Kinetics, energetics and structure of hydrogen adsorbed on transition metal single crystal surfaces

Some recent results on the interaction of hydrogen with low‐index planes of Ni, Ru, Pd and Pt are reported abs compared in order to gain more general and sight into elementary processes involved in heterogeneously catalyzed reactions with hydrogen or hydrocarbon as reactants. Starting off from a consideration of factors which govern the rate of the adsorption/desorption steps the energetics of the hydrogen chemisorption is discussed. The energy of the hydrogen‐metal bond as derived from both isosteric heat or thermal desorption measurements is discussed in terms of its absolute value and analysed with respect to its coverage dependence, thus reflecting both the strength of the metal‐adsorbate and the adsorbate‐adsorbate interaction. It is shown with the aid of some selected examples that ordering phenomena within hydrogen adsorbate layers may occur and can be readily detected by low‐energy electron diffraction. As a consequence, important information about the nature of the H‐H interaction on transition metal surfaces is obtained.