Charge Transfer Between Pt and Au Nanoparticles Over ZnO for CO Oxidation
Abouelhassan A. Gomaa, Na Ta, Wenjie ShenABSTRACT
Oxide‐supported Au nanoparticles exhibit promising activity for the low‐temperature oxidation of CO owing to the weak adsorption of CO on Au, in contrast to Pt nanoparticles that suffer from CO poisoning on Pt. Here, we investigated the effect of Pt on the activity of Au/ZnO for CO oxidation by depositing preformed 2.0 nm Au and 4.4 nm Pt particles on ZnO. It was found that the reaction rate declined as Pt was added to Au/ZnO. Microscopic and spectroscopic characterizations revealed that charge transfer from Au to Pt via ZnO induced the formation of positively‐charged gold species and simultaneously the enrichment of electron density on Pt. The formation of positively‐charged gold weakened CO activation during CO oxidation. In addition, carbonates, formed over the Pt‐containing catalysts under the reaction conditions, inhibited the interfacial active sites for O 2 activation at temperatures below the threshold at which CO inhibition of Pt sites disappeared. Therefore, the inactivity of Pt/ZnO was ascribed not only to CO poisoning on the Pt sites but also to the blocking of the Pt‐ZnO interfaces by carbonates. By contrast, the high activity of Au/ZnO was associated with the weaker adsorption of CO and the efficient O 2 activation at the interface.