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(öffnet in neuem Fenster).
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.
