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

## TL;DR

This paper shows how adjusting the surface wettability of porous activated carbon can optimize hydrogen and methane storage in clathrate structures.

## Contribution

The study identifies a specific wettability window that maximizes clathrate formation and gas storage in nanoporous carbons.

## Key findings

- Optimal clathrate formation occurs at moderate hydrophilicity (water contact angle ≈ 43°).
- A dual-storage mechanism combines micropore physisorption and meso/macropore enclathration to enhance gas storage.
- Tunable wettability and porosity provide experimentally testable design rules for hydrogen and methane storage materials.

## Abstract

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.