Preparation method of hollow carbon sphere epitaxial growth Bi4O5Br2 nanosheet confinement reactor and CO2 hydrogenation application of hollow carbon sphere epitaxial growth Bi4O5Br2 nanosheet confinement reactor

Abstract

The invention belongs to the field of design and synthesis of nano confinement reactors and CO2 hydrogenation application, and relates to a preparation method of a hollow carbon sphere epitaxial growth Bi4O5Br2 nanosheet confinement reactor and photocatalytic CO2 hydrogenation application of the hollow carbon sphere epitaxial growth Bi4O5Br2 nanosheet confinement reactor. A hollow nitrogen-doped carbon sphere NC is used as a template, and Bi4O5Br2 nanosheets grow in situ on the surface of the hollow nitrogen-doped carbon sphere NC through an oil bath method to construct a supported hollow carbon sphere confinement reactor BOB (at) NC. And photo-induced electrons generated by the Bi4O5Br2 nanosheets are directionally migrated into the hollow carbon spheres (NC) under the action of a built-in electric field and a Bi-C bond. Wherein the N site in the NC can be used as an electron enrichment center and a CO2 spontaneous adsorption-activation center at the same time, so that the CO2 activation energy barrier is effectively reduced, and the hydrogenation reduction reaction is promoted. Under simulated sunlight irradiation, the yields of CO and CH4 generated by reducing CO2 through BOB and NC are 3.31 times and 14.91 times of those of a monomer BOB respectively. The work provides a new thought for constructing a high-performance artificial photosynthesis catalyst.

Description

Technical Field

[0001] The invention belongs to the field of nano-confined reactor material preparation and artificial photosynthesis technology, and particularly relates to a hollow carbon sphere epitaxial growth Bi 4 O 5 Br 2 Preparation method of nanosheet confined reactor and its photocatalytic CO 2 Reduction hydrogenation applications. Background Art

[0002] Driven by clean solar energy, it simulates plant photosynthesis and converts greenhouse gas CO 2 Converting CO into carbon-based fuels is a cutting-edge technology to alleviate the current energy crisis and environmental pollution. 2 It is an extremely stable linear molecule with a C=O binding energy of 750 kJ mol -1 At the same time, the photocatalyst has low efficiency in separating photogenerated charge carriers and CO 2 Poor adsorption-activation-hydrogenation active sites lead to CO 2 Therefore, a novel method combining effective directional separation of photogenerated charge carriers and abundant CO 2 Photocatalysts with activation and reduction sites are the key to further development of artificial photosynthesis technology. Summary of the invention

[0003] The purpose of this invention is to controllably construct a hollow BOB@NC nanoconfined reactor to achieve effective light absorption while improving the directional migration and separation efficiency of photogenerated electrons, and to enhance CO 2 adsorption-activation ability, thus achieving high-performance photocatalytic CO 2 Reduction and hydrogenation to carbon-based fuels can alleviate the fossil energy crisis.

[0004] This patent uses the template method to controllably construct hollow carbon spheres to epitaxially grow Bi 4 O 5 Br 2 Nanosheet (BOB@NC) confined reactor. Ultrathin BOB nanosheets grow uniformly and upright on the outer surface of NC. The photogenerated electrons of BOB nanosheets converge from the surface to the edge under photoexcitation, and the edge electrons migrate to the NC surface through Bi-C bonds. The photogenerated electrons on NC quickly undergo the process of eh exciton state generation and transfer to defect states, thereby effectively separating the photogenerated electrons of BOB. NC acts as a photogenerated electron enrichment center, while transferring the abundant CO 2 Molecules are trapped in the cavity. Under simulated sunlight, BOB@NC reduces CO 2 Produces CO and CH 4The yields of BOB@NC and BOB@NC were 3.31 and 14.91 times of those of BOB, respectively. The construction of BOB@NC nanoconfined reactor has opened up a new way to design efficient artificial photosynthesis catalysts.

[0005] The technical solution of the present invention:

[0006] A hollow carbon sphere epitaxial growth Bi 4 O 5 Br 2 The preparation method of the nanosheet confined reactor comprises the following steps:

[0007] (1) adding hollow nitrogen-doped carbon spheres and urotropine to a mannitol aqueous solution to prepare a solution A;

[0008] (2) dissolving bismuth nitrate, bismuth acetate, bismuth sulfate or bismuth ammonium citrate bismuth salt in mannitol solution to prepare solution B;

[0009] (3) adding an inorganic or organic bromine salt to the mannitol solution to prepare solution C;

[0010] (4) Adding solution B in step (2) and solution C in step (3) to solution A in step (1) in sequence, stirring to obtain a mixed solution D.

[0011] (5) After transferring the solution D in step (4) to an oil bath and heating for several hours, the obtained product was centrifuged, washed several times with distilled water and anhydrous ethanol, and dried to obtain Bi 4 O 5 Br 2 Nanosheet-loaded hollow carbon sphere confined reactor material, i.e., hollow carbon sphere epitaxial growth Bi 4 O 5 Br 2 Nanosheet confined reactor, denoted as BOB@NC.

[0012] In step (1), the dosage ratio of the hollow nitrogen-doped carbon spheres, urotropine and the mannitol aqueous solution is 5-20 mg: 0.5-3 mmol: 10-150 mL, wherein the concentration of the mannitol aqueous solution is 0.2-2.0 mmol / L.

[0013] In step (2), the dosage ratio of bismuth salt to mannitol aqueous solution is 0.2-4mmol:10-150mL, wherein the concentration of mannitol aqueous solution is 0.2-2.0mmol / L.

[0014] In step (3), the dosage ratio of the bromide salt to the mannitol aqueous solution is 0.2-4mmol:10-150mL, wherein the concentration of the mannitol aqueous solution is 0.2-2.0mmol / L.

[0015] In step (3), the inorganic bromine salt is KBr, NaBr or NH 4 One of Br.

[0016] In step (3), the organic bromide salt is one of hexadecyltrimethylammonium bromide, 1,3-dimethylimidazolium bromide, 1-ethyl-3-methylimidazolium bromide, 1-propyl-3-methylimidazolium bromide iodide, 1-butyl-3-methylimidazolium bromide iodide or 1-dodecyl-3-methylimidazolium bromide.

[0017] In step (4), the ratio of the raw materials in solutions A, B and C is 5-20 mg: 0.2-4 mmol: 0.2-4 mmol for the hollow nitrogen-doped carbon spheres, bismuth salt and bromide salt.

[0018] In step (5), the reaction temperature is 60-120°C, the reaction time is 1-24h, the drying temperature is 40-80°C, and the drying time is 4-12h.

[0019] The hollow carbon sphere epitaxial growth Bi 4 O 5 Br 2 The diameter of the nanosheet confined reactor is 100-1000nm.

[0020] Hollow carbon spheres prepared by the present invention are epitaxially grown Bi 4 O 5 Br 2 Nanosheet confined reactor for photocatalytic CO 2 Reduction and hydrogenation to produce CO and CH 4 .

[0021] The beneficial effects of the present invention are:

[0022] The present invention uses hollow nitrogen-doped carbon balls (NC) as templates to epitaxially grow Bi 4 O 5 Br 2 (BOB) ultrathin nanosheets are used to construct hollow confined reactors (BOB@NC). BOB@NC improves the utilization rate of light absorption and promotes the migration of photogenerated electrons from BOB to the NC surface through built-in electric fields and Bi-C bonds. Photogenerated electrons undergo rapid eh exciton state generation and transfer to defect states on the NC surface, achieving directional migration and effective separation of photogenerated electrons. The doped nitrogen in NC acts as an enrichment center for photogenerated electrons and CO 2 The active sites of adsorption-activation-hydrogenation effectively reduce the energy barrier of the rate-determining step of the reaction and spontaneously induce the hydrogenation of the *CO intermediate until CH 4 The construction of the BOB@NC nanoconfinement reactor opens up a new avenue for the design of highly efficient artificial photosynthesis catalysts. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 Epitaxial growth of Bi on prepared hollow carbon spheres 4 O 5 Br 2 XRD pattern of nanosheet confined reactor material.

[0024] Figure 2 SEM and TEM images of the prepared BOB@NC-0.3 material.

[0025] Figure 3 SEM and TEM images of the prepared BOB@NC-0.1 material.

[0026] Figure 4 SEM and TEM images of the prepared BOB@NC-0.5 material.

[0027] Figure 5 The prepared Bi 4 O 5 Br 2 TEM image of nanosheets.

[0028] Figure 6 Solid UV image of the prepared BOB@NC-0.3.

[0029] Figure 7 Epitaxial growth of Bi 4 O 5 Br 2 Nanosheet confined reactor materials for photocatalytic reduction of CO 2 Production of CO and CH 4 The yield. DETAILED DESCRIPTION

[0030] The present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0031] Embodiment 1:

[0032] Epitaxial growth of Bi on hollow carbon spheres 4 O 5 Br 2 The preparation method of the nanosheet confined reactor comprises the following steps:

[0033] First, 9 mL of ammonia water, 16.5 mL of water, and 4.5 mL of tetraethoxysilane were mixed in 70 mL of ethanol, stirred for 2 hours, and centrifuged. The mixture was washed with deionized water and ethanol and dried to obtain SiO 2 Then, 0.5g SiO 2The nanospheres were dispersed in a pH 8.5 tris(hydroxymethyl)aminomethane buffer solution, stirred for 22 h, centrifuged, washed with deionized water and ethanol, and dried. 2 Heat to 800 °C for 2 h under protection, and then calcine the calcined product with 4 M NH 4 HF 2 Etching for 24h to remove SiO 2 template to obtain hollow nitrogen-doped carbon spheres (NCs).

[0034] Solution A was prepared by adding 10 mg of hollow nitrogen-doped carbon spheres, 1.5 mmol of hexamethylenetetramine and 20 mL of mannitol solution (0.1 M) into a 100 mL round-bottom flask and stirring for 15 min.

[0035] 0.3 mmol Bi(NO 3 ) 3 ·5H 2 O was dissolved in 10 mL of mannitol solution (0.1 M) to prepare solution B.

[0036] Solution C was prepared by dissolving 0.3 mmol KBr in 10 mL mannitol solution (0.1 M).

[0037] First, solution B was added dropwise to solution A and stirred for 15 min, then solution C was added and stirred for 30 min, and the mixture was placed in a 90°C oil bath for 6 h. The product was separated, washed, and dried to obtain the nanoconfined reactor BOB@NC-0.3.

[0038] Embodiment 2:

[0039] The preparation method of BOB@NC-0.1 material comprises the following steps:

[0040] Solution A was prepared by adding 10 mg of hollow nitrogen-doped carbon spheres, 1.5 mmol of hexamethylenetetramine and 20 mL of mannitol solution (0.1 M) into a 100 mL round-bottom flask and stirring for 15 min.

[0041] Add 0.1mmol Bi(NO 3 ) 3 ·5H 2 O was dissolved in 10 ml of mannitol solution (0.1 M) to prepare solution B.

[0042] Solution C was prepared by dissolving 0.1 mmol KBr in 10 mL of mannitol solution (0.1 M).

[0043] First, solution B was added dropwise to solution A and stirred for 15 min, then solution C was added and stirred for 30 min, and the mixture was placed in a 90°C oil bath for 6 h. The product was separated, washed, and dried to obtain the nanoconfined reactor BOB@NC-0.1.

[0044] Embodiment 3:

[0045] The preparation method of BOB@NC-0.5 material comprises the following steps:

[0046] Solution A was prepared by adding 10 mg of hollow nitrogen-doped carbon spheres, 1.5 mmol of hexamethylenetetramine and 20 mL of mannitol solution (0.1 M) into a 100 mL round-bottom flask and stirring for 15 min.

[0047] Add 0.5mmol Bi(NO 3 ) 3 ·5H 2 O was dissolved in 10 ml of mannitol solution (0.1 M) to prepare solution B.

[0048] Solution C was prepared by dissolving 0.5 mmol KBr in 10 mL of mannitol solution (0.1 M).

[0049] First, solution B was added dropwise to solution A and stirred for 15 min, then solution C was added and stirred for 30 min, and the mixture was placed in a 90°C oil bath for 6 h. The product was separated, washed, and dried to obtain the nanoconfined reactor BOB@NC-0.5.

[0050] Comparative Example 1:

[0051] Bi 4 O 5 Br 2 The method for preparing the nanosheet comprises the following steps:

[0052] Solution A was prepared by adding 1.5 mmol of hexamethylenetetramine and 20 mL of mannitol solution (0.1 M) into a 100 mL round-bottom flask and stirring for 15 min.

[0053] Add 0.5mmol Bi(NO 3 ) 3 ·5H 2 O was dissolved in 10 mL of mannitol solution (0.1 M) to prepare solution B.

[0054] Solution C was prepared by dissolving 0.5 mmol KBr in 10 mL of mannitol solution (0.1 M).

[0055] First, solution B was added dropwise to solution A and stirred for 15 min, then solution C was added and stirred for 30 min, and the mixture was placed in a 90°C oil bath for 6 h. The product was separated, washed, and dried to obtain Bi 4 O 5 Br 2 Nanosheets, denoted as BOB.

[0056] Figure 1 The nanoconfined reactors BOB@NC-0.3, BOB@NC-0.1, BOB@NC-0.5 prepared in Examples 1-3 of the present invention and the Bi prepared in Comparative Example 1 4 O 5 Br 2 XRD pattern of nanosheets. It can be found that the XRD diffraction peaks of the prepared materials are all Bi 4 O 5 Br 2 characteristic peaks.

[0057] Figure 2 The SEM and TEM images of the BOB@NC-0.3 material prepared in Example 1 of the present invention are shown in Figure 1. 4 O 5 Br 2 The nanosheets grow vertically and uniformly on the surface of hollow nitrogen-doped carbon spheres.

[0058] Figure 3 The SEM and TEM images of the BOB@NC-0.1 material prepared in Example 2 of the present invention are shown in Figure 2. A small amount of Bi 4 O 5 Br 2 The nanosheets grow vertically on the surface of hollow nitrogen-doped carbon spheres.

[0059] Figure 4 The SEM and TEM images of the BOB@NC-0.5 material prepared in Example 3 of the present invention are shown in Figure 3. 4 O 5 Br 2 The nanosheets grow randomly on the surface of hollow nitrogen-doped carbon spheres.

[0060] Figure 5 Bi prepared in Comparative Example 1 of the present invention 4 O 5 Br 2 TEM image of nanosheets. It can be found that Bi 4 O 5 Br 2 Nanosheets are ultra-thin sheet-like structures.

[0061] Figure 6The nanoconfined reactor BOB@NC-0.3 and Bi prepared in Example 1 and Comparative Example 1 of the present invention 4 O 5 Br 2 Solid UV image of nanosheets. It can be found that Bi 4 O 5 Br 2 The light absorption edge of the nanosheet is 550nm, while the light absorption edge of the BOB@NC-0.3 nanoconfined reactor can be broadened to the near-infrared light.

[0062] Figure 7 The nanoconfined reactors BOB@NC-0.3, BOB@NC-0.1, BOB@NC-0.5 prepared in Examples 1-3 of the present invention and Bi prepared in Comparative Example 1 4 O 5 Br 2 Photocatalytic reduction of CO by BOB nanosheets 2 Hydrogenation to produce CO and CH 4 The yield diagram shows that the nanoconfined reactor BOB@NC-0.3 produces CO and CH 4 The yield was the highest. After 5 h of illumination, BOB@NC-0.3 reduced CO 2 The generated CO and CH 4 The yields were 28.34 and 3.13 μmol h -1 g -1 , which are 3.31 and 14.91 times of the monomer BOB respectively.

Claims

1. A method for preparing a confined reactor for epitaxial growth of Bi4O5Br2 nanosheets with hollow carbon spheres, characterized in that: The following steps are involved: (1) adding hollow nitrogen-doped carbon spheres and urotropine to a mannitol aqueous solution to prepare a solution A; (2) using bismuth nitrate, bismuth acetate, bismuth sulfate or ammonium bismuth citrate as a bismuth source and mannitol aqueous solution as a solvent to prepare solution B; (3) using an inorganic bromine salt and an organic bromine salt as halogen sources and a mannitol aqueous solution as solvent to prepare a solution C; (4) injecting the solution B in step (2) and the solution C in step (3) into the solution A in step (1) in sequence, and stirring to obtain a mixed solution D; (5) After transferring solution D in step (4) to an oil bath and heating for reaction for several hours, the obtained product is centrifuged, washed several times with distilled water and anhydrous ethanol, and vacuum dried to obtain a Bi4O5Br2 nanosheet-loaded hollow carbon sphere confined reactor material, i.e., a hollow carbon sphere epitaxially grown Bi4O5Br2 nanosheet confined reactor.

2. The preparation method according to claim 1, characterized in that: In the step (1), the dosage ratio of the hollow nitrogen-doped carbon spheres, urotropine and the mannitol aqueous solution is 5-20 mg: 0.5-3mmol:10-150mL, wherein the concentration of the mannitol aqueous solution is 0.2-2.0mmol / L.

3. The preparation method according to claim 1, characterized in that: In the step (2), the dosage ratio of the bismuth salt to the mannitol aqueous solution is 0.2-4 mmol:10-150 mL, wherein the concentration of the mannitol aqueous solution is 0.2-2.0 mmol / L.

4. The preparation method according to claim 1, characterized in that: In the step (3), the inorganic bromine salt is one of KBr, NaBr or NH4Br.

5. The preparation method according to claim 1, characterized in that: In the step (3), the organic bromide salt is one of hexadecyltrimethylammonium bromide, 1,3-dimethylimidazolium bromide, 1-ethyl-3-methylimidazolium bromide, 1-propyl-3-methylimidazolium bromide iodide, 1-butyl-3-methylimidazolium bromide iodide or 1-dodecyl-3-methylimidazolium bromide.

6. The preparation method according to claim 1, characterized in that: In the step (3), the dosage ratio of the bromide salt to the mannitol aqueous solution is 0.2-4 mmol:10-150 mL, wherein the concentration of the mannitol aqueous solution is 0.2-2.0 mmol / L.

7. The preparation method according to claim 1, characterized in that: In the step (4), the ratio of the raw materials in solutions A, B and C is 5-20 mg of the hollow nitrogen-doped carbon spheres, bismuth salt and bromine salt: 0.2-4mmol:0.2-4mmol.

8. The preparation method according to claim 1, characterized in that: In the step (5), the reaction temperature is 60-120° C., and the reaction time is 1-24 h; the drying temperature is 40-80° C., and the drying time is 4-12 h.

9. A confined reactor for epitaxial growth of Bi4O5Br2 nanosheets on hollow carbon spheres, characterized in that: It is prepared by the preparation method described in any one of claims 1 to 8, and the diameter of the prepared hollow carbon sphere epitaxial growth Bi4O5Br2 nanosheet confined reactor is 100-1000nm.

10. Use of the hollow carbon sphere epitaxially grown Bi4O5Br2 nanosheet confined reactor as described in claim 9 for photocatalytic reduction of CO2 to generate CO and CH4.

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