The X‐ray photoelectron spectra of Ir, IrO2 and IrCl3 revisited

The X-ray photoelectron spectra of metallic iridium and the technologically important iridium compounds, IrO2 and IrCl3, have been studied. The results not only improve the accuracy of published data but also expand the binding energy database of other iridium core-levels. The difference between anhydrous and hydrated materials is explored, and the effect on curve-fitting is discussed, together with the derivation of suitable line shapes for peak fitting of data acquired from a conventional monochromatic Al Kα X-ray source. Copyright © 2017 John Wiley & Sons, Ltd

Synthesis and characterization of electrocatalytic materials : anodic activation of oxygen evolution reaction in a PEM electrolyzer

Le dihydrogène se présente comme un vecteur énergétique d'avenir pour la diversification des sources de production d'énergie. L'électrolyse de l'eau dans le système PEMWE (Proton Exchange Membrane Water Electrolyzer) permet l'obtention de dihydrogène de grande pureté. Les atouts de cette technologie induite par l'utilisation d'assemblage membrane électrode (AME) permettent son couplage aux énergies renouvelables. Toutefois, l'amélioration de l'activité catalytique des matériaux anodiques et leur stabilité pour baisser la tension de cellule et la diminution de la teneur en métaux nobles dans la composition des matériaux sont nécessaires.Lors de ces travaux de thèse, une voie de synthèse a été élaborée pour préparer des nanomatériaux à base de ruthénium. L'ajout d'iridium a permis dans un premier temps de prévenir l'oxyde de ruthénium de la dissolution tout en maintenant l'activité du catalyseur initial. Les meilleures performances catalytiques des AMEs en termes de densité de courant, de tension de cellule et de durabilité ont été délivrées avec les matériaux anodiques dont la composition molaire en Ru est supérieure à 70 %. La substitution partielle des métaux précieux (Ru et Ir) par du cérium et du niobium dans le but de proposer des catalyseurs à moindre coût a été aussi réalisée. Contrairement au niobium qui apporte une phase amorphe dans la structure du matériau, le cérium jusqu'à une teneur de 10 % permet de conserver les performances de l'anode telles que obtenues dans le matériau bimétallique. Le cérium se présente donc comme un métal prometteur à intégrer de manière appropriée dans la composition des matériaux anodiques.Hydrogen seems to be the most promising energetic vector in order to diversify the sources of energy production. Water splitting in a Proton Exchange Membrane Water Electrolyzer (PEMWE) provides a sustainable way of producing clean hydrogen. One of the main advantages of this technology based on the utilization of Membrane Electrode Assembling (MEA) is its potential coupling with renewable energy sources. However, the improvement of the catalytic activity of anode materials, their stability and the reduction of the noble metal content in their composition are required.During this thesis work, a new synthesis approach that consists in hydrolysis of metallic precursors in ethanol medium has been undertaken to prepare non-supported ruthenium-based nanomaterials. The addition of iridium to the nanocatalysts composition prevents the ruthenium oxide from dissolution without decreasing the initial activity of the anode catalyst. The best catalytic performance of MEAs in terms of current density, cell voltage and durability were observed with anode materials whose ruthenium molar composition is higher than 70 %. The partial substitution of precious metals (Ru and Ir) either by cerium or niobium with the purpose of decreasing the catalysts cost was also attempted. While the substitution with niobium introduces an amorphous phase in the material structure, the trimetallic materials containing cerium were shown to be crystalline. Furthermore, cerium contents up to 10 % allows maintaining the catalytic activity of the trimetallic anode close to that obtained with the bimetallic oxide material. Thus cerium appears as a promising metal to include in a suitable way on the composition of anode materials

IrO2Coated on RuO2as Efficient and Stable Electroactive Nanocatalysts for Electrochemical Water Splitting

International audienceWith the aim of obtaining a highly stable and active catalyst for oxygen evolution reaction (OER), a core–shell-like IrO2@RuO2material was synthesized by using a surface modification/precipitation method in ethanol medium. The comparison of this catalyst with pure RuO2and pure IrO2showed that the obtained mixed oxide catalyst displayed the highest amount of active sites as well as a good accessibility for water. Moreover, this catalyst was shown to be highly stable toward repetitive redox cycling. Polarization curves of the three catalysts showed that the IrO2@RuO2was the most active for the OER due to the large number and high accessibility of active sites. These catalytic benefic effects are attributed to an intimate contact between the two oxides in the IrO2-covered RuO2nanocatalyst that combines the RuO2intrinsic activity and the IrO2stability. The present study contributes therefore to the rational design of efficient and stable electrocatalysts for water splitting in acidic media

Non-aqueous aluminiumeair battery based on ionic liquid electrolyte

International audienceA promising metaleair secondary battery based on aluminiumeoxygen couple is described. In this paper, we observed that an aluminiumeair battery employing EMImCl, AlCl3 room temperature ionic liquid (RTIL) as electrolyte and aluminium as negative electrode, has an exceptional reduced self-discharged rate. Due to its new and innovative type of electrolyte, this aluminiumeair battery can support relatively high current densities (up to 0.6 mA cm-2) and an average voltage of 0.6e0.8 V. Such batteries may find immediate applications, as they can provide an internal, built-in autonomous and self-sustained energy source

Tuning of Pt and RuO2 based electrocatalysts towards a bifunctional oxygen electrode for a Unitized Regenerative Fuel Cell

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Effect of the annealing atmosphere on the electrochemical properties of RuO 2 nano-oxides synthesized by the Instant Method

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Preparation and characterization of supported Ru x Ir (1-x) O 2 nano-oxides using a modified polyol synthesis assisted by microwave activation for energy storage applications

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Elaboration and characterization of ruthenium nano-oxides for the oxygen evolution reaction in a Proton Exchange Membrane Water Electrolyzer supplied by a solar profile

International audienceHighly crystalline rutile-like structure ruthenium oxide material was synthesized from the hydrolysis method. A heat-treatment procedure was effective to recover catalyst powders free from organic carbon species which could be resulted in the traces of ethanol as solvent. Voltammetry (CV and LSV) and electrochemical impedance Spectroscopy (EIS) were used to determine the capacitance and the kinetic parameters of the RuO2 anodes for the oxygen evolution reaction (OER). The utilization of this catalyst as anode in a single cell PEM electrolyzer has shown high activity toward pure H-2 and O-2 gases production. Exchange current density and Tafel slope of 3.3 10(-8) A cm(-2) and 51 mV dec(-1), respectively determined at 60 degrees C, showed that the H2O oxidation to O-2 was limited by intermediate species formation step. During the durability tests in a 25 cm(2) single PEM water electrolyzer (PEMWE) supplied by a solar power profile, the area resistance was raised in the 300-345 m Omega cm(2) range and an efficiency loss of 330 mu V h(-1) was measured from 1.85V at 1 A cm(-2) and 80 degrees C