Effect of long-term aging on graphene oxide: structure and thermal decomposition

FTIR, XRD, Raman, AFM, XPS were used to characterize graphene oxide aged
for 2 years. The results showed that after aging, the C/O ratio of
graphene oxide increased from 1.96 to 2.76, but the type of
oxygen-containing functional groups did not change. In addition to
oxygen-containing functional groups, the content of -CH3, -CH2- and
physically adsorbed water also decreased. The change in the structure is
manifested by the reduction of the average interlayer distance from 1.320
nm to 1.134 nm. Moreover, ID/IG increased from 0.95 to 1.03, indicating
that the defect density in the carbon skeleton increased after aging. The
thermal decomposition process of graphene oxide and its decomposition
products were analyzed by thermogravimetric combined with Infrared
spectroscopy. When the temperature exceeds 60°C, the infrared signal of
CO2 produced by the decomposition of graphene oxide can be detected. After
aging, the decomposition peak temperature of graphene oxide decreased from
216 to 195°C. The amount of CO2 produced in the decomposition products is
almost unchanged, while the amount of CO and H2O produced decreases, and
the amount of SO2 produced decreases significantly. The OH radicals and
heat accumulated during the decomposition process may in turn accelerate
the decomposition rate, leading to a thermal runaway process at 216°C.