Electric double-layer of [emim][DCA] ionic liquid at heterogeneous interface of TiO₂/C composite: From simulation to experiment

The hydrophilicity/hydrophobicity of heterogeneous interface of the electrode material is critical for the performance of ionic liquids supercapacitors. However, the behavior of electrolytes at the electrode interface, especially the interface microstructure and properties is not yet clear. We investigated the electric double-layer of [emim][DCA] on slit pore of TiO₂/C composite with the heterogeneous surface by combining molecular dynamics simulation and experimental measurements. The results of simulation show that coverage ratio of carbon on the surface affect the number density distribution, orientation and diffusion coefficient of [emim][DCA]. Moreover, we calculated the charge distribution of electric double-layer of [emim][DCA] and the capacitance. The results indicate that the capacitance of slit pore with the surface of TiO₂ with 78.7% carbon coverage ratio has the highest capacitance at high surface charge density. We performed an electrochemical experiment using composite of TiO₂ covered with carbon as the electrode material, and obtained the capacitance from cyclic voltammetry (CV). The experimental results also indicate there is an optimal coverage ratio of carbon, which achieves the highest capacitance. Our researches could provide a microscopic perspective of the electric double layer at the heterogeneous interface and the guidance for the design of electrode material.