Ionic Diffusion in CO_{2} Adsorption by Li_{4}SiO_{4}: Inert-Marker Experiment and DFT Calculations

Area of Science:

• Materials Science
• Chemical Engineering
• Physical Chemistry

Background:

• Carbon dioxide (CO_{2}) capture is crucial for mitigating climate change.
• Lithium silicate (Li_{4}SiO_{4}) shows promise for CO_{2} adsorption.
• The reaction rate is limited by diffusion within the product layer, but the mechanism is unknown.

Purpose of the Study:

• To elucidate the ionic diffusion mechanism during CO_{2} adsorption by Li_{4}SiO_{4}.
• To identify the rate-limiting step in the CO_{2} capture process.

Main Methods:

• Inert-marker experiments using an electron probe.
• First-principles calculations based on density functional theory (DFT).

Main Results:

• Electron probe tests revealed inward movement of platinum (Pt) markers into the product layer.
• Outward transfer of oxide (O^{2-}) and lithium (Li^{+}) ions is identified as the dominant diffusion pathway.
• DFT calculations confirmed O^{2-} and Li^{+} diffusion, with O^{2-} diffusion being the rate-limiting step.

Conclusions:

• The study clarifies the diffusion mechanism in Li_{4}SiO_{4} for CO_{2} capture.
• Understanding this mechanism is key to optimizing Li_{4}SiO_{4} for efficient carbon capture technologies.