Studies of the chemical and pore structures of the carbon aerogels synthesized by gelation and supercritical drying in isopropanol

The carbon aerogels prepared by a new method through gelation and supercritical drying in isopropanol were characterized by X-ray photoelectron spectroscopy (XPS), scanning electron microscopy, and a surface area analyzer. Their chemical structure, morphology, and pore structure are discussed. We found that all of these carbon aerogel (CA-IPA) samples have almost the same carbon and oxygen elemental states, as well as similar oxygen-containing groups. The curve fitting of the C1s XPS spectra of the samples for characterizing oxygen-containing surface groups can be performed by assuming the peak type to be a Gaussian-Lorentzian Cross Product, but we cannot obtain good results using a Gaussian lineshape. When the mass density of the CA-IPA decreases, the mesopores and macropores of the samples are found to grow, but the size and the shape of individual carbon nanoparticles in various CA-IPA samples do not apparently change. The micropore volume of the CA-IPA samples increases with a decrease in the mass density, while the mesopore volume has a maximum at a certain mass density. The CA-IPA samples have a very narrow micropore distribution at about 0.5 nm. The mesopore distribution of the CA-IPA is widened and the average pore size increases as the mass density of the sample decreases.