Selectivity and self-diffusion of CO2 and H2 in a mixture on a graphite surface

Area of Science:

• Materials Science
• Chemical Engineering
• Computational Chemistry

Background:

• Industrial off-gases present a challenge for CO2 capture and H2 separation.
• Developing efficient separation technologies is crucial for environmental and industrial applications.

Purpose of the Study:

• To elucidate the adsorption and diffusion mechanisms of CO2 and H2 on graphite surfaces.
• To evaluate the potential of graphite-based materials for CO2 enrichment in industrial off-gases.

Main Methods:

• Classical molecular dynamics (MD) simulations were employed to model gas adsorption and diffusion.
• Density Functional Theory (DFT) calculations were used to determine interaction energies.
• Simulations covered a temperature range of 250-550 K, simulating industrial conditions.

Main Results:

• CO2 exhibits a binding energy on graphite approximately three times greater than H2.
• CO2 selectivity over H2 is significantly higher at lower temperatures.
• The self-diffusion coefficient of CO2 is consistently lower than that of H2 across the studied temperature range.

Conclusions:

• Graphite surfaces demonstrate preferential adsorption of CO2 over H2.
• Temperature plays a critical role in modulating CO2/H2 selectivity.
• Carbon molecular sieve membranes show promise for effective CO2 enrichment from industrial off-gases.