Why alloying with noble metals does not decrease the oxidation of platinum: a DFT-based ab initio thermo-dynamics study

Abstract

Despite its well-known nobility, even platinum is subject to corrosion under the harsh conditions that many technical applications require. Based on the assumption that the platinum loss is mainly caused by the formation of volatile PtO₂, alloying is a promising strategy to reduce it. This investigation explores the bulk stability of Pt–Au, Pt–Ir, Pt–Re, Pt–W, Pt–Ag, Pt–Rh, Pt–Cu, Pt–Ni and Pt–Co, as well as their oxides, utilizing density functional theory, as well as ab initio and literature thermodynamic data. The alloy model combines special-quasi random structures with thermodynamic properties interpolated from the constituting metals, which are complemented by the configuration entropy. The results suggest that reducing platinum oxidation by alloying decreases the overall nobility of the alloy, since platinum- and oxygen affinity of the alloying metal are related to each other. Despite this limitation, copper was identified as a promising candidate for stabilizing the platinum catalyst in the Ostwald process.