Electro-oxidation of Various Oxygenated

The electro-oxidation characteristics of formaldehyde has been investigated by Lamy and coworkers ° and was studied due to its simple structure and the fact that it can serve as a model for understanding into the nature of oxidation of larger organic species. The group reported that the implementation of experimental methods are complicated by the fact that thef system involves an equilibrium between formaldehyde and methylene glycol, which is the main species in aqueous solutions. It was determined that the anodic oxidation of formaldehyde Is accompanied by the formation of strongly adsorbed species which have been identified as adsorbed CO by in-situ IR spectroscopy In alkaline - and acidic media.  

Being a one-carbon organic molecule, formic acid has also drawn attention as a potential fuel for fuel cell related applications. When considered in acidic media, the oxidation of formic acid proceeds according to the following reaction. 

Along with Pt, rhodium and palladium have been identified to have good activity for the electro-oxidation of formic acld. Parsons and Vandernoot have proposed a general scheme for the electro-oxidation of formic acid on R which involves a duel-path mechanism. The reactive adsorbed intermediate species 

It has been observed that the rate of electrocatalytic oxidation of formic acid at R electrodes can be enhanced significantly by the incorporation of adatoms, such as Pb, Bi, Tl, and Cd. The most significant enhancement has been seen with Pb adatoms, which were shown to be accompanied by a dramatic decrease in the poisoning phenomena on R. ° A similar type of behavior has been observed with systems based on Pt/Cdg, Pt/TI and Pt/Biads, although to a lesser extent. One of the most plausible explanations given rationalizing the improved characteristics of electro-oxidation in the presence of adatoms was proposed by Shibata and Motoo ° who invoke a 

The likely adsorbate species involved in the oxidation of the organic compounds has been summarized by Beden et al., who have considered the possible species from methanol to CO2. as illustrated in Fig. 1.4. 

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