Methanol oxidation bimetallic electrode

What is the stability of such a bimetallic electrode, as well as that of other bimetallic and multimetallic electrodes, which exhibit high activity for methanol oxidation ... 

Until now, for methanol oxidation the best bimetallic catalyst was found to be Pt-Ru. Several papers deal with the electro-oxidation of methanol at Pt-Ru bimetallic system dispersed in polyaniline [33,46]. From results with bulk alloys, the optimum Pt/Ru ratio of around 6 1 to 4 1 was found [49] and confirmed [50]. The electroactivity of Pt-Ru-modified polyaniline is much better than that displayed by pure Pt particles dispersed into the PAni film. The optimum composition of the Pt-Ru bimetallic system was confirmed from these results [33]. The decrease of the poisoning phenomenon is the consequence of a low coverage in adsorbed CO resulting from the chemisorption of methanol. This was checked by considering the oxidation of CO at the same Pt-Ru/PAni-modified electrode [34], which occurs at low overvoltages (150 mV) in the presence of Ru. 

As was previously mentioned, PtRu alloys exhibit improved performance over pure Pt alloys.117,118 This is primarily a result of the ability of Ru to dissociate H20 for reaction with CO adsorbed on Pt sites.115,116 That CO oxidation on pure Ru is unfavorable indicates that on the bimetallic surface, CO is oxidized only on the Pt sites.119 Thus, CO is oxidized on Pt sites adjacent to Ru sites, where water is activated.120,121 This is known as a bifunctional mechanism. In addition, the presence of Ru atoms reduces the adsorption energy of CO on neighboring Pt atoms, lowering the activation energy of CO oxidation.122 This effect is purely electronic and is less significant than the bifunctional effect of Ru.123 One significant limitation of PtRu is the weak adsorption of methanol on Ru, particularly at room temperature.117,124 The weak adsorption severely hinders methanol decomposition, which is evident in Fig. 7 by the drop in current density for PtRu electrodes with high Ru composition.125... 

Comprehensive EXAFS reviews on catalysis have been recently published. These encompass studies concerning surface mediated electrochemical processes and catalytic solids under environmental conditions. The first set of studies examined the local structural changes in the metal occurring in tandem with redox processes under voltage control. " Recent work in this area examines the stability of bimetallic Pt-Ru electrodes and their performance in the hydrogen oxidation reaction in the presence of CO or direct methanol fuel cells. Studies reviewed involving supported metal catalysts concern, in the first place, the reduction process " while other studies also consider the oxidation process and reduction under inert gases. All of these studies make an attempt to understand the relevance of the metal support interface... 

Yi Q, Zhang J, Chen A, Liu X, Xu G, Zhou Z (2008) Activity of a novel titaniirm-supported bimetallic PtSn/Ti electrode for electrocatalytic oxidation of formic acid and methanol. J Appl Electrochem 38 695-701... 

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