Engineering Microstructure of Ultraporous 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 toward sustainable and low-carbon energy is imperative. Hydrogen (H2), 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. We report engineering microstructure of ultramicroporous 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 ultramicropores with favorable confinement effects which enhanced intermolecular interactions across the pore walls toward efficient H2 adsorption. The carbon aerogels, regardless of activation methods, exhibited elevated surface areas between 2970 and 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 (CAT20-F25-KOH) demonstrated the highest H2 storage capacity of 2.1 wt % and 6.8 g/L under 298 K and 100 bar pressure. At cryogenic temperature (77 K) and 100 bar pressure, CAT20-F25-KOH achieved a H2 storage capacities of 6.8 wt % and 28 g/L. These findings underscore the pivotal role of porosity and surface chemistry in carbon sorbents for H2 storage.