Preparation method of periodic macroporous photocatalytic material with porous framework

Abstract

The invention discloses a preparation method of a periodic macroporous photocatalytic material with a porous framework, which comprises the following steps: filling gaps among large-size polymethyl methacrylate (PMMA) small balls with small-size PMMA small balls to serve as a multi-scale ordered PMMA template; the preparation method comprises the following steps: dissolving soluble tantalum / niobium salt in ethanol to obtain a precursor solution, then adding a PMMA template agent to make the precursor solution fully infiltrate template gaps, carrying out suction filtration, placing a sample in a tubular furnace, curing the structure in a nitrogen atmosphere, and finally placing the sample in a muffle furnace for calcination to remove the template. The tantalum pentoxide and niobium pentoxide prepared by the method disclosed by the invention have a periodic macroporous structure with a porous skeleton, the specific surface area and the carrier mobility are greatly improved, and the active sites of the reaction are increased, so that the photocatalytic hydrogen production efficiency is improved; the novel synthesis strategy has a reference value for preparation of the three-dimensional multi-scale porous photocatalytic material, and has a wide application prospect.

Description

Technical Field

[0001] The invention belongs to the field of photocatalytic decomposition of water to produce hydrogen, and specifically relates to a method for preparing a periodic macroporous photocatalytic material with a porous skeleton. Background Art

[0002] With the rapid economic development, energy consumption is increasing. On the one hand, energy is becoming increasingly scarce, and on the other hand, the use of fossil energy has caused serious environmental pollution problems. Developing a clean, low-carbon, safe and efficient new energy system is an effective strategy to cope with global climate deterioration, energy shortages, achieve the "dual carbon plan" and promote social development.

[0003] As a new type of efficient energy carrier, hydrogen energy has high energy density and clean combustion products. Hydrogen energy has attracted widespread attention due to its renewability and environmental friendliness. Photocatalytic technology uses sustainable solar energy to decompose water on the surface of photocatalysts to produce hydrogen. It is a long-term, high-return strategic research topic. However, the performance of today's photocatalysts is still restricted by two major factors: the high carrier recombination rate of semiconductor photocatalysts and the low utilization rate of solar energy.

[0004] Ta 2 O 5 and Nb 2 O 5 As a common photocatalyst, it has good photocatalytic performance and photothermal stability, but its specific surface area is small, and the surface defects in the granular structure reduce the reactive active sites and increase the recombination rate of carriers. In view of this, the present invention is proposed. Summary of the invention

[0005] In view of the shortcomings of the prior art, the present invention aims to provide a method for preparing a periodic macroporous photocatalytic material with a porous skeleton, aiming to solve the problem of ordinary Ta 2 O 5 and Nb 2 O 5 The problems of small specific surface area and high carrier recombination rate are solved, and the photocatalytic reaction efficiency of tantalum oxide and niobium oxide is further improved, which has great advantages in photocatalytic hydrogen production.

[0006] The purpose of the present invention is achieved through the following technical solutions: The present invention provides a method for preparing a periodic macroporous photocatalytic material with a porous skeleton, comprising the following steps: S1, using methyl methacrylate (MMA), potassium persulfate, deionized water, and methanol as raw materials to prepare large-sized PMMA beads, using methyl methacrylate, potassium persulfate, and deionized water as raw materials to prepare small-sized PMMA beads, mixing the two template beads and evaporating them to obtain a multi-scale ordered PMMA template; S2, dissolving a soluble tantalum / niobium salt in ethanol to obtain a precursor solution, adding a PMMA template into the precursor solution to fully wet it, and filtering to obtain sample 1; S3. The obtained sample 1 is heated and solidified, and then calcined to remove the template, thereby obtaining a periodic macroporous photocatalytic material with a porous skeleton.

[0007] Furthermore, the large-sized PMMA spheres described in S1 are obtained by oil bath polymerization of methyl methacrylate, potassium persulfate, deionized water and methanol at 70°C for 4-6 h, and have a diameter of 1-1.8 μm; the small-sized PMMA spheres are obtained by oil bath polymerization of methyl methacrylate, potassium persulfate and deionized water at 70°C for 1-2.5 h, and have a diameter of 150-300 nm.

[0008] Furthermore, the multi-scale ordered PMMA template described in S1 is obtained by mixing large-sized PMMA beads and small-sized PMMA beads, ultrasonically mixing them, and then drying them at 40-60°C.

[0009] Furthermore, the soluble tantalum / niobium salt in S2 is TaCl 5 / NbCl 5 , ethanol and Ta 5+ / Nb 5+ The molar ratio is 1:(0.005-0.04).

[0010] Furthermore, the dosage ratio of PMMA template to precursor solution in S2 is 5 mL / g.

[0011] Furthermore, the heating curing in S3 is heating with nitrogen, the nitrogen flow rate is 40-60 mL / min, the heating rate is 1 °C / min, heating is performed at 300 °C for 3 h, and natural cooling is performed.

[0012] Furthermore, the calcination temperature in S3 is 500-700°C, and the heating rate is 1°C / min.

[0013] The process of the present invention utilizes a multi-scale ordered PMMA template to construct a periodic macroporous structure with a porous skeleton. 2 O 5 and Nb 2 O 5 , significantly increased the specific surface area of ​​the catalyst, increased the active sites of the reaction, shortened the migration distance of the carriers, and reduced the recombination rate of the carriers, thereby increasing the Ta 2 O 5 and Nb 2 O 5This general synthetic strategy can extend the possibility of multi-scale periodic macroporous growth to other functional semiconductor materials.

[0014] The beneficial effects of the present invention are: (1) The present invention adopts a multi-scale ordered PMMA template and prepares a skeleton-porous periodic macroporous tantalum pentoxide and niobium pentoxide by infiltrating the template with a precursor solution. Compared with periodic macroporous materials with larger pore sizes, which have lower specific surface areas that hinder the adsorption of molecules, and macroporous materials with smaller pore sizes that hinder mass transfer and restrict the entry of large molecules into active sites, the skeleton-porous periodic macroporous structure of the present invention introduces smaller pores into larger pores, which not only has a high specific surface area, but also improves the mass transfer efficiency, increases the active sites of the reaction, reduces the recombination rate of carriers, and exhibits excellent photocatalytic ability.

[0015] (2) The multi-scale ordered PMMA template prepared by the present invention, in most cases, the PMMA beads produced by soap-free emulsion polymerization have a final particle size of up to 600 nm due to their micelle mechanism. We simply used soap-free emulsion polymerization in a methanol-rich aqueous medium to prepare PMMA beads with a size of more than 1 μm in one step, ultimately achieving a perfect combination of small-sized macropores and large-sized macropores, so that the photocatalyst can increase the number of reaction active sites through the small-sized macropores and effectively transport the guest substances to the framework active sites through the large-sized macropores.

[0016] (3) The porous skeleton periodic macroporous catalyst constructed by the present invention greatly shortens the carrier migration distance, increases the carriers that migrate to the catalyst surface for reaction, and improves the utilization rate of photogenerated carriers. This porous skeleton periodic macroporous structure has a higher porosity, improves the utilization rate of light, and thus improves the efficiency of the catalyst in decomposing water to produce hydrogen.

[0017] (4) The porous skeleton of the periodic macroporous catalyst constructed by the present invention forms a single crystal structure, which greatly reduces the barrier of carrier migration and improves the carrier mobility, thereby greatly improving the efficiency of photocatalytic water decomposition to produce hydrogen. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 The framework is porous and has periodic macroporous Ta 2 O 5 and Nb 2 O 5 XRD pattern of .

[0019] Figure 2 SEM image of the multi-scale ordered PMMA template.

[0020] Figure 3a in the middle is the periodic macropore Ta with porous framework 2 O 5 SEM images of b and b show the periodic macroporous Nb with porous skeleton. 2 O 5 SEM images of the samples.

[0021] Figure 4 The framework is porous and has periodic macroporous Ta 2 O 5 Pure water hydrogen production performance diagram, and the periodic macroporous Nb with porous skeleton when methanol is used as sacrificial agent 2 O 5 Hydrogen production performance diagram. DETAILED DESCRIPTION

[0022] In order to make the purpose, technical scheme and advantages of the present invention clearer, the technical scheme of the present invention will be clearly and completely described below in conjunction with the embodiments. If the specific conditions are not specified in the embodiments, they are carried out according to the conventional conditions or the conditions recommended by the manufacturer. If the manufacturer of the reagents or instruments is not specified, they are all conventional products that can be purchased commercially.

[0023] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art of the present invention. The terms used in the specification of the present invention are only for the purpose of describing specific embodiments and are not intended to limit the present invention. The term "and / or" used herein includes any and all combinations of one or more related listed items.

[0024] Example 1 1. First, weigh 400 g methanol and 200 g water in advance and add them into a 1 L three-necked round-bottom flask. Stir and heat to 70 °C under nitrogen atmosphere. Add 20 g MMA. Continue stirring for 20 min and then add K 2 S 2 O 8 (0.15 g K 2 S 2 O 8 / 10 mLH 2 O) aqueous solution to initiate the polymerization reaction, and finally keep the temperature constant for 6 h to obtain PMMA beads of 1.1 μm in size. 750 mL of water was placed in a three-necked round-bottom flask, stirred and heated to 70 °C under nitrogen atmosphere, 50 mL of MMA was added, and K was added after continuous stirring for 20 min. 2 S 2 O 8 (0.3 g K 2 S 2 O 8 / 20 mL H 2The polymerization reaction was initiated by aqueous solution of 200 nm O, and the PMMA beads were finally obtained by constant temperature for 1 h. The large and small PMMA beads were mixed and ultrasonically dispersed, and then dried in an oven at 60 ° C to obtain a highly ordered multi-scale PMMA template.

[0025] 2. Take 0.3 g NbCl 5 Dissolve in 10 mL of anhydrous ethanol, stir and dissolve to obtain a precursor solution, add 1.5 g of ordered multi-scale PMMA template after natural filtration, immerse for 12 h, vacuum filter out excess solution, and dry at ambient temperature for 2 h. Then heat at 300 °C in a tube furnace for 3 h at a heating rate of 1 °C / min and a nitrogen flow rate of 50 mL / min, transfer to a muffle furnace after natural cooling, and calcine at 500 °C for 3 h at a heating rate of 1 °C / min to obtain a periodic macroporous Nb with a porous skeleton. 2 O 5 .

[0026] Example 2 1. First, weigh 400 g methanol and 200 g water in advance and add them into a 1 L three-necked round-bottom flask. Stir and heat to 70 °C under nitrogen atmosphere. Add 40 g MMA. Continue stirring for 20 min and then add K 2 S 2 O 8 (0.15 g K 2 S 2 O 8 / 10 mLH 2 O) aqueous solution to initiate the polymerization reaction, and finally keep the temperature constant for 4 h to obtain PMMA beads of 1.5 μm in size. 750 mL of water was placed in a three-necked round-bottom flask, stirred and heated to 70 °C under nitrogen atmosphere, 50 mL of MMA was added, and K was added after continuous stirring for 20 min. 2 S 2 O 8 (0.25 g K 2 S 2 O 8 / 20 mL H 2 The polymerization reaction was initiated by aqueous solution of 200 nm O, and the PMMA beads were finally obtained by constant temperature for 1.5 h. The large and small PMMA beads were mixed and dispersed by ultrasonic, and then dried in an oven at 50 °C to obtain a highly ordered multi-scale PMMA template.

[0027] 2. Take 1 g TaCl 5Dissolve in 10 mL of anhydrous ethanol, stir and dissolve to obtain a precursor solution, add 2 g of ordered multi-scale PMMA templates to it after natural filtration, immerse for 6 hours, vacuum filter out the excess solution, and dry at ambient temperature for 2 hours. Then heat at 300 °C in a tube furnace for 3 hours at a heating rate of 1 °C / min and a nitrogen flow rate of 40 mL / min. After natural cooling, transfer to a muffle furnace and calcine at 700 °C for 3 hours at a heating rate of 1 °C / min to obtain a periodic macroporous Ta with a porous skeleton. 2 O 5 .

[0028] Example 3 1. First, weigh 400 g methanol and 200 g water in advance and add them into a 1 L three-necked round-bottom flask. Stir and heat to 70 °C under nitrogen atmosphere. Add 30 g MMA. Continue stirring for 20 min and then add K 2 S 2 O 8 (0.15 g K 2 S 2 O 8 / 10 mLH 2 O) aqueous solution to initiate the polymerization reaction, and finally keep the temperature constant for 6 h to obtain PMMA beads of 1.7 μm in size. 750 mL of water was placed in a three-necked round-bottom flask, stirred and heated to 70 °C under nitrogen atmosphere, 50 mL of MMA was added, and K was added after continuous stirring for 20 min. 2 S 2 O 8 (0.3 g K 2 S 2 O 8 / 20 mL H 2 The polymerization reaction was initiated by aqueous solution of 2-nitropropene and then kept at constant temperature for 1.5 h to obtain PMMA beads of 250 nm in size. The large and small PMMA beads were mixed and dispersed ultrasonically, and then dried in an oven at 60 °C to obtain a highly ordered multi-scale PMMA template.

[0029] 2. Take 0.3 g NbCl 5 Dissolve in 10 mL of anhydrous ethanol, stir and dissolve to obtain a precursor solution, add 2 g of ordered multi-scale PMMA templates after natural filtration, immerse for 12 h, vacuum filter out excess solution, and dry at ambient temperature for 2 h. Then heat at 300 °C in a tube furnace for 3 h at a heating rate of 1 °C / min and a nitrogen flow rate of 50 mL / min. After natural cooling, transfer to a muffle furnace and calcine at 500 °C for 3 h at a heating rate of 1 °C / min to obtain a periodic macroporous Nb with a porous skeleton. 2 O 5.

[0030] Example 4 1. First, weigh 400 g methanol and 200 g water in advance and add them into a 1 L three-necked round-bottom flask. Stir and heat to 70 °C under nitrogen atmosphere. Add 40 g MMA. Continue stirring for 20 min and then add K 2 S 2 O 8 (0.15 g K 2 S 2 O 8 / 10 mLH 2 O) aqueous solution to initiate the polymerization reaction, and finally keep the temperature constant for 5 h to obtain PMMA beads of 1.7 μm in size. 750 mL of water was placed in a three-necked round-bottom flask, stirred and heated to 70 °C under nitrogen atmosphere, 55 mL of MMA was added, and K was added after continuous stirring for 20 min. 2 S 2 O 8 (0.25 g K 2 S 2 O 8 / 10 mL H 2 The polymerization reaction was initiated by aqueous solution of 200 μg / mL and the PMMA spheres were kept at constant temperature for 2 h to obtain 250 nm PMMA spheres. The large and small PMMA spheres were mixed and dispersed ultrasonically and dried in an oven at 50 °C to obtain a highly ordered multi-scale PMMA template.

[0031] 2. Take 1.2 g TaCl 5 Dissolve in 10 mL of anhydrous ethanol, stir and dissolve to obtain a precursor solution, add 2 g of ordered multi-scale PMMA templates after natural filtration, immerse for 5 h, vacuum filter out excess solution, and dry at ambient temperature for 2 h. Then heat at 300 °C in a tube furnace for 3 h at a heating rate of 1 °C / min and a nitrogen flow rate of 40 mL / min, transfer to a muffle furnace after natural cooling, and calcine at 700 °C for 3 h at a heating rate of 1 °C / min to obtain a skeleton porous periodic macroporous Ta 2 O 5 .

[0032] The products obtained in Examples 1-4 above have the following morphology, structure, and properties: Figure 1-Figure 4 shown.

[0033] Depend on Figure 1 It can be seen that the framework of the porous periodic macroporous Ta prepared by the present invention 2 O 5 and Nb 2 O 5 The photocatalytic materials are all pure phase.

[0034] Depend on Figure 2 It can be seen that the present invention evenly mixes small-sized and large-sized PMMA beads to successfully prepare a highly ordered multi-sized PMMA template.

[0035] Depend on Figure 3 It can be seen that the periodic macroporous Ta 2 O 5 and Nb 2 O 5 was successfully built.

[0036] Depend on Figure 4 It can be seen that the periodic macroporous Ta 2 O 5 and Nb 2 O 5 The hydrogen production performance is excellent.

[0037] The embodiments described above only express several preferred embodiments of the present invention, and the descriptions thereof are relatively specific and detailed, but are not intended to limit the present invention. It should be noted that for those skilled in the art, the present invention may also have various changes and modifications, and any modifications, equivalent substitutions, improvements, etc. made within the concept and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for preparing a periodic macroporous photocatalytic material with a porous skeleton, characterized in that: The steps include: S1, using methyl methacrylate, potassium persulfate, deionized water, and methanol as raw materials to prepare large-sized PMMA beads, using methyl methacrylate, potassium persulfate, and deionized water as raw materials to prepare small-sized PMMA beads, mixing the two template beads and evaporating them to obtain a multi-scale ordered PMMA template; S2, dissolving a soluble tantalum / niobium salt in ethanol to obtain a precursor solution, adding a PMMA template into the precursor solution to fully wet it, and filtering to obtain sample 1; S3. The obtained sample 1 is heated and solidified, and then calcined to remove the template, thereby obtaining a periodic macroporous photocatalytic material with a porous skeleton.

2. The method for preparing a periodic macroporous photocatalytic material with a porous framework according to claim 1, characterized in that: The large-sized PMMA beads S1 are obtained by oil bath polymerization of methyl methacrylate, potassium persulfate, deionized water and methanol at 70°C for 4-6 h, and have a diameter of 1-1.8 μm; the small-sized PMMA beads are obtained by oil bath polymerization of methyl methacrylate, potassium persulfate and deionized water at 70°C for 1-2.5 h, and have a diameter of 150-300 nm.

3. The method for preparing a periodic macroporous photocatalytic material with a porous framework according to claim 1, characterized in that: The multi-scale ordered PMMA template described in S1 is obtained by mixing large-sized PMMA balls and small-sized PMMA balls, ultrasonically mixing them, and then drying them at 40-60°C.

4. The method for preparing a periodic macroporous photocatalytic material with a porous framework according to claim 1, characterized in that: S2 The soluble tantalum / niobium salt is TaCl5 / NbCl5, ethanol and Ta 5+ / Nb 5+ The molar ratio is 1:(0.005-0.04).

5. The method for preparing a periodic macroporous photocatalytic material with a porous framework according to claim 1, characterized in that: The dosage ratio of PMMA template to precursor solution in S2 is 5 mL / g.

6. The method for preparing a periodic macroporous photocatalytic material with a porous framework according to claim 1, characterized in that: The heating curing in S3 is heating with nitrogen, the nitrogen flow rate is 40-60 mL / min, the heating rate is 1 °C / min, heating is performed at 300 °C for 3 h, and natural cooling is performed.

7. The method for preparing a periodic macroporous photocatalytic material with a porous framework according to claim 1, characterized in that: The calcination temperature in S3 is 500-700°C, and the heating rate is 1°C / min.

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