Carbon Monoliths Possessing a Hierarchical, Fully Interconnected Porosity

Abstract

Nanocasting of carbon replicas of siliceous micro-or mesoporous materials has gained a lot of interest during the last years. Micro-and mesoporous carbons, respectively, are, depending on their pore size, interesting materials for a wide range of applications, including hydrogen storage, doublelayer capacitors, molecular separation, and catalysis. Recently, the synthesis of highly ordered micro-and mesoporous carbons possessing a narrow pore size distribution has been described. [1,2] Here, mesoscopically ordered silica is impregnated with a carbon precursor, which is subsequently carbonized under non-oxidizing conditions. Porous carbons are finally obtained through dissolution of the silica framework. In order to maintain the structural integrity of the thus prepared carbon matrix, the host matrix should have an interconnected porosity. Thus, suitable zeolites, [3] MCM-48, [2,4] SBA-1, [5] mesocellular foams, [6] SBA-15, [7] and HMS [8] (hexagonal mesoporous silica) materials, which all possess a three-dimensional (3D) interconnected porosity, have been found to be suitable template structures. To date, however, most of the carbon materials reported have been obtained as powders, with only a few exceptions. [9] This fact may limit the applicability of these materials when macroscopic morphologies, such as chromatographic columns or membrane reactors, are required. The present communication is, to the best of our knowledge, the first to describe the preparation of monolithic carbon possessing a hierarchical bimodal meso-and macroporosity. In a series of papers, Nakanishi et al. [10] have described a sol±gel synthesis route to monolithic silica possessing a bimodal, hierarchical meso-and macroporous structure. This type of monolith is now commercially available as a chromatographic column under the brand name Chromolith. The key to the synthesis is to balance the kinetics of phase separation versus gelation of the silica under acidic conditions; this can be achieved by the use of either homo-polymers or block co- COMMUNICATIONS

Fabrication and Characterization of Nanotemplated Carbon Monolithic Material

“…Considering the ΔEp value obtained for each modified electrode, the NTCM modified GCE (Figure 7f) resembled the C 60 modified GCE (Figure 7 (b)), whereas the CM modified GCE (Figure 7e) resembled the graphite modified GCE (Figure 7c). Furthermore, the response current to Fe(CN) 6 3−/4− of the NTCM modified GCE (Figure 7f) was higher compared to the CM modified GCE (Figure 7e), implying a higher porosity and surface area of the resulting film.…”

“…Studying the electrochemical performance of such materials is helpful to understand their chemical composition and morphology. 38 With Fe-(CN) 6 3−/4− as a redox probe, the cyclic voltammograms of the modified GCEs exhibited quasi-reversible behavior, as ΔE p (peak separation between the anodic and cathodic peak) was noticeably greater than the theoretical value of 59 mV for a reversible electrochemical process. Considering the ΔEp value obtained for each modified electrode, the NTCM modified GCE (Figure 7f) resembled the C 60 modified GCE (Figure 7 (b)), whereas the CM modified GCE (Figure 7e) resembled the graphite modified GCE (Figure 7c).…”

“…The BDD film has attracted considerable interest in electrochemistry for use as active electrodes due to its superior chemical, physical, and mechanical inertness. Figure 8A (a) shows a cyclic voltammogram of a bare BDD electrode in 0.1 M KCl solution, once again containing Fe(CN) 6 3−/4− (10 mM) as the probe.…”

“…Carbon monoliths (CM) possess an integrated structure, which is much easier to apply to many of the above applications. 6,7 Additionally, CMs often exhibits a controlled pore structure, with interconnected channels within their framework, which additionally provides the benefito fh i g hflow-through permeability. According to International Union of Pure and Applied Chemistry (IUPAC) definitions, mesoporous carbon materials possess pores within the 2−50 nm range, microporous materials have pores of <2 nm, whereas pore size within macroporous carbon are >50 nm.…”

Hierarchical Porosity in Self‐Assembled Polymers: Post‐Modification of Block Copolymer–Phenolic Resin Complexes by Pyrolysis Allows the Control of Micro‐ and Mesoporosity

“…[20,21] Among the various concepts, the template-assisted approach provides a facile way for well-defined structures at different length scales, for a wide range of pore sizes, and for various chemical functionalities. [5,16,[22][23][24] Examples of suitable structure-directing agents include, surfactants or block copolymers, [25][26][27][28][29][30][31] colloids, [32,33] emulsions, [34] polymer gels, [35] vesicles, [36] foams, [13,37] solid particles, and bacteria. [38] By combining different structure-directing agents, the structures can be controlled hierarchically at different independent length scales.…”