Adsorption and Absorption Energies of Hydrogen with Palladium

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,E-ads (HD)= 0.99 eV) as well as the classical dissociative binding energy epsilon(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 (epsilon 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.

Automated summary

The thermal recombinative desorption rates of HD on Pd(111) and Pd(332) surfaces were studied through transient kinetic experiments. A detailed kinetic model accurately described the competition between the recombination of surface-adsorbed hydrogen and deuterium atoms and their diffusion into the bulk. The obtained results provide valuable information on the dissociative adsorption energies, binding energy, and the energy required for surface-to-bulk diffusion of H and D atoms.