Chemical Insights into High Entropy Alloy Nanoparticle Formation and Reactivity

With the support of the Macromolecular, Supramolecular and Nanochemistry Program in the Division of Chemistry, Professor Schaak of Pennsylvania State University will develop chemical reactions to form nanoparticles of high entropy alloys, which contain five or more elements. The large number of elements in these nanoparticles may lead to unique properties that are useful in many applications, including as catalysts for chemical reactions relevant to clean energy technologies. Prof. Schaak and his group will develop chemical reactions for making high entropy alloy nanoparticles in solution and understand how, why, and when they form. They will also define the chemical reactivity of these nanoparticles to understand how they transform when exposed to different reagents. The knowledge gained from this research will lead to future advances in catalysis and other fields by allowing the properties of high entropy alloys to be tuned in new ways through control over nanoscopic features. Prof. Schaak and his group will develop tutorials and learning modules based on unique aspects of high entropy alloy nanoparticle synthesis and characterization, which will impact a broad community of students and researchers. Prof. Schaak will also launch a virtual networking and mentoring initiative for early-career researchers. Most strategies for synthesizing high entropy alloy nanoparticles require high-temperature heating and rapid cooling of metal salts loaded onto refractory supports, which provide nanoscale stabilization. However, these methods do not allow finer control over nanoparticle features that are well known to influence properties, including size, uniformity, and shape. Chemical reactions that occur in solution are well suited for nanoparticle synthesis, but solution routes to high entropy alloys remain limited, and little is known about how they form, grow, and transform. Prof. Schaak’s research team will elucidate the pathways by which selected high entropy alloy nanoparticles form in solution and evaluate how diverse reaction parameters influence reaction outcomes. There also is limited knowledge about the chemical reactivity of high entropy alloy nanoparticles, which is important for using them in applications. The large number of constituent elements in high entropy alloy nanoparticles is likely to lead to unique synergistic properties, such as modified selectivity and increased stability in catalysis. Prof. Schaak and his group will study the reactivity and stability of high entropy alloy nanoparticles, including in solution with a broad range of inorganic reagents. These experiments will lead to the formation of new classes of high entropy alloy nanoparticles and provide foundational knowledge about how application-relevant features of colloidal high entropy alloy nanoparticles can be controlled and tuned. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.