F. Pico

Block-Copolymer assisted synthesis of hierarchical carbon monoliths suitable as supercapacitor electrodes

Three dimensional (3D) hierarchical porous (micro-, meso- and macro-porous) carbon monoliths (HCMs) have recently been proposed as promising supercapacitor electrodes. In this work, we have further explored the use of block-copolymers as templates for the preparation of HCMs via condensation of resorcinol and formaldehyde (RF) and subsequent carbonization. The resulting HCMs exhibited a textured morphology consisting of a bicontinuous macroporous carbon network built of interconnected microporous carbon colloids, as demonstrated by nitrogen adsorption/desorption isotherms, mercury porosimetry and electron microscopy, in both scanning and transmission mode. Such a texture favored the performance of HCMs as supercapacitor electrodes, reaching remarkable values of capacitance of up to 198 F g−1 (normalized by mass) and 34.5 μF cm−2 (normalized by BET surface area). The first electrolyte infiltration into the micropore (prior capacitance measurements) was demonstrated to play a crucial role in the achievement of large capacitance values.

Single-Walled Carbon Nanotubes as Electrodes in Supercapacitors

7 pages.-- PACS: 82.47.Uv; 82.45.Fk; 85.35.Kt; 68.43.Mn; 82.45.Yz; 82.45.Gj; 81.40.Gh; 78.30.Na

PPO15-PEO22-PPO15block copolymer assisted synthesis of monolithic macro- and microporous carbon aerogels exhibiting high conductivity and remarkable capacitance

Ultralightweight (specific gravity 5 × 10−2) and highly conductive (2.5 S/cm) monolithic carbon aerogels exhibiting a three-dimensionally continuous micro- and macroporous structure have been prepared through a PPO-PEO-PPO block copolymer assisted route. The resulting carbon aerogels were highly suitable as electrodes of electric double layer capacitors, with remarkable values of capacitance of up to 225 F/g (normalized by mass) and 31 µF/cm2 (normalized by BET surface area).

Phosphate-Functionalized Carbon Monoliths from Deep Eutectic Solvents and their Use as Monolithic Electrodes in Supercapacitors

Porous carbon materials have received considerable attention in the last years because of their outstanding performance as substrates in a number of separation and catalytic processes as well as electrodes in fuel cells, supercapacitors, and batteries. 2] In sustainable terms, these latter electrochemical processes are especially attractive for the future of our society because of their capability to either provide an alternative to combustion of fossil fuels for energy production (e.g. , fuel cells) or to store energy (e.g. , supercapacitors and batteries). Particularly interesting are those nanostructured porous carbon materials or those carbon materials showing three-dimensional (3D) hierarchical porous textures (containing pores at different scales, from micropores to mesopores, up to macropores) that combine high specific surface areas with proper channels, allowing good diffusion of any substance (e.g. , analytes, adsorbates, electrolytes, etc.) to the entire surface of the material. A number of synthetic routes using different carbonaceous precursors in the presence of either hard or soft templates has been explored to date with the aim to control the textural properties of the resulting carbon materials. Among them, the use of ionic liquids (ILs) and deep-eutectic solvents (DESs) is especially interesting in sustainable terms due to their recent application to a number of green processes, both synthetic and catalytic. Sustainability is emphasized with those ILs and DESs capable to play multiple roles (e.g. , from reaction medium to carbonaceous precursors up to structure-directing agents) in the synthetic process and hence, promoting a significant economy of reagents. Thus, ILs and DESs have proved efficient in tailoring not only the textural properties, but also the composition of the resulting carbon materials. For instance, nitrogen-functionalized carbon materials have exhibited a remarkable capacity for CO2 adsorption [9] and they hold much potential as electrodes for supercapacitors. With regard to this application, the use of phosphate-functionalized carbon materials open interesting perspectives because of the widening of the operational voltage window with aqueous electrolytes and the subsequent increase of the energy density that can be attained. However, neither ILnor DES-assisted synthesis have yet been described for the preparation of phosphate-functionalized carbon monoliths (PfCMs). Herein, we describe the preparation of PfCMs by polycondensation of formaldehyde with a resorcinol-based DES—composed of resorcinol, choline chloride, and glycerol—and using phosphoric acid as catalyst. The ternary DES was prepared in a closed container by the complexation of resorcinol, choline chloride, and glycerol in a molar ratio 1:1:1 at 90 8C (see the Experimental Section). The inset in Figure 1 a shows that the resulting DES is a viscous liquid (the static viscosity is 314 cP at 22 8C, as determined by

Deep-Eutectic-Solvent-Assisted Synthesis of Hierarchical Carbon Electrodes Exhibiting Capacitance Retention at High Current Densities

Nature provides a wide range of entities and/or systems with different functions that may serve as a source of bioinspiration for material chemists. Actually, materials exhibiting a 3D porous texture (combining pores at different scales, from macroto mesoup to micropores) mimic the hierarchical structure of different systems found in living organisms (e.g., the blood circulation or the respiratory system in mammalians). Structural organization at different scales is ultimately responsible for the outstanding properties offered by hierarchical materials (not only as stationary phases in separation and catalytic processes, but also as electrodes in fuel cells and capacitors) because they offer not only large surface areas, but also accessibility to such a surface. A number of synthetic routes have been explored by using different carbonaceous precursors and either exo or endo templates to modulate the porous texture of the resulting carbon structures. Recent efforts have also been focused on the preparation of porous carbon composites containing graphitic carbon entities (e.g., carbon nanotubes and nanohorns, or even graphene oxide) the challenge of which is double and resides in 1) the achievement of a homogenous dispersion of these entities throughout the monolith structure and 2) the preservation of high surface areas. Baumann and co-workers have recently performed a quite extensive and stimulating work on single-walled carbon nanotubes (SWCNTs) and double-walled carbon nanotubes (DWCNTs) synthesized by resorcinol–formaldehyde polycondensation. Particularly interesting in terms of conductivity and surface area were those composites based on DWCNTs, although the authors expressed the convenience of substituting the surfactants used for carbon-nanotube (CNT) dispersion. Ionic liquids (ILs) and deep eutectic solvents (DESs, a new class of ILs obtained by complexion of quaternary ammonium salts with hydrogen-bond donors, such as acids, amines, and alcohols) have lately been the solvent of choice in a number of chemical processes because of special features: for example, they are nonreactive with water, nonvolatile, and biodegradable as well as excellent solvents for a wide variety of solutes, such as different substrates, enzymes, and even microorganisms of catalytic and biocatalytic interest. Of particular interest for the purpose of this work are those processes for which the capability both as solvents for CNT dispersion and structure-directing agents in the synthesis of different materials was demonstrated. Actually, ILs and DESs have been used as solvents for preparation of CNT-based carbon composites and even as carbonaceous precursors of both nontextured and textured carbons. In particular, we have recently described the preparation of DESs based on mixtures of resorcinol and choline chloride, the rupture of which (via resorcinol polycondensation and subsequent segregation of choline chloride) resulted in the formation of bimodal porous carbons. In this case, hierarchy was obtained through a synthetic mechanism that combined aspects from those original works used for synthesis of zeolites (i.e., based on DES rupture and controlled delivery of an organic template to the reaction mixture) and those used for synthesis of macroporous structures (i.e. , based on spinodal-like processes) . It is also worth noting the “green” character of the process as a result of the absence of residues and/or byproducts eventually released after the synthetic process, that is, one of the components forming the DES (e.g., resorcinol) becomes the material itself, whereas the second one (e.g., choline chloride) is fully recovered and can be reused in subsequent reactions. Based on these previous results, we considered that the use of DESs could open an interesting path for the preparation of hierarchical porous CNT composites. Herein, we describe the preparation of hierarchical porous multiwalled CNT (MWCNT) composites exhibiting high surface areas and outstanding conductivities through furfuryl alcohol (FA) condensation catalyzed by a protic DES based on complexes of para-toluene sulfonic acid [a] Dr. M. C. Guti rrez, Dr. D. Carriazo, Dr. R. Jim nez, Dr. J. M. Rojo, Dr. M. L. Ferrer, Dr. F. del Monte Instituto de Ciencia de Materiales de Madrid-ICMM Consejo Superior de Investigaciones Cient ficas-CSIC Campus de Cantoblanco, 28049-Madrid (Spain) E-mail : mcgutierrez@icmm.csic.es delmonte@icmm.csic.es [b] Dr. A. Tamayo Instituto de Ceramica y Vidrio-ICV Consejo Superior de Investigaciones Cient ficas-CSIC. Campus de Cantoblanco, 28049-Madrid (Spain) [c] Dr. F. Pic Centro Nacional de Investigaciones Metalurgicas-CENIM Consejo Superior de Investigaciones Cient ficas-CSIC Av. Gregorio del Amo s/n, 28040-Madrid (Spain) Supporting information for this article is available on the WWW under http://dx.doi.org/10.1002/chem.201101679.