MXenes à la Carte: Epitaxially grown MXene sandwiches with nitrogen sprinkles and metal topping
Joint work from CICECO-UA and the University of Barcelona proposes a new method of growing thicker MXenes by taking advantage of the nitrogen-dissociating capabilities of thinner ones.

The latest study published by the teams led by José R. B. Gomes, from CICECO-Aveiro Institute of Materials and Department of Chemistry of the University of Aveiro, and Francesc Illas, from the Department of Materials Science and Physical Chemistry at the University of Barcelona, with co-authors José Daniel Gouveia, Ángel Morales-García, and Francesc Viñes, proposes a new method for synthesizing MXenes (two-dimensional transition metal carbides and nitrides) by epitaxially growing alternating layers of nitrogen and transition metal atoms. This method takes advantage of the findings of a previous study by the same authors, which showed that MXenes excel at catalysing the dissociation of nitrogen molecules. In the sequel, they developed a “decalogue of MXene epitaxial growth”, a set of ten criteria which must be met for a given three-layer MXene to be able to epitaxially grow into a thicker seven-layer one. These criteria were obtained using density functional simulations and assess the thermodynamic stability and kinetic accessibility of all the intermediate materials attained in the growth process. All the 18 three-layer studied MXenes were found to meet most of the criteria, meaning they are suitable seeds for being epitaxially grown into thicker ones. Thus, these results represent a convenient way to expand, control, and tune the composition, width, and structure of the MXene family. Although the vast majority of the MXenes synthesized to date are carbides, computational models predict their nitride counterparts to be more stable. The method proposed by these scientists also breaks new ground towards the production of much sought nitrogen-based MXenes. The new approach was recently published in the highly reputed ACS Nano scientific journal.


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