Development of lanthanum strontium cobalt ferrite composite cathodes for intermediate- to low-temperature solid oxide fuel cells

Solid oxide fuel cells (SOFCs) offer high energy conversion, low noise, low pollutant emission, and low processing cost. Despite many advantages, SOFCs face a major challenge in competing with other types of fuel cells because of their high operating temperature. The necessity to reduce the operational temperature of SOFCs has led to the development of research into the materials and fabrication technology of fuel cells. The use of composite cathodes significantly reduces the cathode polarization resistance and expands the triple phase boundary area available for oxygen reduction. Powder preparation and composite cathode fabrication also affect the overall performance of composite cathodes and fuel cells. Among many types of cathode materials, lanthanum-based materials such as lanthanum strontium cobalt ferrite (La1-xSrxCo1-yFeyO3-δ) have recently been discovered to offer great compatibility with ceria-based electrolytes in performing as composite cathode materials for intermediate- to low-temperature SOFCs (IT-LTSOFCs). This paper reviews various ceria-based composite cathodes for IT-LTSOFCs and focuses on the aspects of progress and challenges in materials technology

Avanços recentes em nutrição de larvas de peixes

Os requisitos nutricionais de larvas de peixes são ainda mal compreendidos, o que leva a altas mortalidades e problemas de qualidade no seu cultivo. Este trabalho pretende fazer uma revisão de novas metodologias de investigação, tais como estudos com marcadores, genómica populacional, programação nutricional, génomica e proteómica funcionais, e fornecer ainda alguns exemplos das utilizações presentes e perspectivas futuras em estudos de nutrição de larvas de peixes

Search for excited leptons in proton-proton collisions at root s=8 TeV

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Highly conjugated multiporphyrins: synthesis, spectroscopic and electrochemical properties

A series of meso-to-meso ethynyl-bridged multiporphyrin arrays have been synthesized using Sonogoshira palladium-catalyzed cross-coupling reactions involving the appropriate ethynylporphyrin and iodoporphyrin precursors. The absorption spectra of these multiporphyrins show splitting of the Soret bands and significant red shifts of the Q bands as compared to the combination of the corresponding components. These conjugated multiporphyrins also show red shifts in their emission spectra as the pi-conjugation is expanded. In the electrochemical measurements, the porphyrins dimer 7 shows two 1-e(-) oxidations at E-1/2 =+ 0.63 and + 0.76 V for the first electron abstraction from the two porphyrin rings, indicating electronic communication between the two porphyrin units. The porphyrin trimer 4 exhibits the first and second 1-e(-) oxidations at E-1/2 =+ 0.68 and + 0.77 V, respectively, which correspond to the two outer porphyrins. The cyclic voltammogram of pentamer 5 shows two overlapping 1-e(-) couples at E-1/2 =+ 0.56 and + 0.66 V, and one 2-e(-) couple at E-1/2 =+ 0.86 V, for the four outer porphyrin units. These results demonstrate that in the porphyrin trimer and pentamer the individual peripheral porphyrin units are electrochemically coupled via a central porphyrin core. The UV-Vis-NIR spectra of the oxidized species of these multiporphyrins exhibit a broad intervalence charge transfer (IVCT) band in the region from 1200 to 3000 nm. The present work shows that a central porphyrin unit appended with ethynyl bridges affords strong electronic interactions between the peripheral porphyrin rings over a distance of about 15 angstrom