A nitrogen fixation device and method based on cyanobacterial biological nitrogen fixation mechanism

Abstract

The application relates to a nitrogen fixation device based on a cyanobacteria biological nitrogen fixation mechanism, which comprises a photoelectric anode chamber (2), a photoelectric cathode chamber (3), a photoelectric anode sheet (4), a photoelectric cathode sheet (5) and a wire (10); the photoelectric anode chamber (2) is filled with an anode electrolyte containing coenzyme Q; the photoelectric anode sheet (4) is immersed in the anode electrolyte (7); the photoelectric cathode chamber (3) is filled with a cathode electrolyte (6), and the cathode electrolyte (6) contains cyanobacteria, nitrogen-free culture medium and coenzyme Q; the photoelectric cathode sheet (5) is immersed in the cathode electrolyte (6); the photoelectric anode sheet (4) is provided with a semiconductor photoelectric material; the photoelectric anode sheet (4) is connected with the photoelectric cathode sheet (5) through the wire, and a proton exchange membrane (1) is arranged between the photoelectric anode chamber (2) and the photoelectric cathode chamber (3). The application supplies cyanobacteria with electrons generated by photoelectric materials, and cyanobacteria nitrogenase reduces nitrogen by using the electrons, so that semi-artificial high-efficiency nitrogen fixation is realized under normal temperature and pressure by taking nitrogen as raw material and taking a light source as energy.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of biological nitrogen fixation, and particularly relates to a nitrogen fixation device and method based on a cyanobacteria biological nitrogen fixation mechanism. BACKGROUND

[0002] Artificial nitrogen fixation is a very challenging work, because the cleavage of nitrogen bond requires a huge amount of energy, and the high-temperature and high-pressure conditions with high energy consumption are still adopted in the industrial nitrogen fixation. Photocatalytic nitrogen fixation is considered as a feasible scheme. However, the kinetic limitation makes it difficult for most unmodified photocatalytic materials to achieve this process. The surface free radicals of photocatalytic materials are considered as the key to activate nitrogen molecules. However, it is still difficult to break through the theoretical limit of nitrogen fixation to effectively activate nitrogen cracking and inhibit side reactions at room temperature and normal pressure.

[0003] Natural microorganisms (cyanobacteria) can reduce nitrogen to ammonia by nitrogenase at room temperature and ambient pressure to achieve nitrogen fixation. For more than a decade, semi-artificial photosynthetic systems have successfully achieved the photocatalytic synthesis of H2- and CO2- derived organic matter by integrating the metabolic mechanisms of microorganisms. These successfully constructed semi-artificial photosynthetic systems make semi-artificial photocatalytic nitrogen fixation possible. However, the low efficiency of electron transfer between photocatalysts and biological components greatly limits the development of semi-artificial photocatalytic nitrogen fixation technology. SUMMARY

[0004] (I) Technical problems to be solved

[0005] In view of the above-mentioned shortcomings and deficiencies of the prior art, the present application provides a nitrogen fixation device and method based on a cyanobacteria biological nitrogen fixation mechanism, which can realize efficient semi-artificial catalytic nitrogen fixation under room temperature and normal pressure conditions with nitrogen as raw material and natural light source or artificial light source as energy. The nitrogen fixation process is clean and pollution-free, and can output ammonia fertilizer and hydrogen and other products, which solves the technical problem of low photocatalytic nitrogen fixation capacity in the prior art.

[0006] (II) Technical solutions

[0007] In order to achieve the above-mentioned purposes, the present application provides a nitrogen fixation device based on a cyanobacteria biological nitrogen fixation mechanism, which comprises: a photoanode chamber (2), a photocathode chamber (3), a photoanode sheet (4), a photocathode sheet (5) and a wire (10).

[0008] The photoelectric anode chamber (2) contains anode electrolyte (7), which is an electrolyte solution containing coenzyme Q; the photoelectric anode sheet (4) is immersed in the anode electrolyte (7); the photoelectric cathode chamber (3) contains cathode electrolyte (6), which contains cyanobacteria, nitrogen-free medium suitable for cultivating cyanobacteria and coenzyme Q; the photoelectric cathode sheet (5) is immersed in the cathode electrolyte (6); the photoelectric anode sheet (4) is provided with a semiconductor photoelectric material capable of generating free electrons through photoelectric effect;

[0009] The photoelectric anode sheet (4) is connected to the photoelectric cathode sheet (5) by a wire, and a proton exchange membrane (1) is arranged between the photoelectric anode chamber (2) and the photoelectric cathode chamber (3), which separates the anode electrolyte (7) from the cathode electrolyte (6) but allows protons to pass through.

[0010] According to the preferred embodiment of the present application, the photoelectric anode chamber (2) and the photoelectric cathode chamber (3) are groove structures made of light-transmitting materials.

[0011] According to the preferred embodiment of the present application, the nitrogen fixation device further comprises an external light source (9) that irradiates the photoelectric anode sheet (4) in the anode electrolyte (7) to generate photoelectric effect, generating electrons and holes in the photoelectric anode sheet (4), and the electrons move to the photoelectric cathode sheet (5) along the wire (10); the external light source (9) irradiates the cathode electrolyte (6) to provide the light energy required for the photosynthesis of cyanobacteria.

[0012] According to the preferred embodiment of the present application, the photoelectric anode chamber (2) and the photoelectric cathode chamber (3) are groove structures made of non-light-transmitting materials, and at this time, an internal light source is arranged inside the photoelectric anode chamber (2) and the photoelectric cathode chamber (3).

[0013] According to the preferred embodiment of the present application, the photoelectric cathode chamber (3) is a closed groove structure and is provided with a nitrogen gas inlet, which communicates with the inside and outside of the photoelectric cathode chamber (3) and is used to supply nitrogen gas to the photoelectric cathode chamber (3). The nitrogen gas inlet is also provided with a gas guide pipe for dispersing nitrogen gas into the inside of the cathode electrolyte (6), and the lower end of the gas guide pipe is connected to a distributor or a pipe wall is provided with a plurality of gas permeable holes.

[0014] According to the preferred embodiment of the present application, the photoelectric anode chamber (2) is a closed groove structure and is provided with a gas exchange hole, which is used to guide the oxygen generated in the photoelectric anode chamber (2) out.

[0015] According to the preferred embodiment of the present application, the photoelectric anode sheet (4) comprises a carrier and a titanium dioxide-based semiconductor material covering the surface of the carrier.

[0016] According to a preferred embodiment of the present application, the conductive glass is one or more of indium tin oxide, fluorine-doped SnO2, and zinc oxide-based materials.

[0017] According to a preferred embodiment of the present application, the preparation method of the photoanode sheet (4) is as follows:

[0018] Step 1: Disperse the titanium dioxide-based semiconductor material into anhydrous ethanol containing 3-6 wt% Nafion solution for 15-25 min under ultrasonic for standby, to obtain a titanium dioxide-based semiconductor film-forming slurry;

[0019] Step 2: Apply the titanium dioxide-based semiconductor film-forming slurry to the conductive glass, and dry by baking to obtain the photoanode sheet (4). The conductive glass is preheated by a baking lamp.

[0020] According to a preferred embodiment of the present application, the photocathode sheet (5) is a carbon cloth, a copper sheet, a silver sheet, or a platinum sheet.

[0021] According to a preferred embodiment of the present application, the wire (10) is a copper wire or a platinum wire.

[0022] According to a preferred embodiment of the present application, the cyanobacteria are one or more of Nostoc, Anabaena, Oscillatoria, Gleocapsa, and Chroococcus.

[0023] According to a preferred embodiment of the present application, the cyanobacteria inoculated into the cathode electrolyte (6) are purified nitrogen-fixing cyanobacteria obtained after 5 generations of culture in a nitrogen-free medium.

[0024] According to a preferred embodiment of the present application, the anode electrolyte (7) is a phosphate buffer containing coenzyme Q.

[0025] According to a preferred embodiment of the present application, in the anode electrolyte (7) and the cathode electrolyte (6), the coenzyme Q is any one or a combination of several of coenzyme Q0-10; the concentration of coenzyme Q is 0.02-1 mg / mL.

[0026] According to a preferred embodiment of the present application, in the cathode electrolyte (6), the inoculation concentration of cyanobacteria is 4.24E8-3.81E7 cell / mL.

[0027] In a second aspect, the present application provides a nitrogen fixation method based on the nitrogen fixation mechanism of cyanobacteria, which uses the nitrogen fixation device of any of the above embodiments for nitrogen fixation. During the nitrogen fixation process, artificial or natural light sources are provided to the photoanode chamber (2) and the photocathode chamber (3), and free nitrogen is introduced into the photocathode chamber (3). After the operation of the nitrogen fixation device, oxygen is collected in the photoanode chamber (2), and an algal liquid rich in ammonia or ammonium salt is collected in the photocathode chamber (3). The algal liquid can be used to make liquid or solid nitrogen fertilizer.

[0028] (III) Beneficial Effects

[0029] The device of the present application combines the photoelectric effect of photoelectric semiconductor material with the nitrogen fixation mechanism and photosynthesis of cyanobacteria, and realizes efficient semi-artificial catalytic nitrogen fixation under normal temperature and pressure conditions with nitrogen as raw material and natural light or artificial light as energy source. The nitrogen fixation process is clean and pollution-free, and solves the problems of high energy consumption and great difficulty in artificial nitrogen fixation. The photosynthesis mechanism of cyanobacteria ensures a sufficient number of cyanobacteria and maintains the life activity of cyanobacterial cells, produces more nitrogenase, improves the activity of nitrogenase, provides the energy required for life activities (cell metabolism proliferation and nitrogen fixation, etc.), and realizes photosynthetic nitrogen fixation.

[0030] Reducing one molecule of nitrogen requires the consumption of 6 electrons, and the electrons consumed in the cyanobacterial nitrogen fixation process will also cause oxidative damage to themselves, thereby reducing nitrogen fixation, and external electron supply can solve this problem.

[0031] The present application utilizes the performance of photoelectric semiconductor that can rapidly undergo charge separation under light excitation, uses coenzyme Q as an electronic relay, and integrates the cyanobacterial nitrogen fixation mechanism with photosynthetic nitrogen fixation ability through photoelectrochemical means; coenzyme Q ensures efficient transfer of electrons from semiconductor materials to cyanobacteria, in addition to the electrons produced by cyanobacterial photosynthesis, the photoelectric effect of photoelectric semiconductor supplements the required electrons for nitrogen fixation. Among them, the electrons produced by the semiconductor under light excitation are transferred to the photo-cathode sheet, and then rapidly transferred to the cyanobacterial cells in the cathode electrolyte through coenzyme Q, the nitrogenase of cyanobacterial cells receives the externally supplied electrons, and realizes efficient nitrogen fixation under normal temperature and pressure.

[0032] The present application adds coenzyme Q as an electronic relay in both the anode electrolyte and the cathode electrolyte, ensuring that continuous charge separation and electron production can occur on the photo-anode sheet, and that efficient and rapid transfer of electrons from the photo-cathode sheet to the nitrogenase of cyanobacteria can be achieved.

[0033] The present application uses titanium dioxide-based materials as photoexcitation materials and cyanobacteria as nitrogen-fixing microorganisms, and the reaction can be carried out under normal temperature and pressure and natural light conditions, the nitrogen fixation conditions are mild, the energy consumption is low, the raw materials are easy to obtain, the source is abundant, and the nitrogen fixation product can be obtained by centrifuging the cathode electrolyte. The ammonia / ammonium-rich product can be further processed into agricultural nitrogen fertilizer. BRIEF DESCRIPTION OF DRAWINGS

[0034] Figure 1 is a schematic diagram of the nitrogen fixation device based on the cyanobacterial biological nitrogen fixation mechanism of the present application.

[0035] Figure 2 is a cyclic voltammogram during the nitrogen fixation process of Example 1 using the nitrogen fixation device of the present application.

[0036] Figure 3The cyclic voltammogram for the nitrogen fixation process using the nitrogen fixation device of the present invention is shown in Example 2.

[0037] Figure 4 The cyclic voltammogram is shown in Example 3, which illustrates the nitrogen fixation process using the nitrogen fixation device of the present invention.

[0038] Figure 5 The ammonia content generated in the cathode electrolyte when nitrogen is fixed using the nitrogen fixation device described in Example 1 is shown.

[0039] Figure 6 The ammonia content generated in the cathode electrolyte when nitrogen is fixed using the nitrogen fixation device described in Example 2 is shown.

[0040] Figure 7 The ammonia content generated in the cathode electrolyte when nitrogen is fixed using the nitrogen fixation device described in Example 3 is shown.

[0041] Figure 8 The ammonia content generated in the cathode electrolyte when nitrogen is fixed using the nitrogen fixation device described in Example 4 is shown. Detailed Implementation

[0042] To better explain and facilitate understanding of the present invention, the present invention will be described in detail below with reference to the accompanying drawings and specific embodiments.

[0043] like Figure 1 The diagram shows a nitrogen fixation device based on the cyanobacterial biological nitrogen fixation mechanism of the present invention. The fixation device includes a photoanode chamber 2, a photocathode chamber 3, a photoanode plate 4, a photocathode plate 5, and a wire 10. The photoanode chamber 2 contains an anolyte 7, which is an electrolyte solution containing coenzyme Q. The photoanode plate 4 is immersed in the anolyte 7, and a semiconductor photoelectric material capable of generating free electrons through the photoelectric effect is disposed on the photoanode plate 4. Preferably, the photoanode plate 4 comprises a carrier and a titanium dioxide-based semiconductor material covering the surface of the carrier, wherein the carrier can be conductive glass; preferably, the conductive glass is one or more of indium tin oxide, fluorine-doped SnO2, and zinc oxide-based materials. The carrier can be electrically connected to the wire 10. The wire 10 can be a low-resistance copper wire or platinum wire. The photoanode plate 4 can be prepared by the following method:

[0044] Step 1: Disperse the titanium dioxide-based semiconductor material in anhydrous ethanol containing 3-6 wt% Nafion solution and sonicate for 15-25 min for later use to obtain titanium dioxide-based semiconductor film-forming slurry;

[0045] Step 2: Coat the titanium dioxide-based semiconductor film-forming slurry (coating amount 0.04-1 mg / cm²). 2 The photoelectric anode sheet 4 is obtained by baking and drying on conductive glass that has been preheated by a baking lamp.

[0046] The cathode electrolyte 6 is filled in the photoelectric cathode chamber 3, and contains blue algae, nitrogen-free culture medium suitable for cultivating blue algae and coenzyme Q. The photoelectric cathode sheet 5 is immersed in the cathode electrolyte 6, and is made of electrode materials such as carbon cloth, copper sheet, silver sheet or platinum sheet. One end of the photoelectric anode sheet 4 is connected to the photoelectric cathode sheet 5 by a wire, and a proton exchange membrane 1 is arranged between the photoelectric anode chamber 2 and the photoelectric cathode chamber 3. The proton exchange membrane separates the anode electrolyte 7 from the cathode electrolyte 6, but allows protons to pass through.

[0047] The principle of realizing high-efficiency nitrogen fixation of the nitrogen fixation device is that the light source irradiates the photoelectric anode sheet in the anode electrolyte to excite photoelectric effect, holes and free electrons are generated on the surface of the photoelectric anode sheet, the free electrons move to the photoelectric cathode sheet along the wire, the coenzyme Q in the cathode electrolyte is used as an electronic relay to receive the electrons and efficiently transfer the electrons to the blue algae in the cathode electrolyte, and the nitrogen fixation enzyme of the blue algae reduces the free nitrogen to negative valence state N after receiving the electrons. In the anode electrolyte, water and the holes generated on the surface of the photoelectric anode sheet react to generate protons and oxygen, the protons pass through the proton exchange membrane into the cathode electrolyte and combine with the negative valence state N to form ammonia. The negative valence state N is ionized in the anode electrolyte, and the hydroxyl radicals react with the holes to fill the holes with electrons, so that the photoelectric anode sheet continuously generates charge separation under irradiation. In addition, the blue algae in the cathode electrolyte occurs normal photosynthesis under irradiation to maintain a sufficient number of blue algae cells and life activities, generate more nitrogen fixation enzymes, improve the activity of the nitrogen fixation enzymes, provide energy required for life activities (proliferation metabolism and nitrogen fixation), and realize high-efficiency nitrogen fixation.

[0048] In the process of using the above nitrogen fixation device, the following reactions occur in the anode electrolyte 7:

[0049] 2H2O + 4h + → 4H + + O2

[0050] 2h + + 2OH - → H2O + 1 / 2O2

[0051] In the process of using the above nitrogen fixation device, the following reactions occur in the cathode electrolyte 6:

[0052] The coenzyme (such as Q0) is used to transfer electrons:

[0053] e - + Q0 → OxQ0 → RedQ0 + e - → e - + N2 + H + + blue algae → NH3

[0054] In order to facilitate the irradiation of natural light or external light source, the photoanode chamber 2 and the photocathode chamber 3 are both provided as a groove structure made of light-transmitting material, and a matching external light source 9 can be provided, so as to excite the photoelectric effect of the photoanode sheet and provide the light energy required for the photosynthesis of cyanobacteria. Of course, the photoanode chamber 2 and the photocathode chamber 3 can also be light-tight, in which case an internal light source needs to be provided inside the photoanode chamber 2 and the photocathode chamber 3.

[0055] As shown in Figure 1 The photocathode chamber 3 is a closed groove structure, and is provided with a nitrogen inlet 81, and a gas guide pipe 811 is installed at the nitrogen inlet 81, and the lower end of the gas guide pipe 811 is connected to a distributor or a pipe wall provided with a plurality of gas permeable holes. The nitrogen inlet 81 and the gas guide pipe 811 are used to facilitate the introduction of free nitrogen into the interior of the cathode electrolyte 6 and fully contact the cyanobacterial cells. It should be noted that the photocathode chamber 3 can also be provided as a non-closed groove, but considering that the ammonia produced is easy to volatilize from the cathode electrolyte 6 after heating, which reduces the recovery rate, it is preferred that the photocathode chamber 3 is provided as a closed groove structure. The closed groove can also isolate the contamination of the cyanobacterial culture medium and improve the utilization rate of nitrogen.

[0056] The photoanode chamber 2 can also be a closed groove structure, and is provided with a gas exchange hole 82 for guiding the oxygen generated in the photoanode chamber 2 out of the chamber. The oxygen generated in the anode electrolyte 7 can be quickly discharged by introducing nitrogen, so as to avoid the influence of high oxygen content on the chemical reaction on the photoanode sheet. The closed groove can effectively isolate the pollution. In addition, the photoanode chamber 2 can also be a non-closed groove.

[0057] In the present application, the cyanobacteria are any one or a combination of the following blue algae series that can fix nitrogen: nostoc, anabaena, monactin, chroococcus and anabaenopsis. Preferably, the cyanobacteria are purified nitrogen-fixing cyanobacteria obtained after 5 generations of culture in a nitrogen-free medium (Ashby nitrogen-free medium). The inoculation concentration of the cyanobacteria in the cathode electrolyte 6 is 4.24E8-3.81E7 cells / mL. The concentration of coenzyme Q in the cathode electrolyte 6 is 0.02-1 mg / mL, and the coenzyme Q can be any one or a combination of coenzyme Q0-10. The anode electrolyte 7 is preferably a phosphate buffer containing coenzyme Q, and the concentration of coenzyme Q is 0.02-1 mg / mL, and the coenzyme Q can be any one or a combination of coenzyme Q0-10.

[0058] The following will be further described in combination with the embodiments of the present application.

[0059] Example 1

[0060] In this embodiment, the above-mentioned nitrogen fixation device is used for nitrogen fixation experiment, and the experimental method includes:

[0061] (1) Take 8 mg of titanium dioxide composite powder and disperse it in 1 mL of anhydrous ethanol containing 50 μL of 5% Nafion solution for 20 min; coat the obtained material on FTO conductive glass under a baking lamp and dry it in an oven for 48 h to obtain photoanode sheet 4. Use carbon cloth as photocathode sheet 5.

[0062] (2) Take 0.1 mg of coenzyme Q0 material and disperse it in 10 mL of phosphate buffered saline solution for 2 min to obtain anode electrolyte 7.

[0063] (3) Use nitrogen-free medium (Ashby nitrogen-free medium) to culture the nostoc, and obtain purified nitrogen-fixing cyanobacteria after 5 generations; add 0.1 mg of coenzyme Q0 to 10 mL of 7.0E7 cell / mL purified nostoc in nitrogen-free medium to obtain cathode electrolyte 6.

[0064] (3) Use proton exchange membrane 1 to separate the two chambers, and assemble photoanode sheet 4 and photocathode sheet 5 into photoanode chamber 2 and photocathode chamber 3, respectively; add equal amounts of anode electrolyte 7 and cathode electrolyte 6 into the electrode chambers.

[0065] (4) Inject 20 mL of N2 into cathode electrolyte 6 through nitrogen inlet 81, and turn on external light source 9 to irradiate and operate to realize photocatalytic nitrogen fixation at normal temperature and pressure.

[0066] Nitrogen fixation effect test

[0067] Test the redox effect by cyclic voltammetry curves under dark and light conditions (use the device without adding coenzyme Q as a control); the experimental results are shown in Table 1. Figure 2

[0068] After 8 min of irradiation, centrifuge cathode electrolyte 6 to obtain a clear solution, and use an ammonia kit to quantitatively detect the ammonia content (use the experiment of directly using the nostoc in the cathode electrolyte for photosynthetic nitrogen fixation under the same light intensity and irradiation time without using the nitrogen fixation device as a control); the experimental results are shown in Table 2. Figure 5

[0069] Example 2

[0070] This example uses the above-mentioned nitrogen fixation device to perform nitrogen fixation experiments, and the experimental method includes:

[0071] (1) Take 8 mg of titanium dioxide composite powder and disperse it in 1 mL of anhydrous ethanol containing 50 μL of 5% Nafion solution for 20 min; coat the obtained material on FTO conductive glass under a baking lamp and dry it in an oven for 48 h to obtain photoanode sheet 4. Use carbon cloth as photocathode sheet 5.

[0072] ​​(2) Take 0.2 mg coenzyme Q0 material dispersed in 10 mL phosphate buffered saline solution, ultrasonic for 2 min as anode electrolyte 7.

[0073] (3) Use nitrogen-free medium to culture Anabaena, and after 5 generations, obtain purified nitrogen-fixing cyanobacteria for standby; add 0.2 mg coenzyme Q0 to 10 mL 7.0E7 cell / mL purified Anabaena-containing nitrogen-free medium as cathode electrolyte 6.

[0074] (3) Use proton exchange membrane 1 to separate the two chambers, and assemble photoanode sheet 4 and photocathode sheet 5 into photoanode chamber 2 and photocathode chamber 3 respectively; add equal amounts of anode electrolyte 7 and cathode electrolyte 6 into the electrode chambers.

[0075] (4) Inject 20 mL N2 into cathode electrolyte 6 through nitrogen inlet 81, and turn on external light source 9 for irradiation operation to realize photocatalytic nitrogen fixation at normal temperature and pressure.

[0076] Nitrogen fixation effect test

[0077] Test the redox effect under dark and light conditions by cyclic voltammetry curve (use the device without adding coenzyme Q as a control); the experimental results are shown in Figure 3 .

[0078] After 8 min of irradiation, centrifuge the cathode electrolyte 6 to obtain the supernatant, and use the ammonia kit to quantitatively detect the ammonia content (use the same light intensity and light duration conditions, without using the nitrogen fixation device to directly utilize the Anabaena photosynthetic nitrogen fixation experiment in the cathode electrolyte as a control); the experimental results are shown in Figure 6 .

[0079] Example 3

[0080] This example uses the above-mentioned nitrogen fixation device for nitrogen fixation experiment, and the experimental method includes:

[0081] (1) Take 8 mg titanium dioxide composite powder and disperse it in 1 mL anhydrous ethanol containing 50 μL 5% Nafion solution and ultrasonic for 20 min; coat the obtained material on FTO conductive glass under a baking lamp, and dry in an oven for 48 h to obtain photoanode sheet 4. Use carbon cloth as photocathode sheet 5.

[0082] (2) Take 0.4 mg coenzyme Q0 material dispersed in 10 mL phosphate buffered saline solution, ultrasonic for 2 min as anode electrolyte 7.

[0083] (3) Use nitrogen-free medium to culture Anabaena, and after 5 generations, obtain purified nitrogen-fixing cyanobacteria for standby; add 0.4 mg coenzyme Q0 to 10 mL 7.0E7 cell / mL purified Anabaena-containing nitrogen-free medium as cathode electrolyte 6.

[0084] (3) Using proton exchange membrane 1 to separate two chambers, assembling photoanode sheet 4 and photocathode sheet 5 into photoanode chamber 2 and photocathode chamber 3 respectively; adding equal amount of anode electrolyte 7 and cathode electrolyte 6 into electrode chambers.

[0085] (4) Injecting 20 mL N2 into cathode electrolyte 6 through nitrogen inlet 81, and opening external light source 9 to irradiate and run to realize photocatalytic nitrogen fixation at normal temperature and pressure.

[0086] Nitrogen fixation effect test

[0087] The redox effect is detected by testing cyclic voltammetry curves under dark and light conditions (using the device without adding coenzyme Q as a control); the experimental results are shown in Figure 4 .

[0088] After irradiation for 8 min, the cathode electrolyte 6 is centrifuged to obtain a clear solution, and the ammonia content is quantitatively detected by an ammonia kit (using the same light intensity and light duration conditions, without using the nitrogen fixation device to directly utilize the nitrogen fixation of the cathode electrolyte by the chlorella photosynthesis experiment as a control); the experimental results are shown in Figure 7 .

[0089] Example 4

[0090] This example uses the above-mentioned nitrogen fixation device to perform nitrogen fixation experiments, and the experimental method includes:

[0091] (1) Dispersing 8 mg of titanium dioxide composite powder into 1 mL of anhydrous ethanol containing 50 μL of 5% Nafion solution and ultrasonicating for 20 min; coating the obtained material on FTO conductive glass under a baking lamp, and drying in an oven for 48 h to obtain a photoanode sheet 4. Carbon cloth is used as a photocathode sheet 5.

[0092] (2) Dispersing 0.2 mg of coenzyme Q0 material in 10 mL of phosphate buffered saline solution and ultrasonicating for 2 min to obtain an anode electrolyte 7.

[0093] (3) Culturing chlorella in a nitrogen-free medium, and obtaining purified nitrogen-fixing cyanobacteria after 5 generations for standby; adding 0.2 mg of coenzyme Q0 to 10 mL of 9.0E7 cell / mL (9.0 x 10 7 cell / mL) purified chlorella in a nitrogen-free medium to obtain a cathode electrolyte 6.

[0094] (3) Using proton exchange membrane 1 to separate two chambers, assembling photoanode sheet 4 and photocathode sheet 5 into photoanode chamber 2 and photocathode chamber 3 respectively; adding equal amount of anode electrolyte 7 and cathode electrolyte 6 into electrode chambers.

[0095] (4) The nitrogen gas is injected into the cathode electrolyte 6 through the nitrogen gas injection port 81, and the external light source 9 is turned on to irradiate, so that the photocatalytic nitrogen fixation can be realized at normal temperature and pressure.

[0096] Nitrogen fixation effect test

[0097] After the light irradiation for 20 minutes, the cathode electrolyte 6 is centrifuged to obtain a clear solution, and the ammonia content is quantitatively detected by using an ammonia kit (under the same light intensity and light irradiation time, the direct use of the cathode electrolyte for nitrogen fixation of the chlorella by photosynthesis is used as a control); the experimental results are shown in Table 1. Figure 8

[0098] From the experimental results of Examples 1-3 Figures 2-4 It can be seen that, compared with the control group without adding coenzyme Q, the addition of coenzyme Q as an electronic relay in the anode electrolyte and the cathode electrolyte significantly enhances the cathode reduction peak under light irradiation, indicating that the electrons are effectively transferred to the chlorella to assist photosynthetic nitrogen fixation.

[0099] From the experimental results of Examples 1-4 Figures 5-8 It can be seen that, compared with the control group without using the nitrogen fixation device to directly use the cathode electrolyte for nitrogen fixation of the chlorella by photosynthesis, the ammonia content produced by using the nitrogen fixation device of the present application is increased by 5.80 times (Example 1), 8.44 times (Example 2), 12.98 times (Example 3) and 28.98 times (Example 4), and it can be found from Examples 1-3 that the more the amount of coenzyme Q added in the electrolyte, the higher the nitrogen fixation efficiency, and it can also be seen from Example 4 that the longer the light irradiation time, the higher the ammonia content in the cathode electrolyte.

[0100] Finally, it should be noted that: the above examples are only used to illustrate the technical solutions of the present application, but not to limit them; although the present application has been described in detail with reference to the foregoing examples, those skilled in the art should understand that they can still modify the technical solutions described in the foregoing examples, or make equivalent substitutions for part or all of the technical features; and these modifications or substitutions do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present application.​

Claims

1. A nitrogen fixation device based on the nitrogen fixation mechanism of cyanobacteria, characterized in that, It includes: The device comprises a photoanode chamber (2), a photocathode chamber (3), a photoanode plate (4), a photocathode plate (5), and a wire (10). The photoanode chamber (2) contains an anolyte (7), which is an electrolyte solution containing coenzyme Q. The anolyte (7) is a phosphate buffer solution containing coenzyme Q. The photoanode plate (4) is immersed in the anolyte (7). The photocathode chamber (3) contains a cathode electrolyte (6), which contains cyanobacteria, a nitrogen-free culture medium suitable for culturing cyanobacteria, and coenzyme Q. The photocathode chamber (3) is a closed tank structure with a nitrogen inlet connected to the inside and outside of the photocathode chamber (3) for supplying nitrogen to the photocathode chamber (3). The concentration of coenzyme Q in the anolyte (7) and the cathode electrolyte (6) is 0.02-1 mg / mL. The photocathode (5) is immersed in the cathode electrolyte (6); the photoanode (4) is provided with a semiconductor photoelectric material that can generate free electrons through the photoelectric effect; The nitrogen fixation device also includes an external light source (9), which is a natural light source or an artificial light source. The external light source (9) irradiates the photoanode plate (4) in the anolyte (7) to generate a photoelectric effect. Electrons and holes are generated in the photoanode plate (4). The electrons move along the wire (10) to the photocathode plate (5). With the help of coenzyme Q in the cathode electrolyte, the electrons are received and transferred to the cyanobacteria in the cathode electrolyte. After the cyanobacterial nitrogenase receives the electrons, it reduces the free nitrogen gas to the negative valence state N. The photocathode plate (4) is connected to the photocathode plate (5) by a wire, and a proton exchange membrane (1) is provided between the photocathode chamber (2) and the photocathode chamber (3). The proton exchange membrane separates the anolyte (7) from the catholyte (6) but allows protons to pass through.

2. The nitrogen fixation device based on the cyanobacterial biological nitrogen fixation mechanism according to claim 1, characterized in that, The photoelectric anode chamber (2) and the photoelectric cathode chamber (3) are tank structures made of light-transmitting material.

3. The nitrogen fixation device based on the cyanobacterial biological nitrogen fixation mechanism according to claim 1 or 2, characterized in that, The external light source (9) irradiates the cathode electrolyte (6) to provide the light energy required for cyanobacterial photosynthesis.

4. The nitrogen fixation device based on the cyanobacterial biological nitrogen fixation mechanism according to claim 1, characterized in that, The nitrogen inlet is also provided with a gas guide pipe for dispersing nitrogen into the cathode electrolyte (6), and the lower end of the gas guide pipe is connected to a distributor or has several vent holes on the pipe wall.

5. The nitrogen fixation device based on the cyanobacterial biological nitrogen fixation mechanism according to claim 1, characterized in that, The photoelectric anode chamber (2) is a closed tank structure and is provided with a gas exchange hole, which is used to export the oxygen generated by the photoelectric anode chamber (2).

6. The nitrogen fixation device based on the cyanobacterial biological nitrogen fixation mechanism according to claim 1, characterized in that, The photocathode (5) is made of carbon cloth, copper, silver or platinum; the conductor (10) is made of copper or platinum wire.

7. The nitrogen fixation device based on the cyanobacterial biological nitrogen fixation mechanism according to claim 1, characterized in that, The cyanobacteria mentioned are one or more of the following: Nostoc, Anabaena, Monofibrillaris, Sphaerophyta, and Collegiformis.

8. The nitrogen fixation device based on the cyanobacterial biological nitrogen fixation mechanism according to claim 1, characterized in that, Coenzyme Q is any one or a combination of several of the coenzyme Q0-10.

9. A nitrogen fixation method based on the nitrogen fixation mechanism of cyanobacteria, wherein the nitrogen fixation device based on the nitrogen fixation mechanism of cyanobacteria as described in any one of claims 1-8 is used for nitrogen fixation, wherein during the nitrogen fixation process, artificial light or natural light is provided to the photoanode chamber (2) and the photocathode chamber (3), and free nitrogen gas is introduced into the photocathode chamber (3); after the nitrogen fixation device is operated, oxygen is collected in the photoanode chamber (2); and algal liquid rich in ammonia or ammonium salts is collected in the photocathode chamber (3).

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