Calorimetric and Raman Spectroscopic Evaluation of Mixed Hydrogen–Methane Hydrates: Applicable to Energy Storage

Safe and cost-effective storage and delivery of hydrogen (H2) remain critical challenges for the establishment of a hydrogen-based economy. Gas hydrates have emerged as a promising medium for H2 storage; however, their application has been limited by the severe operating conditions required for hydrate formation and stability. In contrast, methane (CH4) hydrates can be stabilized at near-ambient temperatures and moderate pressures. This study investigates mixed H2–CH4 hydrates as a potential way to enable hydrogen storage under significantly milder conditions. Phase equilibrium conditions for mixed hydrates of varying compositions were evaluated using a multicell high-pressure differential scanning calorimeter. Experimental findings were further compared with thermodynamic predictions obtained from Multiflash v6.2 employing the CPA-Infochem equation of state. In addition, the hydrate structures were characterized using an inVia Reflex Raman microscope spectrometer. The combined experimental and modeling results provide new insights into the phase behaviors and structural features of mixed H2–CH4 hydrates, highlighting their potential for practical hydrogen storage applications.