Synthesis of Mesoporous Carbons Using Ordered and Disordered Mesoporous Silica Templates and Polyacrylonitrile as Carbon Precursor

Abstract

Mesoporous carbons were synthesized from polyacrylonitrile (PAN) using ordered and disordered mesoporous silica templates and were characterized using transmission electron microscopy (TEM), powder X-ray diffraction, nitrogen adsorption, and thermogravimetry. The pores of the silica templates were infiltrated with carbon precursor (PAN) via polymerization of acrylonitrile from initiation sites chemically bonded to the silica surface. This polymerization method is expected to allow for a uniform filling of the template with PAN and to minimize the introduction of nontemplated PAN, thus mitigating the formation of nontemplated carbon. PAN was stabilized by heating to 573 K under air and carbonized under N2 at 1073 K. The resulting carbons exhibited high total pore volumes (1.5-1.8 cm3 g(-1)), with a primary contribution of the mesopore volume and with relatively low microporosity. The carbons synthesized using mesoporous templates with a 2-dimensional hexagonal structure (SBA-15 silica) and a face-centered cubic structure (FDU-1 silica) exhibited narrow pore size distributions (PSDs), whereas the carbon synthesized using disordered silica gel template had broader PSD. TEM showed that the SBA-15-templated carbon was composed of arrays of long, straight, or curved nanorods aligned in 2-D hexagonal arrays. The carbon replica of FDU-1 silica appeared to be composed of ordered arrays of spheres. XRD provided evidence of some degree of ordering of graphene sheets in the carbon frameworks. Elemental analysis showed that the carbons contain an appreciable amount of nitrogen. The use of our novel infiltration method and PAN as a carbon precursor allowed us to obtain ordered mesoporous carbons (OMCs) with (i) very high mesopore volume, (ii) low microporosity, (iii) low secondary mesoporosity, (iv) large pore diameter (8-12 nm), and (v) semi-graphitic framework, which represent a desirable combination of features that has not been realized before for OMCs.

Fabrication and Characterization of Inorganic Silver and Palladium Nanostructures within Hexagonal Cylindrical Channels of Mesoporous Carbon

“…The EISA method made it feasible to regulate pore structures and pore sizes and allowed the preparation of various mesoporous materials from water-insoluble systems, including mesoporous silicas [2,7,8,10,[15][16][17][18], mesoporous resins [3,6,9,11], mesoporous TiO 2 [19][20][21], and mesoporous carbons [2,4,12,16,[22][23][24]. The typical procedure used to prepare ordered mesoporous carbons, so-called "template synthesis" [25][26][27][28][29][30], involves the use of mesoporous silicas as hard templates, impregnation of carbon precursors into their mesochannels, carbonization under an inert gas, and finally dissolving the hard template of the "ordered mesoporous silica" through etching in HF (aq) . Although such template syntheses have been used broadly, they can be ineffective means of fabrication of mesoporous carbons because of the many steps required and complicated processing.…”

Synthesis of Partially Graphitic Ordered Mesoporous Carbons with High Surface Areas

“…To achieve graphitization of ordered mesoporous carbon frameworks, four methods are considered feasible: 1) Choosing an appropriate, easily graphtiized carbon source, such as mesophase pitch, [ 7 , 8 ] polyaromatic hydrocarbons, [ 9 , 10 ] aromatic molecules, [ 10 ] aniline, [ 11 ] or acrylonitrile. [12][13][14] As an example, Ryoo and co-workers [ 9 ] fi rst reported fabrication of nanocast mesoporous graphitic carbons by fi lling Al-containing mesoporous silica (Al-SBA-15) mesochannels with acenaphthene, converting the acenaphthene in situ to mesophase pitch, and then graphitizing it in a special alloy autoclave at 900 ° C and under vacuum. 2) High-temperature ( > 900 ° C) chemical vapor deposition (CVD).…”

Structural Changes of Polyacrylonitrile Film by Catalytic Effects of Nickel Particles under Carbonization Process

“…[16][17][18] Kruk et al prepared mesoporous carbons with sharp distribution pore size from PAN by using ordered and disordered mesoporous silica templates, and the detailed characteristics were investigated. 16 Ryoo also studied the similar structures prepared by using sucrose.…”

“…[16][17][18] Kruk et al prepared mesoporous carbons with sharp distribution pore size from PAN by using ordered and disordered mesoporous silica templates, and the detailed characteristics were investigated. 16 Ryoo also studied the similar structures prepared by using sucrose.17 Giunta et al prepared carbon-silica nanocomposites from the pyrolysis of PAN.18 The carbonization has been carried out for electro-spun thin PAN fibers to pursue smooth thermal stabilization and carbonization as well as to avoid the occurrence of defects and voids within the fibers by chemical reactions under the thermal stabilization and carbonization. [19][20][21][22] Recent studies reported that the composite of PAN and multi-wall carbon nanotubes (MWNTs) were prepared by gelation/crystallization from PAN solution containing MWNTs.…”