Growth of Pt Nanoparticles on Reducible CeO₂(111) Thin Films: Effect of Nanostructures and Redox Properties of Ceria

Abstract

Pt nanoparticles grown on fully oxidized and partially reduced CeOx(111) thin films have been studied by scanning tunneling microscopy and X-ray photoelectron spectroscopy to understand the effect of redox properties and nanostructures of ceria supports on the growth of Pt. Deposition of 0.2 ML of Pt on CeO2 at 300 K produces two atomic layer high nanoparticles, while on reduced ceria films Pt favors the growth of smaller particles of one−two layer thick with a larger particle density. With the increase of Pt coverage, Pt particles on CeO2 grow in size while the Pt particle density significantly increases on the reduced ceria. Heating the surface to higher temperatures causes the Pt particle agglomeration, but Pt particles sinter less on the reduced ceria compared to those on the fully oxidized ceria. New particle structures are formed on reduced ceria as a result of heating which are suggested due to the encapsulation of Pt particles by ceria. In addition to the structural changes of the Pt particles, modifications of electronic properties of both ceria and Pt were observed upon Pt deposition as well as after heating. Our combined scanning tunneling microscopy and X-ray photoelectron spectroscopy studies suggest a complex growth behavior of Pt on ceria and a strong interaction between the Pt and the ceria support.