Influence of the Processing Method on the Quality of the Protective Coatings for SOFC Applications

International audienceProtective layers for Solid Oxide Fuel Cells (SOFC) interconnects (IC) were developed. The contacting layers are made of La0.8Sr0.2Mn0.5Co0.5O3 (LSMC) and were prepared by wet powder spraying. In order to avoid IC oxidation and a dramatic increase of ASR, MnCo2O4 spinel protective coatings were processed either by Atmospheric Plasma Spraying (APS) or by a Metal Organic route (MO). The influence of the processing method of these layers on the resistance of their assembly with an IC was investigated on Crofer22APU and F17TNb substrates. The measured ASR is stable after about one hundred hours. Their efficiency in Single Repeated Unit (SRU) configuration was also investigated. The MO process gave the thinnest layer, thereby the lowest resistance. The APS process gives thicker and denser layers, thus preventing completely the chromium diffusion through the cathode, but a slightly higher resistance is observed

Monitoring the degradation of a solid oxide fuel cell stack during 10,000h via electrochemical impedance spectroscopy

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Three dimensionally ordered mesoporous hydroxylated Ni x Co 3−x O 4 spinels for the oxygen evolution reaction: on the hydroxyl-induced surface restructuring effect

International audienceMesoporous nickel cobaltites synthesized using a nanocasting technique show high OER activity after surface modifications induced by potential cycling

Platinum Supported Catalysts: Predictive CO and H 2 Chemisorption by a Statistical Cuboctahedron Cluster Model

International audienceChemisorption of probe molecules such as hydrogen and carbon monoxide on the surface of Pt particles is the most common chemical technique used to estimate the crucial parameters of metal catalysts, namely the dispersion (D), the particle size (d), and the metallic specific surface area (SPt). However, it remains a controversy concerning the stoichiometry of adsorbate per surface metal atom, leading to an inaccurate estimation of D, d, and SPt. A model describing the statistics of the surface atoms and sites on perfect cuboctahedron clusters was developed to assess values of D, d, and SPt, assuming the most favorable adsorption sites based on density functional theory (DFT) calculation of the literature. This model successfully predicted the experimental values of D, d, and SPt determined from H or CO chemisorption data, and it allowed providing a set of simple equations for the accurate determination of these parameters from chemisorption experiments on Pt

Co3O4/rGO Catalysts for Oxygen Electrocatalysis: On the Role of the Oxide/Carbon Interaction

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Electrochemically induced surface modifications of mesoporous spinels (Co3O4-d, MnCo2O4-d, NiCo2O4-d) as the origin of the OER activity and stability in alkaline medium

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Estimating linear functionals of a sparse family of Poisson means

Assume that we observe a sample of size n composed of p-dimensional signals, each signal having independent entries drawn from a scaled Poisson distribution with an unknown intensity. We are interested in estimating the sum of the n unknown intensity vectors, under the assumption that most of them coincide with a given 'background' signal. The number s of p-dimensional signals different from the background signal plays the role of sparsity and the goal is to leverage this sparsity assumption in order to improve the quality of estimation as compared to the naive estimator that computes the sum of the observed signals. We first introduce the group hard thresholding estimator and analyze its mean squared error measured by the squared Euclidean norm. We establish a nonasymptotic upper bound showing that the risk is at most of the order of {\sigma}^2(sp + s^2sqrt(p)) log^3/2(np). We then establish lower bounds on the minimax risk over a properly defined class of collections of s-sparse signals. These lower bounds match with the upper bound, up to logarithmic terms, when the dimension p is fixed or of larger order than s^2. In the case where the dimension p increases but remains of smaller order than s^2, our results show a gap between the lower and the upper bounds, which can be up to order sqrt(p)