A Comparison of the Adsorption and Diffusion of Hydrogen on the 111 Surfaces of Ni, Pd, and Pt from Density Functional Theory Calculations

We present gradient corrected density function theory calculations on the adsorption and thermally activated diffusion pathways of hydrogen on the 111 surfaces of Ni, Pd, and Pt. We find that the variation of the adsorption energy as a function of adsorption site shows considerable differences between the three metals. For Ni and Pd, the adsorption energies vary as a function of hydrogen coordination with the 3-fold hollow sites the most stable and the 1-fold atop site considerably less stable. On Pt the adsorption energies for all the sites are similar indicating that diffusion across the surface will be faster on Pt than on Ni or Pd. The activation energies for diffusion have been calculated with that for Pt (2−3 kJ mol-1) considerably smaller than for Ni or Pd (13 kJ mol-1). The calculated adsorption and activation energies are in good agreement with experimental investigations of the structure, energetics, and diffusion properties.