Revisiting H/Pt(111) by a combined experimental study of the H-D exchange reaction and first-principles calculations

Abstract

We report a detailed investigation of the behavior of chemisorbed hydrogen atoms (Ha) on Pt(111) by a combination of an experimental study of the Ha + Da reaction and first-principles calculations. The coverage-dependent adsorption and desorption behavior of Ha and Da on Pt(111) have been systematically established and can be well interpreted in terms of repulsive interactions between adsorbates. Ha adsorbs exclusively on the face-centered cubic (fcc) sites of Pt(111) at coverages not exceeding 1 monolayer (ML). With increasing Ha coverage, repulsive interactions between Ha increase, leading to a reduction in both the adsorption energy and the desorption activation energy. It is proposed that the lateral interactions within a Ha layer are partly induced by the local repulsive interactions due to high mobility of Ha on Pt(111). For the Ha + Da exchange reaction on Pt(111), it is found that Ha has a higher selectivity for HD formation than Da. Considering that Ha diffuses much faster than Da on Pt(111), we propose that the difference in diffusion rates between Ha and Da may determine the selectivity of Ha and Da in forming HD in the Ha + Da reaction on Pt(111).