Hydrogen storage in subsurface porous media: Mechanisms, challenges, and safety

Underground Hydrogen Storage (UHS) represents a pivotal pathway for establishing a global hydrogen economy and decarbonizing energy infrastructure, yet its practical efficacy remains constrained by complexities in hydrogen microscopic storage and transport mechanisms within subsurface reservoirs. Our review examines H₂ adsorption and diffusion processes in subsurface porous media, integrating a comprehensive experimental framework for diffusion coefficient measurement. The results indicate that H₂ adsorption is predominantly physical, with capacity modulated by temperature, pressure, moisture, reservoir properties, and competitive adsorption with CH₄; Diffusion exhibits multiple mechanisms and influencing factors behavior, where H₂ diffusivity exceeds that of CH₄ and CO₂ by orders of magnitude—though this enhances caprock leakage risks. Optimizing reservoir parameters and ensuring caprock integrity can substantially enhance UHS efficiency and operational safety. Nevertheless, future work must investigate long-term H₂ depletion behavior and H₂- fluid-rock interactions.