Understanding Electric Field‐Dependent Structure Variation of Functional Ionic Liquids at the Electrode Interface

Abstract Understanding the electric field‐dependent structure variation of ionic liquids (ILs) near electrodes is crucial to the rational design of ILs‐based electrochemical applications. In the present work, the number density and ionic orientation show that anions in imidazole ILs accumulate first and then are pulled out while that in sulfonic imidazole ILs changes little as the electric field strengthens. Meanwhile, the evolution of layered structure of cation and anion leads to a stronger interfacial polarization compared to that in the bulk for various ILs. Moreover, the elongation and sulfonic modification of the side chain can further respectively strengthen and weaken the interfacial polarization. These quantitative relations among structure change, side‐chain length, sulfonic group, and the electric field can provide practical guidelines in the ionic liquid design and management of the related electrochemical processes.