Hydrogen adsorption on nitrogen-doped carbon xerogels

Nitrogen-doped (1.2-4.5 wt%) carbon xerogels were synthesized from carbonization of resorcinol-formaldehyde polymer in an ammonia atmosphere at various temperatures. The textural properties and the chemical nature of nitrogen in the nitrogen-doped carbon xerogels were analyzed by Ar adsorption/desorption isotherms and X-ray photoelectron spectroscopy, respectively. The maximum hydrogen uptakes were measured to be 3.2 wt% at -196 degrees C and 0.28 wt% at 35 degrees C. Hydrogen adsorption had a stronger correlation with specific surface area than nitrogen content at the low temperature of -196 degrees C. At the higher temperature of 35 degrees C, optimal nitrogen doping enhanced hydrogen adsorption by electronic modification of carbon in agreement with previous theoretical predictions. (C) 2009 Elsevier Ltd. All rights reserved.