Carbon materialization of ionic liquids: from solvents to materials

Carbon materials have been extensively used in diverse areas, especially in energy-related applications. Traditionally, these materials have been synthesized by carbonization of low-vapor-pressure natural or synthetic polymers. However, the polymer-related procedures are multistep and time consuming because of the limited solubility and complicated synthesis of polymers. Recently, ionic liquids (ILs), composed of entirely cations and anions, have emerged as a new family of carbon precursors. The carbon-rich nature of ILs, coupled with their attractive properties such as diverse cation-anion combinations, low volatilities, and high thermal stabilities, not only greatly simplifies the entire carbonization process, but also gives rise to carbons with attractive features, which are distinct from those of carbons obtained using conventional polymer precursors, such as very high nitrogen contents and conductivities. In this review, we highlight recent approaches to the preparation of carbon materials using ILs as versatile precursors. We begin with a brief introduction to these novel precursors, discussing the key structures and properties of ILs that enable successful carbonization, and then address synthetic techniques for the fabrication of advanced porous carbons from ILs by either self-or external-template methods, followed by a review of the potential applications of ionic-liquid-derived carbons such as electrocatalysis, Li-ion batteries, supercapacitors, CO2 capture and chemical catalysis. The review concludes with an overview of possible directions for future research in this field.