Composite electrode material of A-C core-shell structure and preparation method and application thereof

Abstract

The invention relates to a composite electrode material of an A-C core-shell structure, and belongs to the technical field of electrode materials. In the core-shell structure composite electrode material, A is any one element, two elements, three elements, four elements or five elements selected from Mn, Ni, Co, Fe, Cu, Zn, Ru, Pd and Rh; c is RE < x > Ce < 1-x > O < 2 >, and RE is any one element or two elements selected from La, Pr, Nd, Sm and Gd; x is the mole fraction of RE. By improving the interaction between the oxide and the core multi-component alloy and the synergistic effect between the elements, the structural stability and the carbon deposition resistance of the electrode material under the high-temperature condition are remarkably enhanced.

Description

Technical Field

[0001] This invention relates to an A@C core-shell structured composite electrode material, its preparation method, and its application, belonging to the field of electrode material technology. Background Technology

[0002] High-temperature carbon dioxide and water electroreduction technology is considered one of the key pathways to achieving carbon neutrality, especially the reaction carried out in a solid oxide electrolyzer (SOEC) with significant advantages. Compared with low-temperature electroreduction systems, high-temperature processes not only allow the use of pure carbon dioxide and water as feedstock, avoiding side reactions, but also utilize thermodynamic advantages to significantly reduce reaction overpotential, theoretically achieving higher energy conversion efficiency. However, the industrialization of this technology has been severely constrained by catalyst performance limitations. European patent PCT / EP2024 / 069715 discloses a method for preparing a catalyst by encapsulating an optimized Co-Ni alloy core in a stable SDC (Sm2O3-doped CeO2) shell. However, this method only studies the catalyst performance and lifetime under CO2 conditions, without studying the catalyst performance and lifetime under conditions where water vapor and CO2 coexist, and without studying the changes in electrocatalytic products; furthermore, it only discloses single metals or binary alloys, without addressing the influence of the electronic structure of ternary or higher alloys on catalytic performance and lifetime. Meanwhile, the outer core is only Sm-doped CeO2, without the influence of the multi-doped CeO2 coating layer.

[0003] Under practical industrial application conditions, catalysts need to be applied at high current densities (≥1 A cm⁻¹). -2 It needs to operate stably for a long time in harsh environments with high temperatures (around 800℃). Most existing catalyst systems, including single-metal catalysts and metal oxide composite catalysts, face the dilemma of not being able to achieve both activity and stability. Their energy conversion efficiency is generally below 70%, and their operating life is usually less than 200 hours. This is mainly due to problems such as sintering and aggregation of metal active sites caused by high temperatures, as well as carbon deposition during the reaction process. Summary of the Invention

[0004] To address the aforementioned technical problems, this invention provides an A@C core-shell structured composite electrode material. By enhancing the interaction between the oxide and the multi-elemental core alloy, as well as the synergistic effect between elements, this invention significantly improves the structural stability and resistance to carbon deposition of the electrode material under high-temperature conditions. The technical solution of this invention is as follows:

[0005] A composite electrode material with an A@C core-shell structure, wherein A is any one, two, three, four, or five elements selected from Mn, Ni, Co, Fe, Cu, Zn, Ru, Pd, and Rh; and C is RE. xCe 1-x O2, wherein RE is any one or two elements selected from La, Pr, Nd, Sm, and Gd; preferably, when A is two, three, four, or five elements, the elements are in equimolar proportions; x is the mole fraction of RE, 0 ≤ x ≤ 0.3; more preferably, the element combination in the composite electrode material is Ni. 1 / 3 Co 1 / 3 Ru 1 / 3 @SDC, where SDC stands for Sm 0.2 Ce 0.8 O2.

[0006] The present invention also includes a method for preparing composite electrode materials with A@C core-shell structure, the specific steps of which are as follows: (2) Weigh A metal salt precursor, dissolve it in deionized water, stir until completely dissolved, and obtain a metal salt mixed solution;

[0007] Preferably, the mixture is stirred continuously at 300-500 r / min at 100°C until completely dissolved.

[0008] (2) Add a complexing agent to the solution obtained in step (1). The complexing agent is any one or a mixture of any two of citric acid, ethylene glycol, and EDTA. Keep the temperature at 100°C and continue stirring to form a uniform sol system.

[0009] (3) RE is then added to the sol system of step (2). x Ce 1-x O2 nitrate, the RE x Ce 1-x O2 accounts for 10%-50% of the mass fraction of the composite electrode material, where RE is any one or two elements selected from La, Pr, Nd, Sm, and Gd. The mixture is stirred continuously until homogeneous to obtain a mixed solution; x is the mole fraction of RE, 0≤x≤0.3.

[0010] (4) The mixed solution obtained in step (3) is continuously heated at 100°C to evaporate the water. After the system is transformed into a viscous gel, it is transferred to an oven to dry and the precursor dry gel is obtained.

[0011] Preferably, the product is dried in an oven at 300°C for 10-12 hours.

[0012] (7) After grinding the dry gel obtained in step (4) evenly, it is placed in a muffle furnace for segmented calcination: first, the temperature is raised to 600℃ at a heating rate of 5℃ / min and held for 5 hours; then it is naturally cooled to room temperature to obtain A@C powder. The A@C powder is ground and sieved to obtain catalyst powder with encapsulated structure.

[0013] Preferably, the catalyst powder with the encapsulated structure is obtained by sieving through a 100-mesh standard inspection sieve.

[0014] (8) The catalyst powder with the encapsulated structure is ball-milled and then dried to obtain the composite electrode material with the A@C core-shell structure.

[0015] Preferred conditions for ball milling are as follows: The sieved powder is placed in a ball mill jar, and an appropriate amount of anhydrous ethanol is added for ball milling. The solid content is 30%, and the ball-to-powder ratio is 3:1. The ball milling speed is set to 450 r / min, and the milling time is 5 hours. The drying conditions are as follows: the powder is placed in an oven and dried at 80℃ for 10 hours.

[0016] The advantages of this invention compared to the prior art are as follows:

[0017] This invention achieves precise control over the electronic structure and interfacial properties of the material surface by accurately adjusting key parameters such as the proportion of metal elements in A and the type and content of the shell C. Compared with the A / C physically mixed powder prepared by the direct mixing method used in the comparative example, the core-shell structured material prepared by this invention exhibits superior performance at 800℃ and 1 A·cm⁻¹. -2 This novel core-shell electrode material exhibits significantly superior performance in CO2-H2O co-electrolysis under specific conditions, with an approximately 50% increase in current density and a substantial enhancement in resistance to carbon deposition, while also allowing for adjustable syngas composition. This innovative core-shell structure provides a groundbreaking solution for the industrial application of high-temperature CO2-H2O co-electrolysis technology. Attached Figure Description

[0018] Figure 1 The images show the XRD patterns of the electrode material powders obtained in Example 2 and Comparative Example 2, respectively. Detailed Implementation

[0019] The technical solution of the present invention will be described in detail below through specific embodiments. It should be understood that the following specific embodiments are merely exemplary, and any modifications or changes that do not depart from the technical solution design of the present invention should be within the scope of protection of the claims of the present invention. The present invention will be described in detail below with reference to embodiments.

[0020] Example 1

[0021] The Ni@SDC composite electrode material and its preparation method are as follows:

[0022] Step S1: Weigh 5.816g of nickel nitrate hexahydrate and add it to a beaker. Add 50ml of deionized water to the beaker and stir at 100℃ on a constant temperature magnetic stirrer until the metal salt is completely dissolved to obtain a metal nitrate solution.

[0023] Step S2: Prepare a citric acid solution with a mass fraction of 0.1 mol / L. Slowly add the citric acid solution to the metal nitrate solution, and then add ethylene glycol. The molar ratio of citric acid: ethylene glycol: metal ions is 1:1:1. Keep the temperature at 100℃ and continue stirring to form a homogeneous sol system.

[0024] Step S3, according to Sm 0.2 Ce 0.8 To determine the stoichiometric ratio of O2 (SDC), weigh 4.653 g of cerium nitrate hexahydrate and 1.163 g of samarium nitrate hexahydrate, and add them to the sol system in step S2. Continue stirring and heating the solution to evaporate the water until the solution gradually changes from a transparent state to a viscous gel state, accompanied by the generation of numerous bubbles.

[0025] Step S5: Cover the mouth of the beaker with tin foil while leaving a vent hole, transfer it to an oven, and dry it at 300°C for 10 hours to obtain a fluffy black precursor powder.

[0026] Step S6: The precursor powder is placed in a muffle furnace and calcined at high temperature in air. The temperature is increased to 600°C at a heating rate of 5°C / min and held at this temperature for 5 hours. After natural cooling, the obtained Ni@SDC powder is ground in a mortar and sieved through a 100-mesh standard sieve to obtain the catalyst powder with the encapsulated structure.

[0027] Step S7: Place the sieved powder in a ball mill jar, add an appropriate amount of anhydrous ethanol, and ball mill the powder. The solid content is 30%, and the ball-to-powder ratio is 3:1. Set the ball mill speed to 450 r / min and the ball milling time to 5 hours.

[0028] In step S8, the ball-milled slurry is transferred to a beaker and placed in an oven at 80°C for 10 hours to ensure complete evaporation of ethanol, ultimately yielding Ni@SDC catalyst powder with finer particle size and higher activity.

[0029] Example 2

[0030] Ni 0.5 Co 0.5 @SDC Composite Electrode Materials and Preparation Methods

[0031] The preparation steps are the same as in Example 1, except that nickel nitrate and cobalt nitrate are added in step S1, wherein the molar ratio of nickel nitrate to cobalt nitrate is 1:1. Figure 1 Ni synthesized in Example 2 0.5 Co 0.5 XRD analysis of the @SDC composite electrode material. Testing showed that Ni... 0.5 Co 0.5The electrochemical performance of the @SDC composite electrode material in co-electrolysis was demonstrated, with a current density of 0.83 A cm⁻¹ in the electrolytic cell at 850℃. -2 .

[0032] Example 3

[0033] Ni 0.5 Co 0.5 @PDC Composite Electrode Materials and Preparation Methods

[0034] The preparation steps of Example 3 are the same as those of Example 2, except that Sm in step S3... 0.2 Ce 0.8 O2 is Pr 0.2 Ce 0.8 O2 (PDC). Ni was tested. 0.5 Co 0.5 The electrochemical performance of the PDC composite electrode material in co-electrolysis was demonstrated, with a current density of 0.91 A cm⁻¹ in the electrolytic cell at 850℃. -2 .

[0035] Example 4

[0036] Ni 0.5 Ru 0.5 @SDC Composite Electrode Materials and Preparation Methods

[0037] The preparation steps of Example 4 are the same as those of Example 1, except that nickel nitrate and ruthenium chloride are added in step S1, with a molar ratio of nickel nitrate to ruthenium chloride of 1:1. Testing showed that Ni... 0.5 Ru 0.5 The electrochemical performance of the @SDC composite electrode material in co-electrolysis is as follows: the current density of the electrolytic cell at 850℃ is 1.08 A cm⁻¹. -2 .

[0038] Example 5

[0039] Ni 1 / 3 Co 1 / 3 Ru 1 / 3 @SDC Composite Electrode Materials and Preparation Methods

[0040] The preparation steps of Example 5 are the same as those of Example 1, except that nickel nitrate, cobalt nitrate, and ruthenium chloride are added in step S1, with a molar mass ratio of 1:1:1. Ni was tested... 1 / 3 Co 1 / 3 Ru 1 / 3 The electrochemical performance of the @SDC composite electrode material in co-electrolysis was demonstrated, with a current density of 1.60 A cm⁻¹ in the electrolytic cell at 850 °C. -2 .

[0041] Comparative Example 1

[0042] The preparation of Ni / SDC powder includes the following steps:

[0043] Step S1: First, synthesize SDC powder. Based on the stoichiometric ratio of SDC (Ce:Sm = 8:2), weigh cerium nitrate hexahydrate and samarium nitrate hexahydrate, and dissolve them in 50 ml of deionized water. Calculate and add the corresponding amounts of CA and EG based on the molar ratio of citric acid (CA):ethylene glycol (EG):total metal ions (Ce+Sm) of 1:1:1. Stir continuously at 100°C to form a sol, and continue heating to evaporate the water until a gel forms. Place the gel in a 300°C oven for 12 hours, then heat to 600°C in a muffle furnace at a rate of 5°C / min and hold for 5 hours to obtain pure SDC carrier powder.

[0044] Step S2: Place the SDC powder prepared in step S1 into a beaker. Add 50 ml of deionized water to the beaker and stir at 100°C on a constant temperature magnetic stirrer to form an SDC suspension.

[0045] Step S3: Take nickel nitrate hexahydrate and add it to the above SDC suspension. Continue stirring until the metal salt is completely dissolved. The amount of nickel nitrate is the same as in Example 1.

[0046] Step S4: Based on the molar ratio of citric acid (CA): ethylene glycol (EG): total metal ions of 1:1:1, add the weighed CA to a beaker containing deionized water and stir until completely dissolved to form a CA solution with a concentration of 0.5 mol / L.

[0047] Step S5: Slowly add the solution prepared in step S4 to the mixed solution in step S3. Add the weighed EG directly to the above mixed solution and stir continuously at 100°C to form a homogeneous mixture. Continue stirring and heating the solution until the mixture gradually transforms into a viscous gel, accompanied by the generation of numerous bubbles.

[0048] Step S6: Cover the mouth of the beaker with tin foil while leaving a vent hole, and dry it in an oven at 300°C for 10 hours to obtain a fluffy black precursor powder.

[0049] In step S7, the precursor powder from S6 is placed in a muffle furnace and heated to 600°C at a heating rate of 5°C / min in air atmosphere, and held at this temperature for 5 hours. After natural cooling, it is sieved through a 100-mesh standard inspection sieve to obtain Ni / SDC composite catalyst powder.

[0050] Step S8: Place the Ni / SDC composite catalyst powder in a ball mill jar, add an appropriate amount of anhydrous ethanol, and ball mill. The solid content is 50%, the ball-to-material ratio is 3:1, the ball milling speed is set to 450 r / min, and the ball milling time is 5 hours.

[0051] Step S9: Transfer the ball-milled slurry to a beaker and dry it in an 80°C oven for 10 hours to ensure complete evaporation of ethanol, finally obtaining the final Ni / SDC catalyst powder.

[0052] Comparative Example 2

[0053] The synthesis process of Comparative Example 2 is the same as that of Comparative Example 1, except that nickel nitrate and cobalt nitrate are added in step S3, with a molar mass ratio of nickel nitrate to cobalt nitrate of 1:1. The molar masses of nickel nitrate and cobalt nitrate are each half the molar mass of nickel nitrate in Comparative Example 1. Figure 1 Ni synthesized for Comparative Example 2 0.5 Co 0.5 XRD pattern of the / SDC electrode material.

[0054] Comparative Example 3

[0055] The synthesis process of Comparative Example 3 is the same as that of Comparative Example 2, except that the SDC in step S1 is pure CeO2. The molar mass of cerium nitrate weighed is the sum of the molar masses of cerium nitrate and samarium nitrate in step S1.

[0056] Test case

[0057] The prepared catalyst powder was used to fabricate an electrolyte-supported symmetrical cell to evaluate the electrochemical performance of the material. A 20 mm diameter SSZ electrolyte was prepared by tape casting and calcined at 1500 °C for 5 hours to obtain a dense electrolyte sheet. An SDC barrier layer was screen-printed onto both sides of the SSZ and then calcined at 1350 °C for 3 hours. The synthesized Ni-Co@SDC powder was mixed with an organic binder at a ratio of 1:1.5 (5 wt.% ethyl cellulose and 95 wt.% terpineol) and ground for 30–40 min to obtain a cathode electrode slurry. The electrode slurry was uniformly coated onto both sides of the SDC|SSZ|SDC to obtain a symmetrical cell. LSCF-SDC air electrode slurry (purchased from FuelCell Materials) and the cathode electrode material were coated onto both sides of the SDC|SSZ|SDC to obtain a single cell.

[0058] The battery was attached to the testing device and placed in the testing furnace, where it was heated to 850°C at a heating rate of 4°C / min. The testing temperature range was 850°C to 650°C (measurements were taken every 50°C). Water was heated to 81.4°C and CO2 was injected at a flow rate of 50 sccm into the testing device for single-cell testing. The results are shown in Table 1.

[0059] Table 1

[0060]

[0061] The above comparison reveals that the lowest current density in Comparative Example 3 is only 0.26 Acm. -2 The main issue is the relatively low ionic conductivity of the coating layer. Furthermore, as shown in the table, the electrolytic cell current density of the materials synthesized in Examples 1-5 is higher than that of the materials in Comparative Examples 1-3, indicating that coating helps improve the electrochemical performance of the materials. The battery performance of Example 3 is higher than that of Example 2, indicating that the conductivity of the coating material also has a significant impact on battery performance. It was also found that the type of alloy core has a greater impact on battery performance; the highest current density was observed in Example 5, which is due to the addition of the noble metal Ru to the transition metal, significantly improving the electrochemical performance of co-electrolysis.

[0062] Finally, it should be noted that the above descriptions are merely preferred embodiments of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A composite electrode material with an A@C core-shell structure, characterized in that, In the composite electrode material shown, A is any one, two, three, four, or five elements selected from Mn, Ni, Co, Fe, Cu, Zn, Ru, Pd, and Rh; C is RE x Ce 1-x O2, where RE is any one or two elements selected from La, Pr, Nd, Sm, and Gd; x is the mole fraction of RE, 0 ≤ x ≤ 0.

3.

2. The composite electrode material according to claim 1, characterized in that, When A consists of two, three, four, or five elements, each element is in an equimolar ratio.

3. The composite electrode material according to claim 1, characterized in that, The composite electrode material contains Ni. 1 / 3 Co 1 / 3 Ru 1 / 3 @SDC, where SDC stands for Sm 0.2 Ce 0.8 O2.

4. The method for preparing the composite electrode material as described in claim 1, characterized in that, The specific steps of the preparation method are as follows: (1) Weigh out metal salt precursor A, dissolve it in deionized water, and stir until completely dissolved to obtain a mixed solution of metal salts; (2) Add a complexing agent to the solution obtained in step (1). The complexing agent is any one or a mixture of any two of citric acid, ethylene glycol, and EDTA. Keep the temperature at 100°C and continue stirring to form a uniform sol system. (3) RE is then added to the sol system of step (2). x Ce 1-x O2 nitrate, the RE x Ce 1-x O2 accounts for 10%-50% of the mass fraction of the composite electrode material, where RE is any one or two elements selected from La, Pr, Nd, Sm, and Gd. The mixture is stirred continuously until homogeneous to obtain a mixed solution; x is the mole fraction of RE, 0≤x≤0.

3. (4) The mixed solution obtained in step (3) is continuously heated at 100°C to evaporate the water. After the system is transformed into a viscous gel, it is transferred to an oven to dry and the precursor dry gel is obtained. (5) After grinding the dry gel obtained in step (4) evenly, it is placed in a muffle furnace for segmented calcination: first, the temperature is raised to 600℃ at a heating rate of 5℃ / min and held for 5 hours; then it is naturally cooled to room temperature to obtain A@C powder. The A@C powder is ground and sieved to obtain catalyst powder with encapsulated structure. (6) The catalyst powder with the encapsulated structure is ball-milled and then dried to obtain the composite electrode material with the A@C core-shell structure.

5. The preparation method according to claim 4, characterized in that, In step (1), the mixture is stirred continuously at 300-500 r / min at 100°C until completely dissolved.

6. The preparation method according to claim 4, characterized in that, In step (4), the product is dried in an oven at 300°C for 10-12 hours.

7. The preparation method according to claim 4, characterized in that, In step (5), the catalyst powder with the encapsulated structure is obtained by sieving through a 100-mesh standard inspection sieve.

8. The preparation method according to claim 4, characterized in that, The specific conditions for ball milling in step (6) are as follows: the sieved powder is placed in a ball milling jar, an appropriate amount of anhydrous ethanol is added for ball milling, the solid content is 30%, the ball-to-material ratio is 3:1, the ball milling speed is set to 450 r / min, and the ball milling time is 5 hours.

9. The preparation method according to claim 4, characterized in that, The specific drying conditions in step (6) are to place the product in an oven and dry it at 80°C for 10 hours.

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