A ruthenium-based catalyst for acidic oxygen evolution reaction, and a preparation method and application thereof

Abstract

This invention relates to the field of functional materials technology, and discloses a ruthenium-based catalyst for the acidic oxygen evolution reaction (OER), its preparation method, and its application. The preparation method includes dissolving 100-200 parts by mass of RuCl3·H2O and 1-40 parts by mass of VCl3 in 20-60 parts by volume of anhydrous methanol, stirring to obtain a mixed solution; slowly adding hydrazine hydrate dropwise to the mixed solution, continuing stirring, centrifuging and filtering; washing alternately with anhydrous methanol and ultrapure water, freeze-drying, and heat-treating at 300-500℃ for 1-4 hours to obtain a V-doped RuO2 catalyst. The prepared V-RuO2 catalyst exhibits excellent initial activity and long-term durability under acidic conditions, providing a new solution for developing high-performance anode catalysts suitable for proton exchange membrane water electrolyzers.

Description

Technical Field

[0001] This invention belongs to the field of functional materials technology, and specifically relates to a vanadium-doped ruthenium dioxide catalytic material, specifically a ruthenium-based catalyst for acidic oxygen evolution reaction, its preparation method, and its application. Background Technology

[0002] Hydrogen energy, as a clean and efficient secondary energy carrier, has seen its production technology become a key link in the energy transition. Developing green and efficient hydrogen energy technologies is crucial for addressing the global energy crisis and achieving carbon neutrality. Proton exchange membrane water electrolysis technology has become one of the promising hydrogen production routes due to its high efficiency, high hydrogen purity, and fast response speed. However, in this technology, the OER kinetics at the anode are slow, which severely limits its large-scale commercial application, especially in strongly acidic, high-potential, and strongly oxidizing environments, placing extremely high demands on the activity and stability of the electrocatalyst.

[0003] Among numerous acidic oxygen evolution catalyst systems, iridium-based (such as IrO2) and ruthenium-based (such as RuO2) oxides are ideal follow-up materials. However, Ir's extremely low crustal abundance and high cost severely limit its large-scale application. In contrast, RuO2 exhibits higher intrinsic activity and relatively lower cost, making it a current research hotspot. However, during long-term operation, the Ru in the crystal lattice... 4+ It is easily further oxidized to soluble RuO4. 2- Dissolving into the electrolyte leads to the loss of active components and damage to the catalyst structure, resulting in insufficient stability and performance degradation. Therefore, how to improve catalytic activity while maintaining material stability has become a key scientific problem that urgently needs to be solved in this field.

[0004] To overcome this challenge, researchers commonly employ elemental doping strategies to optimize the performance of RuO2. By introducing suitable dopant elements, the electronic structure of Ru active sites can be modulated, enhancing the Ru-O bond strength and thus improving catalyst activity and resistance to peroxidation. However, reported dopant elements such as nickel, cobalt, and copper exhibit insufficient stability in strongly acidic environments, easily leaching from the crystal lattice and accelerating catalyst deterioration, resulting in the opposite of the desired doping effect. Furthermore, various methods exist for preparing RuO2 catalysts, such as the sol-gel method and the molten salt method, but these methods suffer from complex processes, high energy consumption, or uneven product particle size.

[0005] Therefore, developing a dopant element that can form a stable solid solution with RuO2 and effectively improve its catalytic performance, along with a corresponding simple preparation method, is of great scientific significance and application value. Summary of the Invention

[0006] To address the problem that existing technologies using elemental doping to optimize the performance of RuO2 suffer from insufficient stability of the dopant elements in strong acids, leading to easy leaching from the crystal lattice and an inability to maintain long-term stability while enhancing the catalytic activity of RuO2, this invention provides a ruthenium-based catalyst for the acidic oxygen evolution reaction, its preparation method, and its application.

[0007] This invention is achieved using the following techniques: This invention provides a method for preparing a ruthenium-based catalyst for the acidic oxygen evolution reaction, comprising the following steps: S1, take 100-200 parts by mass of RuCl3·H2O and 1-40 parts by mass of VCl3 and dissolve them in 20-60 parts by volume of anhydrous methanol, stir to obtain a mixed solution, and stir for a time greater than or equal to 0.5 h, wherein the mass parts are expressed in mg and the volume parts are expressed in ml; S2, slowly add 0.1~0.4 volume parts of hydrazine hydrate, the concentration of which is 80wt%, to the mixed solution prepared in step S1, and continue stirring for a stirring time of ≥4h. After the reaction is completed, centrifuge and filter to collect the solid. S3, the solid collected in step S2 is washed with anhydrous methanol and ultrapure water alternately, and then freeze-dried for 10-20 hours to obtain the precursor catalyst; S4. The precursor catalyst prepared in step S3 is heat-treated at 300~500℃ for 1~4h in a muffle furnace with a heating rate of 1~5℃ / min to obtain the V-doped RuO2 catalyst.

[0008] In existing technologies, there are various methods for preparing RuO2 catalysts, such as the sol-gel method and the molten salt method. However, these methods are complex, energy-intensive, or produce products with uneven particle size. The method described above uses a liquid-phase reduction-thermal treatment method, which is simple to operate and has successfully synthesized a high-performance V-uniformly doped RuO2 catalyst (V-RuO2).

[0009] The present invention also provides a ruthenium-based catalyst for acidic oxygen evolution reaction prepared by the above preparation method. The ruthenium-based catalyst has a rutile phase structure, with V uniformly doped in the RuO2 lattice, and the RuO2 lattice fringes are distorted and produce locally highly active sites.

[0010] Compared to various dopants in the prior art, V has advantages due to its unique electronic configuration (3d). 3 4s 2The variable oxidation states (+3 to +5) and atomic radii similar to Ru (Ru: 0.68 Å, V: 0.71 Å) make it easy to incorporate into the RuO2 lattice to form a stable rutile phase structure. According to existing theoretical studies, V incorporation can significantly alter the band structure of RuO2 through d-orbital hybridization, while simultaneously inducing lattice distortion to generate locally highly active sites, offering a promising opportunity to simultaneously improve catalytic activity and stability.

[0011] The present invention also provides the application of the above-mentioned ruthenium-based catalyst in the acidic oxygen evolution reaction.

[0012] Specifically, it is used as an anode electrocatalyst in acidic water electrolysis oxygen evolution catalyst systems.

[0013] Introducing V into the RuO2 lattice effectively modulates the electronic environment of the central metal Ru, thereby optimizing the adsorption / desorption energy barriers of reaction intermediates at active sites and simultaneously improving the catalyst's activity and stability. Furthermore, the partial substitution of the noble metal Ru by the transition metal V also reduces the overall cost of the catalyst. Compared to self-made pure RuO2, the V-RuO2 catalyst exhibits superior catalytic performance in acidic OER.

[0014] Compared with the prior art, the present invention has the following beneficial effects: This invention provides a ruthenium-based catalyst for the acidic oxygen evolution reaction, its preparation method, and its application. It employs a two-step method combining hydrazine hydrate liquid-phase reduction and medium-temperature heat treatment. On one hand, hydrazine hydrate is used as a strong reducing agent to rapidly co-reduce Ru. 3+ and V 5+ (or V) 3+ This process forms a uniform Ru-V precursor, laying the foundation for the subsequent formation of uniformly doped oxides. Compared to existing preparation methods such as hydrothermal methods, this method has lower equipment requirements, shorter reaction time, lower energy consumption, and a simpler process, making it very suitable for large-scale production.

[0015] The V-doped RuO2 catalyst prepared in this invention possesses a regular rutile phase structure. V doping effectively modulates the electronic environment of the Ru active centers, reduces their d-band centers, and optimizes the adsorption / desorption behavior of reaction intermediates, thereby lowering the reaction overpotential and enhancing intrinsic activity. Simultaneously, the introduction of V strengthens the Ru-O bond, improves the stability of lattice oxygen, and effectively inhibits the peroxidation of active Ru species to soluble RuO4 under high pressure. 2- The process. Therefore, the catalyst prepared in this invention exhibits long-term operational stability far exceeding that of pure RuO2 under harsh acidic OER conditions.

[0016] Electrochemical tests showed that the V-RuO2 catalyst prepared in this invention exhibited lower overpotential and higher quality activity in 0.5M H2SO4 solution compared to pure RuO2 prepared by the same method, and its performance degradation rate was significantly reduced in long-term stability tests. Attached Figure Description

[0017] Figure 1 The image shows the SEM image of the catalyst prepared in Comparative Example 1.

[0018] Figure 2 The image shows a SEM image of the catalyst prepared in Example 1.

[0019] Figure 3 TEM image of the catalyst prepared in Comparative Example 1.

[0020] Figure 4 The image shows a TEM image of the catalyst prepared in Example 1.

[0021] Figure 5 The image shows the HRTEM image of the catalyst prepared in Comparative Example 1.

[0022] Figure 6 The image shows an HRTEM image of the catalyst prepared in Example 1.

[0023] Figure 7 This is an EDS mapping diagram of the catalyst prepared in Example 1.

[0024] Figure 8 The XRD patterns are for the catalysts prepared in Comparative Example 1 and Example 1.

[0025] Figure 9 Raman diagrams of the catalysts prepared in Comparative Example 1 and Example 1.

[0026] Figure 10 Ru 3p plots for the catalysts prepared in Comparative Example 1 and Example 1.

[0027] Figure 11 The image shows the V 2p plot of the catalyst prepared in Example 1.

[0028] Figure 12 Polarization curves of the catalysts prepared for Comparative Example 2, Comparative Example 1 and Example 1.

[0029] Figure 13 Tafel slope diagrams for the catalysts prepared in Comparative Example 2, Comparative Example 1, and Example 1.

[0030] Figure 14 EIS diagrams of the catalysts prepared in Comparative Example 1 and Example 1.

[0031] Figure 15C1 of the catalysts prepared for Comparative Example 2, Comparative Example 1, and Example 1 dl Value graph.

[0032] Figure 16 Specific activity diagrams of the catalysts prepared for Comparative Example 2, Comparative Example 1 and Example 1.

[0033] Figure 17 Mass activity diagrams of the catalysts prepared for Comparative Example 2, Comparative Example 1, and Example 1.

[0034] Figure 18 The stability graph shows the catalyst prepared in Example 1.

[0035] Figure 19 CV curves for the catalysts prepared in Comparative Example 1 and Example 1.

[0036] Figure 20 The polarization curves are for the catalysts prepared in Examples 2 and 3. Detailed Implementation

[0037] The specific embodiments of the present invention will be described in detail below. Example 1

[0038] A method for preparing a ruthenium-based catalyst for the acidic oxygen evolution reaction includes the following steps: S1, dissolve 112.7 mg of RuCl3·H2O and 7.8 mg of VCl3 in 40 ml of anhydrous methanol, stir for at least 0.5 h to obtain a mixed solution; S2, 0.2430 ml of 80 wt% hydrazine hydrate is slowly added dropwise to the mixed solution prepared in step S1, and the reaction is continued to be stirred for 5 h. After the reaction is completed, the solid is collected by centrifugation and filtration. S3, the solid collected in step S2 was washed three times with anhydrous methanol and ultrapure water alternately, and then freeze-dried for 12 h to obtain the precursor catalyst; S4. The precursor catalyst prepared in step S3 is placed in a muffle furnace and heated to 400°C at a heating rate of 5°C / min. After heat treatment for 2 hours, V-doped RuO2 catalyst is obtained, denoted as V-RuO2. Example 2

[0039] A method for preparing a ruthenium-based catalyst for the acidic oxygen evolution reaction includes the following steps: In step S1, 112.7 mg of RuCl3·H2O and 15.6 mg of VCl3 were used as raw materials, and the rest was completely consistent with Example 1 to prepare a V-doped RuO2 catalyst, denoted as V-RuO2-1. Example 3

[0040] A method for preparing a ruthenium-based catalyst for the acidic oxygen evolution reaction includes the following steps: In step S1, 112.7 mg of RuCl3·H2O and 31.2 mg of VCl3 were used as raw materials, and the rest was completely consistent with Example 1 to prepare a V-doped RuO2 catalyst, denoted as V-RuO2-2. Comparative Example 1

[0041] A method for preparing a ruthenium-based catalyst for the acidic oxygen evolution reaction, wherein VCl3 is not added during the reaction, includes the following steps: In step S1, 112.7 mg of RuCl3·H2O was used as raw material, and the rest was completely consistent with Example 1 to prepare V-doped RuO2 catalyst, denoted as H-RuO2. Comparative Example 2

[0042] Commercially available RuO2 powder, namely commercial RuO2 (Commercial ruthenium oxide), was used, denoted as C-RuO2.

[0043] The catalyst samples prepared in Comparative Example 1, Comparative Example 2, and Examples 1-3 were tested. Structural characterization

[0044] The V-RuO2 catalyst prepared in Example 1 and the H-RuO2 catalyst prepared in Comparative Example 1 were characterized by scanning electron microscopy (SEM), and the results are as follows: Figure 1 and Figure 2 As shown in the figure, both catalysts exhibit a nanoparticle morphology, indicating that the introduction of V did not change the basic morphology of the catalysts.

[0045] Transmission electron microscopy (TEM) was used to characterize the V-RuO2 and H-RuO2 catalysts, such as... Figure 3 and Figure 4 As shown in the figure, both catalysts maintain a uniformly distributed nanoparticle morphology, with no large agglomerates present.

[0046] High-lens transillumination (HRTEM) characterization was performed on the V-RuO2 and H-RuO2 catalysts, and the results are as follows: Figure 5 and Figure 6 As shown in the figure, H-RuO2 exhibits obvious lattice fringes, while V-RuO2 displays weaker lattice fringes, indicating that the introduction of V reduces the crystallinity of the catalyst. Furthermore, the lattice fringes in V-RuO2 show a distortion phenomenon, indicating that V causes strain in the local structure of the catalyst, thereby modulating the charge structure of the material. More significantly, V-RuO2 also contains a small number of amorphous regions, which provide abundant active sites for the catalyst. Component analysis

[0047] EDS surface scan analysis of the V-RuO2 catalyst yielded the following results: Figure 7 As shown in the figure, V is uniformly distributed in the catalyst, indicating that V has been successfully incorporated into RuO2.

[0048] X-ray diffraction characterization of V-RuO2 and H-RuO2 catalysts was performed, and the results are as follows: Figure 8 As shown in the figure, the introduction of V into RuO2 maintains the original structure, but the crystallinity is relatively reduced, which is consistent with the results of HRTEM.

[0049] Raman spectroscopy was performed on V-RuO2 and H-RuO2 catalysts, and the results are as follows: Figure 9 As shown in the figure, both exhibit similar characteristic peaks, indicating that they have similar structures.

[0050] Electronic structure analysis X-ray photoelectron spectroscopy (Ru 3p) analysis was performed on V-RuO2 and H-RuO2 catalysts, and the results are as follows: Figure 10 As shown in the figure, the valence state of Ru is effectively suppressed after the introduction of V, indicating that electrons are transferred from V to Ru, which can inhibit the peroxidation of Ru.

[0051] X-ray photoelectron spectroscopy (V 2p) analysis of the V-RuO2 catalyst yielded the following results: Figure 11 As shown in the figure, V in the catalyst maintains multiple valence states, which may play a regulatory role in the valence state of Ru. Performance testing

[0052] Electrochemical performance was tested using a standard three-electrode system: the catalyst was drop-coated onto carbon paper as the working electrode (loading 1 mg·cm⁻¹). -2 The test was conducted at room temperature and pressure, using Pt (platinum wire) as the counter electrode, Hg / Hg2O4 as the reference electrode, and 0.5 M H2SO4 as the electrolyte.

[0053] Linear sweep voltammetry was performed on commercial RuO2 (denoted as C-RuO2), H-RuO2 prepared in Comparative Example 1, and V-RuO2 catalyst prepared in Example 1. The results are as follows: Figure 12 As shown in the figure, the V-RuO2 catalyst reaches 10 mA·cm⁻¹. -2 The overpotential required for the current density is only 150 mV, exhibiting excellent oxygen evolution activity. Compared with C-RuO2 and H-RuO2, the electrocatalytic activity of the catalyst is significantly improved after the introduction of V.

[0054] Tafel slope tests were performed on RuO2, H-RuO2, and V-RuO2 catalysts, and the results are as follows: Figure 13 As shown in the figure, the Tafel slope of V-RuO2 is the smallest, indicating that its reaction kinetics are the fastest. This proves that the introduction of V into RuO2 greatly enhances the reaction kinetics of the catalyst.

[0055] Electrochemical impedance spectroscopy was performed on H-RuO2 and V-RuO2 catalysts, and the results are as follows: Figure 14 As shown in the figure, the electrochemical impedance of RuO2 is significantly reduced after the introduction of V.

[0056] Double layer capacitance (C) of RuO2, H-RuO2 and V-RuO2 catalysts dl The test results are as follows: Figure 15 As shown in the figure. It can be seen from the figure that the C after introducing V into RuO2... dl The value increases significantly, indicating an improvement in its electrochemical active area. This suggests that the catalyst with this structure can provide more electrochemical reaction active sites, a conclusion similar to that of HRTEM.

[0057] The specific activities of RuO2, H-RuO2 and V-RuO2 catalysts were tested, and the results are as follows: Figure 16 As shown in the figure, V-RuO2 still exhibits the best catalytic performance after electrochemical active area correction, indicating an improvement in its intrinsic catalytic activity.

[0058] The mass activity of RuO2, H-RuO2 and V-RuO2 catalysts was tested, and the results are as follows: Figure 17 As shown in the figure, V-RuO2 exhibits the best mass activity, indicating that the Ru active sites in this catalyst structure are fully utilized.

[0059] Long-term stability tests were conducted on the V-RuO2 catalyst, and the results are as follows: Figure 18 As shown in the figure, the catalyst performance remained stable after 1000 hours of testing, indicating that the introduction of V improved the structural stability of RuO2 under acidic conditions.

[0060] Cyclic voltammetry tests were performed on H-RuO2 and V-RuO2 catalysts, and the results are as follows: Figure 19 As shown in the figure, the CV curve of H-RuO2 shows a significant Ru content. 8+ / Ru 6+ The oxidation peak was observed in V-RuO2, but not in V-RuO2, indicating that the introduction of V can significantly inhibit the over-oxidation of Ru. Comparison of different V doping levels

[0061] Linear sweep voltammetry was performed on the V-RuO2-1 and V-RuO2-2 catalysts prepared in Examples 2 and 3 to compare different V doping amounts. The testing method was completely consistent with that of commercial RuO2, Example 1, and Comparative Example 1. The results are as follows: Figure 20 As shown in the figure, the results indicate that the V-RuO2-1 and V-RuO2-2 catalysts achieve an 10 mA cm⁻¹ osmosis. -2 The overpotential required for the current density of V-RuO2 is higher than that of V-RuO2, indicating that excessive V doping leads to a decrease in catalyst performance.

[0062] In summary, this invention successfully prepared a high-performance V-doped RuO2 acidic OER electrocatalyst through a simple and efficient liquid-phase reduction-thermal treatment method. This catalyst exhibits significant advantages in both activity and stability, and shows promising prospects for industrialization.

[0063] The scope of protection claimed by this invention is not limited to the specific embodiments described above. Moreover, for those skilled in the art, this invention can have various modifications and alterations. Any modifications, improvements, and equivalent substitutions made within the concept and principles of this invention should be included within the scope of protection of this invention.

Claims

1. A method for preparing a ruthenium-based catalyst for the acidic oxygen evolution reaction, characterized in that, Includes the following steps: S1, take 100-200 parts by mass of RuCl3·H2O and 1-40 parts by mass of VCl3 and dissolve them in 20-60 parts by volume of anhydrous methanol, stir to obtain a mixed solution, wherein the mass parts are expressed in mg and the volume parts are expressed in ml; S2, slowly add 0.1~0.4 volume parts of hydrazine hydrate to the mixed solution prepared in step S1, continue stirring the reaction, and collect the solid by centrifugation and filtration after the reaction is completed; S3, the solid collected in step S2 is washed with anhydrous methanol and ultrapure water alternately, and then freeze-dried to obtain the precursor catalyst; S4. Heat-treat the precursor catalyst prepared in step S3 at 300~500℃ for 1~4h to obtain V-doped RuO2 catalyst.

2. The method for preparing a ruthenium-based catalyst for acidic oxygen evolution reaction according to claim 1, characterized in that, In step S2, the concentration of the hydrazine hydrate is 80 wt%.

3. The method for preparing a ruthenium-based catalyst for acidic oxygen evolution reaction according to claim 1, characterized in that, In step S1, the stirring time is greater than or equal to 0.5 h; in step S2, the stirring time is greater than or equal to 4 h; in step S3, the freeze-drying time is 10 to 20 h; in step S4, the heat treatment is carried out in a muffle furnace with a heating rate of 1 to 5 °C / min.

4. A ruthenium-based catalyst for acidic oxygen evolution reaction prepared by any one of the preparation methods of claims 1 to 3.

5. A ruthenium-based catalyst for the acidic oxygen evolution reaction according to claim 4, characterized in that, The ruthenium-based catalyst has a rutile phase structure.

6. A ruthenium-based catalyst for the acidic oxygen evolution reaction according to claim 5, characterized in that, In the ruthenium-based catalyst, V is uniformly doped in the RuO2 lattice, and the RuO2 lattice fringes are distorted and produce localized highly active sites.

7. The application of the ruthenium-based catalyst according to claim 4 in the acidic oxygen evolution reaction.

8. The application according to claim 7, characterized in that, It is used as an anode electrocatalyst in an acidic water electrolysis oxygen evolution catalyst system.

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