Theoretical Simulation of the Binding Energies and Stretching Frequencies of CO Molecules on PtSn Bimetallic Nanoparticles

Abstract

The adsorption of CO molecules by Pt and Pt–Sn nanoparticles is studied using ab initio calculations. The Pt–C and C–O bond lengths, adsorption energies, and stretching frequencies of adsorbed molecules on the surface of nanoparticles at different sites are calculated. The calculated values are in good agreement with the experimental data. The segregation of bimetallic nanoparticles is also observed. The configuration of a nanoparticle in which platinum atoms are in the nucleus and tin atoms are on the surface is found to be energetically most favorable. The effect of Sn atoms near Pt on the density of electronic states of platinum and the stretching frequency of adsorbed CO molecules is also studied. Tin in the first coordination sphere is found to decrease the CO stretching frequency. The results obtained will allow quantitative interpretation of the infrared spectra of bimetallic nanoparticles during the catalytic reaction to analyze the surface morphology. The constructed adsorption energy maps will make it possible to predict the occupancy of nonequivalent adsorption sites at different temperatures and gas pressures.