Characterization of carbon cryogel synthesized by sol–gel polycondensation and freeze-drying

Babić, Biljana; Kaluđerović, Branka; Vračar, Lj.M.; Krstajić, N.V.

doi:10.1016/j.carbon.2004.05.046

Cited by 81 publications

(39 citation statements)

References 23 publications

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“…Sample CRF0.05 had a surface area close to 780 m 2 g −1 , other samples having values of 670-715 m 2 g −1 . Such values are comparable and sometimes higher than those reported for other carbon cryogels based on resorcinol-formaldehyde [4,16,17].…”

Section: Pore Structure Of Crf Carbon Cryogelssupporting

confidence: 79%

“…RF hydrogels were prepared by polycondensation reaction of resorcinol with formaldehyde in an aqueous solution, basing on the method described elsewhere [16]. In the present case, resorcinol (R) was diluted in distilled water (W) at four different R/W mass ratios: 0.05, 0.1, 0.2 and 0.5, yielding the samples labelled as RF0.05, RF0.1, RF0.2 and RF0.5, respectively.…”

Section: Synthesis Of Carbonaceous Materials Derived From Resorcinol-mentioning

confidence: 99%

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Bimodal activated carbons derived from resorcinol-formaldehyde cryogels

Szczurek

Amaral-Labat

Fierro

et al. 2011

Science and Technology of Advanced Materials

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Resorcinol-formaldehyde cryogels prepared at different dilution ratios have been activated with phosphoric acid at 450• C and compared with their carbonaceous counterparts obtained by pyrolysis at 900• C. Whereas the latter were, as expected, highly mesoporous carbons, the former cryogels had very different pore textures. Highly diluted cryogels allowed preparation of microporous materials with high surface areas, but activation of initially dense cryogels led to almost non-porous carbons, with much lower surface areas than those obtained by pyrolysis. The optimal acid concentration for activation, corresponding to stoichiometry between molecules of acid and hydroxyl groups, was 2 M l −1 , and the acid-cryogel contact time also had an optimal value. Such optimization allowed us to achieve surface areas and micropore volumes among the highest ever obtained by activation with H 3 PO 4 , close to 2200 m 2 g −1 and 0.7 cm 3 g −1 , respectively. Activation of diluted cryogels with a lower acid concentration of 1.2 M l −1 led to authentic bimodal activated carbons, having a surface area as high as 1780 m 2 g −1 and 0.6 cm 3 g −1 of microporous volume easily accessible through a widely developed macroporosity.

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Section: Pore Structure Of Crf Carbon Cryogelssupporting

confidence: 79%

Section: Synthesis Of Carbonaceous Materials Derived From Resorcinol-mentioning

confidence: 99%

Bimodal activated carbons derived from resorcinol-formaldehyde cryogels

Szczurek

Amaral-Labat

Fierro

et al. 2011

Science and Technology of Advanced Materials

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“…There are, at least, four different types of materials named "cryogels": (i) gelatinous precipitate forming during cryoprecipitationblood plasma treatment upon cooling to ca. 4°C [57]; (ii) frozen polymeric or other hydrogels used 14 as antipyretic materials or materials for thermal energy storage [58]; (iii) polymeric and inorganic cryogels produced using sol-gel technology with subsequent freeze-drying including individual and mixed inorganic oxides, polymers, hybrids, composites, and carbon cryogels (the latter is prepared by carbonisation of polymeric cryogels) [59][60][61][62][63][64][65][66][67] There are many cryogels prepared from synthetic polymers such as poly(vinyl alcohol), PVA, which was one of the first polymers used in cryogel preparation [2][3][4]36,38,74,78,82]. PVA alone or in combination with other polymers or proteins is very popular material for the cryogel preparation because its structure containing the (-CH 2 -C(OH)H-) n chain allows various degrees of cross-linking with the participation of the active COH groups, different cross-linkers and co-polymers.…”

Section: Types Of Cryogel Based Composite and Hybrid Materialsmentioning

confidence: 99%

Cryogels: Morphological, structural and adsorption characterisation

Gun'ko

Savina

Mikhalovsky

2013

Advances in Colloid and Interface Science

281

205

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*Graphical Abstract (for review)Cryotripic gelation technique allows the synthesis of solid and soft macroporous gels Textural characterisation of cryogel in native superhydrated state with noninvasive methods Adsorption and diffusion characteristics of macroporous cryogels with respect to macromolecules and cells Theoretical modelling of adsorption from aqueous media *Highlights (for review) Please find the revised manuscript entitled "Cryogels: morphological, structural and adsorption characterisation" by Vladimir M. Gun'ko, Irina N. Savina, Sergey V. Mikhalovsky to re-consider for publication in the "Advances in Colloid and Interface Science"The paper was completely edited and changed according to reviewers comments.Sincerely yours, Prof. V. M. Gun'koCover Letter ABSTRACTExperimental results on polymer, protein, and composite cryogels and data treatment methods used for morphological, textural, structural, adsorption and diffusion characterisation of the materials are analysed and compared. Treatment of microscopic images with specific software gives quantitative structural information on both native cryogels and freeze-dried materials that is useful to analyse the drying effects on their structure. A combination of cryoporometry, relaxometry, thermoporometry, small angle X-ray scattering (SAXS), equilibrium and kinetic adsorption of low and high-molecular weight compounds, diffusion breakthrough of macromolecules within macroporous cryogel membranes, studying interactions of cells with cryogels provides a consistent and comprehensive picture of textural, structural and adsorption properties of a variety of cryogels. This analysis allows us to establish certain regularities in the cryogel properties related to narrow (diameter 0.4 < d < 2 nm), middle (2 < d < 50 nm) and broad (50 < d < 100 nm) nanopores, micropores (100 nm < d < 100 m) and macropores (d > 100 m) with boundary sizes within modified life science pore classification. Particular attention is paid to water bound in cryogels in native superhydrated or freeze-dried states. At least, five states of water -free unbound, weakly bound (changes in the Gibbs free energy G < 0.5-0.8 kJ/mol) and strongly bound (G > 0.8 kJ/mol), and weakly associated (chemical shift of the proton resonance  H = 1-2 ppm) and strongly associated ( H = 3-6 ppm) waters can be distinguished in hydrated cryogels using 1 H NMR, DSC, TSDC, TG and other methods. Different software for image treatment or developed to analyse the data obtained with the adsorption, diffusion, SAXS, cryoporometry and thermoporometry methods and based on regularisation algorithms is analysed and used for the quantitative morphological, structural and adsorption characterisation of individual and composite cryogels, including polymers filled with solid nano-or microparticles.

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“…In the case of Ni electrode, the corresponding Tafel slopes were 55 mV dec -1 at lower current densities and about 259 mV dec -1 at high current densities. Chialvo et al [44] showed that Tafel slope for the OER depended on pretreatment of Ni electrode. In the low overpotential region Tafel slopes were either 80 or 30 mV dec -1 , while in the high overpotential region the Tafel slopes varied between 120 and 190 mV dec -1 , depending on pre-treatment of Ni electrodes [44].…”

Section: Polarization Curvesmentioning

confidence: 99%

“…Chialvo et al [44] showed that Tafel slope for the OER depended on pretreatment of Ni electrode. In the low overpotential region Tafel slopes were either 80 or 30 mV dec -1 , while in the high overpotential region the Tafel slopes varied between 120 and 190 mV dec -1 , depending on pre-treatment of Ni electrodes [44]. Besides the well-known difficulties in determining the mechanism of the OER, related to the impossibility of identifying the intermediate species and the fact that 4 electrons are discharged per one molecule of evolved oxygen, formal approach to the study of the kinetics of this reaction on metal oxides is more complicated due to the uncertain values of the stoichiometric number.…”

Section: Polarization Curvesmentioning

confidence: 99%