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

Thermodynamic properties of hydrogen–water adsorption at terraces and steps of Pt(111) vicinal surface electrodes

“…This is a simple, but efficient, method to estimate metal/solution thermodynamic properties of adsorption processes at Pt single crystals, in good agreement with other more precise methods, like the analysis based on the electrocapillary equation [20,21].Despite several of its implicit approximations, such as the assumption of the separability of a Langmuirian configurational term from the adsorbate chemical potential, the charge number in the adsorption process is equal to the charge of the adsorbing species in solution and the calculation of species coverages by integration of voltammograms at different temperatures, arbitrarily double-layer charging corrected. The full derivation of the mathematical expressions in this scheme has been already described in detail, and so, only main equations will be given here [15,17,20,21].…”

“…Commonly, they have been attributed to Hads on step sites [11,12,14], because peak potentials are constant and charge densities linearly increase with step density, in good agreement with a process where one electron is exchanged per step atom [11][12][13][14]. However, because of their unusual pHdependent shift of 50 mV NHE/pH unit [22,33], and their sharp shape, which can be only modeled by assuming net attractive interactions between adsorbed species [30] in contrast to repulsive Hads lateral interactions on {111} terraces [15,17,20,24], it has been recently also suggested that these peaks at 0.13V and 0.28 V could be caused by competitive co-adsorption of OHads, or even adsorbed oxygen, Oads, from water dissociation at steps, through a more complex reaction scheme [33]:…”

“…Later, works employing more precise methods to characterize the interface, like the analysis based on the electrocapillary equation [20,21,24], reported a good agreement with results from the generalized isotherm strategy [15,17].…”

“…Application of thermodynamic equilibrium conditions to these half-cell reactions [17,20], leads to the meanfield expression for the adsorption on two-dimensional terraces, also known as the generalized isotherm [4-6]:…”

“…Two different step sites can be distinguished: those with {100} geometry and those with {110} geometry. Therefore, the study of the influence of steps, with different orientation, upon the electrochemical reactivity has become a relevant area [11][12][13][14][15][16][17][18][19][20][21][22][23][24][25].However, the understanding at microscopic scale of phenomena underneath voltammetric profiles, the distinction among different processes that could contribute to the voltammetric features and their dependence on various experimental parameters, is still far from being complete, and more work is still necessary to fully understand these simple signatures. In this sense, temperature dependence analysis of voltammetric profiles provides unique information about the electrochemical interface.…”