Tailoring carbon gels for their use in the energy sector

Abstract

A wide range of synthesis conditions and drying methods were used to prepare mesoporous resorcinol-formaldehyde organic gels, and different carbonisation or activation procedures were used in order to produce new carbon gels with controlled microporosity. As is well known, the mesoporosity of the gels is dependent on the synthesis conditions and type of drying. On the other hand, the results presented here indicate that the microporosity generated during carbonisation is not significantly influenced by the synthesis and drying procedures used, but can be significantly improved by resorting to chemical activation. On carbonisation, low micropore volumes and mean pore widths of about 0.25 cm3 g-1 and <1 nm, respectively, are obtained. KOH activation of a previously carbonised gel increased the micropore volume twofold and increased the micropore width from 0.82 to 1.15 nm, while retaining the mesoporosity of the sample. Even larger increases in micropore volume were obtained by KOH or H3PO4 activation of the non-carbonised organic gels, although with the disappearance of mesoporosity. The pore size was also increased, to 1.17 nm and 2.55 nm in the case of KOH and H3PO4, respectively. The work reported here has stated that it is possible to obtain a variety of different carbon xerogels and aerogels with different microporosity and mesoporosity characteristics, by KOH and H3PO4 chemical activation under different conditions.