Computational analysis of H/D isotope effect on adsorption of water and its dissociated species on Pt(111) surface

To understand the mechanism of the H-D exchange reaction for synthesizing various deuterium-labeled molecules on heterogeneous metal catalysts as a first step, we analyzed the effects of H/D isotopes on the adsorption of H2O/D2O and their dissociated OH/OD and H/D species on the Pt(111) surface. We applied the combined plane-wave and localized basis set method developed by us to directly treat the electronic structures of the surface and the localized adsorbed region and the nuclear quantum effect of H and D. The results showed that the adsorption energies for the D-compounds on the Pt surface were larger than those for the H-compounds. This is in keeping with the experimental observations. The difference in the distance between the adsorbates and the Pt surface induced by the H/D isotope effect depends on the bonding characteristics. While the distance between D2O and the Pt surface was longer than that in the H2O case, the distance between the D atom and the Pt surface was shorter than that for the H atom. This is the first report on the geometrical differences between H and D based on a systematic analysis of water and its dissociated species.