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 °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 °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. H2 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.