Adsorption of ionic liquids forming species on Ti3C2Tx MXenes surfaces by first-principle calculations

Abstract

MXenes are two-dimensional layered materials that have attracted increased attention for technological applications, e.g., electrodes, support for single atom catalysts, etc. Several experimental and computational studies have been reported, however, our atomistic understanding is still far from good, in particular, for MXene-ionic liquid interfaces, which is crucial to predict and control the charge–discharge rate of those systems. Here, we have assessed the adsorption of ionic liquids forming species, on surfaces of Ti3C2Tx (where T = F, O or OH) MXenes by means of ab initio calculations at density functional theory level. The F and O terminated MXenes showed to be stables upon the adsorption, whereas the OH terminated one suffered important structural deformations when interacting with cationic species. The adsorption of molecular species are stronger, with values ranging in between −1.10 and −7.36 eV, indicating the contribution of Coulombic and induction interactions as a result of the charge transference among MXenes and adsorbates. The adsorption of ionic pairs on the Ti3C2F2 and Ti3C2O2 monolayers were driven by dispersion interactions, that represent at least 84% of the total adsorption energy. Additionally, the work function of the stable MXenes structures were barely affected by the adsorption of the ionic pairs, and hence, the adsorption process did not affect the electronic properties of the single Ti3C2Tx monolayers.