A copper-samarium biphasic catalyst for efficient electroreduction of carbon dioxide to synthesize multi-carbon products and its preparation method

Abstract

The present invention discloses a copper-samarium biphasic catalyst for the efficient electroreduction of carbon dioxide to synthesize multi-carbon products and a preparation method thereof. The samarium biphasic catalyst is a composite material of copper oxide and copper-samarium oxide, and the copper-samarium oxide is an oxide with a copper-samarium molar ratio of 1 or 0.5 or a mixture of the two; in the copper-samarium biphasic catalyst, the molar ratio of copper to samarium is not greater than 39. The copper-samarium biphasic catalyst of the present invention can be used for the electrocatalytic reduction of carbon dioxide to prepare multi-carbon products, wherein the copper-samarium biphasic catalyst is used as a cathode material to promote carbon-carbon coupling and improve the selectivity of multi-carbon products. The present invention designs a copper-samarium biphasic catalytic material, and by introducing a second metal samarium, regulates the interaction between metal and metal, metal and carrier, and metal and reaction intermediate in the catalyst, thereby improving the reaction activity and target product selectivity.

Description

Technical Field

[0001] The invention relates to a copper-samarium biphasic catalyst for efficiently electroreducing carbon dioxide to synthesize multi-carbon products and a preparation method thereof, belonging to the field of electrochemical catalysis. Background Art

[0002] Electrochemical carbon dioxide reduction (ECR) can effectively utilize renewable energy to convert CO2 into high-value-added chemicals, helping to alleviate the pressure of global warming and the shortage of non-renewable energy. Due to its green and sustainable development, it has attracted widespread attention. Using electrochemical catalysis of CO2 to address the conversion and regeneration of non-renewable energy has become one of the solutions to address the current energy and resource shortages. However, the CO2 conversion process is plagued by low conversion efficiency and poor selectivity, which greatly limits the improvement of CO2 value and the selective conversion capability.

[0003] Among the various products generated by CO2 reduction, carbon-carbon coupling and hydrogenation are important pathways for increasing CO2's value. However, because the reduction of protons to hydrogen often occurs near the sites required for CO2 reduction, these two reactions often coexist and compete, making them difficult to control. This leads to complex products and compromised production value. Therefore, designing appropriate catalysts to control the reaction pathways has become a highly anticipated solution. Summary of the Invention

[0004] The purpose of the present invention is to provide a copper-samarium biphasic catalyst for the efficient electroreduction of carbon dioxide to synthesize multi-carbon products, in which copper oxide and copper-samarium oxide are uniformly distributed and exhibit high activity and superior performance.

[0005] The copper-samarium biphasic catalyst provided by the present invention is a composite material of copper oxide and copper-samarium oxide;

[0006] Wherein, the copper-samarium oxide is an oxide with a copper-samarium molar ratio of 1 or 0.5 or a mixture of the two; preferably, the oxide with a copper-samarium molar ratio of 0.5.

[0007] In the copper-samarium biphasic catalyst, the molar ratio of copper to samarium is not greater than 39, preferably any value among 1.5, 2, 4, 9, 19 and 39 or a range value consisting of any two values ​​therein, more preferably 2-19, 4-19, 9-19 or 9.

[0008] Copper, samarium and oxygen are uniformly distributed in the copper-samarium dual-phase catalyst.

[0009] The present invention further provides a method for preparing the copper-samarium biphasic catalyst, comprising the following steps:

[0010] S1. Prepare aqueous solutions of copper nitrate and samarium nitrate;

[0011] Among them, copper nitrate trihydrate and samarium nitrate hexahydrate are preferred;

[0012] S2. preparing an aqueous solution of ammonium carbonate and potassium hydroxide to form a precipitant solution;

[0013] The molar ratio of the ammonium carbonate to the potassium hydroxide is 1 to 2.33;

[0014] S3, adding the precipitant solution to the aqueous solution in step S1, obtaining a solid mixture by precipitation, centrifuging, washing, and then grinding to obtain a powder;

[0015] Water and ethanol can be used for washing;

[0016] S4, calcining the powder in flowing air and hydrogen / argon atmospheres in sequence;

[0017] S5. calcining the powder processed in step S4 in static air to obtain the product.

[0018] In the above preparation method, before step S3, the aqueous solution in step S1 is stirred for 20 to 40 minutes and then preheated to 50 to 70°C;

[0019] In step S3, the precipitant solution is added dropwise to the aqueous solution, stirred, and then heated to 75-85° C. and maintained for 2-4 hours.

[0020] In the above preparation method, in step S4, the conditions for calcination in the flowing air are as follows:

[0021] The temperature is 300-400°C, the heating rate is 5°C / min, and the time is 2-4 hours.

[0022] The conditions for calcination in the hydrogen / argon atmosphere are as follows:

[0023] The temperature is 250-350℃, the heating rate is 5℃ / min, and the time is 2-4h.

[0024] In step S5, the calcination conditions are as follows:

[0025] The temperature is 600-800℃, the heating rate is 5℃ / min, and the time is 2-4h.

[0026] The copper-samarium biphasic catalyst of the present invention can be used for electrocatalytic reduction of carbon dioxide to produce multi-carbon products. The copper-samarium biphasic catalyst, as a cathode material, can promote carbon-carbon coupling and improve the selectivity of multi-carbon products.

[0027] The multi-carbon products include ethylene, ethanol, acetic acid and n-propanol.

[0028] The present invention further provides a method for preparing multi-carbon products by electrocatalytic reduction of carbon dioxide, comprising the following steps:

[0029] Using a mercury / mercuric oxide electrode as a reference electrode, a nickel foam electrode as a counter electrode, and the copper-samarium biphasic catalyst as a working electrode, electrochemical reduction is carried out in a gas diffusion flow electrolytic cell to obtain a multi-carbon product.

[0030] Wherein, in the gas diffusion type flow electrolytic cell, the anolyte is a potassium hydroxide aqueous solution, and the catholyte is a potassium hydroxide aqueous solution;

[0031] continuously introducing carbon dioxide gas during the electrochemical reduction process;

[0032] The current used for the electrochemical reduction is 100-900 mA, preferably 700 mA.

[0033] The present invention utilizes a high-temperature calcination method to prepare a copper-samarium biphasic catalyst, which features simple, low-cost, highly reproducible, and environmentally friendly preparation. The present invention utilizes copper oxide and copper-samarium oxide to synergistically regulate the catalytic material and catalytic environment, providing a new approach for synthesizing highly active electrode materials for the conversion of carbon dioxide to produce multi-carbon products. The copper-samarium biphasic catalytic electrode provided by the present invention can achieve high multi-carbon efficiency at high current densities and exhibits high catalytic stability.

[0034] The present invention designs a copper-samarium biphasic catalytic material, and by introducing a second metal samarium, regulates the interactions between metals, metals and carriers, and metals and reaction intermediates in the catalyst, thereby improving the reaction activity and target product selectivity. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 This is a scanning electron microscope image of a dual-phase catalyst of copper oxide and copper samarium oxide with a copper to samarium molar ratio of 9, prepared in Example 1 of the present invention.

[0036] Figure 2 This is the X-ray diffraction pattern of the copper oxide and copper samarium oxide dual-phase catalyst with a copper to samarium molar ratio of 9 prepared in Example 1 of the present invention.

[0037] Figure 3 This is an element distribution diagram of the copper oxide and copper samarium oxide dual-phase catalyst with a copper to samarium molar ratio of 9 prepared in Example 1 of the present invention.

[0038] Figure 4 This is a scanning electron microscope image of a dual-phase catalyst of copper oxide and copper samarium oxide with a copper to samarium molar ratio of 39 prepared in Example 2 of the present invention.

[0039] Figure 5 This is a scanning electron microscope image of a dual-phase catalyst of copper oxide and copper samarium oxide with a copper to samarium molar ratio of 19 prepared in Example 3 of the present invention.

[0040] Figure 6 This is a scanning electron microscope image of a dual-phase catalyst of copper oxide and copper samarium oxide with a copper to samarium molar ratio of 4 prepared in Example 4 of the present invention.

[0041] Figure 7 This is a scanning electron microscope image of a dual-phase catalyst of copper oxide and copper samarium oxide with a copper to samarium molar ratio of 2 prepared in Example 5 of the present invention.

[0042] Figure 8 This is a scanning electron microscope image of a dual-phase catalyst of copper oxide and copper samarium oxide with a copper to samarium molar ratio of 1.5 prepared in Example 6 of the present invention.

[0043] Figure 9 This is a graph showing the electrochemical reduction performance of carbon dioxide using a dual-phase catalyst of copper oxide and copper samarium oxide with a copper to samarium molar ratio of 9, as prepared in Example 1 of the present invention.

[0044] Figure 10 Graph showing the effect of catalysts with different copper-samarium molar ratios on carbon dioxide reduction performance, with a test current of 700 mA.

[0045] Figure 11 This is a graph showing the performance stability of the copper oxide and copper samarium oxide dual-phase catalyst with a copper to samarium molar ratio of 9 in the conversion of carbon dioxide to prepare multi-carbon products. The test current is 700 mA.

[0046] Figure 12 This is a scanning electron microscope image of the copper oxide catalyst prepared in Comparative Example 1. DETAILED DESCRIPTION

[0047] Unless otherwise specified, the experimental methods used in the following examples are conventional methods.

[0048] Unless otherwise specified, the materials and reagents used in the following examples can be obtained from commercial sources.

[0049] Example 1. Preparation of a Dual-Phase Catalyst of Copper Oxide and Copper-Samarium Oxide with a Copper-Samarium Molar Ratio of 9

[0050] a) 2.7 mmol of copper nitrate trihydrate and 0.3 mmol of samarium nitrate hexahydrate were dissolved in 10 ml of deionized water using ultrasound. The mixture was then stirred vigorously for 30 minutes and then preheated to 55°C.

[0051] b) 5 mmol of ammonium carbonate and 5 mmol of potassium hydroxide were dissolved in 13 ml of deionized water to serve as alkaline precipitant solutions.

[0052] c) Add the mixed alkaline precipitant solution dropwise at 55°C at a rate of ~1 ml / min, stir vigorously for 10 minutes, then raise the temperature to 80°C and maintain for 2 hours. Centrifuge the resulting solid mixture three times, washing with deionized water / ethanol during centrifugation, dry at 135°C overnight, and then grind thoroughly.

[0053] d) The ground powder was calcined at 350° C. in flowing air for 2 hours and then at 300° C. in a hydrogen / argon atmosphere for 2 hours, with a heating rate of 5° C. per minute.

[0054] e) Finally, the redox-reduced powder was calcined in static air at 700° C. for 3 hours with a heating rate of 5° C. per minute.

[0055] The scanning electron microscope image of the copper oxide and copper samarium oxide dual-phase catalyst with a copper-samarium molar ratio of 9 is as follows: Figure 1 、 X X-ray diffraction pattern Figure 2 , element distribution diagram as follows Figure 3 .

[0056] from Figure 1 It can be seen that the final obtained copper oxide and copper samarium oxide dual-phase catalyst with a copper to samarium molar ratio of 9 presents a bulk structure.

[0057] from Figure 2 The main crystal forms are copper oxide and copper-samarium oxide. Further analysis of diffraction peaks by X-ray diffraction, elemental analysis by EDS scanning electron microscope (EDS), and inductively coupled plasma (ICP) analysis confirmed the specific ratios of copper, samarium, and oxygen, as well as the phase composition of copper-samarium oxide. Copper-samarium oxide is a compound with a copper-samarium-oxygen molar ratio of 1:2:4 (i.e., a copper-samarium molar ratio of 0.5).

[0058] from Figure 3 It can be seen that copper, samarium and oxygen elements are evenly distributed in the catalytic material.

[0059] Example 2: Preparation of a Dual-Phase Catalyst of Copper Oxide and Copper-Samarium Oxide with a Copper-Samarium Molar Ratio of 39

[0060] The amount of copper nitrate trihydrate in Example 1 was replaced with 2.925 mmol, and the amount of samarium nitrate hexahydrate was replaced with 0.075 mmol. Finally, a copper oxide and copper samarium oxide dual-phase catalyst with a copper to samarium molar ratio of 39 was obtained. The scanning electron microscope image of the catalyst is shown in FIG. Figure 4 It can be seen that the final copper oxide and copper samarium oxide dual-phase catalyst with a copper to samarium molar ratio of 39 presents a spherical block structure.

[0061] Example 3. Preparation of a Dual-Phase Catalyst of Copper Oxide and Copper-Samarium Oxide with a Copper-Samarium Molar Ratio of 19

[0062] The amount of copper nitrate trihydrate in Example 1 was replaced with 2.85 mmol, and the amount of samarium nitrate hexahydrate was replaced with 0.15 mmol. Finally, a copper oxide and copper samarium oxide dual-phase catalyst with a copper to samarium molar ratio of 19 was obtained. The scanning electron microscope image thereof is shown in FIG. Figure 5 It can be seen that the final copper oxide and copper samarium oxide dual-phase catalyst with a copper to samarium molar ratio of 19 presents a relatively uniform spherical block structure.

[0063] Example 4. Preparation of a Dual-Phase Catalyst of Copper Oxide and Copper-Samarium Oxide with a Copper-Samarium Molar Ratio of 4

[0064] The amount of copper nitrate trihydrate in Example 1 was replaced by 2.4 mmol, the amount of samarium nitrate hexahydrate was replaced by 0.6 mmol, and the amounts of ammonium carbonate and potassium hydroxide were replaced by 6 mmol and 4 mmol, respectively. Finally, a copper oxide and copper samarium oxide dual-phase catalyst with a copper to samarium molar ratio of 4 was obtained. The scanning electron microscope image thereof is shown in FIG. Figure 6 It can be seen that the final copper oxide and copper samarium oxide dual-phase catalyst with a copper to samarium molar ratio of 4 presents a block layer structure.

[0065] Example 5. Preparation of a Dual-Phase Catalyst of Copper Oxide and Copper-Samarium Oxide with a Copper-Samarium Molar Ratio of 2

[0066] The amount of copper nitrate trihydrate in Example 1 was replaced by 2 mmol, the amount of samarium nitrate hexahydrate was replaced by 1 mmol, and the amounts of ammonium carbonate and potassium hydroxide were replaced by 7 mmol and 3 mmol, respectively. Finally, a copper oxide and copper samarium oxide dual-phase catalyst with a copper to samarium molar ratio of 2 was obtained, and its scanning electron microscope image is shown as follows: Figure 7 It can be seen that the final copper oxide and copper samarium oxide dual-phase catalyst with a copper to samarium molar ratio of 2 presents a block layer structure.

[0067] Example 6. Preparation of a Dual-Phase Catalyst of Copper Oxide and Copper-Samarium Oxide with a Copper-Samarium Molar Ratio of 1.5

[0068] The amount of copper nitrate trihydrate in Example 1 was replaced with 1.8 mmol, the amount of samarium nitrate hexahydrate was replaced with 1.2 mmol, and the amounts of ammonium carbonate and potassium hydroxide were replaced with 7 mmol and 3 mmol, respectively. Finally, a copper oxide and copper samarium oxide dual-phase catalyst with a copper to samarium molar ratio of 1.5 was obtained. The scanning electron microscope image thereof is shown in FIG. Figure 8 It can be seen that the final copper oxide and copper samarium oxide dual-phase catalyst with a copper to samarium molar ratio of 1.5 presents a lamellar structure.

[0069] Example 7

[0070] The electrochemical reduction performance of the copper oxide and copper samarium oxide dual-phase catalyst of the present invention was tested using a three-electrode system:

[0071] The reference electrode was a mercury / mercuric oxide electrode, the counter electrode was a nickel foam electrode, and the working electrode was the copper oxide and copper samarium oxide dual-phase catalyst prepared in Examples 1-6.

[0072] The test was carried out in a gas diffusion flow electrolysis cell. The anolyte was 1 mol / L potassium hydroxide, the catholyte was 1 mol / L potassium hydroxide, the reduction currents set for the reduction process were 100, 300, 500, and 700 mA, the reduction time was 20 minutes, and carbon dioxide gas was continuously introduced into the catholyte during the electroreduction process.

[0073] The electrochemical reduction performance of the copper oxide and copper samarium oxide dual-phase catalyst of the present invention is as follows: Figure 9 .

[0074] from Figure 9 It can be seen that the distribution of carbon dioxide reduction products changes significantly with the change of working current (the test time for each working current is 20 minutes). When the working current is 700mA, the Faradaic efficiency of multi-carbon products can reach 81%, and the product current density is 567mA cm -2 .

[0075] The performance of copper oxide and copper samarium oxide dual-phase catalysts with different copper-samarium molar ratios at a working current of 700mA is shown in the figure. Figure 10 .

[0076] from Figure 10 It can be seen that adjusting the copper-samarium molar ratio can effectively control the Faradaic efficiency of carbon dioxide reduction to produce multi-carbon products. A copper oxide and copper-samarium oxide dual-phase catalyst with a copper-samarium molar ratio of 9 effectively promotes carbon-carbon coupling and suppresses the hydrogen evolution reaction, thereby improving the selectivity of the target products of the carbon dioxide reduction reaction. Among them, multi-carbon products include ethylene, ethanol, acetic acid, and n-propanol.

[0077] Example 8

[0078] The catalytic performance stability of the copper oxide and copper samarium oxide dual-phase catalyst was tested using the carbon dioxide reduction test device in Example 7. The copper oxide and copper samarium oxide dual-phase catalyst (prepared in Example 1) with a copper to samarium molar ratio of 9 was selected as the working electrode. The stability test was performed at a working current of 700 mA, and a curve of current, multi-carbon product Faradaic efficiency, and time was obtained as shown below. Figure 11 .

[0079] from Figure 11 It can be seen that the catalyst can maintain its catalytic activity well and hardly decays for 24 hours.

[0080] Comparative Example 1

[0081] Refer to the operation of Example 1, except that: in step a), samarium nitrate hexahydrate is not added to the solution.

[0082] A single-phase copper oxide catalyst was obtained, and its scanning electron microscope image is shown in Figure 12. It can be seen that the copper oxide finally obtained presents a uniform block structure.

[0083] At a working current of 700 mA, the Faradaic efficiency of the multi-carbon products produced by this comparative catalyst is only 51%, and the partial current density of the multi-carbon products is 357 mA cm -2 , which is much worse than the product performance of Example 1, proving the importance of introducing samarium compounds.

Claims

1. A copper-samarium biphasic catalyst, which is a composite material of copper oxide and copper-samarium oxide; The copper-samarium oxide is an oxide having a copper-samarium molar ratio of 1 or 0.5 or a mixture of the two; In the copper-samarium biphasic catalyst, the molar ratio of copper to samarium is not greater than 39; Copper, samarium and oxygen are uniformly distributed in the copper-samarium dual-phase catalyst; The preparation method of the copper-samarium biphasic catalyst comprises the following steps: S1. Prepare aqueous solutions of copper nitrate and samarium nitrate; S2. preparing an aqueous solution of ammonium carbonate and potassium hydroxide as a precipitant solution; S3, adding the precipitant solution to the aqueous solution in step S1, obtaining a solid mixture by precipitation, centrifuging, washing, and then grinding to obtain a powder; S4, calcining the powder in flowing air and hydrogen / argon atmospheres in sequence; The conditions for roasting in the flowing air are as follows: The temperature is 300~400°C and the time is 2~4h; The conditions for calcination in the hydrogen / argon atmosphere are as follows: The temperature is 250~350°C and the time is 2~4h; S5, calcining the powder treated in step S4 in static air; The calcination conditions are as follows: The temperature is 600~800°C and the time is 2~4h.

2. The method for preparing the copper-samarium biphasic catalyst according to claim 1, comprising the steps of: S1. Prepare aqueous solutions of copper nitrate and samarium nitrate; S2. preparing an aqueous solution of ammonium carbonate and potassium hydroxide as a precipitant solution; S3, adding the precipitant solution to the aqueous solution in step S1, obtaining a solid mixture by precipitation, centrifuging, washing, and then grinding to obtain a powder; S4, calcining the powder in flowing air and hydrogen / argon atmospheres in sequence; The conditions for roasting in the flowing air are as follows: The temperature is 300~400°C and the time is 2~4h; The conditions for calcination in the hydrogen / argon atmosphere are as follows: The temperature is 250~350°C and the time is 2~4h; S5, calcining the powder treated in step S4 in static air; The calcination conditions are as follows: The temperature is 600~800°C and the time is 2~4h.

3. The preparation method according to claim 2, wherein: Before step S3, the aqueous solution in step S1 is stirred for 20-40 minutes and then preheated to 50-70°C; In step S3, the precipitant solution is added dropwise to the aqueous solution, stirred, and then heated to 75-85° C. and maintained for 2-4 h.

4. Use of the copper-samarium biphasic catalyst according to claim 1 in the electrocatalytic reduction of carbon dioxide to produce multi-carbon products; The copper-samarium biphasic catalyst is used as a cathode material.

5. A method for preparing multi-carbon products by electrocatalytic reduction of carbon dioxide, comprising the following steps: Using a mercury / mercury oxide electrode as a reference electrode, a nickel foam electrode as a counter electrode, and the copper-samarium biphasic catalyst according to claim 1 as a working electrode, electrochemical reduction is carried out in a gas diffusion flow electrolytic cell to obtain a multi-carbon product.

6. The method according to claim 5, characterized in that: In the gas diffusion type flow electrolytic cell, the anolyte is a potassium hydroxide aqueous solution, and the catholyte is a potassium hydroxide aqueous solution; continuously introducing carbon dioxide gas during the electrochemical reduction process; The current used in the electrochemical reduction is 100-900 mA.

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