Tuning the textural properties and surface chemistry of table sugar derived activated porous carbons for improved hydrogen storage

Activated porous carbons have been prepared from commercially available table sugar (sucrose) based on KOH activation. XRD and Raman spectroscopic studies confirmed that increasing KOH to C ratio causes significant disorder in sp2 carbon network. TEM, SAXS and N2 adsorption–desorption studies revealed that the samples consist of micro and meso pores. Presence of oxygen containing functional groups on the surface of these activated carbon samples has been confirmed from EDS, FTIR and XPS studies. The maximum hydrogen storage capacity is as high as 2.3 wt% at 123 K and 45 bar pressure for the sample prepared with KOH:C ratio of four. This has been explained based on its higher micropore surface area and greater micropore volume corresponding to this sample. Adsorption enthalpy for this sample is ~ 10 kJ/mol which is quite high compared to that of a commercially available high surface area activated carbon (AX21) and this high adsorption enthalpy is attributed to the presence of oxygen related functional groups on its surface.