Preparation method of complex-derived CNT-Pd nano-catalyst and application of complex-derived CNT-Pd nano-catalyst in preparation of CO through electrocatalytic reduction of CO2

Abstract

The invention discloses a preparation method of a complex-derived CNT-Pd nano-catalyst and application of the complex-derived CNT-Pd nano-catalyst in preparation of CO through electrocatalytic reduction of CO2, and relates to the technical field of preparation of palladium nano-catalysts. The invention aims to solve the problems of poor catalytic performance and low atom utilization rate of the traditional noble metal Pd-based catalyst for electrocatalytic reduction of CO2 into CO. According to the preparation method, rich defect sites are constructed on the surface of the carbon nano tube through the activation step, so that the structural stability of the Pd nano particles is improved, the small-size noble metal Pd nano particles are uniformly dispersed, and the atom utilization rate of noble metal elements is effectively increased; the C element in the carbon nano tube has high electronegativity, can effectively change the electronic structure of the Pd nano particle after being compounded with the Pd nano particle, and can effectively enhance the catalytic performance of the catalyst for reducing CO2 to prepare CO. The invention can obtain the preparation method of the complex-derived CNT-Pd nano-catalyst and the application of the complex-derived CNT-Pd nano-catalyst in preparation of CO by electrocatalytic reduction of CO2.

Description

Technical Field

[0001] The invention relates to the technical field of palladium nanocatalyst preparation, and in particular to a method for preparing a complex-derived CNT-Pd nanocatalyst and application of the catalyst in electrocatalytic reduction of CO2 to produce CO. Background Art

[0002] With the rapid development of science and technology, human activities rely more on the exploitation and utilization of natural resources. Non-renewable fossil energy such as coal, oil and natural gas is the basis for driving the rapid development of society. The rapid consumption of fossil energy will not only trigger a worldwide energy crisis, but the excessive emission of CO2 will also seriously threaten the sustainable development of mankind. my country is the country with the largest population in the world and a major carbon emitter. It faces many challenges in greenhouse gas emission reduction and CO2 resource conversion. In the technical background of developing new technologies for CO2 conversion and realizing artificial carbon cycle, reducing CO2 to energy chemicals by electrocatalysis has broad prospects for alleviating energy crisis, reducing atmospheric CO2 concentration and realizing artificial carbon cycle.

[0003] The electrochemical reduction of CO2 mainly includes the activation and hydrogenation of CO2, which is a multi-step reaction involving the processes of gaining and losing electrons and adsorption and desorption. The electrochemical reduction of CO2 can undergo multi-electron transfer processes such as 2-electron, 4-electron, 6-electron and 8-electron. The products are not unique, and the more common products are HCOOH, CO, CH3OH, CH4, etc. How to improve the selectivity of CO2 reduction to a specific product, reduce the occurrence of side reactions, and improve the utilization rate of electric energy are the primary issues to be considered in the development of new electrocatalytic materials. Considering factors such as market electricity prices and technical and economic levels, CO is considered to be the most cost-effective product. CO can be used as a fuel or as a raw gas for the Fischer-Tropsch reaction. Among the reported catalytic materials, precious metals Ag and Au have become a hot topic of research because of their high Faraday efficiency and selectivity in the conversion of CO2 to CO. The current methods for the preparation of precious metal catalysts mainly focus on regulating the morphology, size, defect sites and alloy components of precious metals, and the bottleneck problem of poor activity of precious metal catalytic materials still exists. In addition, the preparation of precious metal-based catalysts requires many steps, complex operations, low atomic utilization, and is difficult to achieve large-scale preparation, and the catalytic performance is also difficult to guarantee.

[0004] Compared with other elements, Pd has higher selectivity for CO2 reduction to CO, but Pd reserves are scarce, it is a precious metal element, and has a high market price. Improving CO2 reduction performance while improving atomic utilization and reducing costs is the key to Pd-based catalyst research. Therefore, it is urgent to improve the catalytic activity of Pd-based catalysts, achieve efficient electrocatalytic reduction of CO2 to CO, and promote the industrial application of Pd-based catalysts. Summary of the invention

[0005] The purpose of the present invention is to solve the problems of poor catalytic performance and low atomic utilization rate of traditional noble metal Pd-based catalysts in the electrocatalytic reduction of CO2 to CO, as well as complex preparation process and high production cost, and to provide a method for preparing a complex-derived CNT-Pd nanocatalyst and its application in the electrocatalytic reduction of CO2 to CO.

[0006] A method for preparing a complex-derived CNT-Pd nanocatalyst is carried out according to the following steps:

[0007] Step S1: Activating carbon nanotubes;

[0008] Adding carbon nanotubes to a nitric acid solution, mixing and stirring evenly, and centrifuging the mixture; then washing the centrifuged carbon nanotubes with ultrapure water and centrifuging again until the pH of the supernatant after centrifugation is 6 to 7, thereby obtaining washed carbon nanotubes; fully drying the washed carbon nanotubes, and then performing annealing treatment to obtain activated carbon nanotubes;

[0009] Step S2: preparing a precursor electrode;

[0010] The activated carbon nanotubes, Pd-based complex, Nafion solution and solvent obtained in step S1 are mixed and ultrasonicated to obtain a uniform mixed solution; the uniform mixed solution is sprayed on carbon paper and then dried to obtain a precursor working electrode; the mass ratio of the activated carbon nanotubes to the Pd-based complex is (0.1-40): (0.1-40);

[0011] Step S3: preparing a complex-derived CNT-Pd nanocatalyst;

[0012] The precursor working electrode obtained in step S2 is placed in the cathode area of ​​the "H" type electrolytic cell as a cathode. The cathode area and the anode area of ​​the "H" type electrolytic cell are separated by a Nafion proton exchange membrane. The cathode area is energized under the protection of an inert gas to react to obtain a complex-derived CNT-Pd nanocatalyst.

[0013] The application of a complex-derived CNT-Pd nanocatalyst prepared by the above method in the electrocatalytic reduction of CO2 to CO, wherein the complex-derived CNT-Pd nanocatalyst is used as a working electrode for the electrocatalytic reduction of CO2 to CO, and the specific application steps are as follows:

[0014] Step 1: Assembly:

[0015] An "H" type electrolytic cell with a three-electrode system is used, a carbon rod is placed in the anode chamber as a counter electrode, a saturated calomel electrode is placed in the cathode chamber as a reference electrode, and a Nafion proton exchange membrane is used to separate the cathode chamber from the anode chamber; the gas zone and the liquid zone of the cathode chamber are separated by a gas diffusion electrode, and then potassium bicarbonate with a concentration of 0.1 to 5 mol / L is added as an electrolyte into the cathode zone, and then a seal is used to seal the cathode zone, thereby obtaining a device for electrocatalytic reduction of CO2 to produce CO;

[0016] Step 2: Electrocatalytic reduction:

[0017] The CO2 gas is introduced into the electrolyte in the cathode region, and the flow rate of the CO2 gas is controlled to be 10 to 30 mL / min; at a voltage of -1.1 V to -2.1 V, the electrocatalytic reduction of CO2 to produce CO is completed.

[0018] Beneficial effects of the present invention:

[0019] (1) The preparation method of the complex-derived CNT-Pd nanocatalyst of the present invention constructs abundant defect sites on the surface of carbon nanotubes through an activation step, which serve as attachment points of Pd nanoparticles, thereby increasing the structural stability of the Pd nanoparticles, making small-sized precious metal Pd nanoparticles evenly dispersed, and effectively increasing the atomic utilization rate of the precious metal element; the C element in the carbon nanotubes has a high electronegativity, and after being combined with the Pd nanoparticles, it can effectively change the electronic structure of the Pd nanoparticles, and can effectively enhance the catalytic performance of the catalyst in reducing CO2 to CO.

[0020] (2) The present invention adopts a simple electrochemical synthesis method to prepare a complex-derived CNT-Pd nanocatalyst having a uniform Pd nanoparticle size, high catalytic activity and catalytic stability; the catalyst preparation cost of this method is low, the utilization rate of precious metal atoms is high, and it can be used for the efficient reduction of CO2 to produce CO with higher economic benefits, and has broad application prospects.

[0021] The invention can obtain a preparation method of a complex-derived CNT-Pd nanocatalyst and application of the catalyst in electrocatalytic reduction of CO2 to produce CO. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 A scanning electron microscope photograph showing the complex-derived CNT-Pd nanocatalyst prepared in Example 1;

[0023] Figure 2 A transmission electron micrograph of the complex-derived CNT-Pd nanocatalyst prepared in Example 1;

[0024] Figure 3A high-resolution transmission electron micrograph of the complex-derived CNT-Pd nanocatalyst prepared in Example 1;

[0025] Figure 4 represents the HAADF-STEM image of the complex-derived CNT-Pd nanocatalyst prepared in Example 1;

[0026] Figure 5 represents X-ray diffraction spectra, a represents the X-ray diffraction spectrum of the complex-derived CNT-Pd nanocatalyst prepared in Example 1, and b represents the X-ray diffraction spectrum of carbon paper;

[0027] Figure 6 represents an X-ray photoelectron spectrum of the complex-derived CNT-Pd nanocatalyst prepared in Example 1;

[0028] Figure 7 A graph showing the Faradaic efficiency of the electrocatalytic reduction of CO2 to CO by the complex-derived CNT-Pd nanocatalyst prepared in Example 1;

[0029] Figure 8 A current density diagram showing the electrocatalytic reduction of CO2 to CO by the complex-derived CNT-Pd nanocatalyst prepared in Example 1. DETAILED DESCRIPTION

[0030] Specific implementation method 1: This implementation method is a preparation method of a complex-derived CNT-Pd nanocatalyst, which is carried out according to the following steps:

[0031] Step S1: Activating carbon nanotubes;

[0032] Adding carbon nanotubes to a nitric acid solution, mixing and stirring evenly, and centrifuging the mixture; then washing the centrifuged carbon nanotubes with ultrapure water and centrifuging again until the pH of the supernatant after centrifugation is 6 to 7, thereby obtaining washed carbon nanotubes; fully drying the washed carbon nanotubes, and then performing annealing treatment to obtain activated carbon nanotubes;

[0033] Step S2: preparing a precursor electrode;

[0034] The activated carbon nanotubes, Pd-based complex, Nafion solution and solvent obtained in step S1 are mixed and ultrasonicated to obtain a uniform mixed solution; the uniform mixed solution is sprayed on carbon paper and then dried to obtain a precursor working electrode; the mass ratio of the activated carbon nanotubes to the Pd-based complex is (0.1-40): (0.1-40);

[0035] Step S3: preparing a complex-derived CNT-Pd nanocatalyst;

[0036] The precursor working electrode obtained in step S2 is placed in the cathode area of ​​the "H" type electrolytic cell as a cathode. The cathode area and the anode area of ​​the "H" type electrolytic cell are separated by a Nafion proton exchange membrane. The cathode area is energized under the protection of an inert gas to react to obtain a complex-derived CNT-Pd nanocatalyst.

[0037] Specific implementation method 2: The difference between this implementation method and specific implementation method 1 is that in step S1, carbon nanotubes are added to a nitric acid solution, placed in a water bath for mixing and stirring, the water bath temperature is 50-100° C., and the water bath time is 6-24 hours.

[0038] The other steps are the same as those in the first specific implementation.

[0039] Specific implementation method three: This implementation method is different from specific implementation methods one or two in that the ratio of the mass of the carbon nanotubes described in step S1 to the volume of the nitric acid solution is (0.1-10) g: (5-500) mL, and the concentration of the nitric acid solution is 8-15 mol / L.

[0040] The other steps are the same as those in the first or second embodiment.

[0041] Specific implementation method 4: The difference between this implementation method and specific implementation methods 1 to 3 is that in step S1, the dried carbon nanotubes are placed in a tubular furnace for annealing, the annealing temperature is 200-400° C., and the annealing time is 6-24 hours.

[0042] The other steps are the same as those in Specific Embodiments 1 to 3.

[0043] Specific embodiment 5: The difference between this embodiment and specific embodiments 1 to 4 is that the ratio of the mass of the activated carbon nanotubes, the volume of the Nafion solution and the volume of the solvent described in step S2 is (0.1-40) mg: (0.4-160) μL: (0.025-10) mL.

[0044] The other steps are the same as those in Specific Embodiments 1 to 4.

[0045] Specific embodiment six: The difference between this embodiment and specific embodiments one to five is that the Pd-based complex described in step S2 is bis(acetonitrile)palladium dichloride, bis(cyanobenzene)palladium dichloride, bistriphenylphosphinepalladium dichloride or allylpalladium chloride dimer, and the solvent is methanol, ethanol, acetone, propanol or isopropanol.

[0046] The other steps are the same as those in Specific Embodiments 1 to 5.

[0047] Specific embodiment 7: The difference between this embodiment and specific embodiments 1 to 6 is that the ultrasonic time in step S2 is 10 to 180 minutes.

[0048] The other steps are the same as those in Specific Embodiments 1 to 6.

[0049] Specific embodiment 8: The difference between this embodiment and specific embodiments 1 to 7 is that the area ratio of the uniform mixed liquid to the carbon paper in step S2 is (0.01-1) mL: 1 cm 2 ; In step S2, the drying temperature is 20-80°C and the drying time is 5-300min.

[0050] The other steps are the same as those in Specific Embodiments 1 to 7.

[0051] Specific embodiment nine: The difference between this embodiment and specific embodiments one to eight is that: in step S3, a graphite or platinum electrode is used as an anode in the anode area of ​​the "H" type electrolytic cell, a saturated calomel electrode is placed in the cathode area as a reference electrode, and a carbonate electrolyte is added to both the cathode area and the anode area; the carbonate electrolyte is potassium carbonate, sodium carbonate, potassium bicarbonate or sodium bicarbonate, and the concentration is 0.1 to 5 mol / L; the power-on reaction time is 1 to 180 min, and the power-on voltage is -1V to -2V; the inert gas is nitrogen or argon.

[0052] The other steps are the same as those in Specific Embodiments 1 to 8.

[0053] Specific embodiment 10: In this embodiment, a complex-derived CNT-Pd nanocatalyst prepared by the above method is used in the electrocatalytic reduction of CO2 to CO. The complex-derived CNT-Pd nanocatalyst is used as a working electrode for the electrocatalytic reduction of CO2 to CO. The specific application steps are as follows:

[0054] Step 1: Assembly:

[0055] An "H" type electrolytic cell with a three-electrode system is used, a carbon rod is placed in the anode chamber as a counter electrode, a saturated calomel electrode is placed in the cathode chamber as a reference electrode, and a Nafion proton exchange membrane is used to separate the cathode chamber from the anode chamber; the gas zone and the liquid zone of the cathode chamber are separated by a gas diffusion electrode, and then potassium bicarbonate with a concentration of 0.1 to 5 mol / L is added as an electrolyte into the cathode zone, and then a seal is used to seal the cathode zone, thereby obtaining a device for electrocatalytic reduction of CO2 to produce CO;

[0056] Step 2: Electrocatalytic reduction:

[0057] The CO2 gas is introduced into the electrolyte in the cathode region, and the flow rate of the CO2 gas is controlled to be 10 to 30 mL / min; at a voltage of -1.1 V to -2.1 V, the electrocatalytic reduction of CO2 to produce CO is completed.

[0058] The following examples are used to verify the beneficial effects of the present invention:

[0059] Example 1: A method for preparing a complex-derived CNT-Pd nanocatalyst, comprising the following steps:

[0060] Step S1: Activating carbon nanotubes;

[0061] 2 g of carbon nanotubes (CNT) were added to 100 mL of 9 mol / L nitric acid solution, placed in a water bath, and heated in a water bath at 90°C for 12 h; the mixed solution was centrifuged at high speed to separate the carbon nanotubes from the solution; the centrifuged carbon nanotubes were then washed with ultrapure water and centrifuged again, and the operation was repeated until the pH of the supernatant after centrifugation was 7 to obtain washed carbon nanotubes; the washed carbon nanotubes were fully dried, and then the dried carbon nanotubes were placed in a tubular furnace and annealed at 300°C for 12 h to obtain activated carbon nanotubes;

[0062] Step S2: weighing;

[0063] Weigh 20 mg of activated carbon nanotubes, 20 mg of bis(acetonitrile)palladium dichloride, 160 μL of Nafion solution, and 5 mL of isopropanol respectively;

[0064] Step S3: preparing a precursor electrode;

[0065] The activated carbon nanotubes, bis(acetonitrile)palladium dichloride, Nafion solution and isopropanol were weighed and mixed, and ultrasonicated for 30 minutes to obtain a uniform mixed solution; the uniform mixed solution was sprayed on a 100 cm 2 on carbon paper, and then dried at 80 °C for 60 min to obtain a precursor working electrode;

[0066] Step S4: preparing a complex-derived CNT-Pd nanocatalyst;

[0067] The precursor working electrode is placed in the cathode area of ​​an "H" type electrolytic cell as a cathode, a graphite or platinum electrode is used as an anode in the anode area, a saturated calomel electrode is placed in the cathode area as a reference electrode, and a Nafion proton exchange membrane is used to separate the cathode area and the anode area; a potassium bicarbonate electrolyte with a concentration of 0.5 mol / L is added to both the cathode area and the anode area, and the cathode area is powered on at a voltage of -1.2 V under inert gas protection for 30 minutes to obtain a complex-derived CNT-Pd nanocatalyst.

[0068] Figure 1 The scanning electron microscope photograph of the complex-derived CNT-Pd nanocatalyst prepared in Example 1 is shown; Figure 1As shown, the morphology of the catalyst at the micron scale is a linear structure of cross-linked carbon nanotubes, and no obvious metal crystals are found, indicating that the carbon nanotubes in the CNT-Pd nanocatalyst prepared by the complex derivatization method maintain the original physical structure and will not be destroyed, and the particle size of the formed Pd nanoparticles is below the micron scale.

[0069] Figure 2 The transmission electron micrograph of the complex-derived CNT-Pd nanocatalyst prepared in Example 1 is shown; Figure 2 As shown, darker Pd metal nanocrystals with a particle size of less than 10 nanometers are distributed on the surface of the carbon nanotubes, and the Pd nanocrystals are evenly distributed on the carbon nanotube carrier. No obvious nanoparticle agglomeration phenomenon is found, indicating that there are enough carbon defects on the surface of the activated carbon nanotubes, which can provide sufficient anchoring points for the Pd atoms released by the Pd-based complex and limit the further growth of the nanocrystals to form Pd nanocrystals with uniform particle size distribution.

[0070] Figure 3 A high-resolution transmission electron micrograph of the complex-derived CNT-Pd nanocatalyst prepared in Example 1; Figure 3 As shown, after the activation step, the surface of the carbon nanotubes is relatively rough and rich in defect sites. The areas with dense lattice stripes are Pd nanocrystals, and the Pd nanocrystals grow closely in the defect sites of the carbon nanotubes. This shows that the complex derivatization method used in this embodiment can effectively load small-sized Pd nanocrystals on the carbon nanotube carrier, ensuring that the catalyst has excellent conductivity, and the smaller Pd nanocrystals also make the catalyst have a higher utilization rate of precious metal Pd atoms.

[0071] Figure 4 The HAADF-STEM image of the complex-derived CNT-Pd nanocatalyst prepared in Example 1 is shown; Figure 4 As shown, high-brightness Pd nanocrystals are evenly dispersed on the carbon nanotubes, and the particle size is about 5 nm, which further illustrates that the CNT-Pd nanocatalyst material is successfully prepared in this embodiment.

[0072] Figure 5 represents X-ray diffraction spectra, a represents the X-ray diffraction spectrum of the complex-derived CNT-Pd nanocatalyst prepared in Example 1, and b represents the X-ray diffraction spectrum of carbon paper; Figure 5 As shown, the complex-derived CNT-Pd nanocatalyst prepared in Example 1 exhibited Pd crystal diffraction peaks at 2θ values ​​of 40°, 46.5° and 68° that were different from those of the carbon paper substrate b, indicating that the complex-derived CNT-Pd nanocatalyst was successfully prepared in Example 1.

[0073] Figure 6The X-ray photoelectron spectrum of the complex-derived CNT-Pd nanocatalyst prepared in Example 1 is shown; Figure 6 As shown, obvious 1s signal peaks of C and 3d signal peaks of Pd can be seen, indicating that the complex-derived CNT-Pd catalyst was successfully prepared in this example.

[0074] Example 2: The CNT-Pd nanocatalyst derived from the complex prepared in Example 1 was used as a working electrode for electrocatalytic reduction of CO2. The area of ​​the working electrode was 1 cm×2 cm. The specific application steps were as follows:

[0075] Step 1: Assembly:

[0076] An "H" type electrolytic cell with a three-electrode system is used, a carbon rod is placed in the anode chamber as a counter electrode, a saturated calomel electrode is placed in the cathode chamber as a reference electrode, and a Nafion proton exchange membrane is used to separate the cathode chamber from the anode chamber; the gas zone and the liquid zone of the cathode chamber are separated by a gas diffusion electrode, and then potassium bicarbonate with a concentration of 0.5 mol / L is added as an electrolyte into the cathode zone, and then a seal is used to seal the cathode zone, thereby obtaining a device for electrocatalytic reduction of CO2 to produce CO;

[0077] Step 2: Electrocatalytic reduction:

[0078] CO2 gas is introduced into the electrolyte in the cathode area, and the flow rate of CO2 gas is controlled to be 10-30 mL / min; CO2 electrocatalytic reduction is carried out at a voltage of -1.1 V to -2.1 V, and online gas product analysis is performed every 10 minutes by directly flowing the gas outlet of the cathode area into the gas sampling loop of the gas chromatograph.

[0079] Figure 7 The Faraday efficiency curve of the electrocatalytic reduction of CO2 to CO by the complex-derived CNT-Pd nanocatalyst prepared in Example 1 is shown; Figure 7 As shown, at a voltage of -1.1 V, the Faradaic efficiency of the complex-derived CNT / Pd catalyst in reducing CO2 to CO exceeds 80%, and at -1.3 V, a CO Faradaic efficiency of 98% can be achieved, indicating that the catalyst prepared in Example 1 has a very high CO2 reduction performance.

[0080] Figure 8 The current density diagram of the electrocatalytic reduction of CO2 to CO by the complex-derived CNT-Pd nanocatalyst prepared in Example 1; Figure 8 As shown in the figure, the partial current density of CO of the complex-derived CNT / Pd catalyst prepared in Example 1 increases with the increasing working voltage, exceeding 25 mA / cm at a potential of -2.1 V. 2, indicating that the complex-derived CNT / Pd catalyst has excellent performance in reducing CO2 to CO.

Claims

1. A method for preparing a complex-derived CNT-Pd nanocatalyst, characterized in that The preparation method is carried out according to the following steps: Step S1: Activating carbon nanotubes; Adding carbon nanotubes to a nitric acid solution, stirring and mixing evenly, and then centrifuging the mixture; then washing the centrifuged carbon nanotubes with ultrapure water and centrifuging again until the pH of the supernatant after centrifugation is 6 to 7, thereby obtaining washed carbon nanotubes; The washed carbon nanotubes are fully dried and then annealed to obtain activated carbon nanotubes; Step S2: preparing a precursor electrode; The activated carbon nanotubes, Pd-based complex, Nafion solution and solvent obtained in step S1 are mixed and ultrasonicated to obtain a uniform mixed solution; the uniform mixed solution is sprayed on carbon paper and then dried to obtain a precursor working electrode; the mass ratio of the activated carbon nanotubes to the Pd-based complex is (0.1-40): (0.1-40); Step S3: preparing a complex-derived CNT-Pd nanocatalyst; The precursor working electrode obtained in step S2 is placed in the cathode area of ​​the "H" type electrolytic cell as a cathode. The cathode area and the anode area of ​​the "H" type electrolytic cell are separated by a Nafion proton exchange membrane. The cathode area is energized under the protection of an inert gas to react and obtain a complex-derived CNT-Pd nanocatalyst.

2. The method for preparing a complex-derived CNT-Pd nanocatalyst according to claim 1, characterized in that In step S1, the carbon nanotubes are added to the nitric acid solution, and the mixture is placed in a water bath for mixing and stirring. The water bath temperature is 50 to 100° C., and the water bath time is 6 to 24 hours.

3. The method for preparing a complex-derived CNT-Pd nanocatalyst according to claim 1 or 2, characterized in that The ratio of the mass of the carbon nanotubes to the volume of the nitric acid solution in step S1 is (0.1-10) g: (5-500) mL, and the concentration of the nitric acid solution is 8-15 mol / L.

4. The method for preparing a complex-derived CNT-Pd nanocatalyst according to claim 1, characterized in that In step S1, the dried carbon nanotubes are placed in a tube furnace for annealing at a temperature of 200 to 400° C. for a time of 6 to 24 hours.

5. The method for preparing a complex-derived CNT-Pd nanocatalyst according to claim 1, characterized in that The ratio of the mass of the activated carbon nanotubes, the volume of the Nafion solution, and the volume of the solvent described in step S2 is (0.1-40) mg: (0.4-160) μL: (0.025-10) mL.

6. The method for preparing a complex-derived CNT-Pd nanocatalyst according to claim 1, characterized in that The Pd-based complex described in step S2 is bis(acetonitrile)palladium dichloride, bis(cyanobenzene)palladium dichloride, bistriphenylphosphinepalladium dichloride or allylpalladium chloride dimer, and the solvent is methanol, ethanol, acetone, propanol or isopropanol.

7. The method for preparing a complex-derived CNT-Pd nanocatalyst according to claim 1, characterized in that The ultrasonication time in step S2 is 10 to 180 minutes.

8. The method for preparing a complex-derived CNT-Pd nanocatalyst according to claim 1, characterized in that The area ratio of the uniform mixed solution to the carbon paper in step S2 is (0.01-1) mL: 1 cm 2 ; In step S2, the drying temperature is 20-80°C and the drying time is 5-300min.

9. The method for preparing a complex-derived CNT-Pd nanocatalyst according to claim 1, characterized in that In step S3, a graphite or platinum electrode is used as an anode in the anode region of the "H" type electrolytic cell, a saturated calomel electrode is placed in the cathode region as a reference electrode, and a carbonate electrolyte is added to both the cathode region and the anode region; the carbonate electrolyte is potassium carbonate, sodium carbonate, potassium bicarbonate or sodium bicarbonate, and the concentration is 0.1 to 5 mol / L; the power-on reaction time is 1 to 180 minutes, and the power-on voltage is -1V to -2V; and the inert gas is nitrogen or argon.

10. Use of a complex-derived CNT-Pd nanocatalyst prepared by the method according to any one of claims 1 to 9 in electrocatalytic reduction of CO2 to produce CO, characterized in that The complex-derived CNT-Pd nanocatalyst is used as a working electrode for electrocatalytic reduction of CO2 to produce CO. The specific application steps are as follows: Step 1: Assembly: An "H" type electrolytic cell with a three-electrode system is used, a carbon rod is placed in the anode chamber as a counter electrode, a saturated calomel electrode is placed in the cathode chamber as a reference electrode, and a Nafion proton exchange membrane is used to separate the cathode chamber from the anode chamber; the gas zone and the liquid zone of the cathode chamber are separated by a gas diffusion electrode, and then potassium bicarbonate with a concentration of 0.1 to 5 mol / L is added as an electrolyte into the cathode zone, and then a seal is used to seal the cathode zone, thereby obtaining a device for electrocatalytic reduction of CO2 to produce CO; Step 2: Electrocatalytic reduction: The CO2 gas is introduced into the electrolyte in the cathode region, and the flow rate of the CO2 gas is controlled to be 10 to 30 mL / min; at a voltage of -1.1 V to -2.1 V, the electrocatalytic reduction of CO2 to produce CO is completed.

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