Carbon materialization of ionic liquids: from solvents to materials

Abstract

Synthesis, characteristics, porous design, and potential applications of novel carbon materials derived from ionic liquids precursors have been reviewed, including future trends and prospects in this direction.Carbon materials have been extensively used in diverse areas , especially in energy-related applications. Traditionally, these materials have been synthesized by carbonization of lowvapor-pressure natural or synthetic polymers. However, the polymer-related procedures are multistep and time consuming because of limited solubility and complicated synthesis. 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-liquidderived carbons. The review concludes with an overview of possible directions for future research in this field.In contrast, because of their high surface areas, electrical conductivities, low costs, and excellent chemical, mechanical, and thermal stabilities, carbon materials have been extensively used in diverse areas such as environmental treatment, catalysis, sensing, separation, gas capture/storage, and, particularly, as electrode materials or electrocatalysts for energy conversion/storage. [13][14][15][16][17][18] Carbon materials are generally prepared by carbonization of carboncontaining precursors at high temperature. The nature of the organic precursor is crucial to the preparation process (e.g., interactions between precursor and template 19 ), and the structures, properties, and performances of the final carbons. The chemical compositions of the precursors are often reflected in the final carbons, and strongly affect characteristics such as the carbon yield, porosity, surface area, graphitization, conductivity, and heteroatom doping. Most organic compounds are completely evaporated or decomposed to gaseous products during high-temperature carbonization, therefore currently available precursors are rather limited, and are mainly low-vaporpressure natural or synthetic polymers. 20 However, polymer-related procedures are multistep and time consuming. Moreover, for carbons derived from "hard carbon" precursors such as sucrose and furfuryl a...

A sustainable synthesis alternative for IL-derived N-doped carbons: Bio-based-imidazolium compounds

“…However, mostly because of the challenging synthetic and purification processes, common ionic liquids are still rather expensive. Therefore, the need for reduced costs for carbon materialization of ionic liquids has been established as one of the main challenges in this field [9]. Besides existing works on protic ionic liquids [10] with regard to price and improved sustainability, we recently presented the convenient synthesis of bifunctional imidazolium compounds using natural amino acids as green starting materials [11].…”

One-step, template-free synthesis of highly porous nitrogen/sulfur-codoped carbons from a single protic salt and their application to CO2 capture

“…8,53 The obtained protic salt was subjected to direct carbonization in a tube furnace under an Ar atmosphere (100 mL/min) using the following temperature program: (1) degassing at room temperature for 1 h; (2) heating to 250 °C at a rate of 10 °C /min; (3) further heating to 350 °C at a rate of 2 °C /min; (4) heating to the desired temperature (e.g., 1000 °C ) at a rate of 10 °C /min; and finally, (5) maintaining the sample at this temperature for 2 h. After cooling the sample to room temperature, the obtained carbon materials were powdered for further characterization. [Allyl-NH 3 ][HSO 4 ] was synthesized according to the established procedure.…”

Pristine‐Graphene‐Supported Nitrogen‐Doped Carbon Self‐Assembled from Glucaminium‐Based Ionic Liquids as Metal‐Free Catalyst for Oxygen Evolution

“…[7,9,10] Heteroatom-doped carbon materials, in particulart he Ndoped ones, have great potential as metal-free OER catalysts because the Na toms can effectively modulate charged istribution and the electronic structure of adjacent carbon atoms to promotec atalytic activity. [12][13][14] Assembly of N-doped carbon materials on highly conductive and high-surface-areac arbon nanostructures could be ap romising strategy to obtainh ighly N-doped carbon with high OER catalytic activity because the supports can promote the dispersion of N-doped carbonm aterials for high surface density of catalytically active sites, inhibitt heir aggregation during storage and under harsh electrochemical conditions, facilitatee lectron transfer andtransport, and even introduce synergistic properties. [12][13][14] Assembly of N-doped carbon materials on highly conductive and high-surface-areac arbon nanostructures could be ap romising strategy to obtainh ighly N-doped carbon with high OER catalytic activity because the supports can promote the dispersion of N-doped carbonm aterials for high surface density of catalytically active sites, inhibitt heir aggregation during storage and under harsh electrochemical conditions, facilitatee lectron transfer andtransport, and even introduce synergistic properties.…”

“…[27][28][29] In particular,t he in situ self-assembly of N-containing precursors on graphene could directly produce ag raphene-supported N-doped carbonl ayer with intimate contact between the N-doped carbon and the graphene for maximizing the surfaced ensity of active sites, facilitating electron transfer,and introducingpossible synergistic effects. [30,34] Glucaminium-based ionic liquids (GILs) could be promising precursors fori nsitu self-assembly of N-doped carbon on graphene for the following reasons:1)dehydration and carbonization of their carbohydrate component, which can be performed at ar elatively low temperature, provides possibilities for realizing in situ self-assembly on graphene; [16,30,34] 2) the non-carbohydrate portion can be chemically tailoredt oe nhance the affinity to pristine graphene and promote the in situ self-assembly process; [35,36] 3) the quaternary Na tom can be uniformly incorporated into the carbon during the in situ selfassembly process; [14,37] 4) graphene can serve as an effective template to promote graphitization of the N-doped carbon owing to its largea nd intact p-conjugated structure. [30,34] Glucaminium-based ionic liquids (GILs) could be promising precursors fori nsitu self-assembly of N-doped carbon on graphene for the following reasons:1)dehydration and carbonization of their carbohydrate component, which can be performed at ar elatively low temperature, provides possibilities for realizing in situ self-assembly on graphene; [16,30,34] 2) the non-carbohydrate portion can be chemically tailoredt oe nhance the affinity to pristine graphene and promote the in situ self-assembly process; [35,36] 3) the quaternary Na tom can be uniformly incorporated into the carbon during the in situ selfassembly process; [14,37] 4) graphene can serve as an effective template to promote graphitization of the N-doped carbon owing to its largea nd intact p-conjugated structure.…”