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Abstract: Mesoporous carbon gels are usually obtained by pyrolyzing resorcinol–formaldehyde (RF) gels, which are synthesized via the sol–gel polycondensation of resorcinol with formaldehyde in a slightly basic aqueous solution followed by drying. However, mesoporous carbon gels cannot be prepared under the conditions of high catalyst concentration or high pH of RF solution even by using supercritical drying or freeze drying. In this work, mesoporosity of carbon cryogels is improved by ultrasonic irradiation to RF solution. It is found that the gelation time of RF solution becomes greatly short by ultrasonic irradiation and that ultrasonic can improve mesoporosity of carbon cryogels prepared at high catalyst concentration (C/W). Although the carbon cryogels prepared from C/W=80mol/m3 have no mesopores, the carbon sonogels prepared by ultrasonic irradiation under the same catalyst condition have sharp mesopore size distribution. The utilization of ultrasonic in the preparation of RF gel is an interesting way in improving mesoporosity of carbon gels prepared at high C/W or pH. [Copyright &y& Elsevier]

The role of surfactants on carbon cryogels is investigated by using three different surfactants, nonionic (SPAN80), cationic (trimethylstearylammonium chloride; C18) and nonionic polymeric fluorinated (FC4430) surfactants. By using different SPAN80 concentrations (10.0, 5.0, 2.5, 1.0 and 0.5 vol.%), double-structure carbon microspheres with SBET (630–700 m2/g) and Vmes (0.51–0.93 cm3/g) are obtained. Mesoporous carbon cryogels with different SBET and Vmes are prepared by using C18 with different volume ratios of cyclohexane to water in a C18/water/cyclohexane mixture. Carbon cryogels with SBET (690–810 m2/g) and Vmes (0.83–1.74 cm3/g) are obtained when cyclohexane is contained in the mixture, on the contrary, when there is no cyclohexane in the mixture, a water-based carbon cryogel with low SBET (480 m2/g) and Vmes (0.29 cm3/g) is obtained. Carbon cryogels prepared by using C18 have larger mesopore size and broader mesopore size distribution compared with carbon cryogels prepared by using other surfactants. Microcellular (sponge-like) carbon cryogels with mesoporous surface, SBET (210–660 m2/g) and Vmes (0.37–0.92 cm3/g), are obtained by introducing FC4430 (two concentrations) to two starting RF solutions (C/W=6,45). Low FC4430 concentration leads to carbon cryogels with higher SBET (610 and 660 m2/g) and narrower mesopore size distributions compared to the high concentration counterpart. Hence, it is found that different surfactant types have interesting effects on morphologies and porous properties of RF carbon cryogels. [Copyright &y& Elsevier]