Oxidation of graphite surface: the role of water

TL;DR

This study uses density functional calculations to explore how water influences graphite oxidation, revealing different oxidation patterns, defect formation, and the importance of water in intercalation and exfoliation processes.

Contribution

It provides new insights into the role of water in graphite oxidation, highlighting the differences from graphene and the conditions favoring oxidation and defect formation.

Findings

Oxidation of 80% of graphite surface is energetically favorable.

Water presence facilitates epoxy to hydroxyl transformation and exfoliation.

Water-rich conditions lead to early intercalation and oxidation, unlike water-free conditions.

Abstract

Based on density functional calculations, we demonstrate a significant difference in oxidation patterns between graphene and graphite and the formation of defects after oxidation. Step-by-step modeling demonstrates that oxidation of 80% of the graphite surface is favorable. Oxidation above half of the graphite surface significantly decreases the energy costs of vacancy formation with CO2 production. The presence of water is crucial in the transformation of epoxy groups to hydroxyl, the intercalation with further bundle and exfoliation. In water-rich conditions, water intercalates graphite at the initial stages of oxidation and oxidation, which is similar to the oxidation process of free-standing graphene; in contrast, in water-free conditions, large molecules intercalate graphite only after oxidation occurs on more than half of the surface.