Niobium-ion-doped hydrotalcite nano material, preparation method thereof and method for electro-catalyzing alkaline water to evolve oxygen by using niobium-ion-doped hydrotalcite nano material

Abstract

The invention belongs to the technical field of inorganic advanced nano materials, and particularly relates to a niobium ion doped hydrotalcite nano material, a preparation method thereof and an oxygen evolution method for electro-catalysis of alkaline water. The niobium ion doped hydrotalcite nanometer material comprises a conductive substrate, a hydrotalcite nanometer material growing on the surface of the conductive substrate and niobium ions doped in crystal lattices of the hydrotalcite nanometer material. The niobium ion doped hydrotalcite material is used as an anode catalyst for electrocatalysis of alkaline water reaction for the first time, niobium atoms can attract electrons around nickel atoms, the nickel atoms are promoted to be in a higher energy state after the reaction, the activity of alkaline water oxygen evolution reaction is improved, and the reaction efficiency is improved. Meanwhile, due to doping of niobium, the hydrotalcite material can be reconstructed earlier and faster in the oxygen evolution reaction process, and the occurrence rate of the oxygen evolution reaction is increased.

Description

Technical Field

[0001] The present invention belongs to the technical field of inorganic advanced nanomaterials, and particularly relates to a niobium ion-doped hydrotalcite nanomaterial, its preparation method, and a method for electrocatalytic alkaline water oxygen evolution. Background Art

[0002] As a highly efficient and clean secondary energy source, hydrogen energy is one of the core paths to promote the green transformation of the energy structure and achieve the goal of carbon neutrality. The electrolytic water hydrogen production technology has become a current research hotspot due to its zero-carbon emission characteristics. Among them, the alkaline electrolytic water technology has gradually achieved large-scale application with advantages such as mature reliability and controllable cost. However, the core bottleneck restricting its further development lies in the slow kinetics and high overpotential of the anodic oxygen evolution reaction (OER), resulting in a low overall energy conversion efficiency. Therefore, improving the activity and stability of the anode catalyst is the key to breaking through the technical barriers and reducing the hydrogen production cost.

[0003] Traditional alkaline electrolysis systems usually use noble metal-based (such as IrO2, RuO2) catalysts to accelerate the OER process. However, noble metals are scarce and costly, and the active components are prone to dissolution or structural collapse at high current densities, making it difficult to meet the long-term stability requirements of large-scale hydrogen production. In addition, the active sites of conventional catalysts are insufficiently exposed and the electron transport path is limited, resulting in a low utilization rate of the reaction interface and further exacerbating energy loss. In recent years, although non-noble metal catalysts (such as transition metal oxides and hydroxides) have shown potential, problems such as their insufficient intrinsic activity still hinder practical applications. Therefore, an efficient and stable oxygen evolution reaction catalyst should be developed for electrolytic alkaline water hydrogen production.

[0004] To solve the above problems, the present invention is proposed. Summary of the Invention

[0005] The present invention provides a method for electrocatalytic alkaline water oxygen evolution reaction using a niobium ion-doped hydrotalcite nanomaterial. The method includes: constructing an alkaline water electrolysis reactor with the niobium-doped hydrotalcite nanomaterial as the anode, and bringing the electrolyte into contact with the niobium ion-doped hydrotalcite nanomaterial. The niobium ions doped in the present invention have ultra-high oxygen evolution activity in an alkaline solution, and only need an overpotential of 198 mV to reach a current density of 10 mA / cm 2 . Due to the fact that niobium atoms can attract the electrons around low-valent metal atoms, promoting the low-valent metal atoms to be in a higher energy state after the reaction, improving the activity of the alkaline water oxygen evolution reaction. At the same time, the doping of niobium can enable the hydrotalcite material to reconstruct earlier and faster during the oxygen evolution reaction process, increasing the occurrence rate of the oxygen evolution reaction.

[0006] In the first aspect of the present invention, a niobium ion-doped hydrotalcite nanomaterial is provided. The niobium ion-doped hydrotalcite nanomaterial comprises a conductive substrate, a hydrotalcite nanomaterial grown on the surface of the conductive substrate, and niobium ions doped in the crystal lattice of the hydrotalcite nanomaterial.

[0007] Preferably, the molar fraction of the doped niobium ions is 0.1%-60%, based on the total molar number of metals in the hydrotalcite nanomaterial.

[0008] In the second aspect of the present invention, a preparation method of the niobium ion-doped hydrotalcite nanomaterial described in the first aspect is provided. The synthesis method of the niobium ion-doped hydrotalcite nanomaterial includes a hydrothermal reaction, an electrodeposition method, and a coprecipitation method. Specifically:

[0009] The hydrothermal reaction method includes the following steps: adding a metal salt, a niobium salt, and urea into water and dissolving them, transferring the solution into a hydrothermal reaction kettle, adding a conductive substrate, and then carrying out a hydrothermal reaction.

[0010] Preferably, in the hydrothermal reaction, the concentration of the metal salt is 0.01-0.3 mol / L, the concentration of the niobium salt is 0.01-0.2 mol / L, and the concentration of urea is 2-10 times the total molar concentration of the metal salt and the niobium salt.

[0011] The time of the hydrothermal reaction is 3h-48h, and the temperature is 60°C-200°C.

[0012] The electrodeposition method includes the following steps: adding a metal salt and a niobium salt into water and dissolving them, placing an anode, a cathode, and a reference electrode in the solution, using a conductive substrate at the cathode, and carrying out electrodeposition.

[0013] Preferably, the voltage of the electrodeposition is -1.0V to -1.4V vs SCE, and the time is 100s-7200s.

[0014] Preferably, in the electrodeposition method, the concentration of the metal salt is 0.01-0.3 mol / L, and the concentration of the niobium salt is 0.01-0.2 mol / L.

[0015] Preferably, the metal salt includes one or more of nickel salt, cobalt salt, iron salt, manganese salt, chromium salt, copper salt, and vanadium salt. When there are multiple types of metal salts, the concentration of the metal salt is the total concentration of the metals in the metal salts.

[0016] Preferably, the conductive substrate is one or more of a metal or a carbon material.

[0017] More preferably, the conductive substrate is one of nickel foam, iron foam, nickel-iron alloy foam, nickel mesh, iron mesh, and nickel-iron alloy mesh.

[0018] The coprecipitation method includes the following steps: adding niobium salt and metal salt into water and dissolving them to obtain a mixed metal salt solution, adding an alkaline substance and carbonate into water and dissolving them to obtain a dilute solution of the base, adding the mixed metal salt solution and the dilute solution of the base dropwise into water and controlling the pH within the range of 7-10 for coprecipitation, and finally mixing the obtained product with a perfluorosulfonic acid resin solution (Nafion solution) and dispersing it in an organic solvent, and coating it on a conductive substrate.

[0019] The temperature of the above coprecipitation reaction is 10-80 °C.

[0020] The above alkaline substance is sodium hydroxide or potassium hydroxide. The carbonate is sodium carbonate or potassium carbonate.

[0021] The above organic solvent is one or both of ethanol and methanol.

[0022] Preferably, the metal salt includes one or several of nickel salt, cobalt salt, iron salt, manganese salt, chromium salt, copper salt, and vanadium salt. When there are multiple types of metal salts, the concentration of the metal salt is the total concentration of the metals in the metal salt.

[0023] Preferably, in the coprecipitation method, the metal salt and niobium salt correspond to their nitrates, sulfates, or chlorides. The concentration of other metal ions except niobium salt in the mixed metal salt solution is 20-500 mmol / L, and the concentration of niobium salt is 5-200 mmol / L.

[0024] Preferably, the dilute solution of the base is a mixed solution of sodium hydroxide and sodium carbonate, the concentration of sodium hydroxide is 0.05-0.5 mol / L, and the concentration of sodium carbonate is 0.01-0.5 mol / L;

[0025] The third aspect of the present invention provides a method for electrocatalytic alkaline water oxygen evolution of a niobium ion-doped hydrotalcite nanomaterial. The niobium ion-doped hydrotalcite nanomaterial is used as the anode of an electrolytic reactor, and the electrolyte is brought into contact with the niobium ion-doped hydrotalcite nanomaterial.

[0026] The alkaline water contains an alkaline substance. The alkaline substance is selected from one or several of sodium hydroxide and potassium hydroxide, and the total concentration of the alkaline substance is 0.01-10 mol / L

[0027] Compared with the prior art, the present invention has the following beneficial effects:

[0028] 1. The present invention first applies niobium ion-doped hydrotalcite materials as anode catalysts for electrocatalytic alkaline water reactions. Since niobium atoms can attract the electrons around low-valent metal atoms, promoting the low-valent metal atoms (such as nickel atoms, cobalt atoms, iron atoms, manganese atoms, chromium atoms, copper atoms, vanadium atoms) to be in a higher energy state after the reaction, enhancing the activity of the alkaline water oxygen evolution reaction. At the same time, the doping of niobium enables the hydrotalcite material to reconstruct earlier and faster during the oxygen evolution reaction, improving the occurrence rate of the oxygen evolution reaction.

[0029] 2. It is unexpectedly found in the present invention that compared with the doping of other ions such as copper ions (divalent positive) and tin ions (tetravalent positive), the high-valent state (pentavalent positive) property of niobium ions after OER activation reduces the electron cloud density of other metal ions, making the metal valence state higher and the catalytic activity better.

[0030] 3. Generally, since niobium is located in Group IV A of the fourth period in the periodic table, compared with other metal elements, it has a relatively large ionic radius. Most people's view is that the larger the size, the less likely it is to be used as a material for doped hydrotalcite. And niobium ions are prone to hydrolysis in water, and after hydrolysis to form niobium oxide, they cannot be doped into the hydrotalcite. Therefore, it is not easy to think of using niobium as an ion for doped hydrotalcite materials. It is found in the use of the present invention that the hydrolysis degree of niobium is not large and has a relatively small impact on the synthesis. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 XRD of the niobium ion-doped nickel-iron hydrotalcite electrode prepared by the hydrothermal method in Example 1.

[0032] Figure 2 SEM image and EDS-Mapping of the niobium ion-doped nickel-iron hydrotalcite electrode prepared by the hydrothermal method in Example 1.

[0033] Figure 3 XRD of the niobium ion-doped nickel-iron hydrotalcite electrode prepared by the electrodeposition method in Example 3.

[0034] Figure 4 SEM image and EDS-Mapping of the niobium ion-doped nickel-iron hydrotalcite electrode prepared by the electrodeposition method in Example 3.

[0035] Figure 5 LSV curve graph of the niobium ion-doped nickel-iron hydrotalcite electrode in Application Example 1.

[0036] Figure 6 Constant current curve graph of the niobium ion-doped nickel-iron hydrotalcite electrode in Application Example 2.

[0037] Figure 7 LSV curve graph of the niobium ion-doped nickel-iron hydrotalcite electrode with different synthesis methods in Application Example 3.

[0038] Figure 8 CV curve of the copper-doped nickel-iron hydrotalcite electrode for Comparative Example 1.

[0039] Figure 9 Galvanostatic curve of the copper-doped nickel-iron hydrotalcite electrode for Comparative Example 2.

[0040] Figure 10 LSV curve of the tin-doped nickel-iron hydrotalcite electrode for Comparative Example 3 Figure 11 Linear sweep voltammogram of the nickel-iron hydrotalcite material electrode for Comparative Example 4. Detailed implementation mode

[0041] The present invention will be described below in conjunction with specific embodiments, but the implementation modes of the present invention are not limited thereto. For the experimental methods without specific conditions noted in the embodiments, they are generally carried out according to the conventional conditions and the conditions described in the manuals, or according to the conditions recommended by the manufacturers. For the general equipment, materials, reagents, etc., if not otherwise specified, they can all be obtained from commercial channels. The raw materials required in the following examples and comparative examples are all commercially available.

[0042] The "range" disclosed in this application is defined in the form of a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, and the selected lower limit and upper limit define the boundary of a specific range. The ranges defined in this way can include or exclude the end values, and can be combined arbitrarily, that is, any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60-120 and 80-110 are listed for a specific parameter, ranges of 60-110 and 80-120 are also contemplated. In addition, if the minimum range values 1 and 2 are listed, and if the maximum range values 3, 4, and 5 are listed, then the following ranges are all contemplated: 1-3, 1-4, 1-5, 2-3, 2-4, and 2-5. In this application, unless otherwise stated, the numerical range "a~b" represents the abbreviated representation of any real number combination between a and b, where a and b are both real numbers. For example, the numerical range "0~5" means that all real numbers between "0~5" have been fully listed in this article, and "0~5" is only the abbreviated representation of these numerical combinations. In addition, when it is stated that a certain parameter is an integer ≥2, it is equivalent to disclosing that the parameter is, for example, the integer 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0043] Unless otherwise specified, all embodiments and optional embodiments of the present application can be combined with each other to form new technical solutions. Unless otherwise specified, all technical features and optional technical features of the present application can be combined with each other to form new technical solutions. Unless otherwise specified, all steps of the present application can be carried out sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), which means that the method may include steps (a) and (b) carried out sequentially, or may include steps (b) and (a) carried out sequentially. For example, it is mentioned that the method may further include step (c), which means that step (c) can be added to the method in any order. For example, the method may include steps (a), (b) and (c), or may include steps (a), (c) and (b), or may include steps (c), (a) and (b), etc.

[0044] Unless otherwise specified, the "including" and "comprising" mentioned in the present application mean open-ended, and can also be closed-ended. For example, the "including" and "comprising" can mean that other components not listed can also be included or comprised, or can only include or comprise the listed components.

[0045] Unless otherwise specified, in the present application, the term "or" is inclusive. For example, the phrase "A or B" means "A, B, or both A and B".

[0046] Example 1 - Preparation and Characterization of Niobium Ion-Doped Hydrotalcite Materials by Hydrothermal Method

[0047] In this experimental example, the following method was used to prepare niobium-doped nickel-iron hydrotalcite. Of course, those skilled in the art can make adjustments with reference to the prior art:

[0048] Prepare 30 mL of a solution: 5 mmol of urea, 0.5 mmol of nickel nitrate, 0.49 mmol of iron nitrate, 0.01 mmol of niobium chloride, and 30 mL of water. Pour the solution into a reaction kettle. (In this solution, the metal salt concentration is 0.025 mmol / L, the niobium ion concentration is 0.00032 mmol / L, and the urea concentration is 0.16 mmol / L). Immerse the washed nickel foam into the solution, place it in an oven, with a reaction temperature of 120 °C and a time of 12 hours. The obtained material was washed 3 times with water and ethanol respectively, and dried in vacuum at 60 °C for 10 hours. Thus, the niobium-doped nickel-iron hydrotalcite material was obtained. The molar fraction of niobium in this material was calculated to be 0.1%, based on the total molar number of metal elements in the hydrotalcite nanomaterial.

[0049] With other conditions unchanged, replace the nickel nitrate in the above steps with an equimolar amount of cobalt nitrate, or a mixed salt of nickel nitrate and cobalt nitrate with the same total molar number. Thus, the niobium ion-doped cobalt-iron hydrotalcite material and the niobium ion-doped nickel-cobalt-iron hydrotalcite material can be prepared respectively.

[0050] Under other unchanged conditions, replace nickel nitrate in the above steps with one or more of manganese salts, chromium salts, copper salts, vanadium salts, and cobalt salts with the same total molar amount. Niobium ion-doped manganese (chromium, copper, vanadium, cobalt) iron hydrotalcite materials can be respectively prepared.

[0051] Under other unchanged conditions, replace nickel foam in the above steps with carbon paper. Niobium ion-doped nickel iron hydrotalcite materials supported on carbon paper can be respectively prepared.

[0052] Under other unchanged conditions, replace the reaction temperature of 120 °C in the above steps with 60, 80, 100, 150, and 200 °C. Niobium ion-doped nickel iron hydrotalcite materials can also be respectively prepared.

[0053] Perform X-ray diffraction (XRD) on the above niobium ion-doped nickel iron hydrotalcite material. The diffraction pattern is shown in Figure 1 , which is consistent with the standard card of nickel iron hydrotalcite, indicating that there is no phase separation during the synthesis process. Then, perform scanning electron microscopy (SEM) and X-ray energy spectrometer - elemental distribution test (EDS-Mapping) on this material. As shown in Figure 2 , the results show that the niobium ion-doped nickel iron hydrotalcite material synthesized by the hydrothermal method has an obvious flaky morphology and uniform elemental distribution, proving the successful doping of niobium ions.

[0054] Example 2 Preparation and Characterization of Niobium Ion-Doped Hydrotalcite Materials by Electrodeposition Method

[0055] Prepare 120 mL of solution: 0.6 mmol of cobalt nitrate, 0.6 mmol of iron nitrate, 1.8 mmol of niobium chloride, and 120 mL of water. (In this solution, the metal salt concentration is 0.005 mol / L and the niobium ion concentration is 0.015 mol / L). Use the washed nickel foam as the working electrode, the carbon rod electrode as the counter electrode, and the calomel electrode as the reference electrode. Apply a constant potential of -1.2 V vs SCE for 600 s. The obtained materials are washed 3 times with water and ethanol respectively and dried in vacuum at 60 °C for 10 hours. Niobium-doped nickel iron hydrotalcite materials supported on nickel foam can be obtained. After calculation, the molar fraction of the niobium ions is 60% based on the total molar amount of metals in the hydrotalcite nanomaterial.

[0056] Under other unchanged conditions, replace cobalt nitrate in the above steps with nickel nitrate of the same molar amount, or a mixed salt of nickel nitrate and cobalt nitrate with the same total molar amount. Niobium ion-doped nickel iron hydrotalcite materials and niobium ion-doped nickel cobalt iron hydrotalcite materials can be respectively prepared.

[0057] Perform X-ray diffraction (XRD) on the above niobium ion-doped nickel iron hydrotalcite material. The diffraction pattern is shown in Figure 3, which is consistent with the standard card of nickel-iron hydrotalcite, indicating that there is no phase separation during the synthesis process. Then, the material was tested by scanning electron microscopy (SEM) and X-ray energy spectrometer - element distribution test (EDS-Mapping). As Figure 4 shown, the results show that the niobium ion-doped nickel-iron hydrotalcite material synthesized by the electrodeposition method has an obvious flaky morphology and uniform element distribution, proving the successful doping of niobium ions.

[0058] Example 3 - Preparation of niobium ion-doped hydrotalcite material by coprecipitation method

[0059] Prepare 60 ml of metal salt (including niobium salt) solution: Add 1.2 mmol of copper nitrate, 2 mmol of iron nitrate, 4.8 mmol of niobium chloride, and 60 ml of water to a beaker and stir evenly. (The concentration of iron salt is 0.33 mmol / L, the concentration of copper salt is 0.02 mmol / L, and the concentration of niobium salt is 0.08 mmol / L)

[0060] Prepare 60 ml of alkali salt solution: Add 12 mmol of sodium hydroxide, 4 mmol of sodium carbonate, and 60 ml of water to a beaker and stir evenly. (The concentration of sodium hydroxide is 0.5 mol / L, and the concentration of sodium carbonate is 0.0667 mol / L)

[0061] Take a beaker and fill it with 50 ml of water. Heat the water to 40 °C, and slowly drop the prepared metal salt (including niobium salt) solution and alkali salt solution into the water while stirring. Keep the solution pH = 8 during the dropping process until the metal salt solution is completely precipitated. Centrifuge the obtained solid and dry it at 80 °C. Dissolve the obtained powder with ethanol and binder, and smear it on the surface of nickel foam to obtain the niobium ion-doped hydrotalcite material. After calculation, the molar fraction of the niobium ions is 60%, based on the total molar amount of metals in the hydrotalcite nanomaterial.

[0062] Under other unchanged conditions, replace the copper nitrate in the above steps with one or several of manganese salt, chromium salt, copper salt, vanadium salt, and cobalt salt with the same total molar amount. Then, niobium ion-doped manganese (chromium, copper, vanadium, cobalt) iron hydrotalcite materials can be prepared respectively.

[0063] Under other unchanged conditions, replace the nickel foam in the above steps with carbon paper. Then, niobium ion-doped nickel-iron hydrotalcite carbon paper materials can be prepared respectively.

[0064] Application Example 1 - Oxygen evolution reaction activity test of niobium ion-doped hydrotalcite material

[0065] The electrocatalytic oxygen evolution performance of the niobium ion-doped nickel-iron hydrotalcite material obtained in Example 1 was tested using a three-electrode system: the reference electrode was a calomel electrode, the counter electrode was a platinum sheet electrode, and the working electrode was the niobium ion-doped nickel-iron hydrotalcite material of Example 1 with an effective area of 1 * 1 square centimeter. The electrolyte used was a 1 molar per liter potassium hydroxide solution. First, cyclic voltammetry scans were performed in the range of 1 - 2 V vs RHE until the electrode reached a stable state. After that, the electrolyte was replaced with a new one, and linear sweep voltammetry was performed at a rate of 2 mV / s in the range of 1 - 2 V vs RHE. The obtained linear sweep voltammogram is as Figure 5 shown.

[0066] It can be seen from Figure 5 that the overpotential of the niobium ion-doped nickel-iron hydrotalcite material of Example 1 at a current density of 10 mA cm -2 is 198 mV. This is compared with the undoped nickel-iron hydrotalcite (it can be seen from Figure 11 that the overpotential of the nickel-iron hydrotalcite electrode at a current density of 10 mA cm -2 is 247 mV). The overpotential of this application is reduced by 27 mV, and there is a very large improvement in performance. If applied to industrialization at the same time, the niobium ion-doped hydrotalcite material can save a large amount of electric power resources.

[0067] Application Example 2 - Oxygen Evolution Reaction Stability Test of Niobium Ion-Doped Hydrotalcite Material

[0068] The alkaline saline electrolysis anodic corrosion resistance stability of the niobium ion-doped hydrotalcite material electrode of Example 1 was tested using a two-electrode system: the cathode was a nickel foam electrode, and the anode was the niobium ion-doped hydrotalcite material of Example 1 with an effective area of 1 * 1 square centimeter. The electrolyte used was a 1.0 molar per liter potassium hydroxide solution, and a constant current test of 1000 mA per square centimeter was carried out. The obtained constant current curve is as Figure 6 shown. It can be seen from Figure 6 that the niobium ion-doped hydrotalcite material can operate stably for 100 h for a long time.

[0069] Application Example 3 - Oxygen Evolution Reaction Activity Test of Niobium Ion-Doped Hydrotalcite Material Obtained by Electrodeposition and Coprecipitation

[0070] The electrocatalytic oxygen evolution performance of the niobium ion-doped nickel-iron hydrotalcite material obtained in Examples 2 and 3 was tested using a three-electrode system: the reference electrode was a calomel electrode, the counter electrode was a platinum sheet electrode, and the working electrode was the niobium ion-doped nickel-iron hydrotalcite material of Example 1 with an effective area of 1 * 1 square centimeter. The electrolyte used was a 1 molar per liter potassium hydroxide solution. First, cyclic voltammetry scans were performed in the range of 1 - 2 V vs RHE until the electrode reached a stable state. After that, the electrolyte was replaced with a new one, and linear sweep voltammetry was performed at a rate of 2 mV / s in the range of 1 - 2 V vs RHE. The obtained linear sweep voltammogram is asFigure 7 As shown in Figure 7 It can be seen that the overpotentials of the niobium-doped hydrotalcite materials prepared by electrodeposition and coprecipitation are 215 mV and 227 mV respectively. The niobium-doped hydrotalcite materials prepared by electrodeposition and coprecipitation also have excellent alkaline water oxygen evolution activity.

[0071] Performance test of oxygen evolution reaction of copper ion-doped hydrotalcite material in Comparative Example 1

[0072] The method for preparing the copper ion-doped hydrotalcite material is the same as that in Example 1, except that the niobium ions are replaced by copper ions.

[0073] The electrolytic alkaline water electrocatalytic oxygen evolution performance of the copper ion-doped nickel-iron hydrotalcite material obtained in Example 1 was tested by a three-electrode system: the reference electrode was a calomel electrode, the counter electrode was a platinum sheet electrode, and the working electrode was the copper ion-doped nickel-iron hydrotalcite material of Example 1 with an effective area of 1 * 1 square centimeter. The electrolyte was 1 molar per liter potassium hydroxide solution. First, cyclic voltammetry scanning was carried out in the range of 1 - 2 V vs RHE until the electrode reached a stable state. Then, a new electrolyte was replaced, and linear scanning was performed at 2 mV / s in the range of 1 - 2 V vs RHE. The obtained linear sweep voltammogram is as Figure 8 shown. The overpotential of the copper ion-doped hydrotalcite material is 320 mV, which indicates that the oxygen evolution reaction performance of the copper ion-doped hydrotalcite material is much lower than that of the niobium ion-doped hydrotalcite material. Therefore, the particularity of niobium doping can be illustrated.

[0074] Stability test of oxygen evolution reaction of copper ion-doped hydrotalcite material in Comparative Example 2

[0075] The alkaline water electrolysis anode stability of the copper ion-doped hydrotalcite material electrode was tested by a two-electrode system: the cathode was a nickel foam electrode, the anode was a copper ion-doped nickel-iron hydrotalcite electrode with an effective area of 1 * 1 square centimeter, and the electrolyte was 1.0 molar per liter potassium hydroxide. A constant current test of 200 milliamperes per square centimeter was carried out, and the obtained constant current curve is as Figure 8 shown.

[0076] From Figure 9 it can be seen that the performance of the copper ion-doped nickel-iron hydrotalcite material decreased and voltage fluctuations occurred at 2.0 h. It shows that the stability of the copper ion-doped hydrotalcite material is much lower than that of the niobium ion-doped hydrotalcite material, which is because the doping of niobium ions can stabilize the structure of nickel-iron hydrotalcite and increase the stability of the oxygen evolution reaction.

[0077] Performance test of oxygen evolution reaction of tin ion-doped hydrotalcite material in Comparative Example 3

[0078] The method for preparing the tin ion-doped hydrotalcite material is the same as that in Example 1, except that the niobium ions are replaced by tin ions.

[0079] Electrolytic alkaline water electrocatalytic oxygen evolution performance of the copper ion-doped nickel-iron hydrotalcite material obtained in Test Example 1 of the three-electrode system: The reference electrode is a calomel electrode, the counter electrode is a platinum sheet electrode, and the working electrode is the copper ion-doped nickel-iron hydrotalcite material of Example 1 with an effective area of 1 * 1 square centimeter. The electrolyte uses a 1 molar per liter potassium hydroxide solution. First, cyclic voltammetry scanning is performed in the range of 1 - 2 V vs RHE until the electrode reaches a stable state. Then, a new electrolyte is replaced, and linear scanning is performed at 2 mV / s in the range of 1 - 2 V vs RHE. The obtained linear sweep voltammogram is as Figure 10 shown. The overpotential of the tin-doped nickel-iron hydrotalcite is 270 mV. Compared with tin ion doping, niobium ion doping has a more excellent oxygen evolution activity and is more suitable for the oxygen evolution reaction of alkaline water electrolysis.

[0080] Performance test of the oxygen evolution reaction of the undoped hydrotalcite material in Comparative Example 4

[0081] The method for preparing the hydrotalcite material is the same as that in Example 1, except that metal salts other than nickel and iron are not added.

[0082] Electrolytic alkaline water electrocatalytic oxygen evolution performance of the nickel-iron hydrotalcite material obtained in Test Example 1 of the three-electrode system: The reference electrode is a calomel electrode, the counter electrode is a platinum sheet electrode, and the working electrode is the nickel-iron hydrotalcite material with an effective area of 1 * 1 square centimeter. The electrolyte uses a 1 molar per liter potassium hydroxide solution. First, cyclic voltammetry scanning is performed in the range of 1 - 2 V vs RHE until the electrode reaches a stable state. Then, a new electrolyte is replaced, and linear scanning is performed at 2 mV / s in the range of 1 - 2 V vs RHE. The obtained linear sweep voltammogram is as Figure 11 shown. The overpotential of the nickel-iron hydrotalcite is 247 mV. It is lower than that of the niobium ion-doped hydrotalcite material (the overpotential is 198 mV).

Claims

1. A niobium ion-doped hydrotalcite nanomaterial, characterized in that, The niobium ion-doped hydrotalcite nanomaterial comprises: a conductive substrate, a hydrotalcite nanomaterial grown or coated on the surface of the conductive substrate, and niobium ions doped in the lattice of the hydrotalcite nanomaterial.

2. The hydrotalcite nanomaterial according to claim 1, characterized in that, The molar fraction of the niobium ions is 0.1%-60%, based on the total molar number of metals in the hydrotalcite nanomaterial.

3. A method for preparing the niobium ion-doped hydrotalcite nanomaterial according to claim 1, characterized in that, The synthesis method of the niobium ion-doped hydrotalcite nanomaterial is selected from one of the following: hydrothermal reaction method, electrodeposition method or coprecipitation method. Specifically: The hydrothermal reaction method comprises the following steps: adding a niobium salt, a metal salt and urea into water and dissolving them, transferring the solution to a hydrothermal reaction kettle, adding a conductive substrate and then carrying out a hydrothermal reaction; The electrodeposition method comprises the following steps: adding a niobium salt and a metal salt into water and dissolving them, placing an anode, a cathode and a reference electrode in the solution, using a conductive substrate as the cathode and carrying out electrodeposition; The coprecipitation method comprises the following steps: adding a niobium salt and a metal salt into water and dissolving them to obtain a mixed metal salt solution, adding an alkaline substance and a carbonate into water and dissolving them to obtain a dilute solution of the base, adding the mixed metal salt solution and the dilute solution of the base dropwise into water and controlling the pH within the range of 7-10 for coprecipitation, and finally mixing the obtained product with a perfluorosulfonic acid resin solution, dispersing it in an organic solvent and coating it on a conductive substrate.

4. The preparation method according to claim 3, wherein The niobium salt is one of water-soluble pentavalent niobium salts; the metal salt is one or more of water-soluble nickel salts, water-soluble cobalt salts, water-soluble iron salts, water-soluble manganese salts, water-soluble vanadium salts.

5. A method for electrocatalytic alkaline water oxygen evolution of the niobium ion-doped hydrotalcite nanomaterial according to claim 1, characterized in that, Using the niobium ion-doped hydrotalcite nanomaterial as the anode of an electrolytic reactor and bringing the electrolyte into contact with the niobium ion-doped hydrotalcite nanomaterial.

6. The method according to claim 5, characterized in that, The alkaline water contains an alkaline substance and water.

7. According to the method of claim 6, the alkaline substance is selected from one or more of sodium hydroxide and potassium hydroxide, and the total concentration of the alkaline substance is 0.01-10 moles per liter.

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