| dc.description.abstract | Given the safety and cost issues associated with traditional hydrogen storage systems, this study aims to explore the use of graphitic carbon nitride (g-C3N4) nanotubes as a hydrogen storage material. g-C3N4 nanotubes have emerged as promising candidates due to their unique properties, such as abundant active edges, lightweight structure, and high hydrogen charging and discharging rates. This study focuses on investigating the hydrogen storage properties of ball-milled g-C3N4 nanotubes after microwave irradiation treatment. The aim is to introduce defects and holes in the tube walls during the microwave irradiation process, thereby enhancing hydrogen adsorption.
The samples were ball-milled with ball filling rate of 4.4% and 10%, ensuring thorough mixing, as demonstrated in previous studies. The ball-milled samples were then subjected to microwave irradiation to study the effects of exposure time and material morphology on microwave absorption and subsequent hydrogen storage capabilities.
Microwave irradiation treatments were conducted at moderate power levels (350-500 W) for durations of 4 and 8 minutes. Notably, the BET analysis showed that the 10% ball filling rate sample exhibited optimal micropore generation (2 to 7 nm) after 4 minutes of microwave irradiation. Raman spectroscopy also indicated significant changes in the D band after 4 minutes of irradiation, suggesting the formation of defects within the g-C3N4 structure. These micropores are crucial for enhancing hydrogen ingress into the tubes, thereby improving hydrogen storage. Hydrogen storage tests using Sievert′s method confirmed that the 10% ball filling rate sample outperformed the 4.4% sample, exhibiting a more robust cluster-like morphology and superior microwave absorption characteristics. This led to more efficient micropore formation and improved hydrogen storage performance. For the 10% ball filling rate sample, the hydrogen storage capacity increased from 0.036 wt.% to 0.071 wt.% after 4 minutes of microwave irradiation at 3.7 MPa hydrogen pressure. However, prolonged irradiation (8 minutes) resulted in the destruction of small pores and tubular structures, forming larger pores (>50 nm) and reducing surface area. This effect was especially pronounced in the 4.4% ball filling rate samples, which showed the lowest hydrogen storage capacity (0.0225 wt.%) after 8 minutes of irradiation.
The improvement in hydrogen storage performance is attributed to the generation of defects, pore structure modification, and surface functionalization during the 4-minute microwave treatment. However, longer irradiation times (8 minutes) had detrimental effects on the material structure, likely due to atomic-level damage mechanisms such as welding and coalescence. This study demonstrates the critical importance of precise control over ball milling parameters and microwave irradiation duration in optimizing the hydrogen storage capabilities of g-C3N4 nanotubes. The results suggest that carefully tuned microwave treatments can significantly enhance the performance of these materials in hydrogen storage applications. | en_US |