A method for preparing highly efficient self-supporting oxygen evolution electrocatalysts using cation exchange.
A nickel-iron double hydroxide oxygen evolution electrocatalyst was prepared on carbon cloth by cation exchange, which solved the problems of insufficient conductivity and active sites of nickel-iron double hydroxide and achieved high efficiency and low cost oxygen evolution reaction performance.
Patent Information
- Application Number
- CN202310184564.4
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- Filing Date
- 2023-03-01
- Publication Date
- 2025-10-28
- Estimated Expiration
- 2043-03-01
AI Technical Summary
Existing nickel-iron double hydroxides have poor conductivity and few active sites, which affects their catalytic performance as oxygen evolution electrocatalysts.
A highly efficient self-supporting oxygen evolution electrocatalyst was prepared by cation exchange. A nickel-copper double hydroxide precursor was prepared by hydrothermal method and grown on carbon cloth. Then, it was soaked in ferric chloride solution in a chemical bath to form nickel-iron double hydroxide. The Fe3+ and Cu2+ ion exchange reaction was carried out at room temperature to form a rough porous structure.
The catalyst exhibits improved conductivity and active sites, reduced preparation costs, and demonstrates high catalytic activity and stability in alkaline environments. It also exhibits low overpotential, with values of 253 mV and 302 mV at current densities of 10 mA/cm² and 100 mA/cm², respectively, and the overpotential remains almost unchanged over 24 hours.
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Figure CN116180138B_ABST
Abstract
Description
Technical Field
[0001] This invention relates to a method for preparing an oxygen evolution electrocatalyst. Background Technology
[0002] Hydrogen energy, as an ideal new energy source, has broad application prospects. However, its high production cost limits its further development. Therefore, reducing the cost of hydrogen production is crucial. Electrolysis of water is an ideal method for hydrogen production, as water is abundant and the process is clean and pollution-free. Its main cost lies in the high electricity consumption; therefore, reducing the voltage required for water splitting is critical. The water splitting reaction can be divided into hydrogen evolution and oxygen evolution. Both half-reactions affect the efficiency of hydrogen evolution. The oxygen evolution process at the anode involves four electron / proton coupling reactions, which are kinetically slow, thus affecting the overall splitting efficiency. Therefore, the preparation of highly active oxygen evolution electrocatalysts is a key research focus in the field of water splitting.
[0003] Nickel-iron-based electrocatalysts exhibit good intrinsic catalytic activity, especially nickel-iron double hydroxides, which have shown a strong trend in recent years to replace noble metal catalysts as commercial oxygen evolution catalyst electrodes. However, the poor conductivity and limited number of active sites of nickel-iron double hydroxides mean that their catalytic performance still lags behind that of noble metal catalysts represented by Ru and Ir. Conventional hydrothermal methods for preparing nickel-iron double hydroxides cannot solve these problems. Summary of the Invention
[0004] This invention aims to address the problems of poor conductivity and limited active sites in existing nickel-iron double hydroxides, and provides a method for preparing highly efficient self-supporting oxygen evolution electrocatalysts using cation exchange.
[0005] A method for preparing a highly efficient self-supporting oxygen evolution electrocatalyst using cation exchange comprises the following steps:
[0006] I. Preparation of precursors using a hydrothermal method:
[0007] ① Dissolve nickel nitrate hexahydrate, copper nitrate trihydrate, ammonium fluoride and urea in deionized water and stir at room temperature to obtain a mixed solution;
[0008] The molar ratio of nickel nitrate hexahydrate to copper nitrate trihydrate is 1:(0.4-1); the molar ratio of nickel nitrate hexahydrate to ammonium fluoride is 1:(3-5); the molar ratio of nickel nitrate hexahydrate to urea is 1:(8-10).
[0009] ② The carbon cloth is immersed in the mixed solution and then placed in a high-pressure reactor for high-temperature reaction;
[0010] ③ After the reaction is complete, wait for the high-pressure reactor to cool to room temperature, remove the carbon cloth, clean and dry it to obtain the nickel-copper double hydroxide precursor grown on the carbon cloth;
[0011] II. Chemical bath soaking of precursors:
[0012] At room temperature, the nickel-copper double hydroxide precursor grown on carbon cloth was immersed in ferric chloride solution. After immersion, the carbon cloth was removed, cleaned, and dried to obtain a highly efficient self-supporting oxygen evolution electrocatalyst.
[0013] The beneficial effects of this invention are:
[0014] First, the raw materials used in this invention are abundant in nature and readily available, which can effectively reduce the preparation cost of electrocatalysts.
[0015] II. The preparation process of this invention is simple and controllable, with mild reaction conditions, and utilizes Fe. 3+ Ions and Cu 2+ The cation exchange reaction between ions can occur at room temperature without requiring additional energy input. Given the widespread nature of cation exchange reactions, this preparation method has a degree of universality and can be applied to other transition metal hydroxides.
[0016] Third, the nickel-iron double hydroxide obtained in this invention is a self-supporting electrode grown on a carbon cloth substrate, eliminating the need for additional binders. Furthermore, the chemical bath process yields a rough, porous structure; the rough surface improves catalyst wettability, and the porous nanosheets have a large specific surface area, increasing active sites. During the oxygen evolution reaction in an alkaline environment, the current density is 10 mA / cm². 2 and 100mA / cm 2 At that time, the overpotentials were 253mV and 302mV, respectively. Simultaneously, within 24 hours, at a current density of 10mA / cm²... 2 Under these conditions, the overpotential of the oxygen evolution reaction in the sample remains almost unchanged. Attached Figure Description
[0017] Figure 1 This is a scanning electron microscope image of the nickel-copper double hydroxide precursor prepared in step 1③ of Example 1 and grown on carbon cloth.
[0018] Figure 2 This is a scanning electron microscope image of the highly efficient self-supporting oxygen evolution electrocatalyst prepared in step two of Example 1;
[0019] Figure 3 This is a TEM image of the highly efficient self-supporting oxygen evolution electrocatalyst prepared in step two of Example 1;
[0020] Figure 4The X-ray diffraction pattern of the highly efficient self-supporting oxygen evolution electrocatalyst prepared in step two of Example 1 is shown below.
[0021] Figure 5 The image shows the oxygen evolution polarization curve of the highly efficient self-supporting oxygen evolution electrocatalyst prepared in step two of Example 1. Detailed Implementation
[0022] Specific Implementation Method 1: This implementation method describes a method for preparing a highly efficient self-supporting oxygen evolution electrocatalyst using a cation exchange method, which is carried out according to the following steps:
[0023] I. Preparation of precursors using a hydrothermal method:
[0024] ① Dissolve nickel nitrate hexahydrate, copper nitrate trihydrate, ammonium fluoride and urea in deionized water and stir at room temperature to obtain a mixed solution;
[0025] The molar ratio of nickel nitrate hexahydrate to copper nitrate trihydrate is 1:(0.4-1); the molar ratio of nickel nitrate hexahydrate to ammonium fluoride is 1:(3-5); the molar ratio of nickel nitrate hexahydrate to urea is 1:(8-10).
[0026] ② The carbon cloth is immersed in the mixed solution and then placed in a high-pressure reactor for high-temperature reaction;
[0027] ③ After the reaction is complete, wait for the high-pressure reactor to cool to room temperature, remove the carbon cloth, clean and dry it to obtain the nickel-copper double hydroxide precursor grown on the carbon cloth;
[0028] II. Chemical bath soaking of precursors:
[0029] At room temperature, the nickel-copper double hydroxide precursor grown on carbon cloth was immersed in ferric chloride solution. After immersion, the carbon cloth was removed, cleaned, and dried to obtain a highly efficient self-supporting oxygen evolution electrocatalyst.
[0030] The beneficial effects of this specific implementation method are:
[0031] I. The raw materials used in this embodiment are abundant in nature and easy to obtain, which can effectively reduce the preparation cost of electrocatalysts.
[0032] II. The preparation process of this embodiment is simple and controllable, with mild reaction conditions, and utilizes Fe 3+ Ions and Cu 2+ The cation exchange reaction between ions can occur at room temperature without requiring additional energy input. Given the widespread nature of cation exchange reactions, this preparation method has a degree of universality and can be applied to other transition metal hydroxides.
[0033] Third, the nickel-iron double hydroxide obtained in this embodiment is a self-supporting electrode grown on a carbon cloth substrate, eliminating the need for additional binders. Furthermore, the chemical bath process yields a rough, porous structure; the rough surface improves catalyst wettability, and the porous nanosheets have a large specific surface area, increasing active sites. During the oxygen evolution reaction in an alkaline environment, the current density is 10 mA / cm². 2 and 100mA / cm 2 At that time, the overpotentials were 253mV and 302mV, respectively. Simultaneously, within 24 hours, at a current density of 10mA / cm²... 2 Under these conditions, the overpotential of the oxygen evolution reaction in the sample remains almost unchanged.
[0034] Specific Implementation Method Two: This implementation method differs from Specific Implementation Method One in that the total molar ratio of nickel nitrate hexahydrate, copper nitrate trihydrate, ammonium fluoride, and urea in step one ① to the volume ratio of deionized water is 1 mmol:(1-5) mL. Everything else is the same as in Specific Implementation Method One.
[0035] Specific Implementation Method Three: This implementation method differs from Specific Implementation Method One or Two in that the high-temperature reaction described in step one, ②, is specifically carried out at a reaction temperature of 120℃~150℃ for 4h~10h. Everything else is the same as in Specific Implementation Method One or Two.
[0036] Specific Implementation Method Four: This implementation method differs from Specific Implementation Methods One to Three in that the carbon cloth size mentioned in step one, step two, is 1cm × 1cm to 2cm × 4cm. Everything else is the same as in Specific Implementation Methods One to Three.
[0037] Specific Implementation Method Five: This implementation method differs from Specific Implementation Methods One to Four in that, in step two, the nickel-copper double hydroxide precursor grown on carbon cloth is immersed in ferric chloride solution for 8 to 10 hours at room temperature. Everything else is the same as in Specific Implementation Methods One to Four.
[0038] Specific Implementation Method Six: This implementation method differs from Specific Implementation Methods One to Five in that the concentration of the ferric chloride solution mentioned in step two is 6 mmol / L to 8 mmol / L. Everything else is the same as in Specific Implementation Methods One to Five.
[0039] Specific Implementation Method Seven: This implementation method differs from Specific Implementation Methods One to Six in that: the cleaning and drying described in Step One ③ and Step Two specifically involves cleaning with deionized water and ethanol for 0.5 min to 2 min respectively, followed by drying at room temperature for 20 h to 24 h. Everything else is the same as in Specific Implementation Methods One to Six.
[0040] Specific Implementation Method Eight: This implementation method differs from Specific Implementation Methods One to Seven in that: the molar ratio of nickel nitrate hexahydrate to copper nitrate trihydrate in step 1① is 1:0.5; the molar ratio of nickel nitrate hexahydrate to ammonium fluoride in step 1① is 1:4; and the molar ratio of nickel nitrate hexahydrate to urea in step 1① is 1:10. Everything else is the same as in Specific Implementation Methods One to Seven.
[0041] Specific Implementation Method Nine: This implementation method differs from Specific Implementation Methods One to Eight in that: in step one ②, the reaction is carried out at a reaction temperature of 120°C for 6 hours. Everything else is the same as in Specific Implementation Methods One to Eight.
[0042] Specific Implementation Method Ten: This implementation method differs from Specific Implementation Methods One to Nine in that the concentration of the ferric chloride solution mentioned in step two is 8 mmol / L. Everything else is the same as in Specific Implementation Methods One to Nine.
[0043] The beneficial effects of the present invention are verified using the following embodiments:
[0044] Example 1:
[0045] A method for preparing a highly efficient self-supporting oxygen evolution electrocatalyst using cation exchange comprises the following steps:
[0046] I. Preparation of precursors using a hydrothermal method:
[0047] ① Dissolve nickel nitrate hexahydrate, copper nitrate trihydrate, ammonium fluoride and urea in deionized water and stir at room temperature to obtain a mixed solution;
[0048] The molar ratio of nickel nitrate hexahydrate to copper nitrate trihydrate is 1:0.5; the molar ratio of nickel nitrate hexahydrate to ammonium fluoride is 1:4; the molar ratio of nickel nitrate hexahydrate to urea is 1:10; and the total molar number of nickel nitrate hexahydrate, copper nitrate trihydrate, ammonium fluoride, and urea to the volume ratio of deionized water is 1 mmol:3 mL.
[0049] ② The carbon cloth is immersed in the mixed solution and then placed in a high-pressure reactor. The reaction is carried out for 6 hours at a reaction temperature of 120℃.
[0050] ③ After the reaction is complete, wait for the high-pressure reactor to cool to room temperature, remove the carbon cloth, clean and dry it to obtain the nickel-copper double hydroxide precursor grown on the carbon cloth;
[0051] II. Chemical bath soaking of precursors:
[0052] At room temperature, the nickel-copper double hydroxide precursor grown on carbon cloth was immersed in ferric chloride solution for 8 hours. After immersion, the carbon cloth was removed, cleaned and dried to obtain a highly efficient self-supporting oxygen evolution electrocatalyst.
[0053] The concentration of the ferric chloride solution is 8 mmol / L.
[0054] The carbon cloth mentioned in step 1② has a size of 2cm × 2cm.
[0055] The cleaning and drying described in Step 1③ and Step 2 specifically involves cleaning with deionized water and ethanol for 1 minute each, followed by drying at room temperature for 24 hours.
[0056] Figure 1 The image shows a scanning electron microscope (SEM) image of the nickel-copper double hydroxide precursor prepared in step 1③ of Example 1, which is grown on carbon cloth. As can be seen from the image, the prepared nickel-copper double hydroxide precursor has a nanosheet structure, and the nanosheets (approximately 40 nm to 80 nm thick) have a smooth and flat surface.
[0057] Figure 2 The image shows a scanning electron microscope (SEM) image of the highly efficient self-supporting oxygen evolution electrocatalyst prepared in step two of Example 1. As can be seen from the image, the nickel-iron double hydroxide nanosheets are rougher and more porous compared to the precursor surface.
[0058] Figure 3 The image shows a TEM image of the highly efficient self-supporting oxygen evolution electrocatalyst prepared in step two of Example 1; as can be seen from the image, there are multiple small nanopores on the surface of the nanosheets.
[0059] Figure 4 The image shows the X-ray diffraction pattern of the highly efficient self-supporting oxygen evolution electrocatalyst prepared in step two of Example 1; as can be seen from the image, the nanosheet phase is FeNiCl(OH)4·xH2O.
[0060] Using a three-electrode testing system, in an electrolyte of 1 mol / L KOH solution, at a current density of 10 mA / cm², 2 and 100mA / cm 2 Under the specified conditions, the highly efficient self-supporting oxygen evolution electrocatalyst prepared in step two of Example 1 was subjected to an oxygen evolution reaction.
[0061] Figure 5 The figure shows the oxygen evolution polarization curve of the highly efficient self-supporting oxygen evolution electrocatalyst prepared in step two of Example 1; as can be seen from the figure, the current density is 10 mA / cm². 2 and 100mA / cm 2 At that time, the overpotentials were 253mV and 302mV, respectively.
[0062] Meanwhile, within 24 hours, at a current density of 10 mA / cm² 2 Under these conditions, the overpotential remains almost unchanged, increasing by only 8 mV. Compared to existing nickel-iron double hydroxide catalytic electrodes, the material prepared in Example 1 exhibits high catalytic activity and catalytic stability.
Claims
1. A method for preparing a highly efficient self-supporting oxygen evolution electrocatalyst using cation exchange, characterized in that... It is done in the following steps: I. Preparation of precursors using a hydrothermal method: ① Dissolve nickel nitrate hexahydrate, copper nitrate trihydrate, ammonium fluoride and urea in deionized water and stir at room temperature to obtain a mixed solution; The molar ratio of nickel nitrate hexahydrate to copper nitrate trihydrate is 1:0.5; the molar ratio of nickel nitrate hexahydrate to ammonium fluoride is 1:(3~5); the molar ratio of nickel nitrate hexahydrate to urea is 1:(8~10). The total molar ratio of nickel nitrate hexahydrate, copper nitrate trihydrate, ammonium fluoride, and urea to the volume of deionized water is 1 mmol: (3~5) mL. ②Immerse the carbon cloth in the mixed solution, then place it in a high-pressure reactor and react for 4 to 10 hours at a reaction temperature of 120℃~150℃. ③ After the reaction is complete, wait for the high-pressure reactor to cool to room temperature, remove the carbon cloth, clean and dry it to obtain the nickel-copper double hydroxide precursor grown on the carbon cloth; II. Chemical bath soaking of precursors: At room temperature, the nickel-copper double hydroxide precursor grown on carbon cloth was immersed in ferric chloride solution for 8-10 hours. After immersion, the carbon cloth was removed, cleaned and dried to obtain a highly efficient self-supporting oxygen evolution electrocatalyst. The concentration of the ferric chloride solution is 6 mmol / L to 8 mmol / L; the highly efficient self-supporting oxygen evolution electrocatalyst is a nickel-iron double hydroxide nanosheet grown on carbon cloth, and the phase of the nanosheet is FeNiCl(OH)4·xH2O.
2. The method for preparing a highly efficient self-supporting oxygen evolution electrocatalyst using cation exchange according to claim 1, characterized in that... The carbon cloth mentioned in step 1② has a size of 1cm×1cm~2cm×4cm.
3. The method for preparing a highly efficient self-supporting oxygen evolution electrocatalyst using cation exchange according to claim 1, characterized in that... The cleaning and drying described in Step 1③ and Step 2 specifically involves cleaning with deionized water and ethanol for 0.5 min to 2 min respectively, followed by drying at room temperature for 20 h to 24 h.
4. The method for preparing a highly efficient self-supporting oxygen evolution electrocatalyst using cation exchange according to claim 1, characterized in that... The molar ratio of nickel nitrate hexahydrate to copper nitrate trihydrate in step 1① is 1:0.5; the molar ratio of nickel nitrate hexahydrate to ammonium fluoride in step 1① is 1:4; and the molar ratio of nickel nitrate hexahydrate to urea in step 1① is 1:
10.
5. The method for preparing a highly efficient self-supporting oxygen evolution electrocatalyst using cation exchange according to claim 4, characterized in that... In step 1②, the reaction is carried out at a temperature of 120℃ for 6 hours.
6. The method for preparing a highly efficient self-supporting oxygen evolution electrocatalyst using cation exchange according to claim 1, characterized in that... The concentration of the ferric chloride solution mentioned in step two is 8 mmol / L.