2D High Entropy Materials: New Frontiers in Materials Science

Two-dimensional high entropy materials combine the unique behavior of solid-solution and entropy-stabilized systems with high aspect ratios and atomically thin characteristics of 2D materials.
Published in Materials
2D High Entropy Materials: New Frontiers in Materials Science
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Multiple principal elements or high-entropy materials are an exciting field of materials science. These materials are composed of multiple elements in roughly equal proportions, creating a unique and complex structure that can have interesting properties and have been studied extensively in the alloys phase space since the 2000s.1 The concept of entropy stabilization further extended to ceramics from 2015 towards the realization of compounds with entropic contribution from both the metallic and non-metallic sub-lattices.2 Since 2021, the concept of entropy stabilization was extended to two-dimensional (2D) materials with stable phases being reported in oxide, chalcogenide, carbide/carbonitride, and hydroxide forms with promising applications.3, 4, 5

Our US-German-cooperation perspective article discusses entropy stabilization from bulk to 2D systems, the influence of disordered multi-valent atoms on lattice distortion, and the subsequent effect on the local electronic structure. Further, we reflect on how these atomistic changes influence the properties of these materials with a focus on their electrochemical and catalytic response. We also provide a perspective on 2D high-entropy materials research and its challenges. Finally, we also discuss the importance of this emerging field of nanomaterials in designing tunable compositions with unique electronic structures for energy, catalytic, electronic, and structural applications.

One fascinating aspect of bulk high-entropy materials is the "cocktail effect." This effect occurs when multiple elements are mixed, resulting in enhanced properties which are not present in any of the individual elements. For example, the cocktail effect plays a significant role in property enhancement in bulk high-entropy materials. But to what extent can this be translated to 2D structures? For example, high-entropy transition metal carbides/nitrides (MXenes) have been predicted to exhibit some short-range order of atoms in different atomic planes6, leaving us with a vast explorative space towards understanding these fascinating property derivatives.

Can introducing disorder in the non-metal sub-lattices lead to stable structures not reported in bulk forms? We reflect upon substitutional disordering in these sites that can increase the entropy of mixing, leading to greater stabilities and higher working potentials for cathode materials, which was demonstrated in bulk high-entropy oxides with the addition of fluoride salts.7

Another potential avenue for high-entropy 2D materials is for selective ion-sieving and sensing applications. We discuss how tailorable basal atomic plane activity could lead to highly efficient sensing devices. The high-entropy 2D compounds provide a platform to understand better the correlation of electronic structure and the improvement of mechanical properties reported in some bulk high-entropy carbides.

Composition-structure-property mapping in 2D high-entropy systems is at a nascent stage. We believe high-entropy 2D materials will provide a wide degree of tunability and control for deriving unique synergies in materials. As continued development of these materials moves into the current decade and beyond, high-entropy 2D materials have the potential to address some of the persistent challenges toward sustainable goals. The potential of these materials is enormous, and we are only just beginning to scratch the surface of what they have to offer.

The perspective article can be found here: Functional two-dimensional high entropy materials

References:

  1. Yeh JW, et al. Nanostructured High‐entropy Alloys With Multiple Principal Elements: Novel Alloy Design Concepts and Outcomes. Advanced Engineering Materials 6, 299-303 (2004).
  2. Rost CM, et al. Entropy-stabilized Oxides. Nature communications 6, 1-8 (2015).
  3. Cavin J, et al. 2D High-entropy Transition Metal Dichalcogenides for Carbon Dioxide Electrocatalysis. Advanced Materials 33, 2100347 (2021).
  4. Nemani SK, et al. High-entropy 2D Carbide MXenes: TiVNbMoC3 and TiVCrMoC3. ACS Nano 15, 12815-12825 (2021).
  5. Li F, et al. Bottom-up Synthesis of 2D Layered High-entropy Transition Metal Hydroxides. Nanoscale Advances 4, 2468-2478 (2022).
  6. Leong Z, Jin H, Wong ZM, Nemani K, Anasori B, Tan TL. Elucidating the Chemical Order and Disorder in High-Entropy MXenes: A High-Throughput Survey of the Atomic Configurations in TiVNbMoC3 and TiVCrMoC3. Chemistry of Materials 34, 9062-9071 (2022).
  7. Wang Q, et al. Multi-anionic and-cationic Compounds: New High Entropy Materials for Advanced Li-ion Batteries. Energy & Environmental Science 12, 2433-2442 (2019).

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Go to the profile of Yury Gogotsi
about 1 year ago

Great blog on a very nice article!

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Physical Sciences > Materials Science

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