Porous Carbon-Ice Composite Microscale Vessels for Gas Encapsulation and Storage

Micro- or nanoscale gas vessels decentralize gas storage, enabling high-density gas storage at ambient pressure. However, current materials are constrained by complex designs and the need for intensive production and operational conditions. Here, we demonstrate the use of frozen water (ice) to encapsulate commonly available activated carbon (AC), forming microscale vessels where high-density gas is stored within carbon nanopores. Hydrophilic functional groups on the AC surface create water competition for adsorption sites within the pores, reducing the capacity available for gas molecules. This effect diminishes with increasing gas dosage pressure. At 50 bar, methane (CH₄) dosage, stored at ambient pressure and -20 °C, shows that approximately 90% of the deliverable capacity was retained using this water-assisted method─an amount 320% higher than that achieved with traditional adsorption methods under identical conditions. For low-polarizable gases like nitrogen (N₂) and hydrogen (H₂), competitive adsorption significantly reduced performance; however, heat treatment of AC at 1000 °C in argon (Ar) effectively reduced oxygenated functional groups, resulting in a 32 and 48% increase in deliverable N₂ and H₂ capacities, respectively. This study presents a cost-effective, sustainable approach to gas storage using widely available materials and simple operation, advancing the potential for CH₄ and H₂ storage in clean energy systems.