The hydrogen storage capacity of carbon nano-onions fabricated by thermal chemical vapour deposition

Hydrogen is a promising energy source for resolving the world's energy demands without releasing pollution, but storing hydrogen poses a significant challenge. Carbon materials such as activated carbon (AC), carbon nanotubes (CNT), carbon nanofibers (CNF), carbon nano-onions (CNOs) and graphene are potential substrate materials for hydrogen storage through physisorption/chemisorption due to their large surface areas and the ability to bind hydrogen. We investigate the hydrogen storage capacity of CNOs synthesized through thermal chemical vapour deposition using acetylene in this paper. SEM and XRD analysis revealed that the CNOs are spherical and comprised 18 shells at 850 degrees C and 7 shells at 1000 degrees C. However, the CNO interlayer thickness increased from 3.42 to 3.58 A0, which has a significant impact on the physisorption process. Functionalized CNOs were studied for their hydrogen storage capacities at 77 K and 1.5 atm, demonstrated a hydrogen storage capacity of 18.2%. The BET measurements revealed that the CNOs samples have a surface area of 642 m2/gm and FTIR showed a significant increase in -OH and -CH bond vibrations. Desorption studies of hydrogen reveal primarily two stages. The removal of hydrogen from CNO requires a first-stage activation energy of 6 kJ/mol and a second-stage activation energy of 127 kJ/mol, confirming the presence of both physiosorbed and chemisorbed hydrogen. This study found that hydrogen storage capacity of CNOs is extremely promising, and has a potential for mobile applications.(c) 2023 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.