CFM Lunch Seminar

Title:

Understanding the Role of Entropy in Medium to High-Entropy Oxides and Alloys for Clean Energy Applications

Abstract:

Report Summary: This report introduces a universal non-equilibrium flame synthesis technique designed to overcome the Hume-Rothery rules that limit the solubility of elements in solid-state materials, which enables the combination of elements that are typically immiscible in the same  phase. Starting with binary ceramic solid solutions, we have extended our approach to multielement systems, developing medium (3~4 elements) and high entropy (5 elements) materials. In our exploration of binary system thermodynamics, we discovered an  “encapsulated exsolution” phenomenon where ultrastable metal nanoparticles precipitate in situ within porous  nanoshells. These unique structures exhibit exceptional anti-sintering capabilities and sustained high conversion rates at 800°C for methane dry reforming to syngas. Furthermore, we have developed high-entropy oxide (HEOs) with diverse crystal structures, including rock salt, spinel, tetragonal, fluoride, and rutile types. Utilizing (MgCoNiCuZn)O x as a “single-atom level” entropy dispersion carrier, we achieved up to 10 wt% loading of single-atom catalysts which demonstrated  unprecedented thermal stability and activity in CO 2 hydrogenation reactions, far exceeding the traditional 1 or 2 wt%. In the field of high entropy alloys (HEAs), we propose and demonstrate an entropy-induced reduction mechanism to incorporate oxidizable elements into HEAs, which extends the compositional space of HEA nanoparticles to nearly all metals. The developed high-entropy PdPtOsIrAu alloy system proved its potential with over 10,000 cycles of stability in electrocatalytic applications. We look  forward to further advancing entropy-driven oxides, alloys and even metal-organic frameworks in the clean energy sector.