Atomic oxygen absorption into Pt-based alloy subsurfaces

Density functional theory is used to study atomic oxygen absorption into subsurfaces of various platinum-based alloys to investigate the effects of alloyed metals on the thermodynamics and kinetics of this process. The results show that alloying Pt with Ir and Rh increases the absorption energy barrier compared with pure Pt, making the O migration to the subsurface more difficult, and that the addition of Co and Ru to Pt can decrease the reverse energy barrier of absorption making O unstable in the subsurface. By comparison of the atomic oxygen absorption in Pt3X alloys with that in PtX alloys, it is found that both the nature of the alloyed metal species and the alloy composition have effects on the atomic oxygen absorption kinetics. Analyses of the atomic oxygen absorption into the subsurface of ternary alloys such as Pt2IrRu show that compared with pure platinum the presence of the two added metals can increase the barriers for surface diffusion and that for O absorption while simultaneously decreasing the reverse energy barrier, therefore inhibiting the atomic oxygen absorption process more effectively. Pt "skin" monolayers on Pt alloys show increases in the atomic oxygen absorption energy barrier and in their corresponding reverse energy barrier.