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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A selection of recent theoretical and experimental studies on electrolytic hydrogen evolution is presented. It is demonstrated with well-defined model surfaces that this reaction is a very structure-sensitive process. Crystallographic orientation, defect density and surface composition are parameters that determine the local geometric and electronic surface structure, and are thus crucial for the electrocatalytic activity as characterised by the exchange current density. The observed trends can be understood within a recent theory by J. K. Nørskov et al., which is based on density functional calculations and which emphasises the impact of hydrogen chemisorption energies on the reaction rate, that is, on the exchange current density. The particular electrocatalytic activities of ultrathin metal films and of nanostructures are addressed.

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