Molecular-level understanding of electric double layer in ionic liquids

Electrochemical interfaces in ionic liquids (ILs) are structurally anisotropic with multi-scaled and multi-natured interactions between electrode and IL as well as among ions of IL. Combined short-ranged and long-ranged surface techniques with high spatial, time and energy resolutions need to be employed to precisely characterize the lateral structure and vertical arrangement of IL at the interface. We briefly review recent advancements on the understanding of the molecular structure of electric double layer (EDL) at electrode-IL interfaces, with emphasis laid on the necessity of detailed and systematic potential-dependent measurements across and at close to the potential of zero charge (PZC). Future directions of fundamental investigations on EDL are briefly discussed.