Epitaxial oxide bilayer on Pt (001) nanofacets

Daniel Hennessy,Peter Zapol,Hoydoo You,Hakim Iddir,Andi Barbour,Andreas Menzel,Vladimir Komanicky,Michael S Pierce,Kee-Chul Chang

doi:10.1063/1.3678858

Abstract

We observed an epitaxial, air-stable, partially registered (2 × 1) oxide bilayer on Pt (001) nanofacets [V. Komanicky, A. Menzel, K.-C. Chang, and H. You, J. Phys. Chem. 109, 23543 (2005)]. The bilayer is made of two half Pt layers; the top layer has four oxygen bonds and the second layer two. The positions and oxidation states of the Pt atoms are determined by analyzing crystal truncation rods and resonance scattering data. The positions of oxygen atoms are determined by density functional theory (DFT) calculations. Partial registry on the nanofacets and the absence of such registry on the extended Pt (001) surface prepared similarly are explained in DFT calculations by strain relief that can be accommodated only by nanoscale facets.

Highlights

INTRODUCTIONDespite being active for forming and breaking chemical bonds, the platinum surface is not easy to oxidize
Platinum is the most important element for electrocatalysis
Sitive to oxygen atoms, oxygen bonds are inferred from the Pt oxidation states, and oxygen positions are theoretically determined by using density functional theory (DFT)

Summary

INTRODUCTION

Despite being active for forming and breaking chemical bonds, the platinum surface is not easy to oxidize. According to recent theoretical studies platinum should preferentially oxidize below 1000 K, which implies a need for a protective surface layer. Neither submonolayer oxygen adsorption nor loosely formed oxide layers reported in studies at high oxygen pressure seem sufficient to form proper protective kinetic barriers against oxidation, especially for high-index surfaces. Sitive to oxygen atoms, oxygen bonds are inferred from the Pt oxidation states, and oxygen positions are theoretically determined by using density functional theory (DFT). Both (001) and (111) nanofacets were studied, but we will focus on the (001) nanofacets

EXPERIMENTAL

EXPERIMENTAL RESULTS AND DISCUSSIONS

COMPUTATIONAL RESULTS AND DISCUSSIONS

CONCLUSIONS