Method for preparing platinum-loaded monatomic electrode through electro-deposition and electrode

Abstract

The invention discloses a method for preparing a platinum-loaded monatomic electrode through electro-deposition and the electrode. The method comprises the following steps: firstly, carrying out anode etching on foamed nickel in an electrolyte solution, and cleaning the etched foamed nickel by using alkali; and then placing the etched foamed nickel in a precursor solution containing nickel and iron ions to grow the NiFe LDH film. And performing cathode deposition on the foamed nickel electrode loaded with the NiFe LDH in an alkaline solution containing chloroplatinic acid radicals to prepare the NiFe LDH electrode loaded with platinum single atoms (Pt SAs). According to the method, by means of a cathode reduction method, the NiFe LDH catalyst uniformly loaded with platinum single atoms can be rapidly prepared at the room temperature. The electrodeposited NiFe LDH loaded with Pt SAs has a special coordination structure, so that the activity of electrocatalytic hydrogen evolution and oxygen evolution reaction of the composite material is enhanced. The preparation method is expected to introduce platinum single atoms into various LDH electrodes and further enhance the electrocatalytic activity of the electrodes.

Description

Technical Field

[0001] The present invention relates to the preparation of electrocatalytic electrodes, and particularly to a method for preparing a nickel-iron layered double hydroxide electrode loaded with single-atom platinum and the electrode. Background Art

[0002] With the growth of global energy demand and the intensification of environmental pollution problems, the development of efficient and sustainable energy conversion and storage technologies has become a current research hotspot. Among them, hydrogen production by electrolysis of water, as a way to obtain clean and renewable energy, has received extensive attention. However, the slow kinetics of water splitting reactions (including hydrogen evolution reaction (HER) and oxygen evolution reaction (OER)) make the development of efficient electrocatalysts a key factor for the large-scale application of this technology.

[0003] Platinum (Pt) is widely used in electrocatalytic reactions due to its excellent catalytic performance, especially showing extremely low overpotential and excellent stability in HER. However, due to the scarcity of platinum resources and high price, its large-scale application is limited. Therefore, researchers are committed to developing low-platinum-loaded or even platinum-free catalysts to reduce costs and improve catalytic efficiency. In recent years, single-atom catalysts (SACs) have become an ideal catalytic material because they maximize the utilization rate of noble metal atoms and at the same time exhibit excellent electrocatalytic performance. By precisely regulating the interaction between single-atom active sites and the carrier, the catalytic performance can be significantly improved and the stability of the catalyst can be enhanced.

[0004] Among many carrier materials, nickel-iron layered double hydroxide has been widely studied and applied as an OER catalyst due to its large specific surface area, rich active sites and good activity. In addition, the electrocatalytic activity of this material can be further improved by loading metal clusters, quantum dots or compounding with other materials. However, how to construct an efficient, stable and uniformly loaded single-atom platinum catalyst on a nickel foam substrate is an important challenge currently faced. Summary of the Invention

[0005] The purpose of the present invention is to propose a method for preparing a platinum single-atom loaded electrode by electrodeposition and the electrode in view of the deficiencies of the prior art.

[0006] The purpose of the present invention is achieved through the following technical solutions: A method for preparing a platinum single-atom loaded electrode by electrodeposition, comprising the following steps: 1) The nickel foam was ultrasonically cleaned successively with acetone, hydrochloric acid and water. The cleaned nickel foam was used as the working electrode, the silver / silver chloride electrode as the reference electrode, and the platinum sheet as the counter electrode to form a three-electrode system. Then, the nickel foam electrode was immersed in a sodium nitrate solution containing oxalic acid for anodic etching. After etching, the nickel foam was rinsed successively with an alkaline solution and deionized water to obtain a pretreated nickel foam electrode. 2) The pretreated nickel foam electrode was immersed in a mixed solution of ferrous ions (Fe²⁺) and nickel ions (Ni²⁺). After a constant-temperature reaction, it was taken out and rinsed with deionized water to obtain a nickel foam electrode with nickel-iron layered double hydroxide grown on it. 3) The nickel foam electrode with nickel-iron layered double hydroxide grown on it was used as the working electrode, the silver / silver chloride electrode as the reference electrode, and the platinum sheet as the counter electrode to form a three-electrode system. Cathodic deposition was carried out, and the cathodic deposition solution was chloroplatinic acid solution, and the pH was adjusted to alkaline with sodium hydroxide solution. After deposition, it was rinsed with deionized water, and the working electrode was placed in an oven to dry, obtaining a nickel-iron layered double hydroxide electrode loaded with platinum single atoms.

[0007] The concentration of oxalic acid in the sodium nitrate solution containing oxalic acid was 0.001 - 0.1 mol / L -1 , and the concentration of sodium nitrate was 0.01 - 1 mol / L -1 .

[0008] The potential of the anodic etching was 0.8 - 2.0 V, and the etching time was 1 - 10 min.

[0009] The source of the ferrous ions was one or more of ferrous sulfate, ferrous acetate, and ferrous chloride; the source of the nickel ions was one or more of nickel nitrate, nickel sulfate, and nickel chloride.

[0010] The concentration of the ferrous ions was 0.001 - 0.2 mol / L -1 , and the concentration of the nickel ions was 0.002 - 0.4 mol / L -1 .

[0011] The temperature of the constant-temperature reaction in step 2) was 25 - 70 °C, and the reaction time was 10 - 120 min.

[0012] The cathodic deposition potential in step 3) was -0.5 - -2.0 V, and the deposition time was 30 - 180 s.

[0013] The concentration of the chloroplatinic acid solution in step 3) was 0.0001 - 0.05 mol / L -1 .

[0014] A platinum single-atom loaded electrode prepared according to the above method has platinum single atoms stably and uniformly loaded on nickel-iron layered double metal hydroxide, improving the catalytic performance of the electrode, reducing the usage amount of platinum, and being used for water electrolysis.

[0015] The beneficial effects of the present invention are as follows: By means of the processes of anodic etching and growing nickel-iron layered double metal hydroxide, optimizing the electrodeposition conditions, the electrochemical activity of the nickel foam electrode can be greatly improved, and an anchoring matrix for platinum single atoms is provided, realizing the uniform loading of single-atom platinum. By loading platinum single atoms on nickel-iron layered double metal hydroxide, not only the catalytic performance of the electrode is improved, but also the usage amount of platinum is effectively reduced, saving precious metal resources. The present invention realizes the preparation of an electrode with low cost and high efficiency, provides a new solution for the development of high-efficiency and low-cost water electrolysis technology, and has broad application prospects in the new energy field.

[0016] Of course, not all of the beneficial effects above can be achieved by any technical solution of the present invention. Description of the Drawings

[0017] Figure 1(a) is the SEM image of the nickel-iron double metal hydroxide electrode loaded with platinum single atoms; Figure 1(b) is the EDS-Mapping image of the nickel-iron double metal hydroxide loaded with platinum single atoms.

[0018] Figure 2 is the high-angle annular dark-field imaging (STEM-HAADF) of scanning transmission electron microscopy.

[0019] Figure 3 is the XRD pattern of the nickel-iron double metal hydroxide electrode loaded with platinum single atoms.

[0020] Figure 4 is the linear sweep voltammogram of the nickel-iron double metal hydroxide electrode loaded with platinum single atoms. Detailed Embodiments

[0021] The present invention discloses a method for preparing a nickel-iron layered double hydroxide (NiFe LDH) electrode loaded with single-atom platinum. First, nickel foam is anodically etched in an electrolyte solution, and the etched nickel foam is cleaned with an alkali. Then, the etched nickel foam is placed in a solution containing nickel and iron ion precursors to grow a NiFe LDH thin film. The nickel foam electrode loaded with NiFe LDH is subjected to cathodic deposition in an alkaline solution containing chloroplatinic acid root to prepare a NiFe LDH electrode loaded with single-atom platinum (Pt SAs). This method can rapidly prepare a NiFe LDH catalyst uniformly loaded with single-atom platinum at room temperature by means of cathodic reduction. The electrodeposited NiFe LDH loaded with Pt SAs has a special coordination structure, enhancing the electrocatalytic hydrogen evolution and oxygen evolution reaction activities of its composite material. This preparation method is expected to introduce single-atom platinum into various LDH electrodes and further enhance the electrocatalytic activity of the electrodes. Example 1

[0022] 1) Acetone, hydrochloric acid, and water were used in sequence for ultrasonic cleaning to clean the nickel foam. The cleaned nickel foam was used as the working electrode, the silver / silver chloride electrode was used as the reference electrode, and the platinum sheet was used as the counter electrode to form a three-electrode system. Then, the nickel foam was immersed in a mixed solution of 0.05 mol L -1 oxalic acid and 0.1 moL L -1 sodium nitrate, and anodically etched at 1.5 V for 5 min. The etched nickel foam was rinsed successively with an alkali solution and deionized water to obtain a pretreated nickel foam electrode; 2) The pretreated nickel foam electrode was immersed in a mixed solution of 0.01 mol L -1 ferrous sulfate and 0.02 mol L -1 nickel nitrate. After reacting at 50 °C for 1 h, it was taken out and rinsed with deionized water to obtain a nickel foam electrode grown with nickel-iron layered double hydroxide; 3) The electrode grown with nickel-iron layered double hydroxide was used as the working electrode, the silver / silver chloride electrode was used as the reference electrode, and the platinum sheet was used as the counter electrode to form a three-electrode system. Cathodic deposition was carried out at -1.3 V for 90 s. The cathodic deposition solution was 0.001 mol L -1 chloroplatinic acid solution, and the pH was adjusted to 12 using sodium hydroxide solution. After deposition, it was rinsed with deionized water, and the electrode was placed in an oven and dried at 60 °C for 4 h to obtain a nickel-iron layered double hydroxide electrode loaded with single-atom platinum.

[0023] The prepared samples were observed by scanning electron microscopy (SEM) and energy-dispersive spectroscopy (EDS). As shown in Fig. 1(a), a large number of nanoflower structures grew on the surface of the nickel-iron layered double hydroxide electrode loaded with single-atom platinum. As shown in Fig. 1(b), the EDS results indicated the presence of uniformly distributed Ni, Fe, Pt, and O signals on the sample surface, proving the loading of Pt. Figure 2 The presence of single-atom Pt was observed by high-angle annular dark-field imaging in scanning transmission electron microscopy (STEM-HAADF). Figure 3 The X-ray diffraction (XRD) results showed that the synthesized nanoflower structure was the NiFe LDH phase. All of the above proved that this method could successfully prepare the nickel-iron layered double hydroxide electrode loaded with single-atom platinum. Figure 4 From the linear sweep voltammetry curves, it can be seen that the nickel-iron layered double hydroxide electrode loaded with single-atom platinum had excellent electrocatalytic activities for hydrogen evolution and oxygen evolution simultaneously. Example 2

[0024] 1) Acetone, hydrochloric acid, and water were used in sequence for ultrasonic cleaning to clean the nickel foam. The cleaned nickel foam was used as the working electrode, the silver / silver chloride electrode was used as the reference electrode, and the platinum sheet was used as the counter electrode to form a three-electrode system. Then, the nickel foam was immersed in a mixed solution of 0.01 mol L -1 oxalic acid and 0.1 moL L -1 sodium nitrate, and anodic etching was carried out at 0.8 / 1.2 / 1.4 / 1.6 / 1.8 / 2.0 V for 5 min. The etched nickel foam was rinsed with alkali solution and deionized water in sequence to obtain the pretreated nickel foam electrode.

[0025] The specific steps of steps 2) and 3) refer to Example 1. The nickel-iron layered double hydroxide electrodes loaded with single-atom platinum after etching at different anodic potentials all had good OER and HER activities, as shown in Table 1.

[0026] Table 1 Influence of anodic etching potential Example 3

[0027] 1) Acetone, hydrochloric acid, and water were used in sequence for ultrasonic cleaning to clean the nickel foam. The cleaned nickel foam was used as the working electrode, the silver / silver chloride electrode was used as the reference electrode, and the platinum sheet was used as the counter electrode to form a three-electrode system. Then, the nickel foam was immersed in a mixed solution of 0.001 / 0.1 mol L -1 oxalic acid and 0.01 / 1 moL L -1 sodium nitrate, and anodic etching was carried out at 1.5 V for 5 min. The etched nickel foam was rinsed with alkali solution and deionized water in sequence to obtain the pretreated nickel foam electrode.

[0028] For steps 2) and 3), refer to Example 1 for specific steps. The anodic etching solution and the nickel-iron layered double hydroxide electrode loaded with platinum single atoms over time both have good OER and HER activities, as shown in Table 2.

[0029] Table 2 Influence of anodic etching solution and time Example 4

[0030] 1) Use acetone, hydrochloric acid, and water in sequence for ultrasonic cleaning to clean the nickel foam. The cleaned nickel foam serves as the working electrode, the silver / silver chloride electrode serves as the reference electrode, and the platinum sheet serves as the counter electrode to form a three-electrode system. Then, immerse the nickel foam into a mixed solution of 0.01 mol L -1 oxalic acid and 0.1 moL L -1 sodium nitrate, and perform anodic etching at 1.5 V for 1 / 3 / 5 / 8 / 10 min respectively. The etched nickel foam is rinsed with alkali solution and deionized water in sequence to obtain the pretreated nickel foam electrode.

[0031] For steps 2) and 3), refer to Example 1 for specific steps. The nickel-iron layered double hydroxide electrodes loaded with platinum single atoms after different anodic etching times all have good OER and HER activities, as shown in Table 3.

[0032] Table 3 Influence of anodic etching time Example 5

[0033] 1) Refer to Example 1 for specific steps; 2) Immerse the pretreated nickel foam electrode into a mixed solution of 0.001 / 0.2 mol L -1 ferrous sulfate and 0.002 / 0.4 molL -1 nickel nitrate, take it out after reacting at 25 / 70 °C for 10 / 120 min, and rinse it with deionized water to obtain the nickel foam electrode with nickel-iron layered double hydroxide grown; 3) Refer to Example 1 for specific steps.

[0034] Nickel-iron layered double hydroxide can be successfully prepared at different nickel-iron ion concentrations, reaction temperatures, and times, and it does not affect the subsequent loading of platinum single atoms. At the same time, the electrode still has good OER and HER activities, as shown in Table 4.

[0035] Table 4 Influence of different NiFe LDH preparation conditions Example 6

[0036] Steps 1) and 2) refer to Example 1 for specific steps; 3) Use the electrode with grown nickel-iron layered double hydroxide as the working electrode, silver / silver chloride electrode as the reference electrode, and platinum sheet as the counter electrode to form a three-electrode system. Perform cathodic deposition at -0.5 / -1.0 / -1.5 / -2.0 V for 30 / 60 / 120 / 180 s. The cathodic deposition solution is 0.001 mol L -1 chloroplatinic acid solution, and adjust the pH to 12 using sodium hydroxide solution. After deposition, rinse with deionized water and place the electrode in an oven at 60 °C for drying for 4 h to obtain a nickel-iron layered double hydroxide electrode loaded with single-atom platinum.

[0037] Nickel-iron layered double hydroxide loaded with single-atom platinum can be successfully prepared at different cathodic deposition potentials and deposition times, and at the same time, the electrode still has good OER and HER activities, as shown in Table 5.

[0038] Table 5 Effects of different deposition potentials and deposition times Example 7

[0039] Steps 1) and 2) refer to Example 1 for specific steps; 3) Use the electrode with grown nickel-iron layered double hydroxide as the working electrode, silver / silver chloride electrode as the reference electrode, and platinum sheet as the counter electrode to form a three-electrode system. Perform cathodic deposition at -1.3 V for 90 s. The cathodic deposition solution is 0.0001 / 0.001 / 0.01 / 0.05 mol L -1 chloroplatinic acid solution, and adjust the pH to 12 using sodium hydroxide solution. After deposition, rinse with deionized water and place the electrode in an oven at 60 °C for drying for 4 h to obtain a nickel-iron layered double hydroxide electrode loaded with single-atom platinum.

[0040] Nickel-iron layered double hydroxide loaded with single-atom platinum can be successfully prepared at different chloroplatinic acid concentrations, and at the same time, the electrode still has good OER and HER activities, as shown in Table 6.

[0041] Table 6 Effects of different chloroplatinic acid concentrations

[0042] The above embodiments are only used to explain the present invention, rather than limiting the present invention. Any modifications and changes made within the spirit and scope of the claims of the present invention fall within the protection scope of the present invention.

Claims

1. A method for preparing a platinum-loaded single-atom electrode by electrodeposition, characterized in that: The steps include: 1) Using acetone, hydrochloric acid and water to ultrasonically clean nickel foam in sequence, the cleaned nickel foam is used as a working electrode, a silver / silver chloride electrode is used as a reference electrode, and a platinum sheet is used as a counter electrode to form a three-electrode system; then, the nickel foam electrode is immersed in a sodium nitrate solution containing oxalic acid for anodic etching, and the etched nickel foam is rinsed with alkaline solution and deionized water in sequence to obtain a pretreated nickel foam electrode; 2) The pretreated nickel foam electrode is immersed in a mixed solution of ferrous ions (Fe²⁺) and nickel ions (Ni²⁺), taken out after constant temperature reaction, and rinsed with deionized water to obtain a nickel foam electrode with grown nickel-iron layered double hydroxide; 3) A nickel foam electrode on which nickel-iron layered double hydroxide is grown is used as a working electrode, a silver / silver chloride electrode is used as a reference electrode, and a platinum sheet is used as a counter electrode to form a three-electrode system; cathode deposition is performed, and the cathode deposition solution is a chloroplatinic acid solution, and a sodium hydroxide solution is used to adjust the pH to alkaline; After the deposition is completed, it is rinsed with deionized water and the working electrode is placed in an oven for drying to obtain a nickel-iron layered double hydroxide electrode loaded with platinum single atoms.

2. The method according to claim 1, characterized in that The concentration of oxalic acid in the sodium nitrate solution containing oxalic acid is 0.001-0.1 mol L -1 , the concentration of sodium nitrate is 0.01~1 mol L -1 .

3. The method according to claim 1, characterized in that The potential of the anodic etching is 0.8-2.0 V, and the etching time is 1-10 min.

4. The method according to claim 1, characterized in that The ferrous ion source is one or more of ferrous sulfate, ferrous acetate, and ferrous chloride; the nickel ion source is one or more of nickel nitrate, nickel sulfate, and nickel chloride.

5. The method according to claim 1, characterized in that: The ferrous ion concentration is 0.001~0.2 mol L -1 , the concentration of nickel ions is 0.002~0.4 mol L -1 .

6. The method according to claim 1, characterized in that The isothermal reaction temperature of step 2) is 25-70°C, and the reaction time is 10-120 min.

7. The method according to claim 1, characterized in that The cathode deposition potential in step 3) is -0.5~-2.0V, and the deposition time is 30~180s.

8. The method according to claim 1, characterized in that: The concentration of the chloroplatinic acid solution in step 3) is 0.0001-0.05 mol L -1 .

9. A single-atom-loaded platinum electrode prepared according to the method according to any one of claims 1 to 8, characterized in that: Platinum single atoms are stably and evenly loaded on nickel-iron layered double hydroxide, which improves the catalytic performance of the electrode and reduces the amount of platinum used for water electrolysis.

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