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 °C and 0.28 wt% at 35 °C. Hydrogen adsorption had a stronger correlation with specific surface area than nitrogen content at the low temperature of −196 °C. At the higher temperature of 35 °C, optimal nitrogen doping enhanced hydrogen adsorption by electronic modification of carbon in agreement with previous theoretical predictions.