Protic ionic liquids and salts as versatile carbon precursors.

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.

Optimization of Pore Structure of Cathodic Carbon Supports for Solvate Ionic Liquid Electrolytes Based Lithium-Sulfur Batteries.

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.

Protic-salt-derived nitrogen/sulfur-codoped mesoporous carbon for the oxygen reduction reaction and supercapacitors.

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.