Analysis of temperature effects on hydrogen and OH adsorption on Pt(1 1 1), Pt(1 0 0) and Pt(1 1 0) by means of Gibbs thermodynamics

Gibbs thermodynamics in the presence of charge-transfer processes have been applied to characterize temperature effects on Pt(1 1 1), Pt(1 0 0) and Pt(1 1 0) electrodes in 0.1 M HClO4HClO4 solutions. The present analysis allows the evaluation of the entropy of formation of the interphase for the three platinum basal planes, which is found to be structure-sensitive. In addition, these results have been used to test the suitability of the more common approach to characterize temperature effects, based on the application of a generalized isotherm. Besides, the comparison of both approaches allows the characterization of the different components involved in the entropy of hydrogen and OH adsorption, namely, the standard entropy of adsorption, the entropy due to lateral interactions, and the configurational entropy. Finally, the comparison with statistical mechanical calculations demonstrates that adsorbed hydrogen on Pt(1 1 1) and Pt(1 0 0) is rather mobile, while adsorbed OH is rather immobile. Adsorbed hydrogen on Pt(1 1 0) exhibits an unexpected behavior, since it appears to be rather immobile at low coverages, but it becomes very mobile at near saturation coverages.