CN111331149A - Method for preparing hollow Pt nanospheres by taking spherical calcium carbonate as template - Google Patents

Abstract

The invention discloses a method for preparing hollow Pt nanospheres by using spherical calcium carbonate as a template. The method first adopts an inverse microemulsion method to prepare spherical calcium carbonate with a particle size of 0.5-1 μm, and then uses the spherical calcium carbonate as a template, Using potassium chloroplatinite as platinum source and ascorbic acid as reducing agent, hollow Pt nanospheres with regular morphology, uniform size and narrow distribution of particle size of 1-2 μm are simply and efficiently prepared. The preparation method of the invention is simple, safe and non-toxic, and has low cost; the obtained hollow Pt nanospheres exhibit high catalytic activity and stability for methanol catalytic oxidation reaction under acidic conditions, and have good application prospects in electrochemistry .

Description

A method for preparing hollow Pt nanospheres with spherical calcium carbonate as a template

technical field

The invention belongs to the technical field of catalyst preparation, and in particular relates to a method for preparing hollow Pt nanospheres by using spherical calcium carbonate as a template. stability.

Background technique

Precious metals such as platinum, silver, rhodium, palladium, ruthenium, etc., have many advantages, such as high temperature resistance, corrosion resistance, oxidation resistance, etc., and their catalytic activity is high, and they are extremely important catalyst materials. Due to their unique structural characteristics, nano-hollow precious metal spheres have the characteristics of low density, large specific surface area, high surface activity, and strong surface permeability, so they have important applications in the fields of chemistry, biology and materials science.

At present, the preparation methods of hollow sphere materials mainly include spray drying method, emulsion method and template synthesis method, and template method is the most widely used and important method for preparing hollow spheres. Template method is an important method for synthesizing hollow nanomaterials, which is mainly divided into hard template method and soft template method. Significant advantages in shell thickness, particle size and dispersibility. For example: Hyeon et al. reported in 2008 the preparation of iron oxide nanocapsules using SiO ₂ as a template (Piao Y, Kim J, Na HB, et al. Wrap–bake–peel process for nanostructural transformation from β-FeOOH nanorods to biocompatible iron oxide nanocapsules [ J].Nature Materials, 2008, 7(3): 242-247.), Wu et al. reported the synthesis of hollow SiO ₂ spheres by a simple method using polystyrene as a template (Deng, Ziwei, Chen, Min, Zhou , Shuxue, et al. A Novel Method for the Fabrication of Monodisperse Hollow Silica Spheres [J]. Langmuir the Acs Journal of Surfaces&Colloids, 22(14): 6403-6407.), Long et al. used the oxygen generated by the decomposition of hydrogen peroxide as a template to synthesize Hollow TiO ₂ spheres (Long L, Zhang H, Ye M, et al. Ammonia cation-assisted bubble template for synthesizing hollow TiO ₂ nanospheres and their application in lithium ionstorage [J]. RSC Advances, 2015, 5.), Zoldesi et al. reported a direct emulsion as a template to prepare hollow SiO ₂ microspheres and capsule microspheres (CIZoldesi, Imhof A. Synthesis of Monodisperse Colloidal Spheres, Capsules, and Microballoons by Emulsion Templating [J]. Advanced Materials, 2005, 17(7) :924-928.), Zheng et al. used anionic vesicles as soft templates to prepare hollow SeCd spheres (Zheng X, Xie Y, Zhu L, et al.Formation of vesicle-templated CdSe hollow spheres in an ultrasound-induced anionic surfactant solution[J].Ultrasoni csSonochemistry, 2002, 9(6): 311-316.) Dong et al. developed a sequence template method to prepare ZnO multishell structures (Dong Z, Lai X, Halpert JE, et al. Accurate Control of Multishelled ZnO HollowMicrospheres for Dye-Sensitized Solar Cells with High Efficiency[J].AdvancedMaterials,2012,24(8):1046-1049.) Kang Yongqiang et al (Kang Yong-Qiang,Xue Qi,Zhao Yue,etal.Selective Etching Induced Synthesis of Hollow Rh NanospheresElectrocatalyst for Alcohol Oxidation Reactions [J].Small:1801239.) Using rhodium trichloride and chloroauric acid as raw materials, a rhodium-gold core-shell structure is formed, and the gold core is removed by aqua regia to form hollow rhodium. This method has high cost and high toxicity of aqua regia, The experimental risk factor is high. Therefore, it has become a hot and difficult point in the field of hollow materials to provide a simple, effective, low-cost, non-toxic preparation method for hollow nanomaterials.

SUMMARY OF THE INVENTION

Aiming at the problems of agglomeration, large size of template agent and harsh removal conditions affecting the target product in the current hard template method, the present invention is based on a narrow distribution, monodisperse and easy-to-remove spherical calcium carbonate template. The calcium carbonate template dissolves and reduces the product Pt in advance, and finally provides a simple and effective method for preparing hollow Pt nanospheres by using spherical calcium carbonate with a particle size of 0.5-1 μm prepared by an inverse microemulsion method as a template.

For the above purpose, the technical scheme adopted in the present invention is made up of the following steps:

1. Preparation of spherical calcium carbonate template

The calcium chloride solid is dissolved in deionized water, polyacrylic acid is added, and after stirring evenly, sodium dodecylbenzenesulfonate is added to obtain a calcium source solution with a calcium ion concentration of 0.5 to 3.5 mol/L; The source solution was added to the mixed solution of cyclohexane, compound surfactant and co-surfactant, mixed evenly, allowed to stand, and the supernatant was taken to obtain an inverse microemulsion. The total volume of the inverse microemulsion was 100. %, in which calcium source solution accounts for 1.0%-7.0%, compound surfactant accounts for 0.5%-1.5%, co-surfactant accounts for 0.5%-2%, and the rest is cyclohexane; Ammonia water was added dropwise to adjust the pH to 8-10, then CO ₂ gas was continuously introduced, reacted at 25-28°C for 0.5-1.5 hours, centrifuged and washed to obtain submicron spherical calcium carbonate with a porous surface.

2. Preparation of hollow Pt nanospheres

The spherical calcium carbonate obtained in step 1 is ultrasonically dispersed in a 1.3-1.6 mol/L ascorbic acid aqueous solution with a pH of 7-10, then left to stand for 2-4 hours in a vacuum state, and the supernatant is quickly poured out, and the solution is placed at 60- Add 0.01-0.03 mol/L potassium chloroplatinite aqueous solution with a pH of 8-12 to the lower precipitation under stirring at 70°C, stir and react for 1.5-2 hours, centrifuge, wash, and then add dilute hydrochloric acid to remove calcium carbonate to obtain Hollow Pt nanospheres.

In the above-mentioned step 1, the calcium ion concentration in the obtained calcium source solution is preferably 1.0～3.0mol/L, the concentration of polyacrylic acid is 0.16～0.24g/L, and the concentration of sodium dodecylbenzenesulfonate is 0.02～0.03mol/L. L, wherein the polyacrylic acid has a number-average molecular weight of 5,000.

In the above step 1, based on the total volume of the inverse microemulsion as 100%, preferably the calcium source solution accounts for 2.0% to 5.0%, the compound surfactant accounts for 0.7% to 1.0%, and the cosurfactant accounts for 1.5% to 1.5%. 2.0%, and the rest is cyclohexane.

The above-mentioned compound surfactant is a mixture of polyoxyethylene castor oil and Span-80 in a mass ratio of 55:45 to 65:35, and the co-surfactant is ethanol.

In the above-mentioned step 2, preferably the spherical calcium carbonate obtained in step 1 is ultrasonically dispersed in a 1.3-1.6 mol/L ascorbic acid aqueous solution with a pH of 7.5-8.5, then left standstill for 2-4 hours in a vacuum state, and the upper layer is quickly poured out. In the clear night, add 0.01-0.03 mol/L potassium chloroplatinite aqueous solution with a pH of 10-12 to the lower layer precipitate under stirring at 60-70 °C, and stir for 1.5-2 hours.

The pH of the above-mentioned ascorbic acid aqueous solution and potassium chloroplatinite aqueous solution was adjusted by NaOH.

In the above step 2, it is further preferred that the mass-volume ratio of the spherical calcium carbonate to the potassium chloroplatinite aqueous solution is 1 g: (200-500) mL.

The beneficial effects of the present invention are as follows:

In the present invention, an inverse microemulsion method is used to prepare submicron spherical calcium carbonate with a particle size of 0.5-1 μm, porosity and high specific surface area, and then the spherical calcium carbonate is used as a template, and potassium chloroplatinite is used as a platinum source. Ascorbic acid is a reducing agent, using the characteristics of the porous structure of spherical calcium carbonate, the ascorbic acid is infiltrated into the spherical calcium carbonate by means of vacuuming, and when the ascorbic _acid is stably stored in the calcium carbonate, it is taken out. The potassium chloroplatinite aqueous solution was quickly added to reduce it on the surface of spherical calcium carbonate to form a core-shell structure, and finally the calcium carbonate was removed by acid dissolution to form hollow Pt nanospheres.

The preparation method of the invention is simple, safe and non-toxic, and has low cost. The prepared hollow Pt nano-spheres have regular appearance, uniform size and narrow particle size distribution (1-2 μm), and exhibit excellent performance in the catalytic oxidation reaction of methanol under acidic conditions. It has high catalytic activity and stability, and has good application prospects in electrochemistry.

Description of drawings

1 is a scanning electron microscope photograph of the submicron spherical calcium carbonate obtained in Example 1.

FIG. 2 is an XRD pattern of the hollow Pt nanospheres obtained in Example 1. FIG.

3 is a scanning electron microscope photograph of the hollow Pt nanospheres obtained in Example 1.

FIG. 4 is a partial enlarged view of FIG. 3 .

5 is a field emission transmission electron microscope photograph of the hollow Pt nanospheres obtained in Example 1.

6 is a scanning electron microscope photograph of the hollow Pt nanospheres obtained in Example 2.

FIG. 7 is a scanning electron microscope photograph of the hollow Pt nanospheres obtained in Example 3. FIG.

Detailed ways

The present invention will be further described in detail below with reference to the accompanying drawings and embodiments, but the protection scope of the present invention is not limited to these embodiments.

Example 1

1. Preparation of spherical calcium carbonate template

Dissolve 1.11 g of calcium chloride solid with a purity of more than 99% in 8 mL of deionized water, add 2 mL of 1.0 g/L polyacrylic acid aqueous solution with a number average molecular weight of 5000, stir for 0.5 hours, and then add 0.0871 g to it Sodium dodecylbenzenesulfonate, stir evenly to obtain calcium source solution, wherein the calcium ion concentration is 1.0mol/L, the concentration of polyacrylic acid is 0.2g/L, and the concentration of sodium dodecylbenzenesulfonate is 0.025mol/L L. Mix 0.6 g of polyoxyethylene castor oil and 0.4 g of sban-80 uniformly, add 1.0 mL of ethanol to it, and after mixing uniformly, add the resulting mixture dropwise to 100 mL of cyclohexane under stirring at room temperature, and then add it to the mixture. 5 mL of calcium source solution was added dropwise, stirred evenly, and allowed to stand for 2 hours, and the supernatant was taken to obtain an inverse microemulsion. Add ammonia water dropwise to the inverse microemulsion, adjust the pH value to 9.4, then continuously pass _CO gas into the inverse microemulsion, let stand for 40 minutes at 25°C, centrifuge, wash with ethanol 3 times, wash with water 1 time, and finally vacuum-dried at 70 °C to obtain submicron spherical calcium carbonate. It can be seen from Figure 1 that the obtained calcium carbonate is spherical, regular in shape, uniform in size, and narrow in particle size distribution. The particle size is about 500 nm. .

2. Preparation of hollow Pt nanospheres

0.02 g of spherical calcium carbonate obtained in step 1 was ultrasonically dispersed in 5 mL of a 1.5 mol/L ascorbic acid aqueous solution with a pH of 8.84 (pH was adjusted with NaOH), uniformly dispersed and placed in a vacuum drying box, and then placed under vacuum to 0.8 MPa. For 3 hours, quickly take out and pour out the supernatant, and put it into a 65°C water bath and add 6 mL of 0.025 mol/L potassium chloroplatinite aqueous solution (pH adjusted with NaOH) to the lower precipitate under stirring state, at 2 Potassium chloroplatinite was rapidly reduced to elemental Pt on the surface of calcium carbonate within ~3 minutes. After stirring for 1.5 hours, centrifugation and washing were performed, and then dilute hydrochloric acid was added to dissolve in acid for 2 hours to remove calcium carbonate. Finally, hollow Pt nanoparticles were obtained after centrifugation and washing. ball. It can be seen from Figure 2 that the obtained product is indeed elemental Pt, and it can be clearly seen from Figures 3 to 5 that the obtained metal Pt has a hollow structure with a particle size of about 1 μm.

Example 2

In this example, 0.02 g of spherical calcium carbonate obtained in step 1 was ultrasonically dispersed in 5 mL of a 1.5 mol/L ascorbic acid aqueous solution with a pH of 7.9 (pH was adjusted with NaOH), and the dispersion was uniformly placed in a vacuum drying box. After reaching 0.8MPa, it was left for 2 hours. The other steps are the same as in Example 1 to obtain hollow Pt nanospheres with a particle size of about 1 μm (see FIG. 6 ).

Example 3

In this example, 0.02 g of spherical calcium carbonate obtained in step 1 was ultrasonically dispersed in 5 mL of a 1.5 mol/L ascorbic acid aqueous solution with a pH of 8.84 (pH was adjusted with NaOH), and the dispersion was uniformly placed in a vacuum drying oven. After reaching 0.8MPa, place it for 3 hours, quickly take out and pour out the supernatant, and put it into a 70 ° C water bath and add 6 mL of a 0.025 mol/L potassium chloroplatinite aqueous solution with a pH of 11.5 to the lower precipitation under stirring. adjustment), potassium chloroplatinite was rapidly reduced to elemental Pt on the surface of calcium carbonate within 2 to 3 minutes, and stirred for 1.5 hours. Other steps are the same as in Example 1, and hollow Pt spheres are obtained, the particle size of which is about 1 μm (see FIG. 7 ).

Example 4

In this example, 3.33 g of calcium chloride solid with a purity of more than 99% was dissolved in 8 mL of deionized water, and 2 mL of 1.0 g/L polyacrylic acid aqueous solution with a number-average molecular weight of 5,000 was added to it, and after stirring evenly, it was added to the 0.0871g of sodium dodecylbenzenesulfonate was added therein, and stirred uniformly to obtain a calcium source solution, wherein the calcium ion concentration was 3.0mol/L, the concentration of polyacrylic acid was 0.2g/L, and the concentration of sodium dodecylbenzenesulfonate was 0.2g/L. is 0.025mol/L. Other steps are the same as in Example 1, and hollow Pt nanospheres are obtained.

Claims (8)

1. a method for preparing hollow Pt nanospheres with spherical calcium carbonate as a template, is characterized in that it is made up of the following steps: (1) Preparation of spherical calcium carbonate template The calcium chloride solid is dissolved in deionized water, polyacrylic acid is added, and after stirring evenly, sodium dodecylbenzenesulfonate is added to obtain a calcium source solution with a calcium ion concentration of 0.5 to 3.5 mol/L; The source solution was added to the mixed solution of cyclohexane, compound surfactant and co-surfactant, mixed evenly, allowed to stand, and the supernatant was taken to obtain an inverse microemulsion. The total volume of the inverse microemulsion was 100. %, in which calcium source solution accounts for 1.0%-7.0%, compound surfactant accounts for 0.5%-1.5%, co-surfactant accounts for 0.5%-2.0%, and the rest is cyclohexane; Ammonia water is added dropwise to adjust the pH value to 8-10, then _CO gas is continuously introduced, reacted at 25-28°C for 0.5-1.5 hours, centrifuged and washed to obtain submicron spherical calcium carbonate with a porous surface; (2) Preparation of hollow Pt nanospheres The spherical calcium carbonate obtained in step (1) is ultrasonically dispersed in a 1.3-1.6 mol/L ascorbic acid aqueous solution with a pH of 7-10, and then left to stand for 2-4 hours in a vacuum state, and the supernatant is quickly poured out. Add 0.01-0.03 mol/L potassium chloroplatinite aqueous solution with a pH of 8-12 to the lower sediment under stirring at 60-70 °C, stir and react for 1.5-2 hours, centrifuge, wash, and then add dilute hydrochloric acid to remove calcium carbonate , to obtain hollow Pt nanospheres. 2. The method for preparing hollow Pt nanospheres according to claim 1, characterized in that: in step (1), the calcium ion concentration in the obtained calcium source solution is 1.0～3.0mol/L, and the concentration of polyacrylic acid is 0.16～3.0 mol/L. 0.24g/L, the concentration of sodium dodecylbenzenesulfonate is 0.02-0.03mol/L, wherein the number average molecular weight of the polyacrylic acid is 5000. 3. The method for preparing hollow Pt nanospheres according to claim 1, wherein in step (1), the total volume of the inverse microemulsion is 100%, wherein the calcium source solution accounts for 2.0%～5.0% , Compound surfactant accounts for 0.7%-1.0%, co-surfactant accounts for 1.5%-2.0%, and the rest is cyclohexane. 4. the method for preparing hollow Pt nanospheres according to claim 1 and 3, is characterized in that: described compound surfactant is polyoxyethylene castor oil and span-80 mass ratio is 55:45～65 :35 mixture. 5. The method for preparing hollow Pt nanospheres according to claim 1 or 3, wherein the co-surfactant is ethanol. 6. The method for preparing hollow Pt nanospheres according to claim 1, wherein in step (2), the spherical calcium carbonate obtained in step (1) is ultrasonically dispersed in a pH of 7.5-8.5 at 1.3-1.6 mol/L ascorbic acid aqueous solution, then stand for 2 to 4 hours in a vacuum state, quickly pour out the supernatant, and add 0.01 to 0.03 mol/L of pH 10 to 12 to the lower precipitation under stirring at 60 to 70 °C. L potassium chloroplatinite aqueous solution, and the reaction was stirred for 1.5 to 2 hours. 7. The method for preparing hollow Pt nanospheres according to claim 1 or 6, wherein in step (2), the pH of the ascorbic acid aqueous solution and the potassium chloroplatinite aqueous solution is adjusted by NaOH. 8. the method for preparing hollow Pt nanospheres according to claim 1 or 6, is characterized in that: in step (2), the mass volume ratio of described spherical calcium carbonate and potassium chloroplatinite aqueous solution is 1g:(200 ~500) mL.

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