A ferrate-modified water oxidation electrocatalyst and its preparation method and application

Abstract

The present invention provides a ferrate-modified water oxidation electrocatalyst and its preparation method and application. A carbon material is used as a matrix, nickel salt, manganese salt, urea and ferrate are added to the solution thereof, and then a ferrate-modified NiFe double metal hydroxide / carbon composite material is obtained after a hydrothermal reaction. The material is rich in iron vacancies and nickel vacancies and shows excellent electrocatalytic activity for water oxidation. By controlling the amount of ferrate, different contents of iron vacancies and nickel vacancies can be obtained, with the content of iron vacancies being 5%-40% and the content of nickel vacancies being 4%-25%. The composite catalyst also has the advantages of a simple preparation method and uniform morphology. By applying it in the field of water electrolysis, it can provide a practical approach to solving the current increasingly serious energy crisis and environmental pollution problems.

Description

Technical Field

[0001] The present invention belongs to the field of catalysts and relates to a ferrate-modified water oxidation electrocatalyst and a preparation method and application thereof, specifically to the preparation of a ferrate-modified NiFe bimetallic oxide nanomaterial and its application in water oxidation. Background Art

[0002] With the energy crisis and environmental pollution becoming increasingly severe, there is an urgent need to develop a new, clean, and sustainable energy source. Hydrogen has attracted widespread attention due to its high energy density and low environmental pollution. Currently, water electrolysis to produce hydrogen is widely researched due to its simplicity and high efficiency.

[0003] The water oxidation process in water electrolysis involves a four-electron process, resulting in slow kinetics and requiring a high overpotential to drive the reaction. The high cost and limited availability of traditional noble metal catalysts have limited their commercial development. Therefore, the key to water electrolysis technology lies in designing and constructing highly active, inexpensive, and readily available water oxidation electrocatalysts to replace traditional noble metal catalysts.

[0004] NiFe double hydroxide is currently considered one of the most competitive candidate materials for water oxidation electrocatalysts. However, due to its poor conductivity and slow mass transfer rate, the activity of NiFe LDH cannot meet commercial requirements. Summary of the Invention

[0005] The purpose of the present invention is to provide a ferrate-modified water oxidation electrocatalyst and its preparation method, wherein a NiFe double hydroxide / carbon composite material rich in iron vacancies and nickel vacancies is prepared by hydrothermal reaction, which is a ferrate-modified water oxidation electrocatalyst. 2+ and Ni 3+ The NiFe double hydroxide generates iron vacancies and nickel vacancies, and the content of iron vacancies reaches 40%, and the content of nickel vacancies reaches 25%. This is beneficial to improving the performance of the material, and the preparation method of the invention is simple and the product morphology is uniform.

[0006] Another object of the present invention is to provide a ferrate-modified water oxidation electrocatalyst for use in water oxidation electrocatalysis.

[0007] The specific technical solutions of the present invention are as follows:

[0008] A method for preparing a ferrate-modified water oxidation electrocatalyst comprises the following steps:

[0009] A. dispersing the carbon material in a solvent to form a uniform dispersion;

[0010] B. Under stirring conditions, the nickel-iron mixed solution is added dropwise to the dispersion prepared in step A, and then urea and ferrate are added to carry out a hydrothermal reaction to obtain a ferrate-modified water oxidation electrocatalyst.

[0011] The carbon material and solvent ratio in step A is 0.2-20 mg / ml;

[0012] In step A, the carbon material is dispersed in the solvent by ultrasound for 0.5-2 hours to form a uniform dispersion;

[0013] The carbon material in step A is selected from one or more of carbon black, graphene or carbon nanotubes.

[0014] The solvent in step A is a mixed solvent of water and alcohol in any proportion; it can also be pure water or pure alcohol; the alcohol is preferably methanol, ethanol or ethylene glycol; the volume ratio of water to alcohol is preferably 1:1;

[0015] The nickel-iron mixed solution prepared in step B is prepared by dissolving nickel salt and iron salt in a solvent; the total mass ratio of the nickel salt and iron salt to the solvent is 1-150 mg / mL; the molar ratio of the nickel salt to the iron salt is 2:1-25:1;

[0016] In the preparation of the nickel-iron mixed solution, the nickel salt is selected from a soluble nickel salt, preferably one or more of nickel chloride hexahydrate, nickel nitrate hexahydrate, nickel sulfate hexahydrate or nickel acetate tetrahydrate; the iron salt is a soluble iron salt, preferably manganese nitrate hexahydrate, ferric chloride hexahydrate and hydrated ferric sulfate;

[0017] In the preparation of the nickel-iron mixed solution, the solvent is a mixed solvent of water and alcohol in any proportion, which is the same as the mixed solvent described in step A.

[0018] The volume ratio of the nickel-iron mixed solution in step B to the dispersion in step A is 0.1:1-10:1;

[0019] In step B, the nickel-iron mixed solution is added drop by drop so that the metal salt can be evenly dissolved into the dispersion prepared in step A, and the prepared material is more uniform and has better performance.

[0020] The ratio of the mass of urea in step B to the total mass of the nickel and iron salts in the nickel-iron mixed solution is 1:1-100:1. The addition of urea provides a weakly alkaline environment, which allows for co-precipitation of metal ions, resulting in better LDH crystallinity and enhanced oxygen evolution activity. Substituting other alkaline sources reduces water oxidation performance, and the prepared material may not meet the requirements. LDH refers to layered double hydroxide.

[0021] In step B, the ratio of the total mass of nickel salt and iron salt in the mixed solution of ferrate and nickel iron is 1:3-1:50; the ferrate is selected from potassium ferrate or sodium ferrate; ferrate undergoes an oxidation-reduction reaction with nickel and iron, and the iron vacancy content and nickel vacancy content can be adjusted by adjusting the dosage ratio of ferrate.

[0022] The hydrothermal reaction in step B is: reacting at 80-180° C. for 4-48 hours;

[0023] In step B, after the hydrothermal reaction is completed, the precipitate is cooled and separated. The obtained precipitate is first washed with water, then washed with alcohol, and then vacuum dried at 30-60° C. to constant weight to obtain a ferrate-modified NiFe double metal hydroxide / carbon composite material, that is, a ferrite-modified water oxidation electrocatalyst.

[0024] The present invention provides a ferrate-modified water oxidation electrocatalyst, which is a ferrate-modified NiFe double metal hydroxide / carbon composite material, has a flaky structure, a size of 50nm-1000nm, and is rich in iron vacancies and nickel vacancies. By controlling the amount of ferrate used, samples with different iron vacancy contents can be obtained, and the iron vacancy content is 5%-40%; by controlling the amount of ferrate used, samples with different nickel vacancy contents can be obtained, and the nickel vacancy content is 4%-25%.

[0025] The ferrate in the present invention is inexpensive and readily available. Under hydrothermal conditions, the ferrate and the iron and nickel salts in the solution undergo an oxidation-reduction reaction, generating a large number of iron and nickel vacancies in the target material, thereby improving the conductivity of the target material and enhancing the catalytic activity of the material. The addition of a carbon material as a carrier also increases the conductivity of the material, and the two work synergistically to further enhance the conductivity of the material. The present invention uses a NiFe double hydroxide / carbon composite material modified with ferrate and containing a large number of iron and nickel vacancies as a water oxidation electrocatalyst. The iron and nickel vacancies increase the number of active sites for the oxygen evolution reaction, enhancing mass transfer, and the two work synergistically.

[0026] The present invention provides an application of a ferrate-modified water oxidation electrocatalyst for water oxidation electrocatalytic reaction.

[0027] The present invention uses carbon material as a matrix, adds nickel salt, manganese salt, urea and ferrate to the solution thereof, and then produces a ferrate-modified NiFe double hydroxide / carbon composite material after a hydrothermal reaction. The present invention needs to follow the above preparation sequence to obtain the target product; if the carbon material, nickel salt, iron salt, urea and ferrate are directly mixed in a solvent for reaction, the target product of the present application cannot be obtained. The material prepared by the present invention is rich in iron vacancies and nickel vacancies and shows excellent electrocatalytic activity for water oxidation. The present invention uses transition metal compounds as raw materials and ferrate for modification, replacing traditional precious metal catalysts, providing a cheap, easily available electrocatalyst with outstanding electrocatalytic activity for water electrolysis and water oxidation reactions. The composite catalyst also has the advantages of simple preparation method and uniform morphology. Its application in the field of water electrolysis can provide a practical idea for solving the current increasingly serious energy crisis and environmental pollution problems.

[0028] Compared with the prior art, the ferrate-modified NiFe double hydroxide / carbon composite material prepared by the present invention is simple in preparation and has a uniform morphology. The iron vacancy content can reach up to 40%, and the nickel vacancy content can reach up to 25%. The addition of carbon material can improve conductivity, and the vacancies also further increase conductivity to a certain extent. The high iron and nickel vacancy contents of the present invention increase the mass transfer rate, so that the ferrate-modified NiFe double hydroxide / carbon composite material prepared by the present invention has excellent water oxidation electrocatalytic activity. In a 1.0M KOH solution, the material reaches 10mA·cm -2 The overpotential of the catalyst is between 180-240 mV vs. RHE. In addition, due to the role of iron vacancies and nickel vacancies, the catalyst has a high overpotential at 10 mA cm compared with the NiFe double hydroxide / carbon composite material. -2 The overpotential is reduced by 20-100mV. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 This is the X-ray powder diffraction (XRD) pattern of the ferrate-modified NiFe double hydroxide / carbon black material prepared in Example 1;

[0030] Figure 2 This is a scanning electron microscope (SEM) photograph of the ferrate-modified NiFe double hydroxide / carbon black material obtained in Example 1;

[0031] Figure 3 This is the full XPS spectrum of the ferrate-modified NiFe double hydroxide / carbon black material obtained in Example 1;

[0032] Figure 4 This is the Fe high-resolution XPS pattern of the ferrate-modified NiFe double hydroxide / carbon black material obtained in Example 1;

[0033] Figure 5 This is the Ni high-resolution XPS pattern of the ferrate-modified NiFe double hydroxide / carbon black material obtained in Example 1;

[0034] Figure 6 This is a water oxidation LSV curve of the ferrate-modified NiFe double hydroxide / carbon black material obtained in Example 1;

[0035] Figure 7 This is the water oxidation LSV curve of the NiFe double hydroxide / carbon black material obtained in Example 1.

[0036] Figure 8 The water oxidation LSV curves of the ferrate-modified NiFe double hydroxide / graphene material and the NiFe double hydroxide / graphene material obtained in Example 2 are shown.

[0037] Figure 9 The water oxidation LSV curves of the ferrate-modified NiFe double hydroxide / carbon nanotube material and the NiFe double hydroxide / carbon nanotube material obtained in Example 3 are shown.

[0038] Figure 10 This is the X-ray powder diffraction (XRD) pattern of the ferrate-modified NiFe double hydroxide / carbon black material prepared in Example 4;

[0039] Figure 11 This is a water oxidation LSV curve of the ferrate-modified NiFe double hydroxide / carbon black material obtained in Example 4;

[0040] Figure 12 This is the X-ray powder diffraction XRD pattern of the ferrate-modified water oxidation electrocatalyst prepared in Example 5;

[0041] Figure 13 is an LSV curve of the ferrate-modified water oxidation electrocatalyst obtained in Example 5; DETAILED DESCRIPTION

[0042] The present invention is described in detail below with reference to the embodiments.

[0043] Example 1

[0044] A method for preparing a ferrate-modified water oxidation electrocatalyst comprises the following steps:

[0045] A. Dispersion: Weigh 5 mg of carbon black into 10 mL of a 1:1 volume ratio mixture of ethylene glycol and water, and sonicate for 1 h to disperse it evenly.

[0046] B. Preparation: Add 0.0500 g of nickel chloride hexahydrate and 0.0081 g of ferric chloride hexahydrate to 10 mL of a mixture of ethylene glycol and water (1:1 by volume) at room temperature. Then, slowly add this solution dropwise to the dispersion from step A while stirring. Then, add 150 mg of urea and 0.0080 g of potassium ferrate. Finally, heat the resulting solution to 120° C. for 10 hours.

[0047] C. Drying: The system after the reaction is cooled and separated, the precipitate is washed with water first, then with alcohol, and vacuum dried at 40°C to constant weight, i.e., the ferrate-modified NiFe double metal hydroxide / carbon black composite material ( Figure 1 and Figure 3 ), and NiFe double hydroxide is a flake structure with a diameter of about 500nm ( Figure 2 ), marked as V Fe,Ni -NiFe LDH / C, XPS test shows that NiFeLDH / C composite material contains a large number of iron vacancies and nickel vacancies, and the content of iron vacancies reaches 30%, and the content of nickel vacancies reaches 25%. Figure 4 and Figure 5 , namely, ferrate-modified water oxidation electrocatalysts.

[0048] Electrocatalytic performance test:

[0049] The V obtained in Example 1 Fe,Ni -NiFe LDH / C as a catalyst for electrocatalytic water oxidation reaction:

[0050] First, weigh a certain amount of V Fe,Ni -NiFe LDH / C nanomaterials were ultrasonically dispersed in deionized water to prepare a 4 mg / L dispersion solution. Subsequently, 6 μL of the 4 mg / L dispersion solution was dripped onto the surface of a glassy carbon electrode and allowed to dry naturally. Finally, in a 1.0 M KOH solution, an electrochemical workstation was used to record the electrocatalytic process of water oxidation in a potential window of 1.3 to 1.55 V vs. RHE. It can be seen that in a 1.0 M KOH solution, when the current density reached 10 mA cm -2 When the overpotential is only 234mV vs.RHE, see Figure 6 .

[0051] At the same time, NiFe LDH / C composite material was prepared as a comparison, and its preparation procedure was as follows

[0052] A. Dispersion: Weigh 5 mg of carbon black into 10 mL of a 1:1 volume ratio mixture of ethylene glycol and water, and disperse it evenly by ultrasonication.

[0053] B. Preparation: 0.0500 g of nickel chloride hexahydrate and 0.0190 g of ferric chloride hexahydrate were added to 10 mL of a mixture of ethylene glycol and water (1:1 by volume) at room temperature. This solution was then slowly added dropwise to the dispersion from step B under stirring, and 150 mg of urea was added. Finally, the resulting solution was heated to 120° C. for 10 hours.

[0054] C. Drying: The system after the reaction was cooled and separated, and the precipitate was first washed with water and then with alcohol, and then dried in vacuum at 40° C. to a constant weight, i.e., NiFe double hydroxide / carbon composite material (NiFe LDH / C).

[0055] The electrocatalytic performance was tested using the same method as above: in 1.0 M KOH solution, NiFe LDH / C reached a current density of 10 mA cm -2 The overpotential is 260mV vs. RHE (see Figure 7 ). In comparison, V Fe,Ni -NiFe LDH / C composite material reaches 10mA·cm -2 The overpotential of the NiFe LDH / C composite material is 26 mV smaller than that of the NiFe LDH / C composite material.

[0056] Example 2

[0057] A method for preparing a ferrate-modified water oxidation electrocatalyst comprises the following steps:

[0058] A. Dispersion: Weigh 10 mg of graphene in 10 mL of a 1:1 ethanol / water mixture and sonicate for 1 h to disperse it evenly.

[0059] B. Preparation: Add 0.0750 g of nickel nitrate hexahydrate and 0.0163 g of ferric chloride hexahydrate to 10 mL of a mixture of ethanol and water (1:1 by volume) at room temperature. Then, slowly add this solution dropwise to the dispersion from step A while stirring. Then, add 200 mg of urea and 9 mg of potassium ferrate. Finally, heat the resulting solution to 110° C. and react for 18 hours.

[0060] D. Drying: The system after the reaction was cooled and separated. The precipitate was washed with water first, then with alcohol, and dried in vacuum at 30°C to a constant weight. This is the ferrate-modified NiFe double hydroxide / graphene composite material containing iron vacancies and nickel vacancies, which is marked as V Fe,Ni -NiFe LDH / G, and the content of iron vacancies is 25%, and the content of nickel is 20%.

[0061] Electrocatalytic performance test:

[0062] The V obtained in Example 2 Fe,Ni-NiFe LDH / G as a catalyst for electrocatalytic water oxidation reaction:

[0063] First, weigh a certain amount of V Fe,Ni -NiFe LDH / G nanomaterials were ultrasonically dispersed in deionized water to prepare a 5 mg / L dispersion solution. Then, 6 μL of the 5 mg / L dispersion solution was dripped onto the surface of the glassy carbon electrode and allowed to cool naturally. Finally, an electrochemical workstation was used to record the water oxidation process in the potential window of 1.3 to 1.55 V vs. RHE. It can be seen that the obtained V Fe,Ni -NiFe LDH / G composite material has good electrocatalytic reaction. -2 , V Fe,Ni -NiFe LDH / G has an overpotential of only 220mV vs.RHE( Figure 8 ).

[0064] Under the same conditions, NiFe double hydroxide / graphene composite material (NiFe LDH / G) was prepared for comparison. The preparation procedure is as follows:

[0065] A. Dispersion: Weigh 10 mg of graphene in 10 mL of a 1:1 ethanol / water mixture and disperse it evenly by ultrasonication.

[0066] B. Preparation: 0.0750 g of nickel nitrate hexahydrate and 0.0285 g of ferric nitrate hexahydrate were added to 10 mL of a mixture of ethanol and water (1:1 by volume) at room temperature. This solution was then slowly added dropwise to the dispersion from step B while stirring, and 200 mg of urea was added. Finally, the resulting solution was heated to 110° C. for 18 hours.

[0067] C. Drying: The system after the reaction was cooled and separated, and the precipitate was first washed with water and then with alcohol, and then dried in vacuum at 30° C. to a constant weight, i.e., NiFe double hydroxide / graphene composite material (NiFe LDH / G).

[0068] The electrocatalytic performance was tested using the same method: in 1.0 M KOH solution, the NiFe LDH / C composite material reached a current density of 10 mA cm -2 The overpotential of V prepared in Example 2 is only 243mV vs. RHE. Fe,Ni -The overpotential of NiFe LDH / G composite material is reduced by 23mV( Figure 8 ).

[0069] Example 3

[0070] A method for preparing a ferrate-modified water oxidation electrocatalyst comprises the following steps:

[0071] A. Dispersion: Weigh 8 mg of carbon nanotubes into 10 mL of a 1:1 volume ratio methanol and water mixture and sonicate for 1 h.

[0072] B. Preparation: Add 0.0650 g of nickel sulfate hexahydrate and 0.0105 g of ferric sulfate monohydrate to 10 mL of a mixture of methanol and water (1:1 by volume) at room temperature. Then, slowly add this solution dropwise to the dispersion from step A while stirring. Then, add 180 mg of urea and 10 mg of potassium ferrate. Finally, heat the resulting solution to 150° C. for 24 hours.

[0073] C. Drying: The system after the reaction was cooled and separated, and the precipitate was washed with water first, then with alcohol, and dried in vacuum at 45°C to a constant weight, i.e., the ferrate-modified NiFe double hydroxide / carbon nanotube composite material containing iron vacancies and nickel vacancies, marked as V Fe,Ni -NiFe LDH / CNT, and the content of iron vacancies is 29%, and the content of nickel vacancies is 15%.

[0074] Electrocatalytic performance test:

[0075] The V obtained in Example 3 Fe,Ni -NiFe LDH / CNT as catalyst for water oxidation reaction:

[0076] First, weigh a certain amount of V Fe,Ni -NiFe LDH / CNT composite material was ultrasonically dispersed in deionized water to prepare a 4 mg / L dispersion solution; then, 6 μL of the 4 mg / L dispersion solution was dripped on the surface of the glassy carbon electrode and naturally cooled; finally, the electrochemical workstation was used to record the electrocatalytic process of water oxidation in the potential window of 1.3~1.55V vs.RHE. It can be seen that the obtained V Fe,Ni -NiFe LDH / CNT composites have excellent water oxidation activity. In 1.0M KOH solution, V Fe,Ni -NiFe LDH / CNT composite material reaches a current density of 10 mA·cm -2 The overpotential is only 180mV vs.RHE( Figure 9 ).

[0077] Under the same conditions, NiFe double hydroxide / carbon nanotube nanocomposite (NiFe LDH / CNT) was prepared as a comparison. The preparation procedure is as follows:

[0078] A. Dispersion: Weigh 8 mg of carbon nanotubes into 10 mL of a 1:1 volume ratio methanol and water mixture and disperse them evenly by ultrasonication.

[0079] B. Preparation: 0.0650 g of nickel sulfate hexahydrate and 0.0200 g of ferric sulfate monohydrate were added to 10 mL of a mixture of ethylene glycol and water (1:1 by volume) at room temperature. This solution was then slowly added dropwise to the dispersion from step B under stirring. 180 mg of urea was then added. Finally, the resulting solution was heated to 150° C. for 24 hours.

[0080] C. Drying: The system after the reaction was cooled and separated. The precipitate was washed with water first, then with alcohol, and dried under vacuum at 45°C to a constant weight, i.e., NiFe double hydroxide / carbon nanotube nanocomposite material (NiFe LDH / CNT). During the electrocatalytic process of water oxidation in 1.0 M KOH solution, NiFe LDH / CNT reached a current density of 10 mA cm -2 The overpotential is only 250mV vs.RHE. In comparison, V Fe,Ni -The electrocatalytic overpotential of NiFe LDH / CNT composite material was reduced by 70mV( Figure 9 ).

[0081] Example 4 (for comparison)

[0082] A method for preparing a ferrate-modified water oxidation electrocatalyst comprises the following steps:

[0083] A. Dispersion: Weigh 5 mg of carbon black into 10 mL of a 1:1 volume ratio mixture of ethylene glycol and water, and sonicate for 1 h to disperse it evenly.

[0084] B. Preparation: Add 0.0500 g of nickel chloride hexahydrate to 10 mL of a mixture of ethylene glycol and water (1:1 by volume) at room temperature. Then, slowly add this solution dropwise to the dispersion from step A while stirring. Then, add 150 mg of urea and 0.0080 g of potassium ferrate. Finally, heat the resulting solution to 120° C. for 10 hours.

[0085] C. Drying: The system after the reaction is cooled and separated, the precipitate is washed with water first, then with alcohol, and vacuum dried at 40°C to constant weight, i.e., the ferrate-modified NiFe double metal hydroxide / carbon black composite material ( Figure 10 ), namely, ferrate-modified water oxidation electrocatalyst (G-NiFe LDH / C).

[0086] Electrocatalytic performance test:

[0087] The G-NiFe LDH / C obtained in Example 4 was used as a catalyst for the electrocatalytic reaction of water oxidation:

[0088] First, a certain amount of G-NiFe LDH / C nanomaterials was weighed and ultrasonically dispersed in deionized water to prepare a 4 mg / L dispersion solution. Subsequently, 6 μL of the 4 mg / L dispersion solution was dripped onto the surface of a glassy carbon electrode and allowed to dry naturally. Finally, the electrocatalytic process of water oxidation was recorded in a 1.0 M KOH solution using an electrochemical workstation in a potential window of 1.3 to 1.6 V vs. RHE. It can be seen that in a 1.0 M KOH solution, when the current density reached 10 mA cm -2 When the overpotential is 357mV vs.RHE, see Figure 11 .

[0089] Example 5 (for comparison)

[0090] A method for preparing a ferrate-modified water oxidation electrocatalyst comprises the following steps:

[0091] A. Dispersion: Weigh 5 mg of carbon black into 10 mL of a 1:1 volume ratio mixture of ethylene glycol and water, and sonicate for 1 h to disperse it evenly.

[0092] B. Preparation: Add 0.0081 g of ferric chloride hexahydrate to 10 mL of a mixture of ethylene glycol and water (1:1 by volume) at room temperature. Then, slowly add this solution dropwise to the dispersion from step A while stirring. Then, add 150 mg of urea and 0.0080 g of potassium ferrate. Finally, heat the resulting solution to 120°C for 10 hours.

[0093] C. Drying: The system after the reaction was cooled and separated, and the precipitate was washed with water first, then with alcohol, and dried in vacuum at 40°C to constant weight. XRD test showed that the ferrate-modified double metal hydroxide / carbon black composite material could not be obtained in the absence of nickel salt. Figure 12 ).

[0094] Electrocatalytic performance test:

[0095] The catalyst obtained in Example 5 was used for the electrocatalytic reaction of water oxidation:

[0096] First, a certain amount of the catalyst obtained in Example 5 was weighed and ultrasonically dispersed in deionized water to prepare a 4 mg / L dispersion solution. Subsequently, 6 μL of the 4 mg / L dispersion solution was dripped onto the surface of a glassy carbon electrode and allowed to dry naturally. Finally, the electrocatalytic process of water oxidation was recorded in a 1.0 M KOH solution using an electrochemical workstation in a potential window of 1.3 to 1.7 V vs. RHE. It can be seen that in a 1.0 M KOH solution, when the current density reached 10 mA cm -2 When the overpotential is as high as 450mVvs.RHE, see Figure 13 .

Claims

1. A method for preparing a ferrate-modified water oxidation electrocatalyst, characterized in that: The preparation method comprises the following steps: A. dispersing the carbon material in a solvent to form a uniform dispersion; B. Under stirring, adding the nickel-iron mixed solution dropwise to the dispersion prepared in step A, and then adding urea and ferrate to carry out a hydrothermal reaction to obtain a ferrate-modified water oxidation electrocatalyst; In the nickel-iron mixed solution described in step B, the molar ratio of nickel salt to iron salt is 2:1-25:1; the ratio of ferrate to the total mass of nickel salt and iron salt in the nickel-iron mixed solution is 1:3-1:

50.

2. The preparation method according to claim 1, characterized in that The ratio of the carbon material to the solvent in step A is 0.2-20 mg / ml.

3. The preparation method according to claim 1 or 2, characterized in that The solvent in step A is a mixed solvent of water and alcohol in any proportion.

4. The preparation method according to claim 1, characterized in that The method for preparing the nickel-iron mixed solution in step B is: dissolving nickel salt and iron salt in a solvent; the total mass ratio of the nickel salt and iron salt to the solvent is 1-150 mg / mL.

5. The preparation method according to claim 1, characterized in that The volume ratio of the nickel-iron mixed solution in step B to the dispersion in step A is 0.1:1-10:

1.

6. The preparation method according to claim 1, characterized in that The ratio of the mass of urea in step B to the total mass of nickel salt and iron salt in the nickel-iron mixed solution is 1:1-100:

1.

7. The preparation method according to claim 1, characterized in that The hydrothermal reaction in step B is to react at 80-180° C. for 4-48 hours.

8. A ferrate-modified water oxidation electrocatalyst prepared by the preparation method according to any one of claims 1 to 7, characterized in that: The ferrate-modified water oxidation electrocatalyst is rich in iron vacancies and nickel vacancies; the content of iron vacancies is 5%-40%; the content of nickel vacancies is 4%-25%.

9. Use of a ferrate-modified water oxidation electrocatalyst prepared by the preparation method according to any one of claims 1 to 7, characterized in that: Used in water oxidation electrocatalytic reaction.

Images