Oxygen transport mechanisms through the mixed conductor membrane and elaboration of new design for oxygen separation application

International audienc

Impact de la rugosité de surface sur les performances de semi-perméation de membrane de structure pérovskite du type La1-xSrxFe1-yGayO3-δ,

National audienc

Impact of the surface roughness on the oxygen semi-permeation performances of La1-xSrxFe1-yGayO3-δ perovskite membranes

International audienc

Alternated bimetallic [Ru–M] (M = Fe2+, Zn2+) coordination polymers based on [Ru(bpy)3]2+units connected to bis-terpyridine ligands: synthesis, electrochemistry and photophysics in solution or in thin film on electrodes

International audienceTwo alternated bimetallic Ru–Fe and Ru–Zn coordination polymers, [{RuII(bpy)2(L2)MII}n]4n+ (M = Fe2+, Zn2+), were synthesized using the [Ru(bpy)2(L2)]2+ (bpy = 2,2′ bipyridine) complex as a building block, in which L2 is a bipyridine ligand substituted by two terpyridine sites. The [Ru(bpy)3]2+ like-subunits provide the assemblies with photoredox properties whereas the second metal allows the build-up of the polymer structure by coordination of the free terpyridine units, associated with additional redox activities. Thin robust films of these metallo supramolecular structures can be easily obtained as a coating on electrode surfaces (C, Pt, and ITO) by a simple electrochemical procedure based on an electroreductive precipitation adsorption process. The morphology of the films has been characterized by AFM. Electrochemical and photophysical properties of these coordination polymers were investigated in CH3CN solution as well as thin films deposited on an electrode. The Ru(II)–Zn(II) film, deposited on a transparent ITO electrode, displays luminescence properties. On the other hand, the Ru(II)–Fe(II) film exhibits electrochromic properties under continuous cycling over the FeII/FeIII and RuII/RuIII waves, shifting from reddish dark at the Fe(II)–Ru(II) reduced state to orange-yellow at the Fe(III)–Ru(II) state and to pale green at the more oxidized state Fe(III)–Ru(III). These oxidation processes can be also driven by visible light. Indeed, upon continuous irradiation of an CH3CN solution of the Ru–Fe polymer in the presence of a diazonium salt as a sacrificial electron acceptor, the fast quantitative one-electron oxidation of the Fe(II) centers followed by that of the Ru(II) ones occurs, despite the strong quenching of the luminescence of the Ru(II) moieties by the Fe(II) center. The photoinduced oxidation of the Fe(II) center is still efficient when the Ru(II)–Fe(II) polymer is electrodeposited as a thin film on ITO leading to the storage of an oxidative equivalent on an electrode

Efficient photocatalytic hydrogen production in water using a cobalt(iii) tetraaza-macrocyclic catalyst: electrochemical generation of the low-valent Co(i) species and its reactivity toward proton reduction

International audienc

Visible Light-Driven Electron Transfer from a Dye-Sensitized p-Type NiO Photocathode to a Molecular Catalyst in Solution: Toward NiO-Based Photoelectrochemical Devices for Solar Hydrogen Production

International audienceThe photoelectrochemical activity of a mesoporous NiO electrode sensitized by a ruthenium complex was investigated with several rhodium and cobalt H-2-evolving catalysts. Photocurrent as high as 80 mu A/cm(2) was produced by irradiation of such photocathode in the presence of the Rh(III) polypyridyl complexes, while cobalt complexes gave almost no photocurrent. Photolysis experiments led to the two-electron reduced form of the Rh(III) complexes into Rh(I) complexes and demonstrate the occurrence of an electron transfer chain from NiO to the catalyst. Mott-Schottky experiments evidenced the pH dependence of the NiO flat band potential, explaining the dramatic drop of the photocurrent in acidic conditions (cyanoanilinium). By contrast, in weaker acid conditions (formic acid) the photocurrent increases and the key Rh(III) hydride intermediate was efficiently generated. In acetonitrile solution, Rh(III)-H slowly reacts with HCOOH to generate H-2. However, this process was not catalytic, because the reduction potential of the Ru sensitizer is not sufficiently negative to reduce the Rh(III)-H into Rh(II)-H