C3N4 piezoelectric catalyst doped with gold nanorods as well as preparation method and application of C3N4 piezoelectric catalyst

Abstract

The invention discloses a C3N4 piezoelectric catalyst doped with gold nanorods as well as a preparation method and application of the C3N4 piezoelectric catalyst, relates to the technical field of preparation of catalysts, and overcomes the defects that in H2O2 production through C3N4 piezoelectric catalysis, the adsorption performance on a reaction substrate O2 is poor, electrons / holes are easy to compound, reaction active sites are few and the like. Meanwhile, the Au nanorods are wrapped and tightly combined by the C3N4 and are not prone to leakage, the Au nanorods and the C3N4 form a tight interface, transfer of electrons is promoted, the Au nanorods and the C3N4 generate a synergistic catalysis effect, and the performance of direct generation of H2O2 from O2 and water through piezoelectric catalysis of the C3N4 is improved.

Description

Technical Field

[0001] The invention belongs to the technical field of catalyst preparation, and in particular relates to a C3N4 piezoelectric catalyst doped with gold nanorods, a preparation method and application thereof. Background Art

[0002] Hydrogen peroxide (H2O2), commonly known as hydrogen peroxide, is the cleanest green oxidant. It has the highest active oxygen content (47.1% w / w) and produces no toxic byproducts during the reaction, only H2O and O2. In addition, the energy density of H2O2 is 3.0MJ·L -1 (60wt%H2O2), higher than compressed hydrogen (35MPa, 2.8MJ·L -1 ), is a green, storable and transportable fuel that can be used directly to generate electricity.

[0003] At present, the anthraquinone method and direct synthesis method are commonly used in industry to prepare H2O2. Compared with these two methods, piezoelectric catalytic H2O2 production technology has the advantages of being green, free of secondary pollution, and effective energy conversion. In the piezoelectric catalytic process, through the piezoelectric effect, the piezoelectric catalyst collects energy dispersed in the external environment (such as water flow, friction, vibration) to generate a polarized electric field, and the free charges (electrons / holes) generated thereby trigger a series of redox catalytic reactions, realizing the direct generation of H2O2 from O2 and water. The use of piezoelectric catalysis to produce H2O2 is in its infancy, and the research and development of catalysts with excellent piezoelectric catalytic properties is critical.

[0004] In the prior art, graphite carbon nitride (g-C3N4) has a tri-triazine unit structure with strong polarity superposition and uniformly distributed triangular nanopores. This unique structure enables g-C3N4 to exhibit extremely strong dipole networks and piezoelectric polarization effects. At the same time, the raw materials for synthesizing g-C3N4 are abundant and low in cost, and it has great development potential as a piezoelectric catalyst for producing H2O2. However, pure g-C3N4 has poor adsorption performance for the reaction substrate O2, and the electrons / holes generated by the piezoelectric effect are easy to recombine, and there are fewer active sites and slow electron transfer defects, so its piezoelectric catalytic efficiency for producing H2O2 is very low.

[0005] Therefore, it is of great significance to adopt effective strategies to develop and design g-C3N4-based catalysts with high-voltage electrocatalytic performance for the piezoelectric catalytic preparation of H2O2. Summary of the invention

[0006] Purpose of the invention: To address the problems in the prior art that g-C3N4 piezoelectric catalysts have poor adsorption performance for the reaction substrate O2, easy recombination of electrons / holes, and few reaction active sites in piezoelectric catalytic production of H2O2, a C3N4 piezoelectric catalyst doped with gold nanorods, a preparation method and its application are provided.

[0007] The present invention provides a method for preparing a C3N4 piezoelectric catalyst doped with gold nanorods, comprising the following steps:

[0008] Step 1, preparing a suspension of gold nanorods;

[0009] Step 2, preparing a g-C3N4 precursor material;

[0010] Step 3, preparation of gold nanorod-doped C3N4 piezoelectric catalyst: the gold nanorod suspension and the g-C3N4 precursor are mixed in an agate mortar, ground and dried, and then transferred to a crucible. The crucible is placed in a muffle furnace and heated to a certain temperature at a certain heating rate and kept warm for a period of time. When the muffle furnace cools to room temperature, the gold nanorod-doped C3N4 piezoelectric catalyst is obtained.

[0011] Furthermore, the specific operation steps of step 1 are as follows:

[0012] Step 1.1, dissolving HAuCl4·3H2O and tetraoctylammonium bromide in deionized water, placing in a flask and stirring for a period of time, adding NaBH4 ice water solution at a stirring rate of 700-900 rpm to obtain a gold seed solution;

[0013] Step 1.2, tetraoctylammonium bromide, HAuCl4·3H2O, and AgNO3 solution are mixed in deionized water, placed in a flask and stirred for a period of time, ascorbic acid solution is added, and the flask is placed in a water bath; the gold seed solution prepared in step 1.1 is added, stirring is continued for a period of time, and excess tetraoctylammonium bromide is removed by centrifugation to obtain a suspension containing gold nanorods.

[0014] Furthermore, in the step 1.1: the mass ratio of HAuCl4·3H2O to tetraoctylammonium bromide is 1:360; the mass ratio of HAuCl4·3H2O to deionized water is 1:10000; the mass ratio of HAuCl4·3H2O to NaBH4 is 7400:1, and the concentration of the added NaBH4 icy water solution is 10 mmol / L;

[0015] In the step 1.2: the mass ratio of HAuCl4·3H2O to tetraoctylammonium bromide is 1:180; the mass ratio of HAuCl4·3H2O to deionized water is 0.0002:1; the mass ratio of HAuCl4·3H2O to AgNO3 is 588:1, and the concentration of the AgNO3 solution is 4 mmol / L; the mass ratio of HAuCl4·3H2O to ascorbic acid is 0.0018:1, and the concentration of the ascorbic acid solution is 80 mmol / L; the mass ratio of the mass of gold seeds in the gold seed solution to HAuCl4·3H2O is 1:8.

[0016] Furthermore, in step 1.2: the water bath temperature is 25-30° C.; after adding the gold seed solution, the stirring time is more than 1 hour.

[0017] Furthermore, in step 1.2: the length of the obtained gold nanorods is 20-60 nanometers, and the particle size is 10-20 nanometers.

[0018] Furthermore, the specific operation of step 2 is: dissolving melamine and cyanuric acid in water respectively, heating in a water bath and stirring continuously until they are completely dissolved; adding the obtained melamine solution dropwise to the cyanuric acid solution, stirring for a period of time, standing to room temperature, and then centrifuging the obtained precipitate, washing the solid three times with anhydrous ethanol, and then putting it into an oven to dry, to obtain a g-C3N4 precursor substance.

[0019] Furthermore, in step 2:

[0020] The mass ratio of melamine to cyanuric acid is 1:1, the water bath temperature is 50-60°C; the stirring time is 30 minutes, the drying temperature is 60°C, and the drying time is 10 hours.

[0021] Furthermore, in step 3:

[0022] The mass of the gold nanorods in the gold nanorod suspension is 0.1%-1% of the mass of the gold nanorods and the g-C3N4 precursor, the heating rate is 5°C / min, the insulation time is 1.5-4 hours, and the insulation temperature is 480-520°C.

[0023] The invention also discloses a C3N4 piezoelectric catalyst doped with gold nanorods prepared by the method and its application in piezoelectric catalytic production of H2O2.

[0024] Beneficial effects: (1) The gold nanorod-doped C3N4 piezoelectric catalyst prepared by the present invention has good piezoelectric hydrogen peroxide production performance compared to the C3N4 catalyst in the prior art. The loaded Au nanoclusters provide more reactive sites to improve the adsorption performance of the reaction substrate O2 during the piezoelectric catalysis process. At the same time, the gold nanoclusters have good electron transfer performance, which promotes the separation of electrons and holes in the piezoelectric catalysis, thereby improving the performance of H2O2 production; (2) The catalyst of the present invention has high stability in the piezoelectric catalysis of H2O2 under cyclic ultrasonic radiation. The catalyst Au nanorods of the present invention are tightly wrapped and bound by C3N4 and are not easy to leak. The Au nanorods and C3N4 form a tight interface, which promotes the transfer of electrons. The two have a synergistic catalytic effect, which improves the catalytic activity of the catalyst. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 is a transmission electron microscope image of the gold nanorods prepared in Example 1;

[0026] Figure 2 This is a transmission electron microscope image of the C3N4 catalyst prepared in Example 1;

[0027] Figure 3 This is the transmission electron microscopy image of the Au / C3N4 catalyst prepared in Example 1. DETAILED DESCRIPTION

[0028] The following embodiments are provided for a better understanding of the present invention. The following embodiments do not limit the content and protection scope of the present invention. Any product identical or similar to the present invention obtained by anyone under the inspiration of the present invention or by combining the present invention with the features of other prior arts shall fall within the protection scope of the present invention.

[0029] If no specific experimental steps or conditions are specified in the examples, the conventional experimental steps or conditions described in the literature in the field can be used. If no manufacturer is specified for the reagents or instruments used, they are all conventional reagent products that can be obtained commercially.

[0030] Example 1

[0031] (1) Preparation of gold nanorods

[0032] 1 mg HAuCl4·3H2O and 360 mg tetraoctylammonium bromide were dissolved in 10 ml deionized water, then placed in a 25 ml three-necked flask and magnetically stirred for 10 min. 0.6 ml of 10 mmol / L NaBH4 ice water solution was added under continued strong stirring (900 rpm) to obtain a gold seed solution.

[0033] 360 mg of tetraoctylammonium bromide, 2 mg of HAuCl4·3H2O, and 50 μl of 4 mmol / l AgNO3 solution were mixed in deionized water and placed in a three-necked flask. After stirring for 10 minutes, 70 μl of 80 mmol / l ascorbic acid solution was added. The three-necked flask was placed in a water bath at a temperature of 25-30°C. Then 12 μl of gold seed solution was added and stirring continued for 1 hour. Excess tetraoctylammonium bromide was removed by centrifugation to obtain a suspension containing gold nanorods. The transmission electron microscope image of the obtained gold nanorods is shown below. Figure 1 As shown, the prepared gold nanorods have a length of 20-60 nanometers and a particle size of 10-20 nanometers.

[0034] (2) preparing g-C3N4 precursor material;

[0035] 2 g of melamine and 2 g of cyanuric acid were dissolved in 100 ml of water respectively, heated in a water bath (50-60°C) and stirred continuously until they were completely dissolved. The obtained melamine solution was added dropwise to the cyanuric acid solution, stirred for a period of time, and allowed to stand at room temperature, and then the obtained precipitate was centrifuged, the solid was washed three times with anhydrous ethanol, and then placed in an oven at 60°C for 10 hours to obtain a g-C3N4 precursor material.

[0036] (3) Preparation of Au / C3N4 (C3N4 piezoelectric catalyst doped with gold nanorods)

[0037] 10 ml of the suspension containing gold nanorods and the g-C3N4 precursor were mixed, ground and dried in an agate mortar, and then transferred to a crucible. The crucible was placed in a muffle furnace and heated to 500°C at a heating rate of 5°C / min, and kept warm for 2 hours. When the muffle furnace was cooled to room temperature, the Au / C3N4 sample (C3N4 piezoelectric catalyst doped with gold nanorods) was obtained, which was recorded as sample A. Figure 3 This is the TEM image of Au / C3N4 sample. Figure 3 It can be seen that C3N4 wrapped the gold nanorods.

[0038] The elemental analysis instrument measured that the mass fraction of gold nanorods in the sample was 0.1%. The specific surface area performance test of sample A was carried out by the specific surface area measuring instrument. The test results showed that the specific surface area of ​​sample A was 8.4m 2 / g, and the average pore size is 33nm.

[0039] Comparative Example 1

[0040] Preparation of C3N4 catalyst: 2 grams of melamine and 2 grams of cyanuric acid are dissolved in water respectively, heated in a water bath (50-60°C) and stirred continuously until they are completely dissolved. The obtained melamine solution is added dropwise to the cyanuric acid solution, stirred for a period of time, and allowed to stand at room temperature, and then the obtained precipitate is centrifuged, the solid is washed three times with anhydrous ethanol, and then placed in an oven at 60°C for 10 hours to obtain a g-C3N4 precursor substance. After the g-C3N4 precursor is ground in an agate mortar, it is transferred to a crucible, and finally the crucible is placed in a muffle furnace and heated to 500°C at a heating rate of 5°C / min, and kept warm for 2 hours. When the muffle furnace is cooled to room temperature, a C3N4 catalyst sample is obtained. Figure 2 TEM image of C3N4 catalyst sample. Figure 2 It can be seen that the C3N4 catalyst is in the form of flakes.

[0041] Example 2

[0042] This embodiment provides a method for preparing a C3N4 piezoelectric catalyst doped with gold nanorods. The preparation process is the same as that of Example 1, except that, during the preparation of Au / C3N4 in this embodiment, 20 ml of a suspension containing gold nanorods is taken, and the mass fraction of gold nanorods doped in the obtained Au / C3N4 sample is 0.2%, which is recorded as sample B.

[0043] The specific surface area performance of sample B was tested using a specific surface area meter. The test results showed that the specific surface area of ​​sample B was 8.0 m 2 / g, and the average pore size is 33nm.

[0044] Example 3

[0045] This embodiment provides a method for preparing a C3N4 piezoelectric catalyst doped with gold nanorods. The preparation process is the same as that of Example 1, except that, in the process of preparing Au / C3N4 in this embodiment, 40 ml of a suspension containing gold nanorods is taken, and the mass fraction of gold nanorods doped in the obtained Au / C3N4 sample is 0.4%, and an Au / C3N4 sample is obtained, which is recorded as C.

[0046] The specific surface area performance of Au / C3N4 sample was tested by using specific surface area meter. The test results showed that the specific surface area of ​​Au / C3N4 sample was 7.8m 2 / g, and the average pore size is 34nm.

[0047] Example 4

[0048] This embodiment provides a method for preparing a C3N4 piezoelectric catalyst doped with gold nanorods. The preparation process is the same as that of Example 1, except that, in the process of preparing Au / C3N4 in this embodiment, 60 ml of a suspension containing gold nanorods is taken, and the mass fraction of gold nanorods doped in the obtained Au / C3N4 sample is 0.6%, and an Au / C3N4 sample is obtained, which is recorded as sample D.

[0049] The specific surface area performance of sample D was tested using a specific surface area meter. The test results showed that the specific surface area of ​​sample D was 7.5 m 2 / g, and the average pore size is 34nm.

[0050] Example 5

[0051] This embodiment provides a method for preparing a C3N4 piezoelectric catalyst doped with gold nanorods. The preparation process is the same as that of Example 1, except that, during the preparation of Au / C3N4 in this embodiment, 80 ml of a suspension containing gold nanorods is taken, and the obtained Au / C3N4 sample is recorded as sample E. The mass fraction of gold nanorods doped in sample E is 0.8%.

[0052] The specific surface area performance of sample E was tested using a specific surface area meter. The test results showed that the specific surface area of ​​sample E was 7.4 m 2 / g, and the average pore size is 33nm.

[0053] Example 6

[0054] This embodiment provides a method for preparing a C3N4 piezoelectric catalyst doped with gold nanorods. The preparation process is the same as that of Example 1, except that, during the preparation of Au / C3N4 in this embodiment, 100 ml of a suspension containing gold nanorods is taken, and the obtained Au / C3N4 sample is recorded as sample F, and the mass fraction of gold nanorods doped in sample F is 1%.

[0055] The specific surface area performance of sample F was tested using a specific surface area meter. The test results showed that the specific surface area of ​​sample F was 7.2 m 2 / g, and the average pore size is 33nm.

[0056] Test Example 1

[0057] Catalyst activity test: The catalytic activity test of piezoelectric catalysis to produce H2O2 was carried out. In a beaker, 25 mg of the catalyst was dispersed in 50 ml of pure water and stirred in a dark environment for 1 hour. Then an ultrasonic cleaner with a power of 300 W was used as an external ultrasonic radiation source for the H2O2 production test. The ultrasonic cleaner was filled with circulating condensed water to ensure that the temperature remained at room temperature during the reaction. Take 2 ml of the dispersion from the beaker every hour and centrifuge to remove the catalyst residue. Keep 1 ml of the upper clear liquid for further use. The H2O2 concentration was determined by iodine titration. 1 mL of 0.4 M KI solution and 1 mL of 0.1 M potassium hydrogen phthalate solution were added to the clear liquid respectively and color was developed in the dark for 1 h (H2O2+3I - +2H + →I3 - +2H2O), and the absorbance of the solution after the reaction at 350nm was measured by UV spectrophotometer (I3 - ), and the concentration of H2O2 was calculated using the fitted absorbance-concentration standard curve.

[0058] The calculated results of piezoelectric catalytic H2O2 production under ultrasonic irradiation for 3 hours are shown in Table 1 below.

[0059] Table 1 Test results of different catalyst activities

[0060]

[0061] From the data comparison in Table 1 above, it can be seen that the C3N4 piezoelectric catalyst doped with gold nanorods prepared by the present invention has good piezoelectric hydrogen peroxide production performance compared with the C3N4 catalyst in the prior art. The loaded Au nanoclusters provide more reactive sites to improve the adsorption performance of the reaction substrate O2 during the piezoelectric catalysis process. At the same time, the gold nanoclusters have good electron transfer performance, which promotes the separation of electrons and holes in the piezoelectric catalysis, thereby improving the performance of H2O2 production.

[0062] Test Example 2

[0063] Catalyst stability test: 25 mg of the gold nanorod-doped C3N4 piezoelectric catalyst prepared in Example 3 of the present invention was subjected to a cyclic piezoelectric catalytic hydrogen peroxide production test. The stability test of hydrogen peroxide production in the first 3 h, second 3 h, third 3 h and fourth 3 h was calculated respectively. The results are shown in Table 2.

[0064] Table 2 Hydrogen peroxide production stability test results of piezoelectric catalysts

[0065]

[0066] The catalyst of the present invention has high stability in producing H2O2 under cyclic ultrasonic radiation piezoelectric catalysis, and no Au nanorods are found in the aqueous solution, indicating that the Au nanorods of the catalyst of the present invention are tightly wrapped and bound by C3N4 and are not easy to leak. The Au nanorods and C3N4 form a tight interface, which promotes the transfer of electrons. The two have a synergistic catalytic effect, thereby improving the catalytic activity of the catalyst.

[0067] As described above, although the present invention has been shown and described with reference to specific preferred embodiments, it should not be construed as limiting the present invention itself. Various changes in form and details may be made without departing from the spirit and scope of the present invention.

Claims

1. A method for preparing a C3N4 piezoelectric catalyst doped with gold nanorods, characterized in that: The steps include: Step 1, preparing a suspension of gold nanorods; Step 2, preparing a g-C3N4 precursor material; Step 3: Preparation of C3N4 piezoelectric catalyst doped with gold nanorods: The suspension of gold nanorods and the g-C3N4 precursor are mixed, ground and dried in an agate mortar, and then transferred to a crucible. The crucible is placed in a muffle furnace and heated to a certain temperature at a certain heating rate and kept warm for a period of time. When the muffle furnace cools to room temperature, the C3N4 piezoelectric catalyst doped with gold nanorods is obtained.

2. The preparation method according to claim 1, characterized in that: The specific steps of step 1 are as follows: Step 1.1, dissolving HAuCl4·3H2O and tetraoctylammonium bromide in deionized water, placing in a flask and stirring for a period of time, adding NaBH4 ice water solution at a stirring rate of 700-900 rpm to obtain a gold seed solution; Step 1.2, tetraoctylammonium bromide, HAuCl4·3H2O, and AgNO3 solution are mixed in deionized water, placed in a flask and stirred for a period of time, ascorbic acid solution is added, and the flask is placed in a water bath; the gold seed solution prepared in step 1.1 is added, stirring is continued for a period of time, and excess tetraoctylammonium bromide is removed by centrifugation to obtain a suspension containing gold nanorods.

3. The preparation method according to claim 2, characterized in that: In the step 1.1: the mass ratio of HAuCl4·3H2O to tetraoctylammonium bromide is 1:360; the mass ratio of HAuCl4·3H2O to deionized water is 1:10000; the mass ratio of HAuCl4·3H2O to NaBH4 is 7400:1, and the concentration of the added NaBH4 icy water solution is 10 mmol / L; In the step 1.2: the mass ratio of HAuCl4·3H2O to tetraoctylammonium bromide is 1:180; the mass ratio of HAuCl4·3H2O to deionized water is 0.0002:1; the mass ratio of HAuCl4·3H2O to AgNO3 is 588:1, and the concentration of the AgNO3 solution is 4 mmol / L; the mass ratio of HAuCl4·3H2O to ascorbic acid is 0.0018:1, and the concentration of the ascorbic acid solution is 80 mmol / L; the mass ratio of the mass of gold seeds in the gold seed solution to HAuCl4·3H2O is 1:

8.

4. The preparation method according to claim 2, characterized in that: In step 1.2: The water bath temperature was 25-30°C; after adding the gold seed solution, the stirring time was more than 1 hour.

5. The preparation method according to claim 2, characterized in that: In the step 1.2: the length of the obtained gold nanorods is 20-60 nanometers, and the particle size is 10-20 nanometers.

6. The preparation method according to claim 1, characterized in that: The specific operations of step 2 are: Melamine and cyanuric acid are dissolved in water respectively, heated in a water bath and stirred continuously until they are completely dissolved; the obtained melamine solution is added dropwise to the cyanuric acid solution, stirred for a period of time, allowed to stand to room temperature, and then the obtained precipitate is centrifuged, the solid is washed three times with anhydrous ethanol, and then placed in an oven for drying to obtain a g-C3N4 precursor substance.

7. The preparation method according to claim 6, characterized in that: In step 2: The mass ratio of melamine to cyanuric acid is 1:1, the water bath temperature is 50-60°C; the stirring time is 30 minutes, the drying temperature is 60°C, and the drying time is 10 hours.

8. The preparation method according to claim 1, characterized in that: In step 3: The mass of the gold nanorods in the gold nanorod suspension is 0.1%-1% of the mass of the gold nanorods and the g-C3N4 precursor, the heating rate is 5°C / min, the insulation time is 1.5-4 hours, and the insulation temperature is 480-520°C.

9. A C3N4 piezoelectric catalyst doped with gold nanorods, characterized in that: Obtained by the preparation method described in any one of claims 1 to claim 8.

10. Use of the gold nanorod-doped C3N4 piezoelectric catalyst according to claim 9 in piezoelectric catalytic production of H2O2.

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