Methanol Oxidation as a Diagnostic for OH Adsorption on Pt

The methanol oxidation reaction is known to depend on surface hydroxyl species, yet direct identification of OH adsorption typically requires spectroscopic techniques. Here, we demonstrate that the MOR can serve as a direct, rapid, and spectroscopy-free diagnostic for detecting OH adsorption on Pt. By examining the initial voltammetric cycles across Pt single-crystal surfaces spanning the entire stereographic triangle, we show that low-potential OH adsorption is a universal property of low-coordination Pt sites, occurring regardless of step geometry or terrace width, and enabling early methanol dehydrogenation to CO. The MOR also provides a structural readout: the position and intensity of the dehydrogenation features shift systematically with step geometry and step density, reflecting changes in kinetic accessibility associated with local coordination, without altering the fundamental ability of these sites to stabilize OH. Thus, the MOR response reveals both the presence of OH and structure-dependent differences in methanol activation. By reframing the MOR as a diagnostic probe, rather than solely as a catalytic reaction, this work elucidates the mechanistic interplay between local coordination, OH adsorption, and methanol dehydrogenation, providing a practical route for assessing reactive surface motifs and for guiding the design of Pt-based electrocatalysts.