Onboard hydrogen storage is one of the major hurdles in developing hydrogen fuel cell-powered vehicles. Cryogenic physisorption on nanostructured carbons exhibits the potential to meet the DOE 2010 hydrogen storage capacity target (~ 7 wt%). This research is focused on tailoring the pore structure of lignin-derived activated carbons for hydrogen storage.

A series of nanostructured activated carbons have been synthesized from lignin, a pulp industry waste, by carbonization and activation. Thermogravimetric analysis and pyrolysis-MS studies revealed that CO, CO₂ and H₂O are the primary thermodegradation products during the carbonization process, leading to a high yield of lignin carbon (> 50 wt%). Nanoporous structure is formed and tuned by activating lignin carbon matrix with activating agents CO₂, K₂CO₃ and KOH at a temperature range of 600 to 850 °C. Nitrogen sorption results revealed that activated lignin carbons are highly porous, with the majority of pores having a pore diameter less than 2 nm. Hydrogen uptake at 1 bar and 77 K indicates that high surface area and small pore size facilitate hydrogen uptake. A hydrogen storage capacity of ~ 2.4 wt% (77 K, 1 bar) has been recorded for an activated lignin carbon with a surface area of ~ 2000 m²/g and an average pore diameter of d_DR ~ 1.4 nm.