An oxygen-vacancy-containing inorganic-organic hybrid photocatalyst and a preparation method thereof
By preparing an oxygen-vacancy-containing Bi2MoO6-TpPa-1 inorganic-organic hybrid photocatalyst, the problem of low nitrogen solubility in aqueous phase was solved, achieving efficient photocatalytic nitrogen fixation with excellent visible light photocatalytic performance and low cost.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- JIANGNAN UNIV
- Filing Date
- 2023-11-16
- Publication Date
- 2026-06-19
Smart Images
Figure CN117654615B_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of photocatalysis, specifically relating to an oxygen-vacancy-containing inorganic-organic hybrid photocatalyst and its preparation method. Background Technology
[0002] The Haber-Bosch process requires high temperature and pressure conditions, consuming significant amounts of energy and emitting greenhouse gases, making it unsustainable. Researchers have devoted decades to finding a sustainable, green technology for synthesizing NH3. Photocatalytic nitrogen fixation is considered one of the most promising green methods for ammonia synthesis, with the design and construction of highly efficient photocatalysts being crucial. Therefore, developing novel, highly efficient catalysts is essential for reducing N2 to NH3 in aqueous systems. However, nitrogen has low solubility in aqueous solutions, significantly reducing the probability of contact between the catalyst surface and nitrogen molecules. Therefore, designing photocatalytic materials that facilitate nitrogen capture and activation is key to improving the efficiency of photocatalytic nitrogen fixation. Surface defect sites in materials have the function of capturing and activating nitrogen. Due to the presence of defect sites, the surface becomes rich in localized electrons, which can activate inert nitrogen molecules. Therefore, designing and constructing defective photocatalysts is an effective way to modulate the catalytic activity of the catalyst. Summary of the Invention
[0003] To address the above problems, this invention prepares an oxygen-vacancy-containing Bi2MoO6-TpPa-1 inorganic-organic hybrid photocatalyst via a two-step method. This method is simple and inexpensive. The prepared photocatalyst has both good charge separation properties and visible light absorption, and contains oxygen vacancies, which can effectively capture and activate nitrogen molecules, thereby improving the photocatalytic nitrogen fixation efficiency.
[0004] This invention is achieved through the following technical solution:
[0005] The first objective of this invention is to provide a method for preparing an oxygen-vacancy Bi2MoO6-TpPa-1 inorganic-organic hybrid photocatalyst for photocatalytic nitrogen fixation, comprising the following steps:
[0006] (1) Preparation of oxygen-vacancy-containing ultrathin Bi2MoO6 nanosheets: hexadecyltrimethylammonium bromide, sodium molybdate dihydrate and bismuth nitrate pentahydrate were added to an aqueous solution of ethylene glycol, stirred evenly and then transferred to a high-pressure reactor for reaction. The product was washed with water and ethanol and freeze-dried to obtain UBMO.
[0007] (2) Preparation of Bi2MoO6-TpPa-1 hybrid material: Take the UBMO obtained in step (1), o-dichlorobenzene and 1,4-dioxane and mix them evenly. Then add trialdehyde phloroglucinol and p-phenylenediamine and disperse them evenly. Then add acetic acid solution and mix evenly to obtain a mixed solution. Freeze the mixed solution with liquid nitrogen and degas it by freezing-pumping-thawing 3 to 5 times. Then heat the reaction. After the reaction is completed, the product is washed with ethanol, DMF and tetrahydrofuran and freeze-dried to obtain Bi2MoO6-TpPa-1 hybrid material.
[0008] Furthermore, in step (1), the volume ratio of water to ethylene glycol in the aqueous solution of ethylene glycol is 1:(0.5~1.5).
[0009] Furthermore, in step (1), the molar ratio of sodium molybdate dihydrate and bismuth nitrate pentahydrate is 1:(1.5-2.5).
[0010] Furthermore, in step (1), the molar ratio of sodium molybdate dihydrate to hexadecyltrimethylammonium bromide is 1:(1-1.5).
[0011] Furthermore, in step (1), the molar ratio of sodium molybdate dihydrate to the volume ratio of the aqueous solution of ethylene glycol is 0.5 mmol: (30-50) mL.
[0012] Furthermore, in step (1), the reaction in the high-pressure reactor is carried out at 110-150°C for 20-30 hours.
[0013] Furthermore, in step (2), the molar ratio of UBMO to the volume of o-dichlorobenzene is 0.5 mmol:(1-2) mL.
[0014] Furthermore, in step (2), the molar ratio of UBMO to the volume of 1,4-dioxane is 0.5 mmol:(1-2) mL.
[0015] Furthermore, in step (2), the molar ratio of UBMO to trialdehyde phloroglucinol is 1:(0.1 to 0.9).
[0016] Preferably, the molar ratio of UBMO and trialdehyde phloroglucinol in step (2) is 1:(0.3-0.7).
[0017] More preferably, the molar ratio of UBMO and trialdehyde phloroglucinol in step (2) is 1:0.5.
[0018] Furthermore, in step (2), the molar ratio of UBMO to p-phenylenediamine is 1:(0.1 to 0.2).
[0019] Furthermore, in step (2), the concentration of the acetic acid solution is 2-5 M.
[0020] Furthermore, in step (2), the molar ratio of UBMO to the volume of acetic acid solution is 0.5 mmol:(0.5-1) mL.
[0021] Furthermore, the heating reaction described in step (2) is carried out at 110–130°C for 60–80 h.
[0022] A second objective of this invention is to provide an oxygen-vacancy Bi2MoO6-TpPa-1 inorganic-organic hybrid photocatalyst prepared by the aforementioned method.
[0023] A third objective of this invention is to provide the application of the aforementioned oxygen-vacancy-containing Bi2MoO6-TpPa-1 inorganic-organic hybrid photocatalyst in the field of photocatalysis.
[0024] Furthermore, the application in the field of photocatalysis is photocatalytic nitrogen fixation.
[0025] Compared with the prior art, the present invention has the following significant advantages:
[0026] (1) This invention provides a method for preparing an oxygen-vacancy Bi2MoO6-TpPa-1 inorganic-organic hybrid photocatalyst for photocatalytic nitrogen fixation. An oxygen-vacancy Bi2MoO6-TpPa-1 inorganic-organic hybrid composite material was constructed by in-situ synthesis. An effective interface was formed between the two-dimensional materials, which facilitates charge separation and transfer, thereby improving the visible light photocatalytic activity.
[0027] (2) The oxygen-vacancy Bi2MoO6-TpPa-1 inorganic-organic hybrid photocatalyst prepared in this invention has excellent visible light photocatalytic nitrogen fixation performance. It can achieve efficient photocatalytic nitrogen fixation without the need to add any sacrificial agent or co-catalyst, and has potential application value.
[0028] (3) The present invention synthesizes an oxygen-vacancy Bi2MoO6-TpPa-1 inorganic-organic hybrid high-efficiency photocatalyst in two steps. The synthesis method is simple, easy to operate and low in cost. Attached Figure Description
[0029] Figure 1 X-ray diffraction patterns of different samples: (a) TpPa-1 and TpPa / UBMO-3, (b) block samples BBMO, UBMO and composite samples with different composite ratios;
[0030] Figure 2 Scanning electron micrographs of different samples: (a) UBMO, (b) TpPa-1 and (c) TpPa / UBMO-3 composite sample; (d) high-resolution transmission electron micrograph of TpPa / UBMO-3 composite sample;
[0031] Figure 3 Electron paramagnetic resonance spectra of UBMO, TpPa-1, and TpPa / UBMO-3;
[0032] Figure 4 Fluorescence spectra of BBMO, UBMO, TpPa-1 and TpPa / UBMO-3;
[0033] Figure 5 Photocatalytic nitrogen fixation performance of different samples: (a) BBMO, UBMO, TpPa-1, TpPa / UBMO-3 and TpPa / BBMO-3; (b) composite photocatalysts with different proportions in Examples 1 to 5. Detailed Implementation
[0034] The present invention will be further described in detail below with reference to specific embodiments. These descriptions are for explanation purposes only and are not intended to limit the scope of the invention.
[0035] Source of raw materials
[0036] Trialdehyde-based phloroglucinol, analytical grade, Shanghai Maclean Biotechnology Co., Ltd.; p-phenylenediamine, analytical grade, Aladdin Biotechnology Co., Ltd.; all others were analytical grade, Sinopharm Chemical Reagent Co., Ltd.
[0037] Example 1
[0038] A method for preparing an oxygen-vacancy Bi2MoO6-TpPa-1 inorganic-organic hybrid photocatalyst for photocatalytic nitrogen fixation, comprising the following steps:
[0039] (1) Preparation of oxygen-vacancy-containing ultrathin Bi2MoO6 nanosheets: 0.225 g of hexadecyltrimethylammonium bromide (CTAB), 0.5 mmol of sodium molybdate dihydrate (Na2MoO4·2H2O) and 1 mmol of bismuth nitrate pentahydrate (Bi(NO3)3·5H2O) were added to a mixed solution containing 20 mL of deionized water and 20 mL of ethylene glycol. After the mixture was stirred evenly, it was transferred to a high-pressure reactor and reacted in an oven at 120 °C for 24 h. The product was washed several times with deionized water and ethanol. The obtained product was freeze-dried for 12 h and the sample was labeled as UBMO.
[0040] (2) Preparation of Bi2MoO6-TpPa-1 hybrid material: First, 0.05 mmol UBMO was weighed and added to a mixed solution of 1.5 mL o-dichlorobenzene and 1.5 mL 1,4-dioxane, and ultrasonicated until uniformly dispersed; then 0.005 mmol trialdehyde phloroglucinol (Tp) and 0.0075 mmol p-phenylenediamine (Pa) were added and ultrasonically dispersed, and then 0.5 mL 3M acetic acid (HAc) solution was added and mixed evenly; the above mixed solution was transferred to a Pyrex tube, the tube was frozen with liquid nitrogen and degassed by freezing-pumping-thawing 3 times, and then the tube was sealed and heated in an oven at 120℃ for 72 h; the product was washed multiple times with ethanol, DMF and tetrahydrofuran, and then freeze-dried for 12 h to obtain Bi2MoO6-TpPa-1 hybrid material, denoted as TpPa / UBMO-1.
[0041] Example 2
[0042] The preparation method in this embodiment is the same as that in Example 1. The only difference is that in step (2) of this embodiment, 0.015 mmol of trialdehyde phloroglucinol (Tp) and 0.0225 mmol of p-phenylenediamine (Pa) are added respectively. The other conditions remain unchanged. The resulting Bi2MoO6-TpPa-1 hybrid material is denoted as TpPa / UBMO-2.
[0043] Example 3
[0044] The preparation method in this embodiment is the same as that in Example 1. The only difference is that in step (2) of this embodiment, 0.025 mmol of trialdehyde phloroglucinol (Tp) and 0.0375 mmol of p-phenylenediamine (Pa) are added respectively. The other conditions remain unchanged. The resulting Bi2MoO6-TpPa-1 hybrid material is denoted as TpPa / UBMO-3.
[0045] Example 4
[0046] The preparation method in this embodiment is the same as that in Example 1. The only difference is that in step (2) of this embodiment, 0.035 mmol of trialdehyde phloroglucinol (Tp) and 0.0525 mmol of p-phenylenediamine (Pa) are added respectively. The other conditions remain unchanged. The resulting Bi2MoO6-TpPa-1 hybrid material is denoted as TpPa / UBMO-4.
[0047] Example 5
[0048] The preparation method in this embodiment is the same as that in Example 1. The only difference is that in step (2) of this embodiment, 0.045 mmol of trialdehyde phloroglucinol (Tp) and 0.0675 mmol of p-phenylenediamine (Pa) are added respectively. The other conditions remain unchanged. The resulting Bi2MoO6-TpPa-1 hybrid material is denoted as TpPa / UBMO-5.
[0049] Comparative Example 1
[0050] Preparation of bulk Bi₂MoO₆: 5 mmol of bismuth nitrate pentahydrate and 2.5 mmol of sodium molybdate dihydrate were added to 20 mL of deionized water and magnetically stirred for 30 min. The resulting mixture was then transferred to an autoclave and reacted in an oven at 200 °C for 24 h. After cooling the reaction mixture, the product was washed with deionized water and ethanol, and then freeze-dried for 12 h. The resulting bulk Bi₂MoO₆ sample was labeled BBMO.
[0051] Comparative Example 2
[0052] The preparation method in this embodiment is similar to that in Example 3. The only difference is that the UBMO formed in step (1) is not added in this embodiment, but the BBMO prepared in Comparative Example 1 is added. The other conditions remain unchanged, and the prepared sample is denoted as TpPa / BBMO-3.
[0053] Small-angle X-ray diffraction characterization was performed on TpPa-1 and TpPa / UBMO-3, such as... Figure 1 As shown in Figure a, TpPa-1 exhibits strong diffraction peaks at small angles, indicating that the prepared COF has good crystallinity and long-range order. The UBMO composite did not significantly alter the ordered structure of TpPa-1. Furthermore, wide-angle X-ray diffraction was used to analyze the phase structures of UBMO, BBMO, and samples with different composite ratios, as shown in Figure a. Figure 1 As shown in b, the diffraction peak positions of BBMO and UBMO are the same, both corresponding to standard card number 77-1246, indicating that their phase structures are both pure-phase bismuth molybdate. However, the intensity of the diffraction peaks differs between the two; the diffraction peak of the oxygen-vacancy-containing ultrathin UBMO is significantly broadened, indicating the successful preparation of the ultrathin structure. Obvious UBMO diffraction peaks can be seen in composite samples with different proportions, indicating that the in-situ formation of TpPa-1 did not alter the phase structure of UBMO.
[0054] Figure 2 The images show scanning electron microscopy and transmission electron microscopy of the samples before and after composite formation. The images clearly show that pure UBMO has an ultrathin sheet-like structure and TpPa-1 has a linear structure. The composition of both can be clearly seen in the composite sample, indicating the successful preparation of the Bi2MoO6-TpPa-1 hybrid material.
[0055] Figure 3To determine the presence of oxygen vacancies in the material using electron paramagnetic spectroscopy (EPR), the figure clearly shows that the TpPa / UBMO-3 composite and UBMO have strong EPR signals at g = 2.002, while TpPa-1 does not, indicating that both the composite and UBMO contain oxygen vacancies, and that the oxygen vacancies in the composite originate from the UBMO component.
[0056] Figure 4 The fluorescence spectrum of the sample shows that, based on the method of this invention, the fluorescence intensity of the composite photocatalyst sample formed by combining ultrathin UBMO with TpPa-1 decreased significantly, indicating that the introduction of TpPa-1 can effectively reduce the recombination of photogenerated electrons and holes in the composite photocatalyst, thereby improving the photocatalytic nitrogen fixation performance of the photocatalyst.
[0057] Example 6
[0058] To study the photocatalytic performance of the photocatalyst, the prepared photocatalyst was used for photocatalytic nitrogen fixation. The specific experimental procedure is as follows:
[0059] 5 mg of photocatalyst was weighed and dispersed in 30 mL of ultrapure water without adding any sacrificial agent. Nitrogen gas was introduced for 30 min to remove oxygen. During the photocatalysis process, circulating nitrogen gas was continued to maintain a nitrogen-saturated atmosphere in the entire reaction system. The nitrogen fixation yield was tested after 1 h of illumination with a 300 W xenon lamp (with a filter to remove ultraviolet light with wavelengths less than 420 nm).
[0060] The photocatalytic nitrogen fixation performance of composite samples with different proportions in Examples 1-5, BBMO in Comparative Example 1, and TpPa / BBMO-3 in Comparative Example 2 is as follows: Figure 5 As shown, the photocatalytic performance of the composite sample is significantly enhanced. With increasing Tp content, the photocatalytic performance of the composite sample first increases and then decreases, exhibiting an optimal value: when the Tp content is 50% of the molar amount of UBMO, the corresponding TpPa / UBMO-3 composite sample exhibits the best photocatalytic nitrogen fixation performance. When bulk BBMO is used instead of oxygen-vacancy-containing ultrathin UBMO, the photocatalytic nitrogen fixation performance of the prepared TpPa / BBMO-3 is worse than that of the TpPa / UBMO-3 composite sample, indicating that oxygen vacancies have a stronger effect on nitrogen capture and activation, thereby improving the photocatalytic nitrogen fixation performance.
[0061] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application and are not intended to limit it. Although this application has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of this application without departing from the spirit and scope of the technical solutions of this application, and all such modifications or substitutions should be covered within the scope of the claims of this application.
Claims
1. A method for preparing an oxygen-vacancy-containing Bi2MoO6-TpPa-1 inorganic-organic hybrid photocatalyst, characterized in that, Includes the following steps: (1) Preparation of oxygen-vacancy-containing ultrathin Bi2MoO6 nanosheets: Hexadecyltrimethylammonium bromide, sodium molybdate dihydrate and bismuth nitrate pentahydrate were added to an aqueous solution of ethylene glycol, stirred evenly, and then transferred to a high-pressure reactor for reaction. The product was washed with water and ethanol and freeze-dried to obtain UBMO. The molar ratio of sodium molybdate dihydrate to bismuth nitrate pentahydrate was 1:1.5~2.5; the molar ratio of sodium molybdate dihydrate to hexadecyltrimethylammonium bromide was 1:1~1.
5. (2) Preparation of Bi2MoO6-TpPa-1 hybrid material: Take the UBMO obtained in step (1), o-dichlorobenzene and 1,4-dioxane and mix them evenly. Then add trialdehyde phloroglucinol and p-phenylenediamine and disperse them evenly. Then add acetic acid solution and mix evenly to obtain a mixed solution. Freeze the mixed solution with liquid nitrogen and degas it by freezing-pumping-thawing 3 to 5 times. Then heat the reaction. After the reaction is completed, wash the product with ethanol, DMF and tetrahydrofuran and freeze dry to obtain Bi2MoO6-TpPa-1 hybrid material. The molar ratio of UBMO and trialdehyde phloroglucinol is 1:0.
5. The molar ratio of UBMO and p-phenylenediamine is 1:0.1~0.
2.
2. The method of claim 1, wherein, In step (1), the volume ratio of water to ethylene glycol in the aqueous solution of ethylene glycol is 1:0.5~1.
5.
3. The method as claimed in claim 1, characterized in that In step (1), the molar ratio of sodium molybdate dihydrate to the volume ratio of the aqueous solution of ethylene glycol is 0.5 mmol: 30~50 mL.
4. The method as claimed in claim 1, characterized in that In step (2), the molar ratio of UBMO to the volume of o-dichlorobenzene is 0.5 mmol: 1~2 mL; the molar ratio of UBMO to the volume of 1,4-dioxane is 0.5 mmol: 1~2 mL.
5. The method as claimed in claim 1, wherein, In step (2), the concentration of the acetic acid solution is 2~5 M; the molar ratio of UBMO to the volume of the acetic acid solution is 0.5 mmol:0.5~1 mL.
6. The oxygen-vacancy Bi2MoO6-TpPa-1 inorganic-organic hybrid photocatalyst prepared by the method according to any one of claims 1 to 5.
7. The application of the oxygen-vacancy-containing Bi2MoO6-TpPa-1 inorganic-organic hybrid photocatalyst as described in claim 6 in the field of photocatalysis.