Nickel-iron layered double hydroxide / iron oxide composite material and method for preparing the same

Abstract

The application discloses a kind of nickel-iron layered double hydroxide / iron oxide composite material and preparation method thereof, main preparation steps are respectively configured ferric salt and triethanolamine solution;The complex solution of ferric ion and triethanolamine is obtained after triethanolamine solution is added dropwise into ferric salt solution, and then the solution is treated using microwave hydrothermal to obtain iron oxide precursor dispersion;After the mixed solution of nickel salt and triethanolamine is configured, it is added into iron oxide precursor dispersion and is mixed uniformly by ultrasonic treatment;The mixture is transferred to microwave hydrothermal reaction bottle, and then microwave hydrothermal treatment is carried out, after treatment is completed, precipitated product is washed by centrifugation using deionized water and ethanol, and finally vacuum drying obtains nickel-iron layered double hydroxide / iron oxide composite material.The nickel-iron layered double hydroxide / iron oxide composite material prepared by the microwave hydrothermal method of the application has simple preparation process and shows good electrochemical oxygen evolution activity.

Description

Technical Field

[0001] This invention belongs to the field of inorganic material preparation technology, specifically, it relates to a nickel-iron layered bimetallic hydroxide / iron oxide composite material and its preparation method. Background Technology

[0002] Hydrogen energy boasts advantages such as cleanliness, high efficiency, safety, and sustainability, helping to alleviate the energy crisis and environmental pollution problems. It is the most promising secondary clean energy source for human sustainable development. Water electrolysis is an important method for producing hydrogen. However, the slow kinetics and high energy barrier of the oxygen evolution reaction (OER) during water electrolysis severely limit its efficiency. Ruthenium dioxide and iridium dioxide are currently recognized as the best-performing electrocatalysts for the OER, but their high price and scarcity limit their large-scale application. Therefore, finding a low-cost, highly active, and highly stable OER electrocatalyst is crucial to improving water electrolysis efficiency.

[0003] Layered bimetallic hydroxides (LBHs) are a typical class of two-dimensional layered materials. They are rich in raw materials, possess flexible and varied compositions and structures, and exhibit unique physicochemical properties, showing broad application prospects in the field of hydrogen production through water electrolysis. Among various LBHs, nickel-iron LBHs have attracted widespread attention due to their excellent electrochemical performance. However, their relatively poor conductivity and the tendency for the layers to stack prevent the active sites from being fully exposed, significantly limiting their electrocatalytic oxygen evolution activity. To optimize the electrochemical activity of nickel-iron LBHs, extensive research has focused on improving their electrocatalytic oxygen evolution activity through morphology control, intercalation, doping, and the construction of composite structures. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to provide a method for preparing nickel-iron layered bimetallic hydroxide / iron oxide composite material that is simple to operate, uses simple raw materials, and is low in cost.

[0005] The technical solution of the present invention to solve the above-mentioned technical problems is as follows:

[0006] A method for preparing a nickel-iron layered bimetallic hydroxide / iron oxide composite material includes the following steps:

[0007] To prepare an iron salt solution, weigh 0.245–0.606 g of iron salt and dissolve it in 10–20 mL of ultrapure water to prepare an iron salt solution with a concentration of 0.05–0.15 mol / L.

[0008] To prepare a triethanolamine solution, weigh 0.895–4.028 g of triethanolamine and dissolve it in 10–20 mL of ultrapure water to prepare a triethanolamine solution with a concentration of 0.3–2.7 mol / L.

[0009] To prepare a precursor dispersion, iron salt solution and triethanolamine solution were taken at a volume ratio of 3:1. The triethanolamine solution was added dropwise to the iron salt solution, and then the mixture was magnetically stirred for 1 hour to obtain a clear solution. The clear solution was then subjected to microwave hydrothermal treatment to obtain a precursor dispersion containing iron oxide.

[0010] To obtain the reaction solution, weigh 0.475–1.745 g of nickel salt and 0.597–3.581 g of triethanolamine and dissolve them in 40–60 mL of ultrapure water. After the nickel salt and triethanolamine are completely dissolved, add the iron oxide precursor dispersion and mix the solution evenly by ultrasonic dispersion to obtain the reaction solution.

[0011] For microwave hydrothermal reaction, take 10-20 mL of the reaction liquid and put it into the microwave hydrothermal reaction flask to start the microwave hydrothermal reaction.

[0012] Centrifuge the reaction liquid after the microwave hydrothermal reaction has ended and the reaction liquid has cooled to room temperature, and collect the precipitate after centrifugation.

[0013] Cleaning: Use ultrapure water or anhydrous ethanol to clean the precipitate.

[0014] The precipitate was collected by drying and then vacuum dried. After drying, a nickel-iron layered bimetallic hydroxide / iron oxide composite material was obtained.

[0015] Wherein, the molar ratio of iron ions to triethanolamine in the mixed solution used to prepare the iron oxide precursor dispersion is 1:2 to 6, and the molar ratio of nickel ions to triethanolamine in the reaction solution is 1:2 to 4.

[0016] The present invention also provides a nickel-iron layered bimetallic hydroxide / iron oxide composite material prepared by the above preparation method, wherein the nickel-iron layered bimetallic hydroxide / iron oxide composite material exhibits an ultrathin nanosheet structure.

[0017] The present invention has the following beneficial effects:

[0018] (1) The present invention uses microwave hydrothermal method to prepare nickel-iron layered bimetallic hydroxide / iron oxide composite material. The preparation process is simple and efficient, the raw materials required are simple, the cost is low, and the reaction time is short, which helps to realize large-scale industrial application.

[0019] (2) The nickel-iron layered bimetallic hydroxide / iron oxide composite material prepared by the present invention has an ultra-thin sheet structure, which helps to expose more active sites and exhibits good electrocatalytic oxygen evolution activity. At the same time, it has potential application prospects in the fields of adsorption, catalysis, and electrochemical energy storage. Attached Figure Description

[0020] Figure 1 This is a TEM image of the surface morphology of the product obtained in Example 1 of the present invention.

[0021] Figure 2 This is a TEM image of the surface morphology of the product obtained in Example 2 of the present invention.

[0022] Figure 3 This is a TEM image of the surface morphology of the product obtained in Example 3 of the present invention.

[0023] Figure 4 The OER polarization curves of the products obtained in Examples 1-3 and Comparative Example 1 of this invention in 1M KOH solution are shown.

[0024] Figure 5 The Tafel slope diagrams are shown for the products obtained in Examples 1-3 and Comparative Example 1 of this invention in 1M KOH solution.

[0025] Figure 6 The X-ray diffraction patterns are those of the products obtained in Examples 1-3 and Comparative Example 1 of the present invention. Detailed Implementation

[0026] The purpose of this invention is to provide a nickel-iron layered bimetallic hydroxide / iron oxide (NiFe LDH / Fe2O3) composite material and its preparation method via a microwave hydrothermal method. This method utilizes microwaves as a heating tool, enabling molecular-level stirring, rapid and uniform heating, significantly shortening reaction time and improving heating efficiency. By optimizing the molar ratio of triethanolamine to the metal salt, reaction time, and temperature, a small and uniform nickel-iron layered bimetallic hydroxide / iron oxide composite material is prepared. The nickel-iron layered bimetallic hydroxide / iron oxide composite material prepared by this invention exhibits an ultrathin nanosheet structure, which helps expose more active sites and demonstrates good electrocatalytic oxygen evolution activity. It also shows potential applications in adsorption, catalysis, and electrochemical energy storage. The invention is further described in detail below with reference to specific examples.

[0027] Example 1:

[0028] The preparation method of the nickel-iron layered bimetallic hydroxide / iron oxide composite material of Example 1 of the present invention includes the following steps:

[0029] To prepare an iron salt solution, 0.324 g of iron salt was weighed and dissolved in 15 mL of ultrapure water to prepare an iron salt solution with a concentration of 0.08 mol / L. The iron salt was at least one of ferric sulfate pentahydrate, ferric chloride hexahydrate, and ferric nitrate nonahydrate. In this embodiment, ferric chloride hexahydrate was used as the iron salt. Only ferric iron sources could be selected. Choosing a ferrous iron source would lead to the formation of ferric oxide impurities and result in larger and thicker products. This is because the complex of ferric ions and triethanolamine is more stable and has greater solubility than the complex of ferrous ions and triethanolamine. Adding triethanolamine to a ferrous salt solution would directly cause the precipitation of ferrous ions.

[0030] To prepare a triethanolamine solution, 2.864 g of triethanolamine was weighed and dissolved in 20 mL of ultrapure water to prepare a triethanolamine solution with a concentration of 0.96 mol / L.

[0031] To prepare the precursor dispersion, 15 mL of iron salt solution and 5 mL of triethanolamine solution were taken at a volume ratio of 3:1. The triethanolamine solution was added dropwise to the iron salt solution, followed by magnetic stirring for 1 hour to obtain a clear solution. The clear solution was then subjected to microwave hydrothermal treatment to obtain a precursor dispersion containing iron oxide (Fe2O3). Specifically, the microwave hydrothermal treatment of the clear solution was performed at a temperature of 100℃, a stirring speed of 600 rpm, and a reaction time of 10 minutes. The molar ratio of iron ions to triethanolamine in the mixed solution used to prepare the iron oxide precursor dispersion was 1:4. A molar ratio of triethanolamine to iron ions that is too low will prevent the formation of a clear metal complex solution, while a molar ratio that is too high will hinder the conversion of the metal complex to iron oxide.

[0032] To obtain the reaction solution, 0.571 g of nickel salt and 1.074 g of triethanolamine were weighed and dissolved in 40 mL of ultrapure water. After the nickel salt and triethanolamine were completely dissolved, an iron oxide precursor dispersion was added. The solution was then ultrasonically dispersed to ensure uniform mixing, thus obtaining the reaction solution. The nickel salt was one of nickel sulfate hexahydrate, nickel chloride hexahydrate, or nickel nitrate hexahydrate. In this embodiment, nickel chloride hexahydrate was used as the nickel salt. The molar ratio of nickel ions to triethanolamine in the obtained reaction solution was 1:3. Triethanolamine has a certain alkalinity and acts as both a complexing agent and a precipitating agent in this reaction, eliminating the need for additional precipitating agent. A molar ratio of triethanolamine to nickel ions that is too low will result in the formation of impurities, preventing the formation of nickel-iron layered bimetallic hydroxide / iron oxide. A molar ratio that is too high is detrimental to the formation of nickel-iron layered bimetallic hydroxide.

[0033] For microwave hydrothermal reaction, 20 mL of the reaction liquid is placed in a microwave hydrothermal reaction flask to begin the reaction. Before starting the reaction, the reaction solution in the flask is pre-stirred for 5 minutes. After pre-stirring, the microwave hydrothermal reaction begins at 100°C, with a stirring speed of 660 rpm, for 40 minutes. Different temperatures and times in the microwave hydrothermal reaction can control the ratio of nickel-iron layered bimetallic hydroxide to iron oxide in the resulting product, as well as the size and thickness of the nanosheets. At the optimal reaction temperature and time, nickel-iron layered bimetallic hydroxide / iron oxide nanosheets with high OER activity can be obtained. Reactions below the lower limit of temperature and time are unfavorable for the formation of nickel-iron layered bimetallic hydroxide, while reactions above the upper limit yield nickel-iron layered bimetallic hydroxide with increased nanosheet thickness.

[0034] Centrifugation is performed after the microwave hydrothermal reaction ends and the reaction liquid cools to room temperature. The precipitate formed after centrifugation is collected. Centrifugation is used to remove excess solution and retain only the precipitate, which is a semi-finished composite material.

[0035] Washing: Use ultrapure water or anhydrous ethanol to wash the precipitate; washing can be done multiple times to completely remove impurities.

[0036] The precipitate was collected and dried under vacuum at 50°C. After drying, a nickel-iron layered bimetallic hydroxide / iron oxide composite material was obtained.

[0037] The nickel-iron layered bimetallic hydroxide / iron oxide composite material obtained in this embodiment was obtained after TEM imaging as follows: Figure 1 The surface morphology TEM image shown.

[0038] Example 2:

[0039] The preparation method of the nickel-iron layered bimetallic hydroxide / iron oxide composite material of Example 2 of the present invention includes the following steps:

[0040] To prepare an iron salt solution, 0.485 g of iron salt was weighed and dissolved in 15 mL of ultrapure water to prepare an iron salt solution with a concentration of 0.08 mol / L. In this example, ferric nitrate nonahydrate was used as the iron salt.

[0041] To prepare a triethanolamine solution, 2.864 g of triethanolamine was weighed and dissolved in 20 mL of ultrapure water to prepare a triethanolamine solution with a concentration of 0.96 mol / L.

[0042] To prepare the precursor dispersion, 15 mL of iron salt solution and 5 mL of triethanolamine solution were taken at a volume ratio of 3:1. The triethanolamine solution was added dropwise to the iron salt solution, followed by magnetic stirring for 1 hour to obtain a clear solution. The clear solution was then subjected to microwave hydrothermal treatment to obtain a precursor dispersion containing iron oxide (Fe2O3). Specifically, the microwave hydrothermal treatment of the clear solution was performed at a temperature of 100℃, a stirring speed of 600 rpm, and a reaction time of 10 minutes. The molar ratio of iron ions to triethanolamine in the mixed solution used to prepare the iron oxide precursor dispersion was 1:4.

[0043] To obtain the reaction solution, 1.047 g of nickel salt and 2.148 g of triethanolamine were weighed and dissolved in 40 mL of ultrapure water. After the nickel salt and triethanolamine were completely dissolved, the iron oxide precursor dispersion was added, and the solution was mixed evenly by ultrasonic dispersion to obtain the reaction solution. In this embodiment, nickel nitrate hexahydrate was used as the nickel salt. The molar ratio of nickel ions to triethanolamine in the obtained reaction solution was 1:4.

[0044] For the microwave hydrothermal reaction, 20 mL of the reaction liquid was placed into a microwave hydrothermal reaction flask to begin the reaction. Before starting the microwave hydrothermal reaction, the reaction solution in the microwave hydrothermal reaction flask was pre-stirred for 5 minutes. After pre-stirring, the microwave hydrothermal reaction was started at a temperature of 120℃, a stirring speed of 660 rpm, and a reaction time of 30 minutes.

[0045] Centrifugation is performed after the microwave hydrothermal reaction ends and the reaction liquid cools to room temperature. The precipitate formed after centrifugation is collected. Centrifugation is used to remove excess solution and retain only the precipitate, which is a semi-finished composite material.

[0046] Washing: Use ultrapure water or anhydrous ethanol to wash the precipitate; washing can be done multiple times to completely remove impurities.

[0047] The precipitate was collected and dried under vacuum at 50°C. After drying, a nickel-iron layered bimetallic hydroxide / iron oxide composite material was obtained.

[0048] The nickel-iron layered bimetallic hydroxide / iron oxide composite material obtained in this embodiment was obtained after TEM imaging as follows: Figure 2 The surface morphology TEM image shown.

[0049] Example 3:

[0050] The preparation method of the nickel-iron layered bimetallic hydroxide / iron oxide composite material of Example 3 of the present invention includes the following steps:

[0051] To prepare an iron salt solution, 0.294 g of iron salt was weighed and dissolved in 15 mL of ultrapure water to prepare an iron salt solution with a concentration of 0.8 mol / L. In this example, ferric sulfate pentahydrate was used as the iron salt.

[0052] To prepare a triethanolamine solution, 4.297 g of triethanolamine was weighed and dissolved in 20 mL of ultrapure water to prepare a triethanolamine solution with a concentration of 1.44 mol / L.

[0053] To prepare the precursor dispersion, 15 mL of iron salt solution and 5 mL of triethanolamine solution were taken at a volume ratio of 3:1. The triethanolamine solution was added dropwise to the iron salt solution, followed by magnetic stirring for 1 hour to obtain a clear solution. The clear solution was then subjected to microwave hydrothermal treatment to obtain a precursor dispersion containing iron oxide (Fe2O3). Specifically, the microwave hydrothermal treatment of the clear solution was performed at a temperature of 100℃, a stirring speed of 600 rpm, and a reaction time of 10 minutes. The molar ratio of iron ions to triethanolamine in the mixed solution used to prepare the iron oxide precursor dispersion was 1:6.

[0054] To obtain the reaction solution, 1.262 g of nickel salt and 2.864 g of triethanolamine were weighed and dissolved in 40 mL of ultrapure water. After the nickel salt and triethanolamine were completely dissolved, the iron oxide precursor dispersion was added, and the solution was mixed evenly by ultrasonic dispersion to obtain the reaction solution. In this example, nickel sulfate hexahydrate was used as the nickel salt. The molar ratio of nickel ions to triethanolamine in the obtained reaction solution was 1:4.

[0055] For the microwave hydrothermal reaction, 20 mL of the reaction liquid was placed into a microwave hydrothermal reaction flask to begin the reaction. Before starting the microwave hydrothermal reaction, the reaction solution in the microwave hydrothermal reaction flask was pre-stirred for 5 minutes. After pre-stirring, the microwave hydrothermal reaction was started at a temperature of 140℃, a stirring speed of 660 rpm, and a reaction time of 30 minutes.

[0056] Centrifugation is performed after the microwave hydrothermal reaction ends and the reaction liquid cools to room temperature. The precipitate formed after centrifugation is collected. Centrifugation is used to remove excess solution and retain only the precipitate, which is a semi-finished composite material.

[0057] Washing: Use ultrapure water or anhydrous ethanol to wash the precipitate; washing can be done multiple times to completely remove impurities.

[0058] The precipitate was collected and dried under vacuum at 50°C. After drying, a nickel-iron layered bimetallic hydroxide / iron oxide composite material was obtained.

[0059] The nickel-iron layered bimetallic hydroxide / iron oxide composite material obtained in this embodiment was obtained after TEM imaging as follows: Figure 3 The surface morphology TEM image shown.

[0060] Comparative Example 1:

[0061] (1) Weigh 0.324g of ferric chloride hexahydrate and dissolve it in 15mL of ultrapure water. Stir magnetically for 15min to ensure complete dissolution.

[0062] (2) Weigh 2.864g of triethanolamine and dissolve it completely in 20mL of ultrapure water;

[0063] (3) Add 5 mL of triethanolamine solution dropwise to ferric chloride solution, stir magnetically for 1 h to obtain a clear solution, and then treat it in an oil bath at 100 °C for 2 h to obtain Fe2O3 precursor dispersion.

[0064] (4) Weigh 0.571g of nickel chloride hexahydrate and 1.074g of triethanolamine and dissolve them in 40mL of ultrapure water. After they are fully dissolved, add them to the Fe2O3 precursor dispersion obtained in step (3). After ultrasonic dispersion, make it evenly dispersed and then transfer it to a polytetrafluoroethylene reactor and hydrothermally heat it at 100℃ for 6h.

[0065] (5) Following the method described in step (4), after the reaction is completed and cooled to room temperature, the reaction product is collected by centrifugation. The precipitated product is washed with ultrapure water and anhydrous ethanol. After vacuum drying at 50°C, the sample is collected to obtain nickel-iron layered bimetallic hydroxide / iron oxide composite material.

[0066] The oxygen evolution catalytic performance of the nickel-iron layered bimetallic hydroxide / iron oxide composite materials prepared in Examples 1-3 and Comparative Example 1 was tested using a three-electrode system. The prepared nickel-iron layered bimetallic hydroxide / iron oxide was used as the working electrode, a graphite rod as the counter electrode, and mercury / mercury oxide as the reference electrode. A 1M potassium hydroxide solution was used as the electrolyte, and the electrochemical oxygen evolution performance of the prepared samples was evaluated by polarization curve testing. After testing, when the current density reached 20 mA cm⁻¹, the oxygen evolution performance was satisfactory. -2 At that time, the overpotentials required for oxygen evolution in the samples prepared in Examples 1, 2, 3, and Comparative Example 1 were 264, 267, 293, and 269 mV, respectively. Figure 4 As shown.

[0067] The Tafel slope of the products from Examples 1-3 and Comparative Example 1 was measured, and the results are as follows: Figure 5 As shown, the Tafel slopes of the four products in Examples 1-3 and Comparative Example 1 are 42.6, 53.3, 50.3, and 54.4 mV dec, respectively. -1 .

[0068] The above two performance test results show that the prepared nickel-iron layered bimetallic hydroxide / iron oxide has good electrocatalytic performance, and the electrocatalytic oxygen evolution performance of the sample prepared by microwave hydrothermal method in Example 1 is better than that of the sample prepared by hydrothermal method in Comparative Example 1 under the same raw material ratio.

[0069] In addition, XRD analysis was performed on the products of Examples 1-3 and Comparative Example 1 as follows: Figure 6 As shown, the spectral peaks correspond to standard cards PDF#40-0215 ​​and PDF#13-0092, indicating that the samples prepared in Examples 1, 2, 3 and Comparative Example 1 are composed of NiFe LDH and Fe2O3. It can be concluded that the nickel-iron layered bimetallic hydroxide / iron oxide composite material was successfully synthesized.

[0070] The above description, in conjunction with specific preferred embodiments, provides a further detailed explanation of the present invention. It should not be construed that the specific implementation of the present invention is limited to these descriptions. For those skilled in the art, various simple deductions or substitutions can be made without departing from the inventive concept, and all such modifications and substitutions should be considered within the scope of protection of the present invention.

Claims

1. A method for producing a nickel-iron layered double hydroxide / iron oxide composite material, characterized by, The method comprises the following steps: Preparation of iron salt solution, 0.245-0.606 g of ferric salt is weighed and dissolved in 10-20 mL of ultrapure water to prepare an iron salt solution with a concentration of 0.05-0.15 mol / L; Preparation of triethanolamine solution, 0.895-4.028 g of triethanolamine is weighed and dissolved in 10-20 mL of ultrapure water to prepare a triethanolamine solution with a concentration of 0.3-2.7 mol / L; Preparation of precursor dispersion, take the iron salt solution and the triethanolamine solution with a volume ratio of 3:1, add the triethanolamine solution dropwise into the iron salt solution, then perform magnetic stirring for 1 h to obtain a clear solution, and then perform microwave hydrothermal treatment on the clear solution to obtain an iron oxide precursor dispersion; Obtaining a reaction solution, 0.475-1.745 g of nickel salt and 0.597-3.581 g of triethanolamine are weighed and dissolved in 40-60 mL of ultrapure water, and then the iron oxide precursor dispersion is added after the nickel salt and the triethanolamine are completely dissolved, the solution is uniformly mixed through ultrasonic dispersion, and a reaction solution is obtained; Microwave hydrothermal reaction, 10-20 mL of the reaction liquid is taken into a microwave hydrothermal reaction bottle, and the microwave hydrothermal reaction is started; Centrifugation, after the microwave hydrothermal reaction is completed and the reaction liquid is cooled to room temperature, the reaction liquid is centrifuged, and the precipitated product after centrifugation is collected; Washing, the precipitated product is washed with ultrapure water or anhydrous ethanol; Drying and collection, the washed precipitated product is vacuum dried, and after the drying is completed, a nickel-iron layered double hydroxide / iron oxide composite material is obtained. In the mixed solution for preparing the iron oxide precursor dispersion, the molar ratio of iron ions to triethanolamine is 1:2-6, and in the reaction solution, the molar ratio of nickel ions to triethanolamine is 1:2-4.

2. The method of claim 1, wherein the method is characterized by: The iron salt is at least one of iron sulfate pentahydrate, iron chloride hexahydrate, and iron nitrate nonahydrate.

3. The method of claim 1, wherein the method is characterized by: The nickel salt is one of nickel sulfate hexahydrate, nickel chloride hexahydrate, and nickel nitrate hexahydrate.

4. The method of claim 2, wherein the method is characterized by: In the step of preparing the precursor dispersion, when the clear solution is subjected to microwave hydrothermal treatment, the microwave hydrothermal temperature is 100°C, the stirring speed is 600 rpm, and the reaction time is 10 min.

5. The method of claim 1, wherein the method is characterized by: In the step of microwave hydrothermal reaction, the reaction solution in the microwave hydrothermal reaction bottle is pre-stirred for 5-10 min before the microwave hydrothermal reaction starts.

6. The method of claim 5, wherein the method further comprises: In the step of microwave hydrothermal reaction, the reaction temperature of the microwave hydrothermal reaction is 80-160°C, the stirring speed is 500-800 rpm, and the reaction time is 30-60 min. ​ 7. The nickel-iron layered double hydroxide / iron oxide composite material produced by the method of any one of claims 1-6, wherein: The nickel-iron layered double hydroxide / iron oxide composite material presents an ultra-thin nanosheet structure.

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