Unravelling the hydrogen absorption process in Pd overlayers on a Au(111) surface

QUAINO, PAOLA M.; SANTOS, ELIZABETH; NAZMUTDINOV, RENAT; PEIRETTI, LEONARDO FEDERICO

PHYSICAL CHEMISTRY CHEMICAL PHYSICS

ROYAL SOC CHEMISTRY

Lugar: CAMBRIDGE; Año: 2016 vol. 18 p. 3659 - 3668

1463-9076

The hydrogen absorption into overlayers of Pd deposited on Au(111) has been investigated by densityfunctional theory (DFT). Hydrogen concentrations, absorption environments, and geometrical andelectronic effects have been analyzed, seeking for a better understanding of the general principlesgoverning the process and the effect of foreign supports. The results show that the absorption is morefavored than in pure Pd leading to lower absorption energies and less repulsive interactions due to thesurface expansion induced by the gold larger lattice constant. Our findings also suggest that thehydrogen absorption process is more favorable for a less number of Pd overlayers. This situationchanges gradually until the substrate influence is no longer detected and the pure palladium natureappears. An entangled combination of repulsive forces, strain effect, structural ordering and chemicalaffinity has been found. The kinetics of hydrogen absorption has been studied as well. Two cases wereexplored: (1) the absorption of an adsorbed hydrogen atom and (2) the bond-breaking and penetrationof a H2 molecule.