Porous carbon xerogels with texture tailored by pH control during sol–gel process

Abstract

Despite commonly accepted ideas, evaporative drying does not always completely destroy the pore texture of phenolic gel. This work shows that very porous carbon materials can be synthesized by evaporative drying and pyrolysis of aqueous resorcinol–formaldehyde gels provided that the operating variables are correctly chosen. Moreover, in this manner monoliths can be easily produced. The pore texture of the materials was studied before and after pyrolysis in order to determine which synthesis and/or pyrolysis variables have an influence on the final texture of the carbon. Results show that it is possible to tailor the morphology of these materials by varying the initial pH of the precursors solution in a narrow range. Micro–macroporous, micro–mesoporous, microporous or totally non-porous carbon materials were obtained. The specific surface area is independent from the initial pH whereas the total void volume varies from 0.4 to 1.4 cm3/g when the initial pH decreases from 6.25 to 5.45. These materials can be used as catalysts supports or for electrochemical applications, the texture control being an interesting advantage.