Water-Gas Shift Activity of Atomically Dispersed Cationic Platinum versus Metallic Platinum Clusters on Titania Supports

Atomically dispersed supported metal catalysts offer unique opportunities for designing highly selective catalysts and maximizing the utility of precious metals that have potential applications in a wide variety of industrial chemical reactions. Although substantial advances in understanding the origin of the activity of such highly dispersed metal catalysts have been made for a few chemical reactions, the reaction mechanisms and the nature of the active site small metal clusters versus single atoms are still highly debated. Using a combination of density functional theory and microkinetic modeling, we confirm that a positively charged single Pt atom on TiO2(110) can exhibit a very high low-temperature activity for the water-gas shift reaction (TOF > 0.1 s(-1) at 473 K). A comparison of these results with our work on Ti02 supported Pt cluster models provides clear evidence that different active sites are responsible for the experimentally observed activity at low and high temperatures. Finally, we explain why contradictory experimental conclusions have been reported.