Role of Pore Structure Parameters of Clay and Modified Clay Minerals on Their Hydrogen Adsorption at Low- and High-Pressure Conditions

Hydrogen can act as a potential alternative to fossil fuels; however, storage of this energy source is a challenge to overcome. Researchers have been concentrating on geological hydrogen storage in sandstones and shales. Gas in the latter porous rock is primarily stored in the adsorbed phase, to which inorganic minerals, like montmorillonite, illite, and kaolinite, contribute significantly. In this work, the adsorption of gaseous hydrogen on different clay and clay minerals has been studied experimentally at low-pressure–low-temperature (LPLT, 77 K) and high-pressure–high-temperature (HPHT, 313 K) conditions. Further, the pore characteristics of the selected clay samples have been analyzed using low-pressure N₂ (77 K) and CO₂ (273 K) adsorption. Scanning electron microscopy (SEM) images of the samples have been utilized to study their morphology, particle sizes, and pore structures. The role of pore structure parameters on hydrogen adsorption at LPLT and HPHT has been investigated. Through these investigations, it has been found that the specific surface area and micropore volume positively affect hydrogen adsorption and the average pore width affects it negatively. Further, the applicability of some well-known adsorption models, like Langmuir, Freundlich, Toth, and Sips, has been investigated. It has been found that the Langmuir model gives a poor fit in both experimental conditions. The Toth and Sips models are good at LPLT as well as HPHT conditions.