Visualizing the step bunching on Pt surfaces and its effect in electrocatalysis with EC-STM

In a recent issue of Nature Catalysis, Rost et al. directly visualized the step bunching on flame-annealed Pt(111)-vicinal surfaces at high step densities using in situ electrochemical scanning tunneling microscopy (EC-STM). This phenomenon originates from the increased step-step repulsive interaction between closely distanced steps, and the surface-free energy will be lowered when forming bunched steps with wider terraces. This work challenges the common assumption that all stepped surfaces present homogeneously spaced steps of monoatomic height and provides a convincing explanation at atomic level for the anomalous electrochemical behavior of the platinum surface at high step densities, including the activity and potential of zero total charge.