Getting Insights into the Temperature-Specific Active Sites on Platinum Nanoparticles for CO Oxidation: A Combined in Situ Spectroscopic and ab Initio Density Functional Theory Study

Abstract

The geometrical structure of metal nanoparticles has been found to be a critical factor that can influence the catalytic behavior significantly. For typical metal nanoparticles, the exposed surface atoms usually exhibit different coordination environments among different surface sites. By in situ diffuse reflectance Fourier transform infrared spectroscopy, kinetic measurements, and DFT calculations, it has been found that, for Pt-catalyzed CO oxidation at different temperatures, CO reacts preferentially on different surface sites of Pt nanoparticles. At low temperatures, Pt species with higher coordination numbers (≥7-fold coordinated) present higher catalytic activities due to the lower CO adsorption energy. However, at high temperatures, especially beyond the ignition temperature, Pt species with lower coordination numbers (≤6-fold coordinated) play a predominant role because of their better capability for O activation.