Benzimidazole modified nickel phthalocyanine catalyst as well as preparation method and application thereof

Abstract

The invention discloses a benzimidazole modified nickel phthalocyanine catalyst and a preparation method and application thereof.The preparation method of the benzimidazole modified nickel phthalocyanine catalyst comprises the following steps that benzimidazole modified nickel phthalocyanine is dissolved in a second solvent to obtain a nickel phthalocyanine solution, carbon nano tubes are dispersed in a third solvent to obtain a carbon nano tube solution, and the carbon nano tube solution is added into the second solvent to obtain the benzimidazole modified nickel phthalocyanine catalyst. A nickel phthalocyanine solution and a carbon nanotube solution are mixed, subjected to ultrasonic treatment, stirred, subjected to suction filtration, washed and freeze-dried, the benzimidazole modified nickel phthalocyanine catalyst is obtained, the carbon monoxide Faraday efficiency of the benzimidazole modified nickel phthalocyanine catalyst reaches 94% or above, the highest carbon monoxide Faraday efficiency can reach 98%, and under the acidic condition, the carbon monoxide Faraday efficiency of the benzimidazole modified nickel phthalocyanine catalyst can reach 98% or above. The hydrogen evolution reaction generated in a system can be effectively inhibited, the hydrogen Faraday efficiency is controlled to be 7% or below within a wide voltage range, and excellent product selectivity is achieved.

Description

Technical Field

[0001] The invention belongs to the technical field of environmental functional materials and electrochemical technology, and specifically relates to a benzimidazole-modified nickel phthalocyanine catalyst and a preparation method and application thereof. Background Art

[0002] Since the Industrial Revolution in the 19th century, the overuse of fossil fuels (such as oil, coal and natural gas) has caused a series of problems. On the one hand, due to the continuous growth of population and the rapid development of science and technology, human beings have an increasing demand for fossil fuels. However, fossil fuels are non-renewable energy and have limited reserves, which has led to an intensification of the energy crisis. On the other hand, due to the continuous use of fossil fuels, a large amount of CO2 is emitted into the atmosphere, which has led to the intensification of global warming. The electro-reduction of CO2 to sustainable fuels or high-value-added chemicals (such as carbon monoxide, methane, ethanol and ethylene, etc.) is a promising strategy. Among the chemicals generated by the electrocatalytic reduction of CO2, CO is a promising industrial raw material and plays a key role in many industrial processes.

[0003] The nickel phthalocyanine catalyst formed by metal phthalocyanine loaded on the surface of carbon nanotubes is often used for the electrocatalytic reduction of CO2, and has excellent performance. In particular, the nickel phthalocyanine catalyst has excellent product selectivity and current density in the catalytic process. However, the nickel phthalocyanine is generally used in the process of electrocatalytic reduction of CO2 under neutral or weak alkaline conditions, and refractory carbonates are formed during the reaction, which will cause the active sites on the surface of the nickel phthalocyanine catalyst to be covered, thereby affecting the stability and catalytic efficiency of the nickel phthalocyanine catalyst. Summary of the invention

[0004] In view of the deficiencies of the prior art, the object of the present invention is to provide a benzimidazole-modified nickel phthalocyanine.

[0005] Another object of the present invention is to provide a method for preparing benzimidazole-modified nickel phthalocyanine, wherein the method utilizes an imidazole group containing a basic functional group to modify ordinary nickel phthalocyanine to obtain benzimidazole-modified nickel phthalocyanine.

[0006] Another object of the present invention is to provide a method for preparing a benzimidazole-modified nickel phthalocyanine catalyst.

[0007] Another object of the present invention is to provide an application of a benzimidazole-modified nickel phthalocyanine catalyst in electrocatalysis of CO2, wherein the benzimidazole-modified nickel phthalocyanine catalyst can inhibit the occurrence of hydrogen evolution reaction in electrocatalysis of CO2 under acidic conditions, and can also optimize the current density of the central active metal, promote the overflow and transfer of electrons, and further improve the catalytic conversion rate of CO2.

[0008] The purpose of the present invention is achieved through the following technical solutions.

[0009] A benzimidazole-modified nickel phthalocyanine, the structural formula of which is as follows:

[0010]

[0011] A method for preparing benzimidazole-modified nickel phthalocyanine comprises the following steps:

[0012] Step 1, dissolving 4-nitrophthalonitrile in anhydrous DMF, adding 2-mercaptobenzimidazole under a nitrogen atmosphere, stirring at 50-60° C. for 20-30 minutes, adding anhydrous potassium carbonate several times, reacting at 50-55° C. for 72-84 hours under stirring, and obtaining a mixture after the reaction is completed. The mixture is poured into ice water and stirred, and allowed to stand for at least 12 hours, filtered, washed, and freeze-dried to obtain 4-{[1H-benzo(d)imidazol-2-yl]thiol}phthalonitrile, wherein the ratio of 4-nitrophthalonitrile to 2-mercaptobenzimidazole is (1-2):(1-2) by mass;

[0013] In the step 1, the mass fraction of the 4-nitrophthalonitrile, the mass fraction of anhydrous potassium carbonate and the volume fraction of anhydrous DMF is (1-2): (4-8): (35-40), the unit of the mass fraction is g, and the unit of the volume fraction is mL.

[0014] In the step 1, the operation of adding anhydrous potassium carbonate in multiple times includes: adding the anhydrous potassium carbonate in 6 to 8 times within 2 to 3 hours.

[0015] In the step 1, the mixture is poured into ice water and stirred for 1 to 2 hours.

[0016] In the step 1, the standing time is 12 to 16 hours.

[0017] In step 1, the washing operation includes: washing the filtered solid with water until the filtrate is neutral, and then washing with methanol for 3 to 5 times.

[0018] Step 2, under a nitrogen atmosphere, 4-{[1H-benzo(d)imidazol-2-yl]thiol}phthalonitrile, anhydrous NiCl2 and 1.8 diazabicyclo[5.4.0]undec-7-ene (DBU) are dispersed in ultra-dry n-pentanol, and refluxed at 70-90° C. for 20-24 hours under stirring. After the reaction is completed, a reaction solution is obtained, which is cooled to room temperature, diluted with a first solvent to produce a solid precipitate, filtered, and washed. Freeze-drying to obtain benzimidazole-modified nickel phthalocyanine, wherein the mass fraction of 4-{[1H-benzo(d)imidazol-2-yl]thiol}phthalonitrile, the mass fraction of anhydrous NiCl2 and the volume fraction ratio of 1.8diazabicyclo[5.4.0]undec-7-ene is (0.2-0.3):(0.1-0.2):(0.5-0.6), the unit of the mass fraction is g, and the unit of the volume fraction is mL.

[0019] In step 2, the first solvent is methanol.

[0020] In the step 2, the ratio of the mass fraction of anhydrous NiCl2, the volume fraction of ultra-dry n-pentanol and the volume fraction of the first solvent is (0.1-0.2):(20-30):(100-150), the unit of the mass fraction is g, and the unit of the volume fraction is mL.

[0021] In step 2, washing includes: washing with n-hexane, methanol, ethanol and water in sequence for 1 to 2 times each.

[0022] In step 1 and step 2, the freeze-drying temperature is -80 to -50°C, and the freeze-drying time is 36 to 48 hours.

[0023] A method for preparing a benzimidazole-modified nickel phthalocyanine catalyst comprises the following steps:

[0024] The above-mentioned benzimidazole-modified nickel phthalocyanine is dissolved in a second solvent to obtain a nickel phthalocyanine solution, and carbon nanotubes are dispersed in a third solvent by ultrasound to obtain a carbon nanotube solution. The nickel phthalocyanine solution and the carbon nanotube solution are mixed, ultrasound-treated, stirred for 12 to 24 hours, filtered, washed, and freeze-dried to obtain a benzimidazole-modified nickel phthalocyanine catalyst, wherein the ratio of the benzimidazole-modified nickel phthalocyanine to the carbon nanotubes is (0.003 to 0.004): (0.03 to 0.04) by mass.

[0025] In the above technical solution, the second solvent is DMF, and the third solvent is DMF.

[0026] In the above technical solution, the mass fraction of benzimidazole-modified nickel phthalocyanine, the volume fraction of the second solvent and the volume fraction of the third solvent are (0.003-0.004):(30-40):(20-30), the unit of the mass fraction is g, and the unit of the volume fraction is mL.

[0027] In the above technical solution, the frequency of the ultrasound is 80 to 100 Hz, and the time of the ultrasound is 1 to 2 hours.

[0028] In the preparation method of the benzimidazole-modified nickel phthalocyanine catalyst, washing includes washing with DMF, ethanol and water in sequence for 1 to 2 times respectively.

[0029] In the above technical solution, the freeze-drying temperature is -80 to -50°C, and the freeze-drying time is 36 to 48 hours.

[0030] Application of the above-mentioned benzimidazole-modified nickel phthalocyanine catalyst in electrocatalysis of CO2.

[0031] In the above technical solution, the pH of the electrocatalytic electrolyte is less than 8, preferably less than 7.2, and more preferably acidic.

[0032] Compared with the prior art, the present invention has the following beneficial effects:

[0033] (1) The benzimidazole-modified nickel phthalocyanine catalyst of the present invention has high current density and high binding energy, which is beneficial to electron transport and has better catalytic activity.

[0034] (2) The benzimidazole-modified nickel phthalocyanine catalyst of the present invention has a carbon monoxide Faraday efficiency of more than 94% at a voltage of -1.20 to -1.00 V (vs. RHE) and an electrolyte pH of 1.85, and can reach a maximum of 98%. Under acidic conditions, it can effectively inhibit the occurrence of hydrogen evolution reaction in the system. Within a wide voltage range, its hydrogen Faraday efficiency is controlled below 7%, and it has excellent product selectivity, which provides new insights for electrocatalytic CO2 reduction in actual acidic environments. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 Co2p diagrams of the benzimidazole-modified nickel phthalocyanine catalyst prepared in Example 2 and the nickel phthalocyanine catalyst prepared in Comparative Example 1;

[0036] Figure 2 (a) is a transmission electron microscope (TEM) image and (b-e) are energy dispersive X-ray scanning spectra of the benzimidazole-modified nickel phthalocyanine catalyst prepared in Example 2, wherein (b) is the C element, (c) is the N element, (d) is the Ni element, and (e) is the S element;

[0037] Figure 3 (a) is a TEM image and (b-d) are energy dispersive X-ray scanning spectra of the nickel phthalocyanine catalyst prepared in Comparative Example 1, wherein (b) is the C element, (c) is the N element, and (d) is the Ni element;

[0038] Figure 4 The linear voltammetric scanning diagram of the H-type electrolytic cell using the benzimidazole-modified nickel phthalocyanine catalyst prepared in Example 2 and the nickel phthalocyanine catalyst prepared in Comparative Example 1;

[0039] Figure 5 The cyclic voltammograms of the H-type electrolytic cell using the benzimidazole-modified nickel phthalocyanine catalyst prepared in Example 2 and the nickel phthalocyanine catalyst prepared in Comparative Example 1;

[0040] Figure 6 The impedance diagram (EIS) of an H-type electrolytic cell using the benzimidazole-modified nickel phthalocyanine catalyst prepared in Example 2 and the nickel phthalocyanine catalyst prepared in Comparative Example 1;

[0041] Figure 7 (a) CO Faraday efficiency (FE) of the H-type electrolytic cell using the benzimidazole-modified nickel phthalocyanine catalyst prepared in Example 2 and the nickel phthalocyanine catalyst prepared in Comparative Example 1 at an electrolyte pH of 1.85 CO ) and (b) hydrogen Faraday efficiency (FE H2 )picture;

[0042] Figure 8 The current density and the Faraday efficiency (FE) of carbon monoxide in the H-type electrolytic cell using the benzimidazole-modified nickel phthalocyanine catalyst prepared in Example 2 at an electrolyte pH of 1.85 for 20 hours CO )picture;

[0043] Fig. 9 (a) CO Faraday efficiency (FE) of the H-type electrolytic cell using the benzimidazole-modified nickel phthalocyanine catalyst prepared in Example 2 under different electrolytes CO ) and (b) hydrogen Faraday efficiency (FE H2 )picture;

[0044] Fig.10 (a) CO Faraday efficiency (FE) of the H-type electrolytic cell using the benzimidazole-modified nickel phthalocyanine catalyst prepared in Example 2 and the nickel phthalocyanine catalyst prepared in Comparative Example 1 at an electrolyte pH of 7.2 CO ) and (b) hydrogen Faraday efficiency (FE H2 )picture;

[0045] Fig.11 Fourier transform infrared (FT-IR) spectra of the benzimidazole-modified nickel phthalocyanine prepared in Example 1 and the nickel phthalocyanine in Comparative Example 1. DETAILED DESCRIPTION

[0046] The technical solution of the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments.

[0047] The following drugs were purchased from:

[0048] 4-Nitrophthalonitrile, 2-mercaptobenzimidazole and 1,8-diazabicyclo[5.4.0]undec-7-ene were purchased from Shanghai MacLean Biochemical Technology Co., Ltd.

[0049] In the following examples, an X-ray photoelectron spectrometer (manufacturer: Thermo Fisher Scientific K-Alpha) was used to measure the XPS spectra. The test conditions of the X-ray photoelectron spectrometer are as follows: the vacuum degree of the analysis chamber is 5×10 -10 Pa, the excitation source is Al-ka ray (hv=1486.68eV), the working voltage is 15kV, the filament current is 10mA, and the signal accumulation is performed 5-10 times. The test pass energy is 50eV, the step size is 0.05eV, and the charging correction uses C1s=284.80eV binding energy as the energy standard.

[0050] In the following examples, a transmission electron microscope (TEM, model: FEI-Tecnai G2 F20 S-Twin) was used to analyze the microscopic morphology at an accelerating voltage of 200 kV to obtain a transmission electron microscope (TEM) image.

[0051] In the following examples, nafion membrane solution (model: D520) was purchased from DuPont.

[0052] In the following examples, the method for preparing the working electrode includes: placing 2 mg of catalyst, 1990 uL of ethanol and 10 uL of nafion membrane solution in a 2 mL centrifuge tube, ultrasonicating for 1 hour to obtain an ink-like mixed solution, and evenly dropping 300 uL of the mixed solution on a 1 cm 2 The two sides of the carbon cloth were dried in an oven at 60°C for 5 minutes, and the carbon cloth with the mixed solution dropwise coated on both sides was fixed with a platinum electrode clamp to obtain a working electrode, wherein the catalyst was the benzimidazole-modified nickel phthalocyanine catalyst prepared in Example 2 or the nickel phthalocyanine catalyst prepared in Comparative Example 1.

[0053] In the following embodiments, the H-type electrolytic cell comprises: a working electrode, a reference electrode and a counter electrode, the electrolyte is one of a KCl-HCl mixed solution (pH = 1.85), a K2SO4-H2SO4 mixed solution (pH = 2.19) and a KHCO3 aqueous solution (pH = 7.2), the KCl-HCl mixed solution is a mixture of KCl, HCl and water, the concentration of KCl in the KCl-HCl mixed solution is 0.5M, and the concentration of HCl in the KCl-HCl mixed solution is 0.01M; the K2SO4-H2SO4 mixed solution It is a mixture of K2SO4, H2SO4 and water, the concentration of K2SO4 in the K2SO4-H2SO4 mixed solution is 0.5M, and the concentration of H2SO4 in the K2SO4-H2SO4 mixed solution is 0.01M; the KHCO3 aqueous solution is a mixture of KHCO3 and water, the concentration of KHCO3 in the KHCO3 aqueous solution is 0.5M, the catalyst in the working electrode is the benzimidazole-modified nickel phthalocyanine catalyst prepared in Example 2 or the nickel phthalocyanine catalyst prepared in Comparative Example 1, the reference electrode is a saturated calomel electrode, and the counter electrode is a graphite electrode.

[0054] Example 1

[0055] A method for preparing benzimidazole-modified nickel phthalocyanine comprises the following steps:

[0056]

[0057] Step 1, 4-nitrophthalonitrile (1.73 g, 0.01 mol) was dissolved in anhydrous DMF (35 mL), 2-mercaptobenzimidazole (1.50 g, 0.01 mol) was added under nitrogen atmosphere, and the mixture was stirred at 50° C. for 20 minutes, and anhydrous potassium carbonate (4.14 g, 0.03 mol) was added in 8 portions within 2 hours. The mixture was reacted at 50° C. for 72 hours under stirring. After the reaction was completed, a mixture was obtained, and the mixture was poured into ice water and stirred for 2 hours, and allowed to stand for 12 hours. A gray solid was collected by filtration, and the gray solid was rinsed with water until the filtrate was neutral, and then washed with methanol 3 times, and freeze-dried at -80° C. for 48 hours to obtain 4-{[1H-benzo(d)imidazol-2-yl]thiol}phthalonitrile;

[0058] Step 2, under a nitrogen atmosphere, 4-{[1H-benzo(d)imidazol-2-yl]thiol}phthalonitrile (0.221 g, 0.8 mmol), anhydrous NiCl2 (0.104 g, 0.8 mmol) and 1.8 diazabicyclo[5.4.0]undec-7-ene (0.5 mL) were dispersed in ultra-dry n-pentanol (20 mL), and refluxed at 80° C. for 24 hours under stirring. After the reaction, a dark green reaction solution was obtained, which was cooled to room temperature and diluted with methanol (100 mL) to allow a solid precipitate to appear in the reaction solution. The solution was filtered, and the solid precipitate was washed twice with n-hexane, methanol, ethanol and water respectively, and freeze-dried at -80° C. for 48 hours to obtain benzimidazole-modified nickel phthalocyanine (code: im-Nipc).

[0059] Example 2

[0060] A method for preparing a benzimidazole-modified nickel phthalocyanine catalyst comprises the following steps:

[0061] The benzimidazole-modified nickel phthalocyanine (0.003 g) prepared in Example 1 was dissolved in DMF (30 mL, the second solvent) to obtain a nickel phthalocyanine solution;

[0062] Carbon nanotubes (0.03 g) were dispersed in another portion of DMF (30 mL, the third solvent) by ultrasonication at a frequency of 100 Hz for 1 hour to obtain a carbon nanotube solution.

[0063] The nickel phthalocyanine solution and the carbon nanotube solution were mixed and ultrasonicated at a frequency of 100 Hz for 1 hour, stirred for 12 hours after ultrasonication, filtered, washed with DMF, ethanol and water twice respectively, and freeze-dried at -80°C for 48 hours to obtain a benzimidazole-modified nickel phthalocyanine catalyst (code: im-Nipc / CNT).

[0064] Comparative Example 1

[0065] A method for preparing a nickel phthalocyanine catalyst (number: Nipc / CNT) comprises the following steps:

[0066] Step 1, under a nitrogen atmosphere, phthalonitrile (0.102 g, 0.8 mmol), anhydrous NiCl2 (0.104 g, 0.8 mmol) and 1.8 diazabicyclo [5.4.0] undec-7-ene (0.5 mL) were dispersed in super dry n-pentanol (20 mL), and refluxed at 80° C. for 24 hours under stirring. After the reaction, a dark green reaction solution was obtained, which was cooled to room temperature and diluted with methanol (100 mL) to allow solid precipitates to appear in the reaction solution. The solution was filtered, and the solid precipitates were washed twice each with n-hexane, methanol, ethanol and water in turn, and dried at -80° C. for 48 hours to obtain nickel phthalocyanine (code: Nipc).

[0067] Step 2, dissolving nickel phthalocyanine (0.003 g) in DMF (30 mL) to obtain a nickel phthalocyanine solution. Dispersing carbon nanotubes (0.03 g) in another portion of DMF (30 mL) by ultrasonication at 100 Hz for 1 hour to obtain a carbon nanotube solution. Mixing the nickel phthalocyanine solution and the carbon nanotube solution and ultrasonication at 100 Hz for 1 hour, stirring for 12 hours after ultrasonication, filtering, washing with DMF, ethanol and water twice in sequence, freeze-drying at -80°C for 48 hours, and obtaining a nickel phthalocyanine catalyst (No.: Nipc / CNT).

[0068] The benzimidazole-modified nickel phthalocyanine catalyst prepared in Example 2 and the nickel phthalocyanine catalyst prepared in Comparative Example 1 were tested by an X-ray photoelectron spectrometer to obtain the XPS spectrum of the electronic structure of the Ni site (i.e., Co2p diagram), as shown in FIG. Figure 1 As shown by Figure 1 It can be seen that the Ni2p of the benzimidazole-modified nickel phthalocyanine catalyst prepared in Example 2 3 / 2 The fitting peak is at 856 eV, Ni2p 1 / 2 The fitting peak is at 873.89 eV, while the Ni2p 3 / 2 The fitting peak is at 855.05 eV, Ni2p 1 / 2 The fitting peak is at 872.63 eV. It can be seen that compared with the nickel phthalocyanine catalyst prepared in Comparative Example 1, the benzimidazole-modified nickel phthalocyanine prepared in Example 2 has a higher binding energy and is more conducive to the charge transfer between the central metal Ni and the conductive substrate (carbon nanotubes).

[0069] Energy dispersive X-ray scanning (TEM-EDS) tests were performed on the benzimidazole-modified nickel phthalocyanine catalyst prepared in Example 2 and the nickel phthalocyanine catalyst prepared in Comparative Example 1 using a transmission electron microscope. The test results are as follows: Figure 2 and Figure 3 As shown by Figure 2 (a) shows that the benzimidazole-modified nickel phthalocyanine catalyst prepared in Example 2 has a carbon nanotube structure. Figure 2 It can be seen from (be) that since the benzimidazole-modified nickel phthalocyanine catalyst prepared in Example 2 contains a mercaptobenzimidazole structure, it contains the S element, and the S element is clearly distributed. At the same time, the C element, the N element and the Ni element are also evenly distributed on the carbon nanotubes. This proves that the benzimidazole-modified nickel phthalocyanine catalyst prepared in Example 2 is successfully prepared and evenly loaded on the surface of the carbon nanotubes. Figure 3 It can be seen that the elements in the nickel phthalocyanine catalyst prepared in Comparative Example 1 are evenly distributed, and its preparation is successful.

[0070] Example 3

[0071] In the reversible hydrogen voltage range of -1.45 to -0.25 V, a linear voltammetric scan was performed on an H-type electrolytic cell (the electrolyte was a KCl-HCl mixed solution) using the benzimidazole-modified nickel phthalocyanine catalyst prepared in Example 2 and the nickel phthalocyanine catalyst prepared in Comparative Example 1 as the "catalyst" to obtain the current density of each catalyst at different voltages. The test results are shown in FIG. Figure 4 As shown by Figure 4 It can be seen that at a reversible hydrogen voltage of -1.45 V, the current density of the H-type electrolytic cell using the benzimidazole-modified nickel phthalocyanine catalyst prepared in Example 2 can reach 49.6 mA cm -2 However, the current density of the H-type electrolytic cell using the nickel phthalocyanine catalyst prepared in Comparative Example 1 was only 27.3 mA cm -2 In Example 2, the activity of the central metal Ni is optimized and the electron transmission and electron transfer capabilities are enhanced, which enables the benzimidazole-modified nickel phthalocyanine catalyst prepared in Example 2 to have high catalytic activity.

[0072] Example 4

[0073] In the reversible hydrogen voltage range of -1.35V to 1.6V, a cyclic voltammetry scan was performed at a rate of 0.05V / s on an H-type electrolytic cell (the electrolyte was a KCl-HCl mixed solution) using the benzimidazole-modified nickel phthalocyanine catalyst prepared in Example 2 and the nickel phthalocyanine catalyst prepared in Comparative Example 1 as the "catalyst". The test results are as follows: Figure 5 As shown by Figure 5 It can be seen that the reduction peak of the H-type electrolytic cell using the benzimidazole-modified nickel phthalocyanine catalyst prepared in Example 2 appears at 1.16V (vs. RHE), and the reduction peak of the H-type electrolytic cell using the nickel phthalocyanine catalyst prepared in Comparative Example 1 appears at 1.22V (vs. RHE). After modification with the benzimidazole group, the electronic structure of the benzimidazole-modified nickel phthalocyanine in the benzimidazole-modified nickel phthalocyanine catalyst prepared in Example 2 changes, and its reduction peak moves forward by 60mV. This is because the electrolyte in the H-type electrolytic cell is acidic, and the protons (H + ) combines with the 1-position N atom in the benzimidazole group to form an organic cationic structure, so the benzimidazole-modified nickel phthalocyanine catalyst prepared in Example 2 exhibits a strong electron-withdrawing property, which also means that under acidic conditions, the benzimidazole-modified nickel phthalocyanine catalyst prepared in Example 2 is more conducive to the reduction of CO2 in the electrocatalytic process and can better inhibit the hydrogen evolution reaction in the process of electrocatalytic reduction of CO2.

[0074] Example 5

[0075] At a reversible hydrogen voltage of -1.00 V, an impedance test was performed on an H-type electrolytic cell (the electrolyte was a KCl-HCl mixed solution) using the benzimidazole-modified nickel phthalocyanine catalyst prepared in Example 2 and the nickel phthalocyanine catalyst prepared in Comparative Example 1 as the "catalyst". The test results are as follows: Figure 6 As shown by Figure 6 It can be seen that the H-type electrolytic cell using the benzimidazole-modified nickel phthalocyanine catalyst prepared in Example 2 has a smaller semicircle radius than the H-type electrolytic cell using the nickel phthalocyanine catalyst prepared in Comparative Example 1, indicating that the benzimidazole-modified nickel phthalocyanine catalyst prepared in Example 2 has a smaller resistance than the nickel phthalocyanine catalyst prepared in Comparative Example 1. After fitting the data, it is obtained that the resistance of the benzimidazole-modified nickel phthalocyanine catalyst prepared in Example 2 is 50.8Ω, and the resistance of the nickel phthalocyanine catalyst prepared in Comparative Example 1 is 460Ω, further indicating that in the benzimidazole-modified nickel phthalocyanine catalyst prepared in Example 2, the electron transmission reaction speed between the benzimidazole-modified nickel phthalocyanine and the carbon nanotubes is faster, and the surface reaction activity is higher.

[0076] Example 6

[0077] The electrocatalytic CO2 reduction test was carried out by constant voltage current method at different reversible hydrogen voltages G on H-type electrolytic cells (electrolyte is KCl-HCl mixed solution) using the benzimidazole-modified nickel phthalocyanine catalyst prepared in Example 2 and the nickel phthalocyanine catalyst prepared in Comparative Example 1 as "catalysts". The composition and concentration of the generated gas (carbon monoxide and hydrogen) were detected by gas chromatography. The concentration was calculated according to the Faraday efficiency calculation formula in the literature (Zhu Jiajia, Rui Jialiang, Shi Wenwen, et al. Construction of nickel / nitrogen co-doped self-supporting foam carbon electrode and electrocatalytic CO2 reduction performance [J]. Journal of Chemistry in Universities, 2024, 45(10): 20-28.) to obtain the carbon monoxide Faraday efficiency (FE CO ) and the Faraday efficiency of hydrogen (FE H2 ), FE CO The test results and G are shown in Table 1 and Figure 7 As shown in (a), FE H2 The test results and G are shown in Table 2 and Figure 7 as shown in (b).

[0078] Table 1

[0079] G Example 2 Comparative Example 1 -0.95V(vs.RHE) 81％ 21％ -1.00V(vs.RHE) 91％ 26％ -1.05V(vs.RHE) 98％ 26％ -1.10V(vs.RHE) 98％ 34％ -1.15V(vs.RHE) 95％ 47％ -1.20V(vs.RHE) 94％ 47％ -1.25V(vs.RHE) 73％ 39％

[0080] From Table 1 and Figure 7 (a) shows that the benzimidazole-modified nickel phthalocyanine catalyst prepared in Example 2 has a higher carbon monoxide Faraday efficiency FE CO , at -1.05V reversible hydrogen voltage FE CO The FE of the nickel phthalocyanine catalyst prepared in Comparative Example 1 reached 98%, which is much higher than that of the nickel phthalocyanine catalyst prepared in Comparative Example 1.CO (26%), and under different reversible hydrogen voltage ranges, the FE of the benzimidazole-modified nickel phthalocyanine catalyst prepared in Example 2 CO They are both higher than the nickel phthalocyanine catalyst prepared in Comparative Example 1, reaching 2 to 3 times, which proves that the benzimidazole-modified nickel phthalocyanine catalyst prepared in Example 2 has excellent CO2 reduction performance.

[0081] Table 2

[0082]

[0083]

[0084] FE of the benzimidazole-modified nickel phthalocyanine catalyst prepared in Example 2 at different reversible hydrogen voltages H2 are all less than 6%, while the FE of the nickel phthalocyanine catalyst prepared in Comparative Example 1 is H2 The lowest reached 22%, which is precisely because of the modification of the benzimidazole group that the benzimidazole-modified nickel phthalocyanine catalyst prepared in Example 2 can effectively inhibit the occurrence of hydrogen evolution reaction under acidic conditions. Therefore, the benzimidazole-modified nickel phthalocyanine catalyst of the present invention has more excellent product selectivity under acidic electrolyte.

[0085] Example 7

[0086] The stability of the H-type electrolytic cell (electrolyte is KCl-HCl mixed solution) with the benzimidazole-modified nickel phthalocyanine catalyst prepared in Example 2 as the "catalyst" was tested by constant voltage current method at -1.00V reversible hydrogen voltage. The test results Figure 8 As shown by Figure 8 It can be seen that during the 20-hour test, the current density was 75 mA cm -2 The Faraday efficiency of carbon monoxide has remained stable at an average of 91%.

[0087] Example 8

[0088] The electrocatalytic CO2 reduction test was performed by constant voltage current method at different reversible hydrogen voltages G on an H-type electrolytic cell (electrolyte is a K2SO4-H2SO4 mixed solution) using the benzimidazole-modified nickel phthalocyanine catalyst prepared in Example 2 as the "catalyst" to obtain the carbon monoxide Faraday efficiency (such as Fig. 9 Medium FE CO (H2SO4) and shown in Table 3) and the hydrogen Faraday efficiency (as Fig. 9 Medium FE H2 (H2SO4) and as shown in Table 3), and the FE of the benzimidazole-modified nickel phthalocyanine catalyst prepared in Example 2 in Example 6 CO (like Fig. 9 Medium FECO (HCl)) and FE H2 (like Fig. 9 Medium FE H2 (HCl)) to analyze the electrocatalytic performance under different electrolyte pH. Fig. 9 It can be seen that within the reversible hydrogen voltage range of -1.15V to -1.00V, the carbon monoxide Faraday efficiency is above 90%, and its hydrogen Faraday efficiency is controlled below 7%.

[0089] Table 3

[0090]

[0091]

[0092] Example 9

[0093] The electrocatalytic CO2 reduction test was carried out by constant voltage current method at different reversible hydrogen voltages G on H-type electrolytic cells (electrolyte is KHCO3 aqueous solution) using the benzimidazole-modified nickel phthalocyanine catalyst prepared in Example 2 and the nickel phthalocyanine catalyst prepared in Comparative Example 1 as "catalysts" to obtain the carbon monoxide Faraday efficiency (FE CO ) and the Faraday efficiency of hydrogen (FE H2 ), FE CO The test results and G are shown in Table 4 and Fig.10 As shown in (a), FE H2 The test results and G are shown in Table 4 and Fig.10 As shown in (b), from Table 4 and Fig.10 It can be seen that under neutral conditions, the benzimidazole-modified nickel phthalocyanine catalyst prepared in Example 2 still has a better carbon monoxide Faraday efficiency than the nickel phthalocyanine catalyst prepared in Comparative Example 1.

[0094] Table 4

[0095]

[0096] Thermo Scientific Nicolet iS20 spectrometer was used to analyze the -1 The benzimidazole-modified nickel phthalocyanine prepared in Example 1 and the nickel phthalocyanine in Comparative Example 1 were analyzed by FT-IR. The test results are as follows: Fig.11 It can be seen that Fig.11 It can be seen that in the Fourier transform infrared spectrum of nickel phthalocyanine, at 2914 cm -1 The absorption peak at 1603 cm-1 is attributed to the CH stretching vibration. -1 The absorption peak at 1524 cm-1 is attributed to the internal stretching vibration of the benzene ring. -1The absorption peak at 1392 cm is attributed to the plane deformation vibration of the benzene ring. -1 The absorption peak at 1093 cm is attributed to CC stretching vibration. -1 The absorption peak at 716 cm is attributed to the NN stretching vibration and the -1 The absorption peak at 2959 cm-1 is attributed to the vibration of CN on the conjugated ring of phthalocyanine. -1 、1604cm -1 、1531cm -1 、1406cm -1 、1102cm -1 and 725cm -1 Vibration peaks similar to those of nickel phthalocyanine were also found. These peaks showed a slight blue shift compared with nickel phthalocyanine, which may be due to the change in the electronic structure caused by the introduction of the benzimidazole group, which can better reduce the reaction barrier of benzimidazole-modified nickel phthalocyanine. In addition, at 3062 cm -1 934cm -1 The CH stretching vibration peak and CH bending vibration peak in the benzimidazole group were also found at , which proved the successful synthesis of the benzimidazole-modified nickel phthalocyanine prepared in Example 1.

[0097] The present invention is described above by way of example. It should be noted that, without departing from the core of the present invention, any simple deformation, modification or other equivalent replacement that can be made by those skilled in the art without inventive effort falls within the protection scope of the present invention.

Claims

1. A benzimidazole-modified nickel phthalocyanine, characterized in that: Its structural formula is as follows:

2. A method for preparing benzimidazole-modified nickel phthalocyanine, characterized in that: The following steps are involved: Step 1, dissolving 4-nitrophthalonitrile in anhydrous DMF, adding 2-mercaptobenzimidazole under a nitrogen atmosphere, stirring at 50-60° C. for 20-30 minutes, adding anhydrous potassium carbonate several times, reacting at 50-55° C. for 72-84 hours under stirring, and obtaining a mixture after the reaction is completed. The mixture is poured into ice water and stirred, and allowed to stand for at least 12 hours, filtered, washed, and freeze-dried to obtain 4-{[1H-benzo(d)imidazol-2-yl]thiol}phthalonitrile, wherein the ratio of 4-nitrophthalonitrile to 2-mercaptobenzimidazole is (1-2):(1-2) by mass; Step 2, under a nitrogen atmosphere, 4-{[1H-benzo(d)imidazol-2-yl]thiol}phthalonitrile, anhydrous NiCl2 and 1.8 diazabicyclo[5.4.0]undec-7-ene are dispersed in ultra-dry n-pentanol, and refluxed at 70-90° C. for 20-24 hours under stirring. After the reaction is completed, a reaction solution is obtained, which is cooled to room temperature, diluted with a first solvent to produce a solid precipitate, filtered, washed, and freeze-dried. The reaction mixture is dried to obtain benzimidazole-modified nickel phthalocyanine, wherein the mass fraction of 4-{[1H-benzo(d)imidazol-2-yl]thiol}phthalonitrile, the mass fraction of anhydrous NiCl2 and the volume fraction of 1.8 diazabicyclo[5.4.0]undec-7-ene is (0.2-0.3):(0.1-0.2):(0.5-0.6), the unit of the mass fraction is g, and the unit of the volume fraction is mL.

3. The preparation method according to claim 2, characterized in that: The mass fraction of the 4-nitrophthalonitrile, the mass fraction of anhydrous potassium carbonate and the volume fraction of anhydrous DMF are (1-2): (4-8): (35-40), the unit of the mass fraction is g, and the unit of the volume fraction is mL.

4. The preparation method according to claim 2, characterized in that: The operation of adding anhydrous potassium carbonate in multiple times includes: adding the anhydrous potassium carbonate in 6 to 8 times within 2 to 3 hours.

5. The preparation method according to claim 2, characterized in that: The mixture is poured into ice water and stirred for 1 to 2 hours; the first solvent is methanol.

6. The preparation method according to claim 2, characterized in that: The ratio of the mass fraction of anhydrous NiCl2, the volume fraction of ultra-dry n-pentanol and the volume fraction of the first solvent is (0.1-0.2):(20-30):(100-150), the unit of the mass fraction is g, and the unit of the volume fraction is mL.

7. A method for preparing a benzimidazole-modified nickel phthalocyanine catalyst, characterized in that: The following steps are involved: Dissolve one of the benzimidazole-modified nickel phthalocyanine in claim 1 and the benzimidazole-modified nickel phthalocyanine obtained by the preparation method described in claims 2 to 6 in a second solvent to obtain a nickel phthalocyanine solution, disperse carbon nanotubes in a third solvent by ultrasound to obtain a carbon nanotube solution, mix the nickel phthalocyanine solution and the carbon nanotube solution, ultrasound, stir for 12 to 24 hours, filter, wash, and freeze-dry to obtain a benzimidazole-modified nickel phthalocyanine catalyst, wherein the ratio of the benzimidazole-modified nickel phthalocyanine to the carbon nanotubes is (0.003 to 0.004): (0.03 to 0.04) by mass.

8. The preparation method according to claim 7, characterized in that: The mass fraction of benzimidazole-modified nickel phthalocyanine, the volume fraction of the second solvent and the volume fraction of the third solvent are (0.003-0.004): (30-40): (20-30), the unit of the mass fraction is g, the unit of the volume fraction is mL, the second solvent is DMF, and the third solvent is DMF.

9. The benzimidazole-modified nickel phthalocyanine catalyst obtained by the preparation method as claimed in claim 7.

10. Use of the benzimidazole-modified nickel phthalocyanine catalyst as claimed in claim 9 in electrocatalysis of CO2.

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