Preparation method of Ni-Fe LDH ultrathin nanosheet containing oxygen vacancy defect

Abstract

The invention discloses a preparation method of a Ni-Fe LDH ultrathin nanosheet containing an oxygen vacancy defect. The method comprises the following steps: (1) preparing the Ni-Fe LDH ultrathin nanosheet from nickel chloride, ferrous chloride, hexamethylenetetramine and lauryl sodium sulfate through a one-step hydrothermal method; and (2) etching the Ni-Fe LDH ultrathin nanosheet in a sodium borohydride solution to construct an oxygen vacancy defect so as to obtain the Ni-Fe LDH ultrathin nanosheet containing the oxygen vacancy defect. The ultrathin nanosheet provided by the invention has ultrathin thickness and abundant oxygen vacancy defects, can provide more edge active sites, and improves the reaction rate of hydrogen evolution by water electrolysis.

Description

Technical Field

[0001] The invention relates to the technical field of hydrogen production by water electrolysis, and in particular to a method for preparing a Ni-Fe LDH ultra-thin nanosheet containing oxygen vacancy defects. Background Art

[0002] As a clean and efficient new clean energy, hydrogen energy has shown great development potential due to its low environmental impact and high energy density. Electrocatalytic water splitting to produce hydrogen is a key technology for the industrialization of hydrogen energy, but its efficiency is largely limited by the activity of the catalyst. Therefore, designing efficient hydrogen evolution reaction (HER) electrocatalysts is crucial in the water splitting reaction.

[0003] Currently, commercial electrocatalysts for water electrolysis mainly include Pt, Ir, IrO 2 、RuO 2 However, these catalysts are expensive and scarce in storage, which greatly hinders their industrial application. Therefore, in order to develop low-cost, high-performance and long-life hydrogen evolution electrocatalysts, many researchers have focused on first transition metals such as nickel, iron and cobalt. Layered double hydroxides (LDH) have good application prospects in the field of electrocatalytic hydrogen production due to their low cost, good stability and flexible structure. However, LDH has limited edge active sites, resulting in low HER (electrocatalyst hydrogen evolution reaction) activity. Therefore, the use of appropriate modification methods to prepare catalysts with high HER activity is an urgent problem to be solved in the field of electrocatalytic hydrogen production. Summary of the invention

[0004] The object of the present invention is to provide a method for preparing a Ni-Fe LDH ultrathin nanosheet containing oxygen vacancy defects, which can obtain effective hydrogen evolution active sites and ultrathin sheet structures, thereby obtaining an efficient Ni-Fe LDH ultrathin nanosheet electrocatalyst containing oxygen vacancies, so as to improve the performance of Ni-Fe LDH electrocatalytic hydrogen production.

[0005] In one aspect of the present invention, the present invention provides a method for preparing a Ni-Fe LDH ultrathin nanosheet containing oxygen vacancy defects. According to an embodiment of the present invention, the method comprises the following steps:

[0006] (1) Ni-Fe LDH ultrathin nanosheets were prepared by a one-step hydrothermal method using nickel chloride, ferrous chloride, hexamethylenetetramine and sodium dodecyl sulfate;

[0007] (2) The Ni-Fe LDH ultrathin nanosheet is etched in a sodium borohydride solution to construct oxygen vacancy defects, thereby obtaining the Ni-Fe LDH ultrathin nanosheet containing oxygen vacancy defects.

[0008] In addition, the method for preparing a Ni-Fe LDH ultra-thin nanosheet containing oxygen vacancy defects according to the above embodiment of the present invention may also have the following additional technical features:

[0009] In some embodiments of the present invention, step (1) specifically includes the following steps: slowly adding a mixed solution of nickel chloride and ferrous chloride to a mixed solution of hexamethylenetetramine and sodium dodecyl sulfate, stirring until fully mixed, performing a hydrothermal reaction, centrifuging, washing, and drying to obtain Ni-Fe LDH ultrathin nanosheets.

[0010] In some embodiments of the present invention, the molar ratio of nickel chloride, ferrous chloride, hexamethylenetetramine and sodium dodecyl sulfate is (1-2):(2-1):(1-2):(1-2).

[0011] In some embodiments of the present invention, the temperature of the hydrothermal reaction is 110-120°C, the time of the hydrothermal reaction is 24-30 hours, and the temperature of the drying is 60-70°C.

[0012] In some embodiments of the present invention, step (2) specifically includes the following steps: adding the Ni-Fe LDH ultrathin nanosheets to a sodium borohydride solution for etching, and then centrifuging, washing, and drying to obtain Ni-Fe LDH ultrathin nanosheets containing oxygen vacancy defects.

[0013] In some embodiments of the present invention, the concentration of the sodium borohydride solution is 0.5-1.5 mol / L, and the mass of the Ni-Fe LDH ultrathin nanosheets added per milliliter of the sodium borohydride solution is 1-3 mg.

[0014] In some embodiments of the present invention, the etching time is 20 to 100 minutes.

[0015] In another aspect of the present invention, the present invention provides a Ni-Fe LDH ultra-thin nanosheet containing oxygen vacancy defects prepared according to the method for preparing a Ni-Fe LDH ultra-thin nanosheet containing oxygen vacancy defects.

[0016] In another aspect of the present invention, the present invention provides an application of Ni-Fe LDH ultrathin nanosheets containing oxygen vacancy defects. According to an embodiment of the present invention, the Ni-Fe LDH ultrathin nanosheets containing oxygen vacancy defects are used as electrocatalysts.

[0017] In addition, the application of the Ni-Fe LDH ultra-thin nanosheet containing oxygen vacancy defects according to the above embodiment of the present invention may also have the following additional technical features:

[0018] In some embodiments of the present invention, the Ni-Fe LDH ultrathin nanosheets containing oxygen vacancy defects are used to produce hydrogen by electrolyzing water.

[0019] Compared with the prior art, the present invention has the following beneficial effects:

[0020] 1) The Ni-Fe LDH ultrathin nanosheets containing oxygen vacancies of the present invention have a lower HER overpotential than precious metal-based catalysts. Oxygen vacancy defects are constructed on the Ni-Fe LDH ultrathin nanosheets by a simple hydrothermal method and a chemical etching method.

[0021] 2) In the present invention, dodecyl sulfate ions are used as intercalation ions to dissociate the Ni-Fe LDH flower-like structure into ultra-thin sheets, and then after etching with sodium borohydride, oxygen vacancy defects are constructed on the Ni-Fe LDH nanosheets. The structure of oxygen vacancies causes defects in the Ni-Fe LDH ultra-thin nanosheets, thereby obtaining abundant hydrogen evolution active centers.

[0022] 3) The Ni-Fe LDH ultra-thin nanosheets containing oxygen vacancy defects of the present invention have good dispersibility and a larger electrochemical active area, which is beneficial to improving the electrolysis performance of water.

[0023] 4) The Ni-Fe LDH ultra-thin nanosheets containing oxygen vacancies of the present invention are low in cost compared to precious metal-based catalysts and are harmless to the environment and human body. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 This is a morphology of the Ni-Fe LDH ultrathin nanosheet containing oxygen vacancy defects in Example 1 of the present invention;

[0025] Figure 2 This is the LSV curve of hydrogen evolution of Ni-Fe LDH ultrathin nanosheets containing oxygen vacancy defects (the electrolyte is potassium hydroxide solution, PH=14) in the application example of the present invention, and the time in the figure is the chemical etching time;

[0026] Figure 3 This is the Tafel slope curve of hydrogen evolution reaction of Ni-Fe LDH ultrathin nanosheet containing oxygen vacancy defects in the application example of the present invention, and the time in the figure is the chemical etching time;

[0027] Figure 4 This is the electrochemical active area curve of the Ni-Fe LDH ultrathin nanosheet containing oxygen vacancy defects in the application example of the present invention, and the time in the figure is the chemical etching time. DETAILED DESCRIPTION

[0028] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0029] Example 1

[0030] A method for preparing a Ni-Fe LDH ultrathin nanosheet containing oxygen vacancy defects comprises the following steps:

[0031] (1) Weigh 0.570 g of nickel chloride hexahydrate and 0.2385 g of ferrous chloride tetrahydrate and dissolve them in 50 mL of deionized water to obtain a mixed solution of nickel and iron ions, which is recorded as solution A. Weigh 0.3386 g of hexamethylenetetramine and 0.5786 g of sodium dodecyl sulfate and dissolve them in 50 mL of deionized water, which is recorded as solution B. Solution A is slowly added to solution B and stirred with a magnetic stirrer for 30 min until completely mixed.

[0032] (2) The mixed solution was transferred to a reactor for hydrothermal reaction at 120° C. for 24 h, cooled naturally, centrifuged, washed with water and ethanol several times, and then dried at 70° C. to obtain Ni-Fe LDH ultrathin nanosheets.

[0033] (3) Weigh 1.8905 g of sodium borohydride and dissolve it in 50 mL of deionized water to obtain a 1 mol / L sodium borohydride solution. Weigh 50 mg of Ni-Fe LDH ultrathin nanosheets and add them to the sodium borohydride solution. The chemical etching time is 60 min, followed by filtration, washing with water and ethanol several times, and drying at 70° C. to obtain Ni-Fe LDH ultrathin nanosheets containing oxygen vacancy defects.

[0034] like Figure 1 As shown in the high-resolution transmission electron microscope image, the prepared Ni-Fe LDH ultrathin nanosheets containing oxygen vacancy defects have an ultrathin sheet structure (thickness is about 17nm), which can increase the contact area between the catalyst and the electrolyte. In addition, the oxygen vacancy defects can expose more active sites, which helps to improve the catalytic activity of water electrolysis.

[0035] Example 2

[0036] A method for preparing Ni-Fe LDH ultrathin nanosheets containing oxygen vacancy defects, which is different from Example 1 only in that: in step (3), the chemical etching time is 20 minutes, and the other parameters and steps are the same.

[0037] Example 3

[0038] A method for preparing Ni-Fe LDH ultrathin nanosheets containing oxygen vacancy defects, which is different from Example 1 only in that: in step (3), the chemical etching time is 40 minutes, and the other parameters and steps are the same.

[0039] Example 4

[0040] A method for preparing Ni-Fe LDH ultrathin nanosheets containing oxygen vacancy defects, which is different from Example 1 only in that: in step (3), the chemical etching time is 80 minutes, and the other parameters and steps are the same.

[0041] Example 5

[0042] A method for preparing Ni-Fe LDH ultrathin nanosheets containing oxygen vacancy defects, which is different from Example 1 only in that: in step (3), the chemical etching time is 100 minutes, and the other parameters and steps are the same.

[0043] Application Examples

[0044] A method for producing hydrogen by electrolysis of water, comprising the following steps: using the Ni-Fe LDH ultrathin nanosheets containing oxygen vacancy defects prepared in Examples 1-5 as an electrocatalyst, the electrolyte being a potassium hydroxide solution with a pH of 14, a stone mill rod electrode being used as a counter electrode, an Ag / AgCl electrode being used as a reference electrode, and a current density of 10 mA / cm 2 , tested at room temperature.

[0045] like Figure 2-3 As shown, when tested at a scanning speed of 5 mV / s, the LSV overpotentials of the Ni-Fe LDH ultrathin nanosheets containing oxygen vacancy defects prepared in Examples 1-5 are 38 mV, 80 mV, 62 mV, 92 mV, and 101 mV, respectively, and the Tafel slopes are 36 mV / dec, 63 mV / dec, 85 mV / dec, 59 mV / dec, and 63 mV / dec, respectively.

[0046] like Figure 4 As shown in the figure, the electrochemical active areas of the Ni-Fe LDH ultrathin nanosheets containing oxygen vacancy defects prepared in Examples 1-5 are 7.43 mF / cm 2 、6mF / cm 2 、6.28mF / cm 2 、6.33mF / cm 2 , 5.85mF / cm 2 .

[0047] The above contents are merely examples and explanations of the present invention. Those skilled in the art may make various modifications, supplements or replace the specific embodiments described in a similar manner. As long as they do not deviate from the structure of the present invention or exceed the scope defined by the claims, they shall all fall within the protection scope of the present invention.

Claims

1. A method for preparing Ni-Fe LDH ultrathin nanosheets containing oxygen vacancy defects, characterized in that: The following steps are involved: (1) Ni-FeLDH ultrathin nanosheets were prepared by a one-step hydrothermal method using nickel chloride, ferrous chloride, hexamethylenetetramine and sodium dodecyl sulfate; (2) The Ni-Fe LDH ultrathin nanosheets are etched in a sodium borohydride solution to construct oxygen vacancy defects, thereby obtaining Ni-Fe LDH ultrathin nanosheets containing oxygen vacancy defects.

2. The method for preparing a Ni-Fe LDH ultrathin nanosheet containing oxygen vacancy defects according to claim 1, characterized in that: Step (1) specifically includes the following steps: slowly adding a mixed solution of nickel chloride and ferrous chloride to a mixed solution of hexamethylenetetramine and sodium dodecyl sulfate, stirring until fully mixed, performing a hydrothermal reaction, centrifuging, washing, and drying to obtain Ni-Fe LDH ultrathin nanosheets.

3. The method for preparing a Ni-Fe LDH ultrathin nanosheet containing oxygen vacancy defects according to claim 2, characterized in that: The molar ratio of the nickel chloride, ferrous chloride, hexamethylenetetramine and sodium dodecyl sulfate is (1-2):(2-1):(1-2):(1-2).

4. The method for preparing a Ni-Fe LDH ultrathin nanosheet containing oxygen vacancy defects according to claim 2, characterized in that: The temperature of the hydrothermal reaction is 110-120°C, the time of the hydrothermal reaction is 24-30 hours, and the temperature of the drying is 60-70°C.

5. The method for preparing a Ni-Fe LDH ultrathin nanosheet containing oxygen vacancy defects according to claim 1, characterized in that: Step (2) specifically includes the following steps: The Ni-Fe LDH ultrathin nanosheets are added into a sodium borohydride solution for etching, and then centrifuged, washed and dried to obtain Ni-Fe LDH ultrathin nanosheets containing oxygen vacancy defects.

6. The method for preparing a Ni-Fe LDH ultrathin nanosheet containing oxygen vacancy defects according to claim 5, characterized in that: The concentration of the sodium borohydride solution is 0.5-1.5 mol / L, and the mass of the Ni-Fe LDH ultra-thin nanosheets added to each milliliter of the sodium borohydride solution is 1-3 mg.

7. The method for preparing a Ni-Fe LDH ultrathin nanosheet containing oxygen vacancy defects according to claim 5, characterized in that: The etching time is 20 to 100 minutes.

8. A Ni-Fe LDH ultra-thin nanosheet containing oxygen vacancy defects prepared by the method for preparing a Ni-Fe LDH ultra-thin nanosheet containing oxygen vacancy defects according to any one of claims 1 to 7.

9. An application of the Ni-Fe LDH ultra-thin nanosheet containing oxygen vacancy defects according to claim 8, characterized in that: The Ni-Fe LDH ultrathin nanosheets containing oxygen vacancy defects are used as electrocatalysts.

10. The use of the Ni-Fe LDH ultra-thin nanosheet containing oxygen vacancy defects according to claim 9, characterized in that: The Ni-Fe LDH ultrathin nanosheet containing oxygen vacancy defects is used for electrolyzing water to produce hydrogen.

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