CoTNPc / F-HCS electrocatalyst as well as preparation method and application thereof

Abstract

The invention discloses a CoTNPc / F-HCS electrocatalyst as well as a preparation method and application thereof, and belongs to the technical field of electrochemical CO2 reduction materials. The preparation method comprises the following steps: mixing and grinding 4-nitrophthalonitrile, anhydrous cobalt chloride, urea and ammonium molybdate tetrahydrate, and carrying out solid-phase reaction to obtain cobalt tetranitro phthalocyanine; the preparation method comprises the following steps: mixing and stirring tetraethoxysilane, a solvent and dopamine hydrochloride to obtain dopamine-coated silicon dioxide spheres; ammonium fluoride and the dopamine-coated silicon dioxide spheres are mixed and ground together, and then calcination, alkali washing, suction filtration and vacuum drying are performed to obtain fluorinated hollow carbon spheres; cobalt tetranitro phthalocyanine and the fluorinated hollow carbon spheres are respectively placed in an N, N-dimethylformamide solution for ultrasonic treatment, then mixed and stirred to obtain a mixed solution, and the cobalt tetranitro phthalocyanine / fluorinated hollow carbon spheres are obtained after centrifugation and vacuum drying. The electrocatalyst synthesized by the method is of a porous spherical structure, the particle size is about 231 nm, cobalt tetranitro phthalocyanine is uniformly loaded, and the exposure area of active sites is increased. The preparation method provided by the invention has the advantages of easy control of reaction conditions, simple equipment, high conversion efficiency, low cost and the like.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of electrochemical CO2 reduction materials, and particularly relates to a CoTNPc / F-HCS electrocatalyst and a preparation method and application thereof. BACKGROUND

[0002] With the increase of industrial emissions, the combustion of fossil fuels releases a large amount of carbon dioxide, and the concentration of carbon dioxide in the air is also increasing, causing serious greenhouse effect. Finding a clean and efficient way to reduce carbon dioxide has become a problem that human development must face. Converting carbon dioxide reduction into high-value-added products (such as carbon monoxide, methanol, methane and ethylene, etc.) is a reasonable way.

[0003] Carbon monoxide is a C1 synthetic raw material that is essential in the basic chemical industry. CO produced by electrocatalytic CO2 reduction and its downstream products (such as methanol, fuel) can be referred to as "green methanol", "electronic fuel" and the like. The carbon footprint of these products in the life cycle is much lower than that of fossil-derived counterparts, and they have a huge advantage under the future carbon tax and green certification system. Compared with thermal catalysis, photocatalysis, biocatalysis, the advantages of electrocatalytic CO2 reduction are mild reaction conditions, controllable energy input, wide raw material sources, clean process, etc.

[0004] The core mechanism of electrocatalytic CO2 reduction technology is derived from the complex electrochemical process of activating and recombining CO2 molecules on the surface of the catalyst through the electrons provided by the external circuit and the protons in the electrolyte, so as to convert them into target products (such as CO, formic acid, ethylene, ethanol, etc.). In electrocatalytic CO2 reduction, the catalyst plays a core role, that is, it determines the reaction path and selectivity. The essence of the catalyst is to selectively stabilize the key intermediates in a certain specific reaction path through its unique electronic structure and surface geometry, thereby determining the selectivity of the final product.

[0005] Noble metals such as gold (Au), silver (Ag), copper (Cu), palladium (Pd) and platinum (Pt) exhibit high CO selectivity and durability, but are too expensive for large-scale expansion. Non-noble metals usually require higher overpotential to obtain equivalent CO (JCO) bias current density.

[0006] Therefore, finding an electrocatalyst that is efficient, stable, sustainable and environmentally friendly has become an important research direction for the practical level of electrocatalytic CO2 reduction. SUMMARY

[0007] Therefore, the purpose of the present application is to provide a CoTNPc / F-HCS electrocatalyst and a preparation method and application thereof.

[0008] In order to achieve the above-mentioned purpose, the present application provides the following technical solutions: In a first aspect, the present invention provides a method for preparing a CoTNPc / F-HCS electrocatalyst, comprising the following steps: S1. Mix and grind 4-nitrophthalonitrile, anhydrous cobalt chloride, urea and ammonium molybdate tetrahydrate, then heat to carry out solid-phase reaction, and then obtain cobalt tetranitrophthalocyanine by acid washing, alkali washing, filtration and vacuum drying in sequence. S2. Mix tetraethyl orthosilicate, solvent, and dopamine hydrochloride, centrifuge and collect, and vacuum dry to obtain dopamine-coated silica spheres; S3. Mix and grind the ammonium fluoride and dopamine-coated silica spheres together, then calcine them in an inert atmosphere. After calcineation, cool to room temperature, wash with sodium hydroxide in a water bath, filter, and vacuum dry to obtain fluorinated hollow carbon spheres. S4. Cobalt tetranitrophthalocyanine and fluorinated hollow carbon spheres were placed in N,N-dimethylformamide solution and sonicated, then mixed and stirred to obtain a mixed solution. After centrifugation and vacuum drying, the CoTNPc / F-HCS electrocatalyst was obtained.

[0009] Preferably, the molar ratio of 4-nitrophthalonitrile, anhydrous cobalt chloride, urea and ammonium molybdate tetrahydrate in S1 is 40:(8.0-12.0):400:(1.0-3.0).

[0010] Preferably, the solid-phase reaction in S1 is carried out at a temperature of 120-180℃ for 3-6 hours.

[0011] Preferably, in S1, acid washing uses a 1.0-2.0 mol / L hydrogen chloride solution; alkaline washing uses a 0.5-1.0 mol / L sodium hydroxide solution.

[0012] Preferably, the drying temperature in S1 is 40-90℃ and the drying time is 8-18h.

[0013] Preferably, the ratio of tetraethyl orthosilicate, solvent, and dopamine hydrochloride in S2 is 5 ml: (100-150) ml: (0.5-1) mg.

[0014] Preferably, the solvent is a mixture of water, anhydrous ethanol, and ammonia in a volume ratio of 5:20:(1.0-3.0). This invention provides a template for the subsequent preparation of fluorine-doped hollow carbon nanospheres by preparing dopamine-encapsulated silica spheres.

[0015] Preferably, the mass ratio of ammonium fluoride and dopamine-coated silica spheres in S3 is 1:(0.5-3.0).

[0016] Preferably, the calcination temperature in S3 is 700-1000℃, the time is 1-4h, and the heating rate is 2-6℃ / min.

[0017] Preferably, the concentration of sodium hydroxide solution in S3 is (1-2.5) mol / L.

[0018] Preferably, the water bath temperature in step S3 is 60-80℃ and the time is 6-12h.

[0019] Preferably, the drying temperature in step S3 is 40-90℃ and the drying time is 12h.

[0020] Preferably, the inert gas in S3 is argon.

[0021] The fluorine-doped hollow carbon nanospheres prepared in this invention provide an excellent conductive carrier for cobalt tetranitrophthalocyanine. Fluorine doping generates a large number of electrophilic carbon sites on the carbon surface, while simultaneously making the surface overall hydrophobic. The hydrophobic surface effectively repels water molecules, greatly inhibiting the electrochemical hydrogen evolution reaction and significantly improving the selectivity of CO products.

[0022] Preferably, the ratio of cobalt tetranitrophthalocyanine to N,N-dimethylformamide solution in S4 is (3-10) mg: 30 ml; the ratio of fluorinated hollow carbon spheres to N,N-dimethylformamide solution is (30-50) mg: 30 ml.

[0023] Preferably, the mass ratio of cobalt tetranitrophthalocyanine to fluorinated hollow carbon spheres in the S4 mixed solution is 1:(5-10).

[0024] Preferably, the ultrasonic dispersion time in step S4 is 1-3 hours; the drying temperature is 40-90℃, and the drying time is 8-18 hours. A supported heterogeneous catalyst is synthesized by loading cobalt tetranitrophthalocyanine as the active site onto a highly conductive support, achieving efficient electrochemical CO2 reduction to CO.

[0025] The present invention also provides a CoTNPc / F-HCS electrocatalyst, which is prepared by the above-described preparation method.

[0026] This invention also provides the application of the above-mentioned CoTNPc / F-HCS electrocatalyst in electrocatalytic carbon dioxide reduction.

[0027] The present invention also provides the application of the above-mentioned CoTNPc / F-HCS electrocatalyst in an electrochemical carbon dioxide reduction electrode.

[0028] This invention also provides a method for preparing the above-mentioned electrochemical carbon dioxide reduction electrode, comprising the following steps: The CoTNPc / F-HCS catalyst, isopropanol, deionized water and Nafion solution were mixed evenly and ultrasonically dispersed to obtain a dispersion. The dispersion was evenly dropped onto carbon paper and allowed to air dry naturally before being used as the working electrode.

[0029] Preferably, the mass-to-volume ratio of the CoTNPc / F-HCS catalyst, isopropanol, deionized water, and Nafion solution is (3-10) mg:(800-1000) μL:150 μL:(50-100) μL; the ultrasonic dispersion time is 30-60 min; and the catalyst loading on the working electrode is 0.2-1.0 mg / cm³. 2 .

[0030] The present invention also provides an electrochemical carbon dioxide reduction device, which consists of a gas chromatograph, an electrochemical workstation, an electrolytic cell, a working electrode, a counter electrode and a reference electrode; The working electrode uses the aforementioned CoTNPc / F-HCS electrocatalyst. The reference electrode is a silver / silver chloride electrode. The counter electrode is a graphite rod electrode. The proton exchange membrane is a Nafion 117 proton exchange membrane; The electrolyte is a KHCO3 solution; An H-type electrolytic cell was used as a reactor to carry out an electrocatalytic carbon dioxide reduction reaction in an electrochemical workstation.

[0031] It contains at least the following beneficial technical effects: 1. The preparation method of this invention includes the synthesis of cobalt tetranitrophthalocyanine and fluorine-doped hollow carbon nanospheres, and the preparation of a supported catalyst on which cobalt tetranitrophthalocyanine is loaded onto fluorine-doped hollow carbon nanospheres. Specifically, cobalt tetranitrophthalocyanine is synthesized via a high-temperature solid-state reaction, and the fluorine-doped hollow carbon nanospheres are obtained through high-temperature carbonization. Then, cobalt tetranitrophthalocyanine and fluorine-doped hollow carbon nanospheres are separately added to an N,N dimethylformamide solution and sonicated, followed by mixing, stirring, centrifugation, and vacuum drying to obtain a solid catalyst powder. This method is simple and easy to implement, and by effectively controlling the synthesis conditions of the catalyst, a CoTNPc / F-HCS catalyst can be obtained.

[0032] 2. The CoTNPc / F-HCS electrocatalyst synthesized in this invention has a porous spherical structure with a particle size of approximately 231 nm. It is uniformly loaded with cobalt tetranitrophthalocyanine, which increases the exposed area of ​​the active sites.

[0033] 3. The preparation method of the present invention has the advantages of easy control of reaction conditions, simple equipment, high conversion efficiency and low cost. Attached Figure Description

[0034] Figure 1 The XRD pattern of the CoTNPc / F-HCS electrocatalyst prepared in Example 1; Figure 2 TEM image of the CoTNPc / F-HCS electrocatalyst prepared in Example 1; Figure 3 A physical image of the equipment used for electrochemical CO2 reduction of the CoTNPc / F-HCS electrocatalyst prepared in Example 1; Figure 4 Linear scan curve of the CoTNPc / F-HCS electrocatalyst prepared in Example 1 in CO2-saturated 0.5MKHCO3; Figure 5 The CO faradaic efficiency diagram of the CoTNPc / F-HCS electrocatalyst prepared in Example 1 at -0.8V (Vvs.RHE). Detailed Implementation

[0035] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as a limitation of the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0036] It should be understood that the terminology used in this invention is merely for describing particular embodiments and is not intended to limit the invention. Furthermore, with respect to numerical ranges in this invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Every smaller range between any stated value or intermediate value within a stated range, and any other stated value or intermediate value within said range, is also included in this invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0037] Unless otherwise stated, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. While only preferred methods and materials have been described herein, any methods and materials similar or equivalent to those described herein may be used in the implementation or testing of this invention. All references to this specification are incorporated by way of citation to disclose and describe methods and / or materials associated with those references. In the event of any conflict with any incorporated reference, the content of this specification shall prevail.

[0038] Various modifications and variations can be made to the specific embodiments described in this specification without departing from the scope or spirit of the invention, as will be apparent to those skilled in the art. Other embodiments derived from this specification will also be obvious to those skilled in the art. This application specification and embodiments are merely exemplary.

[0039] The terms “include,” “including,” “have,” “contain,” etc., used in this article are all open-ended terms, meaning that they include but are not limited to.

[0040] Unless otherwise specified, "room temperature" and "normal temperature" in this invention refer to 25±2℃.

[0041] Unless otherwise specified, all raw materials or instruments used in the following embodiments of the present invention are commercially available.

[0042] Example 1 The preparation method of CoTNPc / F-HCS electrocatalyst specifically includes the following steps: (1) 10 mmol of 4-nitrophthalonitrile, 2 mmol of anhydrous cobalt chloride, 100 mmol of urea and 0.5 mmol of ammonium molybdate tetrahydrate were mixed and ground, and placed at 160 °C for solid-phase reaction for five hours. The mixture was then washed with 70 ml of 1 mol / L hydrochloric acid aqueous solution, alkali washed with 70 ml of 1 mol / L sodium hydroxide aqueous solution, filtered, and vacuum dried at 60 °C for 12 hours to obtain cobalt tetranitrophthalocyanine. (2) Add 5 ml of tetraethyl orthosilicate to a mixed solution of 25 ml of water, 100 ml of anhydrous ethanol and 5 ml of ammonia, then add 0.6 g of dopamine hydrochloride, stir for a period of time, centrifuge at 8000 r / min, and vacuum dry at 60 °C for 12 h to obtain dopamine-coated silica spheres. (3) Grind and mix ammonium fluoride and carbon spheres at a mass ratio of 1:1 and calcine at 800°C. After cooling to room temperature, wash with 200 ml of 2.5 mol / L sodium hydroxide solution in a water bath at 90°C, filter, and vacuum dry at 60°C to obtain fluorinated hollow carbon spheres. (4) Place 5 mg of tetranitrophthalocyanine cobalt and 30 mg of fluorinated hollow carbon spheres in 30 ml of N,N-dimethylformamide solution and sonicate. Then mix and stir for 24 h. Collect by centrifugation at 8000 r / min and vacuum drying at 60 °C to obtain CoTNPc / F-HCS.

[0043] Example 2 The preparation method of CoTNPc / F-HCS electrocatalyst specifically includes the following steps: (1) 10 mmol of 4-nitrophthalonitrile, 3 mmol of anhydrous cobalt chloride, 100 mmol of urea and 0.25 mmol of ammonium molybdate tetrahydrate were mixed and ground, and placed at 160 °C for solid-phase reaction for five hours. The mixture was then washed with 70 ml of 1 mol / L hydrochloric acid aqueous solution, alkali washed with 70 ml of 1 mol / L sodium hydroxide aqueous solution, filtered, and vacuum dried at 40 °C for 18 hours to obtain cobalt tetranitrophthalocyanine. (2) Add 5 ml of tetraethyl orthosilicate to a mixed solution of 25 ml of water, 150 ml of anhydrous ethanol and 5 ml of ammonia, then add 1 g of dopamine hydrochloride, stir for a period of time, centrifuge at 8000 r / min, and vacuum dry at 60 °C for 12 h to obtain dopamine-coated silica spheres. (3) Grind and mix ammonium fluoride and carbon spheres at a mass ratio of 1:2 and calcine at 1000℃. After cooling to room temperature, wash with 200ml of 2.5mol / L sodium hydroxide solution in a water bath at 90℃, filter, and vacuum dry at 60℃ to obtain fluorinated hollow carbon spheres. (4) Place 5 mg of cobalt tetranitrophthalocyanine and 50 mg of fluorinated hollow carbon spheres in 30 ml of N,N-dimethylformamide solution and sonicate. Then mix and stir for 24 h. Collect by centrifugation at 8000 r / min and vacuum drying at 60 °C to obtain CoTNPc / F-HCS.

[0044] Example 3 The preparation method of CoTNPc / F-HCS electrocatalyst specifically includes the following steps: (1) 10 mmol of 4-nitrophthalonitrile, 2.5 mmol of anhydrous cobalt chloride, 100 mmol of urea and 0.5 mmol of ammonium molybdate tetrahydrate were mixed and ground, and placed at 160 °C for solid-phase reaction for five hours. The mixture was then washed with 70 ml of 1 mol / L hydrochloric acid aqueous solution, alkali washed with 70 ml of 1 mol / L sodium hydroxide aqueous solution, filtered, and vacuum dried at 60 °C for 12 hours to obtain cobalt tetranitrophthalocyanine. (2) Add 5 ml of tetraethyl orthosilicate to a mixed solution of 25 ml of water, 125 ml of anhydrous ethanol and 4 ml of ammonia, then add 0.5 g of dopamine hydrochloride, stir for a period of time, centrifuge at 8000 r / min, and vacuum dry at 60 °C for 12 h to obtain dopamine-coated silica spheres. (3) Grind and mix ammonium fluoride and carbon spheres at a mass ratio of 1:1 and calcine at 700°C. After cooling to room temperature, wash with 200 ml of 2.5 mol / L sodium hydroxide solution in a water bath at 90°C, filter, and vacuum dry at 60°C to obtain fluorinated hollow carbon spheres. (4) Place 5 mg of tetranitrophthalocyanine cobalt and 25 mg of fluorinated hollow carbon spheres in 30 ml of N,N-dimethylformamide solution and sonicate. Then mix and stir for 24 h. Collect by centrifugation at 8000 r / min and vacuum drying at 60 °C to obtain CoTNPc / F-HCS.

[0045] Comparative Example 1 The CoTNPc / F-HCS precursor was prepared in the same way as in Example 1, except that step (1) was only reacted for 1 hour.

[0046] Comparative Example 2 The CoTNPc / F-HCS precursor was prepared in the same way as in Example 1, except that ammonium fluoride was not added in step (3).

[0047] Comparative Example 3 The CoTNPc / F-HCS precursor was prepared in the same way as in Example 1, except that step (4) involved stirring for only 1 hour.

[0048] Experimental Example 1 Performance testing 1. XRD and TEM characterization Depend on Figure 1 As can be seen, Example 1 successfully synthesized the CoTNPc / F-HCS electrocatalyst. Depend on Figure 2 It can be seen that the CoTNPc / F-HCS electrocatalyst has a spherical morphology, with cobalt tetranitrophthalocyanine uniformly dispersed on the surface of the fluorinated hollow carbon nanospheres. The loading of CoTNPc did not change the morphology of the fluorinated hollow carbon nanospheres.

[0049] 2. Electrochemical CO2 Reduction Experiment The CoTNPc / F-HCS working electrode material prepared in Example 1 was used in electrochemical CO2 reduction.

[0050] like Figure 3 As shown, the electrochemical CO2 reduction device mainly adopts a three-electrode system, consisting of an electrochemical workstation, an electrolytic cell, a gas chromatograph, a working electrode, a counter electrode, and a reference electrode; a carbon rod is used as the counter electrode, and silver / silver oxide is used as the reference electrode. The working electrode is made of carbon paper with the CoTNPc / F-HCS catalyst prepared in Example 1, specifically: (1) 5 mg of the CoTNPc / F-HCS electrocatalyst prepared in Example 1 is mixed evenly with 800 μL of isopropanol, 150 μL of deionized water, and 50 μL of Nafion solution, and ultrasonically dispersed for 50 min to obtain a dispersion; (2) 100 μL of the dispersion is evenly dropped three times in a 4:3:3 ratio onto a 1×1 cm 2 The catalyst was placed on carbon paper and allowed to air dry naturally before being used as the working electrode, with a catalyst loading of 0.5 mg / cm³. 2 (The area immersed in the electrolyte is 1 cm²) 2 The electrolyte was a KHCO3 solution with a concentration of 0.5 mol / L, and pure CO2 was introduced to saturate it for 40 min. The main method for testing the electrochemical CO2 reduction performance is the linear sweep voltammetry, with the following detection parameters: settling time is 10s, scan rate is 5mV / s, and scan range is -1.4 to 0V (V vs. RHE). The results are as follows Figures 4-5 As shown. Depend on Figure 4 It can be seen that the CoTNPc / F-HCS electrocatalyst prepared in Example 1 has an initial potential of only -0.4V (Vvs.RHE) for CO2, and a local current density of -67.26 mA / cm at a voltage of -1.4V (Vvs.RHE), exhibiting high electrochemical activity.

[0051] Depend on Figure 5 It can be seen that the CoTNPc / F-HCS electrocatalyst prepared in Example 1 has a CO Faradaic efficiency of 93.8% at a voltage of -0.8V (Vvs.RHE), exhibiting high CO conversion activity.

[0052] Examples 2-3 and Comparative Examples 1-3 were tested according to the above method, and the performance is shown in Table 1.

[0053] Table 1 The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing a CoTNPc / F-HCS electrocatalyst, characterized in that, Includes the following steps: S1. Mix and grind 4-nitrophthalonitrile, anhydrous cobalt chloride, urea and ammonium molybdate tetrahydrate, then heat to carry out solid-phase reaction, and then obtain cobalt tetranitrophthalocyanine by acid washing, alkali washing, filtration and vacuum drying in sequence. S2. Mix tetraethyl orthosilicate, solvent, and dopamine hydrochloride, centrifuge and collect, and vacuum dry to obtain dopamine-coated silica spheres; S3. Mix and grind the ammonium fluoride and dopamine-coated silica spheres together, then calcine them in an inert atmosphere. After calcineation, cool to room temperature, wash with sodium hydroxide in a water bath, filter, and vacuum dry to obtain fluorinated hollow carbon spheres. S4. Cobalt tetranitrophthalocyanine and fluorinated hollow carbon spheres were placed in N,N-dimethylformamide solution and sonicated, then mixed and stirred to obtain a mixed solution. After centrifugation and vacuum drying, the CoTNPc / F-HCS electrocatalyst was obtained.

2. The preparation method according to claim 1, characterized in that, The molar ratio of 4-nitrophthalonitrile, anhydrous cobalt chloride, urea and ammonium molybdate tetrahydrate in S1 is 40:(8.0-12.0):400:(1.0-3.0).

3. The preparation method according to claim 1, characterized in that, The ratio of tetraethyl orthosilicate, solvent, and dopamine hydrochloride in S2 is 5ml:(100-150)ml:(0.5-1)mg.

4. The preparation method according to claim 6, characterized in that, The solvent is a mixture of water, anhydrous ethanol and ammonia in a volume ratio of 5:20:(1.0-3.0).

5. The preparation method according to claim 1, characterized in that, The mass ratio of ammonium fluoride and dopamine-coated silica spheres in S3 is 1:(0.5-3.0).

6. The preparation method according to claim 1, characterized in that, The calcination temperature in S3 is 700-1000℃, the time is 1-4h, and the heating rate is 2-6℃ / min.

7. The preparation method according to claim 1, characterized in that, The mass ratio of cobalt tetranitrophthalocyanine and fluorinated hollow carbon spheres in the S4 mixed solution is 1:(5-10).

8. A CoTNPc / F-HCS electrocatalyst, characterized in that, It is prepared by the preparation method according to any one of claims 1-15.

9. The application of the CoTNPc / F-HCS electrocatalyst according to claim 8 in electrocatalytic carbon dioxide reduction.

10. The application of the CoTNPc / F-HCS electrocatalyst according to claim 8 in an electrochemical carbon dioxide reduction electrode; The preparation method of the electrochemical carbon dioxide reduction electrode includes the following steps: The CoTNPc / F-HCS catalyst of claim 8, isopropanol, deionized water and Nafion solution were mixed evenly and ultrasonically dispersed to obtain a dispersion. The dispersion was evenly dropped onto carbon paper and allowed to air dry naturally before being used as the working electrode.

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