Step-edge decoration and clustering of Pt atoms on a Cu(211) stepped surface

Abstract

The atomic manipulation of the low-coordination sites of metal catalysts can give rise to activity enhancement;however, it is rather challenging to locally probe the dynamic changes and activities of these sites. Herein, step-edge/terrace site decoration and site exchange of Pt atoms with a stepped Cu(211) surface were investigated by a combination of infrared reflection absorption spectroscopy (IRRAS) and temperature-programmed desorption (TPD) of carbon monoxide (CO). For a low coverage of Pt, step decoration and site exchange with Cu were found to be two pathways to isolate Pt as single atoms. CO preferentially adsorbs near the Cu step sites on the lower terrace, and the binding energies of CO show strong Pt coverage dependence. The presence of Pt on terrace and step sites modifies the binding energy of CO absorbed on Cu in the proximity. Increased Pt-Pt lateral coordination changes the site preference;however, the reduced binding energy of CO to Pt is attributed to heteroatom bond formation rather than the strain induced by the lattice mismatch.