Preparation of iron-doped trimanganese tetraoxide electrocatalyst and application thereof in alkaline oxygen evolution reaction

Abstract

The application relates to the technical field of electrocatalytic materials, in particular to a preparation method of an iron-doped trimanganese tetraoxide electrocatalyst and application of the iron-doped trimanganese tetraoxide electrocatalyst in an alkaline oxygen evolution reaction. The preparation method of the iron-doped trimanganese tetraoxide electrocatalyst comprises the following steps: (1) ultrasonic cleaning of a conductive substrate in acetone and ethanol solutions for 30 minutes respectively, and then drying the conductive substrate by blowing nitrogen; (2) preparing a precursor solution containing Fe3 + and Mn2 + , and then electrochemically depositing the cleaned conductive substrate in the precursor solution to obtain a precursor of a FeMn layered double hydroxide layer deposited on the surface of the substrate, namely a FeMnLDH precursor; and (3) annealing the deposited sample in air, and then cooling the sample to room temperature to obtain a spinel-structured FeMn3O4@1.

Description

Technical Field

[0001] This invention relates to the field of electrocatalytic materials technology, specifically to the preparation of an iron-doped manganese tetroxide electrocatalyst and its application in alkaline oxygen evolution reaction. Background Technology

[0002] With the increasing global energy demand and the growing severity of environmental problems, water electrolysis for hydrogen production has attracted much attention as a clean energy technology. However, the slow kinetics of the anodic oxygen evolution reaction severely restricts the efficiency of water electrolysis. Currently, commercial catalysts mainly rely on precious metal materials (such as IrO2 and RuO2), which are costly and scarce, limiting their large-scale application. Therefore, the development of efficient, stable, and low-cost transition metal-based OER catalysts is of great significance. For example, the article "Noble metal-free electrocatalytic materials for water splitting in alkaline electrolyte[J]. EnergyChem, 2021, 3(2): 100053." discusses the research significance and progress of non-precious metal catalysts for alkaline oxygen evolution reaction. Manganese oxides (such as Mn3O4) have received widespread attention due to their low cost, environmental friendliness, and tunable structure, but their intrinsic conductivity and catalytic activity still need to be improved. Transition metal doping is one of the effective strategies for regulating electronic structure and increasing active sites. Summary of the Invention

[0003] This invention aims to provide an iron-doped manganese tetroxide (Fe) Mn3O4 spinel nanostructure electrocatalysts are simple to prepare, low in cost, and exhibit excellent OER activity and stability under alkaline conditions.

[0004] To address the problems of the prior art, this application provides a method for preparing an iron-doped manganese tetroxide electrocatalyst and its application in the alkaline oxygen evolution reaction. This method is achieved through the following approach: A method for preparing an iron-doped manganese tetroxide electrocatalyst, comprising the following steps: (1) ultrasonically cleaning a conductive substrate in acetone solution and ethanol solution for 30 minutes each, and then drying it with nitrogen gas for later use; (2) preparing a catalyst containing Fe³⁺. + and Mn² + The precursor solution was used to electrochemically deposit Fe on the substrate surface after cleaning. The precursor of Mn layered double hydroxides, namely Fe MnLDH precursor; (3) The deposited sample was annealed in air and then cooled to room temperature to obtain Fe with spinel structure. Mn3O4@1.

[0005] Fe The MnLDH precursor has a nanosheet structure; iron is uniformly distributed in manganese tetroxide, forming a solid solution, with a relatively low iron content. @1 refers to the Fe³⁺... + With Mn² + Naming of samples with a molar concentration ratio of 1:5.

[0006] Furthermore, the conductive substrate is one or more of carbon cloth, nickel foam, and titanium mesh; in step (2), Fe³ + With Mn² + The molar concentration ratio is 1:1 to 1:10; Mn² + The concentration was 0.05 M, the electrochemical deposition temperature was 23 °C, and the time was 10 min.

[0007] Furthermore, in step (1), the acetone solution has a mass concentration of 75%, and the ethanol solution has a mass concentration of 75%; in step (2), Fe³⁺… + With Mn² + The molar concentration ratio is 1:5.

[0008] Furthermore, in step (2), Fe³ + From ferric nitrate nonahydrate, Mn² + The electrode is derived from manganese nitrate tetrahydrate; the electrochemically deposited electrode is a platinum wire, the reference electrode is Hg / HgO, and the conductive substrate is the working electrode.

[0009] Furthermore, the electrochemical deposition employs a constant current mode with a current density of 80 mA / cm². - ².

[0010] Furthermore, the annealing temperature in step (3) is 300°C. 400℃, for 1 hour 3 hours.

[0011] Furthermore, the annealing process involves a heating rate of 10°C / min and a holding time of 2 hours.

[0012] The iron-doped manganese tetroxide electrocatalyst prepared by the above method is supported by a conductive substrate.

[0013] Application of iron-doped manganese tetroxide electrocatalyst in alkaline oxygen evolution reaction.

[0014] An electrolytic water hydrogen production system, wherein the anode of the electrolytic water hydrogen production system is made of Fe. Mn3O4@1.

[0015] Beneficial effects (1) High catalytic activity and low energy consumption: The Fe-Mn3O4 anode catalyst used in this patent significantly improves the intrinsic electrocatalytic activity of manganese tetroxide through iron doping, effectively reducing the overpotential of oxygen evolution reaction (OER), thereby improving the overall energy efficiency of the water electrolysis system and reducing hydrogen production energy consumption.

[0016] (2) Excellent structural stability and long lifespan: The catalyst is grown in situ on a conductive substrate, combining the stabilizing effect of Fe doping on the crystal structure with the mechanical strength of the nanosheet structure. It can operate stably for a long time in high current density and strong alkaline environment, which greatly extends the service life of the anode material.

[0017] (3) Low cost and resource-friendly: Using abundant iron and manganese as active components, the use of precious metals (such as Ir and Ru) is completely avoided, and the cost of raw materials is significantly reduced; moreover, the preparation process is simple and the conditions are mild, making it easy to scale up production, which is conducive to promoting the large-scale application of water electrolysis hydrogen production technology.

[0018] Purpose of cleaning: To remove contaminants such as grease, dust, and oxides from the surface of the conductive substrate, ensuring that the catalyst can adhere uniformly to the substrate and improving the catalyst's performance and stability. First, acetone is used for cleaning to remove organic contaminants and grease; then ethanol is used to clean to remove polar contaminants, and ethanol's volatility also helps remove acetone residue.

[0019] Nitrogen drying is used to quickly and gently remove solvents, avoiding contamination or oxidation that may be introduced by using hot air or natural drying. Nitrogen is an inert gas that prevents the substrate from reacting with oxygen or water vapor in the air during the drying process, especially for sensitive conductive materials. Furthermore, nitrogen drying avoids water stains or solvent residue, ensuring a clean and dry substrate surface. Attached Figure Description

[0020] To more clearly illustrate the technical solutions in the embodiments of this application, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some preferred embodiments of this application, and not all embodiments. For those skilled in the art, other embodiments and drawings can be obtained based on these embodiments and drawings without creative effort, and all of them fall within the protection scope of this application.

[0021] Figure 1 This is a schematic diagram of the preparation process and a schematic diagram of the XRD and FTIR characterization results of this invention; Figure 2 Mn3O4 and Fe Elemental distribution maps of Mn3O4@1 obtained by SEM, TEM, HRTEM and EDS; Figure 3 The full XPS spectrum and high-resolution spectra of Mn 2p, O 1s, and Fe 2p are shown. Figure 4 OER performance test results: LSV curve, Tafel slope, electrochemical impedance spectroscopy, double layer capacitance, and ECSA normalized LSV curve. Figure 5 For stability testing and XRD patterns after stability testing; Figure 6 XPS spectra of O 1s and Fe 2p after stability testing; Detailed Implementation To make the objectives, technical solutions, and advantages of this application clearer, the embodiments of this application will be described in further detail below. It should be understood that the terms "upper," "lower," "top," "bottom," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. The foregoing definitions are only for the convenience of describing this application and simplifying the description, and are not intended to indicate or imply that the structure referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this application.

[0022] Example 1 Fe Preparation of Mn3O4@1 electrocatalyst The preparation steps are as follows: (1) The carbon cloth is ultrasonically cleaned in 75% acetone solution and 75% ethanol solution for 30 minutes each, and then dried with nitrogen gas for later use; (2) 200 mg of ferric nitrate nonahydrate and 630 mg of manganese nitrate tetrahydrate are dissolved in 50 mL of deionized water and stirred to prepare a homogeneous precursor solution (Fe³⁺). + / Mn² + (Molar ratio 1:5); the cleaned carbon was arranged in the precursor solution for electrochemical deposition, with carbon cloth as the working electrode, at 80 mA / cm². - Electrodeposition at a current density for 10 minutes yielded Fe deposited on the substrate surface. The precursor of Mn layered double hydroxides, namely Fe MnLDH precursor; (3) The deposited sample was annealed in air at 10℃ / min to 350℃ and held for 2 hours, and then cooled to room temperature to obtain Fe with spinel structure. Mn3O4@1.

[0023] The electrochemical deposition was performed in a constant current mode at a temperature of 23°C. The electrochemically deposited electrode is a platinum wire, and the reference electrode is Hg / HgO.

[0024] X-ray diffraction analysis: The XRD pattern of Fe-Mn3O4@1 is consistent with the structure of standard Mn3O4 spinel, with the main diffraction peaks corresponding to the (103), (211), and (220) crystal planes. Fe doping leads to a decrease in the intensity of the diffraction peaks, indicating that Fe has been successfully incorporated into the Mn3O4 lattice to form a solid solution, causing lattice distortion and grain refinement.

[0025] Infrared spectroscopy analysis: 620 cm⁻¹ in FTIR spectrum - The peak at position ¹ represents the O-Mn asymmetric stretching vibration. The intensity of this peak increases with increasing Fe content to a 1:5 ratio, indicating that Fe³⁺… + The introduction of this enhances the synergistic effect of the Fe-O-Mn bond. ~3400cm - The enhanced OH stretching vibration peak at position ¹ indicates an increase in oxygen vacancy concentration.

[0026] Scanning electron microscopy analysis: SEM showed that Fe-Mn3O4@1 is composed of nanoparticles with a size of 15-30 nm. The surface is rough and smaller than that of undoped Mn3O4 particles, which is beneficial for exposing more active sites.

[0027] Transmission electron microscopy analysis: TEM further confirmed the reduction in particle size. High-resolution TEM showed that the (103) interplanar spacing of Fe-Mn3O4@1 was reduced by 0.01 nm compared to the undoped sample, indicating that Fe³ + Doping causes lattice shrinkage and strain. EDS surface scan shows that Fe, Mn, and O elements are uniformly distributed, with no Fe clusters or second phase formation.

[0028] X-ray photoelectron spectroscopy analysis: XPS indicates that Fe mainly exists as Fe³⁺. + The form exists at octahedral sites, Mn³ + The binding energy increases with Fe doping, indicating that the strong electronegativity of the Fe-O bond leads to a decrease in the electron density around Mn. The significantly enhanced oxygen vacancy peak intensity in the O 1s spectrum confirms that Fe doping introduces more oxygen vacancies.

[0029] OER performance test: A standard three-electrode electrochemical cell system was employed, using a Hg / HgO electrode as the reference electrode, a platinum wire as the counter electrode, and the working electrode fabricated by directly growing the material onto a carbon cloth substrate with a geometric area of ​​1 cm². Electrochemical tests were conducted at room temperature in a 1.0 MkOH solution. Fe Mn3O4@1 at 10 mA cm - The overpotential at 2 is 306 mV, and the Tafel slope is 68 mV dec. - ¹, The charge transfer resistance is 0.52 Ω, and the double-layer capacitance is 20 mF cm⁻¹. - ², exhibiting superior catalytic activity compared to IrO2 and undoped Mn3O4.

[0030] Stability test: At 10 mA cm - ²After running continuously for 24 hours under constant current conditions, Fe The Mn3O4@1 catalyst maintains a stable structure and retains over 95% of its activity, indicating excellent long-term operational stability.

[0031] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application and are not intended to limit it. Although this application has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of this application without departing from the spirit and scope of the technical solutions of this application, and all such modifications or substitutions should be covered within the scope of the claims of this application.

Claims

1. A method for preparing an iron-doped manganese tetroxide electrocatalyst, characterized in that, The preparation steps are as follows: (1) The conductive substrate is ultrasonically cleaned in acetone solution and ethanol solution for 30 minutes each, and then dried with nitrogen gas for later use; (2) Prepare a solution containing Fe³ + and Mn² + The precursor solution was used to electrochemically deposit Fe on the substrate surface after cleaning. The precursor of Mn layered double hydroxides, namely Fe MnLDH precursor; (3) The deposited sample was annealed in air and then cooled to room temperature to obtain Fe with spinel structure. Mn3O4@1.

2. The preparation method of the iron-doped manganese tetroxide electrocatalyst as described in claim 1, characterized in that, The conductive substrate is one or more of carbon cloth, nickel foam, and titanium mesh; in step (2), Fe³ + With Mn² + The molar concentration ratio is 1:1 to 1:10; Mn² + The concentration was 0.05 M, the electrochemical deposition temperature was 23 °C, and the time was 10 min.

3. The method for preparing an iron-doped manganese tetroxide electrocatalyst as described in claim 1, characterized in that, In step (1), the acetone solution has a mass concentration of 75%, and the ethanol solution has a mass concentration of 75%; in step (2), Fe³ + With Mn² + The molar concentration ratio is 1:

5.

4. The method for preparing an iron-doped manganese tetroxide electrocatalyst as described in claim 1, characterized in that, In step (2), Fe³ + From ferric nitrate nonahydrate, Mn² + It comes from manganese nitrate tetrahydrate.

5. The method for preparing an iron-doped manganese tetroxide electrocatalyst as described in claim 1, characterized in that, The electrochemical deposition was performed in a constant current mode with a current density of 80 mA / cm². - ²; The electrochemically deposited electrode is a platinum wire, the reference electrode is Hg / HgO, and the conductive substrate is the working electrode.

6. The method for preparing an iron-doped manganese tetroxide electrocatalyst as described in claim 1, characterized in that, The annealing temperature in step (3) is 300°C. 400℃, for 1 hour 3 hours.

7. The method for preparing an iron-doped manganese tetroxide electrocatalyst as described in claim 6, characterized in that, The annealing process involves a heating rate of 10°C / min and a holding time of 2 hours.

8. The iron-doped manganese tetroxide electrocatalyst prepared by the method according to any one of claims 1-7, characterized in that, The electrocatalyst is supported by a conductive substrate.

9. The application of the iron-doped manganese tetroxide electrocatalyst as described in claim 8 in the alkaline oxygen evolution reaction.

10. A water electrolysis hydrogen production system, characterized in that, The anode of the water electrolysis hydrogen production system uses Fe Mn3O4@1.

Images