(381i) Engineering Microstructure of Ultra Porous Carbon Aerogels As Advanced H2 Sorbent Carriers

In the face of urgent global challenges such as climate change, escalating energy demands, and security concerns, the shift towards sustainable and low-carbon energy is imperative. Hydrogen, recognized as a versatile and clean energy carrier, holds significant promise as a key facilitator in achieving these objectives. However, H₂ encounters challenges in becoming a reliable energy carrier due to issues related to energy density, ease of storage, and compatibility with existing infrastructure. This paper presents a comprehensive investigation of microstructure engineering in high surface area carbon aerogels to enhance H₂ uptake, addressing a pivotal aspect of H₂ storage applications. This study reports engineering microstructure of ultra microporous carbon aerogels via sol-gel and CO₂-supercritical drying methods as potential H₂ sorbent carriers. Microstructural analysis via N₂, Ar, and CO₂ physisorption measurements revealed that the alteration of microstructure in carbon aerogels through controlled pyrolysis, activation, and pore-forming techniques facilitated the formation of ultra-micropores with favorable confinement effects which enhanced intermolecular interactions across the pore walls towards efficient hydrogen adsorption. The carbon aerogels, regardless of activation methods, exhibited elevated surface areas between 2970-3200 m²/g and pore volumes in the range of 0.7-1.39 cm³/g, with a microporous surface area ranging from 950 to 2610 m²/g. Notably, the double-activated carbon aerogel (DA-CA) demonstrated the highest H₂ storage capacity of 2.1 wt.% and 6.8 g/L under 25 ℃ and 100 bar pressure. At cryogenic temperature (77 K), DA-CA achieved a H₂ storage capacity of 6.8 wt.% and 28 g/L under 100 bar pressure. Among the materials studied, the DA-CA demonstrated the highest working capacities, achieving 3.2 wt.% and 13 g/L under the Pressure-Swing (PS) delivery conditions at 77 K and 100-5 bar pressure, respectively. These findings underscore the pivotal role of porosity and surface chemistry in carbon sorbents for H₂ adsorption.