Pyridyl cation modified cobalt porphyrin, preparation method and application of pyridyl cation modified cobalt porphyrin in electro-catalysis of nitrate reduction
By designing a pyridyl cationic modified cobalt porphyrin catalyst, the problem of low efficiency in the electrocatalytic reduction of nitrate to ammonia was solved, achieving a highly efficient and stable conversion of nitrate to ammonia.
Patent Information
- Application Number
- CN202511061812.1
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-07-30
- Publication Date
- 2025-11-21
AI Technical Summary
In existing technologies, the efficiency of electrocatalytic reduction of nitrate to ammonia is low, and the low concentration of nitrate in water is not conducive to catalyst adsorption, resulting in insufficient ammonia production efficiency and a large number of by-products.
We designed a pyridyl cationic modified cobalt porphyrin catalyst. By modifying the cobalt porphyrin with nitrate adsorption groups through molecular design, we can increase the local nitrate concentration and reduce the electron cloud density of the cobalt porphyrin center, thereby improving catalytic stability.
The efficient and directional conversion of nitrate to ammonia was achieved, with improved catalytic efficiency, an ammonia yield of 196.3 μmol/h/cm2, a Faraday efficiency of 90%, and good stability.
Smart Images
Figure CN120987955A_ABST
Abstract
Description
TECHNICAL FIELD
[0001] The present application belongs to the technical field of water treatment, and particularly relates to a pyridyl cation modified cobalt porphyrin and a preparation method thereof, and application of the pyridyl cation modified cobalt porphyrin to electrocatalytic reduction of nitrate in water to produce ammonia. BACKGROUND
[0002] The technical field of water treatment has made remarkable progress in environmental pollution control and resource recovery in recent years. The electrocatalytic reduction technology has become a research hotspot due to its high efficiency and cleanness. Nitrate (NO3 - ) as a common pollutant in water bodies mainly comes from agricultural activities, industrial wastewater and domestic sewage. Excessive existence of nitrate will lead to water eutrophication, threatening the ecological system and human health. Traditional nitrate treatment technologies (such as reverse osmosis, biological denitrification, etc.) have problems such as high energy consumption, difficult control of by-products or secondary pollution, etc. The electrocatalytic reduction technology can efficiently convert nitrate into high-value-added ammonia (NH3) under mild conditions by driving the reaction with green electricity, realizing the resource utilization of pollutants.
[0003] Ammonia is an important raw material for the production of agricultural fertilizers and chemical products. The Haber-Bosch process is used in traditional industry for ammonia synthesis, but it can only be carried out under high temperature and high pressure conditions, which has the disadvantage of high energy consumption. The electrocatalytic reduction of nitrate to produce ammonia is a multi-electron and proton transfer process (NO3 - + 9H + + 8e - → NH3 + 3H2O), which directly converts nitrate in water into ammonia, and has the dual advantages of water nitrogen pollutant removal and energy conversion. In water bodies, the concentration of nitrate is usually very low, which is not conducive to the adsorption of nitrate on the catalytic center, resulting in low ammonia synthesis efficiency. Therefore, how to improve the catalytic efficiency is of great significance to realize the efficient and directional conversion of nitrate to ammonia. SUMMARY
[0004] The purpose of the present application is to provide a pyridyl cation modified cobalt porphyrin and a preparation method thereof, and application of the pyridyl cation modified cobalt porphyrin to electrocatalytic reduction of nitrate in water to produce ammonia, which can improve the catalytic efficiency and realize the efficient and directional conversion of nitrate to ammonia.
[0005] In a first aspect, the present application provides a pyridyl cation modified cobalt porphyrin catalyst, which has a structure shown in formula (I):
[0006]
[0007] In a second aspect, the present application provides a preparation method of the aforementioned pyridyl cation modified cobalt porphyrin catalyst, which comprises the following preparation steps:
[0008] (1) 2,2'-dipyrromethane and o-bromobenzaldehyde are dissolved in solvent A, after oxygen removal, trifluoroacetic acid is added, stirred uniformly, then 2,3-dichloro-5,6-dicyano-1,4-benzoquinone is added, stirred to react, after the reaction is completed, triethylamine is added to terminate the reaction, 5,15-di(2-benzylbromide)porphyrin ligand is obtained, 5,15-di(2-benzylbromide)porphyrin ligand and zinc acetate are dissolved in solvent B, and the reaction is carried out in the dark to obtain 5,15-di(2-benzylbromide)zinc porphyrin compound with the structure shown in formula (II);
[0009]
[0010] (2) 5,15-di(2-benzylbromide)zinc porphyrin compound obtained in step (1) is dissolved in solvent C, oxygen is removed, N-bromosuccinimide is added, and the reaction is carried out to obtain 5,15-dibromo-10,20-di(2-benzylbromide)zinc porphyrin compound with the structure shown in formula (III);
[0011] (3) 5,15-dibromo-10,20-di(2-benzylbromide)zinc porphyrin compound in step (2) and pyridine are added to solvent D, and the reaction is carried out in the dark to obtain 5,15-dibromo-10,20-di(2-benzylpyridine)zinc porphyrin compound with the structure shown in formula (IV):
[0012]
[0013]
[0014] (4) 5,15-dibromo-10,20-di(2-benzylpyridine)zinc porphyrin in step (3) is dissolved in solvent E, concentrated hydrochloric acid is added, and the reaction is stirred, after the reaction is completed, 5,15-dibromo-10,20-di(2-benzylpyridine)porphyrin ligand is obtained, and the prepared 5,15-dibromo-10,20-di(2-benzylpyridine)porphyrin ligand is dissolved in solvent F, and cobalt acetate is added to carry out heating reaction, after the reaction is completed, the pyridyl cation modified cobalt porphyrin catalyst is obtained.
[0015] Optionally, in step (1), the molar ratio of 2,2'-dipyrromethane, o-bromobenzaldehyde, trifluoroacetic acid and 2,3-dichloro-5,6-dicyano-1,4-benzoquinone is 1-4: 1-4: 4-12: 1-6; the molar ratio of 5,15-di(2-benzylbromide)porphyrin ligand and zinc acetate is 0.02-0.1: 0.2-1.5; the stirring reaction time is 0.3-1.5 h, and the temperature of the dark reaction is 60-80℃, and the time is 1-5 h.
[0016] Optionally, in step (2), the molar ratio of the 5,15-di(2-benzyl bromide) zinc porphyrin compound to N-bromosuccinimide is 0.02-0.1:0.04-0.2, and the reaction time is 0.3-1.5 h.
[0017] Optionally, in step (3), the molar ratio of the 5,15-dibromo-10,20-di(2-benzyl bromide) zinc porphyrin to pyridine is 0.02-1.5:0.1-0.4, the temperature of the light-avoiding reaction is 60-80℃, and the reaction time is 1-5 h.
[0018] Optionally, the reaction products in steps (1), (2) and (3) are all purified by column chromatography.
[0019] Optionally, in step (4), the molar volume ratio of the 5,15-dibromo-10,20-di(2-benzyl pyridine) zinc porphyrin to concentrated hydrochloric acid is 0.02-0.1 mmol:1-5 mL, the stirring reaction time is 1-5 h; the molar ratio of the 5,15-dibromo-10,20-di(2-benzyl pyridine) porphyrin ligand to cobalt acetate is 0.02-0.1:0.1-1.0, the heating reaction temperature is 50-75℃, and the reaction time is 1-5 h.
[0020] Optionally, the reaction product in step (4) is extracted with water and dichloromethane, the organic phase is collected, and then subjected to reduced pressure distillation.
[0021] The third invention provides an application of the aforementioned pyridyl cation modified cobalt porphyrin catalyst in electrocatalytic nitrate reduction.
[0022] Optionally, the electrode loaded with the catalyst and carbon material is used as the cathode in the electrocatalytic nitrate reduction reaction, the carbon rod is used as the anode, and the solution including sodium nitrate is used as the electrolyte.
[0023] In summary, the present application has at least one of the following beneficial effects:
[0024] The present application provides a pyridyl cation modified cobalt porphyrin catalyst, which is synthesized by molecular design principles, and is used for the electrocatalytic reduction of nitrate to ammonia in water. The nitrate in water can be adsorbed by the positively charged pyridyl group, thereby increasing the local concentration of nitrate, and significantly improving the efficiency of the electrocatalytic reduction of nitrate to ammonia by cobalt porphyrin. The bromine functional group modified at the meso position of cobalt porphyrin can reduce the electron cloud density of the cobalt porphyrin center, thereby improving the stability of cobalt porphyrin in the electrocatalytic reduction reaction, further improving the catalytic performance, and realizing the efficient reduction of nitrate in water to synthesize ammonia, thereby providing a green solution to energy and environmental problems. The pyridyl cation modified cobalt porphyrin catalyst prepared in the present application has a yield of 196.3 μmol / h / cm 2 for the electrocatalytic reduction of nitrate to ammonia at an optimal voltage of -1.4 V, and a Faraday efficiency of 90%, thereby having good electrocatalytic reduction activity for nitrate. BRIEF DESCRIPTION OF DRAWINGS
[0025] Figure 1 is a synthesis route diagram for preparing the pyridyl cation modified cobalt porphyrin in Example 1.
[0026] Figure 2 is a nuclear magnetic resonance spectrum of the pyridyl cation modified cobalt porphyrin ligand prepared in Example 1.
[0027] Figure 3 is a high-resolution mass spectrum of the pyridyl cation modified cobalt porphyrin prepared in Example 1.
[0028] Figure 4 is a performance curve of the pyridyl cation modified cobalt porphyrin prepared in Example 1 for linear sweep voltammetry (LSV) test in phosphate solution with and without sodium nitrate.
[0029] Figure 5 is a performance curve of the cobalt porphyrin prepared in Comparative Example 1 for linear sweep voltammetry (LSV) test in phosphate solution with and without sodium nitrate.
[0030] Figure 6 is a graph of the ammonia yield and Faraday efficiency of the pyridyl cation modified cobalt porphyrin prepared in Example 1 tested at different voltages.
[0031] Figure 7 is a graph of the ammonia yield and Faraday efficiency of the cobalt porphyrin prepared in Comparative Example 1 tested at different voltages.
[0032] Figure 8 is a stability graph of the electrocatalytic reduction of nitrate to ammonia by the pyridyl cation modified cobalt porphyrin prepared in Example 1.
[0033] Figure 9 is a stability graph of the electrocatalytic reduction of nitrate to ammonia by the cobalt porphyrin prepared in Comparative Example 1. DETAILED DESCRIPTION
[0034] In order to make the objectives, technical solutions and advantages of the present application clearer and more explicit, the present application will be further described in detail below with reference to the accompanying drawings and examples. It should be understood that the specific examples described herein are only used to explain the present application and do not limit the present application.
[0035] Electrocatalytic reduction of nitrate to ammonia is a green technology with double benefits, which can not only achieve efficient treatment of nitrate pollution in water bodies, but also convert waste nitrogen resources into high-value green ammonia, providing an innovative solution for the coordinated development of environmental governance and clean energy. The process of electrocatalytic reduction of nitrate to ammonia is complex, involving the adsorption of nitrate on the catalyst and the multi-step proton coupling electron transfer process, which leads to the problems of insufficient efficiency of electrocatalytic reduction of nitrate to ammonia and the generation of a large amount of by-products. In addition, the concentration of nitrate in water is often not high, which is not conducive to the adsorption of nitrate on the active sites of the catalyst, resulting in low ammonia production efficiency. Therefore, the core of the technology of reducing nitrate to ammonia lies in the development of efficient electrocatalysts. The inventors creatively proposed the design of pyridyl cation modified cobalt porphyrin for electrocatalytic reduction of nitrate. Metal porphyrin is a molecule with a clear M-N4 coordination configuration, which has a rigid structure and a stable coordination environment. The central metal can be stably combined with the reactant. By modifying the porphyrin ligand, the catalytic activity of metal porphyrin can be regulated. By taking advantage of the structural characteristics and easy modification of porphyrin, the adsorption group of nitrate is modified on the structure of the porphyrin ligand, thereby increasing the local concentration of nitrate at the catalytic center. In addition, the bromine functional group modified on the cobalt porphyrin can reduce the electron cloud density of the cobalt porphyrin center, improve the stability of the cobalt porphyrin in the electrocatalytic reduction reaction, and further improve the performance of the electrocatalytic reduction of nitrate to ammonia. In subsequent examples, the electrochemical performance test results show that under the concentration of 0.1M phosphate and 0.1M sodium nitrate, the ammonia production rate of the pyridyl cation modified cobalt porphyrin electrocatalyst of the present application is 196.3μmol / h / cm 2 , the faraday efficiency is 90%, and in the durability test of a total of 9 experimental cycles, the fluctuations of the faraday efficiency and the ammonia production rate are negligible, indicating that the pyridyl cation modified cobalt porphyrin electrocatalyst of the present application also performs well in the stability experiment.
[0036] In some embodiments of the present application, a pyridyl cation modified cobalt porphyrin catalyst is provided, which has the structure shown in formula (I):
[0037]
[0038] In some embodiments of the present application, a preparation method of a pyridyl cation modified cobalt porphyrin catalyst is provided, which comprises the following preparation steps:
[0039] (1) 2,2'-dipyrrylmethane and o-bromobenzaldehyde are dissolved in solvent A, after oxygen removal, trifluoroacetic acid is added, stirred uniformly, then 2,3-dichloro-5,6-dicyano-1,4-benzoquinone is added, stirred and reacted, after the reaction is completed, triethylamine is added to terminate the reaction, to obtain 5,15-di(2-benzylbromide)porphyrin ligand, the 5,15-di(2-benzylbromide)porphyrin ligand and zinc acetate are dissolved in solvent B, and the reaction is carried out in the dark to obtain a 5,15-di(2-benzylbromide)zinc porphyrin compound with a structure shown in formula (II);
[0040]
[0041] (2) The 5,15-di(2-benzylbromide)zinc porphyrin compound obtained in step (1) is dissolved in solvent C, oxygen is removed, N-bromosuccinimide is added, and the reaction is carried out to obtain a 5,15-dibromo-10,20-di(2-benzylbromide)zinc porphyrin compound with a structure shown in formula (III);
[0042]
[0043] (3) The 5,15-dibromo-10,20-di(2-benzylbromide)zinc porphyrin compound in step (2) is added to solvent D with pyridine, and the reaction is carried out in the dark to obtain a 5,15-dibromo-10,20-di(2-benzylpyridine)zinc porphyrin compound with a structure shown in formula (IV):
[0044]
[0045] (4) The 5,15-dibromo-10,20-di(2-benzylpyridine)zinc porphyrin in step (3) is dissolved in solvent E, concentrated hydrochloric acid is added, and the reaction is stirred, after the reaction is completed, to obtain 5,15-dibromo-10,20-di(2-benzylpyridine)porphyrin ligand, the prepared 5,15-dibromo-10,20-di(2-benzylpyridine)porphyrin ligand is dissolved in solvent F, and cobalt acetate is added to carry out a heating reaction, after the reaction is completed, to obtain the pyridyl cation modified cobalt porphyrin catalyst.
[0046] In some embodiments of the present application, in step (1), the molar ratio of 2,2'-dipyrromethane, o-bromobenzaldehyde, trifluoroacetic acid and 2,3-dichloro-5,6-dicyano-1,4-benzoquinone is 1-4: 1-4: 4-12: 1-6, preferably 1.5-2.5: 1.5-2.5: 7-9: 2-4; the molar ratio of 5,15-di(2-benzylbromide) porphyrin ligand and zinc acetate is 0.02-0.1: 0.2-1.5, preferably 0.04-0.06: 0.4-0.6; the stirring reaction time is 0.3-1.5h, preferably 0.3-0.8h; the temperature of the light-protected reaction is 60-80℃, and the time is 1-5h, preferably the temperature is 65-76℃, and the time is preferably 2-4h.
[0047] In some embodiments of the present application, in step (2), the molar ratio of 5,15-di(2-benzylbromide) zinc porphyrin compound and N-bromosuccinimide is 0.02-0.1: 0.04-0.2, preferably 0.04-0.06: 0.08-0.12, and the reaction time is 0.3-1.5h, preferably 0.3-0.8h.
[0048] In some embodiments of the present application, in step (3), the molar ratio of 5,15-dibromo-10,20-di(2-benzylbromide) zinc porphyrin and pyridine is 0.02-1.5: 0.1-0.4, preferably 0.04-0.06: 0.1-0.3, the temperature of the light-protected reaction is 60-80℃, preferably 65-75℃, and the time is 1-5h, preferably 2-4h.
[0049] In some embodiments of the present application, the reaction products in steps (1), (2) and (3) are all purified by column chromatography.
[0050] In some embodiments of the present application, in step (4), the molar volume ratio of 5,15-dibromo-10,20-di(2-benzylpyridine) zinc porphyrin and concentrated hydrochloric acid is 0.02-0.1 mmol: 1-5 mL, preferably 0.04-0.06 mmol: 1-3 mL, the stirring reaction time is 1-5 hours, preferably 1-3 hours; the molar ratio of 5,15-dibromo-10,20-di(2-benzylpyridine) porphyrin ligand and cobalt acetate is 0.02-0.1: 0.1-1.0, preferably 0.03-0.05: 0.4-0.6, the temperature of the heating reaction is 50-75℃, preferably 60-70℃, and the reaction time is 1-5 hours, preferably 1-3 hours.
[0051] In some embodiments of the present application, the reaction product in step (4) is extracted with water and dichloromethane, the organic phase is collected, and then subjected to reduced pressure distillation.
[0052] In some embodiments of the present application, solvent A is selected from dichloromethane, solvent B is selected from tetrahydrofuran, solvent C is selected from chloroform, solvent D is selected from chloroform, solvent E is selected from acetone, solvent F is selected from a mixture of trichloromethane and methanol.
[0053] In some embodiments of the present application, the use of a pyridyl cation modified cobalt porphyrin catalyst in the electrocatalytic reduction of nitrate salt, the electrode loaded with said catalyst and carbon material is used as the cathode working electrode, the carbon rod is used as the anode, and the solution including sodium nitrate is used as the electrolyte. Preferably, the solution including sodium phosphate buffer salt and sodium nitrate is used as the electrolyte.
[0054] The following will be described in detail in combination with specific examples and comparative examples. The raw materials of the examples and comparative examples of the present application are all sourced from the market unless otherwise specified, and the raw materials or reagents used are all of analytical purity.
[0055] Example 1
[0056] This example provides a pyridyl cation modified cobalt porphyrin and a preparation method and application, and the synthetic route is as shown in Figure 1 The specific preparation steps are as follows:
[0057] Step (1): 396 mg (2 mmol) of 2,2'-dipyrrylmethane and 292 mg (2 mmol) of o-bromobenzaldehyde were dissolved in 500 mL of dichloromethane (CAS number: 75-09-2), 0.594 mL (8 mmol) of trifluoroacetic acid was added after oxygen removal, and stirred for 0.5 hours (400 rpm). Then 681 mg (3 mmol) of 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ) was added, and the reaction was stirred for 0.5 hours (400 rpm), 1 mL of triethylamine was added to terminate the reaction, and the product was separated and purified by column chromatography to obtain a 5,15-di(2-benzylbromide) porphyrin ligand. 32.3 mg (0.05 mmol) of 5,15-di(2-benzylbromide) porphyrin ligand and 109.8 mg (0.5 mmol) of zinc acetate tetrahydrate (Zn(OAc)2·4H2O) were dissolved in 20 mL of tetrahydrofuran, and the reaction was carried out at 70°C for 3 hours in the dark. After the product was separated and purified by column chromatography, a 5,15-di(2-benzylbromide) zinc porphyrin compound was obtained.
[0058] Step (2): 35.6 mg (0.05 mmol) of 5,15-di(2-benzylbromide) zinc porphyrin was dissolved in freshly distilled chloroform, oxygen was removed, and 18.16 mg (0.102 mmol) of N-bromosuccinimide was added at 0°C. After the reaction for 0.5 hours, the product was separated and purified by column chromatography to obtain a 5,15-dibromo-10,20-di(2-benzylbromide) zinc porphyrin compound.
[0059] Step (3): 43.2 mg (0.05 mmol) of 5, 15-dibromo-10, 20-di(2-benzyl bromide) zinc porphyrin and 15.82 mL (0.2 mmol) of pyridine were added to 100 mL of chloroform solvent, and reacted at 70°C for 3 hours in the dark. After separation and purification by column chromatography, 5, 15-dibromo-10, 20-di(2-benzyl pyridine) zinc porphyrin compound was obtained.
[0060] Step (4): 43.2 mg (0.05 mmol) of 5, 15-dibromo-10, 20-di(2-benzyl pyridine) zinc porphyrin was dissolved in 25 mL of acetone, 2 mL of concentrated hydrochloric acid (concentration 36% ~ 38%) was added, and the reaction was stirred at room temperature (25°C) for 2 hours (400 rpm). After extraction with water and dichloromethane (1:1), the organic phase was collected and distilled under reduced pressure to obtain 5, 15-dibromo-10, 20-di(2-benzyl pyridine) porphyrin ligand. 42.95 mg (0.05 mmol) of 5, 15-dibromo-10, 20-di(2-benzyl pyridine) porphyrin ligand was dissolved in a mixed solution of 30 mL of chloroform and methanol (10:1), 124.5 mg (0.5 mmol) of cobalt acetate tetrahydrate (Co(OAc)2·4H2O) was added, and the reaction was carried out at 65°C for 3 hours. After removing the solvent under reduced pressure, extraction was performed with water and dichloromethane, and the organic phase was collected. After removing the solvent under reduced pressure, 5, 15-dibromo-10, 20-di(2-benzyl pyridine) cobalt porphyrin was obtained, which is a pyridyl cation modified cobalt porphyrin.
[0061] Since the pyridyl cation modified cobalt porphyrin cannot obtain nuclear magnetic resonance spectrum, the pyridyl cation modified cobalt porphyrin ligand (the ligand compound does not contain the central metal Co) was selected as the object of nuclear magnetic detection to characterize the structure of the compound. Figure 2 The nuclear magnetic resonance spectrum of 5, 15-dibromo-10, 20-di(2-benzyl pyridine) porphyrin ligand prepared in Example 1, the peaks at -2.81 and -2.91 ppm are the hydrogen on the N-H of the pyrrole ring (2H), the peaks at 5.33-5.47 ppm are the hydrogen on the methylene group (4H), the peaks at 7.22-6.68 ppm are the hydrogen on the benzene ring (8H), the peaks at 7.76-8.23 ppm are the hydrogen on the pyridine (10H), and the peaks at 8.45 and 9.50 ppm are the β-hydrogen on the pyrrole ring (8H), which proves that the structure of the pyridyl cation modified cobalt porphyrin ligand is correct. Figure 3 The high resolution mass spectrum of the pyridyl cation modified cobalt porphyrin prepared in Example 1. From Figure 3 It can be seen that the chemical formula of the compound is C 44 H 30 Br2CoN6 2+The high-resolution mass spectrum actually measured 430.5104, and the theoretical value was 430.5102, the test results were consistent with the target compound, which proved that the pyridyl cation modified cobalt porphyrin was successfully prepared in Example 1.
[0062] Comparative Example 1
[0063] Comparative Example 1 synthesizes tetraphenyl cobalt porphyrin according to the reported method (Qin H., et al., “Cobalt porphyrins supported on carbon nanotubes as model catalysts of metal-N4 / C sites for oxygen electrocatalysis”, Journal of Energy Chemistry, 2021, 53, 77-81), including the following steps: mixing 7.5 mL (0.0647 mol) of benzaldehyde and 200 mL (0.267 mol) of propionic acid, heating to reflux. Freshly distilled 5.0 mL (0.0722 mol) of pyrrole is added dropwise to the refluxing system, which is added within 0.5 hours, and the reflux reaction is continued for 0.5 hours. After the reaction is cooled to room temperature, it is placed in the refrigerator to crystallize, and after filtration, column chromatography is used to separate and purify to obtain the tetraphenyl porphyrin ligand. 0.307 g (0.5 mmol) of tetraphenyl porphyrin ligand and 0.65 g (5 mmol) of cobalt chloride are dissolved in a 50 mL volume of N,N-dimethylformamide solution, and reacted at 120°C for 6 hours. After the reaction is completed, distilled water is added to the resulting mixture, and the product is extracted with chloroform, and the extract is dried with anhydrous MgSO4, and after column chromatography separation and purification, tetraphenyl cobalt porphyrin is obtained.
[0064] In the test of reducing nitrate in water to ammonia by electrocatalysis, the cathode uses the catalyst obtained from Example 1 or Comparative Example 1 mixed with graphene (purity > 98%, thickness about 1 nm, flake diameter 0.2-10 μm) (mass ratio 1:1), and 5wt% nafion is added as a binder. 60 μL of the above mixed solution is coated on an area of 0.25 cm 2 on carbon paper, and the anode uses a carbon rod, and the electrolyte is a mixed solution of 0.1M phosphate buffer solution and 0.1M sodium nitrate. The pyridyl cation modified cobalt porphyrin electrocatalyst prepared in Example 1 is tested for electrocatalytic activity in 0.1M phosphate buffer solution with and without 0.1M sodium nitrate by linear sweep voltammetry, and the results are shown in Figure 4 From Figure 4 it can be seen that the catalytic current density is significantly higher in the presence of nitrate, reaching 67 mA / cm 2 at a voltage of-1.6V, while in the absence of nitrate, the catalytic current density is only 27 mA / cm2 This indicates that the pyridyl cationic modified cobalt porphyrin exhibits excellent electrocatalytic activity for the reduction of nitrate in water. Figure 5 The electrocatalytic activity of the tetraphenylcobalt porphyrin prepared for Comparative Example 1 was tested in 0.1 M phosphate buffer solutions containing and without 0.1 M sodium nitrate. Although tetraphenylcobalt porphyrin also showed catalytic nitrate reduction ability, the highest catalytic current density of tetraphenylcobalt porphyrin in the presence of nitrate was only 45 mA / cm². 2 Compared to cobalt porphyrin modified with pyridyl cationic groups, the catalytic current density decreased by nearly 33%, indicating that cobalt porphyrin without positively charged cationic groups has significantly insufficient catalytic activity in nitrate reduction. These conclusions demonstrate that by designing pyridyl cationic groups, the local nitrate concentration in cobalt porphyrin can be increased, which can significantly enhance the electrocatalytic nitrate reduction activity of cobalt porphyrin in water. Figure 6 The figures represent the ammonia yield and Faradaic efficiency of pyridyl cationic modified cobalt porphyrin for reducing nitrate at different voltages. From -1.0 V to -1.6 V, the ammonia yield gradually increases with increasing catalytic current density, reaching 48, 67, 88, 141, 196, 234, and 294 μmol / h / cm², respectively. 2 Regarding the Faraday efficiency, it shows a trend of first increasing and then decreasing from the voltage range of -1.0V to -1.6V, with values of 61%, 75%, 83%, 82%, 90%, 79%, and 72%, respectively. At the optimal reduction voltage of -1.4V, the Faraday efficiency reaches as high as 90%, indicating that nitrates in water can be effectively reduced to ammonia. Figure 7 The figures show the ammonia yield and Faradaic efficiency of tetraphenylcobalt porphyrin in Comparative Example 1 at different voltages for reducing nitrate. The highest Faradaic efficiency was 71%, while the highest ammonia yield was only 110 μmol / h / cm³. 2 Therefore, pyridyl cationic modified cobalt porphyrin exhibits superior electrocatalytic activity compared to tetraphenylcobalt porphyrin in reducing nitrates in water to ammonia.
[0065] like Figure 8 and Figure 9 As shown, continuous electrolysis experiments were conducted on the pyridyl cationic modified cobalt porphyrin of Example 1 and the tetraphenylcobalt porphyrin of Comparative Example 1 at the optimal voltage (-1.4V) to study their stability in the electrocatalytic reduction of nitrate. In nine cycles, the pyridyl cationic modified cobalt porphyrin maintained high activity for the catalytic reduction of nitrate, with only slight fluctuations in Faradaic efficiency and ammonia yield. Comparing the activities before and after cycling, the ammonia yield and Faradaic efficiency remained at 95% and 96%, respectively, indicating that the pyridyl cationic modified cobalt porphyrin prepared in Example 1 improved the stability of cobalt porphyrin in the electrocatalytic reduction of nitrate. In contrast, the tetraphenylcobalt porphyrin showed poor stability in the catalytic reduction of nitrate; after nine cycles, the ammonia yield decreased significantly, remaining at only 45%.
[0066] In summary, the pyridyl cation modified cobalt porphyrin exhibits high catalytic performance and good stability in the electrocatalytic reduction of nitrate to ammonia in water.
[0067] The above merely describes preferred embodiments of the present application and is not intended to limit the scope of the present application. It should be pointed out that, for other researchers in the art, other corresponding modifications and changes can be made according to the technical solutions and concepts described above, and all the other corresponding modifications and changes should be within the protection scope of the claims of the present application.
Claims
1. A pyridinium-modified cobalt porphyrin catalyst characterized in that, The catalyst has a structure shown in formula (I):
2. A method of preparing the pyridinium-modified cobalt porphyrin catalyst of claim 1, characterized by, The preparation steps include: (1) 2,2'-dipyrrylmethane and o-bromobenzaldehyde are dissolved in solvent A, after oxygen is removed, trifluoroacetic acid is added, stirred uniformly, then 2,3-dichloro-5,6-dicyano-1,4-benzoquinone is added, stirred to react, after the reaction is completed, triethylamine is added to terminate the reaction, 5,15-di(2-benzylbromide) porphyrin ligand is obtained, 5,15-di(2-benzylbromide) porphyrin ligand and zinc acetate are dissolved in solvent B, and light-proof reaction is carried out, so that 5,15-di(2-benzylbromide) zinc porphyrin compound with a structure shown in formula (II) is obtained; (2) 5,15-di(2-benzylbromide) zinc porphyrin compound obtained in step (1) is dissolved in solvent C, oxygen is removed, N-bromosuccinimide is added, and reaction is carried out, so that 5,15-dibromo-10,20-di(2-benzylbromide) zinc porphyrin compound with a structure shown in formula (III) is obtained; (3) 5,15-dibromo-10,20-di(2-benzylbromide) zinc porphyrin compound in step (2) and pyridine are added to solvent D, and light-proof reaction is carried out, so that 5,15-dibromo-10,20-di(2-benzylpyridine) zinc porphyrin compound with a structure shown in formula (IV) is obtained: (4) 5,15-dibromo-10,20-di(2-benzylpyridine) zinc porphyrin in step (3) is dissolved in solvent E, concentrated hydrochloric acid is added, and stirring reaction is carried out, after the reaction is completed, 5,15-dibromo-10,20-di(2-benzylpyridine) porphyrin ligand is obtained, and the prepared 5,15-dibromo-10,20-di(2-benzylpyridine) porphyrin ligand is dissolved in solvent F, and cobalt acetate is added to carry out heating reaction, after the reaction is completed, the pyridyl cation modified cobalt porphyrin catalyst is obtained.
3. The method of claim 2, wherein the pyridinium-modified cobalt porphyrin catalyst is prepared by the steps of: (a) mixing a cobalt porphyrin with a pyridinium salt to form a mixture; (b) adding a base to the mixture; and (c) isolating the pyridinium-modified cobalt porphyrin catalyst. In step (1), the molar ratio of 2,2'-dipyrrylmethane, o-bromobenzaldehyde, trifluoroacetic acid and 2,3-dichloro-5,6-dicyano-1,4-benzoquinone is 1-4:1-4:4-12:1-6; the molar ratio of 5,15-di(2-benzylbromide) porphyrin ligand and zinc acetate is 0.02-0.1:0.2-1.5; the stirring reaction time is 0.3-1.5 h, and the light-proof reaction temperature is 60-80 DEG C, and the time is 1-5 h.
4. The method of claim 2, wherein the pyridinium-modified cobalt porphyrin catalyst is prepared by the steps of: (a) mixing a cobalt porphyrin with a pyridinium salt to form a mixture; (b) adding a base to the mixture; and (c) isolating the pyridinium-modified cobalt porphyrin catalyst. In step (2), the molar ratio of 5,15-di(2-benzylbromide) zinc porphyrin compound and N-bromosuccinimide is 0.02-0.1:0.04-0.2, and the reaction time is 0.3-1.5 h.
5. The method of claim 2, wherein the pyridinium-modified cobalt porphyrin catalyst is prepared by the steps of: (a) mixing a cobalt porphyrin with a pyridinium salt to form a mixture; (b) adding a base to the mixture; and (c) isolating the pyridinium-modified cobalt porphyrin catalyst. In step (3), the molar ratio of 5,15-dibromo-10,20-di(2-benzylbromide) zinc porphyrin and pyridine is 0.02-1.5:0.1-0.4, the light-proof reaction temperature is 60-80 DEG C, and the time is 1-5 h.
6. The method of claim 2, wherein the pyridinium-modified cobalt porphyrin catalyst is prepared by the steps of: (a) mixing a cobalt porphyrin with a pyridinium salt to form a mixture; (b) adding a base to the mixture; and (c) isolating the pyridinium-modified cobalt porphyrin catalyst. The reaction products in steps (1), (2) and (3) are all purified by column chromatography.
7. The method of claim 2, wherein the pyridinium-modified cobalt porphyrin catalyst is prepared by the steps of: (a) mixing a cobalt porphyrin with a pyridinium salt to form a mixture; (b) adding a base to the mixture; and (c) isolating the pyridinium-modified cobalt porphyrin catalyst. In step (4), the molar volume ratio of 5,15-dibromo-10,20-di(2-benzylpyridine) zinc porphyrin and concentrated hydrochloric acid is 0.02-0.1 mmol:1-5 mL, the stirring reaction time is 1-5 hours; the molar ratio of 5,15-dibromo-10,20-di(2-benzylpyridine) porphyrin ligand and cobalt acetate is 0.02-0.1:0.1-1.0, the heating reaction temperature is 50-75°C, and the reaction time is 1-5 hours.
8. The method of claim 2, wherein the pyridinium-modified cobalt porphyrin catalyst is prepared by the steps of: (a) mixing a cobalt porphyrin with a pyridinium salt to form a mixture; (b) adding a base to the mixture; and (c) isolating the pyridinium-modified cobalt porphyrin catalyst. The reaction product in step (4) is extracted with water and dichloromethane, the organic phase is collected, and is subjected to reduced pressure distillation.
9. Use of the pyridyl cation modified cobalt porphyrin catalyst of claim 1 in electrocatalytic nitrate reduction reaction.
10. Use of the pyridinium-modified cobalt porphyrin catalyst according to claim 9 for the electrocatalytic reduction of nitrate, characterized in that, In the electrocatalytic nitrate reduction reaction, an electrode loaded with the catalyst and carbon material is used as the cathode, a carbon rod is used as the anode, and a solution including sodium nitrate is used as the electrolyte.