Assessment of hydrogen adsorption capacities on low-maturity shales for geological storage applications: a lattice density functional theory approach
Zheng Rong, Ke Hu, Ying Wu, Xiaochen Li, G. R. Li
Abstract
Large-scale underground storage of hydrogen is widely recognized as an important solution for energy transition to mitigate global warming. To assess H 2 storage in low-maturity shale, lacustrine samples from the North Jiangsu Basin in eastern China were characterized. The pore structure was first visualized using scanning electron microscopy, while the quantitative pore size distribution (PSD) was determined through low-temperature argon adsorption analysis. High-pressure hydrogen adsorption experiments (50–100 °C, 0–190 bar) were then conducted, and the results were interpreted using a lattice density functional theory (LDFT) model. By incorporating PSD data into the LDFT framework, the model successfully captures the variation in H 2 adsorption across pore sizes and quantifies the contributions of micropores and mesopores to the overall adsorption capacity. The maximum excess adsorption capacity (n ex ) of hydrogen ranged from 36.03 to 54.94 μmol/g at 50 °C, increasing with total organic carbon content and decreasing with temperature. The limiting heat of adsorption ranges from 11.81 to 12.29 kJ/mol. The PSD-LDFT model accurately reproduces the adsorption isotherms across a range of pore sizes and temperatures, highlighting the dominant contribution of micro- and mesopores to the overall adsorption capacity. Modeling results indicate that macropores contribute negligibly to H 2 adsorption, while micropores significantly affect interaction energies and adsorbed-phase densities. In micropores, adsorption occurs mainly through complete pore filling, underscoring the importance of pore size variations in adsorption evaluation.