Method for preparing a hybrid of carbon nitride and platinum nanoparticles using a soft template

Abstract

The present invention relates to the fields of colloids, semiconductors, photocatalysis, battery electrodes, etc., and particularly relates to a method for preparing a hybrid of carbon nitride and nano-platinum by using a soft template. First, the preparation of Pickering fine emulsion of nano-platinum is realized by the soft template method; then, the re-dispersion and stabilization of the precursor in the Pickering inverse fine emulsion are completed by using the solubility of the carbon nitride precursor; after the emulsion is coated on a film, a hybrid of carbon nitride and nano-platinum is finally formed by heat treatment, and the size of the hybrid is about 100 nanometers and the distribution is uniform.

Description

Technical Field

[0001] The present invention relates to the fields of colloids, semiconductors, photocatalysis, battery electrodes, etc., and particularly relates to a method for preparing a hybrid of carbon nitride and nano-platinum by using a soft template. Background Art

[0002] Carbon nitride is a semiconductor photocatalytic material with a two-dimensional layered structure and stable chemical properties. Commonly used preparation methods include shock wave compression, high-pressure pyrolysis, ion implantation, reactive sputtering, plasma chemical vapor deposition, electrochemical deposition, ion beam deposition, low-energy ion radiation, pulsed arc discharge, pulsed laser induction, etc.; graphitic carbon nitride is synthesized by thermal polycondensation method, solvothermal method, solid-phase synthesis method and electrochemical deposition method.

[0003] Platinum metal has excellent properties and is widely used. In the chemical industry, it is used to manufacture high-grade chemical utensils, platinum crucibles, electrodes and catalysts for accelerating the reaction rate. Especially in the automotive industry, the role of platinum in exhaust gas treatment is irreplaceable, and its consumption almost accounts for half of the industrial consumption of platinum. Therefore, how to save the amount of platinum metal on the premise of ensuring the catalyst performance has become an inevitable development of the existing technology. Summary of the Invention

[0004] The purpose of the present invention is to prepare a hybrid of carbon nitride and nano-platinum by using a soft template method and realizing it through Pickering inverse fine emulsion and film coating heat treatment.

[0005] Nanotechnology plays an important role in materials science. Using the soft template method, nano-platinum is reduced and formed in the Pickering inverse fine emulsion, and the Pickering inverse fine emulsion of the carbon nitride precursor and nano-platinum is redispersed; the hybrid of carbon nitride and nano-platinum is realized by film coating heat treatment, and the hybrid has advantages in terms of size and distribution.

[0006] The above method is carried out according to the following steps:

[0007] (1) Preparation of soft template Pickering inverse fine emulsion:

[0008] At room temperature, a polymer dissolved in a quantitative amount of hot water and a quantitative aqueous solution of soluble platinum metal salt are dropped at a fixed rate into an oily solution cooled by ice water under a high-speed shearer for comminution. After the high-speed shearer comminutes for a fixed time, a soft template Pickering inverse fine emulsion containing a water-soluble platinum salt can be obtained.

[0009] Among them, the polymer is polyvinyl alcohol, which is a commercially available finished product, the number of polymerization units is 1700 - 2000, and the degree of alcoholysis is 90 - 99%; the temperature of the hot water is 70 - 80 °C, and the mass concentration of polyvinyl alcohol dissolved in the hot water is 0.5 - 1.0%; its dropping rate is 5% of the mass fraction of the polyvinyl alcohol hot water solution per minute.

[0010] The aqueous solution of soluble platinum salt is an aqueous solution of sodium chloroplatinate, potassium chloroplatinate or ammonium chloroplatinate with a mass concentration of 1-3%, and its dropping rate is 20% of the mass fraction of the platinum salt aqueous solution per minute.

[0011] The oily solvent is cyclohexane.

[0012] The mass ratio of the aqueous solution of polyvinyl alcohol, the solution of soluble platinum salt and the oily solvent is 10:0.1-0.5:50.

[0013] The rotation speed of the high-speed shearing machine is 20,000 revolutions per minute, the crushing time is 5 minutes, and the temperature is controlled at 20 °C.

[0014] (2) Preparation of Pickering fine emulsion of nano-platinum:

[0015] Step (2) is operated in an operating cabinet under nitrogen protection: at room temperature, the soft-template Pickering inverse fine emulsion containing soluble platinum salt prepared in step (1) is transferred into a device with heating and magnetic stirring, a quantitative reducing agent is added dropwise, and after gradually heating up and keeping warm for a certain time by magnetic stirring and then cooling to room temperature, the Pickering inverse fine emulsion of nano-platinum is completed.

[0016] Among them, the reducing agent is hydrazine hydrate, sodium borohydride, aqueous formaldehyde solution or aqueous sodium formate solution, etc. The mass concentration of the aqueous formaldehyde solution is 17%, and the mass concentration of the aqueous sodium formate solution is 10%.

[0017] The mass ratio of the reducing agent to the aqueous solution of soluble platinum metal salt in step (1) is 1.0-1.2:1, and the dropping rate of the reducing agent is 20% of the mass fraction of the reducing agent per minute.

[0018] The magnetic stirring gradually heats up to 60-65 °C, and the heat preservation time is 60-90 minutes.

[0019] (3) Preparation of carbon nitride and nano-platinum nanohybrid:

[0020] At room temperature, the nano-platinum Pickering inverse fine emulsion prepared in step (2) is transferred to an ultrasonic biological crusher for crushing, and at the same time, a quantitative aqueous solution of carbon nitride precursor is added dropwise to the fine emulsion prepared in step (2) at a fixed rate, and after crushing for a fixed time, the loading of the carbon nitride precursor into the nano-platinum Pickering fine emulsion is completed; at room temperature, the carbon nitride precursor is loaded into the nano-platinum Pickering inverse fine emulsion and dried on a purified quartz glass by spin coating, and after heat treatment of the film, a carbon nitride and nano-platinum hybrid is obtained.

[0021] Among them, the carbon nitride precursor is melamine or urea, etc., the mass concentration of its hot aqueous solution is 2%, and the temperature of the hot aqueous solution is 60 - 65°C; the mass ratio of the carbon nitride precursor hot aqueous solution to the salt solution in step (1) is 2:1, and the dropping rate is 10% of the mass fraction of the carbon nitride precursor aqueous solution per minute.

[0022] The ultrasonic biological crusher has a high power of 500W and is crushed at 80% power for 10 minutes.

[0023] The thickness of the spin-coated film is controlled at 150 - 200 microns.

[0024] In the heat treatment method, under reduced pressure nitrogen protection, the pressure is 500 - 2000 Pa, the heating rate is 5°C per minute, the holding temperature is 150 - 200°C, and the heat treatment time is 2 - 3 hours.

[0025] In the present invention, the Pickering fine emulsion of nano-platinum is firstly prepared by the soft template method; then, the solubility of the carbon nitride precursor is utilized to complete the re-dispersion and stabilization of the precursor in the Pickering inverse fine emulsion; after the emulsion is coated into a film, the heat treatment is finally used to form the carbon nitride and nano-platinum nano hybrid.

[0026] The present invention has the following advantages:

[0027] 1. Utilize the solubility difference of polymers to form a soft film template Pickering inverse fine emulsion containing soluble salts;

[0028] 2. Utilize the re-dispersion method to form a carbon nitride precursor loaded into the nano-platinum Pickering inverse fine emulsion;

[0029] 3. The thin film is heat-treated to form a carbon nitride and nano-platinum hybrid; the size of the hybrid is about 100 nanometers and is evenly distributed. Description of the Drawings

[0030] Figure 1 It is an electron projection electron microscope picture of the carbon nitride precursor loaded into the nano-platinum Pickering fine emulsion in step (3) of Example 1.

[0031] Figure 2 It is a scanning electron microscope picture of the carbon nitride and nano-platinum hybrid after heat treatment in step (3) of Example 1. Detailed Embodiments

[0032] The technical solutions of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0033] Example 1

[0034] (1) Preparation of soft-template Pickering inverse miniemulsion:

[0035] At room temperature, 10 g of a 0.5% polyvinyl alcohol aqueous solution (the number of polymerization units of polyvinyl alcohol is 1700, and the degree of alcoholysis is 90%) at 70 °C was added dropwise to 50 g of cyclohexane cooled by ice water under a high-speed shear machine at a dropping rate of 0.5 g / min. At the same time, 0.1 g of an aqueous solution of ammonium chloroplatinate with a mass concentration of 1% was added dropwise at a rate of 0.02 g / min for comminution. The rotational speed of the high-speed shear machine was 20,000 r / min, the comminution time was 5 min, and the temperature was controlled at 20 °C. A soft-template Pickering inverse miniemulsion containing water-soluble platinum salt was obtained. The Z-average particle size of the inverse miniemulsion was 180 nm.

[0036] (2) Preparation of Pickering miniemulsion of platinum nanoparticles:

[0037] Step (2) was carried out in an operating cabinet under nitrogen protection: At room temperature, the soft-template Pickering inverse miniemulsion containing water-soluble platinum salt prepared in step (1) was transferred into a heating magnetic stirrer, and 0.1 g of reducing agent hydrazine hydrate was added dropwise at a rate of 0.02 g / min. The magnetic stirrer was gradually heated to 60 °C, and the holding time was 60 min. The Pickering inverse miniemulsion of platinum nanoparticles was completed.

[0038] (3) Preparation of carbon nitride and platinum nanoparticle hybrids:

[0039] At room temperature, the Pickering inverse miniemulsion of platinum nanoparticles prepared in step (2) was transferred to an ultrasonic cell disruptor for comminution. At the same time, 0.2 g of a 2% melamine aqueous solution at 60 °C was added dropwise to the miniemulsion prepared in step (2) at a rate of 0.02 g / min. The ultrasonic cell disruptor was operated at a high power of 500 W and a power state of 80% for 10 min to complete the loading of the carbon nitride precursor into the Pickering miniemulsion of platinum nanoparticles.

[0040] Under room temperature conditions, the carbon nitride precursor loaded into the Pickering inverse miniemulsion of platinum nanoparticles was spin-coated on a purified quartz glass. The thickness of the spin-coated film was controlled at 150 μm, and the dried film was heat-treated under reduced pressure with nitrogen protection, with a pressure of 2000 Pa; the heating rate was 5 °C / min, the holding temperature was 150 °C, and the heat treatment time was 3 h. A carbon nitride and platinum nanoparticle hybrid was obtained.

[0041] Figure 1 Electron projection electron microscopy image of the carbon nitride precursor loaded into the Pickering miniemulsion of platinum nanoparticles in step (3) (the particle size is 120 nm, and the black dots on the surface are platinum nanoparticles ----- 50 nm)

[0042] Figure 2Scanning electron microscope image of the carbon nitride and platinum nanoparticle hybrid after heat treatment in step (3) (the bright spots on the surface are platinum nanoparticles, and the raised areas are carbon nitride ----- 50 nanometers)

[0043] Example 2

[0044] (1) Preparation of soft-template Pickering inverse miniemulsion:

[0045] At room temperature, 10 g of an 80 °C aqueous solution of polyvinyl alcohol with a mass concentration of 1.0% (the number of polymerization units of polyvinyl alcohol is 2000, and the degree of alcoholysis is 99%) was added dropwise to 50 g of cyclohexane cooled with ice water under a high-speed shearer at a dropping rate of 0.5 g / min; at the same time, 0.5 g of an aqueous solution of ammonium chloroplatinate with a mass concentration of 3% was added dropwise at a rate of 0.10 g / min, and then crushed. The rotation speed of the high-speed shearer was 20,000 revolutions per minute, the crushing time was 5 minutes, and the temperature was controlled at 20 °C. A soft-template Pickering inverse miniemulsion containing water-soluble platinum salt was obtained. The Z-average particle size of the inverse miniemulsion was 120 nanometers.

[0046] (2) Preparation of Pickering miniemulsion of platinum nanoparticles:

[0047] Step (2) was carried out in an operating cabinet under nitrogen protection: at room temperature, the soft-template Pickering inverse miniemulsion containing water-soluble platinum salt prepared in step (1) was transferred into a heating magnetic stirrer, 0.6 g of sodium borohydride was added dropwise at a rate of 0.12 g / min, and the magnetic stirrer was gradually heated to 65 °C and kept warm for 90 minutes. The Pickering inverse miniemulsion of platinum nanoparticles was completed.

[0048] (3) Preparation of carbon nitride and platinum nanoparticle hybrids:

[0049] At room temperature, the Pickering inverse miniemulsion of platinum nanoparticles prepared in step (2) was transferred to an ultrasonic cell disruptor for crushing. At the same time, 1.0 g of a 65 °C aqueous solution of melamine with a mass concentration of 2% was added dropwise to the miniemulsion prepared in step (2) at a rate of 0.10 g / min. The ultrasonic cell disruptor was operated at a high power of 500 W and crushed at 80% power for 10 minutes to complete the loading of the carbon nitride precursor into the Pickering miniemulsion of platinum nanoparticles.

[0050] At room temperature, the carbon nitride precursor was loaded into the Pickering inverse miniemulsion of platinum nanoparticles and spin-coated on a purified quartz glass. The thickness of the spin-coated film was controlled at 200 micrometers. After drying, the film was heat-treated under reduced pressure with nitrogen protection, with a pressure of 500 Pa; the heating rate was 5 °C / min, the holding temperature was 200 °C, and the heat treatment time was 2 hours. A carbon nitride and platinum nanoparticle hybrid was obtained. The size of the platinum dots was less than 3 nanometers, and the size of the carbon nitride was less than 70 nanometers.

[0051] Example 3

[0052] (1) Preparation of soft-template Pickering inverse miniemulsion:

[0053] At room temperature, 10 g of a 0.75% polyvinyl alcohol aqueous solution in hot water at 70 °C (the number of polymerization units of polyvinyl alcohol is 1800, and the degree of alcoholysis is 95%) was added dropwise to 50 g of cyclohexane cooled with ice water under a high-speed shear machine at a dropping rate of 0.5 g / min. At the same time, 0.3 g of an aqueous solution of potassium chloroplatinate with a mass concentration of 2.0% was added dropwise at a rate of 0.06 g / min for comminution. The rotation speed of the high-speed shear machine was 20,000 r / min, the comminution time was 5 min, and the temperature was controlled at 20 °C. Thus, a soft-template Pickering inverse miniemulsion containing water-soluble platinum salt was obtained. The Z-average particle size of the inverse miniemulsion was 150 nm.

[0054] (2) Preparation of Pickering miniemulsion of platinum nanoparticles:

[0055] Step (2) was carried out in an operating cabinet under nitrogen protection: At room temperature, the soft-template Pickering inverse miniemulsion containing water-soluble platinum salt prepared in step (1) was transferred into a heating magnetic stirrer, and 0.33 g of an aqueous solution of formaldehyde with a mass concentration of 10% was added dropwise at a rate of 0.066 g / min. The magnetic stirrer was gradually heated to 62 °C, and the holding time was 70 min. The Pickering inverse miniemulsion of platinum nanoparticles was completed.

[0056] (3) Preparation of carbon nitride and platinum nanoparticle hybrids:

[0057] At room temperature, the Pickering inverse miniemulsion of platinum nanoparticles prepared in step (2) was transferred to an ultrasonic cell disruptor for comminution. At the same time, 0.6 g of a 2% urea aqueous solution in hot water at 62 °C was added dropwise to the miniemulsion prepared in step (2) at a rate of 0.06 g / min. The ultrasonic cell disruptor with a high power of 500 W was comminuted at 80% power for 10 min to complete the loading of the carbon nitride precursor into the Pickering miniemulsion of platinum nanoparticles. Under room temperature conditions, the carbon nitride precursor loaded into the Pickering inverse miniemulsion of platinum nanoparticles was spin-coated on a purified quartz glass. The thickness of the spin-coated film was controlled at 180 μm, and the dried film was heat-treated under reduced pressure with nitrogen protection, with a pressure of 1000 Pa, a heating rate of 5 °C / min, a holding temperature of 180 °C, and a heat treatment time of 2.5 h. A carbon nitride and platinum nanoparticle hybrid was obtained. The size of the platinum dots was less than 2 nm, and the size of the carbon nitride was less than 60 nm.

[0058] The above description of the embodiments is to enable those of ordinary skill in the art to understand and apply the present invention. It is obvious that those skilled in the art can easily make various modifications to these embodiments and apply the general principles described herein to other embodiments without creative efforts. Therefore, the present invention is not limited to the embodiments herein, and all modifications made by those skilled in the art to the present invention according to the disclosure of the present invention should be within the protection scope of the present invention.

Claims

1. A carbon nitride and nano-platinum hybrid, characterized in that, The preparation method of the carbon nitride and nano-platinum hybrid is as follows: (1)Preparation of soft-template Pickering inverse fine emulsion: At room temperature, a polymer dissolved in a quantitative amount of hot water and an aqueous solution of a quantitative soluble platinum metal salt are dropped into an oily solution cooled by ice water under a high-speed shearer at a fixed rate for pulverization. After the high-speed shearer pulverizes for a fixed time, a soft-template Pickering inverse fine emulsion containing the water-soluble platinum salt is obtained; The polymer is polyvinyl alcohol, the number of polymerization units is 1700 - 2000, and the degree of alcoholysis is 90 - 99%; the aqueous solution of the soluble platinum salt is an aqueous solution of sodium chloroplatinate, potassium chloroplatinate or ammonium chloroplatinate with a mass concentration of 1 - 3%; the oily solvent is cyclohexane; The mass ratio of the polyvinyl alcohol hot aqueous solution, the soluble platinum salt solution and the oily solvent is 10:0.1 - 0.5:50; the rotation speed of the high-speed shearer is 20,000 revolutions per minute, the pulverization time is 5 minutes, and the temperature is controlled at 20 °C; (2)Preparation of Pickering fine emulsion of nano-platinum: At room temperature, in an operating cabinet protected by nitrogen, the soft-template Pickering inverse fine emulsion containing the water-soluble platinum salt prepared in step (1) is transferred into a device with a heating magnetic stirring device, a quantitative reducing agent is dropped in, and after magnetic stirring, the temperature is gradually increased and kept warm and then cooled to room temperature to complete the preparation of the Pickering inverse fine emulsion of nano-platinum; (3)Preparation of carbon nitride and nano-platinum nano hybrid: At room temperature, the Pickering inverse fine emulsion of nano-platinum prepared in step (2) is transferred to an ultrasonic biological pulverizer for pulverization, and at the same time, a quantitative aqueous solution of a carbon nitride precursor in hot water is dropped into the fine emulsion prepared in step (2) at a fixed rate, and pulverized for a fixed time to complete the loading of the carbon nitride precursor into the Pickering fine emulsion of nano-platinum; at room temperature, the carbon nitride precursor is loaded into the Pickering inverse fine emulsion of nano-platinum and dried on a purified quartz glass by spin coating. After heat treatment of the film, a carbon nitride and nano-platinum hybrid is obtained.

2. The carbon nitride and platinum nanohybrid according to claim 1, characterized in that, In step (1), the temperature of the hot water is 70 - 80 °C, and the mass concentration of the polyvinyl alcohol dissolved in the hot water is 0.5 - 1.0%; the dropping rate of the polymer dissolved in the hot water is 5% of the mass fraction of the polyvinyl alcohol hot aqueous solution per minute; the dropping rate of the aqueous solution of the soluble platinum metal salt is 20% of the mass fraction of the platinum salt aqueous solution per minute.

3. The carbon nitride and nano-platinum hybrid according to claim 1, wherein In step (2), the reducing agent is hydrazine hydrate, sodium borohydride, aqueous formaldehyde solution or aqueous sodium formate solution, the mass concentration of the aqueous formaldehyde solution is 17%, and the mass concentration of the aqueous sodium formate solution is 10%.

4. The carbon nitride and platinum nanohybrid according to claim 1, characterized in that, In step (2), the mass ratio of the reducing agent to the soluble platinum salt solution in step (1) is 1.0 - 1.2:1, the dropping rate of the reducing agent is 20% of the mass fraction of the reducing agent per minute; the magnetic stirring gradually heats up to 60 - 65 °C, and the holding time is 60 - 90 minutes.

5. The carbon nitride and platinum hybrid according to claim 1, characterized in that, In step (3), the carbon nitride precursor is melamine or urea, and the mass concentration of its hot aqueous solution is 2%, and the temperature of the hot aqueous solution is 60-65°C; the mass ratio of the carbon nitride precursor hot aqueous solution to the soluble platinum salt solution in step (1) is 2:1, and the dropping rate is 10% of the mass fraction of the carbon nitride precursor aqueous solution per minute; the high power of the ultrasonic cell disruptor is 500 W and it is crushed at 80% power for 10 minutes.

6. The carbon nitride and platinum nanoparticle hybrid according to claim 1, wherein In step (3), the thickness of the spin-coated film is controlled to be 150-200 microns; the heat treatment method is under reduced pressure nitrogen protection, with a pressure of 500-2000 Pa, a heating rate of 5°C per minute, a holding temperature of 150-200°C, and a heat treatment time of 2-3 hours.

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