  Comprehensive first-principles calculations are performed on diverse
arrangements of relevant chemical defects in fluorographene to provide accurate
microscopic insights into the process of graphene fluorination. The minimum
energy paths for the half- and full-fluorination processes are calculated for a
better understanding of these phenomena. While experimental observations
indicate a much slower rate of the full-fluorination process, compared with the
half-fluorination one, the obtained energy profiles demonstrate much enhanced
fluorine adsorption after the half-fluorination stage. This ambiguity is
explained in terms of significant chemical activation of the graphene sheet
after half-fluorination, which remarkably facilitates the formation of chemical
contaminants in the system and thus substantially slows down the
full-fluorination procedure. After considering the binding energy and
durability of the relevant chemical species, including hydrogen, oxygen, and
nitrogen molecules and xenon atom, it is argued that oxygen-fluorine ligands
are the most likely chemical contaminants opposing the full-fluorination of a
graphene sheet. We propose an oxygen desorption mechanism for the atomic
description of the full-fluorination procedure in realistic situations. It is
argued that the proposed mechanism explains well much enhanced rate of the
full-fluorination procedure at elevated temperatures.

Mesoscale and Nanoscale Physics;Materials Science