Pore Characteristics for Efficient CO₂ Storage in Hydrated Carbons.

Area of Science:

• Materials Science
• Chemical Engineering
• Environmental Science

Background:

• Carbon dioxide (CO2) capture is crucial for mitigating climate change.
• Gas-hydrate crystallization in confined porous media is an emerging CO2 capture technology.
• Pore characteristics significantly influence CO2 capture efficiency.

Purpose of the Study:

• To investigate the impact of pore dimensions and surface functionality of porous carbons (PCs) on CO2 capture efficiency.
• To evaluate CO2 uptake performance in dry and hydrated PCs under high pressure.
• To understand the mechanism behind enhanced CO2 capture capacity in hydrated PCs.

Main Methods:

• Synthesized and characterized porous carbons with varying pore sizes (supermicropores to mesopores) and surface properties (hydrophilic to hydrophobic).
• Imbibed water into PCs and measured CO2 uptake at pressures up to 54 bar.
• Analyzed H2O-to-carbon and H2O/CO2 molar ratios to determine capture efficiency and mechanism.

Main Results:

• Porous carbons with a wide pore size distribution (micropores and mesopores) exhibited significantly higher CO2 capture capacity.
• Achieved a low H2O/CO2 molar ratio of 1.8, surpassing conventional CO2-hydrate formations (5.72).
• CO2 capture in micropores (<2 nm) occurs in gaseous form, blocked by hydrate formations in larger mesopores.
• Microporous/supermicroporous PCs showed no hysteretic CO2 uptake, indicating no hydrate formation within 1-2 nm pores.
• High nitrogen content in PCs inhibited CO2 hydrate formation.

Conclusions:

• A combination of micropores and mesopores in PCs is essential for efficient high-pressure CO2 capture via hydrate-blocking mechanism.
• The developed method offers superior CO2 capture and storage capacity compared to traditional CO2-hydrate systems.
• Surface chemistry, particularly nitrogen functional groups, can be leveraged to control or prevent CO2 hydrate formation.