Copper / alkaline earth metal oxide composite nanocatalyst, preparation and use thereof
The preparation of copper/alkaline earth metal oxide composite nanocatalysts has solved the problem of low efficiency in the existing carbon dioxide methanation reaction, and has achieved high selectivity and high current density carbon dioxide methanation at room temperature, which has broad prospects for industrial application.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- ZHENGZHOU UNIV
- Filing Date
- 2024-01-25
- Publication Date
- 2026-07-21
AI Technical Summary
Existing electrocatalysts suffer from problems such as complex preparation, low methane selectivity, and low current density in the process of converting carbon dioxide to methane, making it difficult to carry out the carbon dioxide methanation reaction efficiently at room temperature.
A copper/alkaline earth metal oxide composite nanocatalyst was prepared by coating copper/alkaline earth metal oxide nanoparticles with amorphous carbon and using an arc discharge method. This process formed a composite structure of Cu/MO1-z nanoparticles and an amorphous carbon layer, which enhanced the active sites and electronic conductivity of the catalyst.
It achieves highly active and selective conversion of carbon dioxide into methane at room temperature, with a current density as high as 150 mA cm-2 and a methane selectivity of 81%, and the preparation process is simple and low in cost.
Smart Images
Figure CN117983223B_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of catalysts, specifically relating to copper / alkaline earth metal oxide composite nanocatalysts, their preparation, and their application as carbon dioxide methanation catalysts. Background Technology
[0002] The combustion of fossil fuels has led to a continuous increase in atmospheric carbon dioxide emissions, triggering a series of climate changes and causing global warming. Limiting the average rise in global temperature to below 1.5 degrees Celsius by reducing atmospheric carbon dioxide emissions is essential. Therefore, converting atmospheric carbon dioxide into valuable chemical feedstocks is a sustainable approach to controlling and utilizing atmospheric carbon dioxide emissions. Furthermore, with the development of solar and wind energy conversion and storage, electricity costs will decrease significantly. Therefore, electrochemical CO2 reduction reactions (CO2RR) driven by renewable energy provide a viable route for manufacturing valuable chemical feedstocks.
[0003] The electrochemical CO2 reduction reaction (CO2RR) process can convert CO2 into a series of short-chain molecules, such as carbon monoxide (CO), formic acid (HCOOH), methane (CH4), methanol (CH3OH), ethylene (C2H4), ethanol (C2H5OH), and propanol (C3H7OH). Among these, CH4 is a suitable energy carrier, with a combustion heat reaching up to 56 kJ / g. -1 It is also a major component of natural gas, a clean energy source that reduces the use of fossil fuels, and can also be used as a raw material to produce carbon black, ammonia, urea, etc.
[0004] Besides electrochemical CO2 methanation, the thermocatalytic reduction of CO2 to CH4 using H2 generated from water electrolysis is also a common method. However, electrochemical CO2 reduction generally occurs at room temperature, while thermocatalytic CO2 conversion typically requires high pressure and high temperature, and the hydrogen produced by water electrolysis requires additional storage and transportation. In comparison, electrochemical CO2 methanation is a more economical and simpler approach.
[0005] Currently, several electrocatalysts have been reported for the CO2 to CH4 conversion reaction. These mainly include Cu / CeO2 (ACS Catal. 2018, 8, 7113-7119), Cu2O / Cu-MOF (ACS Appl. Mater. Interfaces 2019, 11, 9904-9910), Cu-NC (ACS Energy Lett. 2020, 5, 1044-1053), Cu / Al2O3 (Nano Lett. 2021, 21, 7325-7331), and CuPc (Nat. Commun. 2018, 9, 415). However, these electrocatalysts suffer from drawbacks such as complex preparation processes, low FE of the CH4 product, and low partial current density for CH4 formation. Summary of the Invention
[0006] The technical problem to be solved by the present invention is to address the shortcomings of the prior art by providing a preparation and application of a copper / alkaline earth metal oxide composite nanocatalyst. This copper / alkaline earth metal oxide composite nanocatalyst can convert carbon dioxide into methane with high activity and high selectivity at room temperature, and has broad prospects for industrial application.
[0007] To solve the above-mentioned technical problems, the technical solution provided by the present invention is as follows:
[0008] In a first aspect, the present invention provides a copper / alkaline earth metal oxide composite nanocatalyst, which is an amorphous carbon-coated metal nanocatalyst, wherein the catalyst comprises Cu / MO 1-z Nanoparticles, and the Cu / MO coating 1-z Amorphous carbon layer on the surface of nanoparticles, MO 1-z There are certain oxygen vacancies in it, z represents the number of oxygen vacancies, and M is an alkaline earth metal Mg, Ca, Sr or Ba.
[0009] According to the above scheme, Cu and MO 1-z Miscible distribution in Cu and MO 1-z There is a distinct interface at the junction, where Cu and MO lattices coexist and form a state of inter-intercalation.
[0010] According to the above scheme, preferably, the molar ratio of Cu to M is (1-6):(1-6).
[0011] According to the above scheme, preferably, the Cu / MO ratio in the catalyst is... 1-z The mass content of nanoparticles is 80-90%.
[0012] According to the above scheme, the Cu / MO 1-z The particle size of the nanoparticles ranges from 5 to 100 nm.
[0013] According to the above scheme, the thickness of the amorphous carbon layer is 1-3 nm.
[0014] Secondly, the present invention also provides a method for preparing a copper / alkaline earth metal oxide composite nanocatalyst, comprising: uniformly mixing copper metal powder and alkaline earth metal oxide (MO) powder, and then filling the inside of a graphite tube, using the filled graphite tube as the anode; placing it in an arc discharge device, using a graphite rod as the cathode, with the cathode and the anode horizontally opposite each other, passing electricity, performing arc discharge treatment under an inert atmosphere, and collecting the product to obtain the copper / alkaline earth metal oxide composite nanocatalyst.
[0015] According to the above scheme, copper metal powder and alkaline earth metal oxide powder are taken in a molar ratio of (1-6):(1-6).
[0016] According to the above scheme, the arc discharge current is 100-120A.
[0017] According to the above scheme, the particle size of the copper metal powder is 300-500 mesh; the particle size of the alkaline earth metal oxide (MO) powder is 300-500 mesh, and the copper metal powder and alkaline earth metal oxide powder are ground to be uniformly mixed and then filled.
[0018] According to the above scheme, after powering on, bring the anode and cathode close together so that they almost touch and short-circuit, and then quickly move them away until an electric arc discharge and plasma are generated, starting the electric arc discharge reaction. After the reaction lasts for 8 to 15 seconds, continue to move away to terminate the reaction. Repeat the above operation 60 to 80 times.
[0019] According to the above scheme, before the arc discharge treatment, the reaction chamber of the arc discharge equipment is evacuated (specifically, it can be evacuated to 5-8 Pa), and then an inert gas (such as argon) is introduced until the system pressure is 0.08-0.085 MPa.
[0020] According to the above scheme, after the arc discharge reaction is completed, the power supply is turned off, and the product obtained above is allowed to settle naturally for 3-4 hours. The product is then collected to obtain the copper / alkaline earth metal oxide composite nanocatalyst.
[0021] The third aspect of this invention provides the application of the above-mentioned copper / alkaline earth metal oxide composite nanocatalyst as an electrocatalytic carbon dioxide methanation catalyst.
[0022] The fourth aspect of this invention provides a method for the methanation of carbon dioxide, using a copper / alkaline earth metal oxide composite nanocatalyst to selectively catalyze the synthesis of methane from carbon dioxide.
[0023] The copper / alkaline earth metal oxide composite nanocatalyst provided by this invention contains Cu / MO. 1-z Nanoparticles, and the Cu / MO coating 1-zAmorphous carbon on the surface of nanoparticles, MO 1-z There are certain oxygen vacancies in it, MO 1-z The electronegativity of M in the (alkaline earth metal oxide) is lower than that of Cu. Electrons at the composite material interface are directionally transferred from M to Cu, enhancing the charge density of copper sites. At the same time, the presence of oxygen vacancies can provide more active sites to accelerate adsorption and reaction. Meanwhile, the presence of the amorphous carbon layer can increase the overall reaction current density, which is beneficial for conducting electrons from metal nanoparticles to the surface of the catalyst, enhancing the surface electron density. This can synergistically improve the adsorption and activation of the CO2 methanation intermediate *CO by the catalyst of this invention, promote the methanation of carbon dioxide, improve the activity and selectivity of carbon dioxide methanation, and improve the overall performance of the catalyst in carbon dioxide methanation.
[0024] The beneficial effects of this invention are:
[0025] 1. The catalyst of this invention exhibits high activity, methane selectivity, and high current density for the catalytic reaction of carbon dioxide methanation under relatively mild conditions. It can convert carbon dioxide into methane with high activity and selectivity at room temperature and possesses a high current density, making it suitable for practical production applications. The catalyst of this invention has a current density of 1 mol L... -1 In the KOH solution, the CO2 flow rate is 35 mL / min. -1 At that time, the FE conversion rate for carbon dioxide to methane was as high as 81%, with a current density of 150 mA cm⁻¹. -2 ;
[0026] 2. The preparation process of this invention is simple, controllable, highly repeatable, and low in cost. Attached Figure Description
[0027] Figure 1 The XRD patterns are of the catalysts prepared in Examples 2, 7, and 8 of this invention.
[0028] Figure 2 Thermogravimetric analysis (TGA) curve of the catalyst prepared in Example 2;
[0029] Figure 3 High-resolution transmission electron microscope image of the catalyst prepared in Example 7;
[0030] Figure 4 Transmission electron microscope images of the catalysts prepared in Examples 7(a), 8(b), and 2(c);
[0031] Figure 5 High-resolution transmission electron microscope images of the catalysts prepared in Examples 7(a), 8(b), and 2(c);
[0032] Figure 6 The image shows the elemental analysis of the catalyst prepared in Example 2.
[0033] Figure 7 Electron paramagnetic resonance spectra of the catalysts prepared in Examples 2(a) and 7(b);
[0034] Figure 8 The electrochemical performance of the catalyst prepared in Example 2;
[0035] Figure 9 Electrochemical performance diagrams of the copper / alkaline earth metal oxide composite nanocatalysts prepared in Examples 2, 4, 5 and 6;
[0036] Figure 10 Cu3 / MgO prepared in Example 2 1-z Elemental analysis diagram of the @C catalyst. Detailed Implementation
[0037] The present invention will be further illustrated by the following embodiments. It should be understood that the following embodiments are for illustrative purposes only and are not intended to limit the present invention.
[0038] This invention provides a copper / alkaline earth metal oxide composite nanocatalyst, which is an amorphous carbon-coated metal nanocatalyst, wherein the catalyst contains the active component Cu / MO. 1-z Nanoparticles, and the Cu / MO coating 1-z Amorphous carbon layer on the surface of nanoparticles, MO 1-z There are certain oxygen vacancies in it, z represents the number of oxygen vacancies, and M is an alkaline earth metal Mg, Ca, Sr or Ba.
[0039] Preferably, the molar ratio of Cu to M is (1-6):(1-6).
[0040] Furthermore, Cu and MO in the catalyst 1-z Miscible distribution in Cu and MO 1-z There is a distinct interface at the junction, where Cu and MO lattices coexist and form a state of inter-intercalation.
[0041] Cu / MO in the catalyst 1-z The mass content of nanoparticles is 80-90%. The Cu / MO... 1-z If the content of metal nanoparticles is too low, there will be insufficient catalytic active sites.
[0042] Furthermore, the Cu / MO 1-z The particle size of the nanoparticles ranges from 5 to 100 nm.
[0043] Furthermore, the thickness of the amorphous carbon layer is 1–3 nm.
[0044] This invention provides a one-step preparation method for the amorphous carbon-coated metal nanocatalyst used in the conversion of carbon dioxide to methane, employing a simple arc discharge method. The following exemplarily illustrates the preparation method of the amorphous carbon-coated metal nanocatalyst provided by this invention.
[0045] Cu metal powder and alkaline earth metal oxide (MO) powder are uniformly mixed and then filled into the interior of a graphite tube, which serves as the anode. The tube is placed in an arc discharge device, with a graphite rod as the cathode, and the cathode and anode are horizontally opposite each other. Electricity is applied, and arc discharge treatment is performed under an inert atmosphere. The product is collected to obtain a copper / alkaline earth metal oxide composite nanocatalyst. The specific steps are as follows: Electricity is applied, and the anode and cathode are brought close together to almost short-circuit them. Then, they are quickly moved away to generate arc discharge and plasma, initiating the arc discharge reaction. The reaction is continued for 8-15 seconds, and then moved away again to terminate the reaction. The above operation is repeated 60-80 times.
[0046] Furthermore, Cu metal powder and MO alkaline earth metal oxide powder are taken in a molar ratio of (1-6):(1-6).
[0047] Furthermore, the arc discharge current is 100–120 A.
[0048] In some embodiments, the Cu metal powder has a particle size of 300-500 mesh; the alkaline earth metal oxide (MO) powder has a particle size of 300-500 mesh.
[0049] In some embodiments, before the arc discharge reaction, the reaction chamber is evacuated to 5-8 Pa, and then an inert gas such as argon is introduced until the system pressure is 0.08-0.085 MPa.
[0050] After the arc discharge reaction is completed, the power supply is turned off, and the product obtained above is allowed to settle naturally for 3-4 hours. The product is then collected to obtain the copper / alkaline earth metal oxide composite nanocatalyst (Cu / MO). 1-z @C).
[0051] The graphite tubes used are preferably selected for their high temperature resistance, high density, spectral purity, and thin walls. This further prevents the doping of impurities and excessive carbon content from affecting the catalytic performance of the catalyst. Preferably, the dimensions of the graphite tube are: outer diameter 8mm, inner diameter 6mm, and length 12-15cm. The dimensions of the graphite rod are: diameter 8mm and length 25-30cm.
[0052] The catalytic performance of the catalyst prepared in this invention was tested. All catalytic reactions were carried out in a flow cell. 5 mg of catalyst powder was weighed and placed in a glass bottle, 1 mL of 0.5 wt.% Nafion solution was added, and then ultrasonically dispersed to obtain a catalyst slurry. 200 μL of the catalyst slurry was taken and uniformly sprayed onto a 1.5 cm × 3 cm hydrophobic carbon paper as the cathode, and a 1.5 cm × 3 cm Ni mesh was used as the anode. A flow cell was installed, and then a flow rate of 35 mL / min was introduced. -1 CO2 gas. The electrolyte used at both the cathode and anode is 1 mol / L. -1 KOH solution. The product was directly analyzed qualitatively and quantitatively using gas chromatography.
[0053] The catalyst prepared by the above method is used to convert CO2 into CH4, showing high activity and CH4 selectivity, and has the advantages of simple, fast and low cost preparation method.
[0054] The following examples further illustrate the present invention in detail. It should also be understood that the following examples are only for further explanation of the present invention and should not be construed as limiting the scope of protection of the present invention. Any non-essential improvements and adjustments made by those skilled in the art based on the above description of the present invention are within the scope of protection of the present invention. The specific process parameters, etc., in the following examples are merely examples within a suitable range; that is, those skilled in the art can make appropriate selections within the appropriate range based on the description herein, and are not intended to be limited to the specific values in the examples below.
[0055] Example 1
[0056] A Cu / MgO 1-z The preparation method of the @C catalyst is as follows:
[0057] Cu and MgO powders (300 mesh and 400 mesh particle sizes, respectively) with a molar ratio of 1:1 were ground and uniformly mixed, and then filled into a graphite tube with an outer diameter of 8 mm, an inner diameter of 6 mm, and a length of 15 cm to form the anode. A cathode graphite rod with a diameter of 8 mm and a length of 30 cm was then fixed on a water-cooled copper vessel and positioned horizontally opposite the anode. The reaction chamber of the arc discharge device was evacuated to a pressure of 5 Pa, and then filled with argon gas to a pressure of 0.08 MPa. Power was applied at a current of 100 A. The knob of the arc discharge device was rotated to bring the anode and cathode close together, almost to short-circuit them, and then quickly moved away to generate an arc discharge and plasma, initiating the arc discharge reaction. The reaction was continued for 10 seconds, and then moved away again to terminate the reaction. This process was repeated 80 times. After the reaction, the power was turned off, and the reaction products were allowed to settle naturally for 3 hours and collected to obtain the Cu / MgO product. 1-z @C catalyst.
[0058] Weigh out 5 mg of Cu / MgO 1-z The C catalyst was placed in a glass bottle, and 1 mL of 0.5 wt.% Nafion solution was added. The mixture was sonicated for 30 min to ensure uniform dispersion, resulting in a catalyst slurry. 200 μL of this slurry was then uniformly sprayed onto a 1.5 cm × 3 cm hydrophobic carbon paper sheet to serve as the cathode. A 1.5 cm × 3 cm Ni mesh was used as the anode. A flow cell was installed, and a flow rate of 35 mL / min was introduced. -1 The CO2 gas is used, and the electrolyte used at both the cathode and anode is 1 mol L. -1 KOH solution. The product was directly analyzed qualitatively and quantitatively using gas chromatography. The results are shown in Table 1.
[0059] Example 2
[0060] A Cu3 / MgO 1-z The preparation method of the @C catalyst is as follows:
[0061] Cu and MgO powders (300 mesh and 400 mesh particle sizes, respectively) with a molar ratio of 3:1 were ground and uniformly mixed, then filled into a graphite tube with an outer diameter of 8 mm, an inner diameter of 6 mm, and a length of 15 cm to form the anode. A cathode graphite rod with a diameter of 8 mm and a length of 30 cm was then fixed on a water-cooled copper vessel and positioned horizontally opposite the anode. The reaction chamber was evacuated to a pressure of 5 Pa, then filled with argon gas to a pressure of 0.08 MPa. Power was applied at a current of 100 A. The knob of the arc discharge device was rotated to bring the anode and cathode close together, almost to short-circuit them, and then quickly moved away to generate an arc discharge and plasma, initiating the arc discharge reaction. The reaction was continued for 10 seconds, then moved away again to terminate the reaction. This process was repeated 80 times, with a current of 100 A and a reaction time of 0.5 h. After the reaction, the power was turned off, and the reaction products were allowed to settle naturally for 3 h and collected to obtain Cu3 / MgO. 1-z @C catalyst. The synthesized Cu3 / MgO ratio was determined by ICP-OES. 1-z The Cu:Mg molar ratio of the @C catalyst is 2.4:1.
[0062] Weigh out 5 mg of Cu3 / MgO 1-z The C catalyst was placed in a glass bottle, and 1 mL of 0.5 wt.% Nafion solution was added. The mixture was sonicated for 30 min to ensure uniform dispersion, resulting in a catalyst slurry. 200 μL of this slurry was then uniformly sprayed onto a 1.5 cm × 3 cm hydrophobic carbon paper sheet to serve as the cathode. A 1.5 cm × 3 cm Ni mesh was used as the anode, and a flow cell was installed. A flow rate of 35 mL / min was then introduced. -1 CO2 gas. The electrolyte used at both the cathode and anode is 1 mol / L. -1KOH solution. The product was directly analyzed qualitatively and quantitatively using gas chromatography. The results are shown in Table 1.
[0063] Example 3
[0064] A Cu5 / MgO 1-z The preparation method of the @C catalyst is as follows:
[0065] Cu and MgO powders (300 mesh and 400 mesh particle sizes, respectively) with a molar ratio of 5:1 were ground and uniformly mixed, then filled into a graphite tube with an outer diameter of 8 mm, an inner diameter of 6 mm, and a length of 15 cm to form the anode. A cathode graphite rod with a diameter of 8 mm and a length of 30 cm was then fixed on a water-cooled copper vessel and positioned horizontally opposite the anode. The reaction chamber was evacuated to a pressure of 5 Pa, then filled with argon gas to a pressure of 0.08 MPa. Power was applied at a current of 100 A. The knob of the arc discharge device was rotated to bring the anode and cathode close together, almost to short-circuit them, and then quickly moved away until an arc discharge and plasma were generated, initiating the arc discharge reaction. The reaction was continued for 10 seconds, then moved away again to terminate the reaction. This process was repeated 80 times, with a current of 100 A and a reaction time of 0.5 h. After the reaction, the power was turned off, and the reaction products were allowed to settle naturally for 3 h and collected to obtain Cu5 / MgO. 1-z @C catalyst.
[0066] Weigh out 5 mg of Cu5 / MgO 1-z The C catalyst was placed in a glass bottle, and 1 mL of 0.5 wt.% Nafion solution was added. The mixture was sonicated for 30 min to ensure uniform dispersion, resulting in a catalyst slurry. 200 μL of this slurry was then uniformly sprayed onto a 1.5 cm × 3 cm hydrophobic carbon paper sheet to serve as the cathode. A 1.5 cm × 3 cm Ni mesh was used as the anode, and a flow cell was installed. A flow rate of 35 mL / min was then introduced. -1 CO2 gas. The electrolyte used at both the cathode and anode is 1 mol / L KOH. -1 The solution was then subjected to qualitative and quantitative analysis using gas chromatography. The results are shown in Table 1.
[0067] Example 4
[0068] A Cu / CaO 1-z The preparation method of the @C catalyst is as follows:
[0069] Cu and CaO powders (300 mesh and 400 mesh particle sizes, respectively) with a molar ratio of 1:1 were ground and uniformly mixed, and then filled into a graphite tube with an outer diameter of 8 mm, an inner diameter of 6 mm, and a length of 15 cm to form the anode. A cathode graphite rod with a diameter of 8 mm and a length of 30 cm was then fixed on a water-cooled copper vessel and placed horizontally opposite the anode. The reaction chamber was evacuated to a pressure of 5 Pa, and then filled with argon gas to a pressure of 0.08 MPa. Power was applied at a current of 100 A. The knob of the arc discharge device was rotated to bring the anode and cathode close together, almost to short-circuit them, and then quickly moved away to generate an arc discharge and plasma, initiating the arc discharge reaction. The reaction was continued for 10 seconds, and then moved away again to terminate the reaction. This process was repeated 80 times, with a current of 100 A and a reaction time of 0.5 h. After the reaction, the power was turned off, and the reaction products were allowed to settle naturally for 3 h and collected to obtain the Cu / CaO product. 1-z @C catalyst.
[0070] Weigh out 5 mg of Cu / CaO 1-z The C catalyst was placed in a glass bottle, and 1 mL of 0.5 wt.% Nafion solution was added. The mixture was sonicated for 30 min to ensure uniform dispersion, resulting in a catalyst slurry. 200 μL of this slurry was then uniformly sprayed onto a 1.5 cm × 3 cm hydrophobic carbon paper sheet to serve as the cathode. A 1.5 cm × 3 cm Ni mesh was used as the anode, and a flow cell was installed. A flow rate of 35 mL / min was then introduced. -1 CO2 gas. The electrolyte used at both the cathode and anode is 1 mol / L. -1 KOH solution. The product was directly analyzed qualitatively and quantitatively using gas chromatography. The results are shown in Table 1.
[0071] Example 5
[0072] A Cu / SrO 1-z The preparation method of the @C catalyst is as follows:
[0073] Cu and SrO powders (300 mesh and 400 mesh particle sizes, respectively) in a 1:1 molar ratio were ground and uniformly mixed, then filled into a graphite tube with an outer diameter of 8 mm, an inner diameter of 6 mm, and a length of 15 cm to form the anode. A cathode graphite rod with a diameter of 8 mm and a length of 30 cm was then fixed on a water-cooled copper vessel and positioned horizontally opposite the anode. The reaction chamber was evacuated to a pressure of 5 Pa, then filled with argon gas to a pressure of 0.08 MPa. Power was applied at a current of 100 A. The knob of the arc discharge device was rotated to bring the anode and cathode close together, almost to short-circuit them, and then quickly moved away to generate an arc discharge and plasma, initiating the arc discharge reaction. The reaction was continued for 10 seconds, then moved away again to terminate the reaction. This process was repeated 80 times, with a current of 100 A and a reaction time of 0.5 h. After the reaction, the power was turned off, and the reaction products were allowed to settle naturally for 3 h and collected to obtain the Cu / SrO2 mixture. 1-z @C catalyst.
[0074] Weigh out 5 mg of Cu / SrO 1-z The C catalyst was placed in a glass bottle, and 1 mL of 0.5 wt.% Nafion solution was added. The mixture was sonicated for 30 min to ensure uniform dispersion, resulting in a catalyst slurry. 200 μL of this slurry was then uniformly sprayed onto a 1.5 cm × 3 cm hydrophobic carbon paper sheet to serve as the cathode. A 1.5 cm × 3 cm Ni mesh was used as the anode, and a flow cell was installed. A flow rate of 35 mL / min was then introduced. -1 CO2 gas. The electrolyte used at both the cathode and anode is 1 mol / L. -1 KOH solution. The product was directly analyzed qualitatively and quantitatively using gas chromatography. The results are shown in Table 1.
[0075] Example 6
[0076] A Cu / BaO 1-z The preparation method of the @C catalyst is as follows:
[0077] Cu and BaO powders (300 mesh and 400 mesh particle sizes, respectively) in a 1:1 molar ratio were ground and uniformly mixed, then filled into a graphite tube with an outer diameter of 8 mm, an inner diameter of 6 mm, and a length of 15 cm to form the anode. A cathode graphite rod with a diameter of 8 mm and a length of 30 cm was then fixed on a water-cooled copper vessel, horizontally opposite the anode. The reaction chamber was evacuated to a pressure of 5 Pa, then filled with argon gas to a pressure of 0.08 MPa. Power was applied at a current of 100 A. The knob of the arc discharge device was rotated to bring the anode and cathode close together, almost to short-circuit them, and then quickly moved away to generate an arc discharge and plasma, initiating the arc discharge reaction. The reaction was continued for 10 seconds, then moved away again to terminate the reaction. This process was repeated 80 times, with a current of 100 A and a reaction time of 0.5 h. After the reaction, the power was turned off, and the reaction products were allowed to settle naturally for 3 h and collected to obtain the Cu / BaO product. 1-z @C catalyst.
[0078] Weigh out 5 mg of Cu / BaO 1-z The C catalyst was placed in a glass bottle, and 1 mL of 0.5 wt.% Nafion solution was added. The mixture was sonicated for 30 min to ensure uniform dispersion, resulting in a catalyst slurry. 200 μL of this slurry was then uniformly sprayed onto a 1.5 cm × 3 cm hydrophobic carbon paper sheet to serve as the cathode. A 1.5 cm × 3 cm Ni mesh was used as the anode, and a flow cell was installed. A flow rate of 35 mL / min was then introduced. -1 CO2 gas. The electrolyte used at both the cathode and anode is 1 mol / L. -1 KOH solution. The product was directly analyzed qualitatively and quantitatively using gas chromatography. The results are shown in Table 1.
[0079] Example 7 (Comparative Example 1)
[0080] A Cu@C catalyst, the preparation method of which is as follows:
[0081] Cu powder (300 mesh particle size) was filled into a graphite tube with an outer diameter of 8 mm, an inner diameter of 6 mm, and a length of 15 cm to form the anode. A cathode graphite rod with a diameter of 8 mm and a length of 30 cm was then fixed on a water-cooled copper vessel, horizontally opposite the anode. The reaction chamber was evacuated to a pressure of 5 Pa, then filled with argon gas to a pressure of 0.08 MPa. A current of 100 A was applied, and the knob of the arc discharge device was rotated to bring the anode and cathode close together, almost to short-circuit them. The anode and cathode were then quickly moved away to generate an arc discharge and plasma, initiating the arc discharge reaction. The reaction was continued for 10 seconds, then moved away again to terminate the reaction. This process was repeated 80 times, with a current of 100 A and a reaction time of 0.5 h. After the reaction, the power was turned off, and the reaction products were allowed to settle naturally for 3 h and collected to obtain the Cu@C catalyst.
[0082] Weigh 5 mg of Cu@C catalyst and place it in a glass bottle. Add 1 mL of 0.5 wt.% Nafion solution and sonicate for 30 min to uniformly disperse it into a catalyst slurry. Take 200 μL of the catalyst slurry and spray it evenly onto a 1.5 cm × 3 cm hydrophobic carbon paper as the cathode. Use a 1.5 cm × 3 cm Ni mesh as the anode, install a flow cell, and then introduce a flow at a rate of 35 mL / min. -1 CO2 gas. The electrolyte used at both the cathode and anode is 1 mol / L. -1 KOH solution. The product was directly analyzed qualitatively and quantitatively using gas chromatography. The results are shown in Table 1.
[0083] Example 8 (Comparative Example 2)
[0084] A type of MgO 1-z The preparation method of the @C catalyst is as follows:
[0085] MgO powder (400 mesh particle size) was filled into a graphite tube with an outer diameter of 8 mm, an inner diameter of 6 mm, and a length of 15 cm to form the anode. A cathode graphite rod with a diameter of 8 mm and a length of 30 cm was then fixed to a water-cooled copper vessel, horizontally opposite the anode. The reaction chamber was evacuated to a pressure of 5 Pa, then filled with argon gas to a pressure of 0.08 MPa. Power was applied at a current of 100 A. The knob of the arc discharge device was rotated to bring the anode and cathode close together, almost to short-circuit them, and then quickly moved away to generate an arc discharge and plasma, initiating the arc discharge reaction. The reaction was continued for 10 seconds, and then moved away again to terminate the reaction. This process was repeated 80 times, with a current of 100 A and a reaction time of 0.5 h. After the reaction, the power was turned off, and the reaction products were allowed to settle naturally for 3 h and collected to obtain MgO. 1-z @C catalyst.
[0086] Weigh out 5mg of MgO1-z The C catalyst was placed in a glass bottle, and 1 mL of 0.5 wt.% Nafion solution was added. The mixture was sonicated for 30 min to ensure uniform dispersion, resulting in a catalyst slurry. 200 μL of this slurry was then uniformly sprayed onto a 1.5 cm × 3 cm hydrophobic carbon paper sheet to serve as the cathode. A 1.5 cm × 3 cm Ni mesh was used as the anode, and a flow cell was installed. A flow rate of 35 mL / min was then introduced. -1 CO2 gas. The electrolyte used at both the cathode and anode is 1 mol / L. -1 KOH solution. The product was directly analyzed qualitatively and quantitatively using gas chromatography. The results are shown in Table 1.
[0087] Table 1 shows the performance of the catalysts in Examples 1-8 for the conversion of carbon dioxide to methane.
[0088]
[0089] Figure 1 Cu@C prepared in Example 7 and MgO prepared in Example 8 1-z @C, Cu3 / MgO prepared in Example 2 1-z The XRD pattern of the @C catalyst shows that Cu3 / MgO 1-z The @C catalyst exhibits characteristic diffraction peaks at 43.3°, 62.3°, and 74.1°, corresponding to the Cu(200), MgO(220), and Cu(220) crystal planes, respectively.
[0090] Figure 2 Cu3 / MgO prepared in Example 2 1-z Thermogravimetric analysis (TGA) plot of catalyst C shows that the carbon content in the catalyst is approximately 16%, and the Cu3 / MgO ratio is [not specified]. 1-z The content of nanoparticles is approximately 84%.
[0091] Figure 3 The image shows a high-resolution transmission electron microscope image of the Cu@C catalyst prepared in Example 7. The thickness of the amorphous carbon layer is 2.21 nm.
[0092] Figure 4 (a), (b), and (c) are Cu@C prepared in Example 7 and MgO prepared in Example 8, respectively. 1-z @C, Cu3 / MgO prepared in Example 2 1-z The transmission electron microscope image of the @C catalyst shows that the particle size distribution of the catalyst prepared in this invention is 5-100 nm.
[0093] Figure 5 Cu@C prepared in Example 7 and MgO prepared in Example 8 1-z @C, Cu3 / MgO prepared in Example 21-z High-resolution transmission electron microscopy images of the @C catalyst, as shown in (a), (b), and (c), show distinct 0.18 nm lattice fringes corresponding to the (200) crystal plane of Cu and 0.21 nm lattice fringes corresponding to the (200) crystal plane of MgO in 5(c).
[0094] Figure 6 Cu3 / MgO prepared in Example 2 1-z The elemental analysis diagram of the @C catalyst shows that Cu, Mg, O, and C elements are evenly distributed.
[0095] Figure 7 Cu3 / MgO prepared in Example 2 1-z Electron paramagnetic resonance (EPR) spectra of Cu@C catalyst and Cu@C catalyst prepared in Example 7. From the spectra, it can be seen that Cu3 / MgO 1-z @C contains a certain amount of oxygen vacancies.
[0096] Figure 10 Cu3 / MgO prepared in Example 2 1-z The elemental analysis diagram of the C catalyst shows that Cu and MgO are present. 1-z The distribution of elements on the interface.
[0097] Based on the above description, it can be seen that the microstructure of the copper / alkaline earth metal oxide composite nanocatalyst prepared in this invention is predominantly Cu3 / MgO. 1-z For example, the form is Cu and MgO 1-z Miscible distribution. In Cu and MgO... 1-z There is a clear interface at the junction, and the corresponding energy-dispersive X-ray spectra show that Cu and MgO are located on either side of the interface. 1-z They are distributed separately. At the interface, Cu and MgO lattices coexist, forming a state of inter-intercalation.
[0098] Figure 8 Cu3 / MgO prepared in Example 2 1-z Electrochemical performance of C catalyst (reaction conditions: 1 mg Cu3 / MgO) 1-z @C, 35mL min -1 CO2, 1 mol L -1 KOH, 25℃. Reaction tank: flow tank). As shown in the figure, the catalyst exhibits good methane selectivity.
[0099] Figure 9The figures show the electrochemical performance of the copper / alkaline earth metal oxide composite nanocatalysts prepared in Examples 2, 4, 5, and 6. As can be seen from the figures, the copper / alkaline earth metal oxide composite nanocatalysts prepared in Examples 2, 4, 5, and 6 of this invention have excellent activity and high selectivity for carbon dioxide methanation; the value of FE(CH4 / C2H4) gradually increases with the change of alkaline earth metal oxides (MgO, CaO, SrO, BaO), showing good methane selectivity.
Claims
1. A copper / alkaline earth metal oxide composite nanocatalyst, which is an amorphous carbon-coated metal nanocatalyst, wherein the catalyst comprises Cu / MO 1-z Nanoparticles, and the Cu / MO coating 1-z Amorphous carbon layer on the surface of nanoparticles, MO 1-z Oxygen vacancies exist, z represents the number of oxygen vacancies, M is an alkaline earth metal Mg, Ca, Sr or Ba, and Cu and MO... 1-z Miscible distribution in Cu and MO 1-z There is a clear interface at the junction, where Cu and MO lattices coexist and form a state of inter-intercalation of lattices. Cu / MO in the catalyst 1-z The nanoparticles have a mass content of 80-90%, and the amorphous carbon layer has a thickness of 1-3 nm.
2. The copper / alkaline earth metal oxide composite nanocatalyst according to claim 1, characterized in that: The Cu / MO 1-z The particle size of the nanoparticles ranges from 5 to 100 nm.
3. The copper / alkaline earth metal oxide composite nanocatalyst according to claim 1, characterized in that: The molar ratio of Cu to M is (1~6):(1~6).
4. A method for preparing the copper / alkaline earth metal oxide composite nanocatalyst according to claim 1, characterized in that: Copper metal powder and alkaline earth metal oxide powder are uniformly mixed and then filled into the inside of a graphite tube, which serves as the anode. The tube is placed in an arc discharge device, with a graphite rod serving as the cathode. The cathode and anode are horizontally opposite each other. Electricity is applied, and arc discharge is performed under an inert atmosphere. The product is collected to obtain a copper / alkaline earth metal oxide composite nanocatalyst.
5. The preparation method according to claim 4, characterized in that: The arc discharge current is 100~120 A.
6. The preparation method according to claim 4, characterized in that: Copper metal powder and alkaline earth metal oxide powder are taken in a molar ratio of (1~6):(1~6); The copper metal powder has a particle size of 300-500 mesh; the alkaline earth metal oxide powder has a particle size of 300-500 mesh; the copper metal powder and alkaline earth metal oxide powder are ground and mixed evenly before being filled. Before the arc discharge reaction, the reaction chamber is evacuated to 5-8 Pa, and then an inert gas is introduced at a pressure of 0.08-0.085 MPa.
7. The preparation method according to claim 4, characterized in that: After the arc discharge reaction is completed, the power is turned off, and the product obtained above is allowed to settle naturally for 3-4 hours. The product is then collected to obtain the copper / alkaline earth metal oxide composite nanocatalyst.
8. The application of the copper / alkaline earth metal oxide composite nanocatalyst as a catalyst for the electrocatalytic methanation of carbon dioxide according to any one of claims 1-3.
9. A method for the methanation of carbon dioxide, characterized in that: Using the copper / alkaline earth metal oxide composite nanocatalyst as described in any one of claims 1-3 as a carbon dioxide methanation catalyst, highly selective electrocatalytic synthesis of methane from carbon dioxide is achieved.