Sistema modelo de eletrocatalisadores Pt/Au para o estudo da eletro-oxidação de etanol

Abstract

In this work we propose the use of poly and single crystalline Au surfaces modified with Pt as a model system of core-shell nanoparticles to study the ethanol oxidation reaction (EOR). Results regarding the study of the influence of Pt coverage on the product yields of EOR are presented. The results show that the in the case of the Pt/Au-poly system, the Au surface modified with lower amounts of Pt has a higher ability to break the C-C bond present in the ethanol molecule. On the other hand, deposits having small amounts of Pt suffer a faster deactivation due to CO poisoning. This behavior is explained by the structure adopted by the catalytic layer. Additionally, results regarding the study of the influence of defects on the Au surfaces on the catalytic behavior of Pt layer will be shown. The results suggest that, even though Au active site are not in contact with electrolityc solution, the defects lying under the Pt layer influence the catalytic response of the layer. Specifically, as the step density in the Au substrate increases, the acetic acid path is privileged over the CO 2 production path. 89 Figura 35. Séries de espectros coletados durante a varredura anódica para a oxidação de etanol sobre Pt/Au(554) . Nº de interferogramas coletados: 60. Resolução: 8 cm -1 .(A) banda associada à formação de CO 2 , (B) banda de CO Linear , (C) região do espectro mostrando as bandas de CH 3 COOH e CH 3 CHO centradas em 1280 e 933 cm -1 , (D) região do espectro mostrando o estiramento C-H dos grupos CH 2 e CH 3 de etanol e (E) banda associada à formação de espécie CO adsorvida em uma configuração diferente da forma ponte ou linear.