Novel First-Principles Insights into Graphene Fluorination

TL;DR

This study uses first-principles calculations to analyze graphene fluorination, revealing the role of chemical activation and contaminants in influencing fluorination rates and proposing mechanisms for oxygen desorption at higher temperatures.

Contribution

The paper provides new microscopic insights into graphene fluorination processes, highlighting the impact of chemical activation and contaminants on fluorination kinetics.

Findings

Enhanced fluorine adsorption after half-fluorination.

Chemical activation facilitates contaminant formation, slowing full-fluorination.

Oxygen-fluorine ligands are key contaminants affecting fluorination.

Abstract

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.