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The La0.75 Sr0.25 Cr0.5 Mn0.5 O3-´ (LSCM) catalyst and the novel Ru/La0.75 Sr0.25 Cr0.5 Mn0.5 O3-´ composite were investigated as alternative anodes for the direct utilization of propane in anode-supported solid oxide fuel cells. In particular, their synthesis and performance in direct propane reforming were studied. The LSCM powders were prepared by a sol–gel method based on a modified Pechini procedure. Single-phase LSCM perovskite powders were obtained. SEM micrographs of the LSCM powders revealed particles in the 200–300 nm range with a homogeneous grain distribution. The deposition of 5 wt.% metallic ruthenium nanoparticles on the LSCM perovskite powders was carried out by a microwave-assisted procedure. TEM investigations of Ru/LSCM composites showed a homogeneous distribution of metallic ruthenium nanoparticles with a mean grain size of around 2–3 nm. The catalytic activity of these potential anode materials was investigated for the following propane reforming processes: steam reforming (SR), autothermal reforming (ATR) and partial oxidation (POX) at 600, 700 and 800 °C. Very high propane conversion rates were observed under POX and ATR conditions at 700 and 800 °C for both the LSCM and Ru/LSCM compounds (> 92 at 700 °C and > 98% at 800 °C), whereas in the steam reforming environment, a satisfactory conversion was achieved only at 800 °C. The ruthenium presence was found to strongly improve the selectivity for H2 and syngas production for all of the experiments performed, reaching an approximately 90% syngas yield. Finally, good chemical stability after the catalytic tests was demonstrated for the LSCM and Ru/LSCM anode materials

Various recast Nafion] composite membranes containing ceramic oxide fillers with different surface characteristics (SiO2, SiO2-PWA, Al2O3, ZrO2) have been investigated for application in high temperature direct methanol fuel cells (DMFCs). Cell resistance at 145 _C increases as a function of the pH of slurry of the inorganic filler indicating a strong influence of the acid-base characteristics on the electrolyte conductivity. This effect has been attributed to the different water retention capabilities of the various membranes. Fuel cell performance at 145 _C, expressed as both maximum power density and current density at 0.5 V cell potential, increases almost linearly as the pH of slurry of the oxide materials decreases. Appropriate selection of the surface properties for the inorganic fillers allows to enhance the proton conductivity and extends the operating temperature range of composite membranes. The influence of fuel cell operating pressure on the humidification properties of these electrolytes at high temperature has been also investigated.

Methanol oxidation behaviour at three Pt–Ru catalysts varying by the concentration of active phase on the carbon support has been investigated in a wide temperature range (80–130°C). An increase of the adsorbed methanolic residue stripping charge is observed with the increase of catalyst dispersion. As the temperature is increased, the stripping peak potential shifts more negatively accounting for a lower activation barrier for the reaction. An increase of temperature above 90°C also produces a strong decrease in the coverage of adsorbed methanolic residues. The fuel cell performance is significantly enhanced by catalysts with intrinsically high catalytic activity, whereas the methanol reaction rate appears to be less influenced by an increase in coverage of active species. Catalysts characterized by a higher degree of alloying and metallic behaviour on the surface appear to be more active towards methanol oxidation. However, the physico-chemical properties of the catalysts have less influence on the anode electrochemical behaviour at high temperature since CO poisoning is alleviated under such conditions. The decrease of CO-like species coverage with temperature and the methanol tolerance characteristics of a Pt/C cathode are also discussed in relation to the crossover drawback of direct methanol fuel cells.

The structure, chemistry and morphology of unsupported Pt---Ru electro-catalysts of various compositions were investigated by X-ray diffraction (XRD), energy-dispersive analysis by X-rays and X-ray photoelectron spectroscopy. The metal surface-area of Pt---Ru catalysts prepared in an identical manner increased significantly with the increase in Ru content. The electro-catalytic activity of the catalysts towards methanol oxidation in direct methanol fuel cells (DMFC) was studied at 130 °C. A volcano-shape curve was obtained as a function of alloy composition for both mass and specific activities with a maximum occurring for the Pt:Ru (1:1) electro-catalyst. At low anodic overpotentials, an increase in both mass and specific activities as a function of bulk composition was found up to 50 at.% Ru, corresponding to about 40% Ru on the surface. These results indicate that the bifunctional mechanism governs the methanol electro-oxidation on Pt---Ru in the high temperature range, similarly to conventional DMFC operation (60–90 °C).