(222b) Engineering Microstructure of Ultra Porous Carbon-Based Nanomaterials As Advanced H2 Sorbent Carriers

In the face of pressing global concerns such as climate change, escalating energy demands, and security issues, the imperative shift towards sustainable and low-carbon energy sources is undeniable. Hydrogen, recognized as a versatile and clean energy carrier, holds significant promise as a key facilitator in achieving these objectives. However, challenges hinder H₂ from becoming a reliable energy carrier, primarily due to issues related to energy density, storage convenience, and compatibility with existing infrastructure. To surmount these obstacles, adsorptive-based H₂ gas storage (AGS) technologies emerge as a promising avenue, offering a clean, economically viable, and highly sustainable method for adsorbing and desorbing gases under similar conditions. This study focuses on optimizing and engineering carbon-based nanomaterials to augment their hydrogen storage performance. The process involves engineering the structure of several candidates including graphitic carbon nitride (g-C₃N₄) and polymer-derived carbon aerogels through co-polymerization synthesis, exfoliation, controlled pyrolysis, activation, and pore-forming methods in order to establish a highly ultra-porous structure and active sites. The results demonstrate the effectiveness of these methods, with the double-activated carbon aerogel (DA-CA) demonstrated the highest room temperature H₂ storage capacity of 2.1 wt.% and 6.8 g/L at 100 bar pressure owing to its elevated surface area (3,200 m²/g) and ultra-micropore volume (1.23 cm³/g). At cryogenic temperature (77 K), DA-CA achieved a H₂ storage capacity of 6.8 wt.% and 28 g/L under 100 bar pressure. In comparison, exfoliated g-C₃N₄ nanosheets exhibited room temperature gravimetric and volumetric capacities of ~1.8 wt.% and 6.2 g/L, respectively, attributed to a combination of physisorption and chemisorption phenomena, whereas at 77 K, these capacities were enhanced 3.39 and 2.58 times, respectively (ca. 6.1 wt.% and 16 g/L). Furthermore, under the pressure-swing (PS) delivery conditions at 77 K and 100-5 bar, the DA-CA achieved the highest working capacities at 3.2 wt.% and 13 g/L. These results highlight the potential of engineered carbon-based nanomaterials in overcoming challenges and propelling sustainable hydrogen storage technologies forward.