Methanol dehydrogenation, role

In this chapter, we provide a succinct review of some of the advances in the development and application of ab initio methods toward understanding the intrinsic reactivity of the metal and the influence of the reactive site and its environment. We draw predominantly from some of our own recent efforts. More specifically we describe (a) the chemistry of the aqueous-phase on transition metal surfaces and its influence on the kinetics and thermodynamics within example reaction mechanisms, and (b) computational models of the electrode interface that are able to account for a referenced and tunable surface potential and the role of the surface potential in controlling electro-catalytic reactions. These properties are discussed in detail for an example reaction of importance to fuel cell electrocatalysis methanol dehydrogenation over platinum(ll 1) interfaces [24,25]. 

The concentration of acid should affect interfacial reactions in various ways such as through the hydrogen ion concentration, water activity, and behavior of anions. Hydrogen ion concentration may play a minor role because the dehydrogenation can be considered as relatively fast steps in the methanol oxidation. Therefore, the other two elements will be considered here. 

Oxidative dehydrogenation reactions of alcohols and amines are widespread in enzymatic biochemistry, and are of potential importance with regard to the operation of fuel cells based on simple alcohols such as methanol. The nature of products, and their rates of formation, may vary depending on the reaction conditions, and a role of metal ions has been recognized. The oxidation of amines may lead to a variety of products (nitriles, nitro species, etc.) although dehydrogenated diimine products are obtained quantitatively when the oxidation of the amine occurs via coordination to metal centers. A review is available on the mechanisms of oxidative dehydrogenations of coordinated amines and alcohols (93). 

Literature data discussed above indicate that in the alkylation of a primary amine with an alcohol over a copper-containing catalyst the first and ratedetermining step of the reaction is the dehydrogenation of the alcohol. However, the nature and the oxidation state of the active site, i.e. Cu or Cu" is still debated, although more and more data indicate that ionic copper species may play an important role in the dehydrogenation of methanol. ... 

As shown by Figure 4.3, in addition to CH3OH dehydrogenation, the role of H2O chemisorption and OHad formation are erucial for efficient methanol oxidation. Thus,... 

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