Multi-walled carbon nanotubes (MWCNTs) can be utilized for hydrogen storage as they are cost-effective, environmentally acceptable, and exhibit excellent performance in adsorption and desorption processes. a novel technique for the purification of multi-walled carbon nanotubes for H2 storage purposes.
Hydrogen as an Eco-Friendly Energy Source and CNTs for Hydrogen Storage
1.Hydrogen as a Renewable Energy Source: Hydrogen is considered an environmentally safe and cost-effective option for meeting the rising energy demands due to population growth and environmental concerns.
2.Challenges in Hydrogen Storage: Hydrogen can be stored in three forms: compressed gas, cryogenic liquid, and solid-state. However, all these forms present significant storage and transportation challenges.
3.Solid-State Hydrogen Storage: Due to financial and safety concerns, research is focused on solid-state hydrogen storage, where hydrogen is stored by adsorption and desorption in metals and alloys.
4.CNTs for Hydrogen Storage: Carbon nanotubes (CNTs), known for their large surface area and low mass concentration, are promising materials for hydrogen storage through adsorption and desorption processes.
5.Limitations of CNTs: Current CNTs do not meet the hydrogen storage criteria set by the U.S. Department of Energy (DoE), as the growing techniques and conditions affect their adsorption and desorption capabilities, resulting in poor storage performance.
6.Purification of Multi-Walled CNTs: Multi-walled CNTs (MWCNTs) are often contaminated with metallic catalysts and carbonaceous elements due to synthesis processes, necessitating purification.
7.Purification Method: The study used aerosol-assisted chemical vapor deposition (AACVD) to generate MWCNTs, followed by purification using hydrofluoric acid (HF) and hydrochloric acid (HCl) to remove contaminants.
8.Characterization and Results: Purified MWCNTs showed a significant increase in specific surface area, with minimal defects and a crystalline structure in the graphene sheets, as confirmed by XRD, Raman tests, and TEM examinations.
9.Improved Hydrogen Storage: Purified MWCNTs demonstrated better hydrogen adsorption properties compared to un-purified CNTs due to their enhanced structure and minimal flaws.
10.Performance and Limitations: Although purified MWCNTs showed good hydrogen storage capacity at higher pressures, their performance at low pressures did not meet the DoE standards for static and mobile systems. The highest hydrogen storage capability was found to be 3.48 wt% at 12.79 kPa.
11.Future Research: The novel purification technique for MWCNTs suggests potential for further research and improvement in CNT-based hydrogen storage applications, aiming to meet energy storage standards and enhance efficiency.