The stability and electronic properties of Pt-modified Cu(1 1 0) and Cu(1 1 1) in the absence/presence of small molecules: a density-functional theory modeling.

Pt-Cu bimetallic alloys, as a key component in many heterogeneous catalysts, have the potential to be used in a range of industrially important reactions. The stability of platinum-modified Cu(1 1 0) and Cu(1 1 1) surfaces in the absence/presence of CO, NO and O has been investigated based on density-functional theory. We find that Pt alloyed in the second layer of the Cu (1 1 0) surface, rather than in the bulk, is the most favorable configuration. To relieve the strain, platinum tends to stay in the surface layer of close-packed Cu(1 1 1). Adsorbates can affect the stability of Pt-modified surfaces. Upon the adsorption of CO and NO, Pt segregation to the (1 1 0) surface becomes favorable, while on oxygen adsorption, no segregation occurs. Platinum only prefers to segregate on the Cu (1 1 1) surface when it is exposed to carbon monoxide, it tends to locate in the second layer for the other two adsorbates. Combining the position of d-band center, the d-bandwidth, and the separation between the bonding and antibonding states of the adsorbates, we interpret the results and correlate the relationship between the electronic properties of the substrate and the adsorption energy of the adsorbates, which could shed light on the prediction of bimetallic structures with desirable chemical properties.