Promoting thermodynamic stability of hydrogen hydrates with gas-phase modulators for energy-efficient blue hydrogen storage

As the global climate crisis intensifies with rising carbon dioxide (CO2) concentrations, blue hydrogen (H2) produced through the integration of CO2 capture technologies is emerging as a promising alternative energy source and is challenging traditional fossil fuels in the de-fossilization paradigm. Gas hydrate could be one of the feasible storage medium for energy-efficient H2 storage, due to its potential for eco-friendly features and high H2 storage capacity. However, extreme thermodynamic formation conditions for pure H2 hydrate need to be mitigated for practical application. Here, we demonstrate a novel approach by blending a ‘gas-phase modulator’ with H2, specifically a C2H6 (70%) + C3H8 (30%), to enable hydrate-based H2 storage under moderate thermodynamic formation conditions. In this study, we systematically examined thermodynamic stability, crystallographic structure, guest occupation behavior, and the formation kinetics of the C2H6 + C3H8 + H2 hydrates by varying the H2 composition. The results revealed that the C2H6 + C3H8 mixture played a notable role in promoting thermodynamic formation condition of H2 hydrates. The mixed C2H6 + C3H8 + H2 hydrates were predominantly comprised of sII hydrate, with small amount of sI hydrate. Considering the small to large cage ratio of sI and sII hydrate, this observation indicates a significant advantage for H2 storage due to primarily occupation behavior of H2 into the small cages. In addition, as the H2 composition in the feed gas increased, we confirmed that not only that H2 storage in the hydrate was enhanced but also that the degree of the H2 enclathration ratio into the hydrate was elevated. Moreover, the maximum composition of H2 in the C2H6 (14%) + C3H8 (6%) + H2 (80%) hydrate was 44.37%. Hence, we believe that our findings can contribute valuable insights into the potential application of gas-phase modulators for hydrate-based H2 storage, we emphasize that C2H6 + C3H8 can act as a potential gas-phase modulator for energy-efficient H2 storage.