Exploring CO₂ @sI Clathrate Hydrates as CO₂ Storage Agents by Computational Density Functional Approaches

Area of Science:

• Materials Science
• Computational Chemistry
• Physical Chemistry

Background:

• Clathrate hydrates are crystalline solids formed by water trapping guest molecules.
• Understanding the structural stability of clathrate hydrates is key for technological applications, particularly for gas storage.
• Carbon dioxide (CO2) clathrate hydrates are of interest for long-term carbon capture and storage.

Purpose of the Study:

• To computationally investigate the energetic stability of CO2 within the sI clathrate hydrate structure.
• To analyze the interactions governing guest-host stability in CO2@sI clathrates.
• To assess the performance of various computational methods for studying clathrate hydrate systems.

Main Methods:

• First-principles electronic structure calculations were employed.
• Aperiodic and periodic models were used to simulate guest-free and CO2-filled clathrate cages.
• Various density functionals with dispersion corrections were evaluated to determine binding and cohesive energies.

Main Results:

• Encapsulation of CO2 into guest-free sI cages is energetically favorable across most tested functionals.
• Dispersion corrections are crucial for accurately describing non-covalent interactions and stabilizing CO2@sI energies.
• The PW86PBE functional with XDM or D3(BJ) dispersion corrections accurately reproduced experimental lattice constants and described guest-host interactions.

Conclusions:

• The CO2@sI clathrate hydrate structure is energetically favored, whether considering individual cages or the entire unit cell.
• Preferential orientation of CO2 molecules within the sI cages enhances hydrate stability.
• These findings provide high-quality data for data-driven model research and inform strategies for stabilizing CO2 storage materials.