PH-Dependent Distribution of Functional Groups on Titanium-Based MXenes

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Journal Title
Journal ISSN
Volume Title
A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
Date
2019-01-01
Major/Subject
Mcode
Degree programme
Language
en
Pages
9171−9181
Series
ACS Nano, Volume 13, issue 8
Abstract
MXenes are a new rapidly developing class of two-dimensional materials with suitable properties for a broad range of applications. It has been shown that during synthesis of these materials the surfaces are usually functionalized by O, OH, and F and further suggested that controlling the surface allows controlling the material properties. However, a proper understanding of the surface structure is still missing, with a significant discrepancy between computational and experimental studies. Experiments consistently show formation of surfaces with mixed terminations, whereas computational studies point toward pure terminated surfaces. Here, we explain the formation of mixed functionalization on the surface of titanium-based two-dimensional carbides, Ti2C and Ti3C2, using a multiscale modeling scheme. Our scheme is based on calculating Gibbs free energy of formation by a combination of electronic structure calculations with cluster expansion and Monte Carlo simulations. Our calculations show formation of mixtures of O, OH, and F on the surface with the composition depending on pH, temperature, and the work function. On the other hand, our results also suggest a limited stable range of compositions, which challenges the paradigm of a high tunability of MXene properties.
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Keywords
2D materials, density functional theory, functional group, multiscale simulation, MXene
Other note
Citation
Ibragimova, R, Puska, M J & Komsa, H P 2019, ' PH-Dependent Distribution of Functional Groups on Titanium-Based MXenes ', ACS Nano, vol. 13, no. 8, pp. 9171−9181 . https://doi.org/10.1021/acsnano.9b03511