Detalhes bibliográficos
| Ano de defesa: |
2012 |
| Autor(a) principal: |
Botelho, Alielson Corrêa
 |
| Orientador(a): |
TAKANA, Auro Atsushi |
| Banca de defesa: |
Bezerra, Cicero Wellington Brito
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| Tipo de documento: |
Dissertação
|
| Tipo de acesso: |
Acesso aberto |
| Idioma: |
por |
| Instituição de defesa: |
Universidade Federal do Maranhão
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| Programa de Pós-Graduação: |
PROGRAMA DE PÓS-GRADUAÇÃO EM QUÍMICA/CCET
|
| Departamento: |
QUIMICA
|
| País: |
BR
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| Palavras-chave em Português: |
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| Palavras-chave em Inglês: |
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| Área do conhecimento CNPq: |
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| Link de acesso: |
http://tedebc.ufma.br:8080/jspui/handle/tede/935
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Resumo: |
The oxygen reduction reaction (ORR) in 1.0 mol/L KOH solutions catalyzed by FeTMPP/C and CoTMPP/C was investigated in absence and presence of BH4- anions with concentrations varying from 10-7 to 1.0 mol/L. Similar cyclic voltammetry and rotating disk electrode experiments have been also performed the commercial E-TEK Pt/C electrocatalysts. In absence of BH4- anions, the ORR proceeds via a direct 4 electron pathway on FeTMPP/C and Pt/C and via a peroxide pathway involving (2-electron process) on CoTMPP/C and Au/C catalysts. In addition, Pt/C presented the most positive onset potential for the reaction. In presence of BH4- anions, a drastic loss in the catalytic activity of the Pt/C electrode was observed, even for concentrations as low as 10-7 mol/L. The effect of temperature on the ORR was studied and from 20ºC up to 60ºC the diffusion limited current densities remained nearly constants. At 80ºC, a decrease in the current of density was observed, probably due to a decrease in the oxygen concentration and viscosity of the solution. Arrhenius plots [ln (k) vs. T-1] were used to evaluate the activation s energy (Ea) of the ORR in absence of borohydride and resulted in 47.6 kJ/mol and 50.3 kJ/mol for Pt/C and FeTMPP/C, respectively. In presence of borohydride in solution, the Ea value for Pt/C showed a pronounced decrease to 38.7 kJ/mol, due to borohydride oxidation as a parallel reaction, while for FeTMPP/C the value calculate was 52.7 kJ/mol, i.e., remained practically constant. Such results indicates that FeTMPP is an efficient catalyst for ORR in alkaline solutions and tolerant to BH4 anions. |
