Preparation and application of alkaline earth metal cation doped ruthenium dioxide catalyst
Patent Information
- Application Number
- CN202610709764.0
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2026-05-21
- Publication Date
- 2026-09-01
AI Technical Summary
[0005]本发明的目的在于克服现有技术中酸性析氧反应催化剂贵金属用量高、活性与稳定性难以兼得的不足，提供一种碱土金属阳离子掺杂二氧化钌催化剂
[0029]3.协同优势：溶胶-凝胶法为发挥碱土金属掺杂的优势提供了理想的平台，其协同作用主要体现在以下几个方面：通过溶胶-凝胶法精确控制掺杂量，可以有效调控Ru的电子态(如降低其d带中心)，从而优化其对含氧中间体(如O、OH、*OOH)的吸附能，加快反应动力学；由于碱土金属离子(如Mg2+，Ca2+，Sr2+，Ba2+)的半径与Ru4+不同，其掺入会在RuO2晶格中引入拉伸应力。这种应力已被证实能够有效调控表面原子的电子结构和反应能垒，是提升催化性能的关键机制之一；掺杂有助于形成更稳定的晶体结构，并能引入氧空位等缺陷，这些都有助于抑制Ru在高电位下的溶解，从而显著提高催化剂的长期耐久性。
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Abstract
Description
Technical Field
[0001] This invention relates to the field of water electrolysis for hydrogen production technology, and more specifically, to a metal cation-doped ruthenium dioxide catalyst for the oxygen evolution reaction in acidic water electrolysis, its preparation by sol-gel method, an electrode containing the catalyst, and its application in water electrolysis for hydrogen production. Background Technology
[0002] Hydrogen, as a clean energy carrier with high energy density and zero carbon emissions, is considered an ideal fossil fuel alternative to solve the energy crisis and environmental pollution problems. Electrolysis of water is one of the most efficient and environmentally friendly methods for producing hydrogen. The water electrolysis process includes the hydrogen evolution reaction at the cathode and the oxygen evolution reaction at the anode. The oxygen evolution reaction, involving a four-electron transfer process, is kineticly slow and is the key bottleneck limiting the overall efficiency of water electrolysis.
[0003] Currently, ruthenium-based and iridium-based oxides (such as RuO2 and IrO2) are considered the best-performing catalysts for the oxygen evolution reaction in acidic electrolytes. However, RuO2 is readily oxidized to soluble RuO4 at high anodic potentials, leading to rapid catalyst deactivation. While IrO2 is more stable than RuO2, it also suffers from dissolution issues during long-term operation, and the high cost and low reserves of the precious metal Ir severely limit its large-scale industrial application.
[0004] Currently, traditional modification strategies for oxygen evolution reaction (OER) catalysts mainly focus on heterogeneous atom doping, alloying, and constructing heterogeneous supported interfaces. Specific preparation methods include high-temperature pyrolysis, molten salt methods, sol-gel methods, hydrothermal methods, and chemical precipitation methods. The sol-gel method is a wet chemical method for preparing metal oxide materials, offering advantages such as uniform raw material mixing, easy component control, and relatively low reaction temperatures, making it particularly suitable for preparing multi-component, uniformly doped oxide catalysts. However, how to precisely control the catalyst's microstructure (e.g., three-dimensional network structure, grain size) and the uniformity of dopant element distribution by optimizing sol-gel process parameters (e.g., complexing agent type, pH value, heat treatment regime) remains a pressing technical problem to be solved in this field. Summary of the Invention
[0005] The purpose of this invention is to overcome the shortcomings of existing acidic oxygen evolution reaction (OER) catalysts, which require high amounts of noble metals and are difficult to balance in terms of both activity and stability, by providing an alkaline earth metal cation-doped ruthenium dioxide catalyst. This catalyst achieves uniform doping of multiple metal elements at the atomic level through a sol-gel method, exhibiting a unique three-dimensional network or porous structure, and demonstrates excellent OER catalytic activity and long-term stability in acidic electrolytes.
[0006] Another objective of this invention is to provide a method for preparing the catalyst, which is simple, reproducible, and can effectively control the distribution of dopant elements and the microstructure of the material.
[0007] Another object of the present invention is to provide an electrode comprising the catalyst and its application in water electrolysis for hydrogen production.
[0008] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be described in detail below with reference to embodiments. Obviously, the described embodiments are merely some embodiments of this invention, and not all embodiments. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.
[0009] In a first aspect, the present invention provides a method for preparing a uniformly doped ruthenium dioxide electrocatalyst with a sheet-like structure in an alkaline earth metal, comprising the following steps:
[0010] S1. Dissolve the ruthenium metal salt precursor, alkaline earth metal salt precursor and chelating agent in deionized water and stir thoroughly to obtain the precursor solution.
[0011] S2. The precursor solution obtained in step S1 is passed through a constant temperature oil bath for sol-gelation after pH adjustment, and then allowed to stand to form a wet gel.
[0012] S3. The wet gel obtained in step S2 is dried in an oven;
[0013] S4. Anneal the dry gel obtained in step S3 in an air atmosphere, wash and vacuum dry to obtain the final product.
[0014] As some specific implementations of the present invention, in step S1, the ruthenium metal salt precursor is any one of ruthenium chloride, ruthenium nitrate, ruthenium acetylacetonate, ruthenium acetate, and other soluble ruthenium salts or organic ruthenium complexes.
[0015] As some specific implementation methods of the present invention, in step S1, the alkaline earth metal salt precursor is any one of magnesium chloride (MgCl2), calcium chloride (CaCl2), strontium chloride (SrCl2), and barium chloride (BaCl2).
[0016] As a specific embodiment of the present invention, in step S1, the chelating agent is citric acid monohydrate, and further includes any one of glucose, tartaric acid, acetylacetone, oxalic acid, ethylenediaminetetraacetic acid, catechol, and sucrose; preferably citric acid monohydrate and tartaric acid. Citric acid monohydrate, as a chelating agent, can react with ruthenium ions (Ru ions) in solution. 3+ ) and alkaline earth metal ions (such as Mg) 2+ Ca 2+、Sr 2+ Ba 2+ This forms stable complexes. This effectively prevents metal ions from agglomerating or undergoing unfavorable hydrolysis reactions during solution evaporation, laying the foundation for subsequent atomic-level mixing. Citric acid, through chelation, stabilizes and locks all metal ions in the network within the solution, ensuring that all components remain mixed at the molecular / atomic level from the initial stage to gelation. This atomic-level homogeneity fundamentally solves the phase separation problem that is extremely common in the preparation of multi-component oxides (especially noble metals and alkaline earth metals).
[0017] As some specific implementation methods of the present invention, in step S1, the mass ratio of the ruthenium metal salt precursor to the alkaline earth metal salt precursor is 50:1 to 5:2, preferably 25:1 to 5:1.
[0018] As some specific implementation methods of the present invention, in step S1, the ratio of the total mass of the metal salt precursor to the mass of the chelating agent is 1:100 to 1:10, preferably 1:80 to 1:20.
[0019] As some specific implementation methods of the present invention, in step S1, the stirring temperature is controlled at 15-35°C and the stirring time is 10-60 min.
[0020] As some specific implementation methods of the present invention, in step S2, the pH range is adjusted to 6-10, preferably 7-8; during the constant temperature oil bath sol-gel process, the temperature range is 60-100℃, preferably 70-90℃, and the heat preservation time ranges from 1 to 8 hours, preferably 3-6 hours.
[0021] As some specific implementations of the present invention, in step S3, the conditions in the oven are maintained at 80-160°C for 6-24 hours, preferably at 100-140°C for 8-16 hours.
[0022] As some specific embodiments of the present invention, in step S4, the annealing process is carried out in a muffle furnace, the annealing temperature is 300-700°C, and the heating rate is 1-10°C / min. -1 Insulation time: 1-12 hours; preferably 400℃, 5 min. -1 , 10h.
[0023] As some specific implementation methods of the present invention, the product obtained in step S4 is a ruthenium dioxide nanocatalyst uniformly doped with alkaline earth metal ions and having a sheet-like structure.
[0024] Secondly, the present invention provides an alkaline earth metal-regulated ruthenium-based electrocatalyst obtained by the preparation method described above, wherein the alkaline earth metal-regulated ruthenium-based electrocatalyst is a sheet-like alkaline earth metal-doped ruthenium dioxide nanomaterial.
[0025] Thirdly, the sheet-like alkaline earth metal-doped ruthenium dioxide nanomaterials described in this invention can be used as an anode oxygen evolution electrocatalyst to improve the energy conversion efficiency and long-term operational stability of the oxygen evolution process in water electrolysis.
[0026] Specifically, the sol-gel method has the following advantages over traditional methods (such as thermal decomposition and coprecipitation):
[0027] 1. Process and Structural Advantages: The core of the sol-gel method lies in its gentle chemical process "from solution to solid." Atomic-level mixing: Unlike traditional solid-phase mixing, this method can achieve atomic-level uniform dispersion of alkaline earth metals (such as Mg, Ca, Sr, Ba) in the RuO2 lattice, forming a true solid solution, which is the structural basis for its performance advantages. This method is more conducive to the synthesis of nanomaterials with high specific surface area and porous network structure, which can expose more catalytic active sites, which is difficult to achieve with traditional high-temperature sintering methods.
[0028] 2. Performance Advantages: Traditional RuO2 catalysts generally suffer from the bottleneck of balancing activity and stability. The introduction of alkaline earth metal doping provides an effective way to solve this core problem: synergistic enhancement of catalytic activity and stability: Doped alkaline earth metal atoms can significantly improve the catalytic activity and long-term operational stability of RuO2 in key reactions (such as the acidic oxygen evolution reaction) by modulating its electronic structure and lattice stress. Furthermore, the price of partially doped alkaline earth metals is much lower than that of the precious metal ruthenium; therefore, while maintaining or even improving performance, the doping strategy also helps reduce material costs.
[0029] 3. Synergistic Advantages: The sol-gel method provides an ideal platform for leveraging the advantages of alkaline earth metal doping. Its synergistic effects are mainly reflected in the following aspects: By precisely controlling the doping amount through the sol-gel method, the electronic states of Ru can be effectively regulated (e.g., lowering its d-band center), thereby optimizing its adsorption energy for oxygen-containing intermediates (such as O, OH, *OOH) and accelerating reaction kinetics; due to the alkaline earth metal ions (such as Mg...)... 2+ Ca 2+ Sr 2+ Ba 2+ The radius of ) and Ru 4+ Unlike other catalysts, RuO2 doping introduces tensile stress into the RuO2 lattice. This stress has been shown to effectively modulate the electronic structure of surface atoms and the reaction energy barrier, and is one of the key mechanisms for improving catalytic performance. Doping helps to form a more stable crystal structure and can introduce defects such as oxygen vacancies, which help to suppress the dissolution of Ru at high potentials, thereby significantly improving the long-term durability of the catalyst. Attached Figure Description
[0030] Other features, objects, and advantages of the present invention will become more apparent from the following detailed description of non-limiting embodiments with reference to the accompanying drawings:
[0031] Figure 1 SEM images of sheet-like alkaline earth metal-doped ruthenium dioxide nanomaterials prepared according to Examples 1, 2, 3, 4, 5, 6, 7 and Comparative Example 1 of the present invention.
[0032] Figure 2 XRD patterns of materials prepared according to Examples 1 and 7 and Comparative Example 1 of the present invention;
[0033] Figure 3 XPS image of the material prepared according to Example 1 of the present invention;
[0034] Figure 4 OER curves of the catalysts prepared in Examples 1, 2, 3 and Comparative Example 1 after IR compensation polarization;
[0035] Figure 5 The OER polarization curves of the catalysts prepared in Examples 1 and 4 without IR compensation are shown.
[0036] Figure 6 OER polarization curves of the catalysts prepared in Examples 1 and 5 and 6 without IR compensation;
[0037] Figure 7 OER polarization curves of the catalysts prepared in Examples 1, 7 and Comparative Example 1 after IR compensation.
[0038] Figure 8 The results are the stability test results for the catalysts prepared in Examples 1 and 3. Detailed Implementation
[0039] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be described in detail below with reference to embodiments. Obviously, the described embodiments are merely some embodiments of this invention, and not all embodiments. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.
[0040] Example 1
[0041] The porous alkaline earth-regulated ruthenium-based electrocatalyst of this embodiment is prepared by a method including the following steps:
[0042] Precursor solution preparation: (1) Add 2.1g of chelating agent citric acid monohydrate to a beaker containing 20mL of deionized water, stir for 5min to mix evenly, add 50mg of ruthenium chloride (RuCl3) and 3mg of anhydrous calcium chloride (CaCl2), stir for 20min, then add ammonia water dropwise to adjust pH=8.
[0043] Evaporation solvent: (2) The obtained mixture was placed in an oil bath and stirred, and kept at 80°C for 4.5 h to evaporate and obtain a sol-like precursor.
[0044] Dry gelation: (3) Transfer the precursor to a 100ml crucible and place it in an oven at 120℃ for 12h to obtain a porous dry gel.
[0045] Annealing treatment: (4) Grind the dry gel into powder, and then anneal it in an air atmosphere at 400°C for 10 h using a muffle furnace, with a heating rate of 5°C / min. -1 After natural cooling, the sample was washed with deionized water, centrifuged, and dried at 60°C for 12 hours to obtain the Ca-RuO2 catalyst.
[0046] Example 2:
[0047] The only difference between it and Example 1 is that in step (1), the amount of anhydrous CaCl2 used is 1 mg.
[0048] Example 3:
[0049] The only difference between it and Example 1 is that in step (1), the amount of anhydrous CaCl2 used is 5 mg.
[0050] Example 4:
[0051] The only difference between it and Example 1 is that in step (1), the chelating agent citric acid monohydrate is replaced with tartaric acid.
[0052] Example 5:
[0053] The only difference between it and Example 1 is that in step (4), the annealing temperature is 500°C.
[0054] Example 6:
[0055] The only difference between it and Example 1 is that in step (4), the annealing temperature is 600°C.
[0056] Example 7:
[0057] The only difference between it and Example 1 is that in step (1), the anhydrous CaCl2 of the alkaline earth metal salt is replaced with 5 mg MgCl2·6H2O.
[0058] Comparative Example 1:
[0059] Precursor solution preparation: (1) Add 2.1g of chelating agent citric acid monohydrate to a beaker containing 20mL of deionized water, stir for 5min to mix evenly, add 50mg of RuCl3, stir for 20min, then add ammonia water dropwise to adjust pH=8.
[0060] Evaporation solvent: (2) The obtained mixture was placed in an oil bath and stirred, and kept at 80°C for 4.5 h to evaporate and obtain a sol-like precursor.
[0061] Dry gelation: (3) Transfer the precursor to a 100ml crucible and place it in an oven at 120℃ for 12h to obtain a porous dry gel.
[0062] Annealing treatment: (4) Grind the dry gel into powder, and then anneal it in an air atmosphere at 400°C for 10 h using a muffle furnace, with a heating rate of 5°C / min. -1 After natural cooling, it was washed with deionized water, centrifuged, and dried at 60°C for 12 h to obtain the RuO2 catalyst.
[0063] Results and Tests
[0064] (1) Morphological characteristics
[0065] The catalyst prepared in Example 1 was subjected to scanning electron microscopy (SEM) testing, and the results are as follows: Figure 1 As shown in a.
[0066] The catalyst prepared in Example 2 was subjected to scanning electron microscopy (SEM) testing, and the results are as follows: Figure 1 As shown in b.
[0067] The catalyst prepared in Example 3 was subjected to scanning electron microscopy (SEM) testing, and the results are as follows: Figure 1 As shown in c.
[0068] The catalyst prepared in Example 4 was subjected to scanning electron microscopy (SEM) testing, and the results are as follows: Figure 1 As shown in d.
[0069] The catalyst prepared in Example 5 was subjected to scanning electron microscopy (SEM) testing, and the results are as follows: Figure 1 As shown in e.
[0070] The catalyst prepared in Example 6 was subjected to scanning electron microscopy (SEM) testing, and the results are as follows: Figure 1 As shown in f.
[0071] The catalyst prepared in Example 7 was subjected to scanning electron microscopy (SEM) testing, and the results are as follows: Figure 1 As shown in g.
[0072] The catalyst prepared in Comparative Example 1 was subjected to scanning electron microscopy (SEM) testing, and the results are as follows: Figure 1 As shown in h.
[0073] from Figure 1 It can be seen that the alkaline earth metal-doped ruthenium dioxide electrocatalysts prepared in Examples 1, 2, 3, 4, 5, 6, 7 and Comparative Example 1 are sheet-like nanomaterials;
[0074] (2) Phase characterization
[0075] X-ray diffraction (XRD) tests were performed on the products obtained in Examples 1, 7, and Comparative Example 1. The results are as follows: Figure 2 As shown. From Figure 2 The XRD patterns show that the XRD patterns of the alkaline earth metal-doped ruthenium dioxide electrocatalysts prepared in Examples 1 and 7 and the ruthenium dioxide electrocatalyst prepared in Comparative Example 1 match the PDF card of ruthenium dioxide, and no phase separation phenomenon is observed. As the doping radius of alkaline earth metal ions increases, the diffraction intensity of ruthenium dioxide decreases, indicating that defects increase.
[0076] The product obtained in Example 1 was subjected to X-ray photoelectron spectroscopy (XPS) analysis, and the results are as follows: Figure 3 As shown. From Figure 3 The XPS spectra show that Ca was successfully doped into the alkaline earth metal-doped ruthenium dioxide electrocatalyst prepared in Example 1.
[0077] (3) Electrochemical performance testing
[0078] The electrochemical performance of the products obtained in each embodiment and comparative example was tested. The specific test methods are as follows:
[0079] The evaluation was conducted using a three-electrode system. The electrolyte was a 0.5 M H2SO4 solution (pH≈0). The working electrode was an electrode prepared from the electrocatalysts obtained in each example and comparative example. The counter electrode was a platinum wire, and the reference electrode was a saturated calomel electrode (SCE). All test potentials were converted to potentials relative to the reversible hydrogen electrode (RHE).
[0080] The results are as follows Figure 4 , 5 Figures 6 and 7 show the electrochemical polarization curves of the electrocatalysts prepared in each embodiment and comparative example in a three-electrode reaction cell with 0.5 M H₂SO₄ electrolyte; from Figure 4 As can be seen, the catalyst prepared in Example 1 exhibits the optimal current density, requiring only a low overpotential (175 mV) to drive a 10 mA cm⁻¹ current. -2 The current density of the water electrolysis oxygen evolution reaction was similar in Example 2 (low Ca doping) to that of Comparative Example 1 (undoped), while the Ca doping density of Example 3 (high Ca doping) was slightly lower than that of Example 1. Figure 5It can be seen that both Examples 4 and 5, with their increased annealing temperatures, reduce catalyst activity, with Example 5, annealed at 600°C, exhibiting very poor catalytic activity; from Figure 6 It can be seen that in Example 6, where tartaric acid was used as the chelating agent, the catalyst prepared using citric acid monohydrate as the chelating agent did not perform as well as the catalyst. Figure 7 It can be seen that the overpotential of Example 7, which modifies the alkaline earth metal element Mg doping, and Comparative Example 1, which uses self-made ruthenium dioxide, are much greater than that of Example 1, and their electrocatalytic performance is far inferior to that of Example 1.
[0081] To evaluate the durability of the prepared electrocatalysts, 10 mA cm⁻¹ tests were conducted on Examples 1 and 3 under the same system. -2 The constant current polarization test under current density recorded the voltage change over time, and the results are as follows: Figure 7 As shown. From Figure 8 The galvanostatic polarization curves show that the oxygen evolution performance of the sheet-like ruthenium dioxide in Example 1, which is regulated by an appropriate amount of alkaline earth elements, can be maintained for more than 2000 hours under acidic conditions, while the stability of the sheet-like catalyst in Example 3, which is regulated by a high amount of calcium doping, is relatively poor.
[0082] Therefore, this invention constructs an alkaline earth-doped ruthenium dioxide electrocatalyst with a lamellar structure using the sol-gel method. A chelating agent coordinates the dopant element with the host element, ensuring uniform distribution and no phase separation during annealing and pyrolysis. The doping with appropriate amounts of alkaline earth metal ions optimizes mass transfer efficiency while endowing the catalyst with a high specific surface area and abundant surface defects, significantly increasing the density of active sites. Building upon this structural advantage, the uniformly doped alkaline earth elements further enhance the intrinsic activity of the catalyst by regulating the electronic structure of ruthenium dioxide, while stabilizing the valence state of ruthenium and inhibiting acidic dissolution. Appropriate alkaline earth metal doping also reduces the destructive force of alkaline earth metal ion dissolution on the catalyst structure during acidic OER processes, thus overcoming the bottleneck of rapid deactivation in traditional ruthenium-based catalysts.
[0083] The specific embodiments of the present invention have been described above. It should be understood that the present invention is not limited to the specific embodiments described above, and those skilled in the art can make various modifications or variations within the scope of the claims, which do not affect the essence of the present invention.
Claims
1. An acidic water electrolysis catalyst doped with alkaline earth metal cations and noble metal oxides, characterized in that, The catalyst has the following general chemical formula: M-RuO2, where M is an alkaline earth metal element; the catalyst is prepared by sol-gel method, has a three-dimensional network or porous structure, and the doped metal cation M is uniformly distributed in the oxide lattice.
2. The metal cation-doped oxide acidic water electrolysis catalyst according to claim 1, characterized in that, The M-position is selected from at least one of the elements Mg, Ca, Sr, and Ba.
3. The alkaline earth metal cation-doped oxide acidic water electrolysis catalyst according to claim 1 or 2, characterized in that, The catalyst has a rutile, anatase, or perovskite structure, with an alkaline earth doping content ranging from 1% to 40%.
4. A sol-gel method for preparing an alkaline earth metal cation-doped oxide acidic water electrolysis catalyst as described in any one of claims 1-3, characterized in that, Includes the following steps: (1) Dissolve the raw materials containing the doped alkaline earth metal element M metal source and ruthenium source in a solvent, add a chelating agent, adjust the pH value, and form a uniform mixed solution. (2) The mixed solution obtained in step (1) is heated under stirring to cause hydrolysis and condensation reaction to form a sol; (3) The sol obtained in step (2) is aged to form a wet gel; (4) Dry the wet gel obtained in step (3) to obtain the dry gel precursor; (5) The dry gel precursor obtained in step (4) is heat-treated in an oxygen-containing atmosphere to obtain the metal cation-doped oxide acidic water electrolysis catalyst.
5. The preparation method according to claim 4, characterized in that, The complexing agent in step (1) is at least one of citric acid, glucose, tartaric acid, acetylacetone, oxalic acid, ethylenediaminetetraacetic acid, catechol, and sucrose; the metal source is at least one of nitrate, chloride, acetate, or alkoxide.
6. The preparation method according to claim 4 or 5, characterized in that, In step (2), the temperature range of the constant temperature oil bath sol-gel process is 60-100℃, preferably 70-90℃, and the heat preservation time range is 1-8h, preferably 3-6h; the aging time in step (3) is 0.1-4h.
7. The preparation method according to any one of claims 4 to 6, characterized in that, The drying temperature in step (4) is 80–160℃, and the drying time is 6–24 h; the heat treatment temperature in step (5) is 300–700℃, and the heating rate is 1–10℃ / min. -1 The heat preservation time is 1 to 12 hours, preferably 400℃, with a minimum temperature of 5℃ for 5 minutes. -1 , 10h, to remove organic matter and form a metal cation-doped oxide crystal structure.
8. The preparation method according to any one of claims 4 to 7, characterized in that, In step (1), the mass ratio of metal ions to complexing agent is 1:100 to 1:10, preferably 1:80 to 1:20; the pH range is adjusted to 6 to 10, preferably 7 to 8.
9. The application of an alkaline earth metal cation-doped oxide acidic water electrolysis catalyst as described in any one of claims 1 to 3 in water electrolysis for hydrogen production, characterized in that, The catalyst is used as an anode catalyst for the oxygen evolution reaction in acidic electrolytes.
10. An anode electrode for water electrolysis, characterized in that, The electrode comprises the alkaline earth metal cation-doped noble metal oxide acidic water electrolysis catalyst according to any one of claims 1 to 3, as well as a conductive substrate and a binder.