Microfaceting and thermodynamic stability of the surface under chemisorption conditions

The effect of the adsorption of simple molecules on the excess surface energy of a pure metal surface is evaluated. Even analysis in the framework of simple ideal models of adsorption demonstrates that thermodynamic driving forces resulting from chemisorption can cause surface reconstruction with the formation of microfacets. The validity of this approach for description of real adsorption processes, especially at high adsorbate coverages, is confirmed by the fact that the minimum standard enthalpy of adsorption at which metal surface can lose thermodynamic stability, (Δ H°ads)cr, is similar to the typical experimental data available on the heat of chemisorption of reactive molecules (CO, H2, and O2) on the surface of transition metals (Ag, Pt, Ni, Pd, and Fe).