Method for preparing Fe-based hydroxide catalyst by utilizing Ni-based powder doping induced phase change and application of Fe-based hydroxide catalyst

Abstract

The invention relates to a method for preparing a Fe-based hydroxide catalyst through Ni-based powder doping induced phase change and application, and belongs to the technical field of electro-catalysis. The Ni-based doped Fe-based hydroxide catalyst is obtained by inducing a phase change reaction of a Fe (NO3) 3 solution for 4-10 hours at the temperature of 150-250 DEG C by utilizing Ni-based powder. The catalyst has a unique layered structure, and the effective doping of the Ni-based powder can significantly optimize the electronic structure and accelerate charge transfer. The Ni-based powder doped induced phase change Fe-based hydroxide catalyst has the characteristics of controllable cost and microstructure, large specific surface area, good catalytic performance and high stability.

Description

Technical Field

[0001] This invention relates to a method and application for preparing Fe-based hydroxide catalysts by inducing phase transition using Ni-based powder doping, belonging to the field of electrocatalysis technology. Background Technology

[0002] Electrocatalytic water production technology uses electrical energy to break the chemical bonds of water molecules, causing them to recombine and form hydrogen and oxygen. This technology boasts significant advantages such as maturity, ease of operation, and zero pollution. However, the oxygen evolution reaction (OER), as the rate-limiting stage in the entire hydrogen production process, restricts its efficiency. Although iridium / ruthenium-based catalysts exhibit excellent performance in the OER, the scarcity and high cost of these two precious metals make industrial application cost a significant challenge.

[0003] Therefore, the development of efficient and stable non-precious metal oxygen evolution reaction (OER) electrocatalysts is of great significance. Catalyst synthesis methods and doping techniques are crucial for improving catalyst performance. Currently, some researchers have significantly improved the catalytic performance of non-precious metal OER electrocatalysts through doping. Compared to pure samples, doping can adjust the electronic structure of materials, forming new impurity energy levels, reducing the energy required for electron excitation, thereby improving the catalyst's conductivity and accelerating the reaction rate. Although doped water electrolysis catalysts have some applications in water electrolysis, they also have many problems. Inappropriate selection or proportion of doping elements can alter the electronic structure of the catalyst, hindering the water electrolysis reaction and leading to reduced catalyst activity. Typically, doping is an optimization method based on the premise that the phase structure of the matrix material remains unchanged, i.e., the crystal structure of the substance remains unchanged, making it difficult to effectively increase the number of active sites on the material surface. Furthermore, the preparation process of doped water electrolysis catalysts is relatively complex. It is difficult to achieve uniform distribution and precise control of doping elements during preparation, and impurities may be introduced, increasing production costs and extending the production cycle, which is detrimental to large-scale industrial production.

[0004] How to induce phase transitions through efficient doping to change the electronic structure of the catalyst surface, improve its activity, and at the same time simplify the preparation process is an urgent problem to be solved. Summary of the Invention

[0005] To address the problems of unstable phase structure, easy formation of impurity phases, and low activity in existing doped water electrolysis catalysts, this invention provides a method for preparing Fe-based hydroxide catalysts by annealing and doping-induced phase transition using Ni-based powder. This invention uses ferric nitrate and Ni-based powder as raw materials. The Ni-based powder is uniformly dispersed in a ferric nitrate solution, and an annealing sintering process induces a chemical reaction, leading to a phase transition in the Fe(NO3)3 solution, resulting in a Ni-based doped Fe-based hydroxide catalyst. This method reduces the difficulty of catalyst preparation, enables batch production, and significantly improves the electrochemical performance and chemical stability of the prepared Ni-based doped Fe-based hydroxide catalyst.

[0006] A method for preparing Fe-based hydroxide catalysts by inducing phase transition using Ni-based powder doping, the specific steps of which are as follows: (1) Dissolve nickel nitrate in deionized water to obtain a nickel solution, dissolve nickel nitrate and sodium molybdate in deionized water to obtain a Ni-Mo mixed solution, and dissolve NaHB4 in deionized water to obtain a NaHB4 solution; (2) Under ice bath conditions, NaHB4 solution is added dropwise to nickel solution or Ni-Mo mixed solution and reacted for 2-4 hours. Solid-liquid separation is performed, and the solid is dried to obtain NiB powder or NiMoB powder. (3) Dissolve Fe(NO3)3·9H2O in deionized water to obtain Fe(NO3)3 solution, add nickel-based powder to Fe(NO3)3 solution and mix evenly, then place at a temperature of 150~250℃ to induce phase change reaction for 4~10h, dry to obtain Ni-based doped Fe-based hydroxide catalyst; the nickel-based powder is Ni powder, NiB powder or NiMoB powder.

[0007] Preferably, in step (1), the concentration of the nickel solution is 0.1~0.3 g / L; the molar ratio of nickel nitrate to sodium molybdate in the Ni-Mo mixed solution is 1:0.5~1, the concentration of nickel nitrate in the Ni-Mo mixed solution is 0.005~0.015 mol / L, and the concentration of NaHB4 solution is 0.004~0.008 g / mL; the molar ratio of nickel nitrate to NaHB4 in the nickel solution or Ni-Mo mixed solution is 1:5~10.

[0008] Preferably, the dropping rate of the NaHB4 solution in step (2) is 1~2 mL / min.

[0009] Preferably, the concentration of Fe(NO3)3 solution in step (3) is 0.1~0.2 g / mL.

[0010] Preferably, in step (3), the mass ratio of Fe(NO3)3·9H2O to Ni-based powder is 1:0.025~0.035.

[0011] The Fe-based hydroxide catalyst can be used as a catalyst in the electrolysis of water to produce hydrogen.

[0012] This invention utilizes the principle of preparing Fe-based hydroxide catalysts by inducing phase transition through Ni-based powder doping: First, the reducing properties of NaBH4 are used to prepare NiB and NiMoB alloy powders. The alloy powders are then dispersed in a ferric nitrate solution. During heating, the reducing properties of the Ni-based alloy powders are utilized, while NO... 3- It possesses oxidizing properties, and under heating conditions, it accelerates redox reactions. During the heating process, in addition to generating Ni-based ions, a large amount of OH- is also produced. - This leads to an increase in pH, and under heating conditions, it accelerates the reaction of metal ions with OH-. - The combination of elements promotes the formation of Fe-based hydroxide catalysts and achieves effective doping of metal ions and non-metallic element B. Element doping can change the electronic structure of the catalyst, thereby optimizing its conductivity and charge migration ability. It can also introduce defect sites or new active sites, promote the adsorption and desorption of reaction intermediates, and thus improve catalytic efficiency. At the same time, doping can enhance the interaction between the catalyst and the substrate, reduce particle agglomeration or shedding, and can also change the chemical properties of the catalyst surface, improving its mechanical and chemical stability under specific reaction conditions.

[0013] The beneficial effects of this invention are: (1) The present invention uses ferric nitrate as raw material and nickel-based powder as an intermediate to induce phase change to achieve the preparation of Fe-based hydroxide catalyst. The preparation method is simple, the catalyst structure and performance are stable, and batch preparation can be realized. (2) The Ni powder and Ni-based alloy powder in this invention have reducing properties, while nitrate ions have oxidizing properties. Under the combined effects of water ionization protons and heating, the metal powder and nitrate ions undergo redox reaction to produce metal ions and a large number of hydroxide ions, which promotes the successful preparation of Fe-based hydroxide catalysts and effectively improves oxygen evolution performance. (3) The NiB alloy powder of the present invention is co-doped with Ni and B. The synergistic effect of the non-metallic element B doping is beneficial to improving the electrical conductivity of the material, accelerating electron transport, improving the morphology of the material, and increasing the active sites. (4) The NiMoB alloy powder of the present invention is co-doped with Ni, Mo and B, which optimizes the electronic structure, active site distribution and reaction microenvironment of the catalyst. Among them, Mo doping can regulate the electron density of Ni and weaken the effect of H on H. + Excessive adsorption leads to the induction of electron-deficient regions by B, which promotes water dissociation. Co-doping of Ni, Mo, and B forms a synergistic network, while B doping can promote the material's transition to an amorphous state, thereby exposing more edge active sites. Attached Figure Description

[0014] Figure 1 XRD patterns of Fe-based hydroxide catalysts in Examples 1, 2, 3 and Comparative Example 1; Figure 2 This is a ground-resolution SEM image of the Fe-based hydroxide in Example 1; Figure 3 This is a TEM image of the Fe-based hydroxide catalyst in Example 1; Figure 4 This is a ground-resolution SEM image of the Fe-based hydroxide in Example 2; Figure 5 This is a TEM image of the Fe-based hydroxide catalyst in Example 2; Figure 6 This is a ground-resolution SEM image of the Fe-based hydroxide in Example 3; Figure 7 This is a TEM image of the Fe-based hydroxide catalyst in Example 3; Figure 8 The graphs show the polarization curves of the Fe-based hydroxide catalysts in Examples 1, 2, 3 and Comparative Example 7. Detailed Implementation

[0015] The present invention will be further described in detail below with reference to specific embodiments, but the scope of protection of the present invention is not limited to the content described.

[0016] Example: A method for preparing Fe-based hydroxide catalysts by inducing phase transition using Ni-based powder doping, the specific steps of which are as follows: (1) Nickel nitrate is dissolved in deionized water to obtain a nickel solution, nickel nitrate and sodium molybdate are dissolved in deionized water to obtain a Ni-Mo mixed solution, and NaHB4 is dissolved in deionized water to obtain a NaHB4 solution; the concentration of the nickel solution is 0.1~0.3 g / L; the molar ratio of nickel nitrate to sodium molybdate in the Ni-Mo mixed solution is 1:0.5~1, the concentration of nickel nitrate in the Ni-Mo mixed solution is 0.005~0.015 mol / L, and the concentration of NaHB4 solution is 0.004~0.008 g / mL; the molar ratio of nickel nitrate to NaHB4 in the nickel solution or Ni-Mo mixed solution is 1:5~10; (2) Under ice bath conditions, NaHB4 solution is added dropwise to nickel solution or Ni-Mo mixed solution and reacted for 2-4 hours. Solid-liquid separation is performed, and the solid is dried to obtain NiB powder or NiMoB powder. The dropping rate of NaHB4 solution is 1-2 mL / min. (3) Fe(NO3)3·9H2O is dissolved in deionized water to obtain Fe(NO3)3 solution. Nickel-based powder is added to Fe(NO3)3 solution and mixed evenly. Then, the mixture is placed at a temperature of 150~250℃ to induce a phase change reaction for 4~10h. After drying, Ni-based doped Fe-based hydroxide catalyst is obtained. The nickel-based powder is Ni powder, NiB powder or NiMoB powder. The concentration of Fe(NO3)3 solution is 0.1~0.2 g / mL, and the mass ratio of Fe(NO3)3·9H2O to Ni-based powder is 1:0.025~0.035. The specific parameters in Examples 1 to 6 are shown in Table 1 below; Table 1. Process parameters for Examples 1-6 ; A comparative example is set up, and its process parameters are shown in Table 2. Table 2 Process parameters for Comparative Examples 1-7 ; XRD characterization: The XRD pattern of the Ni-based doped Fe-based hydroxide catalyst prepared under the conditions of Example 1 is as follows. Figure 1 The diffraction peaks at 9.8°, 21.9°, 34.8°, 41.7°, and 59.4° are characteristic diffraction peaks of Fe-based hydroxides, indicating that Fe4(OH) 11 Successful preparation of NO3 catalyst; XRD patterns of the catalysts prepared under the conditions of Examples 2 and 3 are shown below. Figure 1 The diffraction peaks at 12°, 25°, and 35° are characteristic diffraction peaks of NiFe-LDH, indicating the successful preparation of NiFe-LDH; the XRD pattern of the sample prepared under the conditions of Comparative Example 7 is as follows. Figure 1 The diffraction peaks at 24.1°, 33.1°, 35.6°, 49.4° and 54° are characteristic diffraction peaks of Fe2O3, indicating that Fe(NO3)3·9H2O decomposes to generate Fe2O3 upon heating without any doping, rather than a hydroxide catalyst. SEM and TEM characterization: SEM and TEM images of the nickel-based doped powder in Example 1 are shown below. Figure 2 and 3 As shown, the sample exhibits an overlapping layered structure with a thickness of approximately 100 nm and a relatively smooth surface; SEM and TEM images of the sample in Example 2 are shown below. Figure 4 and 5 As shown, the samples are stacked in blocks and have no obvious morphological features; the SEM and TEM images of the sample in Example 2 are shown below. Figure 6 and 7 As shown, the samples are stacked in sheet form, with a smooth surface and some debris particles. Electrochemical performance characterization: A 1.0M KOH solution was prepared. A graphite electrode was used as the counter electrode, and an Hg / HgO electrode was used as the reference electrode. The catalytic electrodes obtained in Examples 1-6 and Comparative Examples 1-7 were used as the working electrodes. The electrodes were connected to an electrochemical workstation to test the electrochemical performance of hydrogen evolution. Before the test, the electrodes were activated and the impedance was measured to facilitate subsequent IR compensation. After the test, the reversible hydrogen electrode was calibrated. Taking the catalysts prepared in Examples 1, 2, 3 and Comparative Example 7 as examples, the polarization curves are as follows: Figure 8 As shown; the test results of Examples 1-6 and Comparative Examples 1-7 are shown in Table 3; Table 3 Electrochemical performance of Examples 1-6 and Comparative Examples 1-7 ; The Fe-based hydroxide electrocatalyst prepared in the examples possesses a unique layered, overlapping structure, providing a large specific surface area and significantly improving reaction efficiency. Simultaneously, the doping of Ni with other elements effectively improves the electronic structure of the catalyst. By optimizing the electronic structure, more active sites are exposed on the catalyst surface, accelerating electron transport and accumulation at the interface. In terms of performance indicators, the Tafel slope and 100 mA cm⁻¹... -2 Overpotential is a key parameter for evaluating catalyst performance. The Fe-based hydroxide catalyst in this example demonstrates superior performance in both of these indicators. Its smallest Tafel slope indicates faster reaction kinetics during the catalytic reaction, enabling it to drive the reaction efficiently. Furthermore, it achieves the lowest overpotential value. Compared to other comparative examples and embodiments, the catalyst obtained in this example exhibits significant advantages. The lower overpotential indicates that the catalyst can achieve the catalytic reaction with lower energy consumption, reducing the energy barrier and improving energy utilization efficiency. In contrast, the comparative examples, due to the coarser sample preparation conditions, show significantly higher overpotential and Tafel slopes than the embodiments. This indicates higher energy consumption and underscores the significant advantages of this method. It requires simple equipment, eliminating the need for complex and expensive large-scale instruments, thus reducing preparation costs. The operation process is also easy to master. This simple and easy-to-implement preparation method allows for easy batch production of the catalyst, laying a solid foundation for its large-scale application.

[0017] The specific embodiments of the present invention have been described in detail above. However, the present invention is not limited to the above embodiments. Within the scope of knowledge possessed by those skilled in the art, various changes can be made without departing from the spirit of the present invention.

Claims

1. A method for preparing Fe-based hydroxide catalysts by doping-induced phase transition using a Ni-based powder, characterized in that, The specific steps are as follows: (1) dissolving nickel nitrate in deionized water to obtain a nickel solution, dissolving nickel nitrate and sodium molybdate in deionized water to obtain a Ni-Mo mixed solution, and dissolving NaHB4 in deionized water to obtain a NaHB4 solution; (2) under ice bath conditions, the NaHB4 solution is added dropwise into the nickel solution or the Ni-Mo mixed solution and reacts for 2-4 hours, solid-liquid separation is performed, and the solid is dried to obtain a NiB powder or a NiMoB powder; (3) Fe(NO3)3·9H2O is dissolved in deionized water to obtain a Fe(NO3)3 solution, the nickel-based powder is added into the Fe(NO3)3 solution and mixed uniformly, and then phase transition reaction is induced at a temperature of 150-250°C for 4-10 hours, and drying is performed to obtain a Ni-based doped Fe-based hydroxide catalyst; the nickel-based powder is a Ni powder, a NiB powder or a NiMoB powder.

2. The method for preparing Fe-based hydroxide catalyst by doping-induced phase transition using Ni-based powder according to claim 1, characterized in that: In step (1), the concentration of the nickel solution is 0.1-0.3 g / L; the molar ratio of nickel nitrate to sodium molybdate in the Ni-Mo mixed solution is 1:0.5-1, the concentration of nickel nitrate in the Ni-Mo mixed solution is 0.005-0.015 mol / L, and the concentration of the NaHB4 solution is 0.004-0.008 g / mL; the molar ratio of nickel nitrate to NaHB4 in the nickel solution or the Ni-Mo mixed solution is 1:5-10.

3. The method for preparing Fe-based hydroxide catalyst by doping-induced phase transition using Ni-based powder according to claim 1, characterized in that: In step (2), the dropping speed of the NaHB4 solution is 1-2 mL / min.

4. The method for preparing Fe-based hydroxide catalyst by doping-induced phase transition using Ni-based powder according to claim 1, characterized in that: In step (3), the concentration of the Fe(NO3)3 solution is 0.1-0.2 g / mL.

5. The method for preparing Fe-based hydroxide catalyst by doping-induced phase transition according to claim 4, characterized in that: In step (3), the mass ratio of Fe(NO3)3·9H2O to the nickel-based powder is 1:0.025-0.

035.

6. Application of the Fe-based hydroxide catalyst prepared by the method of any one of claims 1-5 in electrolytic water hydrogen production.

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