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

Area of Science:

• Materials Science
• Chemical Engineering
• Physical Chemistry

Background:

• Hydrogen clathrate hydrates offer safe solid-state storage but face challenges with slow kinetics and low capacity.
• Nanoporous media, especially activated carbons, improve hydrogen storage, yet interfacial chemistry's role is not fully understood.

Purpose of the Study:

• To identify the optimal interfacial chemistry for enhanced hydrogen and methane clathrate hydrate formation and storage in nanoporous carbons.
• To establish design rules connecting surface wettability and porosity to gas storage performance.

Main Methods:

• Molecular dynamics simulations were employed to investigate H2-CH4 clathrate hydrate formation in nanoporous carbons.
• The study explored the impact of surface wettability, ranging from hydrophobic to hydrophilic, on clathrate stability and gas uptake.
• A dual-storage mechanism involving micropore physisorption and meso/macropore enclathration was analyzed.

Main Results:

• A predictive wettability window was identified, maximizing clathrate formation and stability at moderate hydrophilicity (water contact angle ≈ 43°).
• Optimal wettability minimizes critical pore size for stable enclathration, increasing accessible pore volume and storage capacity.
• A dual-storage mechanism in hierarchical porous media significantly enhances overall gas storage capacity across various surface chemistries.

Conclusions:

• Surface wettability is a critical factor in designing porous materials for efficient hydrogen and methane storage.
• Material design rules linking wettability and porosity to gas storage performance were established.
• Tunable surface functionalization and synthesis offer pathways to optimize porous carbons for advanced gas storage technologies.