Phase Changes of Multielemental Alloy Nanoparticles at Elevated Temperatures

Multielemental alloy (MEA) nanomaterials, such as medium and high entropy alloys, display promising catalytic performance in a range of chemical reactions due to their multicomponent structural configurations. These complex structural and chemical arrangements can be influenced by several factors, such as mechanical stress, irradiation, and high temperatures, which impact the performance of MEAs in various applications. Here, we investigated the effect of high temperatures on MEA nanoparticles composed of noble and transition metals (quaternary PtPdFeCo) at the atomic scale and found the material undergoes a series of phase transitions between solid solution and intermetallic phases at elevated temperatures ranging from room temperature to 1073 K. In contrast, the binary PtFe nanoalloy displays a one-way solid solution to intermetallic transition at these temperatures. Our findings, rationalized by density functional theory (DFT) studies, demonstrate how the varied migration energies of elements govern the solid solution to intermetallic transition and how differences in the bonding energies of elemental pairs influence the Gibbs free energy change (Δ<i>G</i>), which dictates the intermetallic to solid-solution transition. Overall, this work provides better guidance in the design, development, and usage of nano-MEAs for high-temperature-based applications.