By employing the in-situ electrochemical video-rate scanning tunneling microscopy (STM) at well-defined single crystal electrodes, we are going to study the surface dynamics of the atoms on Pt(111), Pt(553), Pt(533), Pt(111)-Cu and Cu/Pt(111) surface alloy in the absence and presence of oxygen gas, with the aim to probe and understand the restructuring of Pt and Pt alloy catalyst of the fuel cell cathodes under the operation conditions. Simultaneously, in-situ electrochemical surface Raman spectroscopy will be used to identify the surface species and their interaction with electrodes, using a version employing shell-isolated nanoparticles that is suitable for single-crystal electrodes. On the basis of the observations of STM and Raman spectroscopy, theoretical calculations based on density functional theory (DFT) and Monte Carlo simulations will be carried out to understand the surface electronic structures and to mimic dynamical migrations of the surface atoms. This should yield deep insight into the essential dynamic properties and the impact on the restructuring of these electrocatalysts under operation conditions.