On the Electronic Structure of Palladium—Hydrogen and Platinum—Hydrogen Systems

Abstract

a), and V. HEERA (c)The interaction of hydrogen with palladium and platinum is studied on the basis of cluster calculations using the SW-Xa method in a semirelativistic variant. Energy level spectra, density-ofstates curves, and charge distributions arc represented and discussed w t h respect to other theoretical and experimental investigations. The dominant role of covalent bond between hydrogon and palladium/platinum is illustrated. The results of the calculations show that for a heavy element as platinum relativistic effects can influence the bonding between atoms in a qualitative way. The less stability of the hydrogen-platinum Bystemcompared with the Pd-H systemis explained as a relativistic effect. Die Wechselwjrkung von Wasserstoff mit Pallndium und Platin wird auf der Grundlage v mCluster-Rechnungen mit der SW-Xa-Methode in einer scmirelativistischen Variante untersucht. Die Energicniveauschemata, Zustandedichtekurven und Ladungsdichteverteilungen werden dargestellt und hinsichtlich anderer theoretischcr und cxperimenteller Untersuehungen diskutiert. Die dominicrcnde Rolle der kovalentcn Bindung zwischen Wasserstoff und Palladium/Platin wird illustriert. Die Ergebnisse der Berechnungen zcigen, da13 fiir ein schweres Element wie Platin die relativistischen Effekte die Bindung zwischen Atomen in qualitativer Weise beeinflussen konncn. Die geringero Stabilitat des Platin-Wasscrstoff-Systemsverglichen mit dem Pd-H-Systemwird als ein relativistischer Effckt erkliirt. ~-I) Mommsenstr. 13, DDR-8027 Dresden, GDR. 2, Am Steiger 3, DDR-6900 Jenct, GDR.

Hydrogen Adsorption on Au-Supported Pt and Pd Nanoislands: A Computational Study of Hydrogen Coverage Effects

“…At low hydrogen coverages θ H ads < 0.63 ML, hydrogen is located on the bridge sites at the steps of Pt 19 (Figure b) but on hollow sites on the terrace of Pd 19 (Figure g). As we discussed in previous works, , the preference for low-coordination and high-coordination sites for hydrogen on Pt and Pd, respectively, is the result of relativistic contraction and stabilization of the valence s orbitals of Pt atoms . The metal-H bonding is mainly mediated by s–s bonding for hydrogen at the 3-fold hollow site, , turning to be sensitive to the stabilization of s orbitals in the metal.…”

Hydrogen adsorption on and spillover from Au- and Cu-supported Pt3 and Pd3 clusters: a density functional study

“…The difference between on top and three-fold hollow sites on Pt 3 and Pd 3 arises from a relativistic effect that contracts and stabilizes the valence s orbital of Pt atoms. 57,58 Such stabilization leads to a low M 3 -H interaction energy if the latter is predominantly due to the hybridization of the H 1s orbital (s H ) and the M 3 valence s orbitals (s M ) and a concomitant occupation of the s H -s M antibonding level. Hydrogen at a three-fold hollow site is very sensitive to the stabilization of s M orbitals as M 3 -H bonding is mainly mediated by s H -s M .…”

“…Hydrogen at a three-fold hollow site is very sensitive to the stabilization of s M orbitals as M 3 -H bonding is mainly mediated by s H -s M . [57][58][59] In contrast, hydrogen on top is rather insensitive because in that case the M 3 -H bond derives from the interaction of s H with the d z 2 orbitals of M 3 . 56 Hence, on Pt 3 hydrogen prefers low coordination and short M-H bonds, Pt-H = 1.52 A ˚, while on Pd 3 hydrogen is more stable when highly coordinated, hPt-Hi = 1.79 A ˚.…”

Adsorption and diffusion of sulfur on the (111), (100), (110), and (211) surfaces of FCC metals: Density functional theory calculations

“…III B) because the transition states have a lower number of bonds than the initial state. 68 In the cases of the (110) and (211) surfaces of Ir, Pt, and Au, the relativistic effects present in these heavy atoms are likely influencing 69,70 the bonding with sulfur. Further detailed studies are required to better understand the adoption of sulfur on the (110) and (211) surfaces of Ir, Pt, and Au.…”