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Use este identificador para citar ou linkar para este item: https://tedebc.ufma.br/jspui/handle/tede/tede/928
Tipo do documento: Dissertação
Título: DESEMPENHO DE ELETRODOS Pt/C, Pt3Cr/C E PtCr/C PARA APLICAÇÕES EM CÁTODOS DE CÉLULAS A COMBUSTÍVEL DE METANOL DIRETO
Título(s) alternativo(s): PERFORMANCE OF ELETRODOS Pt / C, Pt3Cr/CE PtCr / C FOR INVESTMENTS IN CATHODES OF THE FUEL CELLS IN METANOL DIRECT
Autor: Varela Júnior, Jaldyr de Jesus Gomes
Primeiro orientador: TAKANA, Auro Atsushi
Resumo: This work presents oxygem reduction reaction (ORR) studies on platinum (Pt/C) and platinum-chromium alloys containing 50% (PtCr/C) or 70% in chromium (Pt3Cr) dispersed on high surface area, in acid aqueous solutions with and without metanol, with cyclic voltammetry, chronoamperometry and rotating disk electrode techniques. Electrochemical measurements have been also performed in a direct methanol unit fuel cell. The electrocatalysts were characterized by energy dispersive X-ray (EDX) and X-ray diffraction (XRD) analyses. The ORR studies in absence of methanol in solution showed that chromium adittion does not change the reaction mechanism observed on the Pt/C and the electrocatalytic activity increases in the order PtCr/C < Pt/C < Pt3Cr/C. Such increase was attributed to a favourable interatomic distance for O2 dissociative adsorption. The alloys showed higher tolerance to methanol presence in solution than Pt, mainly the PtCr electrode due to smaller amount of active sites to methanol adsorption with respect to Pt. In solutions containing low concentration of methanol, the ORR mechanism was not affected by methanol presence. The polarization curves recorded with the unit cell showed that na increase in temperature results in an increase in the electrocatalitic activity of the anode, as well as na increase in methanol diffusion through the Nafion® membrane with consequent cathode depolarization. Furthermore, the system containing Pt3Cr/C as cathodic electrode material presented the best electrochemical performance, with power densities of ~ 55 mW cm-2, in contrast to ~ 40 mW cm-2 for the unit cell with Pt/C cathode and ~ 20 mW cm-2 with PtCr/C.
Abstract: This work presents oxygem reduction reaction (ORR) studies on platinum (Pt/C) and platinum-chromium alloys containing 50% (PtCr/C) or 70% in chromium (Pt3Cr) dispersed on high surface area, in acid aqueous solutions with and without metanol, with cyclic voltammetry, chronoamperometry and rotating disk electrode techniques. Electrochemical measurements have been also performed in a direct methanol unit fuel cell. The electrocatalysts were characterized by energy dispersive X-ray (EDX) and X-ray diffraction (XRD) analyses. The ORR studies in absence of methanol in solution showed that chromium adittion does not change the reaction mechanism observed on the Pt/C and the electrocatalytic activity increases in the order PtCr/C < Pt/C < Pt3Cr/C. Such increase was attributed to a favourable interatomic distance for O2 dissociative adsorption. The alloys showed higher tolerance to methanol presence in solution than Pt, mainly the PtCr electrode due to smaller amount of active sites to methanol adsorption with respect to Pt. In solutions containing low concentration of methanol, the ORR mechanism was not affected by methanol presence. The polarization curves recorded with the unit cell showed that na increase in temperature results in an increase in the electrocatalitic activity of the anode, as well as na increase in methanol diffusion through the Nafion® membrane with consequent cathode depolarization. Furthermore, the system containing Pt3Cr/C as cathodic electrode material presented the best electrochemical performance, with power densities of ~ 55 mW cm-2, in contrast to ~ 40 mW cm-2 for the unit cell with Pt/C cathode and ~ 20 mW cm-2 with PtCr/C.
Palavras-chave: Redução de oxigênio
oxidação de metanol
platina-cromo
Oxygen reduction
methanol oxidation
platinum-chromium
Área(s) do CNPq: CNPQ::CIENCIAS EXATAS E DA TERRA::QUIMICA::QUIMICA ANALITICA
Idioma: por
País: BR
Instituição: Universidade Federal do Maranhão
Sigla da instituição: UFMA
Departamento: QUIMICA
Programa: PROGRAMA DE PÓS-GRADUAÇÃO EM QUÍMICA/CCET
Citação: VARELA JÚNIOR, Jaldyr de Jesus Gomes. PERFORMANCE OF ELETRODOS Pt / C, Pt3Cr/CE PtCr / C FOR INVESTMENTS IN CATHODES OF THE FUEL CELLS IN METANOL DIRECT. 2006. 104 f. Dissertação (Mestrado em QUIMICA) - Universidade Federal do Maranhão, São Luis, 2006.
Tipo de acesso: Acesso Aberto
URI: http://tedebc.ufma.br:8080/jspui/handle/tede/928
Data de defesa: 14-Jul-2006
Aparece nas coleções:DISSERTAÇÃO DE MESTRADO - PROGRAMA DE PÓS-GRADUAÇÃO EM QUIMICA

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