CN108940268B - graphene/Pt nano composite aerogel material and preparation method thereof - Google Patents

graphene/Pt nano composite aerogel material and preparation method thereof Download PDF

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CN108940268B
CN108940268B CN201810841248.9A CN201810841248A CN108940268B CN 108940268 B CN108940268 B CN 108940268B CN 201810841248 A CN201810841248 A CN 201810841248A CN 108940268 B CN108940268 B CN 108940268B
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graphene
aerogel material
nitrophenol
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CN108940268A (en
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杨性坤
刘先福
张钰
杨鑫
罗扣
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Xinyang Normal University
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Abstract

The invention relates to a graphene/Pt nano composite aerogel material and a preparation method thereof. The preparation method of the graphene/Pt nano composite aerogel material comprises the following steps: h is to be2PtCl6·6H2Mixing an isopropanol solution of O and a graphene oxide solution to obtain a mixed solution, introducing nitrogen into the mixed solution for 10-20 min, and then carrying out the mixed solution at room temperature60Co irradiation, washing and freeze drying. According to the preparation method disclosed by the invention, any surfactant is not required to be additionally added in the whole process, the dispersity of Pt nanoparticles in the prepared graphene/Pt (GA/Pt) nano composite aerogel material is very good, and the material has the advantages of light weight and high porosity of the graphene aerogel.

Description

graphene/Pt nano composite aerogel material and preparation method thereof
Technical Field
The invention relates to a graphene/Pt nano composite aerogel material and a preparation method thereof.
Background
P-nitrophenol (4-NP) is a common organic contaminant in water. The removal of p-nitrophenol has been a very important problem. A number of methods have been developed including: adsorption, microbial degradation, photocatalytic degradation, an electro-Fenton method, an electrocoagulation method, an electrochemical treatment method and the like. On the other hand, the common precursor of p-nitrophenol is p-aminophenol (4-AP), and p-nitrophenol is an important intermediate product for preparing analgesic/antipyretic medicaments, and can also be used as a developer, a preservative, an antiseptic lubricant and a hair dye. Catalytic hydrogenation of 4-NP has been achieved with metal catalysts placed in ethanol solution at high temperature and high hydrogen pressure. However, in order to save energy, operate safely and avoid the use of organic solvents, it remains necessary to explore the possibility of achieving conversion of 4-NP and 4-AP in a suitably mild aqueous environment.
The metal nano particles have higher Fermi potential, can effectively reduce reduction potential and can effectively catalyze the electron transfer reaction. With the rapid and vigorous development of nanotechnology over the last two decades, metal nanoparticles were incorporated in sodium borohydride (NaBH)4) There is increasing interest in achieving mild reduction of 4-NP to 4-AP in solution. In addition, because magnetic nanoparticles have high specific surface area and heterogeneous support of magnetic recoverability, so that the magnetic nanoparticles have high catalytic activity in catalytic reaction, some researchers have made some efforts on iron oxide, and the nanoparticles are taken as supports to develop nano-catalysts capable of controlling magnetic recoverability for catalytic reduction of 4-NP, such as Au-Fe3O4And Ag @ Pd-Fe3O4A composite nanomaterial. However, most of the synthetic preparation of the above metal nanoparticles and magnetic composite nanoparticles involves the use of surfactants, reducing agents, or toxic and harmful organic solvents. In order to reduce or eliminate the harm to human health and environment, the preparation method for developing the green and environment-friendly catalyst for catalytic reduction of 4-NP has good application prospect.
Disclosure of Invention
The invention aims to provide a preparation method of a graphene/Pt nano composite aerogel material, which is implemented60The Co is irradiated, so that the environment is protected.
The second purpose of the invention is to provide a graphene/Pt nano composite aerogel material.
In order to achieve the purpose, the technical scheme of the invention is as follows:
a preparation method of a graphene/Pt nano composite aerogel material comprises the following steps:
h is to be2PtCl6·6H2Mixing the isopropanol solution of O and the graphene oxide solution to obtain a mixtureMixing the solution, introducing nitrogen into the mixed solution for 10-20 min, and then carrying out the mixed solution at room temperature60Co irradiation, washing and freeze drying.
The concentration of the graphene oxide in the mixed solution is 1-6 mg/mL.
Graphene oxide and H in the mixed solution2PtCl6·6H2The mass ratio of O is 1-8: 1.
the above-mentioned60The total dose of Co irradiation is 100-300 kGy.
The above-mentioned60The dosage rate of Co irradiation is 1.00-6.50 kGy/h, and the total irradiation time is 20-86 h.
The graphene oxide solution is prepared by a preparation method comprising the following steps: carrying out oxidation treatment on graphite by using nitric acid, potassium permanganate, potassium thiosulfate, phosphorus pentoxide and hydrogen peroxide, sequentially washing by using hydrochloric acid and a hydrogen peroxide solution, then carrying out centrifugal separation, filling the obtained solution into a dialysis bag for ion exchange dialysis, and filling the solution in the dialysis bag after dialysis to obtain a graphene oxide solution.
The mass fraction of the hydrochloric acid is 0.1-8%.
The mass fraction of the hydrogen peroxide solution is 1-60%.
The washing is carried out by adopting a mixed solution of water and ethanol, and the volume ratio of the water to the ethanol is 1: 1.
The freeze drying is carried out at the temperature of between 81 ℃ below zero and 5 ℃ below zero for 120 to 180 hours.
A graphene/Pt nano composite aerogel material is prepared by adopting the preparation method. The graphene/Pt nano composite aerogel material is prepared from graphene oxide and H2PtCl6·6H2And O is subjected to gamma ray irradiation in an isopropanol system to induce synchronous irradiation reduction self-assembly.
The graphene/Pt nano composite aerogel material has a three-dimensional communicated honeycomb structure.
The preparation method of the invention has the advantages that the whole reaction system is carried out in a milder water/isopropanol system and is used in a room temperature environment60Co irradiationGenerating gamma rays to induce water decomposition in the reaction system to generate hydrated electrons, hydroxyl free radicals, hydrogen free radicals and H2O2The hydrated electrons are nucleophilic particles with strong reducing capability and can rapidly generate electron capture reaction with oxygen-containing functional groups, so that the aim of reduction is fulfilled; during irradiation, hydrogen radicals and hydrated electrons act on unstable carbonyl and carboxyl between graphene oxide nanosheets to reduce the unstable carbonyl and carboxyl, so that oxygen-containing functional groups are reduced, and the interlayer spacing of the graphene oxide nanosheets is reduced. The isopropanol in the system acts as an oxygen radical scavenging agent in the reaction system60Under the irradiation of Co, the catalyst reacts with hydroxyl radicals generated by water decomposition to generate reducing substance hydrogen radicals which can further assist in reducing graphene oxide and Pt4+. No surfactant is additionally added in the whole process, the dispersity of Pt nanoparticles in the prepared GA/Pt (graphene/Pt) nano composite aerogel material is very good, and the material has the advantages of light weight and high porosity of graphene aerogel.
The graphene/Pt nano composite aerogel material has a three-dimensional communicated honeycomb structure, and the communicated honeycomb structure is formed by stacking and overlapping graphene sheets. The Pt nano particles are independently and uniformly loaded on the graphene sheet layer, the particle size range is only 2-5 nm, the Pt nano particles loaded on the graphene sheet layer can well prevent the aggregation and the overlapping of the graphene sheet layer, and the catalytic activity of the catalyst and the sensitivity of the sensor are effectively improved.
Drawings
Fig. 1 is a schematic diagram of a method of preparing a graphene/Pt nanocomposite aerogel material of example 1;
FIG. 2 is an AFM image and an SEM image of graphene/Pt nanocomposite aerogel material of graphene oxide of example 1;
in fig. 3, a is a TEM image of graphene oxide in example 1, b is a TEM image of a graphene/Pt nanocomposite aerogel material, c is an enlarged TEM image of Pt nanoparticles, and d is a selected region electron diffraction pattern of the Pt nanoparticles;
fig. 4 is an element distribution energy spectrum of the graphene/Pt nanocomposite aerogel material in example 1;
FIG. 5 is a Raman spectrum of graphene oxide and graphene/Pt nanocomposite aerogel material of example 1;
FIG. 6 is an XRD pattern of graphene/Pt nanocomposite aerogel materials of examples 1-5;
FIG. 7 is a TGA test plot of the graphene/Pt nanocomposite aerogel materials of examples 1-5;
FIG. 8 is a schematic diagram of a reduction mechanism of catalytic reduction of p-nitrophenol with a graphene/Pt nanocomposite aerogel material;
FIG. 9 is a graph of the UV absorption spectrum of the graphene/Pt nanocomposite aerogel material of example 1 after being left for different periods of time to reduce p-nitrophenol;
FIG. 10 is a schematic graph of the cyclic catalytic efficiency of GA/Pt nanocomposite aerogel material of example 1, which was cyclically catalyzed 30 times;
FIG. 11 is a graph comparing UV absorption spectra of graphene/Pt nanocomposite aerogel materials obtained in examples 1-5 by catalytic reduction;
FIG. 12 shows 4-NP and NaBH4The influence of the molar ratio of (a) to (b) on the catalytic efficiency is shown schematically;
FIG. 13 is a graph comparing the catalytic reduction efficiency of the graphene/Pt nanocomposite aerogel materials of examples 1-5 after 20 cycles of catalysis;
FIG. 14 is a graph of the UV absorption spectrum of sodium borohydride catalyzed p-nitrophenol;
fig. 15 is a graph of an ultraviolet absorption spectrum of graphene aerogel catalyzed p-nitrophenol.
Detailed Description
The graphene oxide solution used in the embodiment of the invention is prepared by a Hummers improved method, and is specifically prepared as follows:
1) firstly weighing 5g of natural crystalline flake graphite, adding the natural crystalline flake graphite into a 500mL conical flask container, then slowly adding 150mL of concentrated sulfuric acid and 50mL of concentrated nitric acid into the conical flask, placing the conical flask on a magnetic stirrer, strongly stirring for 24 hours to fully and uniformly mix the natural crystalline flake graphite, then slowly pouring the natural crystalline flake graphite into a beaker filled with 1L of ultrapure water, repeatedly washing the natural crystalline flake graphite for a plurality of times by using the ultrapure water, then carrying out suction filtration by using a Buchner funnel, and placing filter residues in a vacuum oven at 60 ℃ for drying for 24 hours, wherein the pre-oxidation process of the graphite is carried out; the natural flake graphite is purchased from Sigma-Aldrich and has an average size of 500 mu m;
2) placing the pre-oxidized graphite in a high-temperature environment of 1000 ℃ for 10s to ensure that the pre-oxidized graphite is fully expanded and stripped, and obtaining thermal expansion graphite in the process;
3) a thermally expandable graphite sample (5 g) was weighed, and 4.2g of K was added to the sample2S2O8And 6.2g of P2O5Then placing the mixed sample in a 500mL conical flask, then adding 300mL concentrated sulfuric acid, fully stirring, after the sample is uniformly mixed, placing the sample in a 80 ℃ constant-temperature water bath environment, keeping the temperature for 5 hours, then slowly pouring the mixed solution into 2L of ultrapure water, repeatedly washing, filtering and drying, wherein the sample obtained in the process can be called as deep-oxidized thermal expansion graphite;
4) 5g of the deeply oxidized thermal expansion graphite sample is placed in an environment at 0 ℃ to be mixed with 200mL of concentrated sulfuric acid, and then 15g of KMnO is slowly added into a sample bottle4After the reagents are uniformly mixed, the sample bottle is placed in a water bath environment of 35 ℃ for constant temperature reaction for 2H, the reaction solution is slowly poured into 2L of ultrapure water in a strong stirring atmosphere, and then 10mL of H is slowly added2O2(30 wt%) during which the sample solution was seen to turn into a golden yellow mixture;
5) standing for a period of time, pouring out supernatant, transferring the rest solution into dialysis bag, and dialyzing with ultrapure water and dilute hydrochloric acid solution for 7 times to remove unreacted ions;
6) and (4) filtering the dialyzed sample solution to remove precipitates, wherein the filtrate is the sample graphene oxide aqueous solution.
Example 1
The preparation method of the graphene/Pt nanocomposite aerogel material of the embodiment, as shown in fig. 1, includes the following steps:
1) preparing a graphene oxide solution by the same specific method;
2) 5mL of H2PtCl6·6H2Slowly dripping an Isopropanol (IPA) solution of O into 5mL of the graphene oxide solution obtained in the step 1) to obtain a mixed solution, and ensuring that the concentration of the graphene oxide in the mixed solution is 2 mg/mL; graphene oxide and H in the mixed solution2PtCl6·6H2The mass ratio of O is 2: 1;
3) magnetically stirring the mixture for 2h, introducing nitrogen for 10min to remove residual oxygen, and cooling at room temperature60Co irradiation, wherein the total irradiation dose is 200kGy, specifically: the irradiation dose rate is 4.55kGy/h, and the total irradiation time is 44 h; after irradiation, washing unreacted isopropanol and extra ions by using a mixed solution (volume ratio is 1:1) of water and ethanol for not less than 5 times, and freeze-drying a product at-5 ℃ for 180 hours after washing to obtain the graphene/Pt nano composite aerogel material.
The graphene/Pt nanocomposite aerogel material of the present embodiment has a three-dimensionally connected honeycomb structure.
Example 2
The present embodiment is different from embodiment 1 only in that, in step 2), graphene oxide and H are contained in the mixed solution2PtCl6·6H2The mass ratio of O is 1: 1.
Example 3
The present embodiment is different from embodiment 1 only in that, in step 2), graphene oxide and H are contained in the mixed solution2PtCl6·6H2The mass ratio of O is 4: 1.
Example 4
The present embodiment is different from embodiment 1 only in that, in step 2), graphene oxide and H are contained in the mixed solution2PtCl6·6H2The mass ratio of O is 6: 1.
Example 5
The present embodiment is different from embodiment 1 only in that, in step 2), graphene oxide and H are contained in the mixed solution2PtCl6·6H2The mass ratio of O is 8: 1.
Example 6
The difference between the embodiment and the embodiment 1 is only that the total irradiation dose in the step 3) is 300kGy, and the total irradiation time is 66 h; the temperature and time for freeze-drying was-81 deg.C for 120 h.
Example 7
The difference between the embodiment and the embodiment 1 is only that the total irradiation dose in the step 3) is 100kGy, and the total irradiation time is 22 h; the temperature and time for freeze-drying was at-70 deg.C for 140 h.
Example 8
The present example is different from example 1 only in that the concentration of graphene oxide in the mixed solution is ensured to be 1mg/mL in step 2).
Example 9
The present example is different from example 1 only in that the concentration of graphene oxide in the mixed solution is ensured to be 6mg/mL in step 2).
Experimental example 1
The graphene oxide obtained in step 1) of example 1 is subjected to an AFM (atomic force microscope) test, and the result is shown in a graph a in fig. 2, from which it can be clearly seen that the size of graphene oxide lamella is relatively uniform and flat, and the average thickness of the graphene oxide lamella is about 1 nm;
SEM tests of different magnifications are carried out on the graphene/Pt nanocomposite aerogel material obtained in example 1, and the results are shown in b-d graphs in figure 2, wherein the b-d graphs show graphene oxide and H2PtCl6·6H2And (3) performing gamma-ray irradiation induced self-assembly on the O to form the GA/Pt nano composite aerogel material, wherein the b diagram in the figure 2 shows that the surface of the GA/Pt nano composite aerogel material is relatively smooth and flat, the c-d diagrams sequentially show the longitudinal section and the transverse section of the GA/Pt nano composite aerogel material, and the GA/Pt nano composite aerogel material can be seen to have a three-dimensionally communicated honeycomb structure.
Experimental example 2
The TEM test of the graphene oxide obtained in step 1) of example 1 shows that the result is shown in a of fig. 3, and as can be seen from a of fig. 3, the graphene oxide is a transparent monolithic layer with some wrinkles on the layer, further revealing that the graphite achieves complete exfoliation of the layer after a series of chemical oxidations and some magnetic stirring.
The TEM test of the graphene/Pt nanocomposite aerogel material obtained in example 1 shows that, as shown in b of fig. 3, Pt nanoparticles are tightly adhered to the graphene sheet layer, and are uniformly dispersed in the whole area, and only at the folds of graphene, the adsorbed platinum nanoparticles are more densely observed, as can be clearly seen from b of fig. 3. This may be due to the greater degree of graphene defects at the folds, which provide more ion attachment active sites. The Pt nano particles have better dispersibility, and further illustrate that the graphene oxide and H2PtCl6·6H2O is reduced and self-assembled in an isopropanol system through gamma ray irradiation induction synchronous irradiation. The inset in the b diagram in fig. 3 shows the statistical distribution of the particle size of the randomly extracted 100 Pt nanoparticles in the whole characterization region, and it can be seen from the statistical diagram that the particle size distribution of the Pt nanoparticles is narrow, 2-5 nm. In fig. 3, c is a high resolution transmission electron microscope picture showing oriented and ordered lattice fringes of Pt nanoparticles, representing lattice spacings of 0.23nm and 0.20nm, corresponding to the (111) and (220) crystal planes of the Pt nanoparticles, respectively, which is consistent with XRD data. Fig. 3, d, is a selected area electron diffraction pattern of Pt nanoparticles in the graphene/Pt nanocomposite aerogel material of example 1, from which it can be determined that the Pt nanoparticles adhered to the graphene sheet layer belong to a single crystal.
The above Transmission Electron Microscope (TEM) image and the selected area electron diffraction pattern were obtained from FEI Tecnai G2F20S-TWIN, in which the field emission voltage was 200 kV.
Fig. 4 is an element distribution energy spectrum (EDX diagram) of the graphene/Pt nanocomposite aerogel material in example 1, from which it can be determined that the prepared composite material is pure and has only three elements of C, O and Pt (since copper is contained in the copper film used in the TEM test, the Cu peak is correspondingly present in fig. 4).
Experimental example 3
The graphene oxide obtained in step 1) of example 1 and the graphene/Pt nanocomposite aerogel material of example 1 were subjected to raman spectroscopy, and the results are shown in fig. 5Shown in the figure. It is well known that graphene oxide and reduced graphene oxide are present at 1350cm-1And 1585cm-1There are characteristic diffraction peaks, which are assigned to the D peak and the G peak. The D peak represents the degree of disorder of the edge, defect and structure of the solid carbon, and the G peak represents sp of C atom2First order scattering of the hybridized E2g mode. From fig. 5, it can be seen that the intensity ratio of the D peak and the G peak in the GA/Pt nanocomposite aerogel material is increased from 0.91 to 1.23 of the graphene oxide, which indicates that the conductive network in the reduced graphene oxide in the GA/Pt nanocomposite aerogel material is modified to some extent, and the electron transport performance of the reduced graphene oxide can be improved well. An increase in the value of ID/IG also means an increase in the degree of graphene disorder, further indicating successful loading of Pt nanoparticles.
Experimental example 4
XRD characterization was performed on the graphene/Pt nanocomposite aerogel materials of examples 1-5, and the results are shown in FIG. 6, wherein GA/Pt-1, GA/Pt-2, GA/Pt-4, GA/Pt-6, GA/Pt-8, GA, and GO represent the graphene/Pt nanocomposite aerogel material of example 2, the graphene/Pt nanocomposite aerogel material of example 1, the graphene/Pt nanocomposite aerogel material of example 3, the graphene/Pt nanocomposite aerogel material of example 4, the graphene/Pt nanocomposite aerogel material of example 5, the graphene aerogel, and the graphene oxide, respectively. XRD analysis and recording are completed in RIGAKU D/Max 2200X-Ray, and Cu-K alpha diffraction
Figure BDA0001745633580000071
The acceleration voltage was 40kV and the current was 40 mA.
It is clear from fig. 6 that graphene oxide has a very distinct and strong characteristic diffraction peak at 10.3 °, which is attributed to the characteristic diffraction peak of the (002) crystal plane of graphene with few sheets, and the spacing between these sheets is calculated to be 0.85nm, which further indicates that the original graphite was successfully oxidatively exfoliated. The disappearance of the characteristic diffraction peak of the graphene oxide at 10.3 degrees can be seen from the XRD pattern of the graphene aerogel, and a more obvious characteristic diffraction peak appears at 23.7 degrees, which indicates that the graphite oxide has a high purityThe alkene was successfully reduced. With regard to graphene/Pt nanocomposite aerogel materials, strong diffraction peaks were detected at 39.7 °, 46.7 °, 67.7 °, 81.2 °, which were assigned to the (111), (200), (220) and (311) crystal planes of Pt nanoparticles, which is consistent with the face-centered cubic structure of (JCPDS No. 4-802). In addition, we can see that from the map, the following H2PtCl6·6H2As the input amount of O increases, these diffraction peaks gradually widen, while the characteristic diffraction peak intensity with respect to graphene oxide gradually weakens, and the diffraction peak intensity with respect to Pt gradually increases. This change may be due to the incorporation of Pt nanoparticles, which increases the sheet spacing of graphene. The reason why the diffraction peak intensity with respect to graphene oxide is not significant may be because the spacing between graphene sheets is much larger than the wavelength intensity of X-ray diffraction.
Experimental example 5
TGA measurements were performed on the graphene/Pt nanocomposite aerogel materials of examples 1-5, and the results are shown in FIG. 7, wherein GA/Pt-1, GA/Pt-2, GA/Pt-4, GA/Pt-6, GA/Pt-8, GA, and C represent the graphene/Pt nanocomposite aerogel material of example 2, the graphene/Pt nanocomposite aerogel material of example 1, the graphene/Pt nanocomposite aerogel material of example 3, the graphene/Pt nanocomposite aerogel material of example 4, the graphene/Pt nanocomposite aerogel material of example 5, the graphene aerogel, and the graphite, respectively.
It can be seen from fig. 7 that the original graphite is more stable and there is substantially no loss of quality with increasing temperature. The thermal weight loss tendency of the graphene aerogel and the GA/Pt nano composite aerogel materials is approximately the same. Between 50 ℃ and 100 ℃, a remarkable quality reduction process can be seen in both graphene aerogel and graphene/Pt composite aerogel materials, which is probably due to the fact that a certain amount of moisture contained in the materials is evaporated by heating. At temperatures between 100 ℃ and 500 ℃ the mass loss may be due to the decomposition of some oxygen-containing functional groups such as carboxyl, anhydride, lactone, etc. It is also seen from the figure that the graphene aerogel tends to be more stable than the graphene/Pt composite aerogel material, probably due to the enhanced stability of the incorporation of Pt nanoparticles.
Experimental example 6
Taking the graphene/Pt nano composite aerogel material in example 1 to perform a p-nitrophenol catalytic reduction experiment, wherein a schematic reduction mechanism diagram is shown in FIG. 8, and the specific steps are as follows:
firstly, mixing 8mL of freshly prepared 25M sodium borohydride solution and 2mL of p-nitrophenol with the concentration of 0.5M; then, 3mg of the graphene/Pt nanocomposite aerogel material sample of example 1 was added to the above mixed solution, and left for a period of time to reduce p-nitrophenol. An ultraviolet absorption spectrogram of the graphene/Pt nanocomposite aerogel material obtained in example 1, which is used for reducing p-nitrophenol after being placed for different time, is shown in fig. 9, wherein an inset is a macroscopic contrast diagram of the p-nitrophenol before and after catalytic reduction. As can be seen from FIG. 9, the characteristic yellow-green color of p-nitrophenol is obviously weakened, and the change of the spectrum of 4-NP (p-nitrophenol) is recorded by an ultraviolet spectrometer, and it is found that the intensity of the ultraviolet absorption peak at 400nm is obviously reduced, a new characteristic diffraction peak appears at 300nm, and the absorption peak around 300nm is the characteristic diffraction peak of p-aminophenol, which indicates that p-nitrophenol is successfully reduced. As can be seen from fig. 9, at about 110min, p-nitrophenol is completely reduced, sodium borohydride serves as a hydrogen source provider in the whole system, and hydrogen is continuously emitted from the reaction bottle during the reduction of p-nitrophenol, which is helpful for the catalysis of metal. The ultraviolet absorption spectrum of the p-nitrophenol is measured on Hitachi U-3900, and the detection wavelength range is 200-600 nm.
Tests prove that the GA/Pt nano composite aerogel material can realize cyclic catalytic reduction of p-nitrophenol in a sodium borohydride atmosphere, the GA/Pt nano composite aerogel material is taken out by using a forceps after the previous cycle catalysis is finished, and then the GA/Pt nano composite aerogel material can be directly put into the next catalysis process for use, the cycle efficiency chart of the GA/Pt nano composite aerogel material in the embodiment 1 for 30 times of cyclic catalysis is shown in figure 10, the GA/Pt nano composite aerogel material is used for catalytically decomposing p-nitrophenol for 20 times continuously and circularly, the decomposition rate of p-nitrophenol can be kept to be 80%, and the catalytic decomposition efficiency of p-nitrophenol for 30 times of cyclic use can also reach 60%. It should be noted that the above data for cyclic catalytic decomposition of p-nitrophenol are measured at 110min of the catalytic reaction. And no Pt nanoparticles were lost throughout the cycle of catalytic reaction. The reason for the gradual decrease in catalytic activity may be due to the blockage of the active sites by the products after the reaction.
According to the method, the graphene/Pt nano composite aerogel materials in the embodiments 1-5 are respectively taken to carry out a p-nitrophenol catalytic reduction experiment, the catalytic time is 110min, and an ultraviolet absorption spectrogram of the reduced p-nitrophenol is shown in a figure 11;
the GA/Pt nano-composite aerogel material obtained in example 1 was used for different NaBH contents4The ultraviolet absorption spectrum of the reduced p-nitrophenol is shown in FIG. 12, and when the amount of the substance is compared with that of 4-NP: NaBH4The GA/Pt-2 catalytic efficiency is highest when the ratio is 1: 100.
According to the above method, the graphene/Pt nanocomposite aerogel materials in examples 1 to 5 were respectively taken to perform catalytic reduction p-nitrophenol experiments, the catalytic time is 110min, the catalytic cycle is performed for 20 times, and the catalytic reduction efficiency is shown in fig. 13, wherein GA/Pt-1, GA/Pt-2, GA/Pt-4, GA/Pt-6, GA/Pt-8, GA, and C respectively represent the graphene/Pt nanocomposite aerogel material in example 2, the graphene/Pt nanocomposite aerogel material in example 1, the graphene/Pt nanocomposite aerogel material in example 3, the graphene/Pt nanocomposite aerogel material in example 4, and the graphene/Pt nanocomposite aerogel material in example 5, as can be seen from fig. 13, GA/Pt-2 has the best circulating catalytic effect.
Comparative example 1
Mixing p-nitrophenol and a sodium borohydride reducing agent, standing for 20 days, finding that the characteristic yellow green color of the p-nitrophenol is not changed, then placing the p-nitrophenol under ultraviolet light for test characterization, and finding that the intensity of a spectrum at 400nm is not changed as shown in FIG. 14, which indicates that the p-nitrophenol cannot be reduced in a single sodium borohydride atmosphere.
Comparative example 2
Adding graphene aerogel into a mixed solution of p-nitrophenol and sodium borohydride, standing for 20 days, wherein the characteristic yellow-green color of the p-nitrophenol is not changed, and then performing ultraviolet spectrometer test characterization, wherein the result is shown in fig. 15, which shows that the characteristic peak intensity at 400nm is not changed basically, which indicates that the graphene aerogel does not contribute to the reduction of the p-nitrophenol in the sodium borohydride solution.
Experiments prove that the graphene/Pt nano composite aerogel material prepared by the method can effectively realize the characteristic of catalytically reducing p-nitrophenol into p-aminophenol in a sodium borohydride atmosphere. The GA/Pt nano composite aerogel material has a macroscopic structure which is easy to transfer from a reaction solution, so that the operation of catalytic reduction is simple and convenient, the catalytic reduction efficiency of the composite material on p-nitrophenol is better maintained, and the decomposition rate of the p-nitrophenol can be kept to 80% after 20 cycles of catalysis. Therefore, the GA/Pt nano composite aerogel material can be applied to sewage treatment and industrial decomposition of p-nitrophenol, and an effective and green scheme is provided for preparing and synthesizing a macroscopic graphene-based/metal nano composite material in the future.
Various other modifications and changes may be made by those skilled in the art based on the above-described technical solutions and concepts, and all such modifications and changes should fall within the scope of the claims of the present invention.

Claims (2)

1. The application of the graphene/Pt nano composite aerogel material in catalytic reduction of p-nitrophenol in a sodium borohydride atmosphere is characterized in that the preparation method of the graphene/Pt nano composite aerogel material comprises the following steps:
1) preparing a graphene oxide solution;
2) 5mL of H2PtCl6•6H2Slowly dripping an isopropanol solution of O into 5mL of the graphene oxide solution obtained in the step 1) to obtain a mixed solution, and ensuring that the concentration of the graphene oxide in the mixed solution is 2 mg/mL; graphene oxide and H in the mixed solution2PtCl6•6H2Mass ratio of OIs 2: 1;
3) magnetically stirring the mixture for 2h, introducing nitrogen for 10min to remove residual oxygen, and cooling at room temperature60Co irradiation, wherein the total irradiation dose is 200kGy, specifically: the irradiation dose rate is 4.55kGy/h, and the total irradiation time is 44 h; after irradiation, cleaning unreacted isopropanol and extra ions by using a mixed solution of water and ethanol in a volume ratio of 1:1 for not less than 5 times, and freeze-drying a product at-5 ℃ for 180 hours after cleaning to obtain the graphene/Pt nano composite aerogel material;
wherein the average thickness of the sheets of the graphene oxide is 1nm, and the distance between the sheets is 0.85 nm; in the graphene/Pt nano composite aerogel material, Pt nano particles are loaded on a graphene sheet layer, and the particle size of the Pt nano particles is 2-5 nm; in a high-resolution transmission electron microscope atlas of the Pt nano-particle, the lattice spacing corresponding to the (111) crystal face and the (220) crystal face of the Pt nano-particle is 0.23nm and 0.20nm respectively; in a Raman spectrum of the graphene/Pt nano composite aerogel material, the intensity ratio of a D peak to a G peak in the graphene/Pt nano composite aerogel material is 1.23; in the XRD pattern of the graphene/Pt nano composite aerogel material, diffraction peaks of (111), (200), (220) and (311) crystal planes of Pt nano particles are respectively at 39.7 degrees, 46.7 degrees, 67.7 degrees and 81.2 degrees;
the graphene/Pt nano composite aerogel material is used for catalytically reducing p-nitrophenol in a sodium borohydride atmosphere, after the graphene/Pt nano composite aerogel material is used for catalytically decomposing the p-nitrophenol for 20 times in a continuous catalytic cycle, the decomposition rate of the p-nitrophenol is kept to be 80%, after the graphene/Pt nano composite aerogel material is used for catalytically decomposing the p-nitrophenol for 30 times in a continuous catalytic cycle, the catalytic decomposition efficiency of the p-nitrophenol is kept to be 60%, and the data of cyclic catalytic decomposition of the p-nitrophenol is measured when the catalytic reaction is carried out for 110min each time; during the circulation catalytic reaction, the loss rate of the Pt nano particles is 0%.
2. The application of the graphene/Pt nanocomposite aerogel material in catalytic reduction of p-nitrophenol in a sodium borohydride atmosphere according to claim 1, wherein in the catalytic reaction, the mass ratio of the p-nitrophenol to the sodium borohydride is 1: 100.
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