NiMoO4@NiFe(OH) x Hierarchical catalysts, their preparation methods and applications

Abstract

This invention provides a NiMoO4@NiFe(OH) x A hierarchical catalyst, its preparation method, and its application are disclosed. The preparation of the catalyst includes the following steps: removing oil and oxide layers from the surface of nickel foam; dissolving nickel nitrate and ammonium molybdate in deionized water and placing them together with the nickel foam in a high-pressure reactor for hydrothermal reaction to grow NiMoO4 in situ on the nickel foam substrate; after the reaction, cleaning and drying are performed to obtain nickel foam loaded with NiMoO4; immersing it in an iron salt solution to obtain nickel foam loaded with Fe-NiMoO4; immersing it in an alkaline solution, cleaning, and drying are performed to obtain NiMoO4@NiFe(OH). x Hierarchical catalyst. The preparation method of this invention is simple and safe, and can be mass-produced. The prepared catalyst has a three-dimensional hierarchical structure and exhibits excellent catalytic performance and stability in a three-electrode system and an AEMWE electrolyzer.

Description

Technical Field

[0001] This invention relates to water electrolysis catalyst technology, and more particularly to a NiMoO4@NiFe(OH) catalyst. x Hierarchical catalysts, their preparation methods and applications. Background Technology

[0002] Recently, water electrolysis technology utilizing renewable energy has attracted global attention due to its ability to achieve sustainable and efficient hydrogen (H2) production. However, the commercialization of this technology is severely hampered by the slow kinetics of the oxygen evolution reaction (OER), stemming from its inherent four-electron transfer pathway. Although noble metal-based catalysts (such as IrO2 and RuO2) exhibit high activity for OER, their scarcity and high cost hinder large-scale industrial applications. Therefore, the development of inexpensive, high-performance, and scalable non-noble metal OER electrocatalysts is essential.

[0003] Nickel molybdate (NiMoO4) has a large specific surface area, a simple synthesis method, and is easy to reconstruct, making it a potential catalyst for water electrolysis. However, its poor electrical conductivity and limited number of reaction centers restrict its application. Constructing heterogeneous interfaces is considered a feasible strategy for optimizing electronic structure and enhancing the intrinsic activity of electrocatalysts. The interface between two different materials alters electron transfer and chemical properties, thereby improving the electrochemical performance of the electrode.

[0004] For example, Liu Chaoyang's research on the synthesis, modification, and electrocatalytic oxygen evolution performance of nickel molybdate-based nanomaterials describes a method for preparing a NiMoO4-based composite catalyst. The main steps are as follows: Preparation of NiMoO4•nH2O / NF: After pretreating nickel foam, NiMoO4•nH2O is grown in situ via a hydrothermal reaction (120℃, 5h). NiMoO4@FeNi(OH) x Preparation of -X (different Fe ratios): The above-mentioned NiMoO4 was dispersed with FeCl3 in different molar ratios, then NaBH4 solution was added, and the mixture was reacted again via hydrothermal reaction (120℃, 5h) to obtain products with different Fe doping ratios. NiMoO4@FeNi(OH) xThe preparation of -Y (different B ratios) involves dispersing NiMoO4 and FeCl3 in a fixed ratio, then adding NaBH4 solutions of different concentrations, and reacting them through the same hydrothermal reaction (120℃, 5h) to obtain products with different B ratios. The main disadvantages of this technique are: 1. This experimental method requires two hydrothermal steps, making the operation complex and time-consuming; 2. This experiment uses NaBH4 (sodium borohydride) reagent, which is a potentially explosive hazardous chemical that releases flammable gas (hydrogen) upon contact with water, easily causing combustion or even explosion, posing a certain risk during catalyst scale-up; 3. The high price of NaBH4 (sodium borohydride) reagent increases the cost of catalyst preparation. Summary of the Invention

[0005] The purpose of this invention is to address the problems of complex, time-consuming, and costly preparation processes of existing water electrolysis oxygen evolution catalysts, which require the use of highly explosive and hazardous chemicals. To address these issues, this invention proposes a NiMoO4@NiFe(OH) catalyst. x A method for preparing hierarchical catalysts is presented. This method is simple, safe, and can be scaled up for large-scale production. The resulting NiMoO4@NiFe(OH) catalyst is described. x The hierarchical catalyst has a three-dimensional hierarchical structure and exhibits excellent catalytic performance and stability in the three-electrode system and AEMWE electrolyzer.

[0006] It should be noted that, in this invention, unless otherwise specified, the specific meaning of "comprising" in relation to composition and description includes both open-ended meanings such as "comprising," "including," etc., and closed-ended meanings such as "composed of," "consisting of," etc., and similar meanings.

[0007] To achieve the above objectives, the technical solution adopted by the present invention is: a NiMoO4@NiFe(OH) compound. x A method for preparing a hierarchical catalyst includes the following steps:

[0008] Step 1. Pretreatment: Immerse the nickel foam in anhydrous ethanol, dilute hydrochloric acid and deionized water in sequence for ultrasonic cleaning to remove surface oil and oxide layer;

[0009] Step 2. Hydrothermal preparation of NiMoO4: Nickel nitrate and ammonium molybdate are dissolved in deionized water and stirred evenly. Then, they are placed together with the pretreated nickel foam from Step 1 in a high-pressure reactor for hydrothermal reaction to grow NiMoO4 in situ on the nickel foam substrate. After the reaction is completed, the substrate is cleaned and dried to obtain nickel foam loaded with NiMoO4.

[0010] Step 3. Iron salt impregnation: Iron salt is dissolved in deionized water to form an iron salt solution. The nickel foam loaded with NiMoO4 obtained in Step 2 is impregnated in the iron salt solution to obtain nickel foam loaded with Fe-NiMoO4.

[0011] Step 4. Alkali impregnation conversion: KOH is dissolved in deionized water to form an alkaline solution. The Fe-NiMoO4-loaded nickel foam obtained in Step 3 is impregnated in the alkaline solution. After washing and drying, NiMoO4@NiFe(OH) is obtained. x Hierarchical catalyst, where x = 1.5-3.

[0012] Furthermore, in step 1, the concentration of the dilute hydrochloric acid is 1-3 mol / L.

[0013] Furthermore, in step 1, the ultrasonic cleaning time is 10-20 minutes.

[0014] Furthermore, in step 2, the concentration of nickel nitrate is 30-50 mmol / L.

[0015] Furthermore, in step 2, the concentration of the ammonium molybdate is 5-20 mmol / L.

[0016] Furthermore, in step 2, the hydrothermal reaction temperature is 120-160℃, and the reaction time is 4-10 hours.

[0017] Further, in step 2, the mass ratio of the foamed nickel to nickel nitrate and ammonium molybdate is 0.2~4g:0.3~12g:0.3~15g.

[0018] Further, after the hydrothermal reaction in step 2 is completed, the sample is cooled to room temperature, washed multiple times with deionized water, and dried in an electric heating oven at 50~80℃ to obtain nickel foam loaded with NiMoO4.

[0019] Furthermore, in step 3, the iron salt is one or more of ferrous sulfate, ferric nitrate, and ferric chloride.

[0020] Furthermore, in step 3, the iron ion concentration in the iron salt solution is 0.05-0.6 mol / L.

[0021] Furthermore, in step 3, the immersion temperature is 20~50℃ and the immersion time is 10-500 s.

[0022] Furthermore, in step 3, the mass ratio of the nickel foam loaded with NiMoO4 to the iron salt is 0.5~9:1.2~15.

[0023] Furthermore, in step 4, the concentration of the KOH solution is 4~6.5 mol / L.

[0024] Further, in step 4, the mass ratio of the Fe-NiMoO4-loaded nickel foam to potassium hydroxide is 0.5~10:15~70.

[0025] Furthermore, in step 4, the immersion temperature is 20~50℃ and the immersion time is 0.5-8 h.

[0026] Further, in step 4, after impregnation, the catalyst is washed multiple times with deionized water and dried in an electrically heated oven at 50-80°C to obtain NiMoO4@NiFe(OH). x Hierarchical catalysts.

[0027] Another object of the present invention discloses a NiMoO4@NiFe(OH) x The hierarchical catalyst was prepared by the above method, wherein x = 1.5-3.

[0028] Furthermore, the NiMoO4@NiFe(OH) x The hierarchical catalyst uses nickel foam as a substrate, on which NiMoO4 microrod structures are grown, and the surface of the NiMoO4 microrod structures is in situ coated with NiFe(OH). x Nanosheets form core-shell complexes with hierarchical heterogeneous structures.

[0029] Furthermore, the NiMoO4 microrods are grown in situ on the nickel foam substrate via a hydrothermal reaction, and the NiFe(OH)... x Nanosheets are uniformly coated onto the surface of the NiMoO4 microrod using an impregnation method.

[0030] Another object of the present invention discloses a NiMoO4@NiFe(OH) x Application of hierarchical catalysts in the field of oxygen evolution through water electrolysis.

[0031] Furthermore, the NiMoO4@NiFe(OH) x Application of hierarchical catalysts as anodes in alkaline anion exchange membrane water electrolyzers.

[0032] This invention relates to NiMoO4@NiFe(OH) x Hierarchical catalysts, their preparation methods, and applications have the following advantages compared to existing technologies:

[0033] 1) The anode catalyst NiMoO4@NiFe(OH) provided by this invention xIt possesses a hierarchical heterogeneous structure, with nanosheets encapsulating microrod structures to form a multi-level structure. This facilitates the exposure of more active sites, promotes mass transfer and charge transport, and accelerates the desorption and overflow of product bubbles. NiMoO4@NiFe(OH) x (x=1.5-3) at a current density of 100 mA cm⁻¹ -2 The prepared catalyst exhibited a low oxygen evolution overpotential of only 327 mV and was able to operate stably for 25 hours at this current density. It was used as the anode in an anion exchange membrane water electrolyzer (AEMWE) at 20% KOH and 0.8 A cm⁻¹. -2 It can operate stably for 100 hours at 60℃, demonstrating excellent stability.

[0034] 2) The present invention NiMoO4@NiFe(OH) x The preparation process of the hierarchical catalyst is simple: it adopts a "one-step hydrothermal + two-step impregnation" preparation process, which is simpler to operate and less time-consuming than the two-step hydrothermal reaction of the existing technology.

[0035] 3) The present invention NiMoO4@NiFe(OH) x The preparation of hierarchical catalysts avoids the use of high-risk, easily explosive hazardous chemicals (such as NaBH4), and mainly uses nickel nitrate, ammonium molybdate, ferrous sulfate and KOH as raw materials, which effectively reduces production risks.

[0036] 4) The equipment of this invention is simple and low in cost: the core equipment is mainly a conventional drying oven, without the need for complex or special high-pressure equipment, which is suitable for large-scale production and reduces equipment and raw material costs.

[0037] This invention relates to NiMoO4@NiFe(OH) x Hierarchical catalysts have promising application prospects and large-scale promotion potential in the field of oxygen evolution through water electrolysis. Attached Figure Description

[0038] Figure 1 The NiMoO4@NiFe(OH) prepared in Examples 1 and 2 of this invention. x A picture of the actual product;

[0039] Figure 2 The NiMoO4@NiFe(OH) prepared in Example 1 of this invention x Microscopic image magnified 150 times;

[0040] Figure 3 The NiMoO4@NiFe(OH) prepared in Example 1 of this invention x Figure showing the oxygen evolution performance test results of the catalyst and the comparative catalyst;

[0041] Figure 4 The NiMoO4@NiFe(OH) prepared in Example 1 of this invention x Stability test diagram of oxygen evolution reaction;

[0042] Figure 5 The NiMoO4@NiFe(OH) prepared in Example 2 of this invention x This is a test chart of the anode stability of the AEMWE electrolyzer. Detailed Implementation

[0043] The present invention will be further described below with reference to embodiments. The description of the technical features described below is based on representative embodiments and specific examples of the present invention, but the present invention is not limited to these embodiments and specific examples. It should be noted that:

[0044] Unless otherwise stated, all units used in this specification are international standard units, and all numerical values ​​and ranges appearing in this invention should be understood to include systematic errors that are unavoidable in industrial production.

[0045] In this specification, the range of values ​​referred to as "value A to value B" refers to the range including the endpoint values ​​A and B.

[0046] In this specification, the numerical range indicated by "above" or "below" refers to the numerical range that includes the stated number.

[0047] In this specification, the word "may" has two meanings: to perform a certain process and not to perform a certain process.

[0048] In this specification, the terms "optional" or "optional" are used to indicate the use or omission of certain substances, components, procedures, application conditions, etc.

[0049] In this instruction manual, when "room temperature" or "room temperature" is used, the temperature can be 15-25℃.

[0050] Unless otherwise specified, all reagents or instruments used in this instruction manual are commercially available products.

[0051] Example 1

[0052] This embodiment discloses a NiMoO4@NiFe(OH) method. x The hierarchical catalyst is prepared as follows:

[0053] Step (1): Place nickel foam (2*3.5 cm) 2The sample was sequentially immersed in anhydrous ethanol, 3 mol / L dilute hydrochloric acid, and deionized water for ultrasonic cleaning for 10 min to remove surface oil and oxide layer, and then dried in a vacuum drying oven at 50℃.

[0054] Step (2): Dissolve 0.3489 g of nickel nitrate and 0.3708 g of ammonium molybdate in 30 mL of deionized water and stir until homogeneous. The concentration of nickel nitrate in the solution is 40 mmol / L, and the concentration of ammonium molybdate is 10 mmol / L. Transfer the solution to a 50 mL high-pressure reactor and place the dried nickel foam inside. The hydrothermal reaction temperature is 150℃, and the reaction time is 6 h. After the reaction is completed, cool to room temperature, wash the sample several times with deionized water, and dry it in a 60℃ electric heating oven to obtain a yellow NiMoO4 catalyst.

[0055] Step (3): Add 1.3902 g of ferrous sulfate to 50 mL of deionized water and stir until homogeneous. The concentration of ferrous sulfate in the solution is 0.1 mol / L. Impregnate the NiMoO4 catalyst obtained in step (2) in this solution at a temperature of 25°C for 60 s to obtain the Fe-NiMoO4 catalyst.

[0056] Step (4): Dissolve 16.833 g of KOH in 50 mL of deionized water and stir until homogeneous. The KOH concentration in the solution is 6 mol / L. Impregnate the Fe-NiMoO4 catalyst obtained in step (3) in an alkaline solution at 25 °C for 1.0 h. After impregnation, wash several times with deionized water and dry in a 60 °C electric heating oven to obtain yellow-green NiMoO4@NiFe(OH). x Hierarchical catalysts.

[0057] Example 2

[0058] This embodiment discloses a NiMoO4@NiFe(OH) method. x The hierarchical catalyst is prepared as follows:

[0059] Step (1): Place nickel foam (10*10 cm) 2 The sample was sequentially immersed in anhydrous ethanol, 3 mol / L dilute hydrochloric acid, and deionized water for ultrasonic cleaning for 10 min to remove surface oil and oxide layer, and then dried in a vacuum drying oven at 50℃.

[0060] Step (2): Dissolve 11.63 g of nickel nitrate and 12.36 g of ammonium molybdate in 1 L of deionized water and stir until homogeneous. The concentration of nickel nitrate in the solution is 40 mmol / L, and the concentration of ammonium molybdate is 10 mmol / L. Transfer the solution to a 1.5 L high-pressure reactor and place the dried nickel foam inside. The hydrothermal reaction temperature is 150℃, and the reaction time is 6 h. After the reaction is completed, cool to room temperature, wash the sample several times with deionized water, and dry it in a 60℃ electric heating oven to obtain a yellow NiMoO4 catalyst.

[0061] Step (3): Add 13.902 g of ferrous sulfate to 500 mL of deionized water and stir until homogeneous. The concentration of ferrous sulfate in the solution is 0.1 mol / L. Impregnate the NiMoO4 catalyst obtained in step (2) in this solution at a temperature of 25°C for 60 s to obtain the Fe-NiMoO4 catalyst.

[0062] Step (4): Dissolve 67.332 g of KOH in 200 mL of deionized water and stir until homogeneous. The KOH concentration in the solution is 6 mol / L. Impregnate the Fe-NiMoO4 catalyst obtained in step (3) in an alkaline solution at 25℃ for 1.0 h. After impregnation, wash several times with deionized water and dry in a 60℃ electric heating oven to finally obtain yellow-green NiMoO4@NiFe(OH). x Hierarchical catalysts.

[0063] Example 3

[0064] This embodiment discloses a NiMoO4@NiFe(OH) method. x The hierarchical catalyst is prepared as follows:

[0065] Step (1): Place nickel foam (2*3.5 cm) 2 The sample was sequentially immersed in anhydrous ethanol, 3 mol / L dilute hydrochloric acid, and deionized water for ultrasonic cleaning for 10 min to remove surface oil and oxide layer, and then dried in a vacuum drying oven at 50℃.

[0066] Step (2): Dissolve 0.3489 g of nickel nitrate and 0.3708 g of ammonium molybdate in 30 mL of deionized water and stir until homogeneous. The concentration of nickel nitrate in the solution is 40 mmol / L, and the concentration of ammonium molybdate is 10 mmol / L. Transfer the solution to a 50 mL high-pressure reactor and place the dried nickel foam inside. The hydrothermal reaction temperature is 150℃, and the reaction time is 6 h. After the reaction is completed, cool to room temperature, wash the sample several times with deionized water, and dry it in a 60℃ electric heating oven to obtain a yellow NiMoO4 catalyst.

[0067] Step (3): Add 1.3902 g of ferrous sulfate to 50 mL of deionized water and stir until homogeneous. The concentration of ferrous sulfate in the solution is 0.1 mol / L. Impregnate the NiMoO4 catalyst obtained in step (2) in this solution at a temperature of 25°C for 60 s to obtain the Fe-NiMoO4 catalyst.

[0068] Step (4): Dissolve 16.833 g of KOH in 50 mL of deionized water and stir until homogeneous. The KOH concentration in the solution is 6 mol / L. Impregnate the Fe-NiMoO4 catalyst obtained in step (3) in an alkaline solution at 25 °C for 6.0 h. After impregnation, wash several times with deionized water and dry in a 60 °C electric heating oven to finally obtain yellow-green NiMoO4@NiFe(OH). x Hierarchical catalysts.

[0069] Example 4

[0070] This embodiment discloses a NiMoO4@NiFe(OH) method. x The hierarchical catalyst is prepared as follows:

[0071] Step (1): Place the nickel foam (2*3.5cm) 2 The sample was sequentially immersed in anhydrous ethanol, 3 mol / L dilute hydrochloric acid, and deionized water for ultrasonic cleaning for 10 min to remove surface oil and oxide layer, and then dried in a vacuum drying oven at 50℃.

[0072] Step (2): Dissolve 0.3489 g of nickel nitrate and 0.3708 g of ammonium molybdate in 30 mL of deionized water and stir until homogeneous. The concentration of nickel nitrate in the solution is 40 mmol / L, and the concentration of ammonium molybdate is 10 mmol / L. Transfer the solution to a 50 mL high-pressure reactor and place the dried nickel foam inside. The hydrothermal reaction temperature is 150℃, and the reaction time is 6 h. After the reaction is completed, cool to room temperature, wash the sample several times with deionized water, and dry it in a 60℃ electric heating oven to obtain a yellow NiMoO4 catalyst.

[0073] Step (3): Add 1.3902 g of ferrous sulfate to 50 mL of deionized water and stir until homogeneous. The concentration of ferrous sulfate in the solution is 0.1 mol / L. Impregnate the NiMoO4 catalyst obtained in step (2) in this solution at a temperature of 25°C for 30 s to obtain the Fe-NiMoO4 catalyst.

[0074] Step (4): Dissolve 16.833 g of KOH in 50 mL of deionized water and stir until homogeneous. The KOH concentration in the solution is 6 mol / L. Impregnate the Fe-NiMoO4 catalyst obtained in step (3) in an alkaline solution at 25℃ for 1.0 h. After impregnation, wash several times with deionized water and dry in a 60℃ electric heating oven to finally obtain yellow-green NiMoO4@NiFe(OH). x Hierarchical catalysts.

[0075] Example 5

[0076] This embodiment discloses a NiMoO4@NiFe(OH) method. x The hierarchical catalyst is prepared as follows:

[0077] Step (1): Place nickel foam (2*3.5 cm) 2 The sample was sequentially immersed in anhydrous ethanol, 3 mol / L dilute hydrochloric acid, and deionized water for ultrasonic cleaning for 10 min to remove surface oil and oxide layer, and then dried in a vacuum drying oven at 50℃.

[0078] Step (2): Dissolve 0.3489 g of nickel nitrate and 0.3708 g of ammonium molybdate in 30 mL of deionized water and stir until homogeneous. The concentration of nickel nitrate in the solution is 40 mmol / L, and the concentration of ammonium molybdate is 10 mmol / L. Transfer the solution to a 50 mL high-pressure reactor and place the dried nickel foam inside. The hydrothermal reaction temperature is 150℃, and the reaction time is 6 h. After the reaction is completed, cool to room temperature, wash the sample several times with deionized water, and dry it in a 60℃ electric heating oven to obtain a yellow NiMoO4 catalyst.

[0079] Step (3): Add 1.3902 g of ferrous sulfate to 50 mL of deionized water and stir until homogeneous. The concentration of ferrous sulfate in the solution is 0.1 mol / L. Impregnate the NiMoO4 catalyst obtained in step (2) in this solution at a temperature of 25°C for 300 s to obtain the Fe-NiMoO4 catalyst.

[0080] Step (4): Dissolve 16.833 g of KOH in 50 mL of deionized water and stir until homogeneous. The KOH concentration in the solution is 6 mol / L. Impregnate the Fe-NiMoO4 catalyst obtained in step (3) in an alkaline solution at 25℃ for 1.0 h. After impregnation, wash several times with deionized water and dry in a 60℃ electric heating oven to finally obtain yellow-green NiMoO4@NiFe(OH). x Hierarchical catalysts.

[0081] Example 6

[0082] This embodiment discloses a NiMoO4@NiFe(OH) method. x The hierarchical catalyst is prepared as follows:

[0083] Step (1): Place nickel foam (2*3.5 cm) 2 The sample was sequentially immersed in anhydrous ethanol, 3 mol / L dilute hydrochloric acid, and deionized water for ultrasonic cleaning for 10 min to remove surface oil and oxide layer, and then dried in a vacuum drying oven at 50℃.

[0084] Step (2): Dissolve 0.3489 g of nickel nitrate and 0.3708 g of ammonium molybdate in 30 mL of deionized water and stir until homogeneous. The concentration of nickel nitrate in the solution is 40 mmol / L, and the concentration of ammonium molybdate is 10 mmol / L. Transfer the solution to a 50 mL high-pressure reactor and place the dried nickel foam inside. The hydrothermal reaction temperature is 150℃, and the reaction time is 6 h. After the reaction is completed, cool to room temperature, wash the sample several times with deionized water, and dry it in a 60℃ electric heating oven to obtain a yellow NiMoO4 catalyst.

[0085] Step (3): Add 6.9510 g of ferrous sulfate to 50 mL of deionized water and stir until homogeneous. The concentration of ferrous sulfate in the solution is 0.5 mol / L. Impregnate the NiMoO4 catalyst obtained in step (2) in this solution at a temperature of 25 °C for 60 s to obtain the Fe-NiMoO4 catalyst.

[0086] Step (4): Dissolve 16.833 g of KOH in 50 mL of deionized water and stir until homogeneous. The KOH concentration in the solution is 6 mol / L. Impregnate the Fe-NiMoO4 catalyst obtained in step (3) in an alkaline solution at 25 °C for 1.0 h. After impregnation, wash several times with deionized water and dry in a 60 °C electric heating oven to finally obtain yellow-green NiMoO4@NiFe(OH). x Hierarchical catalysts.

[0087] Comparative Example 1

[0088] This embodiment discloses a catalyst, which differs from Example 1 in that the preparation is completed after step (2), and no subsequent impregnation with iron solution and alkali solution is performed, i.e., steps (3) and (4) are omitted, while the remaining operations remain the same, resulting in a yellow NiMoO4 catalyst.

[0089] Comparative Example 2

[0090] This embodiment discloses a catalyst, which differs from Embodiment 1 in that step (2) after obtaining NiMoO4 is not followed by step (3), but directly followed by step (4) to obtain the green NiMoO4@Ni(OH)2 catalyst.

[0091] Comparative Example 3

[0092] This embodiment discloses a catalyst for using nickel foam (2*3.5 cm) 2 The electrodes were sequentially immersed in anhydrous ethanol, 3 mol / L dilute hydrochloric acid, and deionized water for ultrasonic cleaning for 10 min to remove surface oil and oxide layer, and then dried in a vacuum drying oven at 50°C to obtain nickel foam electrodes.

[0093] The NiMoO4@NiFe(OH) compounds from Examples 1-6 were compared respectively. x The hierarchical catalyst and the catalysts of comparative examples 1-3 were tested. The test methods and results are as follows:

[0094] Figure 1 The NiMoO4@NiFe(OH) prepared in Examples 1 and 2 of this invention. x A picture of the actual product. For example... Figure 1 As shown, the prepared NiMoO4@NiFe(OH) x It grows uniformly and has a yellowish-green surface color.

[0095] Figure 2 This is a 150x magnified microscopic image of NiMoO4@NiFe(OH)x prepared in Example 1 of this invention. High-resolution measuring microscopes were used to observe NiFe(OH)... x Nanosheets cover the surface of the NiMoO4 submicron rod structure. This hierarchical heterogeneous structure increases the contact area with the electrolyte, which is beneficial for the rapid release of oxygen from the product and can also promote charge transfer of the catalyst, thus giving it excellent catalytic performance in the electrocatalytic oxygen evolution reaction.

[0096] Figure 3 The NiMoO4@NiFe(OH) prepared in Example 1 of this invention x The oxygen evolution performance test results of the catalyst and the comparative catalyst are shown in the figure. The NiMoO4@NiFe(OH) catalyst prepared in Example 1 is also shown. x The catalyst was cut into pieces with a working area of ​​1.0 x 1.0 cm. 2 The platinum electrode was used directly as the working electrode, the platinum sheet as the counter electrode, and Hg / HgO as the reference electrode. Cyclic voltammetry (CV) was used on a CHI 660E electrochemical workstation at room temperature in 1M KOH solution to study NiMoO4@NiFe(OH). xThe catalyst was first activated, and then polarization curves were obtained using linear sweep voltammetry (LSV). The test results were not IR compensated. Figure 3 It can be seen that this NiMoO4@NiFe(OH) x The catalyst requires only 327 mV overpotential to drive 100 mAcm in the oxygen evolution reaction. -2 The current density, based on the test results, is [data related to NiMoO4@NiFe(OH)]. x The catalyst is significantly superior to the NiMoO4, NiMoO4@Ni(OH)2, and nickel foam (NF) prepared in the comparative example.

[0097] Figure 4 The NiMoO4@NiFe(OH) prepared in Example 1 of this invention x The stability test diagram for the oxygen evolution reaction is shown. In the three-electrode system, the current density is 100 mA cm⁻¹. -2 Below, NiMoO4@NiFe(OH) x The catalyst can maintain stable catalytic activity for at least 25 hours, indicating that the catalyst has good stability.

[0098] Figure 5 The NiMoO4@NiFe(OH) prepared in Example 2 of this invention x This is a test chart of the anode stability of the AEMWE electrolytic cell. The NiMoO4@NiFe(OH) prepared in Example 2 was used. x The catalyst was cut into pieces with a working area of ​​25*25 cm. 2 The electrode material is directly used as the anode in the electrolytic cell, while the cathode uses a commercially available Raney nickel mesh. The electrolytic cell employs a double-sided inlet, with the inlet temperature maintained at approximately 60°C and the alkali concentration at 20% KOH. The current density is 0.8 A cm⁻¹. -2 Under these conditions, the AEMWE electrolytic cell can operate stably for 100 hours, with a performance degradation of only 30 µV / h. This indicates that the NiMoO4@NiFe(OH) electrolytic cell... x As an anode for electrolytic cells, it can withstand high temperatures and strong alkalis. In summary, the NiMoO4@NiFe(OH) prepared in this invention... x The catalyst exhibits good catalytic performance and high stability in the OER process.

[0099] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A NiMoO4@NiFe(OH) compound x A method for preparing a hierarchical catalyst, characterized in that, Includes the following steps: Step 1: Immerse the nickel foam in anhydrous ethanol, dilute hydrochloric acid and deionized water in sequence for ultrasonic cleaning to remove surface oil and oxide layer; Step 2: Dissolve nickel nitrate and ammonium molybdate in deionized water, stir evenly, and then place them together with the pretreated nickel foam from Step 1 in a high-pressure reactor for hydrothermal reaction to grow NiMoO4 in situ on the nickel foam substrate; after the reaction is completed, clean and dry to obtain nickel foam loaded with NiMoO4. Step 3: Dissolve iron salt in deionized water to form an iron salt solution, and immerse the nickel foam loaded with NiMoO4 obtained in Step 2 in the iron salt solution to obtain nickel foam loaded with Fe-NiMoO4. Step 4: Dissolve KOH in deionized water to form an alkaline solution. Immerse the Fe-NiMoO4-loaded nickel foam obtained in Step 3 in the alkaline solution. After washing and drying, obtain NiMoO4@NiFe(OH). x Hierarchical catalyst, where x = 1.5-3.

2. The NiMoO4@NiFe(OH) according to claim 1 x A method for preparing a hierarchical catalyst, characterized in that, In step 1, the concentration of the dilute hydrochloric acid is 1-3 mol / L; And / or, the ultrasonic cleaning time is 10-20 min.

3. The NiMoO4@NiFe(OH) according to claim 1 x A method for preparing a hierarchical catalyst, characterized in that, In step 2, the concentration of nickel nitrate is 30-50 mmol / L; And / or, the concentration of the ammonium molybdate is 5-20 mmol / L; And / or, the hydrothermal reaction temperature is 120-160℃, and the reaction time is 4-10 hours.

4. The NiMoO4@NiFe(OH) according to claim 1 x A method for preparing a hierarchical catalyst, characterized in that, In step 3, the iron salt is one or more of ferrous sulfate, ferric nitrate, and ferric chloride; And / or, the iron ion concentration in the iron salt solution is 0.05-0.6 mol / L; And / or, the impregnation temperature is 20~50℃, and the impregnation time is 10-500 s.

5. The NiMoO4@NiFe(OH) according to claim 1 x A method for preparing a hierarchical catalyst, characterized in that, In step 4, the concentration of the KOH solution is 4~6.5 mol / L; And / or, the immersion temperature is 20~50℃, and the immersion time is 0.5-8 h.

6. The NiMoO4@NiFe(OH) according to claim 1 x A method for preparing a hierarchical catalyst, characterized in that, After impregnation in steps 2 and 4, the catalyst is washed multiple times with deionized water and dried in a 60°C electric heating oven.

7. A NiMoO4@NiFe(OH) compound x Hierarchical catalyst, characterized in that, It is prepared by the method described in any one of claims 1-6.

8. The NiMoO4@NiFe(OH) according to claim 7 x Hierarchical catalyst, characterized in that, It uses nickel foam as a substrate, on which NiMoO4 microrod structures are grown, and the surface of the NiMoO4 microrod structures is in situ coated with NiFe(OH). x Nanosheets form core-shell complexes with hierarchical heterogeneous structures.

9. A NiMoO4@NiFe(OH) compound x Application of hierarchical catalysts in the field of oxygen evolution through water electrolysis.

10. The application according to claim 9, characterized in that, The NiMoO4@NiFe(OH) x Application of hierarchical catalysts as anodes in alkaline anion exchange membrane water electrolyzers.

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