| AVS 66th International Symposium & Exhibition | |
| Surface Science Division | Tuesday Sessions |
| Session SS-TuP |
| Session: | Surface Science Poster Session |
| Presenter: | Richard van Lent, Leiden University, Netherlands |
| Authors: | R. van Lent, Leiden University, Netherlands L.B.F. Juurlink, Leiden University, Netherlands |
| Correspondent: | Click to Email |
The simplest heterogeneously catalyzed reaction possible is isotopic scrambling of hydrogen:
H2 + D2 --> 2 HD
On Pt, this reaction occurs by dissociative adsorption of H2 and D2, mixing of H and D atoms on the surface, and recombination to form the three isotopologues, H2, D2, and HD. Full isotopic scrambling would lead to a product ratio of 1:1:2.
Step edges are well-known to enhance dissociative adsorption, especially at low impact energies. However, it is unknown whether subsequent diffusion and desorption only occur along the steps or involves diffusion onto terraces. We study this by combining supersonic molecular beam techniques with a curved Pt single crystal surface with straight A and B type step edges, c-Pt(111)[1-10]310. At a high surface temperature, we probe HD formation, spatially resolved, along the curved surface by impinging a 50:50 mixture of low energy H2 and D2. HD formation tracks the trend in dissociation: higher step densities yield higher HD formation. However, relatively, HD formation does not increase as rapidly as the dissociation probability. We explain why the (111) terraces are more selective toward HD formation and show that anisotropic diffusion affects isotopic scrambling.