Preparation method of disc-shaped photocatalytic nitrogen fixation material with Fe-W18O49 morphology regulated and controlled by WO3

Abstract

According to the preparation method of the photocatalytic nitrogen fixation material for regulating and controlling the Fe-W18O49 morphology through the disc-shaped WO3, small-size nanowires Fe-W18O49 can be evenly attached to the surface of the disc-shaped WO3 formed by stacking micro-ribbons, the phenomena that the nanowires are prone to gathering and surface active sites are insufficient are effectively improved, the heterojunction WO3 / Fe-W18O49 interface is tightly connected, and therefore the photocatalytic nitrogen fixation material has the advantages that the photocatalytic nitrogen fixation material is stable in performance, good in stability and good in stability. The Fe-W18O49 prepared by the method can promote rapid separation and transition of photon-generated carriers, reduce the recombination probability of electrons and holes and improve the effective utilization rate of the carriers in a nitrogen fixation reaction, the ammonia generation rate of the photocatalyst synthesized by regulating and controlling the Fe-W18O49 morphology through disc-shaped WO3 is 153.8 micromoles / g <-1 > h <-1 >, the NH3 yield can still reach 132.7 micromoles / g <-1 > h <-1 > after five times of circulation, and the photocatalyst has good photocatalytic stability and can be widely applied to the field of nitrogen fixation. The ammonia generation rate of WO3 / Fe-W18O49 induced and synthesized by rod-like WO3 is only 113.6 [mu] mol g <-1 > h <-1 >, and a feasible strategy for improving the catalytic performance of the Fe-W18O49 by constructing a heterojunction catalyst to regulate and control the morphology of the Fe-W18O49 is provided.

Description

Technical Field

[0001] The present invention belongs to the field of photocatalysis, and particularly relates to a preparation method of a photocatalytic nitrogen fixation material for regulating the morphology of disk-shaped WO 3 regulated Fe-W 18 O 49 . Background Art

[0002] Ammonia (NH 3 ) plays a crucial role in the development of human society and is applied to the synthesis of nitrogen fertilizers, the manufacture of plastics and refrigerants, etc. The synthesis of NH 3 mainly relies on the Haber-Bosch process, in which N 2 and H 2 react under high temperature, high pressure and the action of a catalyst. The whole synthesis process involves multiple reaction steps and complex operating conditions. Compared with traditional processes, photocatalytic ammonia synthesis does not rely on fossil fuels and uses the inexhaustible and renewable green energy solar energy as the driving force of the reaction, promising to achieve zero carbon emissions in the whole process of green ammonia synthesis, realizing the transformation of the energy structure and the "dual carbon" goal. However, photocatalytic nitrogen fixation still faces many challenges, resulting in its inability to be widely applied. The main reasons are: N≡N has an extremely high bond energy and is difficult to be activated by conventional catalysts; the recombination rate of electrons and holes is fast, resulting in low effective utilization rate of carriers. These complex factors need to be considered in the design of photocatalysts.

[0003] In natural photosynthesis, a series of complex dynamic structures within the protein framework can ensure the synthesis of high-value products. Although it is difficult for artificial photosynthesis to replicate such structures, defect engineering can provide the chemical complexity and adjustability required for artificial systems. W 18 O 49 is a powerful candidate for constructing lattice defects. The defect energy band of W 18 O 49 can serve as a storage reservoir for photo-generated electrons, thus reducing the adverse carrier recombination effect. At the same time, surface defects make the metal center in an unsaturated coordination state, providing a suitable position for the chemical adsorption of molecules and establishing an effective channel for electron interaction. Element doping can further optimize the photocatalytic performance of W 18 O 49 : (1) Adjust the electronic structure of the catalyst to promote carrier separation; (2) Change the energy band structure to affect the light absorption response range; (3) The doped element can serve as an active site to provide new properties. For example, Patent CN116603518A discloses a preparation method of a Ce-doped W 18 O 49 photocatalyst. The substitution of low-valence Ce ions for high-valence W ions makes W 18 O 49More oxygen vacancies are generated, which is beneficial to the adsorption of reactants. However, carriers are still prone to recombination, resulting in low H 2 production; in Patent CN113318751A, a sea urchin-like Fe-doped W 18 O 49 was prepared, but the sea urchin-like structure formed by the aggregation of nanowires severely limits the exposure of the surface active sites of W 18 O 49 and the nitrogen fixation activity is affected; Patent CN115069262A discloses a synthesis method of a MoO 3-x / Fe-W 18 O 49 catalyst, in which Fe-W 18 O 49 nanowires are uniformly distributed on the surface of MoO 3-x However, the large size of the nanowires is still the main reason affecting the ammonia production rate. In the prior art, photocatalysts with W 18 O 49 as the main body of nitrogen fixation still face the bottleneck of easy aggregation or large size of nanowires, which inhibits the number of surface active sites of the catalyst or the rapid migration of carriers. The influence of morphological regulation and modification of Fe-W 18 O 49 is not considered in the preparation of the catalyst.

[0004] Therefore, a reasonable catalyst synthesis route is designed to promote the exposure of oxygen vacancies in Fe-W 18 O 49 to the outer surface of the catalyst, and at the same time generate free electrons with strong reducing ability.

[0005] The information disclosed in this background art section is intended to enhance the understanding of the overall background of the present invention and should not be regarded as an admission or any form of suggestion that this information constitutes prior art already known to those of ordinary skill in the art. Summary of the Invention

[0006] As described above, the aggregation of nanowires, the large size of nanowires and the recombination of carriers in Fe-W 18 O 49 are the main obstacles affecting the improvement of its catalytic activity. By constructing a heterojunction catalyst with close interfacial contact with a semiconductor whose energy band structure matches, the directional migration of photo-generated carriers can be accelerated, and at the same time, the morphology of Fe-W 18 O 49 can be regulated. WO 3 is a semiconductor material with potential applications in photocatalysis. Continuously exposed to sunlight, WO 3 still exhibits excellent corrosion resistance and chemical stability. Some studies have shown that W 18 O 49Nanowires can grow on the WO 3 surface to form a heterojunction catalyst, which has a low interfacial impedance, high conductivity, and the synergistic effect of fast carrier migration and abundant active sites, improving the photocatalytic performance under full-spectrum irradiation. However, W 18 O 49 tends to aggregate and cannot be evenly dispersed on the surface of rod-shaped WO 3 . To flexibly adjust the microstructure of WO 3 / W 18 O 49 , it is necessary to reasonably change the synthesis conditions.

[0007] Therefore, this project provides a preparation method of a photocatalytic nitrogen fixation material for regulating the morphology of disk-shaped WO 3 Fe-W 18 O 49 . By using disk-shaped WO 3 to modify Fe-W 18 O 49 , the microstructure of Fe-W 18 O 49 nanowires is optimized, and the photocatalytic nitrogen fixation performance of Fe-W 18 O 49 is improved. The synthesis process of this catalyst is simple and the conditions are easy to control.

[0008] To achieve the above objectives, the present invention adopts the following technical solutions:

[0009] A preparation method of a photocatalytic nitrogen fixation material for regulating the morphology of disk-shaped WO 3 Fe-W 18 O 49 . The photocatalyst is constructed by disk-shaped WO 3 and Fe-W 18 O 49 nanowires. Under solvothermal synthesis conditions, Fe-W 18 O 49 can be evenly attached to the surface of disk-shaped WO 3 .

[0010] On the other hand, the present invention provides a preparation method of a photocatalytic nitrogen fixation material for regulating the morphology of disk-shaped WO 3 Fe-W 18 O 49 . The detailed synthesis scheme is as follows:

[0011] (1) Prepare disk-shaped WO 3 using sodium tungstate and sodium chloride in an acidic solution;

[0012] (2) Add the disk-shaped WO synthesized in step one to the alcohol solution of tungsten chloride and iron chloride.3 , the heterojunction catalyst WO is prepared by a solvothermal method 3 / Fe-W 18 O 49 .

[0013] In some embodiments, as described in step (1), for the synthesis of disk-shaped WO 3 , 0.1 g of sodium tungstate and 0.3 g of sodium chloride are added to 30 mL of deionized water, stirred for 1 h to form a clear solution, hydrochloric acid is added to the solution to adjust the pH and stirring is continued for 1 h, and the resulting solution is transferred to a high-pressure reactor and heated at 180 °C for 24 h to obtain disk-shaped WO 3 .

[0014] In some embodiments, as described in step (2), disk-shaped WO is added to 70 mL of absolute ethanol containing 0.1 g of tungsten chloride and 0.01 g of iron chloride 3 , the suspension after stirring for 30 min is transferred to a high-pressure reactor, heated in an oven, washed and collected after cooling to obtain WO 3 / Fe-W 18 O 49 heterojunction catalyst.

[0015] In some embodiments, in step (2), the mass of the disk-shaped WO synthesized in step one added is 0.05, 0.10, and 0.15 g, and preferably the mass of the disk-shaped WO synthesized in step one added is 0.10 g. 3 3 .

[0016] In some embodiments, in step (1), undiluted concentrated hydrochloric acid is added to the solution to adjust the pH value to 1-3, and preferably concentrated hydrochloric acid is added to adjust the pH value to 2.

[0017] In some embodiments, in step (2), the heterojunction catalyst WO is collected by high-speed centrifugation 3 / Fe-W 18 O 49 , the centrifuge is centrifuged at a speed of 10000-12000 rpm for 5-10 min, and the bottom precipitate is collected.

[0018] In some embodiments, in step (2), the high-pressure reactor is maintained in an oven at 180-220 °C for 20 h, and the heating rate of the reactor is 1-3 °C min -1 , and preferably the high-pressure reactor is maintained in an oven at 200 °C for 20 h.

[0019] In some embodiments, in step (1), the stirring speed is 900-1100 rpm both before and after.

[0020] ​In some embodiments, in step (2), the stirring speed is 1000 - 1200 rpm.

[0021] In some embodiments, in step (2), WO is washed with absolute ethanol 3 / Fe-W 18 O 49 4 - 6 times to remove possible impurity ions on the surface of the catalyst.

[0022] In some embodiments, in step (1), by adjusting the feeding relationship of the raw materials, rod-shaped WO can be synthesized. 3 , 1 g of sodium tungstate and 0.3 g of sodium chloride are added to 30 mL of deionized water, stirred for 1 h to form a clear solution, hydrochloric acid is added to the solution to adjust the pH to 2 and stirred for another 1 h, and the resulting solution is transferred to a high-pressure reactor and heated at 180 °C for 24 h to obtain rod-shaped WO. 3 .

[0023] In some embodiments, in step (2), rod-shaped WO can also be added to an alcoholic solution of tungsten chloride and iron chloride, and a heterojunction catalyst WO 3 is prepared by a solvothermal method. 3 / Fe-W 18 O 49 .

[0024] In the third aspect of the present invention, the application of disk-shaped WO 3 in regulating the Fe-W 18 O 49 morphology to synthesize a heterojunction photocatalytic material WO 3 / Fe-W 18 O 49 in nitrogen fixation performance is provided.

[0025] In some embodiments, the application of disk-shaped WO 3 in regulating the Fe-W 18 O 49 morphology to synthesize a heterojunction photocatalytic material WO 3 / Fe-W 18 O 49 in nitrogen fixation performance is characterized in that the heterojunction catalyst WO 3 / Fe-W 18 O 49 is dissolved in pure water, without adding any sacrificial reagent, nitrogen with a purity of 99.999% is bubbled into the solution, and the nitrogen fixation performance is explored under full-spectrum irradiation.

[0026] In some embodiments, disk-shaped WO 3 in regulating the Fe-W 18 O 49 morphology to synthesize a heterojunction photocatalytic material WO3 / Fe-W 18 O 49 The mass ratio to pure water is (1 - 10):10000;

[0027] In some embodiments, the bubbling rate of nitrogen with a purity of 99.999% is 50 mL / min;

[0028] In some embodiments, a 300 W xenon lamp is used to simulate full-spectrum radiation.

[0029] The beneficial effects of the present invention are as follows:

[0030] 1. In this paper, a heterojunction catalyst WO 3 / Fe-W 18 O 49 was synthesized by the hydrothermal method and the solvothermal method. By adjusting the feeding ratio of sodium tungstate to sodium chloride, a disk-shaped WO 3 stacked by micron bands was prepared. Further changing the ratio of disk-shaped WO 3 and Fe-W 18 O 49 in the complex, the microstructure of WO 3 / Fe-W 18 O 49 was regulated, so that small-sized Fe-W 18 O 49 nanowires were uniformly attached to the surface of the disk-shaped WO 3 . The synthesis process of this catalyst is simple, the conditions are easy to control, and it can be prepared repeatedly.

[0031] 2. The present invention provides a preparation method of a photocatalytic nitrogen fixation material for regulating the morphology of disk-shaped WO 3 and Fe-W 18 O 49 . The results of photoelectric performance characterization show that the heterojunction catalyst WO 3 / Fe-W 18 O 49 can effectively reduce the recombination of photo-generated carriers. In the nitrogen fixation activity test, no sacrificial reagent was added to the catalytic solution, and the ammonia generation rate under full-spectrum radiation was 153.8 μmol g -1 h -1 , which is 16.4 and 2.1 times the ammonia synthesis rates of disk-shaped WO 3 and Fe-W 18 O 49 . The ammonia generation rate of the same ratio of WO 3 / Fe-W 3 induced by rod-shaped WO 18 O 49 was only 113.6 μmol g -1 h-1 , reasonable regulation of the micro-morphology and rapid migration of carriers are the keys to promoting the improvement of the catalytic performance of WO 3 / Fe-W 18 O 49 . BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 Scanning electron microscope images of the prepared samples: (a) disc-shaped WO 3 of Comparative Example 1, (b) rod-shaped WO 3 of Comparative Example 2, (c) disc-shaped WO 3 photocatalyst with regulated Fe-W 18 O 49 morphology synthesized in Example 1, (d) rod-shaped WO 3 photocatalyst with regulated Fe-W 18 O 49 morphology synthesized in Example 8;

[0033] Figure 2 are the X-ray diffraction patterns of the disc-shaped WO 3 photocatalyst with regulated Fe-W 18 O 49 morphology synthesized in Examples 1-3;

[0034] Figure 3 is the photoluminescence spectrum of the disc-shaped WO 3 photocatalyst with regulated Fe-W 18 O 49 morphology synthesized in Example 1, the rod-shaped WO 3 photocatalyst with regulated Fe-W 18 O 49 morphology synthesized in Example 8, and the disc-shaped WO 3 of Comparative Example 1;

[0035] Figure 4 are the photocurrent spectra of the disc-shaped WO 3 photocatalyst with regulated Fe-W 18 O 49 morphology synthesized in Examples 1-3 and the disc-shaped WO 3 of Comparative Example 1;

[0036] Figure 5 is the cyclic test of the nitrogen fixation performance of the disc-shaped WO 3 photocatalyst with regulated Fe-W 18 O 49 morphology synthesized in Example 1. DETAILED DESCRIPTION OF THE INVENTION

[0037] Combined with the attached drawings, the operation process of the specific implementation manner will be elaborated in detail below through the technical solution of the present invention. However, it should be understood that the protection scope of the present invention is not limited by the following implementation manner.

[0038] Reagents and characterization instruments used in the examples:

[0039] Sodium chloride, sodium tungstate, ferric chloride, and tungsten chloride were purchased from Aladdin Reagent Co., Ltd. Concentrated hydrochloric acid and absolute ethanol were purchased from Sinopharm Chemical Reagent Co., Ltd. All reagents were not subjected to any purification treatment before use.

[0040] The composition of the samples was detected using an X-ray diffractometer (XRD), and the instrument model was Siemens D5005. The microscopic morphology of the prepared samples was observed using a scanning electron microscope (SEM), and its model was Hitachi SU-8000 FE-SEM. The carrier separation in the samples could be characterized using photocurrent and photoluminescence spectra (PL), and the instruments used were a three-electrode CHI661D electrochemical workstation and an F-7000 fluorescence spectrophotometer, respectively. The nitrogen fixation activity of the samples was detected by ultraviolet-visible diffuse reflectance spectroscopy (model: Varian Cary 700 spectrophotometer).

[0041] Example 1

[0042] WO 3 Regulating Fe-W 18 O 49 Preparation method of a photocatalytic nitrogen fixation material with regulated Fe-W morphology synthesis. The specific synthesis method is as follows:

[0043] (1) The synthesis of disk-shaped WO 3 was carried out by adding 0.1 g of sodium tungstate and 0.3 g of sodium chloride to 30 mL of deionized water, stirring for 1 h to form a clear solution with a stirring speed of 1000 rpm. Concentrated hydrochloric acid was added to the solution to adjust the pH value to 2 and stirring was continued for 1 h with the same stirring speed of 1000 rpm. The resulting solution was transferred to a high-pressure reaction kettle and heated at 180 °C for 24 h to obtain disk-shaped WO 3 .

[0044] (2) 0.10 g of disk-shaped WO 3 was added to 70 mL of absolute ethanol containing 0.1 g of tungsten chloride and 0.01 g of ferric chloride. The suspension after stirring at 1100 rpm for 30 min was transferred to a high-pressure reaction kettle and heated in an oven, maintained at 200 °C for 20 h with a heating rate of 2 °C / min. After cooling, it was washed 5 times with absolute ethanol, and centrifuged at 11000 rpm for 7 min using a centrifuge to collect the bottom precipitate, the heterojunction catalyst WO 3 / Fe-W 18 O 49 .

[0045] Example 2

[0046] WO 3 Preparation method of photocatalytic nitrogen fixation material with regulated Fe-W 18 O 49 morphology is as follows:

[0047] Same as Example 1, except that in step (2), the addition amount of disk-shaped WO 3 is 0.05 g.

[0048] Example 3

[0049] WO 3 Preparation method of photocatalytic nitrogen fixation material with regulated Fe-W 18 O 49 morphology is as follows:

[0050] Same as Example 1, except that in step (2), the addition amount of disk-shaped WO 3 is 0.15 g.

[0051] Example 4

[0052] WO 3 Preparation method of photocatalytic nitrogen fixation material with regulated Fe-W 18 O 49 morphology is as follows:

[0053] Same as Example 1, except that in step (1), concentrated hydrochloric acid is added to adjust the pH value to 1.

[0054] Example 5

[0055] WO 3 Preparation method of photocatalytic nitrogen fixation material with regulated Fe-W 18 O 49 morphology is as follows:

[0056] Same as Example 1, except that in step (1), concentrated hydrochloric acid is added to adjust the pH value to 3.

[0057] Example 6

[0058] WO 3 Preparation method of photocatalytic nitrogen fixation material with regulated Fe-W 18 O 49 morphology is as follows:

[0059] Same as Example 1, except that in step (2), it is heated in an oven and kept at 180 °C for 20 h.

[0060] Example 7

[0061] WO 3 Method for preparing photocatalytic nitrogen fixation material with regulated Fe-W 18 O 49 morphology, and the specific synthesis method is as follows:

[0062] Same as Example 1, except that in step (2), it is heated in an oven and maintained at 220 °C for 20 h.

[0063] Example 8

[0064] WO 3 Method for preparing photocatalytic nitrogen fixation material with regulated Fe-W 18 O 49 morphology, and the specific synthesis method is as follows:

[0065] Same as Example 1, except that in step (2), 0.10 g of rod-shaped WO 3 is added to 70 mL of absolute ethanol containing 0.1 g of tungsten chloride and 0.01 g of iron chloride, and the heterojunction catalyst WO 3 / Fe-W 18 O 49 is prepared by the solvothermal method.

[0066] Preparation of single-phase catalyst disc-shaped WO 3 in Comparative Example 1

[0067] According to the synthesis method of step (1) in Example 1, the single-phase catalyst disc-shaped WO 3 is synthesized.

[0068] Preparation of single-phase catalyst disc-shaped WO 3 in Comparative Example 2

[0069] According to the synthesis method of step (1) in Example 1, by adjusting the feeding relationship of raw materials, rod-shaped WO 3 can be synthesized. 1 g of sodium tungstate and 0.3 g of sodium chloride are added to 30 mL of deionized water, stirred for 1 h to form a clear solution, and hydrochloric acid is added to the solution to adjust the pH to 2.

[0070] Preparation of single-phase catalyst W 18 O 49 in Comparative Example 3

[0071] According to the synthesis method of step (2) in Example 1, only 0.1 g of tungsten chloride is added to 70 mL of absolute ethanol to synthesize the single-phase catalyst W 18 O 49 。

[0072] Preparation of single-phase catalyst Fe-W 18 O 49 in Comparative Example 4

[0073] According to the synthesis method in step (2) of Example 1, 0.1 g of tungsten chloride and 0.01 g of iron chloride were added to 70 mL of absolute ethanol to synthesize the single-phase catalyst Fe-W 18 O 49 .

[0074] Verification example

[0075] 1. Scanning electron microscope characterization

[0076] The microscopic morphology and structural characteristics of the prepared samples were observed by scanning electron microscope, and the test results are as Figure 1 shown. In Figure a, the disk-shaped WO 3 is a structure formed by the stacking of microbelts. In Figure b, the length of the rod-shaped WO 3 is 1-2 μm. The WO 3 induced to synthesize WO 3 / Fe-W 18 O 49 In the heterojunction, Fe-W 18 O 49 still tends to appear in the form of aggregates (Figure d). In comparison, Fe-W 3 nanowires are evenly dispersed on the surface of the disk-shaped WO 18 O 49 (Figure c), and there is close contact between the interfaces. The size of the Fe-W 18 O 49 nanowires is significantly reduced, which can expose more oxygen vacancies to the outer surface of the catalyst to participate in the photocatalytic reaction.

[0077] 2. X-ray diffraction test

[0078] For the photocatalysts synthesized by regulating the morphology of Fe-W 3 in Examples 1-3, the crystal composition was analyzed by X-ray diffraction test, as 18 O 49 shown. In the test spectrum of WO Figure 2 / Fe-W 3 / Fe-W 18 O 49 , the signal peaks related to WO 3 are clearly visible, indicating that the crystallinity of WO 3 is relatively high, and at the same time, it indirectly shows that there are defect structures in the synthesized Fe-W 18 O 49 .

[0079] 3. Photoluminescence test

[0080] Figure 3 is the disk-shaped WO 3Regulating Fe-W 18 O 49 Photocatalyst synthesized by regulating the morphology, Example 8 rod-shaped WO 3 Regulating Fe-W 18 O 49 Photocatalyst synthesized by regulating the morphology and Comparative Example 1 disk-shaped WO 3 Photoluminescence spectra. The signal peak intensity of Comparative Example 1 is significantly higher than that of Examples 1 and 8. The formation of the heterojunction catalyst promotes the rapid separation and transport of photo-generated carriers. The peak intensity of Example 1 decreases more significantly. The defect structure inside Fe-W 18 O 49 can serve as an electron trapping center. The size structure of its nanowires decreases, and the defect structure outside increases, further promoting the separation of photo-generated carriers. Therefore, the PL signal peak intensity of Example 1 decreases significantly.

[0081] 4. Photocurrent test

[0082] Figure 4 Photocurrent spectra of the disk-shaped WO 3 Regulating Fe-W 18 O 49 photocatalyst synthesized by regulating the morphology and Comparative Example 1 disk-shaped WO 3 . The photocurrent test is another method to evaluate the ability of the catalyst to generate carriers under light radiation conditions. In multiple cyclic tests, the degree of recombination of photo-generated carriers in Comparative Example 1 increases, resulting in a gradual decrease in the photocurrent density, while the photocurrent density of Examples 1-3 only shows a weak downward trend, and the photocurrent density generated by Example 1 is the strongest.

[0083] 5. Nitrogen fixation performance cyclic test

[0084] Figure 5 Nitrogen fixation performance cyclic test of the disk-shaped WO 3 photocatalyst synthesized by regulating Fe-W 18 O 49 morphology. During several cyclic processes, it is observed that the ammonia production rate gradually decreases. In the first three tests, there are large numerical differences in the ammonia generation rate. The difference in the ammonia generation rate is the smallest in the 4th and 5th cyclic tests. After 5 cycles, the NH 3 yield can still reach 132.7 μmol g -1 h -1 . Example 1 has good photocatalytic stability.

[0085] 6. Photocatalytic nitrogen fixation reaction

[0086] The photocatalytic performance of Examples 1-7 and Comparative Examples 1-4 was tested to characterize their nitrogen fixation performance. The specific steps are as follows:

[0087] Add 0.05 g of photocatalyst and 100 mL of pure water into the photocatalytic nitrogen fixation reaction device. Bubble nitrogen with a purity of 99.999% into the reaction device in the dark state. After 30 min, conduct the nitrogen fixation performance test under the condition of a 300 W xenon lamp simulation light source, and the light intensity is 200 mW·cm -2 , Take an appropriate amount of turbid liquid from the catalytic reaction device, remove the catalyst and detect the ammonia content in the solution.

[0088] Transfer the solution after removing the catalyst to a cuvette, and use a UV-visible spectrophotometer to detect the photocatalytic nitrogen fixation performance of photocatalysts of Examples 1-7 and Comparative Examples 1-4. The ammonia generation rates of each sample are shown in Table 1.

[0089] Table 1 Nitrogen fixation performance of photocatalysts in different examples / comparative examples

[0090]

[0091]

[0092] In the present invention, the ammonia generation rates of Comparative Example 1 and Comparative Example 2 are 9.4 μmol·g -1 ·h -1 and 7.5 μmol·g -1 ·h -1 , Both are tungsten-based oxides. The ammonia generation rate of Comparative Example 3 increases because its structure contains oxygen vacancies, which can serve as active sites in the photocatalytic nitrogen fixation reaction. In Comparative Example 4, Fe element doping can create more active sites on the surface of W 18 O 49 . The radius and electronegativity of Fe element are different from those of W atoms, resulting in lattice distortion and increasing the possibility of O detaching from the lattice. The constructed heterojunction catalyst WO 3 / Fe-W 18 O 49 has a positive effect on the nitrogen fixation activity. There is a carrier migration phenomenon at the tightly connected heterojunction interface, which can effectively promote the rapid separation and transition of photo-generated carriers, reduce the recombination probability of electrons and holes, and improve the effective utilization rate of carriers in the nitrogen fixation reaction.

[0093] Comparing Examples 1-3, it is not difficult to find that the proportional relationship between WO 3 and Fe-W 18 O 49 in the heterojunction catalyst is one of the key factors affecting the nitrogen fixation performance. In Comparative Example 2, the content of nanowire Fe-W 18 O 49 is high, but there is a phenomenon of mutual adhesion between too many nanowires, which inhibits Fe-W 18 O 49With the active sites fully exposed, the ammonia production rate is affected. In Comparative Example 3, the content of nanowire Fe-W 18 O 49 is low, and the number of active sites on the outer surface of the catalyst is insufficient, which also cannot meet the requirement for the reactants to be adsorbed and activated in a timely manner. In Comparative Example 2, the proportion of WO 3 to Fe-W 18 O 49 is the most appropriate, and the nitrogen fixation performance is the best.

[0094] By comparing Examples 1, 4, and 5, it can be observed that during the hydrothermal reaction process, the pH value of the solution is an important condition affecting the successful synthesis of disk-shaped WO 3 stacked by microbelts. When Fe-W 18 O 49 nanowires attach, it will also affect the microstructure of the heterojunction WO 3 / Fe-W 18 O 49 and thus produce different catalytic effects in the nitrogen fixation reaction.

[0095] By comparing Examples 1, 6, and 7, it can be known that the key step in preparing the heterojunction catalyst WO 3 / Fe-W 18 O 49 is the solvothermal process. The heating temperature affects the formation of oxygen vacancies in nanowire Fe-W 18 O 49 . Low temperature leads to insufficient oxygen vacancy content, which will affect the carrier separation efficiency. However, too many oxygen vacancies formed at high temperature will become recombination centers of electrons and holes, or cause catalyst instability. Therefore, an appropriate synthesis temperature can ensure that the content of oxygen vacancies in the catalyst is beneficial to the occurrence of the catalytic reaction.

[0096] By comparing Examples 1 and 8, it is not difficult to find that by regulating the microstructure of Fe-W 3 nanowires with disk-shaped WO 18 O 49 , the catalytic performance of the heterojunction can be optimized. Compared with rod-shaped WO 3 , the disk-shaped WO 3 has a larger specific surface area, which can reduce the aggregation of Fe-W 18 O 49 nanowires. In Example 1, a smaller nanowire structure is formed, which promotes the exposure of active sites and significantly improves the nitrogen fixation performance.

Claims

1. A disc-shaped WO3 regulates Fe-W 18 O 49 The method for preparing a photocatalytic nitrogen-fixing material having a morphology is characterized in that: The synthesis steps include: Step 1: Prepare disc-shaped WO3 using sodium tungstate and sodium chloride in an acidic solution; Step 2: Add the disc-shaped WO3 synthesized in step 1 to the alcohol solution of tungsten chloride and ferric chloride to prepare the heterojunction catalyst WO3 / Fe-W by solvothermal method 18 O 49 .

2. According to claim 1, a disc-shaped WO3 is used to regulate Fe-W 18 O 49 The method for preparing a photocatalytic nitrogen-fixing material having a morphology is characterized in that: In step 1, the synthesis of disc-shaped WO3 is performed by adding 0.1 g of sodium tungstate and 0.3 g of sodium chloride to 30 mL of deionized water, stirring for 1 h to form a clear solution, adding hydrochloric acid to the solution to adjust the pH and continuing to stir for 1 h, and the resulting solution is transferred to a high-pressure reactor and heated at 180°C for 24 h to obtain disc-shaped WO3.

3. According to claim 1, a disc-shaped WO3 is used to regulate Fe-W 18 O 49 The method for preparing a photocatalytic nitrogen-fixing material having a morphology is characterized in that: In step 2, a disc-shaped WO3 was added to 70 mL of anhydrous ethanol containing 0.1 g of tungsten chloride and 0.01 g of ferric chloride. After stirring for 30 min, the suspension was transferred to a high-pressure reactor, heated in an oven, cooled, washed, and collected. 18 O 49 .

4. According to claim 1, a disc-shaped WO3 is used to regulate Fe-W 18 O 49 The method for preparing a photocatalytic nitrogen-fixing material having a morphology is characterized in that: In step 2, the masses of the disc-shaped WO3 synthesized in step 1 added are 0.05, 0.10 and 0.15 g, and preferably the mass of the disc-shaped WO3 synthesized in step 1 added is 0.10 g.

5. According to claim 2, a disc-shaped WO3 is used to regulate Fe-W 18 O 49 The method for preparing a photocatalytic nitrogen-fixing material having a morphology is characterized in that: In step 1, undiluted concentrated hydrochloric acid is added to the solution to adjust the pH value to 1-3.

6. According to claim 3, a disc-shaped WO3 is used to control Fe-W 18 O 49 The method for preparing a photocatalytic nitrogen-fixing material having a morphology is characterized in that: In step 2, the autoclave is maintained at 180-220° C. for 20 h.

7. According to claim 3, a disc-shaped WO3 is used to control Fe-W 18 O 49 The method for preparing a photocatalytic nitrogen-fixing material having a morphology is characterized in that: In step 2, WO3 / Fe-W is washed with anhydrous ethanol. 18 O 49 4-6 times to remove possible impurity ions on the catalyst surface.

8. A disc-shaped WO3 regulates Fe-W 18 O 49 The photocatalytic nitrogen-fixing material synthesized by morphology is characterized by: The method is obtained by any one of claims 1 to 7.

9. A disc-shaped WO3 controlled Fe-W according to claim 8 18 O 49 The application of the morphologically synthesized photocatalytic nitrogen-fixing material in the field of synthetic ammonia is characterized by: Add the heterojunction catalyst WO3 / Fe-W into the reactor 18 O 49 After bubbling with pure water and 99.999% pure nitrogen, the nitrogen fixation performance test was carried out under the condition of a 300W xenon lamp simulating light source.

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