Adsorption energies and prefactor determination for CH3OH adsorption on graphite

Area of Science:

• Surface Science
• Physical Chemistry
• Materials Science

Background:

• Adsorption and thermal desorption are crucial for understanding surface interactions.
• Quantitative parameters like adsorption energy (Eads) and prefactor (ν) govern desorption kinetics.
• Intercomparison of studies is challenging due to the interconnectedness of Eads and ν in low coverage regimes.

Purpose of the Study:

• To independently determine quantitative parameters governing methanol desorption from graphite.
• To establish a reliable method for extracting adsorption energy and prefactor values across various methanol coverages.
• To investigate the structural behavior of methanol on graphite surfaces.

Main Methods:

• Utilized experimental desorption curves at different heating rates.
• Developed a method to independently determine average adsorption energy and prefactor.
• Applied a first-order kinetic law considering adsorption energy distribution for submonolayer analysis.

Main Results:

• For methanol multilayers on graphite, Eads = 430 meV and ν = 5 × 10^14 s⁻¹.
• For methanol submonolayers, Eads = 470 ± 30 meV and ν = (8 ± 3) × 10^16 s⁻¹.
• These parameters remained consistent from 0.09 ML to 1 ML, indicating island formation.

Conclusions:

• The study successfully derived independent adsorption energy and prefactor values for methanol on graphite.
• Methanol molecules exhibit island-like structures on graphite surfaces, even at low initial coverages.
• The developed method enhances the reliability and intercomparability of desorption studies.