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

Abstract

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. Show more