Structure and activity of oxidized Pt(110) and alpha-PtO2.

We present a density functional theory study of the structure and reactivity of Pt(110) under high loads of atomic oxygen. Surface structures in which the oxygen adsorbs on PtO2-like stripes along the Pt ridges of the Pt(110) are found to be highly stable. The structures become further stabilized when Pt atoms are ejected from the Pt ridges since this allows for stress relief along the PtO2 stripes. Our results thus corroborate the Pt(110)-(12x2)-22O surface oxide structure proposed by Li et al. [Phys. Rev. Lett., 2004, 93, 146104]. We further considered the structure and stability of bulk alpha-PtO2 oxide surfaces. The (0001) and (1010) facets are found to be the lowest energy facets. Finally, the reactivity of the surface oxide and the oxide surfaces in terms of CO oxidation was investigated. We find small energy barriers for the reaction at the Pt(110)-(12x2)-22O surface oxide and at the (1010) facet of alpha-PtO2, but only large barriers over the alpha-PtO2(0001) surface.