Hydrogen adsorption on Pd-modified carbon nanofibres: Influence of CNF surface chemistry and impregnation procedure

Different carbon nanofibre (CNF) based materials (parent, oxidized, and impregnated with a palladium loading of 1 wt.% using different procedures) have been tested for hydrogen storage at ambient pressure. Parent CNF are completely free of oxygen surface groups, whereas treatment in nitric acid increases mainly the amount of surface anhydrides groups. Add to the surface functionalization, the solvent employed in the palladium impregnation was also varied, using both aqueous and organic precursor solutions. Thermogravimetric analyses of the hydrogen adsorption–desorption cycles suggest that the presence of theses functional groups hinders the adsorption. Concerning the presence of palladium, its influence strongly depends on the previous activation of the surface and on the solvent used for the palladium addition. The use of aqueous precursors and functionalized CNFs leads to increases in the adsorption capacity close to 100% compared to the parent CNF (12.6 vs. 6.7 cm3/g).