Hydrogen electrocatalysis on overlayers of rhodium over gold and palladium substrates--more active than platinum?

ABSTRACT

We have investigated the stability and catalytic activity of epitaxial overlayers of rhodium on Au(111) and Pd(111). Both surfaces show a strong affinity for hydrogen. We have calculated the energy of adsorption both for a strongly and a more weakly adsorbed species; the latter is the intermediate in the hydrogen evolution reaction. Both the energy of activation for hydrogen adsorption (Volmer reaction) and hydrogen recombination (Tafel reaction) are very low, suggesting that these overlayers are excellent catalysts.