Multi-metal hydroxide self-supporting integrated activated electrode, preparation and application thereof
By preparing a self-supporting integrated activation electrode of multi-metal hydroxides and using high-current constant current activation to form high-entropy hydroxides, the problem of insufficient activity and stability of OER electrodes was solved, and a low-energy-consumption and high-efficiency water electrolysis process was realized.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- HUNAN NORMAL UNIVERSITY
- Filing Date
- 2024-08-01
- Publication Date
- 2026-05-19
AI Technical Summary
The existing OER electrode catalysts have insufficient activity and high current stability, resulting in high energy consumption in the water electrolysis process, which limits their competitiveness in large-scale applications.
A method for preparing a self-supporting integrated activation electrode using multi-metal hydroxides is adopted. By compositing metal hydroxides on a support and performing high-current constant current activation, high-entropy hydroxides are formed, and suitable physicochemical characteristics are constructed to improve the activity and stability of the OER.
It significantly reduced the OER overpotential, improved the catalytic activity of the electrode and the stability under high current cycling, and achieved excellent OER performance and long-term catalytic stability.
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Figure CN119121282B_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of electrocatalysis, specifically relating to an OER electrocatalytic electrode. Background Technology
[0002] Hydrogen can be used as an energy carrier for energy conversion and storage. Hydrogen can be produced in various ways, the most common being water electrolysis, which uses electricity to break down water into hydrogen (H2) and oxygen (O2). This process can be powered by renewable energy sources such as wind or solar power, making hydrogen production potentially zero-carbon or low-carbon. Furthermore, hydrogen has a high energy density, offering greater potential for long-term energy storage.
[0003] Currently, water electrolysis for hydrogen production is widely used. Water electrolysis can be divided into two half-reactions: the oxygen evolution reaction (OER) at the anode and the hydrogen evolution reaction (HER) at the cathode. Since the OER at the anode is a four-electron transfer process, its kinetics are slower than the HER at the cathode. To achieve the same current density, the OER process requires a higher overpotential, which increases energy consumption during water electrolysis. The large amount of electrical energy input during water electrolysis, especially when producing large quantities of hydrogen, results in high energy consumption. This leads to the high cost of water electrolysis technology, limiting its competitiveness in large-scale applications. Therefore, reducing the overpotential of the OER process is particularly important.
[0004] Traditionally, platinum group metals such as iridium (Ir) and platinum (Pt) have been considered highly efficient OER catalysts, but their high cost and scarcity limit their large-scale application. Therefore, researchers are actively seeking inexpensive and efficient alternatives. Common alternative catalysts include transition metal oxides (such as nickel oxide, molybdenum oxide, and iron oxide) and hydroxides (such as cobalt oxide and nickel hydroxide), as well as nitrogen-doped carbon materials. Further improving the activity and stability of these relatively inexpensive catalysts in various aspects is particularly important. In addition, some metal hydroxide OER materials have been reported in existing technologies, but the OER performance and stability at high currents of these technologies still need improvement. Summary of the Invention
[0005] To address the issues of unsatisfactory catalytic activity and high-current catalytic stability of existing OER electrodes, the primary objective of this invention is to provide a method for preparing a self-supporting integrated activation electrode made of multi-metal hydroxides, aiming to obtain an OER electrode that combines excellent OER catalytic activity with high-current catalytic stability.
[0006] The second objective of this invention is to provide a multi-metal hydroxide self-supporting integrated activation electrode prepared by the aforementioned method and its application in electrocatalysis.
[0007] A method for preparing a multi-metal hydroxide self-supporting integrated activation electrode involves composite metal hydroxides on a carrier to obtain an electrode precursor; the metal hydroxides comprise hydroxides of metal elements M1, M2, and M3; wherein M1 includes at least one of Fe, Co, and Ni; M2 includes at least one of Be, Al, Zn, Ga, In, Sn, Sb, Tl, Pb, Bi, Cr, and Mn; and M3 includes at least one of Cu, Sc, Ti, V, Mo, W, Ru, Rh, Pd, Ag, Cd, Au, Pt, and Ir.
[0008] Then, the electrode precursor is subjected to 200 mA / cm. 2 Constant current activation was performed at the above current density to prepare a multi-metal hydroxide self-supporting integrated activation electrode.
[0009] This invention innovatively demonstrates that by performing constant current activation on a multi-component composite hydroxide containing metals M1-M2-M3 under high current, the effects of high current on the structure and OER degradation can be avoided. Instead, it can promote beneficial physicochemical transformation of the multi-component composite hydroxide, unexpectedly giving it excellent OER activity and high current cycling stability.
[0010] In this invention, the multi-metal hydroxide and its combined constant current activation and current control are key to inducing the physicochemical transformation of the active ingredient and improving its OER activity and high current performance.
[0011] In this invention, the carrier can be a component known in the field of OER that can be used as an electrode material, such as at least one of porous metals, porous carbon materials, and silicon-based materials; further, it can be at least one of nickel foam, copper foam, titanium foam, carbon materials, silicide graphene, and molecular sieves.
[0012] In this invention, the metal hydroxide contains five or more types of metal elements. This invention demonstrates that innovatively employing five or more metal elements comprising M1 / M2 / M3 to form a high-entropy hydroxide, combined with the subsequent high-current constant-current activation, can further enhance the physicochemical characteristics adapted to OER, thereby improving the OER activity and high-current catalytic stability of the prepared material.
[0013] Preferably, the metal M1 includes Fe, Co and Ni; preferably, the molar ratio is 1-4:2-4:2-4; more preferably, it can be 1:2-2.5:2-2.5.
[0014] In this invention, M2 can be at least one of Al and Cr.
[0015] The M3 mentioned can be Cu.
[0016] In this invention, the molar ratio of metals M1, M2 and M3 in the metal hydroxide is 1-8:1-4:1-4; more specifically, it can be 4-6:1:2-3.
[0017] In this invention, the carrier and the dissolved metal solutions of metals M1, M2 and M3 are combined, followed by drying and alkaline precipitation to obtain the electrode precursor.
[0018] Preferably, the total metal concentration in the metal solution is 0.1–4 M, for example, it can be 0.5–2 M.
[0019] Preferably, the metal solution is composited with the support via a spray method. This invention demonstrates that composited metal solution and support via spraying further leverages the metal element and high-current constant-current activation, which facilitates the development of OER-compatible physicochemical characteristics and helps to further enhance its OER activity and catalytic stability.
[0020] Preferably, the alkaline solution used for alkaline precipitation is an aqueous solution of an alkali metal hydroxide;
[0021] Preferably, the concentration of the alkali metal hydroxide in the alkaline solution is above 0.5 M; more preferably, it is 0.5 to 2 M.
[0022] In this invention, the precursor electrode is activated by constant current in an alkaline solution;
[0023] Preferably, the alkaline solution has a concentration of 0.5M or higher, more preferably 0.5-5M, and even more preferably 1-2M aqueous solution of alkali metal hydroxide.
[0024] Preferably, the constant current activation method is a single-electrode, dual-electrode, or triple-electrode method.
[0025] In this invention, the current density during the constant current activation stage is 500 mA / cm². 2 The above is further increased to 500mA / cm. 2 ~1500mA / cm 2 The present invention demonstrates that, at a preferred current density, it is possible to further develop the physicochemical characteristics adapted to OER catalysis, thereby further enhancing the OER activity and catalytic stability of the material.
[0026] In this invention, the constant current activation time is 10 minutes or more, preferably 10 to 600 minutes, and can be further reduced to 20 to 50 minutes to consider efficiency.
[0027] The present invention also provides a multi-metal hydroxide self-supporting integrated activation electrode prepared by the above preparation method.
[0028] In this invention, thanks to the preparation method described above, it is possible to construct OER-adapted physicochemical properties, and the material with the aforementioned properties obtained by the preparation method has both excellent OER performance and catalytic stability.
[0029] The present invention also provides the application of the multi-metal hydroxide self-supporting integrated activation electrode prepared by the above preparation method, which is used as an OER catalytic anode for electrocatalysis;
[0030] Furthermore, the electrocatalysis is at least one of aqueous solution electrocatalysis, carbon dioxide electrocatalytic reduction, and nitrogen fixation electrocatalysis;
[0031] Preferably, the aqueous solution is an alkaline aqueous solution.
[0032] Beneficial effects:
[0033] This invention innovatively activates a multi-component composite hydroxide containing metals M1-M2-M3 under constant current under high current. This avoids the deterioration effect of high current and instead promotes a beneficial physicochemical transformation of the multi-component composite hydroxide, unexpectedly giving it excellent OER activity and high current cycling stability. Attached Figure Description
[0034] Figure 1 This is a SEM image of the unactivated FeCoNiCrCu electrode obtained in step 1 of Example 1.
[0035] Figure 2 In Example 1, step 2, the current density is 1 A / cm². 2 SEM image of the FeCoNiCrCu electrode after 30 min of activation. The layered structure is still retained in a scale-like manner, but the surface is reconstructed under high current stimulation, resulting in an increase in specific surface area and active sites.
[0036] Figure 3 The LSV diagrams are of the FeCoNiCrCu electrode activated in Example 1 and the FeCoNiCrCu electrode activated in Group A of Example 3.
[0037] Figure 4 The activated FeCoNiCrCu self-supporting integrated activation electrode of Example 1 was activated at 1 A / cm 2 Stability test results at current density.
[0038] Figure 5 The activated NiAlCu of Example 2 at 1A / cm 2 LSV plot after activation at current density for 30 min;
[0039] Figure 6 For FeCoNiCrCu at 20mA / cm 2 LSV diagram after activation at current density for 30 min
[0040] Figure 7 This is a SEM image of the FeCoNiCrCu electrode after activation in Example 3B.
[0041] Figure 8 The LSV diagram shows the OER activity of nickel foam in Comparative Example 1.
[0042] Figure 9 The LSV image of 2FeCoNiCrCu after CV activation is shown in the comparative example. Detailed Implementation
[0043] Example 1
[0044] Step (1): Electrode precursor preparation
[0045] 606 mg (1.5 mmol) ferric nitrate nonahydrate, 874 mg (3 mmol) cobalt nitrate hexahydrate, 873 mg (3 mmol) nickel nitrate hexahydrate, 601 mg (1.5 mmol) chromium nitrate nonahydrate, and 725 mg (3 mmol) copper nitrate hexahydrate were dissolved in 10 mL of methanol and stirred for 1 h to form a homogeneous salt solution. A 1 cm × 1.5 cm piece of nickel foam was placed in 1 mol / L hydrochloric acid and sonicated for 30 min, then washed with water and dried in a vacuum oven. 100 μL of the salt solution was atomized and evenly sprayed onto a 1 cm × 1 cm area of the nickel foam using a spray gun, and then dried. After drying, the nickel foam was immersed in 1 mol / L KOH solution. The FeCoNiCrCu composite high-entropy hydroxide OER catalyst precursor was obtained (SEM image shown). Figure 1 ).
[0046] Step (2): Activation
[0047] It was used directly as the working electrode, and then at 1 A / cm 2 A highly active and stable OER catalyst was obtained by constant current activation treatment at a specific current density. Activation was carried out in a normal three-electrode system, with a mercury / mercury oxide electrode as the reference electrode, a Pt sheet electrode as the counter electrode, 1M KOH as the electrolyte, and an activation time of 30 min. A self-supporting integrated activation electrode was fabricated (SEM image shown). Figure 2 ).
[0048] Step (3): OER test
[0049] The activated electrode obtained in step 2 was placed in a three-electrode system for LSV and stability testing at room temperature. This electrode was used as the working electrode, the mercury / mercury oxide electrode as the reference electrode, and the Pt sheet electrode as the counter electrode. The electrolyte was 1M KOH. The electrochemical workstation used was a Gamry Interface 1010E.
[0050] LSV test parameter settings: voltage range is 0.2~1.5V, scan speed is 5mV / s, automatic IR compensation, starting from low potential, to obtain the OER overpotential of the electrode at a current density of 500mA / cm2.
[0051] Stability test parameter settings: The stability test selects the chronovoltammetry method, and the current density is set to 1 A / cm². 2 Add water periodically to maintain a constant electrolyte concentration.
[0052] OER performance test and results:
[0053] LSV data analysis, for ease of comparison, converts the potential relative to mercury / mercury oxide to the potential relative to the standard hydrogen electrode (RHE). Its OER performance is as follows: Figure 3 At 500mA / cm 2 The OER overpotential at current density is only 312.7 mV, which is 50.4 mV lower than before activation.
[0054] At 1A / cm 2 The stability was verified by performing a chronovoltammetric test at a current density of 1 A / cm. The data shows that the integrated electrode can withstand 1 A / cm. 2 Operating at current density for up to 3000 hours without significant change in its OER catalytic performance demonstrates its exceptionally long catalytic stability and activity. The actual operating voltage, converted to a potential relative to the standard hydrogen electrode (RHE), is approximately 1.6V. (After IR compensation, fluctuations in the stability test curves are mainly due to temperature differences and the addition of water during the stability test). Figure 4 .
[0055] Example 2:
[0056] Compared to Example 1, the only difference is that the type and proportion of metals in the precursor metal are changed.
[0057] The metal elements in the electrode precursor are Ni, Al, and Cu (three metals) in a molar ratio of 3-2-3; the activation time is 40 min; the total amount of metal elements and other operations and parameters are the same as in Example 1.
[0058] Activation and testing were performed according to the method in Example 1. The results showed that the performance after activation was better than before activation. The overpotential of the OER at a current density of 500 mA / cm² was observed to be 446 mV. The overpotential of the OER after activation was still 48 mV lower than before activation, indicating the effectiveness of the activation. Figure 5 .
[0059] Example 3: Changing the activation current of constant current
[0060] Compared to Example 1, the only difference is that the current density of the constant current activation in step 2 is changed. The experimental groups are as follows:
[0061] Group A: Current density is 500 mA / cm2;
[0062] Group B: Current density is 20mA / cm2;
[0063] Activation and testing were performed according to the method in Example 1, and the results were as follows:
[0064] Group A: at 500 mA / cm 2 The OER overpotential at the current density was 337.6 mV, which was 25.5 mV lower than before activation. For example... Figure 3 .
[0065] Group B: at 500 mA / cm 2 The OER overpotential at current density was 355.3 mV, which was 7.8 mV lower than before activation, showing little change. The LSV performance graph is shown below. Figure 6 SEM characterization results are as follows Figure 7 .
[0066] Comparative Example 1:
[0067] Compared with Example 1, the only difference is that steps 1 and 2 are omitted, and the described nickel foam is directly used as the working electrode for OER testing, and a blank control is performed.
[0068] The OER test was performed according to the method in Example 1, and the results are as follows:
[0069] At 500 mA / cm 2 The OER overpotential at the current density was 679.8 mV, indicating that the integrated activation electrode prepared by this method can significantly reduce the OER overpotential. Figure 8 .
[0070] Comparative Example 2:
[0071] Compared to Example 1, the difference lies in the activation method in step 2. Instead of using a large constant current activation, a CV (Continuous Voltage) cycle activation method is employed. The CV activation parameters are set as follows: voltage range of 0.2–1.2V (without IR compensation), scan speed of 100mV / s, and 50 cyclic scans. Stable overlap of the curves indicates that the effective value for CV activation has been essentially achieved.
[0072] The OER test was performed according to the method in Example 1, and the results are as follows:
[0073] 500mA / cm 2 The OER overpotential at the current density is 341.1 mV. CV activation also improves the catalyst activity, but not as significantly as high-current activation. Figure 9 .
Claims
1. A method for preparing a self-supporting integrated activation electrode made of multi-metal hydroxide, characterized in that, An electrode precursor is prepared by composite metal hydroxides on a carrier; the metal hydroxides comprise hydroxides of metal elements M1, M2 and M3; wherein, metal M1 comprises Fe, Co and Ni in a molar ratio of 1~4:2~4:2~4; M2 comprises at least one of Al and Zn; and M3 comprises Cu. In the metal hydroxide, the molar ratio of the metals M1, M2 and M3 is 1~8:1~4:1~4; The electrode precursor is then activated by constant current in an alkaline solution to obtain a multi-metal hydroxide self-supporting integrated activation electrode. The current density for constant current activation is greater than 500 mA / cm². 2 Less than or equal to 1500 mA / cm 2 The activation time under constant current is 20~50 min.
2. The method for preparing the multi-element metal hydroxide self-supporting integrated activation electrode as described in claim 1, characterized in that, The carrier includes at least one of porous metal, porous carbon material, and silicon-based material.
3. The method for preparing the multi-element metal hydroxide self-supporting integrated activation electrode as described in claim 2, characterized in that, The carrier is at least one of the following: nickel foam, copper foam, titanium foam, carbon materials, silicide graphene, and molecular sieve.
4. The method for preparing the multi-metal hydroxide self-supporting integrated activation electrode as described in claim 1, characterized in that, The electrode precursor is prepared by combining the carrier with the dissolved metal solutions of metals M1, M2 and M3, followed by drying and alkaline precipitation. The total metal concentration in the metal solution is 0.1~4M; The metal solution is compounded with a carrier by a spraying method; The alkaline solution used for alkaline precipitation is an aqueous solution of an alkali metal hydroxide; The concentration of alkali metal hydroxide in the alkaline solution is above 0.5 M.
5. The method for preparing the multi-element metal hydroxide self-supporting integrated activation electrode as described in claim 1, characterized in that, The alkaline solution activated by constant current is an aqueous solution of alkali metal hydroxide with a concentration of 0.5~5M.
6. The method for preparing the multi-element metal hydroxide self-supporting integrated activation electrode as described in claim 1, characterized in that, The constant current activation method is a single-electrode, two-electrode, or three-electrode method.
7. The method for preparing the multi-metal hydroxide self-supporting integrated activation electrode as described in claim 1, characterized in that, The current density during the constant current activation phase is 1000 mA / cm². 2 .
8. The method for preparing the multi-metal hydroxide self-supporting integrated activation electrode as described in claim 7, characterized in that, The activation time under constant current was 30 minutes.
9. A multi-metal hydroxide self-supporting integrated activation electrode prepared by the preparation method according to any one of claims 1 to 8.
10. The application of a multi-metal hydroxide self-supporting integrated activation electrode prepared by the preparation method according to any one of claims 1 to 8, characterized in that, It was used as the OER catalytic anode for electrocatalysis.
11. The application of the multi-metal hydroxide self-supporting integrated activation electrode prepared by the method described in claim 10, characterized in that, The electrocatalysis described is an aqueous solution-based electrocatalysis.
12. The application of the multi-metal hydroxide self-supporting integrated activation electrode prepared by the method described in claim 11, characterized in that, The aqueous solution is an alkaline aqueous solution.