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International audience; Interest in hydrogen as a possible energy vector is powered by the depletion of fossil fuel feedstocks as well as concerns over global warming, which brings new environmental legislations on the emission of greenhouse gases into the atmosphere. At this point, the future perspective of a hydrogen economy has triggered many researchers to develop and optimize a series of new technologies which differ from conventional industrial processes (like SMR, ATR, POX, and H2O-electrolysis) in their orientation toward the minimization of emission of greenhouse gases (on-site CO2 capture), utilization of renewable feedstock (bio-alcohols, bio-gases, wood, and algae), or renewable energy sources (wind, sunlight, or tides). This chapter gathers information on the most relevant technologies for hydrogen production, including discussions on existing conventional reformingprocesses, as well as developments in advanced and more environmentally benign methods, like chemical-looping.

International audience; Spinel oxide nanoparticles of MxCo2 − xMnO4 (M = Ni, Zn, Cu; 0 < x < 1) were prepared at 120 °C by the inorganic polycondensation method. Phase composition and microstructure of each sample powder thus obtained were characterized by X-ray diffraction, X-ray fluorescence and scanning electron microscopy. Nanoparticles are well crystallized and uniformly distributed in both shape and size. Colloidal dispersions were stabilized in a low cost and environmentally friendly solvent solution. Spinel oxide thin films were then deposited on glass substrates by using the dip-coating technique. Their optical properties were measured in the 300–1100 nm wavelength range. Thin films show extremely good absorbance in the ultra-violet and blue regions. The highest absorbance observed in the red region was for x = 0.15 in zinc. A smaller direct band gap was determined when a low amount of doping M element was introduced in the cobalt and manganese spinel oxide material.

International audience; Iron cobaltite thin films with spinel structure have been elaborated by radio-frequency (RF) magnetronsputtering from a Co1.75Fe1.25O4 target. Influence of argon pressure on structure, microstructure and physicalproperties of films has been examined. Iron–cobalt oxide thin films essentially consist of one spinel phasewhen deposited at low pressure (0.5 and 1.0 Pa). At high pressure (2.0 Pa), the global stoichiometry of the filmis changed which results in the precipitation of a mixed monoxide of cobalt and iron beside the spinel phase.This in-situ reduction due to an oxygen loss occurring mainly at high deposition pressure has been revealed byX-ray diffraction and Raman spectroscopy. Microstructural evolution of thin film with argon pressure has beenshown by microscopic observations (AFM and SEM). The evolution of magnetic and electrical properties, versusargon pressure, has been also studied by SQUID and 4 point probe measurements.

Spinel CoMnFeO4 thin films are stable materials useful to study the influence of radio-frequency (RF) sputtering experimental conditions on the microstructure of oxide films. It has been demonstrated by various techniques such as electronic and atomic force microscopy (AFM), gas adsorption techniques and ellipsometry, that films prepared with 0.5 Pa sputtering argon pressure and 5 cm target–substrate distance are very dense. On the other hand, the samples obtained under higher pressure and/or longer distances are microporous with a mean pore size generally lower than 2 nm. The specific surface areas of such films reach about 75 m2/g. According to the simple model proposed, the films are made of three layers. From the bottom to the top of the film, the first one at the interface with the substrate is 100% dense. The second layer is made of cylindrical rods set up according to a compact plane. Its porosity is due to the lattice interstices. Hemispheric domes covering each rod make up the third layer, which displays a degree of roughness related to the shape and the hexagonal arrangement of the domes. The surface enhancement factor (SEF), the porosity and roughness, calculated from the model, are in corroboration with the experimental values. The porosity factor is however slightly underestimated by the model for very porous samples.