Role of microporosity in hydrogen adsorption on templated nanoporous carbons

Casting of inorganic templates is a viable method for obtaining porous carbons with tailored properties and with potential applications in gas adsorption and storage. One of the most used inorganic templates is mesoporous SBA-15 silica, which presents a honeycomb structure, with microporous channels interconnecting mesopores, this three-dimensional structure allowing facile pores filling by the carbon source. In this work, carbon replicas of SBA-15 silica were synthesized by using a sucrose solution as carbon source, and performing carbonization at different temperatures (800, 900 and 1000 degrees C). In all cases, partially graphitic carbons were obtained, with high surface areas and porous volumes, retaining the morphology of the silica template. Since the carbon replica pyrolised at 800 degrees C showed the highest BET surface area, this was chosen for further post-synthesis treatments (physical or chemical) with the aim of improving textural and surface properties. H, adsorption isotherms at 77 K and sub-atmospheric pressure were measured, finding the highest hydrogen uptake, corresponding to 2.0 wt%, with chemically activated sample. Finally, a linear dependence was found between the hydrogen uptake and microporous volumes of the prepared carbons, as measured by the t-plot method, rather than with BET specific surface areas. (C) 2007 Elsevier Inc. All rights reserved.