Unveiling room temperature hydrogen storage in tubular graphitic carbon nitride with diverse morphologies

The 21st century stands as the hydrogen century, embodying profound possibilities for an economy driven by hydrogen. However, a main obstacle in realizing the hydrogen economy revolves around establishing a secure and efficient method for storing hydrogen. In this work, tubular graphitic carbon nitride (g-C₃N₄) was synthesized for the potential in hydrogen storage. The strategic fabrication of tubular g-C₃N₄ takes shape via three distinctive routes: hydrothermal, thermal condensation, and double calcination. Each pathway yields g-C₃N₄ with varying attributes such as surface area and size, thereby laying the groundwork for an intricate exploration and discussion of their hydrogen storage capabilities. Among the synthesized materials, those obtained through the hydrothermal route (H-g-C₃N₄) exhibited the most substantial dimensions, boasting an impressive length exceeding 10 µm. Conversely, both the thermal condensation-derived nanotubes (T-g-C₃N₄) and their double calcination counterparts (D-g-C₃N₄) displayed similar dimensions, with lengths hovering around 1 µm. It became evident that D-g-C₃N₄ exceeded the results of the other two samples in this aspect, showcasing an elevated BET surface area of 114.2 m²/g. In contrast, H-g-C₃N₄ and T- g-C₃N₄ demonstrated lower surface areas, registering at 59.3 and 70.2 m²/g. Regarding hydrogen storage, all samples were found to be able to adsorb and desorb hydrogen within 5 min. The hydrogen storage of the three distinct materials (H-g-C₃N₄, T-g-C₃N₄, and D-g-C₃N₄), as measured using a Sivert's system under room temperature and 3.7 MPa, manifested as 0.68 wt%, 0.72 wt%, and 0.8 wt%, respectively. This observed variation in storage capacity potentially found a correlation with the distinctive morphologies of the three materials. Despite the current hydrogen storage capacities of these materials being below 1 wt%, their inherent potential remains considerable. Achieving further advancements in fabrication techniques to enhance nanotube purity and reduce their size holds the promise of substantially augmenting their capacity for hydrogen storage.