Mn-doped RuTiOx solid solution Mn-RuTiOx / TF acidic oxygen evolution catalyst and preparation method thereof

Abstract

The invention belongs to the technical field of hydrogen production catalysts, and particularly relates to a Mn-doped RuTiOx solid solution acidic oxygen evolution catalyst and a preparation method thereof. The acidic oxygen evolution catalyst provided by the invention comprises a titanium felt substrate and a Mn-doped RuTiOx solid solution active layer loaded on the titanium felt substrate, and a MnO2 titanium felt precursor is obtained by performing anodic electrodeposition on a Mn-containing acidic deposition solution at a constant current and a constant temperature; and then carrying out hydrothermal reaction on the MnO2 titanium felt and soluble Ru salt to realize Ru doping, thereby obtaining a solid product, namely the Mn-RuTiOx / TF acidic oxygen evolution catalyst. According to the catalyst, through the synergistic effect of Mn doping and the nanofiber structure, more catalytic active sites are exposed, the Ru site electronic structure in a RuTiOx solid solution can be effectively regulated and controlled, excessive oxidation of the Ru site electronic structure can be inhibited, and the electro-catalysis OER activity and stability of the Ru-based catalyst are remarkably improved. Experimental results show that the obtained catalyst shows excellent oxygen evolution performance in an acid medium, only needs the overpotential of 184 mV under the current density of 10 mA cm, can stably operate for 1000 h, and has good industrial application.

Description

Technical Field

[0001] This invention belongs to the interdisciplinary field of new energy materials and electrocatalysis technology, specifically relating to a Mn-doped RuTiO₂. x Mn-RuTiO solid solution structure x / TF acidic oxygen evolution catalyst and its preparation method are particularly suitable for the anodic catalytic reaction of proton exchange membrane electrolysis (PEMWE) systems. Background Technology

[0002] As the global energy structure transitions towards carbon neutrality, green hydrogen energy, as a zero-carbon energy carrier, is considered a key solution for deep decarbonization in transportation, industry, and other sectors. Among water electrolysis hydrogen production technologies, proton exchange membrane electrolyzers (PEMWE) have become an ideal technology for grid-connected renewable energy sources (such as wind and solar power) due to their advantages such as high current density, rapid dynamic response, and high-purity hydrogen. However, the oxygen evolution reaction (OER) at the anode of PEMWE faces two major challenges:

[0003] (1) Slow kinetics: The four-electron transfer process (4OH⁻ → O2 + 2H2O + 4e⁻) results in an overpotential loss of up to 300-500 mV, which significantly reduces the energy conversion efficiency (currently, the efficiency of commercial systems is about 65-70%).

[0004] (2) Poor catalyst stability: In acidic (pH=1-2) and high oxidation potential (>1.8 V vs. RHE) environments, non-precious metal catalysts are prone to dissolution and corrosion, while precious metal IrO2 (currently a commercially available catalyst) has excellent stability but insufficient activity (overpotential η). 10 > 300 mV) and its cost accounts for more than 40% of the total cost of the electrolyzer.

[0005] In recent years, Ru-based catalysts have become a research hotspot due to their higher intrinsic activity (TOF value is about 3-5 times that of IrO2) compared to Ir-based materials. However, existing RuO2-based catalysts suffer from an "activity-stability paradox": pure RuO2 is prone to Ru oxidation during the OER process via the lattice oxygen oxidation mechanism (LOM), leading to Ru oxidation. 4 ⁺ Excessive oxidation to soluble Ru 6 ⁺ (forming RuO4), the stability at a current density of 10 mA·cm⁻² is usually <100 h; although single-component doping (such as Ti, Sn) can optimize the activity through electronic effects, it still cannot solve the problems of Ru dissolution and loss of active sites at the same time.

[0006] Therefore, it is necessary to develop products with high activity (η) 10Acidic OER catalysts with < 250 mV, long lifespan (>1000 h@10 mA·cm⁻²), and low Ru content (<50 wt%) are the core requirements for overcoming the commercialization bottleneck of PEMWE technology. Summary of the Invention

[0007] The purpose of this invention is to provide a Mn-doped RuTiO₂ x solid solution Mn-RuTiO x This invention relates to an acidic oxygen evolution catalyst (O2) and its preparation method, aiming to address the problems of poor stability and easy agglomeration of Ru-based catalysts in acidic environments in existing technologies. The invention prepares a nanofiber-structured MnO2 precursor on a titanium felt using electrodeposition, followed by Ru doping and heat treatment via a hydrothermal method to form Mn-RuTiO2. x The solid solution effectively inhibits the excessive oxidation of Ru, thereby improving the stability and activity of the catalyst.

[0008] To achieve the above objectives, the present invention provides a method for preparing a Mn-RuTiOx / TF acidic oxygen evolution catalyst based on a Mn-doped RuTiOx solid solution, comprising the following steps:

[0009] S1. Preparation of MnO2 / TF precursor by electrodeposition. In an acidic deposition solution containing Mn²⁺, anodic electrodeposition was performed using a titanium felt as the working electrode, a platinum sheet as the counter electrode, and a saturated calomel electrode as the reference electrode under constant current and temperature to obtain MnO2 titanium felt (MnO2 / TF).

[0010] S2. Hydrothermal Ru doping. The MnO2 / TF obtained in step S1 is immersed in a mixed solvent containing soluble Ru salt, and then transferred to a hydrothermal reactor for hydrothermal reaction to obtain Ru-doped MnO2 / TF.

[0011] S3. Heat treatment to form a solid solution. The Ru-doped MnO2 / TF obtained in step S2 is transferred to a muffle furnace and heated in air atmosphere. After natural cooling to room temperature, the Mn-RuTiO2 solid solution is obtained. x / TF acidic oxygen evolution catalyst.

[0012] Preferably, in step S1:

[0013] Mn²⁺ is provided by MnSO₄ solution with a concentration of 0.25-0.35 mol·L⁻¹. -1 0.30 mol·L -1 ;

[0014] The acidic solution is an H₂SO₄ solution with a concentration of 0.30-0.42 mol·L⁻¹. -10.36 mol·L⁻¹ is preferred. -1 ;

[0015] • Electrodeposition is performed using a constant current with a current density of 5-10 mA·cm⁻², preferably 7 mA·cm⁻²;

[0016] • The electrodeposition time is 0.5-1.5 h, preferably 1 h;

[0017] • The electrodeposition temperature is 60-100℃, preferably 94℃.

[0018] Preferably, in step S2:

[0019] • The mixed solvent is a mixture of deionized water and ethanol in a volume ratio of 1:1;

[0020] The soluble Ru salt is ruthenium trichloride (RuCl3·xH2O) or ruthenium nitrate (Ru(NO3)3), with a concentration of 0.01-0.05 mol / L, preferably 0.03 mol / L;

[0021] • The hydrothermal temperature is 100-180℃, preferably 150℃;

[0022] • The hydrothermal time is 8-24 hours, preferably 12 hours.

[0023] Preferably, in step S3:

[0024] The heating temperature is 200-500℃, preferably 250℃;

[0025] Heating time is 1-3 hours, preferably 1 hour;

[0026] The heating rate is 2-5℃ / min, preferably 5℃ / min.

[0027] The present invention also provides a Mn-doped RuTiO₂ prepared by the above method. x solid solution Mn-RuTiO x / TF acidic oxygen evolution catalyst, this catalyst has a three-dimensional porous structure, composed of Mn-RuTiO2 nanofibers. x The solid solution is uniformly distributed on the surface of the titanium felt.

[0028] It contains at least the following beneficial technical effects:

[0029] 1. Nanofiber Structure Design: The MnO2 precursor prepared by electrodeposition in this invention possesses a nanofiber structure with a large specific surface area, providing more active sites. During hydrothermal processes, this structure can both perform ion exchange while maintaining its own structural integrity and achieve uniform Mn doping, effectively suppressing RuO2 aggregation.

[0030] 2. Solid solution formation mechanism: Through hydrothermal treatment and heat treatment, Mn, Ru, and Ti elements formed a stable solid solution structure, and Mn successfully entered RuTiO. x In the Ru lattice, the electronic structure of Ru was adjusted, the Ru-O covalent property was weakened, the participation of lattice oxygen was suppressed, and the stability of RuO2 was significantly improved.

[0031] 3. Excellent electrocatalytic performance: The Mn-RuTiO prepared in this invention... x The / TF catalyst exhibits excellent OER performance in 0.5M H2SO4 solution, with an overpotential of only 184mV at a current density of 10mA·cm⁻² and a Tafel slope of 47.73mV·dec⁻¹, which is far superior to commercial RuO2 catalysts.

[0032] 4. Excellent stability: After 1000 h of constant current electrolysis at a current density of 10 mA·cm⁻², the overpotential of the catalyst increased by only 61.5 mV, while the performance of commercial RuO2 catalysts showed significant degradation after 6 h under the same conditions. Attached Figure Description

[0033] Figure 1 This is a scanning electron microscope (SEM) image of the structure of the present invention;

[0034] Figure 2 The structure is shown in the transmission electron microscope (TEM) and elemental distribution diagram of this invention;

[0035] Figure 3 The X-ray diffraction (XRD) pattern of the structure of this invention is shown below.

[0036] Figure 4 The diagram shows the catalytic performance of the structure of the present invention in an acidic oxygen evolution reaction in a three-electrode system, tested using linear voltammetry.

[0037] Figure 5 The structure of the present invention is at 10 mA cm -2 Timing potential curves at current density. Detailed Implementation

[0038] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as a limitation of the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0039] It should be understood that the terminology used in this invention is merely for describing particular embodiments and is not intended to limit the invention. Furthermore, with respect to numerical ranges in this invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Any stated value or intermediate value within a stated range, as well as each smaller range between any other stated value or intermediate value within said range, is also included in this invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0040] Unless otherwise stated, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. While only preferred methods and materials have been described herein, any methods and materials similar or equivalent to those described herein may be used in the implementation or testing of this invention. All references to this specification are incorporated by way of citation to disclose and describe methods and / or materials associated with those references. In the event of any conflict with any incorporated reference, the content of this specification shall prevail.

[0041] Various modifications and variations can be made to the specific embodiments described in this specification without departing from the scope or spirit of the invention, as will be apparent to those skilled in the art. Other embodiments derived from this specification will also be readily apparent to those skilled in the art. This specification and embodiments are merely exemplary.

[0042] The terms “include,” “including,” “have,” “contain,” etc., used in this article are all open-ended terms, meaning that they include but are not limited to.

[0043] It should be noted that any aspects not described in detail in this invention are conventional practices in the field and are not the focus of this invention.

[0044] In the specific embodiments of the present invention, the room temperature and ambient temperature are both 20-30℃.

[0045] The raw materials and reagents used in the specific embodiments of this invention are all commercially available products.

[0046] Example 1

[0047] S1. Electrodeposition preparation of MnO2 / TF (MTF) precursor

[0048] Preparation of electrodeposition solution: Dissolve MnSO4·H2O and H2SO4 in deionized water to obtain a mixed solution containing 0.30 mol / L MnSO4 and 0.36 mol / L H2SO4.

[0049] Pretreatment of titanium felt: The titanium felt (2cm×2cm) was ultrasonically cleaned with acetone, ethanol and deionized water for 15min in sequence, then boiled in 10 wt% oxalic acid solution for 30min to remove the surface oxide layer, and finally rinsed with deionized water and dried.

[0050] Electrodeposition: Using the treated titanium felt as the working electrode, a platinum sheet as the counter electrode, and a saturated calomel electrode as the reference electrode, electrodeposition was performed at a constant current density of 7 mA·cm⁻² for 1 h at a constant temperature of 94 °C. After electrodeposition, the sample was rinsed with deionized water and dried overnight at 60 °C to obtain the MnO₂ titanium felt (MnO₂ / TF) precursor.

[0051] S2. Hydrothermal Ru doping

[0052] Preparation of hydrothermal solution: Weigh 124.2 mg RuCl3·xH2O and dissolve it in 15 mL of ethanol and 15 mL of deionized water to obtain a homogeneous mixed solution.

[0053] Hydrothermal reaction: MnO2 / TF was placed in the above solution and transferred to a 50 mL stainless steel reactor lined with polytetrafluoroethylene. The reaction was carried out at 150 °C for 12 h. After the reaction was completed, the sample was allowed to cool naturally to room temperature, removed, rinsed with deionized water and ethanol, and dried at 60 °C overnight.

[0054] S3. Heat treatment to form a solid solution

[0055] The sample was placed in a muffle furnace and heated to 250°C at a heating rate of 5°C / min, held at that temperature for 1 hour, and then naturally cooled to room temperature to obtain a Mn-RuTiOx / TF acidic oxygen evolution catalyst with Mn-doped RuTiOx solid solution.

[0056] Comparative Example 1

[0057] Preparation of RuTiO by hydrothermal method x / TF catalyst: Weigh 124.2 mg RuCl3·xH2O and dissolve it in 15 mL of ethanol and 15 mL of deionized water to obtain a homogeneous mixed solution. Place the pretreated titanium felt into the above solution and react hydrothermally at 150 °C for 12 h, then dry at 60 °C overnight. Place the sample in a muffle furnace and calcine at 250 °C for 1 h to obtain RuTiO2. x / TF catalyst.

[0058] Comparative Example 2

[0059] The Mn-RuO2 / TF catalyst was prepared by a co-hydrothermal method: 124.2 mg RuCl3·xH2O and 101.2 mg MnSO4·H2O were weighed and dissolved in 15 mL ethanol and 15 mL deionized water to obtain a homogeneous mixed solution. The pretreated titanium felt was placed in the above solution and hydrothermally reacted at 150 °C for 12 h, then dried at 60 °C overnight. The sample was then calcined in a muffle furnace at 250 °C for 1 h to obtain the Mn-RuO2 / TF catalyst.

[0060] Figure 1 Mn-RuTiO x The scanning electron microscope (SEM) image of / TF shows that Mn-RuTiO x / TF has a nanofiber structure.

[0061] Figure 2 Mn-RuTiO x Transmission electron microscopy (TEM) and elemental distribution map of / TF, as shown in the figure: Mn-RuTiO x The presence of uniformly distributed O, Ru, Ti, and Mn elements in the / TF nanofibers further confirms the successful doping of Mn and Ti.

[0062] Figure 3 Mn-RuTiO x X-ray diffraction (XRD) patterns of / TF and MTF. The figures show that after high-temperature heat treatment, Mn-RuTiO₂... x The / TF diffraction peaks of RuO2 showed a high-angle shift compared to the standard card, indicating lattice shrinkage of RuO2 due to the doping of smaller Ti and Mn ions. Compared to MTF, the disappearance of the MnO2 diffraction peaks and the appearance of RuO2 diffraction peaks in Mn-RuTiOx / TF indicated successful cation exchange.

[0063] Figure 4 The figures show the linear sweep voltammetry (LSV) curves for different samples. As can be seen from the figure: Mn-RuTiO₂ x / TF exhibits a lower overpotential than the comparative example and commercial RuO2, demonstrating excellent electrochemical properties.

[0064] Figure 5 Mn-RuTiO x The stability test results for the / TF electrocatalyst show that at 10 mA cm⁻¹... -2 Mn-RuTiO at current density x The / TF catalyst operated stably for 1000 hours, demonstrating stable electrocatalytic hydrogen evolution stability. In contrast, the performance of the commercial RuO2 catalyst showed significant degradation after 6 hours under the same conditions.

[0065] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from its spirit or essential characteristics. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, all variations falling within the meaning and scope of equivalents of the claims are intended to be included within the present invention. No reference numerals in the claims should be construed as limiting the scope of the claims.

Claims

1. A Mn-doped RuTiO x A method for preparing a solid solution-based acidic oxygen evolution catalyst, characterized in that, Includes the following steps: S1. Using titanium felt as a substrate, an MnO2 titanium felt precursor is prepared by anodic electrodeposition under constant current and temperature conditions in an acidic deposition solution containing Mn²⁺; S2. The MnO2 titanium felt precursor is immersed in a mixed solvent containing soluble Ru salt to carry out a hydrothermal reaction to achieve Ru doping; S3. The product after the hydrothermal reaction is transferred to a muffle furnace and heated at 250~550℃ for 1~3 hours to obtain Mn-doped RuTiO₂. x Mn-RuTiO solid solution structure x / TF acidic oxygen evolution catalyst.

2. The preparation method according to claim 1, characterized in that: In S1, the acidic precipitation solution containing Mn²⁺ is composed of MnSO₄ and H₂SO₄, wherein the concentration of MnSO₄ is 0.25~0.35 mol·L⁻¹. -1 The concentration of H2SO4 was 0.30~0.42 mol·L⁻¹. -1 .

3. The preparation method according to claim 1, characterized in that: In S1, the constant current density for anodic electrodeposition is 5~10 mA·cm⁻², the electrodeposition time is 0.5~1.5 hours, and the constant temperature is 60~100℃.

4. The preparation method according to claim 1, characterized in that: In S2, the mixed solvent containing soluble Ru salt is a mixture of deionized water and ethanol in a volume ratio of 1:

1. The soluble Ru salt is at least one of RuCl3·xH2O, K2RuO4, Ru(NO3)3 or (NH4)2RuCl6, and the concentration of Ru element in the mixed solvent is 0.01~0.05mol / L.

5. The preparation method according to claim 1, characterized in that: In S2, the hydrothermal reaction temperature is 100~180℃, and the hydrothermal reaction time is 8~24 hours.

6. The preparation method according to claim 1, characterized in that: In S3, the heating rate of the muffle furnace is 2~5℃ / min, and the heating atmosphere is air.

7. A Mn-doped RuTiO x Solid solution acidic oxygen evolution catalyst, characterized in that: The catalyst is prepared by any one of claims 1 to 6, wherein the catalyst comprises a titanium felt substrate and Mn-doped RuTiO supported thereon. x The solid solution is composed of nanofibers with a diameter of 50-200 nm and a specific surface area of ​​30-60 m² / g.

8. The catalyst according to claim 7, characterized in that: The Mn-doped RuTiO x In the solid solution, the molar ratio of Mn to Ru is 1:5 to 1:20, and the Ti element comes from the in-situ oxidation of the titanium felt substrate.

9. The catalyst according to claim 7, characterized in that: In a 0.5 mol / L H2SO4 electrolyte, when the current density is 10 mA·cm⁻², the oxygen evolution overpotential of the catalyst is 184~224 mV, and it can operate stably for more than 1000 hours.

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