Developing an understanding of structure-activity relationships and reaction mechanisms of catalytic processes is critical to the successful design of highly efficient catalysts. As a This is a previous version of the article published in

The dependence on temperature of the voltammetric behavior of Pt(111), Pt(100), and Pt(110) electrodes in 0.1 M HClO4 has been studied. A thermodynamic analysis of the hydrogen underpotential deposition (HUPD) has been carried out, taking into account that the adsorption process is accompanied by changes in the electrode double layer. The analysis for Pt(100) requires a previous deconvolution of the OH adsorption contribution whereas for Pt(110), the analysis is limited to high H coverages. The Pt−H bond energy values obtained for the Pt(hkl) electrodes agree with the values obtained in UHV. On Pt(111) and Pt(100), Δ (HUPD) changes linearly with coverage, with Frumkin repulsive parameters 27 and 9 kJ mol-1, respectively. The values obtained for Δ (HUPD) (−48 J mol-1 K-1 for Pt(111), − 56 J mol-1 K-1 for Pt(100), and from −55 to − 70 J mol-1 K-1 for Pt(110)) suggest immobile hydrogen adsorption. The fact that Δ (HUPD) depends significantly on the crystallographic orientation suggests that the symmetry of the platinum substrate strongly influences the degree of order in the water network directly bonded to the metal surface atoms.

A simple model for simulating the electrooxidation of HCOOH on single crystal surfaces of Pt catalyzed by adatoms is presented. The substrate is represented as a square or hexagonal array of lattice points, which may be occupied by adatoms or poisoning species. Analytic expressions for the oxidation current as a function of the adatom coverage are given. Third body effects as well as real improvement of the catalytic activity are analyzed. The model fits satisfactorily some experimental data for the electrooxidation of formic acid on Pt/adatoms systems.