CO oxidation on Ru-Pt bimetallic nanoclusters supported on TiO(101): The effect of charge polarization.

Pt-based catalyst is widely used in CO oxidation, while its catalytic activity is often undermined because of the CO poisoning effect. Here, using density functional theory, we propose the use of a Ru-Pt bimetallic cluster supported on TiO for CO oxidation, to achieve both high activity and low CO poisoning effect. Excellent catalytic activity is obtained in a RuPt/TiO(101) system, which is ascribed to strong electric fields induced by charge polarization between one Ru atom and its neighboring Pt atoms. Because of its lower electronegativity, the Ru atom donates electrons to neighboring Pt. This induces strong electric fields around the top-layered Ru, substantially promoting the adsorption of O/CO + O and eliminating the CO poisoning effect. In addition, the charge polarization also drives the d-band center of the RuPt cluster to up-shift to the Fermi level. For surface O activation/CO oxidation, the strong electric field and d-band center close to the Fermi level can promote the adsorption of O and CO as well as reduce the reaction barrier of the rate-determining step. Meanwhile, since O easily dissociates on RuPt/TiO(101) resulting in unwanted oxidation of Ru and Pt, a CO-rich condition is necessary to protect the catalyst at high temperature.