THENNER SILVA RODRIGUES
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Artigo IPEN-doc 26691 Lowering the sintering temperature of a SOFC by morphology control of the electrolyte powder2019 - MACHADO, M.; MORAES, L.P.R.; RODRIGUES, L.N.; RODRIGUES, T.S.; FONSECA, F.C.Solid oxide fuel cells are fabricated by two-step sintering at low temperature by controlling the morphology of the gadolinium-doped cerium oxide (GDC) electrolyte powders. The GDC electrolyte was synthesized by a hydrothermal route to obtain highly reactive nanorods that can fully densify at temperatures around 1150 °C. The developed system consists of the GDC electrolyte support, lanthanum strontium cobalt ferrite (LSCF) cathode and Ni/GDC anode. The electrolyte support was prepared by uniaxial die pressing and sintered at 1150 °C, and fuel cells were obtained by co-sintering electrode layers at the same temperature. The performance of the cell was evaluated in hydrogen at intermediate temperatures (IT). The experimental results indicate that high-performance IT-SOFC can be obtained at low sintering temperatures by controlling the morphology of electrolyte powder.Artigo IPEN-doc 25839 Tuning diffusion paths in shaped ceria nanocrystals2019 - ESPOSITO, VINCENZO; KABIR, AHSANUL; ROSA, MASSIMO; NONG, NGO V.; RODRIGUES, THENNER S.; RODRIGUES, LAYS N.; MACHADO, MARINA F.S.; MORAES, LETICIA P.R.; MARANI, DEBORA; FONSECA, FABIO C.Mass diffusion controls material structuring from the atomic to the macro-scale defining properties and functionalities. We show here that surface energy in Ce0.9Gd0.1O3-d shaped nanocrystals, i.e. nanocubes, nanorods and spherical nanoparticles, can control solid state diffusion mechanisms over a long range, leading to extreme microstructural diversity.Artigo IPEN-doc 25155 Sub-15 nm CeO2 nanowires as an efficient nonnoble metal catalyst in the room-temperature oxidation of aniline2018 - SILVA, ANDERSON G.M. da; BATALHA, DANIEL C.; RODRIGUES, THENNER S.; CANDIDO, EDUARDO G.; LUZ, SULUSMON C.; FREITAS, ISABEL C. de; FONSECA, FABIO C.; OLIVEIRA, DANIELA C. de; TAYLOR, JASON G.; TORRESI, SUSANA I.C. de; CAMARGO, PEDRO H.C.; FAJARDO, HUMBERTO V.We described herein the facile synthesis of sub-15 nm CeO2 nanowires based on a hydrothermal method without the use of any capping/stabilizing agent, in which an oriented attachment mechanism took place during the CeO2 nanowire formation. The synthesis of sub-15 nm CeO2 nanowires could be achieved on relatively large scales (∼2.6 grams of nanowires per batch), in high yields (>94%), and at low cost. To date, there are only a limited number of successful attempts towards the synthesis of CeO2 nanowires with such small diameters, and the reported protocols are typically limited to low amounts. The nanowires displayed uniform shapes and sizes, high surface areas, an increased number of oxygen defects sites, and a high proportion of Ce3+/Ce4+ surface species. These features make them promising candidates for oxidation reactions. To this end, we employed the selective oxidation of aniline as a model transformation. The sub-15 nm CeO2 nanowires catalyzed the selective synthesis of nitrosobenzene (up to 98% selectivity) from aniline at room temperature using H2O2 as the oxidant. The effect of solvent and temperature during the catalytic reaction was investigated. We found that such parameters played an important role in the control of the selectivity. The improved catalytic activities observed for the sub-15 nm nanowires could be explained by: i) the uniform morphology with a typical dimension of 11 ± 2 nm in width, which provides higher specific surface areas relative to those of conventional catalysts; ii) the significant concentration of oxygen vacancies and high proportion of Ce3+/Ce4+ species at the surface that represent highly active sites towards oxidation reactions; iii) the crystal growth along the (110) highly catalytically active crystallographic directions, and iv) the mesoporous surface which is easily accessible by liquid substrates. The results reported herein demonstrated high activities under ambient conditions, provided novel insights into selectivities, and may inspire novel metal oxide-based catalysts with desired performances.