Electrochemical behaviour of pseudomorphic overlayers: Pd on Au(111)

The electrochemical properties of palladium adlayers on Au(1 1 1) are compared with those of massive Pd(1 1 1). Electrodeposited Pd forms a pseudomorphic overlayer on the unreconstructed Au(1 1 1) surface following the stacking sequence of the substrate. The altered electrochemical behaviour of the overlayer can be ascribed to changes in the electronic structure due to lateral strain. A gradual change to bulk properties is observed with increasing Pd coverage. Besides hydrogen adsorption, sulphate adsorption and surface oxidation, formic acid oxidation was chosen as a test reaction. The influence of lateral strain on the reaction kinetics of formic acid oxidation is discussed. (C) 2003 Elsevier Science B.V. All rights reserved.