Selective Oxidation of the Intermetallic Compound PtAl₂ from Ab Initio Thermodynamics

Abstract

The atomic structures of pristine and oxygen-covered PtAl 2 (100) and PtAl 2 (110) surfaces are studied by density functional theory modeling. Surface phase diagrams for oxygen adsorption on the two lowindex PtAl 2 surfaces are constructed. We show that the composition for the pristine surfaces is determined by the bulk composition, where the most stable surface configurations are the bulk terminations over the dominant range of the chemical potential of Al examined. By contrast, oxygen adsorption induces surface segregation of Al and leads to selective oxidation of Al upon increasing the oxygen chemical potential. An atomic and dynamic perspective of the oxygen adsorption-induced surface segregation is presented. The aluminum oxide formation results in Pt enrichment in the subsurface region that hinders inward oxygen embedment and outward Al diffusion, thereby serving as a protective layer against further oxidationinduced alloy degradation.

Temperature-Dependent Selective Oxidation Behavior of Al2Au Alloy: Insights for Tailoring Au-Enhanced Oxide Layers

“…Alloying is a common strategy for obtaining protective oxide layers on surfaces by selectively oxidizing a specific component within the alloy. − The process of selective oxidation in alloys involves numerous physical and chemical phenomena such as atomic diffusion, oxidation reactions, and interface evolution, which are influenced by factors including alloy structure, composition, and oxidation conditions. − Establishing a comprehensive theoretical framework for selective oxidation presents a substantial challenge.…”