The interlayer cohesive energy of graphite from thermal desorption of polyaromatic hydrocarbons

TL;DR

This study measures the interlayer cohesive energy of graphite by analyzing the thermal desorption of various polyaromatic hydrocarbons, revealing a higher cleavage energy than previously reported.

Contribution

It provides new experimental values for the interlayer cohesive energy of graphite using thermal desorption spectroscopy of PAHs.

Findings

Interlayer cohesive energy of graphite is approximately 52 meV per carbon atom.

Cleavage energy of graphite is about 61 meV per atom, higher than earlier estimates.

Desorption kinetics vary with PAH size, indicating different island stability behaviors.

Abstract

We have studied the interaction of polyaromatic hydrocarbons (PAHs) with the basal plane of graphite using thermal desorption spectroscopy. Desorption kinetics of benzene, naphthalene, coronene and ovalene at sub-monolayer coverages yield activation energies of 0.50 eV, 0.85 eV, 1.40 eV and 2.1 eV, respectively. Benzene and naphthalene follow simple first order desorption kinetics while coronene and ovalene exhibit fractional order kinetics owing to the stability of 2-D adsorbate islands up to the desorption temperature. Pre-exponential frequency factors are found to be in the range $10^{14}$-$10^{21} s^{-1}$ as obtained from both Falconer--Madix (isothermal desorption) analysis and Antoine's fit to vapour pressure data. The resulting binding energy per carbon atom of the PAH is $52\pm$5 meV and can be identified with the interlayer cohesive energy of graphite. The resulting cleavage energy of graphite is $61\pm5$~meV/atom which is considerably larger than previously reported experimental values.