Hydrogen uptake by carbon nanofibers catalyzed by palladium

Carbon nanofibers of herringbone conformation were obtained by chemical vapor deposition on Pd/La2O3 catalyst, from ethylene—hydrogen mixture. After the removal of La2O3, samples with various Pd/C ratios were obtained by oxidation in air. The hydrogen sorption capacities measured gravimetrically at 10 MPa in pure hydrogen, for six different batches of samples, show a good correlation with the Pd/C ratio reveling a catalytic effect of Pd, which supplies atomic H. A possible charge transfer might lead to the increasing of the H uptake with the increasing Pd/C ratio. A saturation value of 1.5% H (mass) per carbon is reached at rather high Pd/C mole ratio (∼1) for nanofibers with 425–455 m2g−1 BET surface area.