Temperature‐Dependent Methanol Electro‐Oxidation on Well‐Characterized Pt‐Ru Alloys

Abstract

The kinetics of methanol electro‐oxidation on well‐characterized Pt‐Ru alloy surfaces were measured in sulfuric acid solution as a function of temperature. The alloy surfaces were prepared in ultrahigh vacuum with the surface composition determined by low energy ion scattering. It was found that the activity of Ru towards the dissociative adsorption of methanol is a strong function of temperature. This change in the adsorptive nature of the Ru sites with temperature produced a variation in the optimum surface composition with temperature. The optimum surface had an Ru content which increased with increasing temperature, from close to ≈10 atomic percent (a/o) Ru at 25°C to a value in the vicinity of ≈30 a/o at 60°C. The shift in optimum composition with temperature was attributed to a shift in the rate‐determining step from methanol adsorption/dehydrogenation at low temperature to the surface reaction between the dehydrogenated intermediate and surface oxygen at high temperature. The apparent activation energies were consistent with this change in the rate‐determining step.

A Multielectrode Electrochemical and Scanning Differential Electrochemical Mass Spectrometry Study of Methanol Oxidation on Electrodeposited PtxRuy

“…As the temperature is increased, the ability of Ru sites to adsorb and decompose methanol improves, which results in improved performance for higher-Ru-content electrodes. 57 The current efficiencies plotted in Figure 7B also depict a change in behavior at higher temperatures. At 25°C, the Pt 100 Ru 0 electrode exhibited the greatest conversion of methanol to carbon dioxide at over 90%.…”

Eletro-oxidação de etanol sobre eletrocatalisadores PtRh/C, PtSn/C e PtSnRh/C preparados pelo método da redução por álcool

“…Os eletrocatalisadores PtRh/C com razões atômica Pt:Rh 90:10 e 50:50 apresentam quatro picos de difração em aproximadamente 2θ = 40 o , 47 o , 67 o e 82 o os quais são associados aos planos (111), (200), (220) e (311), respectivamente, da estrutura cúbica de face centrada (CFC) de platina e ligas de platina [20]. Os cálculos do parâmetro de rede [21] [24]. Para os cál-culos do tamanho médio de cristalito utilizando a equação de Scherrer (Tabela 1) foram selecionados os picos de difração correspondente ao plano (220) dos diferentes eletrocatalisadores.…”

“…e velocidade de varredura de 2°min -1 . O tamanho médio de cristalito foi estimado através dos difratogramas de raios X utilizando a equação de Scherrer [21].…”

On the role of Ru and Sn as promotors of methanol electro-oxidation over Pt

“…The activity of Ru for the methanol adsorption appears to be strongly temperature dependent. In a recent article Gasteiger et al [13] showed that at 60°C the optimum Ru composition is about 30%.…”