Dynamics of scattering and dissociative adsorption on a surface alloy: H2/W(100)-c(2 × 2)Cu

• Published in: Physical chemistry chemical physics : PCCP Vol. 13; no. 1; pp. 4614 - 4624
• Main Authors: Batista, M. N, Busnengo, H. F, Martínez, A. E
• Format: Journal Article
• Language: English
• Published: Cambridge Royal Society of Chemistry 14.03.2011
• Subjects: Adsorption; Chemistry; Copper; Dynamics; Energy of dissociation; Exact sciences and technology; General and physical chemistry; Reduction; Scattering; Surface chemistry; Surface physical chemistry; Trapping; Density of states; Experimental data; Alloys; Theoretical study; Reflection; Chemical reduction; Trapping; Adsorption; Energy; Dynamics; Density functional method; Angular distribution; Defect; Dissociation; Chemical reactivity
• ISSN: 1463-9076; 1463-9084
• DOI: 10.1039/c0cp02542a

H 2 scattering and dissociative adsorption on the W(100)- c (2 × 2)Cu surface alloy is studied based on DFT calculations. A strongly site dependent reactivity is observed in line with results obtained for the density of states projected onto the W and Cu atoms of the topmost layer. H 2 dissociation on a defect free terrace of W(100)- c (2 × 2)Cu is found to be a non-activated process like on W(100), despite the reduction of the number of energetically accessible dissociation pathways at low impact energies due to the presence of Cu atoms. A prominence of dynamic trapping and a reduction of the efficacy of trapping to promote dissociation is also verified, leading to a decrease of the initial sticking probability as a function of the molecular impact energy, in qualitative agreement with experimental findings. The heterogeneous reactivity is also evidenced by two different kinds of reflection events at low energies. Its combination gives rise to a broad specular peak superimposed on a cosine-like angular distribution of scattered molecules which is in good agreement with available experimental data. The W(100)- c (2 × 2)Cu surface alloy shows a strongly site dependent reactivity evidenced in two different kinds of reflection events: direct around top-Cu sites, and through a trapping-desorption mechanism near top-W sites.