Surface Structure and Anion Effects on Electrooxidation of Isopropanol on Pt(hkl)

This study focuses on the electro-oxidation of isopropanol on low-index platinum single-crystal surfaces─Pt(111), Pt(110), and Pt(100)─in acidic electrolytes containing either sulfuric acid (H₂SO₄) or perchloric acid (HClO₄). The aim is to elucidate the roles of crystallographic orientation and electrolyte anions in the reaction pathway and associated dynamic instabilities. While conventional voltammetric and spectroscopic techniques provide insights into reaction products and adsorbed intermediates, galvanostatic experiments are employed here to probe the emergence of potential oscillations, which serve as sensitive indicators of nonsteady-state surface processes. The results reveal a marked dependence of oscillatory behavior on both the electrode surface structure and the electrolyte composition. Pt(111) exhibits no oscillations under any of the tested conditions, consistent with a direct oxidation pathway that predominantly yields acetone and results in negligible accumulation of strongly adsorbed intermediates. Pt(110) displays limited and transient oscillations only in perchloric acid, suggesting a minor role for adsorbed poisoning species under these conditions. In contrast, Pt(100) shows robust and sustained potential oscillations across a wide range of current densities in both electrolytes, indicating a mechanistic regime dominated by the indirect pathway involving the formation and oxidation of adsorbed CO (CO_ads). Moreover, the low sensitivity of oscillations on Pt(100) to the nature of the electrolyte anion suggests that the dynamics of CO_ads buildup and removal are primarily dictated by the surface atomic arrangement rather than by competitive anion adsorption. These findings also underscore the utility of galvanostatic potential oscillations as a powerful diagnostic tool for detecting adsorbed intermediates that may remain elusive under steady-state conditions.