deg, C with and without Ag in a propene/oxygen feed. The Ag nanoparticles do not influence the electrochemical reduction of oxygen, suggesting that the rate-determining step is the charge transfer at the triple phase boundaries YSZ/LSCF/gas. The anodic electrochemical performances correlate well with the catalytic activity for propene oxidation. This suggests that the diffusion of promoting oxygen ions from YSZ via LSCF grains can take place toward Ag nanoparticles and promote their catalytic activity. The best specific catalytic activity, achieved for a LSCF catalytic layer prepared by screen-printing from the commercial powder, is 800 times higher than that of a pure Ag screen-printed film.

One of the most effective technologies in decreasing large-scale NOx emission produced by diesel engine vehicles is Urea-SCR (selective catalytic reduction) system. In order to prevent inducing excessive ammonia to the environment, an NH3 sensor is required at the exit of this system [1, 2]. In this study, highly selective ammonia sensors were developed to detect ammonia emissions from automotive exhaust. The sensors were fabricated with 8-YSZ electrolyte, a platinum reference electrode and a working electrode of Au-V2O5 (mass ratio 85/15), screen-printed on an alumina substrate. A platinum resistor was printed at the backside of the support to control the sensor temperature. The measured sensor’ response (ΔV) is the potential difference between reference and working electrodes. Figure 1 shows the responses of two identical sensors to 100 ppm CO, NO2, NO and 20 ppm of NH3 at four different temperatures. It can be seen that the sensors respond to all gases at lower temperatures while by increasing temperature to 600°C, the selectivity to NH3 is greatly improved. The selectivity of sensors was also confirmed by testing other possible interfering gases: no responses were observed for 20ppm of hydrogen and 100ppm of a hydrocarbon mixture. The stability of such sensors was studied at 550°C and 600°C. Since the sensors show no long-term stability at 600°C (electrode degradation), but remain stable at 550 °C, investigations were made to decrease the working temperature while maintaining selectivity. After testing different mass percentages of V2O5 in working electrode, we observed that by increasing this value to 50%, the working temperature of selective ammonia sensors could be decreased to 550°C with stable responses. Further investigations will be performed in order to gain deeper insight in sensing mechanism of V2O5 based working electrodes, which governs the sensor’s performance. References [1] K. Shimizu, I. Chinzei, et al. "Doped-vanadium oxides as sensing materials for high temperature operative selective ammonia gas sensors," Sensors and Actuators B, 141, 2009, pp. 410-416. [2] M. Van Nieuwstadt, I. Dpadhyay, et al. "Control of Urea SCR Systems for US Diesel Applications" in IFP Energies Nouvelles International Conference, Dearborn, USA, 2011, pp. 655-665. Figure 1

International audience; Laser induced densification of ceramic oxide has shown great promises. However to control this process in regards of the final properties of the material, it is necessary to understand phenomena occurring during laser matter interaction, especially heat diffusion through the material. A thermal simulation of cerium gadolinium oxide (CGO) submitted to infrared laser pulses is presented. In order to determine the temperature profile during laser treatment, optical properties of CGO must be known; for this purpose, ellipsometry measurements were performed in order to obtain absorption coefficient and reflectivity. Finally, a thermal model based on heat equation was developed. Experimental observations of irradiated CGO surfaces were in agreement with the simulation results, in particular at maximum temperature when the material reaches fusion.

Catalytic and electrocatalytic tests have been carried out in a solid oxide cell for propylene combustion using two different Ag screen-printed films deposited on yttria-stabilized zirconia. Competitive adsorption between oxygen and propylene has been observed at 300 °C. Catalytic performances can be tailored by current application in a non-Faradaic manner. The predominant impact of current applications is to modify the reactivity of oxygen present on the Ag surface. Positive current applications enhance the propylene conversion by producing more reactive oxygen species. This beneficial effect is more pronounced under lean-burn conditions where the oxygen coverage on Ag is high.

International audience; Ethylene oxide (EO) is industrially produced by epoxidation of ethylene on Ag-based heterogeneous catalysts. Electrophilic oxygen species are assumed to be active key species in the EO production. This study explores the possibility to electrochemically produced these oxygen species in a solid oxide electrochemical cell. Two series of Ag based cermet electrodes were prepared either with Yttria Stabilized Zirconia (YSZ), a pure oxygen ionic conductor, or with Gadolinia-Doped Ceria (GDC), a mixed ionic and electronic conductor. Ag/YSZ cermet layers were deposited on planar and tubular YSZ dense substrates by using a conventional chemical method while Ag/GDC cermets were coated on GDC dense pellets by reactive magnetron sputtering. We evidenced a self-redispersion of Ag in the ethylene/oxygen mixture in Ag/YSZ cermet layers leading to the formation of small Ag clusters in close interaction with YSZ which are selective for epoxidation. However, the sintering process of these small Ag clusters is too fast even at 260°C to maintain the EO selectivity. On the other hand, the selectivity towards EO and the ethylene conversion of Ag/GDC cermet coatings were found to linearly increase with the applied current, demonstrating for the first time, the direct electrooxidation of ethylene into EO.

In this study, we have investigated, for the very first time, the oxygen electrode reactions on Ag/YSZ electrochemical catalysts both in oxygen and under reaction conditions compatible with the ethylene epoxidation reaction. Electrochemical Impedance Spectroscopy (EIS) in combination with in-situ Raman spectroscopy and catalytic activity measurements were used to identify and understand the main oxygen reaction pathways. The results obtained suggested that the rate limiting step under an O2 reaction atmosphere (at 300 °C) is the O2 adsorption/dissociation process on the Ag catalyst-electrode. In addition, the polarization resistance increased with time under the presence of O2. This was attributed to the formation of Ag2O on the catalyst surface or near surface, which limits the oxygen electrode reactions. Finally, we observed that the addition of ethylene in the feed stream hinders the electrode reaction, due to its competitive chemisorption with oxygen on Ag. These results give new insights into the design of selective Ag/YSZ catalyst for ethylene epoxidation. Keywords: Electrochemical Impedance Spectroscopy (EIS), Oxygen electrode reaction, Ag/YSZ, Ethylene epoxidation

ISSN: 2504-3900; International audience; The development of selective and cheap metal oxide gas sensor at ambient temperature is still a challenging idea. In this study, SnO2 surface functionalization was performed in order to obtain sensitive and selective gas sensor operated at ambient temperature. 3-aminopropyltriethoxysilane (APTES) was used as an intermediate step, followed by functionalization with molecules having acyl chloride with different end functional groups molecules such as alkyl, acid and ester groups. Acid and ester modified sensors are sensitive to ammonia between 0.2 and 10 ppm at room temperature. However, ester modified SnO2 is more selective than acid modified sensor regarding ethanol and carbon monoxide gases.

ISSN: 2504-3900; International audience; Sol based SnO2 precursor was synthetized by aqueous sol-gel route, then transformed into a stable ink with appropriate viscosity and surface tension to be inkjet printed and sintered at relatively moderate temperature. Plastic foil with thickness of 50 µm was selected as substrate for its high thermal resistance and stability (Upilex-50S). Prepared sol and formulated ink were both characterized by analytical techniques; electrical measurements were performed on the printed sensing film to characterize the response to CO gas in different concentrations, at working temperature of 300°C.

International audience; In single-chamber solid oxide fuel cells (SC-SOFC), anode and cathode are placed in a gas chamber where they are exposed to a fuel/air mixture. Similarly to conventional dual-chamber SOFC, the anode and the cathode are separated by an electrolyte. However, as in the SC-SOFC configuration the electrolyte does not play tightness role between compartments, this one can be a porous layer. Nevertheless, it is necessary to have a diffusion barrier to prevent the transportation of hydrogen produced locally at the anode to the cathode that reduces fuel cell performances. This study aims to obtain directly a diffusion barrier through the surface densification of the electrolyte Ce0.9Gd0.1O1.95 (CGO) by a laser treatment. KrF excimer laser and Yb fiber laser irradiations were used at different fluences and number of pulses to modify the density of the electrolyte coating. Microstructural characterizations confirmed the modifications on the surface of the electrolyte for appropriate experimental conditions showing either grain growth or densified but cracked surfaces. Gas permeation and electrical conductivities of the modified electrolyte were evaluated. Finally SC-SOFC performances were improved for the cells presenting grain growth at the electrolyte surface.

Catalytic and electrocatalytic measurements have been carried out in a solid oxide cell for propylene combustion using continuous Ag catalytic films and Ag nanoparticles dispersed on a mixed ionic electronic conductor film deposited on yttria-stabilized zirconia. Similar EPOC behaviors were observed for both samples, indicating that dispersed Ag nanoparticles in LSCF can be electropromoted in a reversible and non-Faradaic manner under lean-burn conditions. Key words: Electrochemical Promotion of Catalysis (EPOC); Propylene Combustion; Ag Catalytic films; dispersed Ag nanoparticles. Introduction: Catalytic combustion as a process used for removal of hydrocarbons from automotive gas exhausts or for energy production has been widely implemented on supported PGM (Platinum Group Metals) based catalysts. Since PGMs are very costly and rare, there is a strong need for an equally effective and less expensive catalyst. The electrochemical promotion of catalysis (EPOC), is a promising concept to in-operando boost catalytic processes in a reversible and controlled manner. The aim of this study was to develop Ag-based electrochemical catalysts for low temperature propylene deep oxidation. The magnitude of the electrochemical promotion has been investigated on continuous screen-printed Ag films as well as on Ag nanoparticles dispersed into the porosity of LSFC (La0.8Sr0.2Co0.2Fe0.8O3), a mixed ionic electronic conductor (MIEC). Experimental: Nanostructured electrochemical catalysts were prepared by screen-printing and by wet impregnation method. Catalytic and electrocatalytic tests have been carried out in a specific quartz reactor1 which operated under continuous flowing conditions at atmospheric pressure. The catalytic activity was monitored in a temperature range of 100 to 400 oC under lean-burn conditions, as encountered in Diesel exhausts. The most active Ag films were also evaluated under closed circuit conditions in order to measure the impact of polarization between the silver working electrode and a Au reference electrode. Both electrodes were exposed to the same atmosphere in a single chamber configuration. Results and discussion: Figure 1 shows typical catalytic activity measurements under current application for a Ag/YSZ sample (a) and a Ag/LSCF/YSZ sample (b) under lean-burn conditions, at 300 oC. The OCV propylene conversion is twice on the dispersed Ag nanoparticles despite a two orders of magnitude lower Ag loading. Furthermore, similar EPOC behaviors were observed for both samples, indicating that dispersed Ag nanoparticles in LSCF can be electropromoted in a reversible and non-Faradaic manner. The predominant impact of current applications is to modify the reactivity of oxygen present on the Ag surface. Conclusions: This study reports, for the first time, that the catalytic activity for propylene combustion of Ag coatings and Ag nanoparticles supported on LSCF both deposited onto YSZ can be tailored by current applications in a non-Faradaic manner. This study also demonstrates that EPOC can enhance catalytic properties of Ag nanoparticles dispersed in a MIEC layer for the abatement of propylene in air. Acknowledgments: This study was performed in the “EPOX” project, funded by the French National Research Agency (ANR), ANR-2015-CE07-0026. References [1] I. Kalaitzidou, T. Cavoue, A. Boreave, L. Burel, F. Gaillard, L. Retailleau-Mevel, E.A. Baranova, M. Rieu, J.P. Viricelle, D. Horwat, P. Vernoux, Cat. Com., 104 (2018) 28-31. Figure 1

International audience; Mixed potential ammonia gas sensors were fabricated by using two sensing materials of Ni3V2O8 and Au-V2O5 as working electrodes, YSZ as electrolyte and platinum as reference electrode. The results have shown that the Ni3V2O8 sensors show cross-sensitivity toward NO gas. However, Au-V2O5 working electrodes displayed a high sensitivity to NH3 as well as very fast response and recovery times at high temperatures. Furthermore, the results indicate that the selectivity of Au-V2O5sensors increases by increasing temperature.

International audience; In this work, a flexible tin oxide (SnO2) gas sensor was successfully fabricated by inkjet printing technology. This thin film deposition technique requires the formulation of stable suspensions with specific fluidic properties. Aqueous Sol-gel method was applied to synthesize astable sol based on tin oxide, then transformed into ink with the appropriate viscosity and surface tension to be printed using a drop-on-demand piezoelectric inkjet printer. Thermal analyses of synthetized sol show that a crystallized structure of SnO2 could be obtained at 350 °C, which is lower than crystallization temperatures of SnO2 previously reported in the literature, and entirely consistent with our plastic substrate. The printed thin-film was then sintered at 350 °C on polyimide foil (Upilex-50S) and characterized as sensor.

International audience; The fabrication of printed electronic devices based on metal oxide inks requires the formulation of stable suspensions with specific fluidic properties. In our work, a tin oxide based solution was synthesized by aqueous sol–gel method and transformed into an ink with appropriate viscosity and surface tension to be inkjet-printed on polyimide foil and sintered at relatively low temperature. Thermal analysis by TGA/DSC and microstructural analysis by XRD of synthesized sol show that a crystallized structure of SnO2 could be obtained at 350 °C, which is lower than crystallization temperatures of SnO2 previously reported in the literature, and entirely consistent with the use of polyimide foil. The stability and the rheological properties of the ink were studied to ensure the jettability criteria of the inkjet printer. Electrical measurements of the printed sensing films were performed to characterize the response to CO gas in different concentrations, at working temperature of 300 °C.

International audience; In order to deal with the well-known lack of selectivity of SnO2 based gas sensors, the functionalization of SnO2 was performed. Liquid silanization by 3-aminopropyltriethoxysilane (APTES) was used as an intermediate step, followed by functionalization with molecules bearing acyl chloride with alkyl or ester end functional groups. Modified sensors with APTES, alkyl and ester end functional groups were successfully characterized by Attenuated Total Reflectance-Fourier Transform Infrared spectroscopy (ATR-FTIR). No response was observed for APTES and alkyl modified SnO2 sensors to ammonia gas at room temperature while the SnO2 sensor modified with ester end group was found to be sensitive and selective to ammonia gas at room temperature. This implies that the response is generated by ester functional groups. Working at low temperature is also one of the advantages of these sensors as well as the selectivity with respect to other gases like acetone and ethanol.

International audience; Solid Oxide Fuel Cells (SOFCs) are electrochemical devices capable of converting and storing energy in a sustainable and efficient way. The decrease of the operating temperature could be of great help for their diffusion. The use of nanocomposites is a smooth way to design materials with many advanced functionalities that could not be reached at the same time with only a single component. Two LSGF (La0.6Sr0.4Ga0.3Fe0.7O3) nanocomposites have been synthesized by wet impregnating manganese and iron oxides (MOx+LSGF, with M = Fe/Mn). The composites’ powders have been extensively characterized by means of XRD, XPS, N2-asdorption, SEM, EDX, TPR, O2-TPD and the results compared with those obtained for LSGF. The supporting perovskite stabilizes the lower oxidation states of Mn and Fe and a deep interaction between the deposited oxides and the perovskite surface is evident. Both Mn and Fe diffuse inside the perovskite during thermal treatments and this phenomenum greatly affect oxygen vacancies, mobility, and exchange capability. The catalytic activity for methane oxidation is affected by nanocomposition. Focusing on the IT-SOFCs, two symmetric cells of the type MOx+LSGF/CGO/LSGF+MOx have been prepared starting from the nanocomposites’ powder. The effect of the SOFCs preparation conditions (temperature, atmosphere) on the electrode and on the cell has been assessed and compared, also through in-situ high temperature XRD, simulating, on the electrodes’ powder, the same treatment necessary to prepare the cell. The use of nanocomposites powders as starting point for electrodes allows to deeply modify the electrochemical performance. A thin, Sr/Fe-rich foil forms on the surface of the electrode during SOFC thermal and deeply improves the electrochemical behaviour of the FeOx+LSGF cathode. The electrochemical results are encouraging for future application in SOFCs, as nanocomposite has an ASR reduced by ⅓ compared to LSGF to 2.1 &#937·cm2 at 620°C.

This paper presents the design and implementation of a foil gas preconcentrator (FGP) on polyimide (PI) substrate. One novelty of the paper is that our device is made on flexible foil by using printing whereas all preconcentrators seen in literature are mainly based on rigid substrates and are micro-machined using cleanroom processes. Printing allows the additive and localized deposition of materials at low temperature on large area and can be applied to both the patterning of the heating element and the integration of the gas absorbent material. The benefits are the easy and flexible processing of cost-effective and lightweight preconcentrators for a variety of target gases. The tubular shape of the FGP is obtained by rolling up and sealing the inkjet printed gold hotplate on foil, which is then filled with the gas absorbent material (Carbopack B and Tenax). The diameter of the inlet/outlet of FGP is adjustable leading to high flow rates, up to 1.5 L/min, much larger than their silicon counterpart. The concept was validated using two target gases (Benzene and Acetophenone) at concentrations down to 250 ppb. © 2015 The Authors. Published by Elsevier Ltd.

International audience; The feasibility of room temperature ammonia gas sensors based on tin dioxide (SnO2) functionalization has been demonstrated. 3-aminopropyltriethoxysilane (APTES) was used as an intermediate step, followed by functionalization with molecules having acyl chloride with different end functional groups molecules such as alkyl, acid and ester groups. Modified films were characterized by attenuated total reflectance infra-red spectroscopy (ATR-FTIR). Upon exposure to ammonia gas, the electrical conductance of alkyl, acid and ester modified SnO2-APTES increases, whereas other reducing gases such as ethanol, carbon monoxide and acetone show no change in conductance. Furthermore, ester modified SnO2 is more selective than acid modified sensor regarding ethanol and carbon monoxide gases

This study reports the electrochemical properties for NOx reduction of a ceria-based mixed ionic electronic conducting porous electrode promoted by Pt nanoparticles, as efficient catalyst for NO oxidation, and BaO, as sorbent to store NOx. This catalytic layer was deposited by screen-printing on a dense membrane of gadolinia-doped ceria, an O2− ionic conductor. The targeted Ba and Pt loadings were 150 and 5 μg/cm2, respectively. The NOx selective electrochemical reduction was performed between 400 °C and 500 °C with and without oxygen in the feed. Variations of the open-circuit voltage with time were found to be a good sensor of the NOx storage process on the ceria-based catalyst-electrode. However, no N2 production was observed in the presence of O2 phase in spite of nitrates formation.

International audience; Printed electronics, particularly on flexible and textile substrates, raised a strong interest during the past decades. This work presents a good candidate for conductive inks based on a graphene/polymer nanocomposite material that gathers three main benefits that are 1 - neither clogging nor flocculation, 2 - spontaneous film formation around room temperature, 3 - high conductivity. Nanosized Multilayered Graphene (NMG) is produced through a solvent-free procedure, using a grinding process in water. These NMG suspensions are used to elaborate conductive composite materials through physical blending with emulsifier-free latex. The nanocomposite microstructure exhibits a well-defined cellular architecture that highlights the formation of continuous paths of fillers throughout the material. The conductivity behavior of the nanocomposite material was efficiently described using a percolation model: the conductivity can be tuned by changing the NMG content and the latex size. A low percolation threshold (0.1 vol%) was obtained and the electrical conductivity reached 217 S m−1 for 6 vol% NMG. Efficient film forming occurs at room temperature leading to continuous and deformable materials, which is adequate for printing on flexible and textile substrates. The applicability in electronics is demonstrated by the use of the nanocomposite material in replacement of copper wires in a LED setup.

International audience; Anode-supported solid oxide fuel cells consisting of nickel-gadolinium doped ceria (NiO-CGO, 60:40 wt%) anode, gadolinium doped ceria (CGO) electrolyte and lanthanum strontium cobaltite ferrite-gadolinium doped ceria (LSCF-CGO) cathode are developed and operated under single-chamber conditions, utilizing methane/air mixture. The cell performance is optimized regarding the electrolyte microstructure, cathode composition and testing conditions. The performance of the cell improves with the decrease of the thickness of the electrolyte and the increase of the ratio of methane to oxygen. The test cell with LSCF-CGO cathode (70:30 wt%) that was sintered at 1100 °C for 2 h and 150 μm dense electrolyte exhibits the maximum power output of ∼260 mW cm−2 at 600 °C in CH4/O2 = 2 atmosphere.

A solid oxide fuel cell was designed to be operated in pure methane, without external reforming or carrier gas. The fuel cell was built up from conventional NiO-YSZ anode supported cell with a specific Pt screen-printed anodic collecting system and a Ir-CGO catalytic layer. The operation principle is based on Gradual Internal Reforming. After an initiation in H2 for 30 minutes, the cell was operated for almost 2000 hours in pure and dry CH4 with a fuel utilization rate of 30 %. Intrinsic gradual degradation of 15 %/1000 h was observed, but no coking occurred at the anodic side.

International audience; In the present work, SnO2 sensors were produced by thick film fabrication. In order to deal with well-known lack of selectivity of SnO2 sensors, functionalization was performed. Silanization by 3-aminopropyltriethoxysilane (APTES) in liquid phase was used as an intermediate step, followed by functionalization with molecules bearing acyl chloride with different end functional groups molecules, for example ester group. Modified sensors with APTES and ester end functional group were successfully characterized by attenuated total reflectance-Fourier transform infrared spectroscopy (ATR-FTIR). The SnO2 sensor modified with ester end group was found to be sensitive and selective to ammonia gas at 100°C. Working at low temperature is also one of the advantages of these sensors as well as the selectivity with respect to other gases like acetone.

The performance of lanthanum nickelate, La 2 NiO 4 + δ (LNO), as a cathode in IT-SOFCs with the electrolyte cerium gadolinium oxide, Ce 0.9 Gd 0.1 O 2 − δ (CGO), has been investigated by AC impedance spectroscopy of symmetrical cells. A significant reduction in the area specific resistance (ASR) has been achieved with a layered cathode structure consisting of a thin compact LNO layer between the dense electrolyte and porous electrode. This decrease in ASR is believed to be a result of contact at the electrolyte/cathode boundary enhancing the oxygen ion transfer to the electrolyte. An ASR of 1.0 Ω cm 2 at 700 °C was measured in a symmetrical cell with this layered structure, compared to an ASR of 7.4 Ω cm 2 in a cell without the compact layer. In addition, further improvements were observed by enhancing the cell current collection and it is anticipated that a symmetrical cell consisting of a layered structure with adequate current collection would lower these ASR values further.

BaIn0.3Ti0.7O2.85 (BIT07) is a promising electrolyte for solid oxide fuel cells, due to its chemical compatibility with most of the cathode electrode material such as LSM and Ln2NiO4. The present work is aimed on the fabrication of anode-supported half cells with thin BIT07 electrolyte. For this, Ni-8YSZ cermet was chosen due to its excellent mechanical and electrochemical properties, in addition to its low cost. The NiO–8YSZ anode support was prepared by tape casting, and for this, an organic slurry formulation was optimized. The BIT07 electrolyte thin film was deposited through screen printing on the green anode. The formulation of the ink was optimized, and sintering at 1350°C for 3 h led to a dense electrolyte with controlled thickness varying from 2 to 12 μm. Further, the cermet electrode still had a homogeneous microstructure with well-defined anode/electrolyte interface. The electrode ASR was about 0.5 Ω cm2 and was stable over 500 h at 800°C under H2–3% H2O. The fabrications of half cells were successfully scaled up to 100 mm × 100 mm retaining the dimensional control and without any surface defects.

Metallic cell supports have been developed for the new generation of fuel cells. Sol–gel process has been used to prepare anodic coatings on these supports at moderate thermal treatment temperature, in order to keep a good support mechanical behavior and limit metallic corrosion. Indeed, we take advantage of the numerous reaction routes that sol–gel method can offer to first synthesize NiO–YSZ (yttria-stabilized zirconia) homogeneous composites, and then to process films of different thicknesses on metallic supports by dip-coating. In this work, the metallic supports could be either dense or porous. To begin with, duplex microstructured anodes were prepared from both thin and thick layers, directly deposited on dense metallic supports. The interfacial anodic layer, around 100 nm thick, improves adhesion and accommodates stresses between metallic interconnect and active thick anode. Moreover, by dipping the substrate into an optimized slurry containing sol–gel composite powders, films of a few microns thick have been obtained and constituted the active anodic part. A heat treatment at only 800 °C leads to a coherent anodic duplex stacking which is continuous, homogeneous and adherent. Subsequently, thick anodic films have also been deposited on two different porous supports, with both dip-coating process and slurries routes. These thick anodic coatings were characterized after thermal treatment at 800 °C.

Metallic cell supports have been developed for the new generation of fuel cells. A sol—gel process has been used to prepare anodic coatings on these supports at moderate thermal treatment temperature, in order to keep good support mechanical behavior and limit metallic corrosion. Indeed, we take advantage of the numerous reaction routes that the sol—gel method can offer to first synthesize NiO—YSZ (yttria-stabilized zirconia) homogeneous composites, and then to process films of different thicknesses on metallic supports by dip-coating. In this work, the metallic supports could be either dense or porous. To begin with, duplex microstructured anodes were prepared from both thin and thick layers, directly deposited on dense metallic supports. The interfacial anodic layer, around 100 nm thick, improves adhesion and accommodates stresses between the metallic interconnect and active thick anode. Moreover, by dipping the substrate into an optimized slurry containing sol—gel composite powders, films a few microns thick have been obtained, and constitute the active anodic part. A heat treatment at only 800°C leads to a coherent anodic duplex stacking which is continuous, homogeneous and adherent. Subsequently, thick anodic films have also been deposited on two different porous supports, with both the dip-coating process and slurry routes. These thick anodic coatings were characterized after thermal treatment at 800°C.

International audience; We report on the development of a metal oxide (MOx) sensor prepared by inkjet printing technology onto polyimide foil. Gold electrodes and a gold heater were printed on each side of the substrate, respectively. SnO2 based ink was developed by sol-gel method and printed onto the electrodes. A final annealing at 400 °C compatible with the polymeric transducers allows to synthetize the SnO2 film. Electrical measurements were carried out to characterize the response of fully printed sensor under different gases. The device was operated at a temperature between 200 and 300 °C using the integrated heater. The sensor exhibited responses to carbon monoxide and nitrogen dioxide, under dry and wet air.

International audience; In single-chamber solid oxide fuel cells (SC-SOFC), anode and cathode are placed in a gas chamber where they are exposed to a fuel/air mixture. Similarly to conventional dual-chamber SOFC, the anode and the cathode are separated by an electrolyte, but in the SC-SOFC configuration it does not play tightness role between compartments. For this reason, the electrolyte can be made by screen printing, a technique particularly appropriate for preparing thick porous layers. However, it is necessary to have a diffusion barrier to prevent the transportation of hydrogen produced locally at the anode to the cathode that reduces fuel cell performances. This study aims to obtain directly a diffusion barrier through the surface densification of the electrolyte by a laser treatment. The material chosen for the electrolyte was cerium gadolinium oxide Ce0,9Gd0,1O1,95 (CGO) which is deposited by screen printing on a composite anode NiO-CGO. KrF excimer laser and Yb fiber laser irradiations were used to modify the density of the electrolyte coating. Different tests were performed with the variation of energy density and number of pulses. Microstructural characterizations confirm the densification on the surface of the electrolyte for appropriate experimental conditions. The effect of laser treatment on SC-SOFC performances will also be discussed.

National audience

International audience; This project deals with the development and the electrochemical characterization of anode supported single chamber SOFC in a simulated environment of thermal engine exhaust gas. In the present work, a gas mixture representative of exhaust conditions is selected. It is composed of hydrocarbons (HC: propane and propene), oxygen, carbon monoxide, carbon dioxide, hydrogen and water. Only oxygen content is varied leading to different gas mixtures characterized by three ratios R = HC/O2. Concerning the cell components, a cermet made of nickel and an electrolyte material, Ce0.9Gd0.1O1.95 (CGO) is used as anode and two cathode materials, La0.6Sr0.4Co0.2Fe0.8O3−δ (LSCF) and Pr2NiO4+δ (PNO), are evaluated. The prepared cells are investigated in the various gas mixtures for temperatures ranging from 450 °C to 600 °C. Ni-CGO/CGO/LSCF-CGO cell has delivered a maximum power density of 15 mW cm−2 at 500 °C with R = HC/O2 = 0.21, while lower power densities are obtained for the other ratios, R = 0.44 and R = 0.67. Afterwards, LSCF and PNO cathode materials are compared and LSCF is found to deliver the highest power densities. Finally, by improving the electrolyte microstructure, some cells presenting a maximum power density of 25 mW cm−2 at 550 °C are produced. Moreover, up to 17% of initial HC are eliminated in the gas mixture.

International audience; Single Chamber Solid Oxide Fuel Cells (SCFC) show a growing interest and are the concern of more and more papers. In such device, anode and cathode are ex-posed to a gas mixture of fuel (hydrocarbon) and oxidant (air) so that no more sealing with electrolyte is necessary. Their operating principle is based on the different catalytic activities of anode and cathode: Ideally, the anode has to be active for the oxidation of fuel while the cathode should present only a strong electro-activity for oxygen reduction. In this paper, we present the development of an anode supported SCFC device running in air/methane mixture characterized by their volume ratio, Rmix = CH4/O2.

International audience; A novel concept that employs dual chamber SOFC technology with a porous electrolyte, which allows the controlled distribution of gaseous O2 at the anode side, was successfully designed using an all porous structure. The oxidative reforming of hydrocarbon streams can consequently operate in a similar fashion to single chamber SOFCs, but within a safer, better controlled process

International audience; Single chamber anode-supported fuel cells are investigated under several methane-oxygen-nitrogen atmospheres at intermediate temperatures (500°C-700°C). Ce0.9Gd0.1O1.95 (CGO) is chosen as electrolyte and deposited by screen-printing onto NiO-CGO anode pellets. A cathode composed of 70 wt% La0.6Sr0.4Co0.2Fe0.8O3−δ (LSCF) and 30 wt% of CGO is screen-printed onto the electrolyte. Thermogravimetric analyses of anode reduction are performed at 700 °C. Carbon deposition is observed under diluted methane but a successful reduction is obtained after an initialization under diluted methane followed by a final treatment under methane-to-oxygen ratio (Rmix) of 2. Anode-supported fuel cells are investigated regarding the working temperature and Rmix. Two types of cells are prepared with modifications of the electrolyte microstructure. For both cells tested, the Open Circuit Voltage (OCV), the power density and the fuel utilization increase when Rmix and temperature decrease. The electrolytes of both cells have a porous microstructure and the electrolyte of the second cell, with the highest thickness, brings better performances. At 600 °C for Rmix = 0.6, the maximum power density is improved from 60 for the first cell to 160 mW cm−2 for the second cell. Comparing the fuel utilization, it increases from 3% for the first cell to 6% for the second one for the same testing conditions.

International audience; A single chamber solid oxide fuel cell (SC-SOFC) is a device able to produce electricity from a mixture of hydrocarbons and oxidant. An innovative application of this system would be to recover energy from exhaust gas of a thermal engine. This paper presents a study of stability and catalytic behaviour of electrode materials composing the cell in a mixture of hydrocarbons (propane, propene), oxygen, carbon monoxide, carbon dioxide, hydrogen and water corresponding to a composition of exhaust gas. A screening of four cathode materials was done, some well-known materials in literature and leading to highest performances such as La0.6Sr0.4Co0.2Fe0.8O3−δ (LSCF), Sm0.5Sr0.5CoO3−δ and Ba0.5Sr0.5Co0.8Fe0.2O3−δ and a last one Pr2NiO4+δ (PNO) very promising for conventional SOFCs. Anode material was a cermet composed of nickel and Ce0.9Gd0.1O1.95 which was also selected as the electrolyte material. Chemical stability tests and catalytic activity studies in the gas mixture were performed on the raw materials and have led to a first selection among cathodes. Two hydrocarbons/oxygen ratios (R = HC/O2) were investigated for materials tests considering the gas mixture stability at high temperature (600°C): R = 0.21 and 0.44. LSCF and PNO were considered as the most stable cathode materials, besides LSCF demonstrated a lower catalytic activity towards hydrocarbon partial oxidation than PNO especially for the R = 0.44 ratio. As for the anode side, nickel was tested regarding its catalytic activity towards hydrocarbons oxidation. It exhibited catalytic activity towards hydrocarbons partial oxidation, especially for the oxygen-lean ratio (0.44), which gradually decreased while lowering temperature from 620 to 450°C.

The NOx (mainly NO and NO2) pollutions that come from the exhaust of the thermal engines can give rise to a serious threat to the environment and human health. The design of more efficient and stable catalysts to reduce NOx to nitrogen in atmospheres containing excess oxygen (typically, from exhaust gas emitted by diesel and lean-burn gasoline engines) has attracted so much attention in the last years. The two actual technologies are using an additional reducing agent to remove NOx, i.e. Diesel fuel post-injection for the NOx storage reduction process and urea for the selective catalytic reduction. An alternative solution could be the electrochemical reduction of NOx in solid oxide electrolysis cell (SOEC)[1,2]that can save the huge reducing agents storage system. This study reports the electrochemical properties for NOx reduction of a Mixed Ionic Electronic Conducting (MIEC) porous electrode promoted by Pt nanoparticles, as efficient catalyst for oxidation reactions, and BaO, as sorbents to store NOx. Pt and BaO nanoparticles were finely dispersed in the porosity of a MIEC film, based on a composite between LSCF (La0.6Sr0.4Co0.8Fe0.2O3-δ) and GDC (Gd0.2Ce0.8O1.9), which was deposited using screen-printing. This catalytic layer was interfaced on a dense pellet of gadolinium doped ceria (GDC), an O2- ionic conductor. The Ba and Pt loadings were around and 150 and 5 µg/cm², respectively. The catalytic performances, upon positive and negative polarizations, have been measured as a function of temperature in the range 200°C-500°C, partial pressure of oxygen and in the presence of propene in the feed. The NOx electrochemical conversion into N2 was found to be driven by the current (Figure 1) and the catalytic activity of the electrode for NO oxidation. In parallel, electrochemical properties have been carried out by using cyclic voltammetry and electrochemical impedance spectroscopy to investigate the electrocatalytic mechanism. Finally, the Pt and BaO nanoparticles in the LSCF/GDC film were characterized by transmission electronic microscopy. References T.J. Huang, C.Y. Wu, S.H. Hsu, C.C. Wu, Energy Environ. Sci., 4, 4061 (2011). R. M. L. Werchmeister, J. J. Bentzen, K. B. Andersen, and K. Kammer Hansen, J. Electrochem. Soc., 161(10) H663-H669 (2014) Figure 1

Pt nanoparticles were dispersed in the porosity of a LSCF-GDC electrode interfaced on a dense GDC membrane. Small positive polarizations can strongly increase (38%-enhancement) the catalytic performance of Pt nanoparticles for propane deep oxidation at low temperatures with apparent Faradaic efficiency values up to 85. This study clearly demonstrates that the catalytic activity of metallic nanoparticles dispersed in the porosity of a mixed ionic electronic conducting electrode can be strongly electropromoted. Keywords: Electrochemical promotion, NEMCA effect, Pt nanoparticles, LSCF/GDC electrode, Post impregnation

AIR+LLI:MTS:PVE; Pt nanoparticles, in a size range which varies from 3 to 20 nm, were dispersed in the porosity of a 7.5 mu m-thick layer of LSCF-GDC electrode interfaced on a dense GDC membrane. Small positive polarizations (200 mu A / 0.8V - 1.2V) can strongly increase the Pt nanoparticles catalytic performance for propane deep oxidation at low temperatures (267 degrees C-338 degrees 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.