Hydrate-based H2 storage with porous materials as heterogeneous promoters: state of the art and challenges

Clathrate hydrates, which can store hydrogen inside crystalline, ice-like structures, have great potential for hydrogen storage. However, kinetic and thermodynamic promoters are often needed to improve the formation rates and stability ranges. Porous materials exhibit significant potential for hydrate-based hydrogen storage by modulating the kinetics, stability, and storage capacity, unlocking substantial application prospects. This review systematically elucidates the critical mechanisms through which porous materials influence hydrogen hydrate behavior, with a comprehensive analysis of the synergistic roles of material properties and engineering operation conditions. Material properties include the nano-confinement effect, which markedly enhances hydrate formation, optimized pore and particle sizes that increase contact area, functionalized surfaces and rough structures that improve nucleation and stability, and moderate hydrophobicity that enhances gas-water contact. Engineering operation conditions involve maintaining suitable temperatures and pressures to ensure stable hydrate formation, uniform spatial layouts to optimize gas diffusion, and water saturation control to boost reaction efficiency. The review further summarizes the application characteristics of various porous materials, including carbon-based materials (e.g. activated carbon), inorganic materials (e.g. silica), organic porous polymers (e.g. polyurethane foam), and hybrid materials (e.g. metal-organic frameworks), evaluating their respective strengths, limitations and suitability. Multiscale insights highlight the macroscopic focus on hydrate formation within high-pressure reactors, the mesoscopic emphasis on optimizing particle surface reactions, and the microscopic attention to confined hydrate growth within pore structures. Future research should prioritize the refinement of nanopore architectures, the development of advanced hydrophilic/hydrophobic materials, the enhancement of reactor designs, and the integration of thermal management and kinetic optimization to propel hydrogen hydrate storage technology toward practical implementation.