Adsorption and Absorption Energies of Hydrogen with Palladium

[Image: see text] Thermal recombinative desorption rates of HD on Pd(111) and Pd(332) are reported from transient kinetic experiments performed between 523 and 1023 K. A detailed kinetic model accurately describes the competition between recombination of surface-adsorbed hydrogen and deuterium atoms and their diffusion into the bulk. By fitting the model to observed rates, we derive the dissociative adsorption energies (E(0, ads)(H(2)) = 0.98 eV; E(0, ads)(D(2)) = 1.00 eV; E(0, ads)(HD) = 0.99 eV) as well as the classical dissociative binding energy ϵ(ads) = 1.02 ± 0.03 eV, which provides a benchmark for electronic structure theory. In a similar way, we obtain the classical energy required to move an H or D atom from the surface to the bulk (ϵ(sb) = 0.46 ± 0.01 eV) and the isotope specific energies, E(0, sb)(H) = 0.41 eV and E(0, sb)(D) = 0.43 eV. Detailed insights into the process of transient bulk diffusion are obtained from kinetic Monte Carlo simulations.