Catalysts alloy metals

Interpretation of this observed correlation between a lowered affinity of the metal surface to oxygen and a higher rate of ORR measured at a Pt shell over a Pt-alloy core has also been at the center of recent theoretical work, based primarily on DFT calculations of electronic properties and surface bond strengths for a variety of expected ORR intermediates at metal and metal alloy catalysts. The second part of this chapter contains a discussion of these valuable contributions and of outstanding issues in tying together this recent theoretical work and ORR experimental data. 

A systematic investigation of dehydrogenation activity over a variety of metal alloy catalysts has been made by Schwab and co-workers (51-53), who have successfully interpreted their results in terms of the bulk metal theory. The test reaction used, namely the dehydrogenation of formic... 

McKee (21, 195) and McKee and Norton (219, 249, 250) have reported compensation effects in the exchange reactions of methane on several pairs of binary noble metal alloy catalysts. For each combination of elements kinetic measurements were made at a number of different compositions. Although the compensation behavior was generally very similar, there were perceptible differences in the values of B and e calculated for the various alloy combinations. The parameters found, by use of the formulas given in Appendix II, are summarized in Table IV, A-E, and are subject to the following comments. In consideration of data for the Pd-Rh alloys, the point for... 

CRMs in the area of technical and industrial materials (e.g., pure metals, alloys, catalysts for cars, semiconductors, fossil fuels, glasses, plastics)... 

Although bimetallic catalysts did not represent a totally new area of research in the early 1960s, my research emphasized entirely new aspects of this subject. Earlier work on metal alloy catalysts was dominated by efforts to relate the catalytic activity of a metal to its electron band structure. Very little attention had been given to other aspects of metal alloy catalysts, such as the possibility of influencing the selectivity of chemical transformations on metal surfaces and of preparing metal alloys in a highly dispersed state. These aspects were the basis for my work on bimetallic catalyst systems. 

Metal alloys catalyst candidates Serial MS screening of a 15 x 15 x 15 libraries with 120 different compositions Kinetics of catalytic reactions 26 o r tn n o... 

While the above discussion has dealt with hquid systems, it is noteworthy that surface solution theory is also of interest for sohds. For example, the surface composition of metal alloy catalyst particles can differ significantly from the bulk composition. The proper design of the catalyst thus requires knowledge of how bulk and surface compositions are related. 

Figure 3.4 Schematics of ORR electrocatalyst s morphologies. (A) Metal catalyst such as Pt and metal alloy catalyst such as PtPd supported on a conductive material such as carbon or metal oxide (B) core—shell catalyst such as Au Pt supported on conductive material such as carbon or metal oxide (C) metal catalyst such as Pt and metal alloy catalyst such as PtPd supported on a nanofibre such as carbon or metal-oxide nanofibre and (D) core—shell catalyst such as Au Pt supported on conductive nanotubings such as carbon nanotubings. (For color version of this figure, the reader is referred to the online version of this book.)...

Kohbnuller H (1977) Anodic-oxidation of ethylene-glycol with noble-metal alloy catalysts. J Power Sources l(3) 249-256... 

Antolini E, Salgado JRC, Gonzalez ER (2006) The stability of Pt-M (M = first row transition metal) alloy catalysts and its effect on the activity in low temperature fuel cells a literature review and tests on a Pt-Co catalyst. J Power Sources 160(2) 957-968... 

It has been shown that the current exchange density increases up to 70°C, but there is no data for this above 100°C, again there is a critical need to measure this under real fuel cell conditions. Much work is being undertaken in precious metal alloy catalysts where Pt is combined with one or more other metals and in nonprecious metal catalysts [77]. These new catalytic materials are being studied in aqueous acid or in ME As at 100% RH, very little data exists on how these materials will behave under hot and dry conditions. In fact the development of new catalyst for fuel cells run under hot and dry conditions may require there optimization outside of aqueous or water-saturated systems. 

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