Instead of traditional polymer precursors and complex procedures, easily prepared and widely obtainable nitrogen-containing protic ionic liquids and salts were explored as novel, small-molecule precursors to prepare carbon materials (CMs) via direct carbonization without other treatments. Depending on the precursor structure, the resultant CMs can be readily obtained with a relative yield of up to 95.3%, a high specific surface area of up to 1380 m(2)/g, or a high N content of up to 11.1 wt%, as well as a high degree of graphitization and high conductivity (even higher than that of graphite). One of the carbons, which possesses a high surface area and a high content of pyridinic N, exhibits excellent electrocatalytic activity toward the oxygen reduction reaction in an alkaline medium, as revealed by an onset potential, half-wave potential, and kinetic current density comparable to those of commercial 20 wt% Pt/C. These low-cost and versatile precursors are expected to be important building blocks for CMs.

Nitrogen/sulfur-co-doped mesoporous carbon (Phen-HS) was obtained through direct carbonization of a single protic salt, that is, 1,10-phenanthrolinium dibisulfate ([Phen][2 HSO4 ]), in the presence of a colloidal silica template without the use of additional acid or metal catalysts for prepolymerization prior to carbonization. Phen-HS was prepared in a relatively high yield (30.0 %) and has a large surface area (1161 m(2)  g(-1) ), large pore volume (2.490 cm(3)  g(-1) ), large mesopores (≈12 nm), narrow pore-size distribution (7-16 nm), and high nitrogen (7.5 at %) and sulfur (1.3 at %) contents. The surface area/pore-size distribution is much higher/narrower than that of most reported carbon materials obtained from traditional precursors by using the same template. Phen-HS was directly used as an electrocatalyst for the oxygen reduction reaction (ORR) and as an electrode material for supercapacitors. As an efficient metal-free catalyst, Phen-HS exhibited good electrocatalytic activity toward the ORR in a 0.1 M KOH aqueous solution, which is comparable to the activity of a commercial Pt/C catalyst. Electrochemical measurements for Phen-HS used in a double-layer capacitor showed high specific capacitances of 160 and 140 F g(-1) in 1 M H2 SO4 and 6 M KOH, respectively, with good rate capabilities and high cycling stabilities.

Electrochemical reactions in Li-S cells with a solvate ionic liquid (SIL) electrolyte composed of tetraglyme (G4) and Li[TFSA] (TFSA: bis(trifluoromethanesulfonyl)amide) are studied. The sulfur cathode (S cathode) comprises sulfur, carbon powder, and a polymer binder. Poly(ethylene oxide) (PEO) and poly(vinyl alcohol) (PVA-x) with different degrees of saponification (x%) are used as binders to prepare the composite cathodes. For the Li-S cell containing PEO binder, lithium polysulfides (Li2Sm, 2 ≤ m ≤ 8), reaction intermediates of the S cathode, dissolve into the electrolyte, and Li2Sm acts as a redox shuttle in the Li-S cell. In contrast, in the Li-S cell with PVA-x binder, the dissolution of Li2Sm is suppressed, leading to high columbic efficiencies during charge-discharge cycles. The compatibility of the PVA-x binder with the SIL electrolyte changes depending on the degree of saponification. Decreasing the degree of saponification leads in increased electrolyte uptake by the PVA-x binder, increasing the charge and discharge capacities of Li-S cell. The rate capability of Li-S cell is also enhanced by the partial swelling of the PVA-x binder. The enhanced performance of Li-S cell containing PVA-x is attributed to the lowering of resistance of Li + ion transport in the composite cathode.

Three-dimensionally macroporous nitrogen-doped carbon materials are fabricated via carbonization of an ionic-liquid-based small molecule precursor, 1-ethyl-3-methylimidazolium dicyanamide, using opal silica colloidal crystals as ah ard template. As compared to traditional polymerizable monomer-based precursors such as furfuryl alcohol, the entire process involving ionic liquid does not require any acid catalyst and prepolymerization step. More importantly,n itrogen heteroatomsc an be incorporated into the carbon skeleton in situ. The obtained inverse opal carbonsp ossess large surface areas and pore volumes, and high nitrogen content. When acting as metal-free electrocatalysts, the inverse opal carbonse xhibit high catalytic activity and selectivityt owards the oxygen reduction reaction in alkaline electrolyte, much better than that of the furfuryl-alcohol-derived inverse opal carbon and close to that of commercial Pt/C catalysts.The oxygen reduction reaction( ORR) is ak ey process in fuel cells and metal-air batteries. Platinumn anoparticless upported on high-surface-area carbon materials (Pt/C) are the most widely used electrocatalysts for ORR to date. However,h igh cost, the sluggish kinetics of the ORR process, and an intolerance to fuel crossover have limitedt he scalingu po fc orresponding renewable energy technologiesu sing Pt/C catalysts.[1] Consequently, there have been tremendous efforts on finding replacements for Pt-based catalysts. Amongt hese candidates, N-doped carbon materials as alternative metal-free catalysts are of particular interest.[2] Conjugation between the lone pair of the nitrogen heteroatom and p system of the carbon lattices results in structural irregularities in hexagonal carbon rings, imparting new catalytic sites and ah igh catalytic activity.[3] Despite the high performance of N-doped carbons, their catalytic activities are still far from satisfactory.T his is partly because of their relatively low nitrogen content as well as al ow surface utilization, resulting from randomly formed inaccessible narrow,s mall mesopores. Thus, aw ell-defineda nd continuousp orous structure with ar elativelyl arge surface area, large pore volume, regularp ores, and high nitrogen content is more preferable for high electrocatalytic activity.In this respect, inverse opal carbons (IOCs), which possess cage-like, orderedm acropores and three-dimensionally interconnected windows, could meet these requirements.[4] The large surface area and uniform pore size may facilitate the access of reactants to the active sites and allow ag ood reactant flux, resulting in high catalytic activity.I OC is technologically important for variousa pplicationss uch as photonic crystals, catalysis,s ensing, and separation techniques. For example, it has been previously reported that graphitic carbon nitride supported on three-dimensional interconnected macroporous carbon showed catalytic activity towards ORR comparable to that of commercial Pt/C.[5] Additionally,t he graphitic nature of the macroporous carbon could improve...

Lithium-sulfur (Li-S) batteries are a promising energy-storage technology owing to their high theoretical capacity and energy density. However, their practical application remains a challenge because of the serve shuttle effect caused by the dissolution of polysulfides in common organic electrolytes. Polysulfide-insoluble electrolytes, such as solvate ionic liquids (ILs), have recently emerged as alternative candidates and shown great potential in suppressing the shuttle effect and improving the cycle stability of Li-S batteries. Redox electrochemical reactions in polysulfide-insoluble electrolytes occur via a solid-state process at the interphase between the electrolyte and the composite cathode; therefore, creating an appropriate interface between sulfur and a carbon support is of great importance. Nevertheless, the porous carbon supports established for conventional organic electrolytes may not be suitable for polysulfide-insoluble electrolytes. In this work, we investigated the effect of the porous structure of carbon materials on the Li-S battery performance in polysulfide-insoluble electrolytes using solvate ILs as a model electrolyte. We determined that the pore volume (rather than the surface area) exerts a major influence on the discharge capacity of S composite cathodes. In particular, inverse opal carbons with three-dimensionally ordered interconnected macropores and a large pore volume deliver the highest discharge capacity. The battery performance in both polysulfide-soluble electrolytes and solvate ILs was used to study the effect of electrolytes. We propose a plausible mechanism to explain the different porous structure requirements in polysulfide-soluble and polysulfide-insoluble electrolytes.