Optimizing Surface Wettability for Confined H₂-CH₄ Clathrates in Porous Activated Carbon

Hydrogen (H₂) clathrate hydrates are emerging solid-state media for safe and efficient hydrogen storage, yet practical deployment is hindered by slow formation kinetics and limited storage capacities under mild conditions. Confinement within nanoporous media, particularly activated carbons, substantially alleviates these limitations, but the governing role of interfacial chemistry remains unclear. Here, molecular dynamics simulations identify a predictive wettability window that maximizes binary H₂-CH₄ clathrate formation, stability, and gas uptake in nanoporous carbons, with optimal performance at moderate hydrophilicity (water contact angle ≈ 43°). This optimum arises from a balance between excessive interfacial-water ordering at strongly hydrophilic surfaces and gas-water phase separation at strongly hydrophobic surfaces. At this wettability, the critical pore size required for stable enclathration is minimized, expanding the clathrate-accessible pore volume and enabling higher gas storage capacity. Furthermore, a dual-storage mechanism in hierarchical porous media is demonstrated across a broad range of surface chemistries, integrating micropore physisorption with meso/macropore enclathration to significantly enhance gas storage capacity. These findings yield experimentally testable material design rules that connect surface wettability and porosity to gas storage performance. Because wettability and porosity are tunable via surface functionalization and synthesis conditions, these rules directly inform the design of porous carbons and related materials for hydrogen and methane storage technologies.