Rotational and vibrational population ofD2desorbing from sulfur-covered Pd(100)

Ab Initio Molecular Dynamics Simulations of the Adsorption of H2 on Palladium Surfaces

“…[40,44,45] Still, it should be noted that there are large significant quantitative and qualitative differences as far as the sticking probability is concerned. The measured probabilities are much smaller than the calculated ones.…”

“…[8,9] Because of the presence of sulfur, H 2 dissociation on Pd is no longer non-activated. [8,9,40] Figure 5 shows a two-dimensional cut through the PES of H 2 interacting with S(22)/Pd(100) derived from PAW-DFT calculations. The minimum energy barrier towards dissociative adsorption is about 0.25 eV.…”

“…However, it should also be noted that experimentally the preparation of an ordered (2 2) sulfur overlayer on Pd(100) is not trivial. [8,40] It is often prepared by just heating up the Pd sample, leading to a segregation of the sulfur dissolved in the bulk Pd crystal to the surface. [8] Sulfur tends to form a c(22) overstructure on Pd(100) [40] corresponding to a higher sulfur coverage of V S = 0.5.…”

“…In order to study the dynamical consequences of the sulfurpoisoning on the hydrogen adsorption dynamics, six-dimensional quantum and classical dynamical studies were performed [40,44,45] on a parameterization of previous DFT calculations. [43,86] Figure 6 shows the calculated classical sticking probabilities as a function of the initial kinetic energies for initially non-rotating and non-vibrating molecules which are denoted by MD in the legends.…”

“…However, not only the coverage of the considered adsorbents itself can influence the adsorption probability, but also the coadsorption of other species can poison or promote reactions on surfaces. On Pd, in particular the influence of sulfur on the hydrogen-Pd interaction dynamics was studied both experimentally [8,9,39,40] as well as theoretically, [40][41][42][43][44][45] but CO coadsorption was also considered. [46] The H 2 -Pd dynamics on low-index metal surfaces has usually been treated quantum mechanically because of the light mass of hydrogen, [2,11,12,16,[47][48][49] but classical dynamical studies have also been performed.…”