High-Resolution Apparatus and Method for Hydrogen Sorption and Transport in Coal for Underground Storage

Summary Hydrogen has emerged as a promising clean energy carrier, and its safe, large-scale storage in geological formations is a critical enabler for a future hydrogen economy. Among potential storage media, coal seams offer both widespread availability and strong gas adsorption capacity. However, the transport mechanisms and limited adsorption capacity of hydrogen in coal remain poorly understood, particularly under dynamic conditions relevant to injection and withdrawal operations. In this study, we developed a novel high-resolution manometric system capable of millisecond-scale pressure acquisition to investigate hydrogen sorption and diffusion processes in coal. Using bituminous coal samples from the King Coal II Mine (San Juan Basin, Colorado), we conducted a series of controlled isothermal experiments to capture pressure-dependent sorption isotherms and real-time transport dynamics. The results reveal a dual-regime sorption behavior characterized by rapid macropore filling and slow micropore diffusion. A dual-site Langmuir–Freundlich model was found to best represent the isotherm behavior across the full pressure range, capturing both energetic heterogeneity and multilayer adsorption effects. Time-resolved effective diffusivity profiles exhibit a power-law decay with time, indicating distributed-lag diffusion in the heterogeneous pore structure of coal. These findings not only deepen our understanding of H2–coal sorption mechanisms but also support the development of predictive models for hydrogen injection, retention, and recovery in CBM and similar tight reservoirs.