Structure Evolution of Graphene Oxide during Thermally Driven Phase Transformation: Is the Oxygen Content Really Preserved?

TL;DR

This study investigates how mild annealing affects the structure and oxygen functionalities of graphene oxide, revealing that oxygen content is not preserved but undergoes transformation, leading to property enhancement.

Contribution

It provides new insights into the structural evolution and oxygen functional group transformation in GO during mild annealing, supported by experiments and density functional theory calculations.

Findings

Oxygen functionalities transform during annealing.

Oxygen content is not fully preserved, but slightly reduced.

Both diffusion and transformation of oxygen groups influence GO properties.

Abstract

A mild annealing procedure was recently proposed for the scalable enhancement of graphene oxide (GO) properties with the oxygen content preserved, which was demonstrated to be attributed to the thermally driven phase separation. In this work, the structure evolution of GO with mild annealing is closely investigated. It reveals that in addition to phase separation, the transformation of oxygen functionalities also occurs, which leads to the slight reduction of GO membranes and furthers the enhancement of GO properties. These results are further supported by the density functional theory based calculations. The results also show that the amount of chemically bonded oxygen atoms on graphene decreases gradually and we propose that the strongly physisorbed oxygen species constrained in the holes and vacancies on GO lattice might be responsible for the preserved oxygen content during the mild annealing procedure. The present experimental results and calculations indicate that both the diffusion and transformation of oxygen functional groups might play important roles in the scalable enhancement of GO properties.