Deciphering Mg-Surface Interactions with Unsaturated Hydrocarbons: An Integrated Experimental-Theoretical Study

Area of Science:

• Surface Science
• Materials Chemistry
• Computational Chemistry

Background:

• Understanding carbonaceous species growth on metal surfaces is crucial for catalysis and materials science.
• Laser-induced processes can initiate surface reactions, but mechanisms require detailed study.

Purpose of the Study:

• To elucidate the mechanism of carbonaceous species formation on magnesium (Mg) surfaces.
• To explain experimental observations of differing deposit quality with ethylene and 1,3-butadiene using theoretical calculations.

Main Methods:

• Combined experimental approach using laser-induced experiments.
• Density functional theory (DFT) calculations for thermodynamic and kinetic analysis of hydrocarbon interactions on Mg(0001).

Main Results:

• 1,3-butadiene (C4H6) leads to clearer, better-structured carbon deposits than ethylene (C2H4) on Mg surfaces.
• DFT calculations show cis-1,3-butadiene binds more strongly to Mg(0001) via [4+2] cycloaddition.
• Lower free energy for dehydrogenation of cis-1,3-butadiene dimers facilitates carbonaceous species growth initiation.

Conclusions:

• The enhanced growth and quality of carbon deposits with 1,3-butadiene are attributed to its stronger binding and more facile dehydrogenation on Mg surfaces.
• DFT calculations successfully explain the experimental findings, highlighting the role of cis-1,3-butadiene's specific isomer and reaction pathway.