Physically Activated Resorcinol-Formaldehyde Derived Carbon Aerogels for Enhanced Hydrogen Storage

Abstract

Carbon aerogels have great potential as hydrogen storage materials owing to their exceptional specific surface area, low weight, and high porosity. These characteristics improve the ability to increase hydrogen adsorption capacity, making them promising candidates for hydrogen storage materials. Nevertheless, the implementation encounters obstacles such as limited storage capacity under ambient temperature and pressure. The present study reports the improved hydrogen storage capacity of carbon aerogels synthesized by Pekala's sol-gel method and optimized by physical activation. This study aims to optimize specific surface area and micropore volumes by physical activation to enhance hydrogen adsorption via the physisorption mechanism. The as-synthesized carbon aerogel has a specific surface area of 579.53 m2/g with a pore volume of 0.34 cm3/g whereas this surface area and pore volume have been tuned using its physical activation. The physically activated carbon aerogel shows a significantly higher specific surface area of 799.68 m2/g with a pore volume of 0.47 cm3/g as compared to the pristine carbon aerogel. This optimization in the specific surface area has enhanced the hydrogen storage capacity of carbon aerogel. The activated carbon aerogel exhibits a promising hydrogen storage capacity of 5.28 wt.% at liquid nitrogen temperature under a hydrogen pressure of 22 atm whereas 3.39 wt.% of hydrogen storage capacity has been seen in the unactivated carbon aerogel under the same conditions. In addition, activated carbon aerogel showed good hydrogen adsorption and desorption kinetics up to 25 cycles at RT (27 oC) under 22 atm H2 pressure. The reason behind enhanced H2 adsorption capacity in activated carbon aerogel has been put forward using various characterization techniques like XRD, TEM, SEM, and BET and discussed in the mechanism section.