Preparation and application of defect-based electronegative hydroxide array electrode

Abstract

The invention relates to the technical field of nano materials and electrocatalysis, in particular to preparation and application of a defect-based electronegative hydroxide array electrode. The electronic structure of the material is regulated and controlled through anion and cation vacancy defects, the electronegative surface of the material can repel chloride ions in seawater in an electrostatic mode, so that corrosion of the chloride ions to the electrode structure in the electrolysis process is avoided, the electrochemical stability of the material is improved, meanwhile, the self-supporting hydroxide array electrode structure can effectively promote the bubble desorption process, and the electrochemical stability of the material is improved. The reaction energy consumption is reduced, the large-current seawater electrolysis performance is improved, and the electrode material is an ideal seawater electrolysis hydrogen production electrode material.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of nanomaterials and electrocatalysis, and particularly relates to a preparation process of a defect-rich negative-electricity hydroxide electrode, which can be widely applied to the field of seawater electrolysis. BACKGROUND

[0002] Under the dual pressures of global energy crisis and ecological pollution, hydrogen energy has advantages such as high combustion heat value and zero carbon emission, and has attracted widespread attention. Among them, the water electrolysis hydrogen production technology is concerned because of its green, environmental protection and pollution-free characteristics. Compared with the proton exchange membrane electrolysis technology which depends on high-purity water source, the alkaline water electrolysis hydrogen production (ALK) has low electrode material cost and high system stability, and is the mainstream water electrolysis technology in the market. However, the traditional alkaline electrolytic tank still needs to use pure water or low-salinity electrolyte (Cl - <50 ppm), which greatly limits the application expansion of the technology in coastal water-deficient areas and industrial salt-rich wastewater scenes, so the direct use of abundant salt water or industrial wastewater and other low-quality water sources for electrolysis has become an important research direction. Although in the alkaline environment, the potential difference of OER / CER can be expanded to 480 mV or more, the anodic oxidation kinetics of chloride ions is inhibited, but there are still a series of problems: on the one hand, under the high-salt electrolytic concentration, the adsorption site competition of Cl - and OH - in the alkaline medium is intensified, which leads to the decrease of the hydroxyl coverage on the catalyst surface, and causes the local chlorine precipitation side reaction, and after the adsorption of chloride ions on the electrode surface, it is easy to cause the corrosion damage of the electrode structure, which affects the stability of the electrode. On the other hand, under the industrial-grade large current density, the ion mass transfer reaction process, bubble adsorption and desorption rate and other influencing factors are intensified, which affects the electrolysis efficiency and electrolysis energy consumption. The common modification methods include electrode material component design, construction of a chlorine ion corrosion-resistant layer on the electrode surface to inhibit chlorine ion corrosion, or development of a super-hydrophilic electrode array to promote the bubble adsorption and desorption process and reduce the energy consumption of the electrolysis reaction process, but many synthesis strategies are often limited to the optimization of single performance, which pursues high activity at the expense of stability, or strengthens corrosion at the expense of reaction activity, and cannot improve the comprehensive performance, so it is very important to develop an electrode which can stably electrolyze in a seawater electrolysis system under a large current. SUMMARY

[0003] The present application provides a preparation method of a defect-based negative-electricity hydroxide array electrode, which has a simple synthesis process, and the catalytic activity and stability of the prepared material are improved, thereby effectively promoting the large-current seawater electrolysis reaction process.

[0004] A preparation method of a defect-based negative-electricity hydroxide array electrode, comprising the following steps: S1, pretreating a nickel mesh; S2, after mixing and dissolving Ni(NO3)2·6H2O, Fe(NO3)3·9H2O, Zn(NO3)2·6H2O, CO(NH2)2 and NH4F, a mixed solution is obtained; S3, the nickel mesh treated is placed in the mixed solution to perform hydrothermal reaction treatment; after the reaction is completed, the nickel mesh is taken out and placed in a NaOH solution to react; S4, the nickel mesh is taken out and placed in a sodium borohydride solution, and after the reaction is completed, a defect-based negative electric hydroxide array electrode is obtained.

[0005] Further, in S1, the specific operation of the nickel mesh pretreatment is that the nickel mesh of a predetermined size is cut, and the nickel mesh is ultrasonically washed with hydrochloric acid and deionized water, respectively.

[0006] Further, in S1, the size of the nickel mesh is 0.001-1 m 2 .

[0007] Further, in the mixed solution in S2, the concentration of Ni(NO3)2·6H2O is 3-15 mmol·L -1 , the concentration of Fe(NO3)3·9H2O is 2-10 mmol·L -1 , the concentration of Zn(NO3)2·6H2O is 1-5 mmol·L -1 , the concentration of CO(NH2)2 is 50-70 mmol·L -1 , and the concentration of NH4F is 25-35 mmol·L -1 .

[0008] Further, in S3, the temperature of the hydrothermal reaction is 120-140 ℃, and the hydrothermal reaction time is 10-15 h.

[0009] Further, in S3, the concentration of the NaOH solution is 3-6 mol·L -1 , and the reaction time of the nickel mesh placed in the NaOH solution is 10-15 h.

[0010] Further, in S4, the concentration of the sodium borohydride solution is 3-6 mol·L -1 , and the reaction temperature is 60-80 ℃.

[0011] The defect-based negative electric hydroxide array electrode prepared by the above preparation method.

[0012] The defect-based negative electric hydroxide array electrode in the application of electrolyzing seawater to produce hydrogen.

[0013] The defect-based negatively charged hydroxide array electrode prepared by this invention has excellent electrocatalytic activity and stability. Thanks to the vacancy defects of anions and cations in the material, its electrode structure exhibits a certain degree of negative charge, which can electrostatically repel chloride ions and avoid the corrosion of electrolysis by chloride ions in seawater. At the same time, the array electrode structure on the nickel mesh can promote the transport of reactants and the desorption process of bubbles, which is beneficial to the continuous and stable electrolysis of seawater under high current and effectively reduces the reaction energy consumption. Attached Figure Description

[0014] Figure 1 This is a scanning electron microscope image of the nickel-iron hydroxide array electrode of Comparative Example 1 of the present invention; Figure 2 This is an optical photograph of the distribution of bubbles on the electrode surface of the nickel-iron-hydroxide array electrode of Comparative Example 1 of the present invention after stable electrolysis for ten minutes at a certain current density. Figure 3 This is the LSV curve of the nickel-iron hydroxide array electrode of Comparative Example 1 of the present invention; Figure 4 This is a scanning electron microscope image of the defective base negatively charged hydroxide array electrode of Example 1 of the present invention; Figure 5 This is an optical photograph of the bubble distribution on the electrode surface of the defective base negatively charged hydroxide array electrode of Embodiment 1 of the present invention after stable electrolysis for ten minutes at a certain current density; Figure 6 This is a comparison diagram of the Zeta potentials of the nickel-iron hydroxide array in Comparative Example 1 and the defect-based negatively charged hydroxide array electrode in Example 1 of this invention. Figure 7 This is the LSV curve of the defective group negatively charged hydroxide array of Example 1 of the present invention; Detailed Implementation To better understand the present invention, the following embodiments further illustrate the content of the present invention, but the content of the present invention is not limited to the following embodiments.

[0015] The first aspect of this invention is the preparation method of a defect-based negatively charged hydroxide array electrode, comprising the following steps: S1: Cutting 0.001~1 m 2 Nickel meshes of different sizes were ultrasonically washed with hydrochloric acid and deionized water for a certain period of time and then removed. Subsequently, a certain amount of Ni(NO3)2·6H2O, Fe(NO3)3·9H2O, Zn(NO3)2·6H2O, CO(NH2)2, and NH4F were weighed out and dissolved in deionized water to obtain a mixed solution. The washed nickel meshes were then placed into the mixed solution.

[0016] In solution A, the concentration of Ni(NO3)2·6H2O is 3~15 mmol·L. -1 Specifically, it can be 3 mmol·L -1 5 mmol·L -1 7 mmol·L -1 9 mmol·L -1 11 mmol·L -1 13 mmol·L -1 15 mmol·L -1 .

[0017] The concentration of Fe(NO3)3·9H2O is 2~10 mmol·L -1 Specifically, it can be 2 mmol·L -1 4 mmol·L -1 6 mmol·L -1 8 mmol·L -1 10 mmol·L -1 .

[0018] The concentration of Zn(NO3)2·6H2O is 1~5 mmol·L. -1 Specifically, it can be 1 mmol·L -1 2 mmol·L -1 3 mmol·L -1 4 mmol·L -1 5 mmol·L -1 .

[0019] The concentration of CO(NH2)2 is 50~70 mmol·L. -1 Specifically, it can be 50 mmol·L -1 55 mmol·L -1 60 mmol·L -1 65 mmol·L -1 70 mmol·L -1 .

[0020] The concentration of NH4F is 25-35 mmol·L. -1 Specifically, it can be 25 mmol·L -1 30 mmol·L -1 35 mmol·L -1 .

[0021] S2. Transfer the mixed solution to a reaction vessel, and perform a hydrothermal reaction at a temperature of 120~140 ℃ for 10~15 h. S3. Subsequently, the electrode obtained above is removed and placed in NaOH solution, and subjected to hydrothermal reaction at 120-140 °C for 10-15 h; the NaOH concentration in S3 is 3-6 mol·L⁻¹. -1 Specifically, it can be 3 mol·L -1 4 mmol·L -1 5 mmol·L -1 6 mmol·L -1 ; S4. After removing the electrode obtained above, place it in 3~6 mol·L⁻¹ -1 In a sodium borohydride solution, after complete ultrasonic reaction at 60–80 °C, a defect-based negatively charged hydroxide array electrode is obtained. Specifically, the concentration of the sodium borohydride solution can be 3 mol·L⁻¹. -1 4 mmol·L -1 5 mmol·L -1 6 mmol·L -1 .

[0022] It should be noted that the size of the nickel mesh in this invention is to ensure that the nickel mesh is fully immersed in the solution, thereby ensuring uniform hydrothermal deposition of the hydroxide array on the nickel mesh. At the same time, the concentrations of Zn(NO3)2·6H2O and other reactant ions are in a certain ratio, the purpose of which is to control the number of cation vacancy defects generated in the material. The process of ultrasonication and heating after adding sodium borohydride is to control the number and uniformity of anion defect sites in the material, so that the distribution of anion and cation defects on the material surface is more uniform, and sufficient oxygen vacancies are generated in the material, further ensuring that its electronic structure and electrode surface electrical properties are fully optimized.

[0023] The second thing this invention aims to protect is the defect-based negatively charged hydroxide array electrode obtained by the above preparation method.

[0024] The third aspect of this invention is to protect the application of the aforementioned defective, negatively charged hydroxide array electrode in the electrolysis of seawater to produce hydrogen.

[0025] <Comparative Example 1> A method for preparing a nickel-iron hydroxide array electrode includes the following steps: S1: Cut 12 cm 2 Nickel meshes of different sizes were ultrasonically washed with hydrochloric acid and deionized water for a certain period of time and then removed. Subsequently, 1.2 mmol of Ni(NO3)2·6H2O, 0.6 mmol of Fe(NO3)3·9H2O, 5 mmol of CO(NH2)2, and 2.5 mmol of NH4F were weighed out and dissolved in 80 mL of deionized water to obtain a mixed solution. S2. Transfer the mixed solution to a reaction vessel, and perform a hydrothermal reaction at a temperature of 120~140 ℃ for 10~15 h to obtain a nickel-iron hydroxide array electrode.

[0026] When the nickel-iron hydroxide array electrode prepared in this comparative example was used for water electrolysis tests, it was found that... Figure 1 The electron microscope images show that the material surface exhibits a nanosheet array structure, while at 50 mA cm⁻¹ -2 After stable electrolysis for ten minutes at a current density, such as Figure 2 As shown, observation of bubbles on the electrode surface revealed a relatively large bubble size distribution, with the majority of bubbles concentrated around 60 µm. The charged behavior of the test system surface was observed to be as follows: Figure 6 As shown, its Zeta potential is 16.1 mV. The LSV curves indicate that the nickel-iron hydroxide array electrode at 400 mA cm⁻¹ exhibits good performance. -2 The overpotential at the current density is 460mV, such as Figure 3 As shown.

[0027] <Comparative Example 2> A method for preparing a nickel-iron hydroxide array electrode includes the following steps: S1, Cut 12 cm 2 Nickel meshes of different sizes were ultrasonically washed with hydrochloric acid and deionized water for a certain period of time, and then removed. Subsequently, 0.6 mmol of Ni(NO3)2·6H2O, 0.6 mmol of Fe(NO3)3·9H2O, 5 mmol of CO(NH2)2, and 2.5 mmol of NH4F were weighed out and dissolved in 80 mL of deionized water to obtain a mixed solution. S2. Transfer the mixed solution to a reaction vessel, and perform a hydrothermal reaction at a temperature of 120~140 ℃ for 10~15 h to obtain a nickel-iron hydroxide array electrode.

[0028] The nickel-iron hydroxide array electrode prepared in this comparative example was used in water electrolysis tests, and it was found that the nickel-iron hydroxide array electrode at 400 mA cm⁻¹… -2 The overpotential at the current density is 411 mV.

[0029] <Example 1> A method for preparing a defect-based negatively charged hydroxide array electrode includes the following steps: S1, Cut 12 cm 2Nickel meshes of different sizes were ultrasonically washed with hydrochloric acid and deionized water for a certain period of time, and then removed. Subsequently, 1.2 mmol of Ni(NO3)2·6H2O, 0.6 mmol of Fe(NO3)3·9H2O, 0.3 mmol of Zn(NO3)2·6H2O, 5 mmol of CO(NH2)2, and 2.5 mmol of NH4F were weighed out and dissolved in 80 mL of deionized water to obtain a mixed solution. S2. Transfer the mixed solution to a reaction vessel, and perform a hydrothermal reaction at 120 ℃ for 10 h. S3. Then, the electrode obtained above is removed and placed in a solution containing 3 mol·L⁻¹ -1 In a NaOH solution, a hydrothermal reaction was carried out at 120 °C for 10 h. S4. After removing the electrode obtained above, place it in 3 mol·L⁻¹ -1 In a sodium borohydride solution, after complete ultrasonic reaction at 60 °C, a defect-based negatively charged hydroxide array electrode is obtained.

[0030] Scanning electron microscope images of the defect-based negatively charged hydroxide array electrode material prepared in Example 1 were obtained, and the results are as follows: Figure 4 As shown in the figure, the electrode surface is a nanosheet array structure. Figure 1 In comparison, the nanosheet size of the defect-based negatively charged hydroxide array electrode material prepared in Example 1 is significantly reduced, indicating a significant increase in the exposed contact area of ​​the material. Meanwhile, as... Figure 5 As shown, the test was conducted at 50 mA cm⁻¹. -2 After the defect-based negatively charged hydroxide array electrode material prepared in Example 1 was stably electrolyzed for ten minutes at a certain current density, bubbles were observed on the electrode surface. The bubbles were found to be relatively small, concentrated around 50 µm in size, with no obvious large bubbles. Figure 6 The figure shows the Zeta potential curve of the defect-based negatively charged hydroxide array electrode material prepared in Example 1. After modification with anion vacancy defects and cation vacancy defects, the Zeta potential value of the electrode surface is -0.81 mV. Compared with the positive Zeta potential of the original nickel-iron hydroxide array electrode in Comparative Example 1, its value is negative, indicating that the electrode surface carries a negative charge, which can electrostatically repel chloride ions and further improve the stability of the material in seawater electrolysis. Figure 7 As shown, the material was tested at 400 mA cm⁻¹. -2 The electrochemical performance at the specified current density was investigated, and the overpotential of the electrode was found to be only 276 mV. Compared with the electrocatalytic material prepared in Comparative Example 1, the overpotential was reduced by 184 mV, and its seawater electrolysis performance was significantly improved.

[0031] <Example 2> S1, Cut 12 cm 2 Nickel meshes of different sizes were ultrasonically washed with hydrochloric acid and deionized water for a certain period of time, and then removed. Subsequently, 1.2 mmol of Ni(NO3)2·6H2O, 0.6 mmol of Fe(NO3)3·9H2O, 0.3 mmol of Zn(NO3)2·6H2O, 5 mmol of CO(NH2)2, and 2.5 mmol of NH4F were weighed out and dissolved in 80 mL of deionized water to obtain a mixed solution. S2. Transfer the mixed solution to a reaction vessel, and perform a hydrothermal reaction at 120 ℃ for 10 h. S3. Then, the electrode obtained above is removed and placed in a solution containing 1 mol·L⁻¹ -1 In a NaOH solution, a hydrothermal reaction was carried out at 120 °C for 10 h. S4. After removing the electrode obtained above, place it in 3 mol·L⁻¹ -1 In a sodium borohydride solution, after complete ultrasonic reaction at 60 °C, a defect-based negatively charged hydroxide array electrode is obtained.

[0032] In this embodiment, the concentration of the NaOH solution was varied, and the electrocatalytic performance of the prepared electrode was tested. It was found that the material exhibited good performance at 400 mA cm⁻¹. -2 At the given current density, the overpotential of the electrode is 284 mV. Compared to Example 1, its performance in electrolyzing brine is reduced.

[0033] <Example 3> S1, Cut 12 cm 2 Nickel meshes of different sizes were ultrasonically washed with hydrochloric acid and deionized water for a certain period of time, and then removed. Subsequently, 1.2 mmol of Ni(NO3)2·6H2O, 0.6 mmol of Fe(NO3)3·9H2O, 0.3 mmol of Zn(NO3)2·6H2O, 5 mmol of CO(NH2)2, and 2.5 mmol of NH4F were weighed out and dissolved in 80 mL of deionized water to obtain a mixed solution. S2. Transfer the mixed solution to a reaction vessel, and perform a hydrothermal reaction at 120 ℃ for 10 h. S3. Then, the electrode obtained above is removed and placed in a solution containing 3 mol·L⁻¹ -1 In a NaOH solution, a hydrothermal reaction was carried out at 120 °C for 10 h. S4. After removing the electrode obtained above, place it in 1 mol·L⁻¹ -1In a sodium borohydride solution, after complete ultrasonic reaction at 60 °C, a defect-based negatively charged hydroxide array electrode is obtained.

[0034] In this embodiment, the concentration of the sodium borohydride solution was varied, and the electrocatalytic performance of the prepared electrode was tested. It was found that the material exhibited good performance at 400 mA cm⁻¹. -2 At the given current density, the overpotential of the electrode is 294 mV. Compared to Example 1, its performance in electrolyzing brine is reduced.

[0035] <Example 4> S1, Cut 12 cm 2 Nickel meshes of different sizes were ultrasonically washed with hydrochloric acid and deionized water for a certain period of time, and then removed. Subsequently, 1.2 mmol of Ni(NO3)2·6H2O, 0.6 mmol of Fe(NO3)3·9H2O, 0.3 mmol of Zn(NO3)2·6H2O, 5 mmol of CO(NH2)2, and 2.5 mmol of NH4F were weighed out and dissolved in 80 mL of deionized water to obtain a mixed solution. S2. Transfer the mixed solution to a reaction vessel, and perform a hydrothermal reaction at 120 ℃ for 10 h. S3. Then, the electrode obtained above is removed and placed in a solution containing 3 mol·L⁻¹ -1 In a NaOH solution, a hydrothermal reaction was carried out at 120 °C for 10 h. S4. After removing the electrode obtained above, place it in 6 mol·L⁻¹ -1 In a sodium borohydride solution, after complete ultrasonic reaction at 25 °C, a defect-based negatively charged hydroxide array electrode is obtained.

[0036] In this embodiment, the concentration of sodium borohydride was varied, and the electrocatalytic performance of the prepared electrode was tested. It was found that this material exhibited excellent performance at 400 mA cm⁻¹. -2 At the given current density, the overpotential of the electrode is 301 mV. Compared to Example 1, its performance in electrolyzing brine is reduced.

[0037] Where there is no conflict, the above embodiments and features described herein can be combined with each other.

[0038] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing a defect-based negatively charged hydroxide array electrode, characterized in that, Includes the following steps: S1. Pre-treat the nickel mesh; S2. After mixing and dissolving Ni(NO3)2·6H2O, Fe(NO3)3·9H2O, Zn(NO3)2·6H2O, CO(NH2)2 and NH4F, a mixed solution is obtained. S3. Place the treated nickel mesh in the mixed solution for hydrothermal reaction treatment; After the reaction is complete, remove the nickel mesh and place it in NaOH solution to continue the reaction. S4. Remove the nickel mesh and place it in a sodium borohydride solution. After the reaction is complete, a defect-based negatively charged hydroxide array electrode is obtained.

2. The method for preparing a defect-based negatively charged hydroxide array electrode according to claim 1, characterized in that, In S1, the specific operation of nickel mesh pretreatment is as follows: cut nickel mesh to a preset size, and ultrasonically wash the nickel mesh with hydrochloric acid and deionized water respectively.

3. The method for preparing a defect-based negatively charged hydroxide array electrode according to claim 2, characterized in that, In S1, the size of the nickel mesh is 0.001~1 m. 2 .

4. The method for preparing a defect-based negatively charged hydroxide array electrode according to claim 1, characterized in that, In the mixture in S2, the concentration of Ni(NO3)2·6H2O is 3~15 mmol·L. -1 The concentration of Fe(NO3)3·9H2O is 2~10 mmol·L. -1 The concentration of Zn(NO3)2·6H2O is 1~5 mmol·L. -1 The concentration of CO(NH2)2 is 50~70 mmol·L. -1 The concentration of NH4F is 25~35 mmol·L. -1 .

5. The method for preparing a defect-based negatively charged hydroxide array electrode according to claim 1, characterized in that, In S3, the hydrothermal reaction temperature is 120~140 ℃ and the hydrothermal reaction time is 10~15 h.

6. The method for preparing a defect-based negatively charged hydroxide array electrode according to claim 1, characterized in that, In S3, the concentration of the NaOH solution is 3~6 mol·L⁻¹. -1 The reaction time of the nickel mesh in NaOH solution is 10-15 h.

7. The method for preparing a defect-based negatively charged hydroxide array electrode according to claim 1, characterized in that, In S4, the concentration of the sodium borohydride solution is 3~6 mol·L⁻¹. -1 The reaction temperature is 60~80 ℃.

8. A defect-based negatively charged hydroxide array electrode prepared by the preparation method according to any one of claims 1-7.

9. The application of the defect-based negatively charged hydroxide array electrode as described in claim 8 in the electrolysis of seawater to produce hydrogen.

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