Analysis of the OH Coverage on Low-Coordinated Pt Sites at Low Potentials

In a previous study, the presence of OH species adsorbed on low-coordinated Pt sites (or steps) at low potentials (the so-called hydrogen adsorption region) using spectroscopy and electrochemical experiments was demonstrated. This investigation was specifically conducted on a Pt(311) surface in an electrolyte with pH = 1. In this work, the study is extended to other surfaces featuring (111) terraces but with varying step geometry and step density. Additionally, the influence of the pH on these systems was explored. Our findings reveal that the OH coverage on Pt steps at low potentials, measured just after the peak for the step, is independent of pH but sensitive to surface structure. Specifically, we have determined that OH coverage is approximately 0.5 on surfaces with (110) steps and 0.33 on surfaces with (100) steps. Furthermore, the potential of zero total charge aligns with the local potential of zero charge for the steps since it is predominantly influenced by adsorbed species on these low-coordinated sites.