High-entropy oxides (HEOs) containing five or more cations have garnered significant attention recently due to their vastly tunable compositional space, along with their remarkable physical and mechanical properties, exceptional thermal stability, and phase reversibility at elevated temperatures. These characteristics position HEOs as promising candidates for structural components and coatings in high-temperature applications. While much of the ongoing research on HEOs centers around understanding processing-structure relationships, there remains a dearth of knowledge concerning their mechanical properties, crucial for their prospective high-temperature applications. Whether in bulk form or as coatings, the efficacy of HEOs hinges on robust mechanical properties across a spectrum of temperatures, to ensure structural integrity, fracture resistance, and resilience to thermal stress. This review offers a succinct synthesis of recent advancements in HEO research, spanning from processing techniques to mechanical behaviors under extreme conditions. Emphasis is placed on three key aspects: (1) Investigating the influence of processing parameters on HEO crystal structures. (2) Analyzing the interplay between crystal structure and mechanical properties, elucidating deformation mechanisms. (3) Examining the mechanical behavior of HEOs under extreme temperatures and pressures. Through this review, we aim to illuminate the effective control of HEOs’ unique structures and mechanical properties, paving the way for their future applications in extreme environments.
Developing stable and efficient electrocatalysts is vital for boosting oxygen evolution reaction (OER) rates in sustainable hydrogen production. High-entropy oxides (HEOs) consist of five or more metal cations, providing opportunities to tune their catalytic properties toward high OER efficiency. This work combines theoretical and experimental studies to scrutinize the OER activity and stability for spinel-type HEOs. Density functional theory confirms that randomly mixed metal sites show thermodynamic stability, with intermediate adsorption energies displaying wider distributions due to mixing-induced equatorial strain in active metal-oxygen bonds. The rapid sol-flame method is employed to synthesize HEO, comprising five 3d-transition metal cations, which exhibits superior OER activity and durability under alkaline conditions, outperforming lower-entropy oxides, even with partial surface oxidations. The study highlights that the enhanced activity of HEO is primarily attributed to the mixing of multiple elements, leading to strain effects near the active site, as well as surface composition and coverage.
more » « less- Award ID(s):
- 2029425
- PAR ID:
- 10464641
- Publisher / Repository:
- Nature Publishing Group
- Date Published:
- Journal Name:
- Nature Communications
- Volume:
- 14
- Issue:
- 1
- ISSN:
- 2041-1723
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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