The production of highly stable, defect-free, and electrically
conducting 3D graphene structures from graphene oxide precursors is
challenging. This is because graphene oxide is a metastable material
whose structure and chemistry evolve due to aging. Aging changes the
relative composition of oxygen functional groups attached to the graphene
oxide and negatively impacts the fabrication and properties of reduced
graphene oxide. Here, we report a universal strategy to reverse the
aging of graphene oxide precursors using oxygen plasma treatment.
This treatment decreases the size of graphene oxide flakes and restores
negative zeta potential and suspension stability in water, enabling
the fabrication of compact and mechanically stable graphene aerogels
using hydrothermal synthesis. Moreover, we employ high-temperature
annealing to remove oxygen-containing functionalities and repair the
lattice defects in reduced graphene oxide. This method allows obtaining
highly electrically conducting graphene aerogels with electrical conductivity
of 390 S/m and low defect density. The role of carboxyl, hydroxyl,
epoxide, and ketonic oxygen species is thoroughly investigated using
X-ray photoelectron and Raman spectroscopies. Our study provides unique
insight into the chemical transformations occurring during the aging
and thermal reduction of graphene oxide from room temperature up to
2700 °C.