THENNER SILVA RODRIGUES
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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 25672 Ethanol steam reforming2019 - RODRIGUES, THENNER S.; SILVA, FELIPE A. e; CANDIDO, EDUARDO G.; SILVA, ANDERSON G.M. da; GEONMONOND, RAFAEL dos S.; CAMARGO, PEDRO H.C.; LINARDI, MARCELO; FONSECA, FABIO C.We reported herein a systematic investigation on how the nature of the support affected the catalytic performances of Rh nanoparticles. The prepared catalysts were denoted as Rh/MxOy, where M corresponded to Ce, Ti, Si, Zn, and Al, and Rh was Rh3+ reduction to Rh nanoparticles on the surface of oxides. This strategy was performed in a single step using urea as a mediator and in the absence of any other stabilizer or capping agent. The Rh nanoparticles displayed relatively similar sizes, shapes, and uniform distribution over the supports, differing only in terms of the nature of the support. This strongly affected the metal–support interaction between Rh nanoparticles and the respective oxides, leading to significant differences in their catalytic performances toward the ethanol steam reforming. Here, not only the catalytic activity (in terms of ethanol conversion) was affected, but both the selectivity and stability were also influenced by the nature of the oxide support. Interestingly, the reaction paths as well as the deactivation profile were completely changed as function of the employed support. Such differences were associated with differences in the oxygen storage, oxygen mobility, and acidity/basicity of the supports. We believe that our results can contribute to the development and understanding of Rh-supported catalysts for the applications toward gas-phase transformations such as the ethanol steam reforming reaction.Artigo IPEN-doc 25099 Synthesis of highly dispersed gold nanoparticles on Al2O3, SiO2, and TiO2 for the solvent-free oxidation of benzyl alcohol under low metal loadings2019 - GUALTEROS, JESUS A.D.; GARCIA, MARCO A.S.; SILVA, ANDERSON G.M. da; RODRIGUES, THENNER S.; CANDIDO, EDUARDO G.; SILVA, FELIPE A. e; FONSECA, FABIO C.; QUIROZ, JHON; OLIVEIRA, DANIELA C. de; TORRESI, SUSANA I.C. de; MOURA, CARLA V.R. de; CAMARGO, PEDRO H.C.; MOURA, EDMILSON M. deWe reported the organic template-free synthesis of gold (Au) nanoparticles (NPs) supported on TiO2, SiO2, and Al2O3 displaying uniform Au sizes and high dispersions over the supports. The Au-based catalysts were prepared by a deposition– precipitation method using urea as the precipitating agent. In the next step, the solvent-free oxidation of benzyl alcohol was investigated as model reaction using only 0.08–0.05 mol% of Au loadings and oxygen (O2) as the oxidant. Very high catalytic performances (TOF up to 443,624 h-1) could be achieved. Specifically, we investigated their catalytic activities, selectivity, and stabilities as well as the role of metal–support interactions over the performances. The conversion of the substrate was found to be associated with the nature of the employed support as the Au NPs presented similar sizes in all materials. A sub-stoichiometric amount of base was sufficient for the catalyst activation and the observation of the catalysts profile over the time enable insights on their recyclability performances. We believe this reported method represents a facile approach for the synthesis of uniform Au-supported catalysts displaying high performances.