A Density Functional Study of Oxygen Adatoms on a Step-Doubled Platinum Surface

Abstract

An investigation into the effect of surface roughness on adsorption and diffusion of oxygen atoms on platinum surfaces using density functional calculations of oxygen interacting with a step-doubled Pt(211) surface is reported. Oxygen atoms are preferentially adsorbed on bridge sites of the step edges, with adsorption at step-bottom sites energetically unfavorable. It is shown that the site preference correlates well with the electronic states of the outermost Pt atoms in a pristine surface without adsorption as revealed by distributions of d-band centers. The change at the step edge is considered to be related to smoothing of the electronic distribution at steps, known as the Smoluchowski effect. The adsorption behavior on the step-doubled surface is similar to that found for a single-atomic-stepped Pt(211) surface but exhibits more localized changes in energy in the vicinity of the step edge and bottom. The calculated energy barriers for oxygen atom diffusion indicate that, while the barrier of 1.42 eV ...