A barium-modified iron oxyhydroxide and its preparation method and application

Abstract

The present invention is applicable to the technical field of electrocatalytic water decomposition, and provides a barium-modified iron oxyhydroxide, a preparation method thereof, and an application thereof. The preparation method comprises: growing a barium-modified iron oxyhydroxide nanosheet array on a metal foam substrate having a porous structure by a hydrothermal method. The specific steps comprise placing a metal foam having a large specific surface area in a polytetrafluoroethylene reactor, adding a mixed solution containing urea, ammonium fluoride, iron salt, and barium salt, and performing a hydrothermal reaction to obtain a barium-modified iron oxyhydroxide nanosheet array. The present invention utilizes a one-step hydrothermal method to grow a barium-modified iron oxyhydroxide nanosheet array on a metal foam substrate. The method is simple and efficient. Furthermore, the barium-modified iron oxyhydroxide nanosheet array is used as a neutral water oxidation electrode, which has abundant active sites and a unique electronic structure, and exhibits excellent neutral water electrolysis catalytic activity and stability.

Description

Technical Field

[0001] The present invention belongs to the technical field of electrocatalytic water decomposition, and in particular relates to a barium-modified iron oxyhydroxide and a preparation method and application thereof. Background Art

[0002] Hydrogen, with its high energy density and zero-carbon, pollution-free combustion products, is considered a promising new energy carrier for addressing the energy crisis and reducing dependence on fossil fuels. Currently, hydrogen is primarily produced industrially through natural gas steam reforming and carbon gasification reactions, which release large amounts of greenhouse gases such as CO2, exacerbating the greenhouse effect. Water electrolysis, on the other hand, not only produces high-purity hydrogen but also directly utilizes electricity generated by renewable energy. In recent years, significant progress has been made in developing high-performance non-precious metal catalysts to improve electrolyzer efficiency while controlling production costs. However, both acidic electrolyzers based on proton exchange membranes and alkaline electrolyzers based on anion exchange membranes require highly corrosive electrolytes, which not only pollute the environment but also severely damage the electrolyzer. Therefore, the development of water-splitting catalysts that operate efficiently under mild conditions is of great significance for the field of water electrolysis hydrogen production. However, progress in neutral water electrolysis has been slow, primarily due to the low concentrations of intermediate reactants in a neutral environment, which hinders the adsorption and activation of the catalysts. Therefore, rationally designing catalyst components and regulating the electronic structure of the catalyst so that it can be efficiently used in neutral water splitting technology will help achieve large-scale application of water electrolysis.

[0003] The water splitting process consists of two half-reactions: the hydrogen evolution reaction (HER) involving two-electron transfer and the oxygen evolution reaction (OER) involving four-electron transfer. Since the latter involves more electron transfers, it has a higher reaction energy barrier and is a kinetically slower process. Therefore, the development of efficient catalysts for OER will greatly promote the development of the field of water splitting. In the existing technology, some precious metal catalysts such as iridium oxide (IrO2) and ruthenium oxide (RuO2) have achieved good results in the research of neutral OER. However, the earth reserves of precious metal elements are low and the cost is high, which is not conducive to the large-scale application of water electrolysis technology. Therefore, some non-precious metal catalysts including cobalt-based, nickel-based and manganese-based catalysts have also been proposed and used in pH-neutral OER. However, these catalysts have high overpotentials (10 mA / cm 2The overpotential is higher than 350 mV at a current density of 100 mV and the stability is poor (less than 150 hours), which means it is still very far from practical application. Among non-precious metal catalysts, iron-based catalysts are considered to be a material with OER activity comparable to precious metals. However, iron-based catalysts are easy to precipitate during the neutral water decomposition reaction, resulting in extremely poor stability. This is because the catalyst has poor adsorption of water decomposition intermediates under a neutral environment, which makes the iron element easily oxidized into high-valent iron salts and then dissolved into the electrolyte. On the other hand, alkaline earth metal elements are usually used to regulate the adsorption of small molecules by the material, which has the effect of enhancing the hydrophilicity of the material. Therefore, by using alkaline earth metals to modify iron-based catalysts, the electronic structure and surface physical and chemical properties of the catalyst can be effectively adjusted, which is expected to greatly improve the neutral electrolysis activity of iron-based catalysts and promote the development of neutral electrolysis anode catalysts. Summary of the Invention

[0004] The purpose of the present invention is to provide a barium-modified iron oxyhydroxide and a preparation method and application thereof, in order to solve the problems raised in the above background technology.

[0005] To achieve the above object, the present invention provides the following technical solutions:

[0006] A method for preparing barium-modified iron oxyhydroxide comprises synthesizing a barium-modified iron oxyhydroxide nanosheet array grown on a metal foam substrate by a hydrothermal method. The iron atom content of the barium-modified iron oxyhydroxide nanosheet array is 10.59-29.33%, and the barium atom content is 0.86-3.78%.

[0007] Furthermore, the specific steps are as follows: placing the metal foam in a polytetrafluoroethylene reactor, adding urea, ammonium fluoride, iron salt, barium salt and deionized water respectively, and reacting using a hydrothermal method. The hydrothermal temperature is 100-180°C and the hydrothermal time is 4-24 hours. After the reaction is completed, it is cooled to room temperature, taken out, washed and dried in an oven to obtain a barium-modified iron hydroxide nanosheet array grown on the metal foam.

[0008] Furthermore, the thickness of the barium-modified iron oxyhydroxide nanosheet array is 5-70 nm.

[0009] Furthermore, the metal foam is any one of nickel foam, iron foam, nickel-iron foam and copper foam.

[0010] Furthermore, the concentration of the urea is 0.017-0.167 mol / L, and the concentration of the ammonium fluoride is 0.083-0.333 mol / L.

[0011] Furthermore, the iron salt is any one of Fe(NO3)3, Fe2(SO4)3 and FeCl3, and the concentration of the iron salt is 0.008-0.100 mol / L.

[0012] Furthermore, the barium salt is Ba(NO3)2 or BaCl2, and the concentration of the barium salt is 0.008-0.100 mol / L.

[0013] A barium-modified iron oxyhydroxide nanosheet array prepared according to a method.

[0014] Application of a barium-modified iron oxyhydroxide in electrocatalytic water oxidation.

[0015] Furthermore, the specific application method is: placing the barium-modified iron oxyhydroxide nanosheet array in a neutral electrolyte as an oxygen evolution electrode for neutral water oxidation reaction; the neutral electrolyte is a phosphate buffer solution, and the concentration of the neutral electrolyte is 1 mol / L.

[0016] Compared with the prior art, the present invention has the following beneficial effects:

[0017] 1. The present invention develops a one-step hydrothermal method to introduce the alkaline earth metal barium element during the growth of iron oxyhydroxide to form a barium-modified iron oxyhydroxide nanosheet array. The preparation method is simple and efficient. The nanosheet array grown on the metal foam substrate can fully expose the active sites. At the same time, the barium modification is beneficial to enhance the conductivity of the iron oxyhydroxide and improve the electron transfer ability, thereby promoting the reaction kinetics of the oxygen evolution reaction, and ultimately significantly improving the neutral water oxidation performance of the electrode.

[0018] 2. The present invention uses barium-modified iron oxyhydroxide nanosheet arrays as neutral water oxidation electrodes, which exhibits excellent catalytic activity and stability. 2 At current densities of 100 mA / cm2 and 300 mA / cm3, the OER overpotential in neutral aqueous solution is as low as 268 and 578 mV, which is much lower than that of the FeOH nanosheet array sample alone. 2 The catalysts can operate for 200 and 50 h, respectively, at a constant current density of 1.5 and 2.5, with no significant degradation in water oxidation performance. This performance is superior to most non-precious metal catalysts in the prior art. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 Scanning electron microscope (SEM) images of barium-modified iron oxyhydroxide (Ba-FeOOH) nanosheet arrays grown on nickel foam substrate after hydrothermal reaction at different magnifications.

[0020] Figure 2Scanning electron microscope (SEM) images of iron oxyhydroxide (FeOOH) nanosheet arrays grown on nickel foam substrate after hydrothermal reaction at different magnifications.

[0021] Figure 3 The transmission electron microscopy (TEM) image and energy dispersive spectroscopy (EDS) element distribution map of Fe, Ba and O elements in Ba-FeOOH.

[0022] Figure 4 In the figure, (a) is the X-ray diffraction (XRD) pattern of FeOOH and Ba-FeOOH; (b) is the Raman spectrum (Raman) comparison diagram of FeOOH and Ba-FeOOH; (c) is the Fe 2p energy level diagram of the X-ray photoelectron spectroscopy (XPS) of FeOOH and Ba-FeOOH; (d) is the Ba 3d energy level diagram of the XPS of Ba-FeOOH.

[0023] Figure 5 Comparison of the OER performance of Ba-FeOOH and other samples in a neutral electrolyte (1 mol / L phosphate buffer (PBS)). (a) Linear sweep voltammetry (LSV) curve; (b) Overpotential comparison at different current densities; (c) Tafel slope plot; (d) Electrochemical impedance spectroscopy (EIS).

[0024] Figure 6 In the figure, (a) is the voltage stability curve of FeOOH and Ba-FeOOH at low current density in neutral electrolyte (1 mol / L PBS); (b) is the voltage stability curve of Ba-FeOOH at high current density in neutral electrolyte (1 mol / L PBS). DETAILED DESCRIPTION

[0025] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0026] The specific implementation of the present invention is described in detail below with reference to specific embodiments.

[0027] A method for preparing barium-modified iron oxyhydroxide, comprising synthesizing a barium-modified iron oxyhydroxide nanosheet array grown on a metal foam substrate by a hydrothermal method, wherein the iron atom content of the barium-modified iron oxyhydroxide nanosheet array is 10.59-29.33%, the barium atom content is 0.86-3.78%, and the thickness of the barium-modified iron oxyhydroxide nanosheet array is 5-70 nm.

[0028] As an embodiment of the present invention, the specific steps are: placing metal foam in a polytetrafluoroethylene reactor, adding urea, ammonium fluoride, iron salt, barium salt and deionized water respectively, and reacting by a hydrothermal method. The hydrothermal temperature is 100-180°C and the hydrothermal time is 4-24 hours. After the reaction is completed, it is cooled to room temperature, taken out, washed and dried in an oven to obtain a barium-modified iron hydroxide nanosheet array grown on the metal foam.

[0029] As an embodiment of the present invention, the metal foam is any one of nickel foam, iron foam, nickel-iron foam and copper foam.

[0030] As an embodiment of the present invention, the concentration of urea is 0.017-0.167 mol / L, and the concentration of ammonium fluoride is 0.083-0.333 mol / L.

[0031] As an embodiment of the present invention, the iron salt is any one of Fe(NO3)3, Fe2(SO4)3 and FeCl3, and the concentration of the iron salt is 0.008-0.100 mol / L.

[0032] As an embodiment of the present invention, the barium salt is Ba(NO3)2 or BaCl2, and the concentration of the barium salt is 0.008-0.100 mol / L.

[0033] A barium-modified iron oxyhydroxide nanosheet array prepared according to a method.

[0034] A barium-modified iron oxyhydroxide is used in electrocatalytic water oxidation. The specific application method is to place the barium-modified iron oxyhydroxide nanosheet array in a neutral electrolyte, which is a phosphate buffer solution with a concentration of 1 mol / L, as an oxygen evolution electrode for neutral water oxidation.

[0035] In an embodiment of the present invention, preferably, a barium-modified iron oxyhydroxide nanosheet array is placed in a neutral three-electrode system as an oxygen evolution electrode, a carbon rod as a counter electrode, a calomel electrode as a reference electrode, the electrolyte is 0.355 mol / L potassium dihydrogen phosphate and 0.645 mol / L potassium hydrogen phosphate, the solution pH is 7, and a neutral water oxidation reaction performance test is performed.

[0036] Example 1: This embodiment of the present invention provides a method for preparing a barium-modified iron oxyhydroxide nanosheet array. The steps of the method are as follows:

[0037] A 2 cm x 5 cm nickel foam was placed in a 3 mol / L hydrochloric acid solution, followed by anhydrous ethanol and deionized water, and ultrasonicated for 15 minutes. The cleaned nickel foam was then placed in a 60 mL solution containing 0.033 mmol / L Fe(NO₃)₃, 0.033 mmol / L Ba(NO₃)₂, 0.1 mmol / L urea, and 0.167 mmol / L ammonium fluoride. The reaction was carried out hydrothermally at 140°C for 5 hours. After the reaction was complete and cooled to room temperature, the catalyst was repeatedly rinsed with anhydrous ethanol and deionized water and then dried in an oven at 60°C for 5 hours, resulting in a barium-modified iron oxyhydroxide nanosheet array catalyst (denoted as "Ba-FeOOH") grown on the nickel foam.

[0038] The present invention provides an application of a barium-modified iron oxyhydroxide nanosheet array. The specific application steps are as follows: the prepared barium-modified iron oxyhydroxide nanosheet array is used as a working electrode, a calomel electrode is used as a reference electrode, and a graphite rod electrode is used as a counter electrode to form a three-electrode system. The system is placed in a neutral electrolyte to test its water oxidation performance. The electrolyte is 1 mol / L phosphate buffer. The sample is tested at 10 and 300 mA / cm 2 The overpotentials for neutral water oxidation at current densities of are shown in Table 1.

[0039] Figure 1 and Figure 2 These are SEM images of the prepared Ba-FeOOH and FeOOH catalysts. The catalysts were observed on a JEOL JSM-7900 with an electron beam intensity of 12.6 keV. Both exhibit a nanosheet array morphology, with the Ba-FeOOH nanosheets ranging in thickness from 5 to 70 nm. This is because the Ba modification makes the FeOOH sheets more uniform and dense.

[0040] Figure 3 This is the EDS elemental distribution of the prepared Ba-FeOOH catalyst. The catalyst morphology was observed on a JEOL 2100F and the elemental distribution was investigated using energy dispersive spectroscopy (EDS) on a QUANTAX 200-TEM. Fe, Ba, and O are uniformly distributed throughout the nanosheets, successfully demonstrating the formation of FeOOH and the incorporation of Ba into the nanosheets.

[0041] Figure 4(a) is the XRD pattern of the prepared FeOOH and Ba-FeOOH catalysts. The specific steps are as follows: the prepared catalysts were collected on X'Pert PRO. It can be seen that the characteristic peaks on the XRD pattern are similar to those of Ni (PDF#4-850), FeOOH (PDF#01-0662) and Ba-FeO x (PDF#28-0141), indicating the successful synthesis of iron oxyhydroxide and the successful incorporation of Ba. Figure 4 (b) Comparison of Raman spectra of FeOOH and Ba-FeOOH. The Raman spectra were acquired on a HORIBA LabRAM at a laser wavelength of 532 nm. Both samples exhibit characteristic peaks characteristic of FeOOH. However, after Ba modification, Ba-FeOOH exhibits a characteristic Ba-O peak, indicating successful Ba incorporation. Figure 4 (c) shows the comparison of Fe 2p energy level spectra of FeOOH and Ba-FeOOH by XPS. It can be found that after Ba modification, the Fe 3+ The peak shifts to higher energy, representing the increase in Fe valence. Figure 4 (d) Shows the Ba 3d energy level spectrum comparison of Ba-FeOOH from the XPS spectra. The 3d splitting peak spacing of Ba is 15.3 eV, indicating a +2 oxidation state. The XPS spectra were acquired on an ESCALAB 250XI (Thermo) system.

[0042] Figure 5 (a) and Figure 5 (b) shows the linear sweep voltammetry (LSV) curves of FeOOH, Ba-FeOOH, and IrO2 samples in 1 mol / L phosphate buffer solution and a detailed comparison of the OER overpotentials. It can be found that the introduction of Ba significantly improves the OER performance of FeOOH at 10 and 300 mA / cm, respectively. 2 At current densities of 1000 nm and 1000 nm, the required OER overpotential is only as low as 268 and 578 mV, which is much better than that of IrO2 samples. The Tafel slopes of these samples are further calculated, as shown in Figure 2. Figure 5 As shown in (c), the Ba-FeOOH sample has a low Tafel slope of 128 mV / dec, indicating that Ba modification is beneficial to promote faster OER reaction kinetics. At the same time, Ba modification is also beneficial to improve the conductivity of FeOOH, thereby promoting rapid electron transfer on the catalyst, as shown in Figure 5 (d) The electrochemical impedance spectroscopy shows that Ba-FeOOH has a smaller charge transfer resistance.

[0043] Figure 6(a) Shows the FeOOH and Ba-FeOOH samples in 1 mol / L PBS solution at 10 mA / cm 2 Comparison of stability under current density. It can be found that the introduction of Ba greatly improves the stability of FeOOH. 2 At a current density of 1.5 GHz, the Ba-FeOOH sample can operate stably for 200 h, while the performance of the FeOOH sample gradually decays within 40 h. Figure 6 (b) shows the Ba-FeOOH sample in 1 mol / L PBS solution at 300 mA / cm 2 Stability under current density. At 300 mA / cm 2 At a high current density, the Ba-FeOOH sample can operate stably for more than 50 h, demonstrating its excellent stability.

[0044] Example 2: This embodiment of the present invention provides a method for preparing a barium-modified iron oxyhydroxide nanosheet array. The steps of the method are as follows:

[0045] A 2 cm x 5 cm iron foam was placed in a 3 mol / L hydrochloric acid solution, followed by anhydrous ethanol and deionized water, and ultrasonicated for 15 minutes. The cleaned iron foam was then placed in a 60 mL solution containing 0.008 mmol / L Fe(NO₃)₃, 0.067 mmol / L BaCl₂, 0.167 mmol / L urea, and 0.333 mmol / L ammonium fluoride. The reaction was carried out hydrothermally at 120°C for 5 hours. After the reaction was complete and cooled to room temperature, the catalyst was repeatedly rinsed with anhydrous ethanol and deionized water and then dried in an oven at 60°C for 5 hours to obtain a barium-modified iron oxyhydroxide nanosheet array catalyst grown on the iron foam.

[0046] The present invention provides an application of a barium-modified iron oxyhydroxide nanosheet array. The specific application steps are as follows: the prepared barium-modified iron oxyhydroxide nanosheet array is used as a working electrode, a calomel electrode is used as a reference electrode, and a graphite rod electrode is used as a counter electrode to form a three-electrode system and placed in a neutral electrolyte to test its water oxidation performance. The electrolyte is 1 mol / L phosphate buffer. The sample is tested at 10 and 300 mA / cm 2 The overpotentials for neutral water oxidation at current densities of are shown in Table 1.

[0047] Example 3: This embodiment of the present invention provides a method for preparing a barium-modified iron oxyhydroxide nanosheet array. The steps of the method are as follows:

[0048] A 2 cm x 5 cm nickel foam was placed in a 3 mol / L hydrochloric acid solution, followed by anhydrous ethanol and deionized water, and ultrasonicated for 15 minutes. The cleaned nickel foam was then placed in a 60 mL solution containing 0.017 mmol / L Fe2(SO4)3, 0.008 mmol / L Ba(NO3)2, 0.017 mmol / L urea, and 0.083 mmol / L ammonium fluoride. The reaction was carried out hydrothermally at 100°C for 12 hours. After the reaction was complete and cooled to room temperature, the catalyst was repeatedly rinsed with anhydrous ethanol and deionized water and then dried in an oven at 60°C for 5 hours to obtain a barium-modified iron oxyhydroxide nanosheet array catalyst grown on the nickel foam.

[0049] The present invention provides an application of a barium-modified iron oxyhydroxide nanosheet array. The specific application steps are as follows: the prepared barium-modified iron oxyhydroxide nanosheet array is used as a working electrode, a calomel electrode is used as a reference electrode, and a graphite rod electrode is used as a counter electrode to form a three-electrode system and placed in a neutral electrolyte to test its water oxidation performance. The electrolyte is 1 mol / L phosphate buffer. The sample is tested at 10 and 300 mA / cm 2 The overpotentials for neutral water oxidation at current densities of are shown in Table 1.

[0050] Example 4: This embodiment of the present invention provides a method for preparing a barium-modified iron oxyhydroxide nanosheet array. The steps of the method are as follows:

[0051] A 4 cm x 10 cm nickel-iron foam was placed in a 3 mol / L hydrochloric acid solution, followed by anhydrous ethanol and deionized water, and ultrasonicated for 15 minutes. The cleaned nickel-iron foam was then placed in a 60 mL solution containing 0.100 mmol / L FeCl₃, 0.033 mmol / L BaCl₂, 0.067 mmol / L urea, and 0.250 mmol / L ammonium fluoride. The reaction was carried out hydrothermally at 180°C for 4 hours. After the reaction was complete and cooled to room temperature, the catalyst was repeatedly rinsed with anhydrous ethanol and deionized water and then dried in an oven at 60°C for 5 hours to obtain a barium-modified iron oxyhydroxide nanosheet array catalyst grown on the nickel-iron foam.

[0052] The present invention provides an application of a barium-modified iron oxyhydroxide nanosheet array. The specific application steps are as follows: the prepared barium-modified iron oxyhydroxide nanosheet array is used as a working electrode, a calomel electrode is used as a reference electrode, and a graphite rod electrode is used as a counter electrode to form a three-electrode system and placed in a neutral electrolyte to test its water oxidation performance. The electrolyte is 1 mol / L phosphate buffer. The sample is tested at 10 and 300 mA / cm 2The overpotentials for neutral water oxidation at current densities of are shown in Table 1.

[0053] Example 5: This embodiment of the present invention provides a method for preparing a barium-modified iron oxyhydroxide nanosheet array. The steps of the method are as follows:

[0054] A 3 cm x 7.5 cm nickel foam was placed in a 3 mol / L hydrochloric acid solution, anhydrous ethanol, and deionized water, followed by ultrasonic treatment for 15 minutes. The cleaned nickel foam was then placed in a 60 mL solution containing 0.033 mmol / L Fe(NO₃)₃, 0.100 mmol / L BaCl₂, 0.050 mmol / L urea, and 0.133 mmol / L ammonium fluoride. The reaction was carried out hydrothermally at 100°C for 16 hours. After the reaction was complete and cooled to room temperature, the catalyst was repeatedly rinsed with anhydrous ethanol and deionized water and then dried in an oven at 60°C for 5 hours to obtain a barium-modified iron oxyhydroxide nanosheet array catalyst grown on the nickel foam.

[0055] The present invention provides an application of a barium-modified iron oxyhydroxide nanosheet array. The specific application steps are as follows: the prepared barium-modified iron oxyhydroxide nanosheet array is used as a working electrode, a calomel electrode is used as a reference electrode, and a graphite rod electrode is used as a counter electrode to form a three-electrode system and placed in a neutral electrolyte to test its water oxidation performance. The electrolyte is 1 mol / L phosphate buffer. The sample is tested at 10 and 300 mA / cm 2 The overpotentials for neutral water oxidation at current densities of are shown in Table 1.

[0056] Example 6: This embodiment of the present invention provides a method for preparing a barium-modified iron oxyhydroxide nanosheet array. The steps of the method are as follows:

[0057] A 2 cm x 5 cm copper foam was placed in a 3 mol / L hydrochloric acid solution, followed by anhydrous ethanol and deionized water, and ultrasonicated for 15 minutes. The cleaned copper foam was then placed in a 60 mL solution containing 0.067 mmol / L FeCl₃, 0.017 mmol / L Ba(NO₃)₂, 0.133 mmol / L urea, and 0.333 mmol / L ammonium fluoride. The reaction was carried out hydrothermally at 160°C for 8 hours. After the reaction was complete and cooled to room temperature, the catalyst was repeatedly rinsed with anhydrous ethanol and deionized water and then dried in an oven at 60°C for 5 hours to obtain a barium-modified iron oxyhydroxide nanosheet array catalyst grown on the copper foam.

[0058] The present invention provides an application of a barium-modified iron oxyhydroxide nanosheet array. The specific application steps are as follows: the prepared barium-modified iron oxyhydroxide nanosheet array is used as a working electrode, a calomel electrode is used as a reference electrode, and a graphite rod electrode is used as a counter electrode to form a three-electrode system and placed in a neutral electrolyte to test its water oxidation performance. The electrolyte is 1 mol / L phosphate buffer. The sample is tested at 10 and 300 mA / cm 2 The overpotentials for neutral water oxidation at current densities of are shown in Table 1.

[0059] Table 1 Summary of neutral water oxidation performance of Ba-FeOOH samples prepared in different examples

[0060]

[0061] In summary, the present invention develops a simple and efficient one-step hydrothermal method to introduce the alkaline earth metal barium during the growth of iron oxyhydroxide to form barium-modified iron oxyhydroxide nanosheet arrays. The nanosheet arrays grown on a metal foam substrate fully expose active sites. Furthermore, the barium modification enhances the conductivity of the iron oxyhydroxide and improves electron transfer, thereby promoting the reaction kinetics of the oxygen evolution reaction (OER), ultimately significantly improving the neutral water oxidation performance of the electrode.

[0062] Ba-modified iron oxyhydroxide nanosheet arrays as neutral water oxidation electrodes exhibited excellent catalytic activity and stability at 10 and 300 mA / cm 2 At current densities of 100 mA / cm2 and 300 mA / cm3, the OER overpotential in neutral aqueous solution is as low as 268 and 578 mV, which is much lower than that of the FeOH nanosheet array sample alone. 2 The catalysts can operate for 200 and 50 h, respectively, at a constant current density of 1.5 and 2.5, with no significant degradation in water oxidation performance. This performance is superior to most non-precious metal catalysts in the prior art.

[0063] The above are only preferred embodiments of the present invention. It should be pointed out that for those skilled in the art, several variations and improvements can be made without departing from the concept of the present invention. These should also be regarded as the scope of protection of the present invention. These will not affect the effect of the implementation of the present invention and the practicality of the patent.

Claims

1. A method for preparing barium-modified iron oxyhydroxide, characterized in that: The following steps are involved: The metal foam is placed in a polytetrafluoroethylene reactor, and urea, ammonium fluoride, iron salt, barium salt and deionized water are added respectively. The reaction is carried out by a hydrothermal method at a hydrothermal temperature of 100-180°C and a hydrothermal time of 4-24 hours. After the reaction is completed, the metal foam is cooled to room temperature, washed and dried in an oven to obtain a barium-modified iron oxyhydroxide nanosheet array grown on the metal foam substrate. The metal foam is any one of nickel foam, iron foam, nickel-iron foam and copper foam; The concentration of the urea is 0.017-0.167 mol / L, and the concentration of the ammonium fluoride is 0.083-0.333 mol / L; The iron salt is any one of Fe(NO3)3, Fe2(SO4)3 and FeCl3, and the concentration of the iron salt is 0.008-0.100 mol / L; The barium salt is Ba(NO3)2 or BaCl2, and the concentration of the barium salt is 0.008-0.100 mol / L; In the barium-modified iron oxyhydroxide nanosheet arrays, the iron atom content is 10.59-29.33% and the barium atom content is 0.86-3.78%.

2. The preparation method according to claim 1, characterized in that The thickness of the barium-modified iron oxyhydroxide nanosheet array is 5-70 nm.

3. A barium-modified iron oxyhydroxide nanosheet array prepared according to the preparation method of claim 1 or 2.

4. Use of the barium-modified iron oxyhydroxide nanosheet array according to claim 3 in an electrocatalytic water oxidation reaction.

5. The use according to claim 4, characterized in that The specific application method is: placing the barium-modified iron oxyhydroxide nanosheet array in a neutral electrolyte as an oxygen evolution electrode for neutral water oxidation reaction; the neutral electrolyte is a phosphate buffer solution, and the concentration of the neutral electrolyte is 1 mol / L.

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