Study of proton adsorption at heterogeneous oxide/electrolyte interface. Prediction of the surface potential using Monte Carlo simulations and 1-pK approach.

Adsorption of protons on a heterogeneous solid surface is modeled using the Monte Carlo (MC) simulation method. The surface of an oxide is assumed to consist of adsorption sites with pK assigned according to a quasi-Gaussian distribution. The influence of the electrostatic interactions combined with the energetic heterogeneity of the surface is examined and the MC results are compared with the predictions of the analytical 1-pK approach. The surface potential behavior is examined using both "experimental" MC results and "theoretical" results obtained from the application of 1-pK model. The results are compared qualitatively with experimental determination of the surface potential of metal oxide surfaces. They confirm that the relation between the surface potential and the pH of bulk solution should not be described by the Nernst equation but by the equation with the parameter linearly reducing Nerstian potential. The values of this parameter are examined with respect to degree of surface energetic heterogeneity and site density of the surface. Copyright 2004 Wiley Periodicals, Inc. J Comput Chem 25: 704-711, 2004