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,E- ads (H)(2) = 0.98 eV; E-0, ads (2)D = 1.00 eV; E-0,ads(HD)= 0.99 eV) as well as the classical dissociative binding energy ?(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 (?(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) were investigated, and a detailed kinetic model accurately describes the competition between recombination and diffusion processes. The obtained energy parameters provide insights into the adsorption and diffusion behaviors of hydrogen and deuterium on Pd surfaces.