A newly developed method is presented which allows the characterization of the electrocatalytic properties of highly dispersed electrocatalysts in a true rotating disk electrode (RDE) configuration by attaching the catalyst powder on a glassy carbon electrode via a thin Nafion film. Complete utilization and high reproducibility of both the electrode preparation and the catalyst loading could be shown via voltammetry and CO stripping voltammetry. Furthermore, RDE mneasurements on the electro-oxidation of hydrogen on Pt/Vulcan showed that the effect of diffusion through the Nafion film can be avoided by proper electrode preparation. Therefore, the electrode kinetics for fuel cell relevant reactions under continuous flow conditions can be measured directly without mathematical modeling.

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CommunicationsPseudomorphic monolayers can be formed on single-crystal substrates by the deposition of palladium. Depending on the lattice parameters of the substrate, the palladium monolayer is compressed or dilated, effects which alter its properties, for example, the adsorption of hydrogen or the electrooxidation of formic acid. The changes in these properties can be studied electrochemically. For more information see the Communication by L. A. Kibler et al. on the following pages.

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The oxidation of formic acid on thin, epitaxially-grown Pd overlayers on Au and Pt single crystal electrodes was studied as a function of overlayer thickness ranging from submonolayer coverages up to the equivalent of 10 monolayers. The results were compared with those for massive Pd single crystal surfaces. The electrocatalytic properties of the Pd overlayers were found to depend markedly on their thickness and on their crystallographic orientation. Pd(100) showed the highest catalytic activity of all three low-index faces, and Pd films on Pt(hkl), even when two or three layers thick, generally exhibited a much higher activity than Pd films on Au(hkl) or massive Pd(hkl). In all cases a high resistivity of the Pd surfaces against poisoning by CO was observed, which makes Pd an interesting alternative to the often quickly deactivated Pt as catalyst for organic fuel cell reactions.

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