Comparison of reactivity on step and terrace sites of Pd (3 3 2) surface for the dissociative adsorption of hydrogen: A quantum chemical molecular dynamics study

• Published in: Applied surface science Vol. 257; no. 24; pp. 10503 - 10513
• Main Authors: Ahmed, Farouq, Nagumo, Ryo, Miura, Ryuji, Ai, Suzuki, Tsuboi, Hideyuki, Hatakeyama, Nozomu, Endou, Akira, Takaba, Hiromitsu, Kubo, Momoji, Miyamoto, Akira
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier B.V 01.10.2011; Elsevier
• Subjects: Adsorption; Condensed matter: electronic structure, electrical, magnetic, and optical properties; Condensed matter: structure, mechanical and thermal properties; Cross-disciplinary physics: materials science; rheology; Diffusion; Dissociation; Exact sciences and technology; Mathematical models; Molecular dynamics; Palladium; Physics; Quantum chemical molecular dynamics method; Quantum chemistry; Surface chemistry; Surface defects; Terraces; Dissociation; Adsorption; Surface defects; Quantum chemical molecular dynamics method; Terrace; method; Surface defect; Hydrogen; Molecular dynamics method; Quantum chemical molecular dynamics; Step
• ISSN: 0169-4332; 1873-5584
• DOI: 10.1016/j.apsusc.2011.07.028

[Display omitted] ► The exact nature of the active sites hence the mechanism by which they act, are still largely a matter of speculation. ► We have presented QCMD calculations for the interaction of H 2 on different step and terrace sites of the Pd (3 3 2) surface. ► Saturated step sites can dissociate H 2 moderately and that a monovacancy surface is suitable for significant dissociation. ► However in terrace site dissociation of H 2 takes place only on Pd sites where the metal atom is not bound to any pre-adsorbed H atom. ► We identify a number of consequences for the interpretation and modeling of diffusion experiments demonstrating the coverage. The notion of “active sites” is fundamental to heterogeneous catalysis. However, the exact nature of the active sites, and hence the mechanism by which they act, are still largely a matter of speculation. In this study, we have presented a systematic quantum chemical molecular dynamics (QCMD) calculations for the interaction of hydrogen on different step and terrace sites of the Pd (3 3 2) surface. Finally the dissociative adsorption of hydrogen on step and terrace as well as the influence of surface hydrogen vacancy for the dissociative adsorption of hydrogen has been investigated through QCMD. This is a state-of-the-art method for calculating the interaction of atoms and molecules with metal surfaces. It is found that fully hydrogen covered (saturated) step sites can dissociate hydrogen moderately and that a monovacancy surface is suitable for significant dissociative adsorption of hydrogen. However in terrace site of the surface we have found that dissociation of hydrogen takes place only on Pd sites where the metal atom is not bound to any pre-adsorbed hydrogen atoms. Furthermore, from the molecular dynamics and electronic structure calculations, we identify a number of consequences for the interpretation and modeling of diffusion experiments demonstrating the coverage and directional dependence of atomic hydrogen diffusion on stepped palladium surface.