Impurity and support effects on surface composition and CO plus NO reactions over Pt-Rh/CeO2 nanoparticles:: A comparative study

A Monte Carlo simulation technique has been used to investigate the effect of sulphur impurity and ceria support on the surface composition and catalytic activity of Pt-Rh/ceria nanocatalysts. For temperatures in the range of 400-1300 K the surface Pt concentration decreases with increase in sulphur coverage. The Pt concentration at the base of the nanocatalyst in contact with the support increases with metal-support interaction. However, for weak metal-support interaction (V-ms < -0.01 eV) the surface Pt concentration slightly increases with metal-support interaction. Overall, sulphur is found to influence the surface composition much more strongly than the metal-support interaction. The MC-simulated surface composition results have been used to study the energetics of the CO + NO reactions over Pt-Rh/CeO2 catalysts. It is found that the CO2 formation rate decreases with increase in sulphur coverage and marginally increases with metal-support interaction up to V-ms = -0.01 eV. All the results qualitatively agree with the experimental results.