Ionic liquids (IL) are widely used in electrochemistry due to their excellent properties such as good ionic conductivity, wide electrochemical potential window, high viscosity, high thermal stability, wide liquid range and tunable solvent properties. In electrochemistry, the performance of an electrochemical system is dependent on the properties of the interface at the IL/electrode. This review presents the surface electrochemistry in ILs, and the interfacial structures of IL/electrode and heterogeneous electron-transfer kinetics are detailed. Finally, the updated researches on the electrochemical applications of ILs such as electrode deposition, electrosynthesis, electrocatalysis, electrochemical biosensing, electrochemical capacitor and lithium batteries are demonstrated.

We report a novel and facile synthesis of a high-quality graphene oxide (GO)–polyaniline (PANI) composite by in situ polymerization suitable for supercapacitor application. Unlike the use of the edged carboxyl groups of graphene sheets as linkers, the current work makes the most of the ample oxygenated groups on the basal plane of graphene sheets to combine with the amine nitrogens of the PANI chain. This is tactically realized by a carboxyl-functionalized process of GO with oxalic acid treatment prior to the combination. The as-constructed carboxyl-functionalized graphene oxide–polyaniline (CFGO–PANI) composite was roundly characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), Fourier-transformed infrared spectrometry (FTIR), Raman spectrometry, and thermogravimetric analysis (TGA), and a stable, highly efficient charge-transfer configuration was disclosed and confirmed. The fabricated electrode composed of this CFGO–PANI material showed an excellent electrochemical capacitance performance with aqueous H₂SO₄ electrolytes.