Site-specific chemical states of adsorbed CO on Pt(997): A high resolution XPS study

► We investigated the adsorbed states of CO on Pt(997) using high-resolution XPS. ► We discriminated three C1s peaks of adsorbed CO and reacted Pt 4f7/2 components. ► We discuss the charge transfer between adsorbed CO and surface Pt atoms. ► Step-CO species electronically interact with both step and terrace Pt atoms.