COPPER PALLADIUM ALLOY SURFACES .1. CU/PD[85-15](110), SURFACE-STRUCTURE AND REACTIVITY

Both ordered and disordered phases of Cu:Pd[85:15]{110} have been studied using low-energy electron diffraction (LEED), X-ray photoelectron spectroscopy (XPS), and ultraviolet photoelectron spectroscopy (UPS). Low-energy ion scattering (LEIS) has also been employed to study the ordered surface. In the case of the ordered phase, these techniques have been used to ascertain the structural and electronic influence of the Pd on this surface in comparison to that observed for Cu(110). In addition temperature-programmed desorption (TPD) has been employed to determine the chemical reactivity of this surface towards the decomposition of adsorbed formic acid (HCOOH) and C-deuterated formic acid (DCOOH).This is compared to the same reaction on Cu(110) and a kinetic isotope effect is noted in the decomposition of the two acids. Segregation of the Cu component of the alloy is observed upon the thermally induced transition from disordered to ordered surface phases, leaving the surface layer essentially free of Pd, while the second layer is enriched in Pd to approximately 50% composition.