A benzimidazole modified phthalocyanine nickel catalyst, a preparation method and application thereof

Abstract

The application discloses a kind of benzimidazole modified phthalocyanine nickel catalyst and its preparation method and application, the preparation method of benzimidazole modified phthalocyanine nickel catalyst includes the following steps: benzimidazole modified phthalocyanine nickel is dissolved in second solvent, and phthalocyanine nickel solution is obtained, carbon nanotube is dispersed in third solvent, and carbon nanotube solution is obtained, phthalocyanine nickel solution and carbon nanotube solution are mixed, ultrasonic, stirring, suction filtration, washing, freeze-drying, and benzimidazole modified phthalocyanine nickel catalyst is obtained, the faraday efficiency of carbon monoxide of this benzimidazole modified phthalocyanine nickel catalyst is as high as 94% or more, can reach 98% at most, under acidic conditions, can effectively inhibit the occurrence of hydrogen evolution reaction generated in system, in relatively wide voltage range, its hydrogen faraday efficiency is controlled at 7% or less, with excellent product selectivity.

Description

Technical Field

[0001] This invention belongs to the fields of environmental functional materials and electrochemical technology, specifically relating to a benzimidazole-modified nickel phthalocyanine catalyst, its preparation method, and its application. Background Technology

[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 continuous population growth and rapid scientific and technological development, human demand for fossil fuels is increasing. However, fossil fuels are non-renewable energy sources with limited reserves, which exacerbates the energy crisis. On the other hand, the continuous use of fossil fuels results in the emission of large amounts of CO2 into the atmosphere, contributing to the acceleration of global warming. Electrochemically reducing CO2 to sustainable fuels or high-value chemicals (such as carbon monoxide, methane, ethanol, and ethylene) is a promising strategy. Among the chemicals produced by the electrocatalytic reduction of CO2, CO is a promising industrial feedstock that plays a crucial role in many industrial processes.

[0003] Nickel phthalocyanine catalysts, formed by supporting metal phthalocyanines on the surface of carbon nanotubes, are commonly used for the electrocatalytic reduction of CO2, exhibiting excellent performance, particularly in terms of product selectivity and current density. However, the electrocatalytic reduction of CO2 by nickel phthalocyanine is generally carried out under neutral or weakly alkaline conditions, and the reaction involves the formation of refractory carbonates. This can lead to the covering of active sites on the surface of the nickel phthalocyanine catalyst, thus affecting its stability and catalytic efficiency. Summary of the Invention

[0004] To address the shortcomings of existing technologies, the purpose of this 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, which uses 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 objective of this invention is to provide an application of a benzimidazole-modified nickel phthalocyanine catalyst in the electrocatalysis of CO2. This benzimidazole-modified nickel phthalocyanine catalyst can suppress the hydrogen evolution reaction in the electrocatalysis of CO2 under acidic conditions, and can also optimize the current density of the central active metal, promote electron overflow and transfer, and further improve the catalytic conversion rate of CO2.

[0008] The objective of this invention is achieved through the following technical solutions.

[0009] A benzimidazole-modified nickel phthalocyanine has the following structural formula:

[0010]

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

[0012] Step 1: Dissolve 4-nitrophthalonitrile in anhydrous DMF, add 2-mercaptobenzimidazole under a nitrogen atmosphere, stir at 50-60°C for 20-30 minutes, then add anhydrous potassium carbonate in several portions, and react at 50-55°C for 72-84 hours with stirring. After the reaction is complete, a mixture is obtained. Pour the mixture into ice water and stir, let stand for at least 12 hours, filter, wash, and freeze-dry to obtain 4-{[1H-benzo(d)imidazole-2-yl]thiol}phthalonitrile, wherein the ratio of 4-nitrophthalonitrile to 2-mercaptobenzimidazole by mass is (1-2):(1-2).

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

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

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

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

[0017] In step 1, the cleaning operation includes: rinsing the filtered solid with water until the filtrate is neutral, and then washing with methanol 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) were dispersed in ultra-dry n-pentanol. The mixture was refluxed at 70–90 °C for 20–24 hours with stirring. After the reaction was complete, the reaction solution was obtained, cooled to room temperature, diluted with the first solvent to form a solid precipitate, filtered, and washed. Freeze-drying yields benzimidazole-modified nickel phthalocyanine, wherein the mass fractions of 4-{[1H-benzimidazol-2-yl]thiol}phthalonitrile, the mass fractions of anhydrous NiCl2, and the volume fractions of 1,8-diazabicyclo[5.4.0]undec-7-ene are in the ratio of (0.2–0.3):(0.1–0.2):(0.5–0.6), where the mass fractions are in g and the volume fractions are in mL.

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

[0020] In 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), where the mass fraction is in g and the volume fraction is in mL.

[0021] In step 2, the washing process includes washing with hexane, methanol, ethanol and water 1 to 2 times each.

[0022] In steps 1 and 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 includes the following steps:

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

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

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

[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] The application of the above-mentioned benzimidazole-modified nickel phthalocyanine catalyst in electrocatalytic CO2 production.

[0031] In the above technical solution, the electrocatalytic electrolyte has a pH of less than 8, preferably less than 7.2, and even 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 gives it better catalytic activity.

[0034] (2) The benzimidazole-modified nickel phthalocyanine catalyst of the present invention has a carbon monoxide faradaic efficiency of over 94% under a voltage of -1.20 to -1.00V (vs. RHE) and an electrolyte pH of 1.85, and can reach up to 98%. Under acidic conditions, it can effectively suppress the occurrence of hydrogen evolution reaction in the system. In a wide voltage range, its hydrogen faradaic efficiency is controlled below 7%, and it has excellent product selectivity. It provides new insights for electrocatalytic CO2 reduction in actual acidic environments. Attached Figure Description

[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 spectroscopy (EDS) spectra of the benzimidazole-modified nickel phthalocyanine catalyst prepared in Example 2, where (b) represents C, (c) represents N, (d) represents Ni, and (e) represents S.

[0037] Figure 3 (a) is the TEM image and (b-d) are the energy dispersive X-ray scan spectra of the nickel phthalocyanine catalyst prepared for Comparative Example 1, where (b) represents C, (c) represents N, and (d) represents Ni.

[0038] Figure 4 Linear voltammetric scans of the benzimidazole-modified nickel phthalocyanine catalyst prepared in Example 2 and the nickel phthalocyanine catalyst prepared in Comparative Example 1 in an H-type electrolyzer.

[0039] Figure 5 Cyclic voltammetry diagrams of H-type electrolyzers for the benzimidazole-modified nickel phthalocyanine catalyst prepared in Example 2 and the nickel phthalocyanine catalyst prepared in Comparative Example 1.

[0040] Figure 6 Impedance diagrams (EIS) of H-type electrolyzers using the benzimidazole-modified nickel phthalocyanine catalyst prepared in Example 2 and the nickel phthalocyanine catalyst prepared in Comparative Example 1.

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

[0042] Figure 8 The current density and carbon monoxide faradaic efficiency (FE) of an H-type electrolyzer using the benzimidazole-modified nickel phthalocyanine catalyst prepared in Example 2 were measured after 20 hours of electrocatalysis at electrolyte pH = 1.85. CO )picture;

[0043] Figure 9 The following describes the (a) carbon monoxide Faradaic efficiency (FE) of an H-type electrolyzer using the benzimidazole-modified nickel phthalocyanine catalyst prepared in Example 2 under different electrolytes. CO (a) and (b) hydrogen Faraday efficiency (FE) H2 )picture;

[0044] Figure 10 The carbon monoxide faradaic efficiency (FE) of an H-type electrolyzer using the benzimidazole-modified nickel phthalocyanine catalyst prepared in Example 2 and the nickel phthalocyanine catalyst prepared in Comparative Example 1 at electrolyte pH = 7.2 is shown to be (a) CO (a) and (b) hydrogen Faraday efficiency (FE) H2 )picture;

[0045] Figure 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 Implementation

[0046] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments.

[0047] The following medicines can be purchased from the following sources:

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

[0049] In the following embodiments, XPS spectra were measured using an X-ray photoelectron spectrometer (manufacturer: Thermo Fisher Scientific K-Alpha). The X-ray photoelectron spectrometer testing conditions were as follows: the vacuum level of the analysis chamber was 5 × 10⁻⁶. -10 The excitation source was Al-ka rays (hv = 1486.68 eV), the operating voltage was 15 kV, the filament current was 10 mA, and signal accumulation was performed 5-10 times. The test pass energy was 50 eV, the step size was 0.05 eV, and the charging correction was based on the binding energy C1s = 284.80 eV.

[0050] In the following examples, the microstructure was analyzed using a transmission electron microscope (TEM, model: FEI-Tecnai G2 F20 S-Twin) at an accelerating voltage of 200 kV to obtain transmission electron microscope (TEM) images.

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

[0052] In the following embodiments, the method for preparing the working electrode includes: placing 2 mg of catalyst, 1990 μL of ethanol and 10 μL of Nafion membrane solution in a 2 mL centrifuge tube, sonicating for 1 hour to obtain an ink-like mixture, and uniformly dropping 300 μL of the mixture onto a 1 cm² surface. 2 Both sides of the carbon cloth were dried in an oven at 60°C for 5 minutes. The carbon cloth with the mixed liquid dripped onto both sides was fixed with a platinum electrode clamp to obtain the working electrode. The catalyst was either 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 includes: a working electrode, a reference electrode, and a counter electrode; the electrolyte is one of the following: 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, with a KCl concentration of 0.5 M and an HCl concentration of 0.01 M; the K2SO4-H2SO4 mixed solution... The solution 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 includes the following steps:

[0056]

[0057] Step 1: Dissolve 1.73 g (0.01 mol) of 4-nitrophthalonitrile in 35 mL of anhydrous DMF. Under a nitrogen atmosphere, add 1.50 g (0.01 mol) of 2-mercaptobenzimidazole and stir at 50 °C for 20 minutes. Then, add 4.14 g (0.03 mol) of anhydrous potassium carbonate in 8 portions over 2 hours. React at 50 °C for 72 hours with stirring. After the reaction is complete, a mixture is obtained. Pour the mixture into ice water and stir for 2 hours. Let it stand for 12 hours. Filter and collect the gray solid. Wash the gray solid with water until the filtrate is neutral. Wash it three times with methanol and freeze-dry 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-benzimidazol-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). The mixture was refluxed at 80 °C for 24 hours with stirring. After the reaction was completed, a dark green reaction solution was obtained. The solution was cooled to room temperature and diluted with methanol (100 mL) to produce a solid precipitate. The solution was filtered and washed twice each with n-hexane, methanol, ethanol, and water, and then freeze-dried at -80 °C for 48 hours to obtain benzimidazol-modified nickel phthalocyanine (number: im-Nipc).

[0059] Example 2

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

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

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

[0063] The nickel phthalocyanine solution and carbon nanotube solution were mixed and sonicated at 100 Hz for 1 hour. After sonication, the mixture was stirred for 12 hours, filtered, and washed twice each with DMF, ethanol and water, and then freeze-dried at -80℃ for 48 hours to obtain the benzimidazole-modified nickel phthalocyanine catalyst (number: im-Nipc / CNT).

[0064] Comparative Example 1

[0065] A method for preparing a nickel phthalocyanine catalyst (No.: Nipc / CNT) includes 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 ultra-dry n-pentanol (20 mL). The mixture was refluxed at 80 °C for 24 hours with stirring. After the reaction was completed, a dark green reaction solution was obtained. The solution was cooled to room temperature and diluted with methanol (100 mL) to make a solid precipitate appear in the reaction solution. The solution was filtered and washed twice each with n-hexane, methanol, ethanol, and water, respectively. The solution was dried at -80 °C for 48 hours to obtain nickel phthalocyanine (Number: Nipc).

[0067] Step 2: Dissolve 0.003 g of nickel phthalocyanine in 30 mL of DMF to obtain a nickel phthalocyanine solution. Disperse 0.03 g of carbon nanotubes in another 30 mL of DMF by sonication at 100 Hz for 1 hour to obtain a carbon nanotube solution. Mix the nickel phthalocyanine solution and the carbon nanotube solution and sonicate at 100 Hz for 1 hour. After sonication, stir for 12 hours, filter, wash twice each with DMF, ethanol, and water, and freeze-dry at -80°C for 48 hours to obtain the nickel phthalocyanine catalyst (catalyst: 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 using X-ray photoelectron spectroscopy to obtain the XPS spectra (i.e., Co2p diagrams) of the electronic structure of the Ni sites, as shown below. 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 is... 3 / 2 The fitting peak is at 856 eV, Ni2p 1 / 2 The fitting peak is at 873.89 eV, while the Ni2p peak of the nickel phthalocyanine catalyst prepared in Comparative Example 1 is... 3 / 2 The fitting peak is at 855.05 eV, Ni2p 1 / 2 The fitting peak is at 872.63 eV, indicating 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 charge transfer between the central metal Ni and the conductive substrate (carbon nanotubes).

[0069] The benzimidazole-modified nickel phthalocyanine catalyst prepared in Example 2 and the nickel phthalocyanine catalyst prepared in Comparative Example 1 were tested using energy-dispersive X-ray diffraction (TEM-EDS) microscopy. The test results are as follows: Figure 2 and Figure 3 As shown, by Figure 2 As can be seen from (a), the benzimidazole-modified nickel phthalocyanine catalyst prepared in Example 2 has a carbon nanotube structure. Figure 2 As can be seen from (be), since the benzimidazole-modified nickel phthalocyanine catalyst prepared in Example 2 contains a mercaptobenzimidazole structure, it contains sulfur (S) element, and its clear distribution, along with the uniform distribution of carbon (C), nitrogen (N), and nickel (Ni) elements on the carbon nanotubes, proves that the benzimidazole-modified nickel phthalocyanine catalyst prepared in Example 2 was successfully prepared and uniformly loaded onto 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 was successful.

[0070] Example 3

[0071] Linear voltammetry scans were performed in an H-type electrolyzer (electrolyte: 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" within a reversible hydrogen voltage range of -1.45 to -0.25 V, to obtain the current density of each catalyst at different voltages. The test results are as follows: Figure 4 As shown, by Figure 4 It can be seen that, under a reversible hydrogen voltage of -1.45V, the current density of the H-type electrolyzer using the benzimidazole-modified nickel phthalocyanine catalyst prepared in Example 2 can reach 49.6 mA cm⁻¹. -2 However, the current density of the H-type electrolytic cell using the nickel phthalocyanine catalyst prepared in Comparative Example 1 only reached 27.3 mA cm⁻¹. -2 In Example 2, the activity of the central metal Ni was optimized and the electron transport and electron transfer capabilities were enhanced, which enabled the benzimidazole-modified nickel phthalocyanine catalyst prepared in Example 2 to have high catalytic activity.

[0072] Example 4

[0073] Cyclic voltammetry scans were performed at a rate of 0.05 V / s on H-type electrolyzers using the benzimidazole-modified nickel phthalocyanine catalyst prepared in Example 2 and the nickel phthalocyanine catalyst prepared in Comparative Example 1 as "catalysts". 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 electrolyzer using the benzimidazole-modified nickel phthalocyanine catalyst prepared in Example 2 appears at 1.16 V (vs. RHE), while the reduction peak of the H-type electrolyzer using the nickel phthalocyanine catalyst prepared in Comparative Example 1 appears at 1.22 V (vs. RHE). After modification with the benzimidazole group, the electronic structure of the benzimidazole-modified nickel phthalocyanine catalyst prepared in Example 2 changes, and its reduction peak shifts positively by 60 mV. This is because the electrolyte in the H-type electrolyzer is acidic, and the protons (H+) in the electrolyte... + The benzimidazole-modified nickel phthalocyanine catalyst prepared in Example 2 combines with the N atom at the 1-position of the benzimidazole group to form an organic cation structure. Therefore, the benzimidazole-modified nickel phthalocyanine catalyst prepared in Example 2 exhibits strong electron-withdrawing properties. This 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 electrocatalysis and can better suppress the hydrogen evolution reaction in the process of electrocatalytic reduction of CO2.

[0074] Example 5

[0075] Impedance tests were performed on H-type electrolyzers (electrolyte being 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 "catalysts" at a reversible hydrogen voltage of -1.00 V. 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 semi-circular radius than the H-type electrolytic cell using the nickel phthalocyanine catalyst prepared in Comparative Example 1. This indicates 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, the resistance of the benzimidazole-modified nickel phthalocyanine catalyst prepared in Example 2 is 50.8 Ω, while the resistance of the nickel phthalocyanine catalyst prepared in Comparative Example 1 is 460 Ω. This further indicates that in the benzimidazole-modified nickel phthalocyanine catalyst prepared in Example 2, the electron transport reaction rate between the benzimidazole-modified nickel phthalocyanine and carbon nanotubes is faster, and the surface reaction activity is higher.

[0076] Example 6

[0077] Electrocatalytic CO2 reduction was tested in an H-type electrolytic cell (electrolyte: 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" under different reversible hydrogen voltages G using the constant voltage current method. The composition and concentration of the generated gases (carbon monoxide and hydrogen) were detected by gas chromatography. The concentrations were used to calculate the carbon monoxide faradaic efficiency (FE) according to the Faradaic efficiency calculation formula in the literature (Zhu Jiajia, Rui Jialiang, Shi Wenwen, et al. Construction and electrocatalytic CO2 reduction performance of nickel / nitrogen co-doped self-supporting foam carbon electrode [J]. Journal of Chemical Research in Chinese Universities, 2024, 45(10):20-28.). CO ) and hydrogen Faraday efficiency (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 As shown in (a), the benzimidazole-modified nickel phthalocyanine catalyst prepared in Example 2 has a higher carbon monoxide Faraday efficiency (FE). CO At a reversible hydrogen voltage of -1.05V, FE CO The efficiency reached 98%, far exceeding 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 The CO2 reduction performance of the benzimidazole-modified nickel phthalocyanine catalyst prepared in Example 2 was 2 to 3 times higher than that of the nickel phthalocyanine catalyst prepared in Comparative Example 1, which proves that the CO2 reduction performance of the benzimidazole-modified nickel phthalocyanine catalyst prepared in Example 2 is excellent.

[0081] Table 2

[0082]

[0083]

[0084] The FE of the benzimidazole-modified nickel phthalocyanine catalyst prepared in Example 2 under different reversible hydrogen voltages H2 All were less than 6%, while the FE of the nickel phthalocyanine catalyst prepared in Comparative Example 1 was... H2 The lowest selectivity reached 22%, which is precisely because the benzimidazole group modification enabled the benzimidazole-modified nickel phthalocyanine catalyst prepared in Example 2 to effectively suppress the hydrogen evolution reaction under acidic conditions. Therefore, the benzimidazole-modified nickel phthalocyanine catalyst of the present invention exhibits superior product selectivity under acidic electrolyte conditions.

[0085] Example 7

[0086] The stability of the benzimidazole-modified nickel phthalocyanine catalyst prepared in Example 2, used as the "catalyst," in an H-type electrolyzer (electrolyte: KCl-HCl mixed solution) was tested using a constant voltage current method at a reversible hydrogen voltage of -1.00 V. 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⁻¹. -2 The levels fluctuated steadily in the vicinity, and the carbon monoxide Faraday efficiency remained stable at an average of 91%.

[0087] Example 8

[0088] Electrocatalytic CO2 reduction was tested in an H-type electrolyzer (electrolyte: K2SO4-H2SO4 mixed solution) using the benzimidazole-modified nickel phthalocyanine catalyst prepared in Example 2 as the "catalyst" at different reversible hydrogen voltages G using the constant voltage current method. The carbon monoxide Faradaic efficiency (e.g.) was obtained. Figure 9 FE CO (H2SO4) and as shown in Table 3) and hydrogen Faraday efficiency (e.g. Figure 9 FE H2 (H2SO4) and as shown in Table 3), it was compared with the benzimidazole-modified nickel phthalocyanine catalyst prepared in Example 2 of Example 6 for FE CO (like Figure 9 FECO (HCl) and FE H2 (like Figure 9 FE H2 Statistical analysis was conducted using (HCl) as shown in Table 3 to analyze the electrocatalytic behavior under different electrolyte pH values. Figure 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%, while the hydrogen Faraday efficiency is controlled below 7%.

[0089] Table 3

[0090]

[0091]

[0092] Example 9

[0093] Electrocatalytic CO2 reduction was tested in an H-type electrolytic cell (electrolyte: 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" at different reversible hydrogen voltages G using the constant voltage current method. The carbon monoxide Faradaic efficiency (FE) was obtained. CO ) and hydrogen Faraday efficiency (FE) H2 ), FE CO The test results and G are shown in Table 4 and Figure 10 As shown in (a), FE H2 The test results and G are shown in Table 4 and Figure 10 As shown in (b), from Table 4 and Figure 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] Using a Thermo Scientific Nicolet iS20 spectrometer at 4 cm⁻¹ -1 FT-IR analysis was performed on the benzimidazole-modified nickel phthalocyanine prepared in Example 1 and the nickel phthalocyanine in Comparative Example 1 at a resolution of [resolution value missing]. The test results are as follows: Figure 11 It can be seen that, from Figure 11 It can be seen that in the Fourier transform infrared spectrum of nickel phthalocyanine, at 2914 cm⁻¹... -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⁻¹ is attributed to the planar deformation vibration of the benzene ring. -1 The absorption peak at 1093 cm⁻¹ is attributed to the C-C stretching vibration. -1 The absorption peak at 716 cm⁻¹ is attributed to the NN stretching vibration and the absorption peak at 716 cm⁻¹. -1 The absorption peak at 2959 cm⁻¹ is attributed to the CN vibration on the conjugated ring of phthalocyanine. In the Fourier transform infrared spectrum of the benzimidazole-modified phthalocyanine nickel prepared in Example 1, the peak at 2959 cm⁻¹ is... -1 1604cm -1 1531cm -1 1406cm -1 1102cm -1 and 725cm -1 Vibrational peaks similar to those of nickel phthalocyanine were also observed. These peaks showed a slight blue shift compared to nickel phthalocyanine, which may be due to the electronic structure change caused by the introduction of the benzimidazole group, which can better lower the reaction barrier of benzimidazole-modified nickel phthalocyanine. Furthermore, at 3062 cm⁻¹... -1 934cm -1 Furthermore, stretching and bending vibration peaks of the CH group in the benzimidazole group were also found. This confirms the successful synthesis of the benzimidazole-modified nickel phthalocyanine prepared in Example 1.

[0097] The present invention has been described above by way of example. It should be noted that any simple modifications, alterations or other equivalent substitutions that can be made by those skilled in the art without creative effort without departing from the core of the present invention fall within the protection scope of the present invention.

Claims

1. The application of a benzimidazole-modified nickel phthalocyanine catalyst in the electrocatalytic reduction of CO2, characterized in that, Benzimidazole-modified nickel phthalocyanine catalyst exhibits a carbon monoxide faradaic efficiency exceeding 94%, with a maximum of 98%, under conditions of -1.20 to -1.00 V vs. RHE voltage and electrolyte pH=1.

85. The preparation method of the benzimidazole-modified nickel phthalocyanine catalyst includes: dissolving benzimidazole-modified nickel phthalocyanine in a second solvent to obtain a nickel phthalocyanine solution; dispersing carbon nanotubes in a third solvent by ultrasound to obtain a carbon nanotube solution; mixing the nickel phthalocyanine solution and the carbon nanotube solution; ultrasound stirring for 12-24 hours; filtration; washing; and freeze-drying to obtain the benzimidazole-modified nickel phthalocyanine catalyst. The mass ratio of benzimidazole-modified nickel phthalocyanine to carbon nanotubes is (0.003-0.004):(0.03-0.04). The structural formula of benzimidazole-modified nickel phthalocyanine is as follows: 。 2. The application according to claim 1, characterized in that, The preparation method of benzimidazole-modified nickel phthalocyanine includes the following steps: Step 1: Dissolve 4-nitrophthalonitrile in anhydrous DMF, add 2-mercaptobenzimidazole under a nitrogen atmosphere, stir at 50-60°C for 20-30 minutes, then add anhydrous potassium carbonate in several portions, and react at 50-55°C for 72-84 hours with stirring. After the reaction is complete, a mixture is obtained. Pour the mixture into ice water and stir, let stand for at least 12 hours, filter, wash, and freeze-dry to obtain 4-{[1H-benzo(d)imidazole-2-yl]thiol}phthalonitrile, wherein the ratio of 4-nitrophthalonitrile to 2-mercaptobenzimidazole by mass is (1-2):(1-2). 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. The mixture is refluxed at 70-90°C for 20-24 hours with stirring. After the reaction is complete, the reaction solution is obtained, cooled to room temperature, diluted with the first solvent to form a solid precipitate, filtered, washed, and freeze-dried. The mixture was dried to obtain benzimidazole-modified nickel phthalocyanine, wherein the mass fractions of 4-{[1H-benzimidazole-2-yl]thiol}phthalonitrile, the mass fractions of anhydrous NiCl2, and the volume fractions of 1,8-diazabicyclo[5.4.0]undec-7-ene were in the ratio of (0.2~0.3):(0.1~0.2):(0.5~0.6), where the mass fractions were in g and the volume fractions were in mL.

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

4. The application according to claim 2, characterized in that, The operation of adding anhydrous potassium carbonate in multiple batches includes adding the anhydrous potassium carbonate in 6 to 8 batches over 2 to 3 hours.

5. The application 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 application 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), where the mass fraction is in g and the volume fraction is in mL.

7. The application according to claim 6, characterized in that, The mass fractions of benzimidazole-modified nickel phthalocyanine, the volume fractions of the second solvent, and the volume fractions of the third solvent are (0.003~0.004):(30~40):(20~30), where the mass fractions are in g and the volume fractions are in mL, the second solvent is DMF, and the third solvent is DMF.

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