Manipulating active sites on carbon nanotube materials for highly efficient hydrogen storage

The paper has firstly reported an effective, simple and controllable strategy to realize appropriate hydrogen diffusion and hydrogen adsorption in CNT based material, simultaneously. The highest H2 storage capacity was about 7.4 wt%, this materials displaying stable cycles for more than 20 times. The dispersion and active sites of CNT can be controlled by adjusting grafted hydroxyl, amide groups. Amide groups of several configurations would be introduced into CNT by amide reacting with hydroxyl, contributing to the strong hydrogen bonds and electrostatic interactions between CN bond of amide and carbonyl of PLLA. CNT grafted with hydroxyl and acylamino that lead to metal ions dispersing uniformly, contributing to Ni or La2O3 nanoparticles dispersed in CNT, thus providing more active sites for hydrogen adsorption. PLLA only promoted CNT dispersion, and not beneficial to hydrogen absorption/ desorption cycle due to the movement of PLLA chain during hydrogen sorption process. This well explains the mechanism of the excellent H2 adsorption and desorption performance of CNT based materials. [Display omitted] •λ The N-CNT-La2O3 and fg-Ni-CNT-PLLA have about H2 storage capacityof 7.4 wt% and 6.2 wt%, respectively.•λ The electron donating effect of metal would be favorable for the interactions between PLLA and Ni-CNT.•λ PLLA chain would be moved and not beneficial to hydrogen adsorption/desorption cycle. The active sites in porous carbon nanotube (CNT) would determine hydrogen storage performance of CNT. Here, we reported an effective, simple and controllable strategy to improve the hydrogen storage property of function group grafted CNT (fg-CNT). N-CNT-M (La2O3, Ni) would be obtained by the mixture of fg-N-CNT and metallic precursor at calcination of 600 °C. N-CNT-La2O3 has the highest H2 storage capacity of 7.4 wt%, displaying stable hydrogen adsorption/ desorption cycles for more than 20 times at 100 °C and 18 bar. fg-Ni-CNT-PLLA were formed by electrostatic interactions between CN bond of amide and carbonyl of l-polylactic acid (PLLA). fg- Ni-CNT-PLLA also has H2 storage capacity of 6.2 wt% at 100 °C and 18 bar. The experiment found that metal ions or PLLA might be dispersed uniformly in CNT by adjusting the ratio of grafted hydroxyl (OH) to acylamino (–CONH2). N-CNT-La2O3 has better hydrogen storage performance than fg-CNT-PLLA because the aggregation of CNT would be caused by the molecular movement of PLLA during hydrogenation and dehydrogenation. This work