Abstract
A series of graphite oxide samples were prepared using the modified Hummers method. Flake graphite was used as the raw material and the reaction temperature of the aqueous solution was changed (0 °C, 30 °C, 50 °C, 60 °C, 70 °C, 80 °C, and 100 °C). X-ray diffraction, Fourier-transform infrared spectroscopy, Raman spectral analysis, X-ray photoelectron spectroscopy, and contact angle tests were performed to characterize the structure, chemical bonding, type, and content of oxygen-containing functional groups of the graphite oxide samples. The results showed that the type and content of each oxygen-containing functional group could be controlled by changing the reaction temperature with the addition of water. As the temperature of the system increased, the degree of oxidation of the graphite oxide samples first increased and then decreased. Too high a temperature (100 °C) of the system led to the formation of epoxy groups by the decomposition of some hydroxyl groups in the samples, causing the reduction of oxygen-containing functional groups between the graphite layers, poor hydrophilic properties, and low moisture content. When the system temperature was 50 °C, the interlayer spacing of the graphite oxide samples was at its highest, the graphite was completely oxidized (C/O = 1.85), and the oxygen-containing functional groups were mainly composed of hydroxyl groups (accounting for approximately 28.88% of the total oxygen-containing functional groups). The high content of hydroxyl and carboxyl groups had good hydrophilic ability and showed the highest moisture content. The sample at 50 °C had better sensitivity to ammonia because of its high hydroxyl group and carboxyl group content, with the sample showing an excellent profile when the ammonia concentration was 20–60 ppm.
Highlights
IntroductionGraphene is a novel two-dimensional carbon material that has attracted a great deal of attention in recent years due to its unique electronic structure [1,2,3] and excellent optoelectronic properties [4,5,6,7]
Results from the hydrophilic tests of the graphite oxide samples prepared at different reaction
The surface of graphite oxide is rich in oxygen-containing functional groups
Summary
Graphene is a novel two-dimensional carbon material that has attracted a great deal of attention in recent years due to its unique electronic structure [1,2,3] and excellent optoelectronic properties [4,5,6,7]. Researchers have studied the physical and chemical properties of graphite oxide and found that the surface of graphite oxide is hydrophilic [33,34] owing to its large number of polar groups, the large number of hydroxyl groups gives the oxide an excellent ion-exchange performance [35,36], and different oxygen-containing groups of graphite oxides show excellent gas sensitivity to specific gases [37,38,39]. To further investigate the influence of water temperature conditions on the structural characteristics and surface functional groups of graphite oxide, the modified Hummers method was used to prepare a series of graphite oxide samples with different oxygen functional groups by controlling the reaction temperature during the water addition stage. The present study looked at the changes in structure, chemical bonding, content, and type of oxygen-containing functional groups to achieve accurate and controllable content and type of oxygen-containing functional groups of graphite oxide
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