Interaction between H2O and Preadsorbed D on the Stepped Pt(553) Surface

We have studied the interaction of Pt(553) with varying coverages of preadsorbed D and H2O and compare results to those from the similar Pt(533) surface. We have used temperature programmed desorption spectroscopy in combination with isotopic labeling to monitor H–D exchange. Similar to results for Pt(533), on Pt(553) small amounts of D weaken the H2O–metal bonding at steps. Larger D coverages also weaken the stability of the water overlayer at the (111) terraces. However, in contrast to Pt(533), water wets the Pt(553) surface at all D-coverages and the surface does not become hydrophobic. We attribute the difference in the long-range ordering of water to the difference in bond energy of deuterium to (100) and (110) step sites. This also affects HOD formation by H–D exchange. The exchange increases with H2O and Dad coverage, although less than proportional. Availability of bare Pt sites for both adsorbates is key to obtaining high reactivity.