New Preparation of PdNi/C and PdAg/C Nanocatalysts for Glycerol Electrooxidation in Alkaline Medium

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Palladium Electrocatalysts Synthesis: Probing Reducing Agent Effect By XRD, XPS and ORR

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Electrochemical activity of ruthenium and iridium based catalysts for oxygen evolution reaction

International audiencedecomposition process. The suitable heat treatment of the polymeric precursors allowed to recover metal oxides free from organic carbon, which can be oxidized to carbon dioxide during H2O splitting at elevated potentials. The materials were examined by various physicochemical techniques in order to understand their electrochemical behavior as anodes in a 5 cm(2) single proton exchange membrane water electrolyzer. Although the presence of Ir in the electrocatalyst composition contributes undoubtedly to its stability against ruthenium dissolution and the Faradaic efficiency of the PEM electrolysis cell, its great amount increases the overpotential value. The activity of the home made RuxIr1-xO2 anodes towards the oxygen evolution reaction occurs at ca. 1.5 Vat 25 degrees C

Kinetic study of oxygen reduction reaction on carbon-supported Pd-based nanomaterials in alkaline medium

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Structural and Phase Transitions in the High Composition Domain of the System (1-x)Pb(Mg1/3Nb2/3)O3—xPbTiO3

International audienceRaman scattering, dielectric studies, powder and single crystal X-ray diffraction on 0.6Pb(Mg1/3Nb2/3)O3-0.4PbTiO3 (PMN-40PT) and 0.55Pb(Mg1/3Nb2/3)O3-0.45PbTiO3 (PMN-45PT) were carried out over a wide temperature range. Dielectric plots of PMN-45PT revealed two phase transitions with a sharp maximum at TC (paraelectric-ferroelectric transition at 485 K, from cubic to tetragonal with respective space groups Pm-3m and P4mm similar to PMN-40PT) and a second broad Raman shift at around 225 K. The Raman investigations confirmed the existence of phase transitions in PMN-45PT crystals, and the lowest frequency behaves like a soft mode. The appearance of diffuse scattering at room temperature in PMN-45PT suggests a phase distinct from PMN-40PT below TC. The identification of the symmetry in this temperature region will be further demonstrated

Silica fume as porogent agent in geo-materials at low temperature

International audienceThe synthesis of geopolymers based on alkaline polysialate was achieved at low temperature (∼25-80 °C) by the alkaline activation of raw minerals and silica fume. The materials were prepared from a solution containing dehydroxylated kaolinite and alkaline hydroxide pellets dissolved in potassium silicate. Then the mixture was transferred to a polyethylene mold sealed with a top and placed in an oven at 70 °C for 24 h. For all geopolymer materials, following dissolution of the raw materials, a polycondensation reaction was used to form the amorphous solid, which was studied by FTIR-ATR spectroscopy. The in situ inorganic foam based on silica fume was synthesized from the in situ gaseous production of dihydrogen due to oxidation of free silicon (content in the silica fume) by water in alkaline medium, which was confirmed via TGA-MS experiments. This foam has potential as an insulating material for applications in building materials since the thermal measurement has a value of 0.22 W m−1 K−1

Complete oxidation of formaldehyde at room temperature using TiO 2 supported metallic pd nanoparticles

A series of reduced and oxidized Pd/TiO 2 catalysts were prepared and used for catalytic oxidation of formaldehyde (HCHO) at room temperature. The reduced catalysts were much more active than the oxidized ones. Nearly 100% HCHO conversion was achieved over the former while it was less than 18% over the latter. Sodium borohydride (NaBH 4) reduced Pd/TiO 2 catalysts exhibited very high turnover frequencies of HCHO oxidation and kept highly active in the presence of chloride. Strong metal-support interaction, well-dispersed and negatively charged metallic Pd nanoparticles, and rich chemisorbed oxygen are probably responsible for the high catalytic activities over the former. Metallic Pd nanoparticles with a strong capacity for oxygen activation should be the active sites for catalytic oxidation of HCHO. © 2011 American Chemical Society.link_to_subscribed_fulltex