Martín G. Bellino

Preparation and ionic transport properties of YDC–YSZ nanocomposites

The ionic transport properties of dense nanocomposites of yttria-doped ceria (YDC) and yttria-stabilized zirconia (YSZ), in a volume ratio of 1 : 1, have been investigated by electrochemical impedance spectroscopy. These materials were prepared by means of a fast-firing process starting from nanopowders with high specific surface area, avoiding the formation of secondary phases and minimizing the opportunity for grain growth to occur during sintering. An important enhancement of the total ionic conductivity with decreasing crystallite size was observed, as reported in the literature for other nanostructured ionic conductors. This result can be attributed to an almost ideal parallel connection between both nanophases, coupled to an increase of their grain boundary ionic diffusivity. In addition, it was proved that the presence of the YSZ phase significantly improves the mechanical properties of ceria-based nanoceramics.

Catalytic Behavior of PdO ∕ NiO ∕ SDC Composites for Partial Oxidation of Methane: Application as Anodes of Single-Chamber IT-SOFCs

PdO/NiO/SDC composites (SDC: Sm 2 O 3 -doped CeO 2 ) have been proposed to be excellent anodes for single-chamber, intermediate-temperature solid oxide fuel cells (SC-IT-SOFCs) operated under mixtures of CH 4 and air, reaching high power densities at relatively low working temperatures. In this work we evaluated the catalytic activity of these composites in the partial oxidation of CH 4 , finding that their high performance is due to the excellent catalytic properties of these materials. The effect of the addition of PdO was investigated by analyzing NiO/SDC and PdO/NiO/SDC composites under different reaction temperatures and CH 4 :O 2 ratios. Finally, PdO/NiO/SDC composites were evaluated under operation in SC-IT-SOFCs similar to those reported in the literature using SDC electrolytes and Sm 0.5 Sr 0.5 CoO 3 cathodes. Our results confirmed the feasibility of SC-IT-SOFCs.

Performance of Ag/La0.6Sr0.4Co1-xFexO3 (x = 0 - 0.8) Nanotube Composite Cathodes for IT-SOFCs

We investigated the performance of Ag/La0.6Sr0.4Co1-xFexO3 (x = 0;0.8) nanotube composite cathodes using samaria-doped ceria as electrolyte. These composites were prepared by mixing a commercial Ag paste and La0.6Sr0.4Co1-xFexO3 (x = 0;0.8) nanotubes synthesized by the pore wetting technique using plastic templates. Electrochemical impedance spectroscopy analyses showed that the incorporation of La0.6Sr0.4Co1-xFexO3 nanotubes significantly enhances the performance of the cathode in comparison to pure Ag due to their high specific surface area.

Performance of Single-Chamber Intermediate-Temperature SOFCs Operated in Methane/Air Mixtures using PdO/NiO/CeO2-Sm2O3 Anodes

In recent years, new concepts have been explored in order to find anodes adequate for operation with hydrocarbon fuels with high catalytic activity at intermediate temperatures, since the usual internal reforming of methane requires very high temperatures. In this sense, single-chamber SOFCs have attracted great attention because they take advantage of the ambient oxygen to produce H2 and CO by the partial oxidation of the hydrocarbon. In this work, we studied the performance of single-chamber intermediatetemperature SOFCs operated with methane as fuel using PdO/NiO/CeO2-Sm2O3 anodes. CeO2-Sm2O3 and Sm0.5Sr0.5CoO3 were used as electrolyte and cathode, respectively. All these materials were prepared by low-cost wet chemical methods. Our results showed that the incorporation of PdO in the anode allows to reach high peak power densities, of about 100 mW/cm 2 at 600°C.