Analysis of the OH coverage on low-coordinated Pt sites at low potentials

In a previous study, we demonstrated the presence of OH species adsorbed on low-coordinated Pt sites (or steps) at low potentials using spectroscopy and electrochemical experiments. This investigation was specifically conducted on a Pt(311) surface in an electrolyte with pH=1. In this work, we extend our study to other surfaces featuring (111) terraces but varying in step geometry and step density. Additionally, we explored the influence of pH on these systems. Our findings reveal that the OH coverage on Pt steps at low potentials is independent of pH but sensitive to surface structure. Specifically, we observed an OH coverage of 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 and is predominantly influenced by adsorbed species on these low-coordinated sites.