Preparation method and application of low-crystalline ni-fe ldh three-dimensional nanosheet array catalyst

Abstract

The application discloses a preparation method and application of a low-crystallinity NiFe LDH three-dimensional nanosheet array catalyst, and the preparation method comprises the following steps: removing surface impurities and an oxidation layer of a nickel foil by using a strong acid, ultrapure water and anhydrous ethanol; and placing the treated nickel foil in an electrolyte composed of 1-20 mmol of FeSO4, 1-10 mmol of H3BO3 and saturated KCl aqueous solution, and preparing the low-crystallinity NiFe LDH three-dimensional nanosheet array catalyst by a pulse electrodeposition method. The pulse electrodeposition method is used to prepare NiFe LDH-B / NF amorphous / crystalline nanosheets with excellent OER performance by taking the nickel foil as a skeleton instead of a nickel foam. The method can promote the electrocatalytic performance of a thin film material and overcome the problem that the traditional ultrasonic wave has no significant influence on the oxygen evolution performance.

Description

Technical Field

[0001] This invention belongs to the field of electrocatalysis technology, and particularly relates to the preparation method and application of a low-crystallinity NiFe LDH three-dimensional nanosheet array catalyst. This catalyst has good acoustic response and OER activity, and is a non-precious metal catalyst that can be used to assist in the electrolysis of water for oxygen evolution. Background Technology

[0002] With the widespread adoption of renewable energy globally, the need to store unstable energy sources as stable chemical energy (such as hydrogen) is becoming increasingly urgent. Renewable energy-driven water electrolysis technology is a crucial pathway to achieving sustainable hydrogen production. However, water electrolysis requires an additional overpotential to overcome the activation energy barrier, leading to energy loss. Currently, many electrolyzers rely on precious metal electrodes and lack efficient catalysts to reduce the overpotential. In particular, the oxygen evolution reaction (OER) at the anode has slower kinetics compared to the hydrogen evolution reaction (HER) at the cathode, becoming a major bottleneck limiting cell efficiency. Therefore, developing high-performance, highly stable anode electrocatalysts is crucial for improving water electrolysis efficiency.

[0003] Superior electrocatalysts can significantly reduce the activation overpotential required for electrocatalysis, while introducing ultrasound can compensate for ohmic losses caused by kinetic overpotentials in the system. The application of ultrasound in water electrolysis mainly optimizes reaction kinetics and mass transfer processes through its physical effects (such as cavitation and acoustic flow), thereby improving HER and OER efficiencies. Typically, ultrasound is emitted by a generator and then transmitted to the electrolytic cell through a medium such as water to interfere with the electrocatalyst's electrolysis of water. Due to the need to consider the loss of ultrasound during propagation, the ultrasonic power used is usually relatively high, and prolonged radiation on the electrocatalyst can damage its lifespan. Therefore, it is necessary to improve the device for applying ultrasound to address the issue of ultrasonic power loss and lifespan, and further enhance the performance of ultrasound-assisted water electrolysis. Summary of the Invention

[0004] To address the shortcomings of existing technologies, the technical problem to be solved by this invention is to provide a method for preparing and applying a low-crystallinity NiFeLDH three-dimensional nanosheet array catalyst, thereby solving the problem of the lack of catalysts with both good ultrasonic effect and excellent OER activity in existing technologies, as well as the problems of insignificant oxygen evolution effect of traditional acoustic wave-assisted electrocatalysis and the damage to catalyst stability caused by traditional acoustic wave devices.

[0005] The technical solution adopted by the present invention to solve the aforementioned technical problem is as follows:

[0006] In a first aspect, the present invention provides a method for preparing a low-crystallinity NiFe LDH three-dimensional nanosheet array catalyst, wherein the preparation method comprises: removing surface impurities and oxide layers from nickel foil using strong acid, ultrapure water, and anhydrous ethanol, respectively; placing the treated nickel foil in an electrolyte composed of 1-20 mmol FeSO4, 1-10 mmol H3BO3, and a saturated KCl aqueous solution, and preparing the low-crystallinity NiFe LDH three-dimensional nanosheet array catalyst by pulse electrodeposition.

[0007] Furthermore, the specific process of the preparation method is as follows:

[0008] S1. Place 1-100μm nickel foil in a strong acid solution of 1-3M H ions and sonicate to remove any possible NiOx layer on its surface. Then rinse with ultrapure water and ethanol, and dry with dry analytical grade argon gas.

[0009] S2. Add 1-20 mmol of FeSO4 and 1-10 mmol of H3BO3 to 50 mL of saturated KCl aqueous solution and stir until homogeneous to obtain electrolyte;

[0010] S3. Electrochemical treatment is performed using pulse deposition, employing a dual-electrode system. Both electrodes are nickel foils pretreated in step S1, placed parallel to each other with a spacing of 1.5-3 cm. The electrolyte described in step S2 is used. The pulse current density applied in the pulse electrodeposition method is ±10~100 mA / cm². 2 The pulse frequency is 0–20 Hz, and the pulse period is 0–1000.

[0011] S4. After the electrochemical treatment is completed, the electrode is removed from the electrolyte, rinsed with ultrapure water and anhydrous ethanol, and dried in a vacuum oven at 50-70°C for 8-16 hours to obtain a low-crystallinity NiFe LDH three-dimensional nanosheet array catalyst.

[0012] Further, in step S1, the nickel foil thickness is 8-20 μm, and the strong acid is: an H2SO4 solution with a concentration of 0.8-1.2 mol / L or a 1-3 M HCl solution; in step S2, the FeSO4 concentration is 1-5 mmol, and the H3BO3 concentration is 1-3 mmol.

[0013] In step S3, the applied pulse current density is ±30~60mA / cm². 2 The pulse frequency is 4–8 Hz, and the pulse period is 500–800.

[0014] Secondly, the present invention provides a low-crystallinity NiFe LDH three-dimensional nanosheet array catalyst obtained by the preparation method described above. The microstructure of the catalyst is composed of a large number of wrinkled nanosheets, with crystalline and amorphous regions inside the nanosheets.

[0015] Furthermore, Fe, Ni, O, and B elements are uniformly dispersed on the surface of the catalyst nanosheets.

[0016] Thirdly, the present invention provides an application of the catalyst described in claim 4, using a low-crystallinity NiFe LDH three-dimensional nanosheet array catalyst as the working electrode in electrocatalytic oxygen evolution. The low-crystallinity NiFe LDH three-dimensional nanosheet array catalyst is designated as NiFe LDH-B / NF, and the specific application process is as follows:

[0017] One side of the NiFe LDH-B / NF is the bonding surface, and the other side is the testing surface. Use AB glue to bond the bonding surface of NiFe LDH-B / NF to the substrate of the interdigital electrode, 1.5-3mm away from the photolithography pattern on the interdigital electrode. Use a scraper to remove excess AB glue and let it dry for 2.5-5 hours.

[0018] Subsequently, the electrolytic cell was bonded to the interdigitated electrode with AB glue. The electrolytic cell covered the working electrode. The inside of the electrolytic cell was divided into a working electrode coverage area and a substrate area. Then it was dried overnight to obtain an in-situ mixed acoustic electrolytic cell.

[0019] Prepare a 1.0M potassium hydroxide solution as the electrolyte for electrocatalysis, and introduce nitrogen gas into the in-situ mixed acoustic electrolysis cell to drive out the air;

[0020] Using NiFe LDH-B / NF as the working electrode, graphite as the counter electrode, and a saturated calomel electrode as the reference electrode, the electrocatalytic oxygen evolution reaction was carried out in an electrocatalytic electrolyte by connecting to an electrochemical workstation.

[0021] Connect the RF source to the signal amplifier and connect a 50-ohm resistor, then connect the interdigital electrodes; supply the signal amplifier with a DC power supply of 32V; during the electrocatalytic oxygen evolution test, the RF source, through the signal amplifier, causes the interdigital electrodes to convert an RF signal with a frequency of 5-15MHz and a level of 0-108dBm into an acoustic signal to assist in oxygen evolution and test its overpotential.

[0022] Furthermore, the substrate of the interdigitated electrode is a lithium niobate single crystal. The photolithographic pattern converts the electrical signal into an acoustic signal. The acoustic wave is transmitted through the lithium niobate single crystal on the substrate and propagates to the working electrode adhered to the single crystal. At the same time, the single crystal not covered by the working electrode propagates the acoustic wave into the electrolyte. The oxygen evolution performance of the electrocatalyst is promoted in the form of bulk acoustic waves and surface acoustic waves.

[0023] Furthermore, without surface ultrasonication, the working electrode operates at a current density of 20 mA·cm⁻¹. -2 The overpotential is 294 mV; under surface ultrasonic conditions, NiFe LDH-B / NF at a current density of 20 mA·cm⁻¹ -2 The overpotential was 237 mV; ultrasound reduced the overpotential of NiFe LDH-B from 294 mV to 237 mV at 20 mA cm⁻¹. -2 The Tafel slope decreased by 66 mV·dec -1 Ultrasonic waves can increase the current density at 500mV by at least two times.

[0024] Fourthly, the present invention provides an in-situ mixing acoustic electrolysis system, characterized in that the system comprises:

[0025] Radio frequency source: Transmits an RF signal with a frequency of 5-15MHz and a level of 0-9dBm;

[0026] DC power supply: Provides 32V DC power to the signal amplifier;

[0027] Signal amplifier: Used to amplify the strength of RF signals from a radio frequency source;

[0028] Interdigitated electrodes: including a single-crystal piezoelectric substrate of 28.0mm×47.0mm×0.5mm, on which a comb-shaped transducer electrode pattern is photolithographically etched to convert electrical signals into acoustic signals;

[0029] Electrolytic cell: a regular square prism made of glass, with the top and bottom faces unsealed;

[0030] Assembly: First, attach the working electrode to the outside of the pattern on the interdigitated electrode using AB glue. Then, cover the working electrode with the electrolytic cell, and attach the bottom of the electrolytic cell to the substrate of the interdigitated electrode using AB glue. The working electrode is not completely covered inside the electrolytic cell, and some areas of the substrate are exposed. Next, connect the RF source and the signal amplifier using a BNC-N port adapter cable, and then connect the signal amplifier to the interdigitated electrode using an N port-electrode clip. Then, connect the signal amplifier to a DC power supply, so that the transmitted electrical signal from the RF source is amplified by the signal amplifier and converted into an acoustic signal by the interdigitated electrode. Finally, add KOH solution to the electrolytic cell, insert the counter electrode and the reference electrode, and then connect to the electrochemical workstation to perform relevant tests.

[0031] Furthermore, the dimensions of the electrolytic cell in the system are 13.0 mm × 13 mm × 24.5 mm × 1 cm.

[0032] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0033] (1) In this invention, NiFe LDH-B / NF amorphous / crystalline nanosheets with excellent OER performance were prepared by using nickel foil as a skeleton instead of nickel foam by pulse electrodeposition.

[0034] (2) The in-situ mixed acoustic electrolysis cell of the present invention can promote the electrocatalytic performance of thin film materials and overcome the problem that traditional ultrasound has little effect on oxygen evolution performance.

[0035] (3) Surface acoustic waves can reduce the oxygen evolution overpotential of NiFe LDH-B / NF by up to 57 mV and increase the current density at 500 mV by a full 2.1 times, demonstrating excellent acoustic response performance. Surface acoustic waves significantly enhance the oxygen evolution performance of NiFe LDH-B / NF, far exceeding the effect of traditional ultrasound on oxygen evolution performance.

[0036] (4) The overpotential in water splitting is mainly caused by activation, ohmic, and concentration overpotentials. Although the activation and ohmic overpotentials can be reduced by optimizing the catalyst, thereby improving OER performance, the improvement of HER and OER performance also leads to the accumulation and increase of bubbles on the electrode. The high content of bubbles in the solution hinders the transport of electrolyte and increases the solution resistance. The accumulation of bubbles on the electrode acts as an insulating barrier, disrupting the electrolysis process. The catalyst prepared in this invention and its application can effectively weaken the ohmic and concentration overpotentials caused by bubbles. While effectively removing hydrogen bubbles and improving hydrogen evolution performance, it can also have a beneficial effect on oxygen evolution reaction without destroying the stability of the catalyst and significantly reducing the overpotential.

[0037] (5) The self-supporting working electrode prepared by this invention has excellent OER activity, and the surface acoustic wave (SAW) enhances OER much more effectively than traditional ultrasound, without heating the electrolyte and causing less damage to the material itself. In addition, the SAW device is easier to characterize in situ than the traditional ultrasound device, which facilitates the study of the microscopic mechanism of acoustic wave-assisted water electrolysis. Attached Figure Description

[0038] Figure 1 This is a physical image of an in-situ mixed acoustic electrolysis cell.

[0039] Figure 2 Linear sweep voltammetry curves of oxygen evolution reaction in water electrolysis with and without 10MHz acoustic wave assisted by nickel foils of different thicknesses.

[0040] Figure 3 Figures show the characterization results of NiFe LDH-B, where (a)-(b) are TEM images of NiFe LDH-B; and (c) are the elemental distribution map and electron diffraction pattern of NiFe LDH-B obtained from energy dispersive X-ray spectroscopy (EDX).

[0041] Figure 4The figures show the oxygen evolution performance test results for different samples, where (a) is the LSV curve, (b) is the Tafel slope, (c) is the EIS plot, and (d) is the double electric layer C. dl picture.

[0042] Figure 5 The figures show the oxygen evolution performance test results of different samples with and without ultrasound, where (a) is the LSV curve, (b) is the Tafel slope, (c) is the EIS plot, and (d) is the double electric layer C. dl picture.

[0043] Figure 6 This is a schematic diagram of the simulation structure of the in-situ mixed acoustic electrolysis system in this invention.

[0044] Figure 7 This is a physical diagram of the in-situ mixing acoustic electrolysis system of the present invention. Detailed Implementation

[0045] The present invention will be described in detail below with reference to the accompanying drawings and embodiments. The advantages and implementation methods of the present invention will become more apparent. The contents shown in the accompanying drawings are only for explanation and illustration of the present invention and do not constitute any limitation on the present invention.

[0046] This invention discloses a method for preparing a low-crystallinity NiFe LDH three-dimensional nanosheet array catalyst. The method involves removing surface impurities and oxide layers from nickel foils of a certain area and different thicknesses using strong acids (H₂O ion concentration 1–3 M), ultrapure water, and anhydrous ethanol, respectively. The strong acids can be H₂SO₄ solutions with a concentration of 0.8–1.2 mol / L, 1–3 M HCl solutions, etc. The treated nickel foils are then placed in an electrolyte composed of 1–20 mmol FeSO₄, 40 mM (mMol / mL) H₃BO₃, and a saturated KCl aqueous solution. Low-crystallinity NiFe LDH-B / NF is then prepared by pulse electrodeposition.

[0047] NiFe LDH-B / NF was used as the working electrode and bonded to the interdigitated electrode with AB glue at a distance of 1.5-3 mm from the photolithographic pattern. Excess AB glue was removed with a scraper, and the electrode was allowed to dry for 3 hours. Subsequently, the electrolytic cell was bonded to the interdigitated electrode with AB glue, covering the working electrode. The working electrode area remaining inside the electrolytic cell was 1 cm². 2 Then it was dried overnight to obtain an in-situ mixed acoustic electrolytic cell.

[0048] The specific preparation and application process is as follows:

[0049] I. Preparation process

[0050] S1. Place a 1-100μm nickel foil (with a test side and an adhesive side) in a 1-3M HCl solution and sonicate for 10 minutes to remove any NiOx layer that may be present on its surface. Then rinse with ultrapure water and ethanol, and dry with dry analytical grade argon gas.

[0051] S2. Add 1-20 mmol of FeSO4 and 1-10 mmol of H3BO3 to 50 mL of saturated KCl aqueous solution and stir until homogeneous to obtain electrolyte;

[0052] S3. Electrochemical treatment is carried out in a two-electrode system, where both electrodes are pre-cleaned nickel foils, placed parallel to each other and spaced approximately 1.5-3 cm apart. The pulsed current density applied in the pulsed electrodeposition method is ±10–100 mA / cm². 2 The pulse frequency is 0–20 Hz, and the pulse period is 0–1000.

[0053] S4. After the electrochemical treatment is completed, the electrode is removed from the electrolyte, rinsed with ultrapure water and anhydrous ethanol, and dried in a vacuum oven at 60°C for 8–16 hours to obtain a low-crystallinity NiFe LDH three-dimensional nanosheet array catalyst.

[0054] Preferably, in step S1, a nickel foil with a thickness of 10 μm is selected, ultrasonically treated in a 3 mol / L HCl solution for 10 minutes, and rinsed three times with water and ethanol in sequence.

[0055] In step S2, 1 mmol of FeSO4 and 2 mmol of H3BO3 are added to a saturated KCl aqueous solution and stirred for 5 min to obtain a homogeneous electrolyte.

[0056] In step S3, the applied pulse current density is ±50 mA / cm². 2 The pulse frequency is 5 Hz, and the pulse period is 750.

[0057] In step S4, the product is dried in a vacuum drying oven for 8 hours.

[0058] II. Application Process of Acoustic Wave-Assisted Electrocatalytic Oxygen Evolution

[0059] F1. Mix A glue and B glue in a mass ratio of 3:1 and stir until evenly mixed;

[0060] F2. The prepared low-crystallinity NiFe LDH three-dimensional nanosheet array catalyst is bonded to the interdigitated electrode with AB glue. At a distance of 1.5-3 mm from the photolithography pattern on the interdigitated electrode, excess AB glue is scraped off with a scraper and dried for 3 hours.

[0061] F3. Next, use AB glue to attach the electrolytic cell to the interdigitated electrodes, completely enclosing the working electrode inside the electrolytic cell, with some space exposed on the substrate of the interdigitated electrodes. The area of ​​the working electrode remaining inside the electrolytic cell is 1 cm². 2 Then it was dried overnight to obtain an in-situ mixed acoustic electrolytic cell.

[0062] F4. Prepare a 1.0M potassium hydroxide solution as the electrolyte for electrocatalysis, and purge the air with nitrogen gas.

[0063] F5. Using NiFe LDH-B / NF as the working electrode, graphite as the counter electrode, and a saturated calomel electrode as the reference electrode, the electrocatalytic oxygen evolution reaction was carried out in the electrolyte by connecting to an electrochemical workstation.

[0064] F6. Connect the RF source to the signal amplifier, and then connect a 50-ohm resistor, followed by the interdigital electrodes. Supply the signal amplifier with a 32V DC power supply. During the electrocatalytic oxygen evolution test, the RF source, through the signal amplifier, causes the interdigital electrodes to convert an RF signal with a frequency of 5-15MHz and a level of 0-108dBm into an acoustic signal to assist in oxygen evolution and test its overpotential.

[0065] Example 1

[0066] First, a 10 μm nickel foil was ultrasonically treated in a 3M HCl solution for 10 minutes, followed by rinsing with ultrapure water and ethanol, and then drying with analytical grade argon gas. A 50 mL electroplating solution was prepared, consisting of 20 mM FeSO4, 40 mM H3BO3, and a saturated KCl aqueous solution. Electrochemical treatment was performed in a two-electrode system, where both electrodes were pre-cleaned nickel foils, each with an area of ​​1 x 1 cm². 2 The two electrodes are placed horizontally and parallel to each other, with a distance of about 3 centimeters between them.

[0067] The applied pulse current density in the experiment was ±50 mA / cm². 2 The pulse frequency is 5 Hz, and the pulse period is 750. After electrochemical treatment, the electrode is removed from the electrolyte, rinsed with ultrapure water and ethanol, and dried in a vacuum chamber for 8 hours. A and B adhesives are mixed in a 3:1 mass ratio and stirred thoroughly. Nickel foil is adhered to the interdigitated electrode using AB adhesive, 3 mm away from the photolithographic pattern. Excess AB adhesive is scraped off with a scraper, and the electrode is dried for 3 hours. Subsequently, the electrolytic cell is adhered to the interdigitated electrode using AB adhesive, leaving a working electrode area of ​​1 cm² inside the electrolytic cell. 2 Then it was dried overnight to obtain an in-situ acoustic electrochemical cell.

[0068] In this embodiment, the substrate of the interdigitated electrode is a lithium niobate single crystal. The photolithographic pattern can convert electrical signals into acoustic signals. The acoustic waves are transmitted by the lithium niobate single crystal on the substrate and propagate to the nickel foil adhered to the single crystal. At the same time, the single crystal not covered by the nickel foil can propagate the acoustic waves into the electrolyte. The oxygen evolution performance of the electrocatalyst is promoted in the form of bulk acoustic waves (within the nickel foil) and surface acoustic waves (on the surface in contact with the electrolyte).

[0069] application

[0070] A 1.0 M potassium hydroxide solution was prepared as the electrolyte for electrocatalysis, and nitrogen gas was introduced to purge the air. NiFe LDH-B / NF was used as the working electrode, graphite as the counter electrode, and a saturated calomel electrode as the reference electrode. The system was connected to an electrochemical workstation, and the electrocatalytic oxygen evolution reaction was carried out in the electrolyte.

[0071] Without surface ultrasonication, the working electrode operates at a current density of 20 mA·cm⁻¹. -2 The overpotential is 294mV.

[0072] Subsequently, the RF source was connected to the signal amplifier, and a 50-ohm resistor was connected in between, followed by the interdigital electrode. During the electrocatalytic oxygen evolution test, the interdigital electrode converted a 10MHz RF signal with a 60dBm level into an acoustic signal. The NiFe LDH-B / NF was then subjected to a current density of 20mA·cm⁻¹. -2 The overpotential is 237mV.

[0073] Under the same test conditions, if nickel foam of the same thickness is used as the carrier of the working electrode, the attenuation of ultrasound is relatively strong, and it cannot play a role in reducing overpotential in the electrocatalytic oxygen evolution test.

[0074] from Figure 3 TEM images revealed that the microstructure of NiFe LDH-B / NF consisted of numerous wrinkled nanosheets, containing both crystalline regions (with a lattice spacing of 0.216 nm) and amorphous regions. Furthermore, elemental mapping analysis of the NiFe-LDH-B nanosheets showed that Fe, Ni, O, and B elements were uniformly dispersed on their surface.

[0075] This application can reduce overpotential at higher current densities, and the catalyst has high ultrasonic responsiveness, which is greatly enhanced with the assistance of ultrasound.

[0076] Comparative Example 1

[0077] This embodiment only changes the thickness of the nickel foil to test the relevant performance of oxygen evolution in water electrolysis under surface ultrasonic assistance at different thicknesses.

[0078] Figure 2The vertical axis represents the current density during oxygen evolution in water electrolysis, and the horizontal axis represents the voltage during oxygen evolution. The figure shows the oxygen evolution LSV curves of nickel foils with thicknesses of 4µm, 8µm, and 10µm, measured with and without acoustic wave assistance. Without acoustic wave assistance, the 4µm, 8µm, and 10µm nickel foils at 50mA cm⁻¹... -2 The overpotentials at the locations were 849mV, 716mV, and 670mV, respectively; under acoustic wave conditions, the overpotentials of 4µm, 8µm, and 10µm nickel foils at 50mA cm⁻¹ were... -2 The overpotentials at the locations were 837mV, 699mV, and 643mV, respectively. After the application of sound waves, the overpotential of the 10µm thick nickel foil decreased the most, by only 27mV. The nickel foil itself has a relatively low responsiveness to ultrasound.

[0079] Comparative Example 2

[0080] First, 10-micron nickel foil was ultrasonically treated in 3M HCl solution for 10 minutes, followed by rinsing with ultrapure water and ethanol, and then drying with analytical grade argon gas. A 50 mL electroplating solution was prepared, consisting of 20 mM FeSO4 and a saturated KCl aqueous solution. Electrochemical treatment was performed in a two-electrode system, where both electrodes were pre-cleaned nickel foils, each with an area of ​​1 x 1 cm. 2 The two electrodes were placed parallel to each other, approximately 3 cm apart. The applied pulse current density during the experiment was ±50 mA / cm². 2 The pulse frequency was 5 Hz, and the pulse period was 750. After electrochemical treatment, the electrode was removed from the electrolyte, rinsed with ultrapure water and ethanol, and dried in a vacuum chamber for 8 hours. The NiFe LDH / NF catalyst was obtained.

[0081] Tests showed that in the electrolyte, the electrocatalytic oxygen evolution reaction could be carried out without ultrasonic assistance at a current density of 20 mA·cm⁻¹. -2 The overpotential is 303mV.

[0082] Comparative Example 3

[0083] First, 10-micron nickel foil was ultrasonically treated in 3M HCl solution for 10 minutes, followed by rinsing with ultrapure water and ethanol, and then dried with analytical grade argon gas. A 50 mL electroplating solution was prepared, consisting of 40 mM H₃BO₃ and a saturated KCl aqueous solution. Electrochemical treatment was performed in a two-electrode system, where both electrodes were pre-cleaned nickel foils, each with an area of ​​1 x 1 cm⁻¹. 2 The two electrodes were placed parallel to each other, approximately 3 cm apart. The applied pulse current density during the experiment was ±50 mA / cm². 2The pulse frequency was 5 Hz, and the pulse period was 750. After electrochemical treatment, the electrode was removed from the electrolyte, rinsed with ultrapure water and ethanol, and dried in a vacuum chamber for 8 hours. The Ni LDH-B / NF catalyst was obtained.

[0084] Tests showed that in the electrolyte, the electrocatalytic oxygen evolution reaction could be carried out without ultrasonic assistance at a current density of 20 mA·cm⁻¹. -2 The overpotential is 346mV.

[0085] like Figure 4 As shown, NiFe-LDH-B exhibits excellent intrinsic catalytic activity, with an OER overpotential of 294 mV at 20 mA cm⁻¹. -2 The value was significantly lower than that of NiFe-LDH (303 mV) and Ni-LDH-B (346 mV). Furthermore, the OER activity of different electrocatalysts was evaluated using Tafel plots; the Tafel slope for NiFe-LDH-B was 98 mV dec. -1 Much smaller than NiFe-LDH (111mV dec) -1 ), Ni-LDH-B (120mV dec) -1 The low Tafel slope of NiFe-LDH-B indicates excellent kinetic performance in its OER reaction. NiFe-LDH-B possesses the lowest charge transfer resistance R0. ct and the largest double-layer capacitance C dl This indicates that NiFe-LDH-B possesses extremely strong electron transport kinetics and electrochemical active area.

[0086] Ultrasound reduced the overpotential of NiFe LDH-B from 294mV to 237mV@20mAcm. -2 ( Figure 5 In (a), the Tafel slope decreased by 66 mV·dec -1 ( Figure 5 In part b), the charge transfer resistance decreases by 0.7Ω. Figure 5 In section c), the electrochemical active area increased by 4.75 cm². 2 ( Figure 5 d). Ultrasonic waves increased the current density at 500 mV by a full 2.1 times. The lack of significant changes in charge transfer resistance and electroactive area indicates that the significant performance improvement was not solely due to the surface cleaning effect of ultrasound; ultrasound also assisted in oxygen evolution.

[0087] Example 2

[0088] This embodiment uses an in-situ hybrid acoustic electrolysis cell system, such as Figure 1 and Figure 6 , 7 As shown, it includes:

[0089] Radio frequency source: Transmits an RF signal with a frequency of 5-15MHz and a level of 0-9dBm.

[0090] DC power supply: Provides 32V DC power to the signal amplifier.

[0091] Signal amplifier: Amplifies the RF signal strength from 5dBm to 60dBm.

[0092] Interdigitated electrodes: These consist of a 28.0 (horizontal) × 47.0 × 0.5 mm single-crystal piezoelectric (128° Y-rotation, X-propagation lithium niobate) substrate on which a comb-shaped transducer electrode (pattern) is photolithographically etched. The pattern consists of 30 pairs of 10 nm and 200 nm thick gold layers with an opening size of 5.6 mm, which can convert electrical signals into acoustic signals.

[0093] Electrolytic cell: It consists of a rectangular electrolyte chamber made of glass, measuring 13.0 mm (horizontal) × 13 mm × 24.5 mm × 1 cm (thickness), with the top and bottom surfaces unsealed.

[0094] Assembly: First, the working electrode is glued to the outside of the pattern on the interdigital electrode with AB glue. Then, the electrolytic cell is placed on the working electrode, and the bottom of the electrolytic cell is glued to the substrate of the interdigital electrode with AB glue. The working electrode is not completely covered inside the electrolytic cell, and some areas of the substrate are exposed. This completes the in-situ mixing acoustic electrolytic cell.

[0095] Next, connect the RF source and signal amplifier using a BNC-N port adapter cable, and then connect the signal amplifier to the interdigital electrodes using an N-port electrode clip. Connect the signal amplifier to a DC power supply, allowing the RF source's transmitted electrical signal to be amplified and converted into an acoustic signal by the interdigital electrodes. Finally, add KOH solution to the electrolytic cell, insert the counter electrode and reference electrode, and connect to an electrochemical workstation to perform relevant tests.

[0096] The embodiments of the present invention have been described in detail above, but the content described is only a preferred embodiment of the present invention and should not be considered as limiting the scope of the present invention. All equivalent changes and improvements made within the scope of the present invention should still fall within the scope of the present invention.

[0097] Any aspects not covered in this invention are applicable to existing technologies.

Claims

1. A method for preparing a low-crystallinity NiFe LDH three-dimensional nanosheet array catalyst, characterized in that, The preparation method is as follows: nickel foil is treated with strong acid, ultrapure water and anhydrous ethanol to remove surface impurities and oxide layer; the treated nickel foil is placed in an electrolyte composed of 1-20 mmol FeSO4, 1-10 mmol H3BO3 and saturated KCl aqueous solution, and a low crystallinity NiFe LDH three-dimensional nanosheet array catalyst is prepared by pulse electrodeposition. The pulsed current density applied in the pulsed electrodeposition method is ±10 to 100 mA / cm². 2 The pulse frequency is 0–20 Hz, and the pulse period is 0–1000.

2. The preparation method according to claim 1, characterized in that, The specific process of the preparation method is as follows: S1. Place 1-100μm nickel foil in a strong acid solution of 1-3M H ions and sonicate to remove any possible NiOx layer on its surface. Then rinse with ultrapure water and ethanol, and dry with dry analytical grade argon gas. S2. Add 1-20 mmol of FeSO4 and 1-10 mmol of H3BO3 to 50 mL of saturated KCl aqueous solution and stir until homogeneous to obtain electrolyte; S3. Electrochemical treatment is performed using pulse deposition, employing a dual-electrode system. Both electrodes are nickel foils pretreated in step S1, placed parallel to each other with a spacing of 1.5-3 cm. The electrolyte described in step S2 is used. The pulse current density applied in the pulse electrodeposition method is ±10~100 mA / cm². 2 The pulse frequency is 0–20 Hz, and the pulse period is 0–1000. S4. After the electrochemical treatment is completed, the electrode is removed from the electrolyte, rinsed with ultrapure water and anhydrous ethanol, and dried in a vacuum oven at 50-70°C for 8-16 hours to obtain a low-crystallinity NiFe LDH three-dimensional nanosheet array catalyst.

3. The preparation method according to claim 1, characterized in that, In step S1, the nickel foil thickness is 8-20 μm, and the strong acid is either an H2SO4 solution with a concentration of 0.8-1.2 mol / L or a 1-3 M HCl solution; in step S2, the FeSO4 concentration is 1-5 mmol, and the H3BO3 concentration is 1-3 mmol. In step S3, the applied pulse current density is ±30~60mA / cm². 2 The pulse frequency is 4–8 Hz, and the pulse period is 500–800.

4. A low-crystallinity NiFe LDH three-dimensional nanosheet array catalyst obtained by the preparation method according to any one of claims 1-3, characterized in that, The catalyst has a microstructure consisting of numerous wrinkled nanosheets, with crystalline and amorphous regions within the nanosheets.

5. The catalyst according to claim 4, characterized in that, Fe, Ni, O, and B elements are uniformly dispersed on the surface of the catalyst nanosheets.

6. An application of the catalyst according to claim 4, characterized in that, A low-crystallinity NiFe LDH three-dimensional nanosheet array catalyst was used as the working electrode in the electrocatalytic oxygen evolution reaction. This low-crystallinity NiFe LDH three-dimensional nanosheet array catalyst is designated NiFe LDH-B / NF. The specific application process is as follows: One side of the NiFe LDH-B / NF is the bonding surface, and the other side is the testing surface. The bonding surface of NiFe LDH-B / NF is bonded to the substrate of the interdigital electrode with AB glue. At a distance of 1.5-3mm from the photolithography pattern on the interdigital electrode, the excess AB glue is scraped off with a scraper and dried for 2.5-5 hours. Subsequently, the electrolytic cell was bonded to the interdigitated electrode with AB glue. The electrolytic cell covered the working electrode. The inside of the electrolytic cell was divided into a working electrode coverage area and a substrate area. Then it was dried overnight to obtain an in-situ mixed acoustic electrolytic cell. Prepare a 1.0M potassium hydroxide solution as the electrolyte for electrocatalysis, and introduce nitrogen gas into the in-situ mixed acoustic electrolysis cell to drive out the air; Using NiFe LDH-B / NF as the working electrode, graphite as the counter electrode, and a saturated calomel electrode as the reference electrode, the electrocatalytic oxygen evolution reaction was carried out in an electrocatalytic electrolyte by connecting to an electrochemical workstation. Connect the RF source to the signal amplifier and connect a 50-ohm resistor, then connect the interdigital electrodes; supply the signal amplifier with a DC power supply of 32V; during the electrocatalytic oxygen evolution test, the RF source, through the signal amplifier, causes the interdigital electrodes to convert an RF signal with a frequency of 5-15MHz and a level of 0-108dBm into an acoustic signal to assist in oxygen evolution and test its overpotential.

7. The application according to claim 6, characterized in that, The substrate of the interdigitated electrode is a lithium niobate single crystal. The photolithographic pattern converts the electrical signal into an acoustic signal. The acoustic wave is transmitted through the lithium niobate single crystal on the substrate and propagates to the working electrode attached to the single crystal. At the same time, the single crystal not covered by the working electrode propagates the acoustic wave into the electrolyte. The oxygen evolution performance of the electrocatalyst is promoted in the form of bulk acoustic waves and surface acoustic waves.

8. The application according to claim 6, characterized in that, Without surface ultrasonication, the working electrode operates at a current density of 20 mA·cm⁻¹. -2 The overpotential is 294 mV; under surface ultrasonic conditions, NiFe LDH-B / NF at a current density of 20 mA·cm⁻¹ -2 The overpotential was 237 mV; ultrasound reduced the overpotential of NiFe LDH-B from 294 mV to 237 mV @ 20 mA cm. -2 The Tafel slope decreased by 66 mV·dec -1 Ultrasonic waves can increase the current density at 500mV by at least two times.

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