Preparation method of electrocatalyst NiPPc added with Co element

Abstract

The invention discloses a preparation method of an electrocatalyst NiPPc added with Co element, and relates to the technical field of electrochemistry. The preparation method comprises the following steps: preparing NiPPc by adopting a solvothermal method: dispersing 40 milligrams of nickel acetate tetrahydrate and 90 milligrams of 1, 2, 4, 5-tetracyanobenzene in 35 milliliters of ethanol solution, stirring for 10 minutes, performing ultrasonic treatment for 30 minutes after stirring is completed, putting the mixture into a reaction kettle for reaction at 100 DEG C after the mixture is uniformly dispersed, washing the mixture with the ethanol solution after the mixture is completely reacted and naturally cooled, and performing forced air drying to obtain a sample NiPPc; cobalt acetate tetrahydrate with different mass fractions is added on the basis of the nickel element content, and Co-coated NiPPc is prepared. By controlling the doping amount of the metal ion Co, the activity and selectivity of the synthesis gas prepared by reducing the CO2 under the electrocatalysis of the NiPPc can be improved, so that the content of the carbon dioxide in the atmosphere is effectively reduced.

Description

Technical Field

[0001] The present invention relates to the field of electrochemical technology, and in particular to a method for preparing a Co-added electrocatalyst NiPPc. Background Art

[0002] Electrocatalytic reduction of carbon dioxide (CO2RR) is an effective measure to mitigate carbon emissions and an efficient way to produce synthesis gas. Metal phthalocyanine is a planar conjugated large π bond structure composed of 18 π electrons. It has a symmetrical molecular structure and a relatively uniform distribution of internal electron density, resulting in stable physical and chemical properties. Since phthalocyanine is generally composed of only C, N, O, H and a small amount of non-precious metal elements, it is inexpensive. However, metal phthalocyanine has poor antioxidant capacity. When used as a catalyst in a homogeneous reaction, its antioxidant capacity is weak and it exhibits low catalytic activity in catalytic applications. In addition, since metal phthalocyanine is not easy to recover from the system after the reaction, this may lead to catalyst waste and environmental pollution, which in turn causes secondary pollution problems. Therefore, designing a catalyst with high selectivity, high stability and high conversion rate remains a great challenge.

[0003] Nickel phthalocyanine is a new type of material with excellent conductivity and catalytic properties. It is often used in the field of electrocatalytic carbon dioxide reduction (CO2RR) and can significantly improve energy efficiency. It participates in various organic synthesis reactions such as hydrogenation, hydrogenation, reduction, and oxidation as a catalyst and has broad application prospects. The current research conducted by researchers mainly focuses on nitrogen-doped nickel phthalocyanine, doping nickel phthalocyanine, and ester-doped nickel phthalocyanine. In these research results, the electrocatalytic activity and stability of the catalyst have been significantly improved. However, its preparation cost is relatively high, the selectivity for specific products is poor, and the stability still needs to be further improved. Studies have found that catalysts with nickel as the metal center have the best CO2RR selectivity and poor activity, but catalysts with cobalt as the metal center have the best CO2RR activity. Summary of the Invention

[0004] The present invention aims to prepare a NiPPc electrocatalyst and to improve the activity, selectivity and stability of the catalyst and the performance of preparing synthesis gas by doping Co in the preparation of the NiPPc electrocatalyst.

[0005] To achieve the above object, the present invention provides the following solutions:

[0006] A method for preparing a Co-added electrocatalyst NiPPc, characterized in that NiPPc is prepared by a solvothermal method: 40 mg of nickel acetate tetrahydrate and 90 mg of 1,2,4,5-tetracyanobenzene are dispersed in 35 ml of an ethanol solution, stirred for 10 minutes, ultrasonicated for 30 minutes after stirring, and placed in a reactor at 100° C. for reaction after uniform dispersion. After the reaction is complete and naturally cooled, the NiPPc is washed with an ethanol solution and dried with air to obtain 1.63 g of a NiPPc sample;

[0007] Preparation of Co@NiPPc: Cobalt acetate tetrahydrate with different mass fractions was added based on the nickel content, and dispersed in 35 ml of ethanol solution with 40 mg of nickel acetate tetrahydrate and 90 mg of 1,2,4,5-tetracyanobenzene respectively. The mixture was stirred for 10 min, and ultrasonicated for 30 min after stirring. After uniform dispersion, the mixture was placed in a reactor for reaction. After the reaction was complete and naturally cooled, it was washed with ethanol solution and dried with air to obtain the sample Co@NiPPc.

[0008] Furthermore, different mass fractions of nickel element are added based on the nickel element content, namely 10%, 30%, 50%, 70%, and 90%. Beneficial effects of the present invention: By controlling the doping amount of metal ion Co, the present invention can improve the activity and selectivity of NiPPc electrocatalytic CO2 reduction to produce synthesis gas, thereby effectively reducing the content of carbon dioxide in the atmosphere. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] Figure 1 XRD patterns of Co@NiPPc with different Co doping amounts;

[0010] Figure 2 FT-IR images of Co@NiPPc with different Co doping amounts;

[0011] Figure 3 TEM images and elemental scans of Co@NiPPc, where (a, b) are TEM images; (cf) are elemental scans of Ni, Co, N, and C.

[0012] Figure 4 EDS pattern of Co@NiPPc;

[0013] Figure 5 XPS images of Co@NiPPc, where (a) is the full spectrum of Co@NiPPc; (b) is the detailed spectrum of Ni, Co, N and C elements in Co@NiPPc.

[0014] Figure 6 LSV and EIS diagrams of Co@NiPPc with different Co doping amounts (a)—LSV diagram; (b)—EIS diagram;

[0015] Figure 7 CV and Cdl diagrams of Cu@NiPPc with different Co doping amounts, including (a) 10wt% Co@NiPPc; (b) 30wt% Co@NiPPc; (c) 50wt% Co@NiPPc; (d) 70wt% Co@NiPPc; (e) 90wt% Co@NiPPc; (f) Cdl diagram;

[0016] Figure 8 It plots of Co@NiPPc with different Co doping amounts, where (a)—NiPPc; (b)—10wt% Co@NiPPc; (c)—30wt% Co@NiPPc; (d)—50wt% Co@NiPPc; (e)—70wt% Co@NiPPc; (f)—90wt% Co@NiPPc;

[0017] Figure 9 CO2 reduction performance diagram of Co@NiPPc with different Co doping amounts, including (a) FECO diagram; (b) FEH2 diagram; (c) jCO diagram; (d) CO / H2 diagram; DETAILED DESCRIPTION

[0018] The experimental raw materials and instruments selected in the present invention include: nickel acetate tetrahydrate, cobalt acetate tetrahydrate, Nafion and 1,2,4,5-tetracyanobenzene produced by Shanghai McLean Biochemical Technology Co., Ltd.; hydrochloric acid, ethanol, sulfuric acid and hydrogen peroxide produced by Tianjin Yongda Chemical Reagent Co., Ltd.; N,N-dimethylformamide produced by Tianjin Jindong Tianzheng Fine Chemical Reagent Factory; and potassium bicarbonate produced by Shanghai Aladdin Biochemical Technology Co., Ltd.

[0019] The test means and characterization methods adopted by the present invention are as follows: X-ray diffraction (XRD) is used to analyze the physical phase and crystal structure of the sample. Fourier transform infrared (FT-IR) spectroscopy is used to perform structural analysis and identification on the sample molecules. Raman spectroscopy is used to obtain the structural characteristics of the sample, such as functional groups and chemical bonds. Transmission electron microscopy (TEM) is used to study the microscopic morphology of the catalyst and the corresponding element distribution information. X-ray photoelectron spectrometer (XPS) is used to identify the chemical properties and composition analysis of the sample surface. The Faraday efficiency of CO and H2 is calculated by It data in the electrochemical test, and the CO partial current density is calculated to study the ability of the catalyst to reduce CO2. The component ratio in the generated synthesis gas is then studied by calculating the CO / H2 ratio.

[0020] Electrochemical Equipment Installation and Testing: For electrochemical testing, an Ag / AgCl electrode and a Pt sheet served as the reference and counter electrodes, respectively. A 0.5M KHCO₃ solution was used as the electrolyte. CO₂ was continuously bubbled through the cathode chamber for 30 minutes at a controlled CO₂ flow rate of 10 sccm. The working electrode was prepared as follows: Cut carbon paper was placed in a porcelain boat and calcined at 200°C for 3 hours in an argon atmosphere. 4 mg of catalyst was weighed and added to a 2 mL centrifuge tube. Ethanol and Nafion were added, and the catalyst was evenly dispersed by sonication for 30 minutes. 100 μL of the catalyst slurry was pipetted onto the carbon paper, and the coated carbon paper was dried under infrared light. The treated membrane was treated with hydrogen peroxide at 80°C for 1 hour to remove organic matter from the membrane surface. The membrane was then treated with boiling deionized water for 30 minutes to remove residual hydrogen peroxide. The membrane was then treated with boiling 1 M sulfuric acid for 30 minutes, and then boiled with deionized water for 30 minutes to remove residual sulfuric acid. Finally, 10.012 g of potassium bicarbonate was weighed and dissolved in 200 mL of deionized water, and the volume was adjusted to the desired level using a volumetric flask. Linear sweep voltammetry (LSV) was used to analyze the energy consumption of the sample and evaluate the catalyst's performance. Electrochemical impedance spectroscopy (EIS) was used to analyze the reaction kinetics of the material.

[0021] Explanation of the abbreviations appearing in the present invention: MKHCO3: refers to potassium bicarbonate in the text, which serves as a component of the electrolyte solution and provides an ion conductive environment.

[0022] Nafion: perfluorosulfonic acid resin.

[0023] NiPPc: nickel phthalocyanine.

[0024] Co@NiPPc: cobalt-doped nickel phthalocyanine.

[0025] NiPPc was prepared by a solvothermal method: 40 mg of nickel acetate tetrahydrate and 90 mg of 1,2,4,5-tetracyanobenzene were dispersed in 35 ml of ethanol solution and stirred for 10 minutes. After stirring, the mixture was ultrasonicated for 30 minutes. After uniform dispersion, the mixture was placed in a reactor at 100°C for reaction. After the reaction was complete and naturally cooled, the mixture was washed with ethanol solution and air-dried to obtain 1.63 g of NiPPc sample.

[0026] Preparation of Co@NiPPc: Cobalt acetate tetrahydrate with different mass fractions was added based on the nickel content, and dispersed in 35 ml of ethanol solution with 40 mg of nickel acetate tetrahydrate and 90 mg of 1,2,4,5-tetracyanobenzene respectively. The mixture was stirred for 10 min, and ultrasonicated for 30 min after stirring. After uniform dispersion, the mixture was placed in a reactor for reaction. After the reaction was complete and naturally cooled, it was washed with ethanol solution and dried with air to obtain the sample Co@NiPPc.

[0027] Co was doped at ratios of 10%, 30%, 50%, 70%, and 90% of the added nickel mass. The prepared Co@NiPPc were named 10wt%Co@NiPPc, 30wt%Co@NiPPc, 50wt%Co@NiPPc, 70wt%Co@NiPPc, and 90wt%Co@NiPPc, respectively, depending on the doped Co content.

[0028] Effect of Co doping amount on the composition and phase of Co@NiPPc

[0029] Figure 1 The XRD patterns of Co@NiPPc with different Co doping levels are shown in the figure. It can be observed that when Co is doped into the NiPPc structure, the diffraction peak intensity representing the polyphthalocyanine structure is significantly reduced, and the peak shape shows an amorphous diffraction feature. In the Co-doped Co@NiPPc material, the diffraction peak intensity at 2θ = 27° does not show an increasing trend with the increase of Co doping level.

[0030] To further analyze the effect of doping Co on the structure of NiPPc, we conducted FT-IR test on it. The results are as follows: Figure 2 70wt% Co@NiPPc has the strongest response at the infrared absorption peak corresponding to the phthalocyanine structure (721cm -1 、1103cm -1 and 1311cm -1 ), indicating that a complete polyphthalocyanine structure has been formed. When the Co doping amount reaches 70wt%, the signal of the coordination vibration between the metal and phthalocyanine is enhanced (912cm -1 ), indicating that more metal-phthalocyanine structures were formed. -1 and 1236cm -1 The infrared absorption peak intensity at 2231 cm-1 indicates that NiPPc with high Co doping (70 wt% and 90 wt%) will produce more CN bonds, which is consistent with the signal intensity of the CN group at the end of polyphthalocyanine (2231 cm-1). -1 ), indicating that part of the CN bond signals come from the CN groups at the end of polyphthalocyanine.

[0031] Figure 3 TEM image and elemental scanning image of Co@NiPPc. It can be seen that there are some spherical particles with a diameter of less than 500nm in Co@NiPPc, indicating that the doping of Co makes the NiPPc particles have a smaller particle size ( Figure 3 (a, b)), from Figure 3 (cf) It can be seen that Ni, Co, N and C elements are evenly distributed, indicating that Co is successfully doped. Figure 4 The EDS spectrum also further confirmed the formation of Co@NiPPc.

[0032] Figure 5 is the XPS graph of Co@NiPPc, where Figure 5 (a) is the full spectrum of Co@NiPPc, where the characteristic peaks of Ni, Co, N and C elements can be observed. The fine spectrum of Co 2p is shown in Figure 2. Figure 5 As shown in (c), the characteristic peaks at 779.73 eV and 794.48 eV are attributed to Co 2p 3 / 2 and Co 2p 1 / 2 , due to Co 2p 3 / 2 The characteristic peak is close to Co 2+ 2p 3 / 2 (780.84eV), so the valence of Co is +2. The effect of Co doping on Ni is small ( Figure 5 (b)), but the Pyridinic N of NiPPc doped with Co has a lower binding energy (395.53 eV), which is conducive to the coordination of active Ni and Pyridinic N. At the same time, Co doping also weakens the relative strength of Ni-N and reduces the binding energy of CN=C ( Figure 5 (d, e)), further indicating the successful doping of Co.

[0033] Effect of Co doping amount on electrocatalytic CO2 reduction performance of Co@NiPPc

[0034] Figure 6 (a) is the LSV diagram of Co@NiPPc with different Co doping amounts, which can be used to analyze the effect of the change in Co doping amount on the activity of NiPPc. In the range of 0 to -0.7 V (vs. RHE), 10wt% Co@NiPPc has relatively excellent activity; 30wt% Co@NiPPc, 50wt% Co@NiPPc, 70wt% Co@NiPPc, and 90wt% Co@NiPPc have lower activity than NiPPc in the range of -0.65 to -1.0 V (vs. RHE), but when the current density increases to 10 mA cm -2 After that, the activity of Co@NiPPc was better than that of NiPPc without Co doping. -2 At the current density of , 70wt% Co@NiPPc and 90wt% Co@NiPPc require the smallest potential. According to the EIS graph ( Figure 6 (b) It can be found that the impedance of 70wt% Co@NiPPc and 90wt% Co@NiPPc is also relatively small, showing a faster reaction rate, which is consistent with the conclusion of LSV, indicating that NiPPc with a high Co doping content has higher activity.

[0035] CV test ( Figure 7(ae)). By Figure 7 (f) It can be seen that the C dl 3.03mF cm -2 、0.962393mF cm -2 、0.266986mF cm -2 、0.642987mF cm -2 、0.847214mF cm -2 From a numerical point of view, 10wt% Co@NiPPc has the highest electrochemical surface area, which can accommodate more catalytic sites. The C dl It is also slightly higher than NiPPc without Co doping.

[0036] With the increase of Co doping amount, Co@NiPPc can achieve a higher current density at the same potential. Figure 8 As shown in Figure 2, when the Co doping content is 10wt%, the current density of Co@NiPPc at -0.9V (vs.RHE) is lower than that of NiPPc, but the current density obtained at high potential is similar to that of NiPPc. When the Co doping content is increased to 50wt%, Co@NiPPc reaches 10mA cm at -0.9V (vs.RHE). -2 The current density of 70wt% Co@NiPPc and 90wt% Co@NiPPc at high potential is higher than that of Co@NiPPc with other Co doping amounts (the current density is 22.5mA cm at -1.0V (vs.RHE)). -2 , 37.5 mA cm at -1.1 V (vs. RHE) -2 ), and the current density did not change significantly after electrolysis for 3600s, indicating that it has good stability, further proving that NiPPc has better activity after doping with Co.

[0037] Depend on Figure 9 (a) It can be seen that low-doped Co (10 wt%) improves the selectivity of NiPPc for CO at -0.8 V and -0.9 V (vs. RHE). CO Greater than 90%, and has excellent CO2 reduction activity at high potential ( Figure 9 (c) FE at -0.8 V (vs. RHE) COThe selectivity for CO at other potentials is generally low. CO When the doping amount of Co increased to 50wt%, the catalyst showed good HER performance at all potentials ( Figure 9 (b) FE of highly Co-doped NiPPc (70wt% Co@NiPPc and 90wt% Co@NiPPc) in a wide potential range of -0.7 to -1.1 V (vs. RHE) CO Maintained within 30% to 50%, and the CO / H2 value is around 1:1. For the synthesis gas with a ratio of CO and H2 of 1 ( Figure 9 (d)), Co@NiPPc with high Co content is the best choice, showing higher activity. Compared with the durability test results, the performance of 70wt% Co@NiPPc is slightly better than that of 90wt% Co@NiPPc.

[0038] In this study, a NiPPc electrocatalyst was successfully prepared using a solvothermal method for the electrocatalytic reduction of CO2. Co@NiPPc was prepared by adding the metal ion Co during the synthesis of NiPPc. The addition of Co reduced the size of the NiPPc particles. When the Co doping level was 70 wt%, the Co@NiPPc exhibited a more metal-phthalocyanine structure and achieved a high current density at high potentials, reaching 22.5 mA cm at -1.0 V and -1.1 V (vs. RHE), respectively. -2 and 37.5 mA cm -2 Co@NiPPc with low Co doping amounts (10wt% Co@NiPPc, 30wt% Co@NiPPc, and 50wt% Co@NiPPc) exhibits high CO selectivity and a higher CO partial current density than that of Co@NiPPc with high Co doping amounts. High Co doping amounts (70wt% Co@NiPPc and 90wt% Co@NiPPc) maintain FECO within 30% to 50% over a wide potential range of -0.7 to -1.1 V (vs. RHE), and a CO / H2 ratio of approximately 1:1, demonstrating high syngas production performance.

[0039] It should be noted that the above embodiments are only used to illustrate the core principles of the present invention and are not exhaustive in all details. Those skilled in the art can adjust and optimize the synthesis conditions, raw material ratios and process parameters according to the contents of this specification to meet different application requirements. The scope of protection of the present invention is subject to the claims and their equivalents.

Claims

1. A method for preparing NiPPc electrocatalyst with added Co element, characterized in that: NiPPc was prepared by a solvothermal method: 40 mg of nickel acetate tetrahydrate and 90 mg of 1,2,4,5-tetracyanobenzene were dispersed in 35 ml of ethanol solution and stirred for 10 minutes. After stirring, the mixture was ultrasonicated for 30 minutes. After uniform dispersion, the mixture was placed in a reactor at 100°C for reaction. After the reaction was complete and naturally cooled, the mixture was washed with ethanol solution and air-dried to obtain 1.63 g of NiPPc sample. Preparation of Co@NiPPc: Cobalt acetate tetrahydrate with different mass fractions was added based on the nickel content, and dispersed in 35 ml of ethanol solution with 40 mg of nickel acetate tetrahydrate and 90 mg of 1,2,4,5-tetracyanobenzene respectively. The mixture was stirred for 10 min, and ultrasonicated for 30 min after stirring. After uniform dispersion, the mixture was placed in a reactor for reaction. After the reaction was complete and naturally cooled, it was washed with ethanol solution and dried with air to obtain the sample Co@NiPPc.

2. According to claim 1, a method for preparing NiPPc electrocatalyst with added Co element, characterized in that: Based on the nickel content, different mass fractions of nickel were added, namely 10%, 30%, 50%, 70% and 90%.

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