| Afiliação do(s) autor(es): | [1] Univ Sao Paulo, Inst Quim Sao Carlos, BR-13560970 Sao Carlos, SP - Brazil
[2] Univ Fed Maranhao, Dept Quim, BR-65080040 Sao Luis, MA - Brazil
Número total de Afiliações: 2
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Hydrogen, in the ethanol molecule, can be utilized in indirect hydrogen fuel cells. In this device, ethanol can be dehydrogenated producing H-2 and acetaldehyde in an external fuel processor, and the H-2 molecules are electro-oxidized in the anode. The anode electrocatalyst can, additionally, be active for the electro-oxidation of residual ethanol or acetaldehyde, but must catalyze the reaction via the C-2-pathway (intact C C bond), in order to avoid the formation poisoning species. This work investigated potential materials that are active for H-2 and catalyze the selective electro-oxidation of ethanol and acetaldehyde via the C-2-pathway. The bimetallic electrocatalysts were formed by W, Ru and Sn-modified Pt nanopartides. The reaction products were followed by on-line differential electrochemical mass spectrometry (DEMS) experiments. The results showed that Ru/Pt/C and Sn/Pt/C presented higher overall reaction rate when compared to the other studied materials. However, they were non-selective, even at different atomic proportions, and catalyzed the reaction in parallel pathways producing CO2 and acetaldehyde, with Ru/Pt/C presenting the highest average current efficiency for CO2 formation (16.6%). On the other hand, W/Pt/C with high W content was more selective to the Cy route, evidenced by the absence of the DEMS signals for molecules with one carbon atom such as CH4 and CO2. Additionally, this material was active and stable for Hy electro-oxidation, even in the presence of acetaldehyde in solution, contrarily to what was observed for Pt/C, and this was associated to its activity for Hy oxidation and its inability for the C C dissociation, as evidenced by the DEMS measurements. The high selectivity obtained for the W/Pt/C material to the C-2-pathway, and its capability for hydrogen electro-oxidation, is an important novelty in this work, as it turns into a potential electrocatalyst for application in the anode of indirect hydrogen fuel cells powered by ethanol, mainly for those that operates as auxiliary power units of internal combustion engine cars. (C) 2014 Elsevier B.V. All rights reserved. (AU) |