Síntese e caracterização de catalisadores nanoestruturados contendo PtSnCu para a oxidação eletroquímica de etanol
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2019-11-28
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Universidade Federal de Goiás
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Renewable energies are increasingly desirable. One of the proposed alternatives is proton-exchange membrane fuel cells (PEMFC). The use of ethanol as fuel in these cells is advantageous because it has a low contribution to the greenhouse effect when the CO2 cycle is completed. However, complete oxidation of the ethanol requires the breaking of the CC bond, to oxidize the intermediates that are formed during the reaction, which are stable and if not oxidized promote a decrease in the efficiency, due to the poisoning of Pt. The study is presented with catalysts of PtxSnyCuz supported on high surface area colloidal carbon. The electrocatalysts were produced with the alcohol reduction method. The synthesis used with modification to obtain the materials allowed the formation of nanoparticles with high catalytic activity, in the range of 2 to 3 nm. The physical characterization techniques used, such as XRD, MET and XPS, allowed to verify that the particles are crystalline, with majority crystal of the CFC structure of Pt, and that Sn and Cu atoms were inserted in this crystal, causing modifications in the peaks to the crystalline planes of the Pt network. Microscopies showed the morphology of the nanoparticles and helped to understand the relation of the high catalytic activity with the good dispersion of particles and their high surface area coming from their size. The analysis by XPS allowed to prove the elements present in the samples, besides determining the composition of atoms in the surface in which the catalysis occurs. The electrochemical characterization by VC showed the high activity of the ternaries with low potential values for the beginning of the ethanol oxidation compared to the Pt/C, PtSn/C and PtCu/C catalysts. The chromaamperometric technique evaluated the stability of the catalysts and verified that in the studied time the materials have constant and stable behavior. Through the EIS it was possible to understand the electrical resistance of the catalytic surface and to verify that such property for the ROE decreases as the potential increases, the studied compositions showed that the composition of the material influences in the reduction of the electrical resistance when oxidizing the molecule of ethanol and that can two or more reaction mechanisms occur during catalysis.
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MAGALHÃES, M. M. Síntese e caracterização de catalisadores nanoestruturados contendo PtSnCu para a oxidação eletroquímica de etanol. 2023. 119 f. Tese (Doutorado em Química) - Universidade Federal de Goiás, Goiânia, 2019.