Revealing the wetting mechanism of Li+-doped ionic liquids on the TiO2 surface

Abstract

The sensible design of ionic liquid (IL)-based application relies on a thorough knowledge of the structure and characteristics of electrolyte–electrode interfaces. Here, the wetting processes of the Li+-doped ILs droplets on the TiO2-B(100) surface are investigated by molecular dynamics simulation. According to the spatial distributions of components, doped Li+ prefers to substitute the ILs and adsorb to the substrate, causing the orientation changes of the ILs, weakening the ILs-substrate interaction, and slowing down the wetting process significantly. As Li+ concentration rises from 0 to 80 %, the contact angle increases from 86.97 to 131.18°, inducing the hydrophilic-to-hydrophobic transition. On the contrary, heating up would reduce the contact angle by extending the contact length and enhancing the maximum density of Li+-doped ILs at the interface. These quantitative results prove that the dense adjacent layer in the interface induced by the strong adsorption of Li+ dominates the wetting process of Li+-doped ILs.