RESUMEN
Hydrogen evolution on single-crystal copper and silver is investigated by a combination of density functional theory and a theory developed in our own group. At short times, the reaction rate is determined by the transfer of the first proton to the electrode surface. In accord with experiment, we find for both metals that this reaction proceeds faster on the (111) surfaces than on the (100) ones. The main cause is the lower, that is, more favourable, adsorption energy on the former surfaces. On both silver surfaces, the second step is electrochemical desorption. The same mechanism is likely to operate on copper.
Asunto(s)
Simulación por Computador , Cobre/química , Hidrógeno/química , Modelos Químicos , Plata/química , Cristalización , Propiedades de SuperficieRESUMEN
We used density functional theory to detail new self-diffusion mechanisms on perfect and imperfect Au(100) surfaces. Herein, we report binding energies of stable intermediates and transition states lying on the potential energy surface for these systems. We report migration pathways in the presence of a variety of surface defects and along different step edges, explaining their energetics in terms of chemical bonding. Furthermore, diffusion rate constants are deduced, which are useful for both experimental verification and for implementation into large-scale kinetic Monte Carlo simulations.
RESUMEN
A recently developed model for electrocatalysis is combined with results of quantum chemical calculations to investigate the effect of the electrode's electronic structure on the rate of the hydrogen oxidation reaction. Model calculations have been performed for three metals with widely differing properties: Cd(0001), Au(111) and Pt(111). In line with experimental findings, the energy of activation decreases in this order. These results are explained in terms of the interaction of the bonding orbital of the hydrogen molecule with the d band of the electrode as it passes the Fermi level.