Two-dimensional high entropy alloys and ceramics

Project Information

HighEntropy2D

Grant agreement ID: 101088366

DOI

10.3030/101088366

EC signature date 2 May 2023

Start date 1 June 2023

End date 31 May 2028

Funded under

• European Research Council (ERC)

Total cost

€ 1 995 465,00

EU contribution

€ 1 995 465,00

Coordinated by

TECHNISCHE UNIVERSITAET WIEN
Austria

Periodic Reporting for period 1 - HighEntropy2D (Two-dimensional high entropy alloys and ceramics)

Reporting period: 2023-06-01 to 2025-11-30

Summary of the context and overall objectives of the project

“Entropy engineering” recently had exceptional impact on bulk materials science by invention of bulk high entropy alloys and ceramics. The underlying idea is that by equiatomically adding ≥5 principal elements to alloys/compounds, the much increased configurational entropy stabilizes otherwise non-accessible single “high entropy” phases with an unique random elemental occupancy on a crystalline lattice and hence novel functional properties. Likewise, reducing dimensionality in “two-dimensional” (2D) materials recently had exceptional impact on materials science due to the 2D materials’ unique functional properties. Despite these exciting individual prospects of “entropy engineering” and “2D materials”, combination of these two concepts to synergetically create novel 2D high entropy materials (2D HEMs) as a novel materials class with novel functional properties with possible applications in electronics and catalysis remains lacking. In “HighEntropy2D” we will fabricate unprecedented 2D HEMs (2D high entropy alloys (2D HEAs), oxides (2D HEOs) and sulfides (2D HESs)) using for the first time scalable vapour deposition and a 2D template/2D confinement approach for both 2D film and 2D nanoflake form, asses their novel properties and perform first tests of their applicability for electronic devices and catalysis. Reducing HEM dimensionality to 2D will also create a unique opportunity to for the first time study in situ and at the atomic scale currently unknown fundamental diffusion, crystallisation, phase transition and separation mechanisms in HEMs (using a globally unique (scanning) transmission electron microscopy ((S)TEM) setup), to obtain fundamental insights relevant to HEMs even beyond the here newly introduced 2D HEMs.

Work performed from the beginning of the project to the end of the period covered by the report and main results achieved so far

So far the 5 most significant achievement from the project in its first two years are the following:
1. Observation at atomic scale that before 2D HEO formation an intermediate high entropy alloy phase without oxygen incorporation forms which then jointly transforms to a HEO phase of the same elements. This is a thus far not reported kinetic pathway to HEO formation via an intermediate HEA stage. We observed this not only atomically resolved via (S)TEM on the sputter deposited ultrathin 2D HEOs but also via in situ XRD for the bulk HEO equivalent, underscoring the generality of this new mechanistic finding. This data is currently in write up.
2. We have developed a low-temperature, wet chemistry 2D HES synthesis route (based on dithiocarbamate based precursors, complementary to the sputter deposition route). For these materials we find that these 2D HES outperform traditional single principal element sulfides and non-HE mixtures in long-term photocatalytic performance for hydrogen evolution. A corresponding paper is currently in submission.
3. Our developed 2D HES materials served as a methodology development testbed to advance elemental quantification methology by a collaborating group by laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) for multi-elemental systems, see recently published collaborative paper in Adv. Sample Prep., 16, 100223, (2025), https://doi.org/10.1016/j.sampre.2025.100223.
4. Throughout our data we observe that kinetic pathways (and not only composition) govern 2D HES and 2D HEO formation much more than previously thought. For instance, this is highlighted when comparing our sputter deposited 2D HES atomic resolution in situ (S)TEM insights with results from the high temperature HES synthesis with subsequent liquid phase exfoliation (LPE) structuring to 2D HES. The fact that we have now established in the project not only sputter deposition for 2D HES synthesis but also complementary high temperature powder bulk/LPE synthesis and low temperature wet-chemistry synthesis puts us into the unique position to now compare kinetic pathways for fixed 2D HES compositions and thus for the first time disentangle kinetic from composition effects. Currently, this comparison for 2D HES systems is a focus of our work.
5. The various 2D HESs from the developed synthesis routes offer complementary materials properties in terms of crystallinity, particle size and form factors all with different merits. Accompanying the structural in situ studies, we have also tested the new HES with respect to application perspectives and in particular for photocatalysis find very promising results for both the high and low temperature 2D HES synthesis routes, which are currently under write-up.

Progress beyond the state of the art and expected potential impact (including the socio-economic impact and the wider societal implications of the project so far)

In particular the achievements 1-4 are beyond the state-of-the-art in the literature, and are currently in the process of publication.