Electrified Interfaces of Pt(332) and Pt(997) in Acid Containing CO and KI: As Probed by in Situ Scanning Tunneling Microscopy

The role of step defects on an electrode is a central issue in the modern study of electrocatalysis. Although scanning tunneling microscopy (STM) has been used to characterize the electrified interfaces of low Miller-indexed single-crystal electrodes, there has been little progress in the STM study of stepped Pt electrodes. Herein, the structures of Pt(332) and Pt(997), two vicinal surfaces to the (111) plane, are examined by high-resolution STM under potential control in 0.5 M H2SO4 solution containing iodide or carbon monoxide. These electrodes are annealed by a hydrogen flame and quenched in Millipore water, giving rise to rough step edges with poorly defined atomic structures at 0.1 V (vs reversible hydrogen electrode) in 0.5 M H2SO4. However, step edges are sharpened and aligned in the ⟨110⟩ direction after adsorption of CO on both electrodes. In contrast, seesaw-like step lines are produced by iodine adsorption. Therefore, the step structure and mobility of Pt atoms are markedly influenced by the ad...