A kind of method for preparing graphene oxide
Technical field
The present invention relates to a kind of method that adopts solvent-thermal method to prepare graphene oxide at low temperatures, belong to the functional materials preparing technical field.
Background technology
Graphene is a kind of carbonaceous novel material of the cellular crystalline network of individual layer of the tightly packed one-tenth of carbon atom, is a kind of two dimensional crystal, is the elementary cell that makes up other dimension carbonaceous materials (as zero dimension soccerballene, one dimension carbon nanotube, three-dimensional graphite).The history in existing more than 60 year of the theoretical investigation of Graphene, but all the time, people generally believe that the two dimensional crystal structure of this strictness is owing to thermodynamic phase is difficult to independent stable existence.Up to 2004, the study group of Univ Manchester UK utilized the method for the high oriented graphite of tape stripping to obtain self-existent two-dimentional Graphene crystal, for the experimental study of two-dimensional system provides wide space.
At present preparation method of graphene has mechanically peel method, chemical Vapor deposition process (CVD), epitaxial growth method, electrochemical process, graphite oxide reduction method etc., and wherein the graphene film amount that obtains of mechanically peel method is few, and randomness is big; CVD method and epitaxial growth method mostly with SiC as substrate, cost height, poor controllability; The Graphene amount that electrochemical method obtains is less, wayward.The graphite oxide reduction method is by introducing oxygen-containing functional group at graphite surface, increase interlamellar spacing, thereby reduces the Van der Waals force between the layer, changes its hybridization state by method such as ultrasonic then, obtains Graphene by reduction again.The graphite oxide reduction method with its cheaply advantage become one of present most popular method, at present the preparation method of graphene oxide mainly is Hummers method (Hummers, W.S.﹠amp; Offeman, R.E.Preparation of graphitic oxide.J.Am.Chem.Soc.80,1339 (1958)).This method is in the system of opening wide, need in the process of preparation graphene oxide, adopt cooling earlier, the three-step approach that heats up in two steps again, and utility appliance such as condensing reflux, need accurately to control temperature of reaction and temperature in the process up to 98 ℃, the graphene oxide for preparing also needs ultrasonic for a long time, complex steps, the concentration of product is lower, is not suitable for mass production.Chinese patent CN102225754A discloses a kind of method that adopts seal pot to prepare graphene oxide, has adopted nitrate in the raw material, and temperature of reaction is 80-130 ℃, can produce NO and NO in the reaction process
2Deng toxic gas, reduced the security of reaction process, be not suitable for industrial production.
The present invention adopts solvent-thermal method to prepare graphene oxide at low temperatures, and sample can be used for the absorption of organic dye, also can directly reduce, and obtains Graphene.Sample contains abundant oxygen-containing functional group, and output is bigger.
Summary of the invention
The purpose of this invention is to provide a kind of method that adopts solvent-thermal method to prepare graphene oxide, this method temperature is lower, easy and simple to handle, save energy, and the graphene oxide of preparation has the characteristics of equal solvent soluble in water, and output is bigger.Mild condition of the present invention, synthesis device is simple, favorable reproducibility, for the mass production of graphene oxide provides may.
For achieving the above object, it is raw material that the present invention adopts Graphite Powder 99, and the mixing acid of the vitriol oil or the vitriol oil and strong phosphoric acid is intercalator, and potassium permanganate is oxygenant.Experimental technique obtains the graphene oxide material of different degree of oxidations by changing ratio and the reaction times of oxygenant and Graphite Powder 99.
Technical scheme of the present invention is:
A kind of method for preparing graphene oxide may further comprise the steps:
A) dense mineral acid is added in the sealed reactor, under agitation, add Graphite Powder 99, be cooled to 0~4 ℃ then, add potassium permanganate again, reaction 0.5~2h;
Wherein, material proportion is the dense mineral acid of 23ml/1g Graphite Powder 99, and quality is than Graphite Powder 99: potassium permanganate=1: 4~6;
B) reaction system that will obtain above is heated to 60~70 ℃, and 12~24h is placed in sealing;
C) by volume in the distilled water: the ratio of hydrogen peroxide=10: 1 adds hydrogen peroxide in distilled water, freeze to the ice cube shape, graphite oxide is transferred in the distilled water that contains hydrogen peroxide, the distilled water of the corresponding 100ml of 1g graphite dissolves fully to ice cube, and the back suction filtration stirs, use 5% HCl, distilled water, washing with alcohol graphene oxide to sulfate radical-free respectively, and be neutral, with product dry 6h under 50 ℃, obtain graphene oxide at last.
Described dense mineral acid is one or both in the vitriol oil and the strong phosphoric acid.
Described hydrogen peroxide is the hydrogen peroxide of mass percent 30%.
Advantage of the present invention:
1, adopting Graphite Powder 99, the vitriol oil and potassium permanganate is raw material, and raw materials cost is cheap to be easy to get.
2, adopt seal pot to prepare at present adopting nitrate in the method for graphene oxide is oxygenant, does not adopt nitrate in the raw material of the present invention, has prevented NO, NO
2Generation Deng toxic gas.
3, prepare graphene oxide in seal pot, the preparation method is simple, and is easy to operate, can be by the ratio of regulating oxygenant and the degree of oxidation that oxidization time is regulated graphene oxide.With the increase of oxidant ratio, the growth of oxidization time, the interlamellar spacing maximum of graphene oxide can be extremely
4, temperature of reaction is lower, just can obtain interlamellar spacing under 60~70 ℃ the condition to be
Graphene oxide, be far smaller than 80-130 ℃ that present patent adopts, save energy, the graphene oxide that obtains contains abundant oxygen-containing functional group, and is fit to the preparation of a large amount of graphene oxides.
5, Zhi Bei graphene oxide has good dye adsorption ability, and the maximal absorptive capacity to the 20mg/l methylene blue solution can reach 199.2mg/g at normal temperatures, has industrial application value.
Description of drawings
Fig. 1 is the XRD figure of the graphene oxide of embodiment 1,2,3,4,5 preparations
Fig. 2 (a) is the microphotograph of the not dry graphene oxide solid of embodiment 1; (b) be the photo of the colloidal solution of the water-soluble formation of embodiment 1 undried graphene oxide;
Fig. 3 is the SEM figure of embodiment 1 dry rear oxidation Graphene.
Embodiment
Embodiment 1: measure the 23ml vitriol oil (massfraction is 98%), join in the polytetrafluoroethyllining lining of stainless steel cauldron of 50ml, after mixing under the magneton stirring condition, add the 1g Graphite Powder 99, under the condition of ice-water bath, be cooled to 0~4 ℃, add 6g potassium permanganate, the time is controlled at 1h, and sample is stirred.After the still sealing, put into 70 ℃ of thermostat containers, place 24h, finish graphite oxidation, sample is lavender.
Press the hydrogen peroxide that adds 10ml mass percent 30% in the 100ml distilled water, cooling is frozen to the ice cube shape.Graphite oxide is transferred in the distilled water mixture that contains hydrogen peroxide that is frozen into ice cube, treated that it dissolves back (sample is glassy yellow) fully, back sand core funnel suction filtration stirs.HCl with 5%, distilled water, ethanol wash graphite oxide successively and extremely detect sulfate radical-free with barium chloride solution, and are neutral.Sample is put into 50 ℃ of dry 6h of air dry oven.Obtain the 1.2g graphene oxide.(Fig. 1 curve a) is respectively 2 θ=26.55 ° (002) and 2 θ=54.70 ° (004) to the X ray characteristic diffraction peak of Graphite Powder 99 (Graphite), and the interlamellar spacing that represents Graphite Powder 99 is

Effect along with oxygenant, the characteristic diffraction peak of Graphite Powder 99 is more and more not obvious, and the characteristic diffraction peak of graphene oxide is more and more obvious, and diffraction angle is more and more littler, in the X ray diffracting spectrum of Fig. 1 sample, curve b represents the spectrogram of embodiment 1 sample, and the characteristic peak of graphite disappears as seen from the figure, and the crystalline structure of this explanation Graphite Powder 99 is destroyed.The diffraction peak grow of graphene oxide illustrates that body shape graphite has become less, the thinner carbon-coating (Nano grade) of size, and degree of crystallinity reduces.At this moment the interlamellar spacing of graphene oxide is
Graphite oxide than the preparation of Hummers method
(Daniela C.Marcano et.al.Improved synthesis of graphene oxide ACS Nano.20104 (8): 4806-14) its interlamellar spacing also has obvious increase, illustrates that the degree of oxidation of the graphene oxide that seal pot prepares is higher.Be the microphotograph of undried graphene oxide as Fig. 2 a, show that the graphene oxide that obtains is the glassy yellow solid, with T Chen, Baoqing Zeng etc. are to description unanimity (the Journal of physics of graphene oxide; 2009,188:012051).Photo when the colloidal solution of the water-soluble formation of undried graphene oxide that Fig. 2 b obtains for embodiment 1 is diluted to concentration and is 0.05mg/l.Be the SEM figure of dried graphene oxide as Fig. 3, as can be seen, graphene oxide becomes laminated structure, and is looser, in its edge section obvious fold arranged from the figure.
This sample is 199.2mg/g to the maximal absorptive capacity of the methylene blue solution of 20mg/l.
Embodiment 2: other experimental procedures are with embodiment 1, only change the amount of potassium permanganate, the quality that adds potassium permanganate is 5g, the mass ratio of Graphite Powder 99 and potassium permanganate is 1: 5, curve c is the X ray diffracting spectrum of this sample among Fig. 1, the characteristic diffraction peak of Graphite Powder 99 is not obvious as seen from the figure, and the interlamellar spacing of calculating the gained sample is
Show that the oxygenant consumption reduces, its reactive force in graphite layers reduces.
Embodiment 3: other experimental procedures are with embodiment 1, only by changing the amount of putting into of potassium permanganate, the quality that adds potassium permanganate is 4g, the mass ratio of Graphite Powder 99 and potassium permanganate is 1: 4, curve d is the X ray diffracting spectrum of this sample among Fig. 1, the characteristic diffraction peak of Graphite Powder 99 begins not obvious, and the interlamellar spacing of calculating the gained sample is
Show that the oxygenant consumption further reduces, its reactive force in graphite layers also reduces.
Embodiment 4: other experimental procedures are with embodiment 1, and only by changing the reaction times, the reaction times is 12h, and curve e is the X ray diffracting spectrum of this sample among Fig. 1, and the characteristic diffraction peak of Graphite Powder 99 is not obvious, and the interlamellar spacing of calculating the gained sample is
Show the reaction times minimizing, its reactive force in graphite layers reduces.This may be because in time minimizing, and the liquid evaporation amount in the seal pot reduces, and the pressure that seal pot is produced also reduces, the layer of graphite oxide with layer the variation of arrangement become not obvious.
Embodiment 5: other experimental procedures are with embodiment 3, only by changing the composition of concentrated acid, the concentrated acid that adds is the mixture of the vitriol oil (massfraction is 98%) and strong phosphoric acid (massfraction is 85%), volume ratio is 9: 1, curve f is the X ray diffracting spectrum of this sample among Fig. 1, the characteristic diffraction peak of Graphite Powder 99 is not obvious, and the characteristic diffraction peak of graphene oxide is that the interlamellar spacing that 2 θ=11.20 ° calculate sample is
Interlamellar spacing is similar to the sample of embodiment 3, but the characteristic diffraction peak of graphene oxide is more obvious.This may be because the strong phosphoric acid that adds and the functional group on graphene oxide surface interact, and makes the molecule that inserts graphite layers more, and interlamellar spacing is more stable.
From top embodiment as can be seen, by changing add-on and the oxidization time of oxygenant, can change the degree of oxidation of graphene oxide, when quality than Graphite Powder 99: during potassium permanganate=1: 6, under 70 ℃, oxidization time is that the degree of oxidation of the graphene oxide that obtains of 24h is the highest.