Layla BOU TANNOUS1,2, Mirella SIMOES SANTOS1, Zheng GONG1, Agilio PADUA1, Audrey STEINBERGER3
1Laboratoire de Chimie, ENS de Lyon, CNRS, Lyon, France
2LETI, CEA, Grenoble, France
3Laboratoire de Physique, ENS de Lyon, CNRS, Lyon, France
Room temperature ionic liquids (ILs) can create a strong accumulation of charges at solid interfaces by forming a very thin and dense electric double layer (EDL). The structure of this EDL has important consequences in numerous applications involving ILs, for examples in supercapacitors, sensors and lubricants, by impacting the interfacial capacitance, the charge carrier density of semi-conductors, as well as the frictional properties of the interfaces.
We have studied the interfacial structure of an imidazolium-based IL with a long alkyl chain (1-octyl-3-methylimidazolium dicyanamide) on several substrates using atomic force microscopy (AFM) experiments. We have observed 3 types of interfacial structure for the same IL, depending on the substrate and the water content, showing that the EDL structure is not an intrinsic property of the IL. Complementary experiments and molecular dynamics (MD) simulations evidenced the crucial role of the surface chemistry on the EDL structure, and enabled to better understand the influence of water contamination. We will unveil our results and conclusions in this presentation.