Tunable tetrahydrofuran saturation governs pore-scale wetting and storage-pathway control in hydrate-based hybrid hydrogen storage systems.

HYPOTHESIS: Hydrogen storage in activated carbons (ACs) via hydrate-based hybrid systems is governed by pore-scale wetting and interfacial phenomena rather than pore structure alone. We hypothesize that tetrahydrofuran (THF) saturation controls capillary-driven liquid redistribution across micro-, meso-, and macropores, thereby modulating interfacial accessibility and governing the redistribution of H2 among adsorption, pore-confined gas-phase compression, and hydrate-associated contributions.

EXPERIMENTS: Three ACs with distinct pore hierarchies (RLY-1700, CY-1500, and MES-80) were systematically loaded with 5.56 mol% THF solution at saturation levels ranging from 0 to 1. Hydrogen storage experiments were conducted at 9 MPa and 273.8 K. Pressure-time evolution, combined with pore-scale occupancy analysis and morphology observations, was used to resolve storage contributions and to map structure-saturation-performance relationships.

FINDINGS: THF saturation induces a transition in pore-scale wetting from dispersed nanoclusters to semi-continuous films and finally to fully connected liquid domains, fundamentally altering interfacial accessibility and mass transport. At low saturation (0.25), an optimal balance is achieved through enhanced gas-liquid-solid interfacial area and preserved gas accessibility. For RLY-1700, adsorption, pore-confined gas-phase compression, and hydrate-associated contributions account for 46%, 34%, and 20% of the total H2 uptake, with 28.42 mol% conversion of water to hydrate and 0.19 wt% gravimetric hydrate-based storage capacity. Increasing saturation progressively suppresses adsorption and compression through pore flooding, while promoting hydrate-dominated regimes at high saturation. These results establish THF saturation as a pore-wetting switch that governs interfacial processes and pathway competition in confined hydrogen storage systems, providing a framework for designing colloidally structured porous media for energy storage applications.