Summary of the invention
Technical problem to be solved by this invention is to propose a kind of TiO to above-mentioned prior art
2The hydrothermal preparing process of-rGO composite photo-catalyst, it need not under the situation of any additive as reducing agent, is solvent one step preparation high activity TiO with the pure water
2-rGO composite photo-catalyst, the composite photo-catalyst of gained shows than pure TiO
2Higher photocatalysis performance.
The present invention solves the problems of the technologies described above the technical scheme that is adopted: TiO
2The hydrothermal preparing process of-rGO composite photo-catalyst is characterized in that including the next coming in order step:
1) with the commercial P25 TiO of 0.5 g
2In 200-800 ℃, carry out preliminary treatment 0.5-5 h;
2) ultrasonic being scattered in of graphene oxide formed uniform graphene oxide (GO) solution in the deionized water, wherein the concentration of graphene oxide is 0.0025-0.5 wt %;
3) with the pretreated TiO of step 1)
2Being distributed to 10 ml steps 2) in the graphene oxide solution of preparation, stirring forms stable TiO
2-GO suspension;
4) with the TiO of step 3) gained
2-GO suspension is hydrothermal treatment consists 0.5-10 h under 100-200 ℃ of condition, and products therefrom washing 3 times after vacuum drying, promptly obtains TiO
2-rGO composite photo-catalyst.
Press such scheme, TiO in the step 1)
2Pretreatment temperature be preferably 350-600 ℃, pretreatment time is preferably 1-3h.
Press such scheme, step 2) in the concentration of graphene oxide be preferably 0.05-0.25 wt %.
Press such scheme, the hydrothermal treatment consists temperature of suspension is preferably 120-170 ℃ in the step 3), and the hydrothermal treatment consists time is preferably 2-5 h.
Press such scheme, the described vacuum drying temperature of step 4) is 30-100 ℃, and be 3-12 h drying time.
Press such scheme, the described vacuum drying temperature of step 4) is preferably 40-80 ℃, is preferably 6-8 h drying time.
The present invention proposes need not under the situation of any additive as reducing agent through hydrothermal method, is solvent one step preparation high activity TiO with the pure water
2-rGO composite photo-catalyst, its synthetic basic principle is: because the TiO after graphene oxide and the heat treatment
2All have fabulous hydrophily, make TiO
2Nano particle is easy to be distributed to the graphene oxide surface and forms uniform suspension; In the hydrothermal treatment consists process, TiO
2Deoxygenation directly takes place and forms the reduction Graphene in the graphene oxide of nanoparticle surface, causes TiO
2One step of-rGO composite photo-catalyst is synthetic.
TiO
2The photocatalytic activity of-rGO composite photo-catalyst characterizes through photocatalytic degradation phenol solution under the ultraviolet light.Experimentation is following: with 0.05 g TiO
2-rGO composite photo-catalyst is dispersed in 10 mL phenol solution (10 mgL is housed
-1) culture dish in (diameter is 5 cm), culture dish is positioned over dark place 2 h to reach adsorption equilibrium.At ambient temperature, with the ultra violet lamp of 15 W, whenever measure the phenol concentration in the solution at a distance from 15 min.(UVmini 1240, Japan) measure by the ultraviolet-visible absorption spectroscopy appearance for the concentration of phenol in the degradation solution.
TiO
2The micro-structural characterizing method of-rGO composite photo-catalyst: observe pattern and granular size with field emission scanning electron microscope (FESEM); With X-ray diffraction (XRD) spectrum analysis crystallization situation, with the reduction situation of infrared spectrum (FTIR) and Raman spectrum analysis graphene oxide.Mg target K α be the photoelectron spectrograph (KRATOA XSAM800 XPS) of X-ray source obtain x-ray photoelectron can spectrogram, confirm component and valence state.
Beneficial effect of the present invention is: of the present invention is the method for solvent with the pure water, simple to operate, need not to add reducing agents such as various organic surface active agents, additive, is a kind of graphene oxide method of reducing of environmental protection.The high electron mobility of reduction Graphene can improve the effective separative efficiency in light induced electron-hole, thereby improves TiO
2Photocatalysis performance.As commercialization P25 TiO
2When containing the 1-5% Graphene in the Graphene composite photo-catalyst, Pyrogentisinic Acid's photocatalytic degradation performance is than pure commercialization P25 TiO under ultraviolet light
2Improve 20%-30%.The present invention has that operation is very simple, equipment requirements is low, need not expensive various reaction units, be easy to advantage such as synthetic in enormous quantities.
The specific embodiment
Below in conjunction with embodiment the present invention is done further detailed explanation, but this explanation can not be construed as limiting the invention.
Embodiment 1:
TiO
2The preparation process of-rGO composite photo-catalyst is following: (1) is with the commercial P25 TiO of 0.5 g
2Through 550 ℃ of preliminary treatment 2 h; (2) graphene oxide is dissolved in deionized water for ultrasonic and handles back formation uniform graphene oxide (GO) solution, wherein the concentration of graphene oxide is 0.05 wt %; (3) the pretreated TiO of 0.5 g
2Be distributed in the 10 ml graphene oxide solution, stir 2 h, form stable TiO
2-GO suspension; (4) with the TiO of above-mentioned preparation
2-GO suspension places hydrothermal treatment consists 5 h under 150 ℃ of conditions; After the products therefrom washing 3 times,, promptly obtain TiO at 60 ℃ of vacuum drying 6 h
2-rGO composite photo-catalyst.
Fig. 1 is TiO
2The synthetic sketch map of-rGO composite.As everyone knows, because graphene oxide contains a lot of oxygen-containing functional groups, like-OH, C=O, C-O-C and-COOH are so it can be scattered in the even and stable solution of formation in the water well.Fig. 1 a is the graphene oxide structural representation, can find out that from its optics picture graphene oxide is pale brown look; Fig. 1 b is TiO
2With the mixture of graphene oxide, can find out TiO
2Be dispersed in well in the graphene oxide solution, because the TiO that adds
2Be white powder, so that mixed solution is is light yellow; Fig. 1 c is TiO after the hydrothermal treatment consists
2With graphene composite material.Can find out that Graphene becomes black by pale brown look before and after hydro-thermal, explain that graphene oxide is reduced.Through to TiO
2With the simple hydrothermal treatment consists of graphene oxide, obtained a series of TiO
2With the redox graphene composite.Explanation is easy to graphene oxide is reduced to the reduction Graphene under certain hydrothermal condition, simultaneously, and TiO
2Particle be dispersed on the Graphene surface.
Fig. 2 is the TiO of preparation
2The XRD figure spectrum of-rGO composite.Clearly, hydrothermal treatment consists rear oxidation Graphene (Fig. 2 a) 2
θ=11.0 characteristic peaks disappear, and in reduction Graphene (Fig. 2 b), occur 2
θThe characteristic peak of=24.1 (002) crystal faces explains that graphene oxide successfully is reduced.And it should be noted that TiO
2-rGO composite (Fig. 2 d) has and TiO
2The XRD figure spectrum that (Fig. 2 c) characteristic diffraction peak is similar.At TiO
2With the diffraction maximum that does not have to find to belong to separately the Graphene characteristic in the composite of Graphene, reason possibly be that Graphene content in compound is limited.
Fig. 3 is graphene oxide, TiO
2And TiO
2The FESEM figure of-rGO composite.Fig. 3 a is the SEM figure of graphene oxide, can find out that from figure graphene oxide is a structure thin and that curl.Can see the TiO that particle diameter is little and be evenly distributed from Fig. 3 b
2Particle.And can find out that from Fig. 3 c after hydro-thermal Graphene is also keeping curl pattern and at a lot of TiO of its surface distributed of thin stratiform
2Particle, size is about 30 nm.Show TiO
2And the success between the Graphene formed strong chemical bond, might improve the photocatalytic activity of composite.
Fig. 4 is graphene oxide, reduction Graphene, TiO
2And TiO
2The infrared spectrum of-rGO composite.(Fig. 4 a) demonstrates very strong absworption peak owing to having many oxygen-containing functional groups to graphene oxide, like stretching vibration peak (3410 cm of hydroxyl-OH waterborne
-1The place), carbonyl C=O stretching vibration peak (1734 cm
-1The place), water-flexural vibrations peak and C=C stretching vibration peak (1629 cm of OH
-1The place), C-OH flexural vibrations peak (1420 cm
-1The place), epoxy stretching vibration peak C-O-C and C-O (1227 cm
-1The place) and carboxylic acid on C-O stretching vibration peak (1055 cm
-1The place).Compare with graphene oxide, in the redox graphene (Fig. 4 b) water-OH vibration peak, 1734 cm
-1C=O peak, 1055 cm at place
1The C-O peak and the 800-1500 cm at place
-1The intensity in peak district all obviously descends, and the successful deoxidation of graphene oxide be described and is reduced to the reduction Graphene.TiO
2In the infrared spectrogram of (Fig. 4 c) in showing water-the flexible and flexural vibrations of OH, (400-900 cm also in the lower wave number district
-1) TiO arranged
2The Ti-O-Ti key.TiO
2The situation of oxygen-containing functional group and rGO's is similar in-the rGO composite (Fig. 4 d), be illustrated in after the hydrothermal treatment consists graphene oxide in the composite successful transformation for reducing Graphene.The 400-900 cm in the lower wave number district in addition
-1, TiO
2-rGO composite shows the absorption of broad, mainly is because TiO
2Ti-O-Ti key and the new Ti-O-C key acting in conjunction that forms cause.Therefore, above-mentioned result of study has confirmed the successful reduction and the TiO of graphene oxide
2The success of-rGO composite is synthetic.
The TiO that the Raman spectrum of Fig. 5 can provide
2Structural information with Graphene.TiO
2(Fig. 5 a) in the structure Raman peaks at 144 cm
-1(E
g), 395 cm
-1(B
1g), 516 cm
-1(A
1g) and 639 cm
-1(E
g) demonstrate very strong characteristic peak.And work as TiO
2With the compound back of Graphene (Fig. 5 d), these characteristic peaks significantly weaken, and possibly be because Graphene is coated on TiO
2The surface, part has been covered TiO
2Raman information.This has shown and has formed very strong chemical action between the composite.Raman spectrum also is carbon atom sp in the strong and widely used sign Graphene
2And sp
3The hybrid structure defective.The illustration of Fig. 5 shows, at 1347 cm
-1With 1590 cm
-1The place finds the D peak and the G peak of Graphene and composite thereof.The D peak is by sp
3The carbon of hydridization type causes, in Graphene, show as structural defective and unordered degree, and the G peak is by sp
2The carbon of hydridization type causes, in Graphene, shows as the integrated degree on the graphene-structured.And the strength ratio at D peak and G peak has reflected the defective and the unordered degree of Graphene usually.By Fig. 5 result, calculate the I of graphene oxide
D/ I
GBe 0.807, and the I of reduction Graphene
D/ I
GBeing higher than graphene oxide is 0.925, is illustrated in that graphene oxide has been reduced to the reduction Graphene in the composite.On the other hand, can find out TiO
210 cm have an appointment at the G peak of-rGO composite
-1Variation.Therefore, be all tangible proof to be provided for the reduction of graphene oxide and graphene composite material successfully synthesize at the variation of raman spectrum strength and G peak blue shift.
Fig. 6 is graphene oxide, reduction Graphene and TiO
2The C 1s spectrogram of the x-ray photoelectron power spectrum (XPS) of-rGO composite.In the C of XPS 1s spectrogram, show there is four types carbon bond, that is: C – C, C=C, C-H (284.9 eV), C-O-C, C-OH (286.6 eV), C=O (287.6 eV) and O=C-OH (288.3 eV).(Fig. 6 C-C a), C=C and c h bond and oxygen containing carbon bond C-O (286.6 eV) and C=O (288.3 eV) intensity are all very high for graphene oxide.Oxygen containing carbon bond intensity obviously descends in reduction Graphene (Fig. 6 b), simultaneously, can find out with graphene oxide from table 1 and to compare that the shared ratio of peak area of the CC key of reduction Graphene is increased to 0.62 from 0.42.Yet C-O-C and O=C-OH proportion drop to 0.14 and 0.19 from 0.32 respectively and drop to 0.03.This shows that water-heat process has reduced the content of C-O key, thereby makes graphene oxide change the reduction Graphene into.From TiO
2Can find out similarly with the reduction Graphene in the C1s spectrogram of the XPS of-rGO composite (Fig. 6 c), it contains oxygen carbon bond ratio and also correspondingly reduces.Above result shows that hydro-thermal is synthetic and can significantly reduce carbon-oxygen bond content, thereby makes graphene oxide convert the reduction Graphene into and be TiO
2The reduction of GO further provides strong evidence in the-rGO composite.
Fig. 7 is TiO
2And TiO
2Under ultraviolet light, the degrade degradation rate constant column diagram of phenol solution of-rGO composite.As can be seen from the figure, the content of Graphene is to TiO
2Photocatalysis performance remarkable influence is arranged.After introducing a spot of Graphene, sample TiO
2The photocatalysis performance of-rGO (1 wt %) (Fig. 7 b) is than pure TiO
2(Fig. 7 a) obviously strengthens, and reaction rate constant is 4.7 * 10
-3Min
-1TiO
2The principle that-rGO composite photocatalyst performance strengthens is: at first, Graphene is owing to have the absorption property that big specific area has excellence, thereby increased near the organic concentration catalyst surface.The phenol molecule is transferred to catalyst surface and can be connected with the Graphene conjugation from solution.Therefore with pure TiO
2Compare TiO
2-rGO composite Pyrogentisinic Acid has higher adsorption rate.Secondly, titanium dioxide produces electron-hole pair behind ultraviolet excitation.With Graphene compound after, the electronics on the titanium dioxide conduction band can be transferred on the Graphene fast, has reduced the compound of electronics and hole effectively.Therefore, the quick transmission of the strong adsorption capacity of Graphene and charge carrier has promoted the degraded of photochemical catalyst to dyestuff.
Embodiment 2:
In order to check TiO
2The powder pre-treating temperature is to TiO
2The influence of-rGO nano composite material, except that the pretreatment temperature difference, other reaction conditions are following: TiO
2Powder pre-treating time (2 h), TiO
2Powder quality (0.5 g), graphene oxide concentration (0.05 %) and volume (10 milliliters), mixing time (2 h), hydrothermal temperature (150 ℃), hydro-thermal time (5 h), baking temperature (60 ℃), drying time (6 h) etc. are all identical with embodiment 1.The result shows, pretreatment temperature in the time of 200 ℃, TiO
2The adsorbed impurity of powder surface fails effectively to remove, and mix back uniformity and suspendability with Graphene solution not so good, influenced TiO
2Combination with Graphene; Pretreatment temperature in the time of 350-600 ℃, TiO
2Powder mixes with Graphene solution, and it is all fine to obtain solution uniformity and suspendability; When pretreatment temperature reaches 800 ℃, TiO
2Powder particle is excessive, is unfavorable for being dispersed in the solution of graphene oxide, and coagulation takes place easily.Therefore, TiO
2In the building-up process of-rGO nano composite photo-catalyst, TiO
2The powder pre-treating optimum temperature is 350-600 ℃.
Embodiment 3:
In order to check TiO
2The powder pre-treating time is to TiO
2The influence of-rGO nano composite material, except that the pretreatment time difference, other reaction conditions are following: TiO
2Powder pre-treating temperature (550 ℃), TiO
2Powder quality (0.5 g), graphene oxide concentration (0.05 %) and volume (10 milliliters), mixing time (2 h), hydrothermal temperature (150 ℃), hydro-thermal time (5 h), baking temperature (60 ℃), drying time (6 h) etc. are all identical with embodiment 1.The result shows, when pretreatment time is 0.5 h, and TiO
2The adsorbed impurity of powder surface fails effectively to remove, and has influenced the formation and the TiO of composite
2Combination with Graphene; When pretreatment time is 1-3 h, TiO
2The adsorbed impurity of powder surface is effectively removed, and has formed fresh interface, makes TiO
2Combine to be easy to carry out with the Graphene surface; When pretreatment time reaches 5 h, TiO
2Powder particle is excessive, is unfavorable for being dispersed in the graphene oxide solution forming suspension, and coagulation takes place easily.Therefore, TiO
2In the building-up process of-rGO nano composite photo-catalyst, TiO
2The powder pre-treating Best Times is 1-3 h.
Embodiment 4:
In order to check Graphene concentration to TiO
2The influence of-rGO nano composite material photocatalysis performance, except that Graphene concentration difference, other reaction conditions are following: TiO
2Powder pre-treating temperature (550 ℃), TiO
2Powder pre-treating time (2 h), TiO
2Powder quality (0.5 g), graphene oxide volume (10 milliliters), mixing time (2 h), hydrothermal temperature (150 ℃), hydro-thermal time (5 h), baking temperature (60 ℃), drying time (6 h) etc. are all identical with embodiment 1.The result shows that Graphene concentration is at 0.0025% o'clock, and Graphene content is very few to TiO
2Photocatalysis performance is obviously influence not; When Graphene concentration is 0.05%-0.25 %, the TiO of gained
2The performance of-rGO composite photo-catalyst has obvious humidification, and Pyrogentisinic Acid's photocatalytic degradation performance is than pure commercialization P25 TiO under ultraviolet light
2Improve 20%-30%; When Graphene concentration was 0.5%, too much the photocatalytic activity of Graphene sample was than pure TiO
2Low.This possibly be because TiO
2-rGO composite is to the increase of scattering of light, and the Graphene of high-load covered the absorption to ultraviolet light of the titanium dioxide that coats, causes the rapid minimizing through the reactant liquor exciting light.Therefore, TiO
2In the building-up process of-rGO nano composite photo-catalyst, the graphene oxide optimum concentration range is 0.05%-0.25 %.
Embodiment 5:
In order to check hydrothermal temperature to TiO
2The influence of-rGO nano composite material photocatalysis performance, except that hydro-thermal temperature difference, other reaction conditions are following: TiO
2Powder pre-treating temperature (550 ℃), TiO
2Powder pre-treating time (2 h), TiO
2Powder quality (0.5 g), graphene oxide concentration (0.05%) and volume (10 milliliters), mixing time (2 h), hydrothermal temperature (150 ℃), hydro-thermal time (5 h), baking temperature (60 ℃), drying time (6 h) etc. are all identical with embodiment 1.The result shows that when hydrothermal temperature was 100 ℃, graphene oxide is reduced degree to be reduced greatly; When hydrothermal temperature was respectively 120 ℃, 150 ℃, 170 ℃, graphene oxide can be reduced; When hydrothermal temperature is higher than 180 ℃, when reaching 200 ℃, Graphene and compound generation carbonization thereof.Therefore, TiO
2In the building-up process of-rGO nano composite photo-catalyst, the optimum temperature of hydro-thermal is 120-170 ℃.
Embodiment 6:
In order to check the hydro-thermal time to TiO
2The influence of-rGO nano composite material, except that the hydro-thermal asynchronism(-nization), other reaction conditions are following: TiO
2Powder pre-treating temperature (550 ℃), TiO
2Powder pre-treating time (2 h), TiO
2Powder quality (0.5 g), graphene oxide concentration (0.05%) and volume (10 milliliters), mixing time (2 h), hydrothermal temperature (150 ℃), baking temperature (60 ℃), drying time (6 h) etc. are all identical with embodiment 1.The result shows that the hydro-thermal time is relevant with hydrothermal temperature.Hydrothermal temperature is 150 ℃, and when the hydro-thermal time was 0.5 h, the degree that graphene oxide is reduced reduced greatly; When the hydro-thermal time was 2-5 h, graphene oxide can be reduced relatively fully; When the hydro-thermal time reached 10 h, Graphene and compound pattern thereof and photocatalysis performance did not all have obvious variation.Therefore, TiO
2In the building-up process of-rGO nano composite photo-catalyst, collateral security Graphene reducing degree considers with the angle that saves time, and hydro-thermal reaction time optimal is 2-5 h.
Embodiment 7:
In order to check baking temperature to TiO
2The influence of-rGO nano composite material, except that the baking temperature difference, other reaction conditions are following: TiO
2Powder pre-treating temperature (550 ℃), TiO
2Powder pre-treating time (2 h), TiO
2Powder quality (0.5 g), graphene oxide concentration (0.05%) and volume (10 milliliters), mixing time (2 h), hydrothermal temperature (150 ℃), hydro-thermal time (5 h), drying time (6 h) etc. are all identical with embodiment 1.The result shows, when baking temperature is 30 ℃, and TiO
2The complete baking needed of-rGO composite material granular chronic; When baking temperature is 40-80 ℃, TiO
2The time of the complete baking needed of-rGO composite material granular is appropriate; When baking temperature reaches 100 ℃, TiO
2-rGO composite material granular hardens easily and becomes big block.Therefore, TiO
2In the building-up process of-rGO nano composite photo-catalyst, dry optimum temperature is 40-80 ℃.
Embodiment 8:
In order to check drying time to TiO
2The influence of-rGO nano composite material, except that the drying time difference, other reaction conditions are following: TiO
2Powder pre-treating temperature (550 ℃), TiO
2Powder pre-treating time (2 h), TiO
2Powder quality (0.5 g), graphene oxide concentration (0.05%) and volume (10 milliliters), mixing time (2 h), hydrothermal temperature (150 ℃), hydro-thermal time (5 h), baking temperature (60 ℃) etc. are all identical with embodiment 1.The result shows, TiO
2The drying time of-rGO nano composite material particle is relevant with baking temperature.When baking temperature is 60 ℃, be 3 h when drying time, sample does not parch, and also contains than juicy; When drying time is 6-8 h, and sample parches; After being 12 h drying time, the quality and the character of Graphene and compound thereof do not have obvious variation.Therefore, TiO
2In the building-up process of-rGO nano composite photo-catalyst, collateral security sample bone dry considers that with the angle that saves time when baking temperature was 60 ℃, be 6-8 h best drying time.
Contain the peak area of oxygen carbon bond and the ratio of the gross area among table 1 XPS
Sample |
A
C-C/A
|
A
C-O/A
|
A
C=O/A
|
A
COOH/A
|
GO |
0.42 |
0.32 |
0.07 |
0.19 |
rGO |
0.62 |
0.14 |
0.21 |
0.03 |
TiO
2-rGO (1 wt %)
|
0.86 |
0.10 |
0.04 |
0 |