Self-supporting electrode and preparation method and application thereof

Abstract

The invention relates to a self-supporting electrode and a preparation method and application thereof, and belongs to the technical field of new energy and alkaline electro-catalytic water decomposition. A preparation method of a self-supporting electrode comprises the following steps: taking a nickel net, foamed nickel or a stainless steel net as a substrate, taking deionized water containing a ferric iron compound and phosphate as an etching solution, soaking the substrate in the etching solution at room temperature, taking out the substrate, and drying at room temperature to obtain a surface-modified self-supporting electrode; according to the method, PO4 < 3-> is introduced while the Fe / M self-supporting electrode is synthesized through a one-step etching method, so that the free energy of * OH and * O intermediates is adjusted, the valence state is adjusted, and the oxygen evolution reaction rate is increased; meanwhile, PO4 < 3-> and Fe sites act, so that the Fe coordination sites are stabilized, and precipitation of iron is prevented; the self-supporting electrode prepared by using a room-temperature one-step chemical etching method not only has good water electrolysis oxygen evolution reaction activity, stability and repeatability, but also is simple and rapid in preparation process and low in cost, and large-scale industrial production can be realized.

Description

Technical Field

[0001] The present application belongs to the field of new energy and alkaline electrocatalytic water splitting technology, and specifically relates to a self-supporting electrode and its preparation method and application, and specifically relates to a room temperature one-step chemical etching method to quickly prepare a highly active and highly stable self-supporting electrode and its preparation method and its application in electrocatalytic water splitting and oxygen separation under alkaline conditions. Background Art

[0002] Traditional fossil energy faces problems such as resource depletion and environmental pollution risks, making it difficult to meet the needs of human society. Among the many new energy sources, hydrogen energy is a potential energy carrier with high energy density and zero emissions in terminal applications. The electrolysis of water to produce hydrogen technology has a controllable reaction and high production purity (above 99.7%). It can also use the electricity generated by other renewable resources (wind, light, water, etc.) to convert it into hydrogen energy for storage and utilization, making up for the intermittent nature of some renewable energy sources and has broad application prospects. Alkaline electrolyzer hydrogen production is a relatively mature water electrolysis hydrogen production technology. The water electrolysis hydrogen production reaction consists of the cathode hydrogen evolution reaction (HER) and the anode oxygen evolution reaction (OER). Since the OER reaction involves the transfer of four electrons, it is the rate-controlling reaction of the water electrolysis reaction and has a high energy barrier. Therefore, the performance of the OER catalyst plays a decisive role in the efficiency of water electrolysis.

[0003] Among the many catalysts for oxygen evolution by water electrolysis, ruthenium-based and iridium-based noble metal catalysts have excellent OER activity, but their scarcity, high price, and poor stability during the catalytic process make them difficult to apply on a large scale. Non-noble metal catalysts, on the other hand, are being continuously developed and applied due to their low cost and abundant reserves. Among them, nickel-iron (NiFe)-based catalysts have very ideal electrochemical activity in alkaline electrolytes and are considered to be one of the most effective OER catalysts. For example, the prior art CN116695158A discloses an electrode and its preparation method, as well as an alkaline water electrolysis hydrogen production device. The electrode preparation method comprises the following steps: forming a catalyst layer on the electrode body by an in-situ electrochemical deposition method, wherein the material of the catalyst layer includes: a noble metal material and / or a non-noble metal material. The electrode prepared by the electrode preparation method provided in this application has excellent durability and can significantly improve the current density and catalytic hydrogen production efficiency of the hydrogen production device.

[0004] The present invention relates to a surface-deposition-resistant hydrogen evolution electrode disclosed in prior art CN118086949A, and its preparation method and application, which belong to the field of applied electrochemical technology. The present invention first deposits a catalytic layer on the surface of a conductive substrate using an electrochemical deposition method or a hydrothermal method, and then deposits a hydroxide film layer on the surface of the catalytic layer using an electrochemical deposition method or a chemical deposition method. The hydroxide film layer is a hydroxide film containing certain defects. The hydrogen evolution electrode prepared by the present invention after modifying the hydroxide deposition layer can significantly hinder the mass transfer of magnesium and calcium ions in the electrolyte to the reaction site of the hydrogen evolution electrode, reduce the deposition of magnesium and calcium ions on the electrode surface, significantly improve the anti-deposition performance in seawater, and can be applied to seawater / saline water electrolysis or seawater batteries.

[0005] However, existing catalyst preparation processes are complex, making large-scale production difficult in practice. During the electrocatalytic reaction, the localized acidic environment near the active site leads to the dissolution of iron (Fe). This dissolved Fe is then incorporated into the substrate lattice and redeposited during the OER process, resulting in uneven Fe distribution and catalyst deactivation, significantly reducing stability. To address these issues, the rational design and synthesis of simple, efficient, and stable catalytic materials that exhibit both high activity and stability in alkaline water electrolysis is crucial for water electrolysis.

[0006] In order to address the shortcomings and deficiencies of the prior art, the present application proposes a room temperature one-step chemical etching method for rapidly preparing a highly active and highly stable self-supporting electrode, a preparation method thereof, and its application in electrocatalytic water splitting and oxygen release under alkaline conditions. Summary of the Invention

[0007] Taking the above problems into consideration, the applicant used the etching effect of Fe(NO)3 solution on the substrate (Ni, etc.) to generate Ni(OH)2 and Fe(OH)3 in situ on the substrate, simplifying the catalyst synthesis steps; and using the adsorption effect of strongly electronegative oxygen-containing anions on Fe to lock the Fe active center, which can effectively prevent Fe from dissolving. 3- It can not only adsorb with Fe to prevent Fe dissolution, but also effectively regulate the electronic structure of Ni sites, enhance the nickel-oxygen covalency, and improve oxygen evolution activity and stability.

[0008] Based on this, a room temperature one-step chemical etching method was developed to quickly prepare highly active and highly stable self-supporting electrodes. This preparation method is simple and efficient, and can achieve large-area preparation of catalytic electrodes; the introduction of Fe and P can simultaneously prevent the precipitation of iron, which can enable it to have high activity while effectively improving the activity and stability of the catalyst, reducing the economic cost of water electrolysis equipment, and providing technical support for the application of non-precious metals in the field of alkaline water electrolysis.

[0009] Specifically, this application includes the following contents: First aspect: The present application proposes a self-supporting electrode, comprising a substrate, which is any one of nickel mesh, nickel foam, and stainless steel mesh; and a layer, which is nickel iron phosphide hydroxide attached to the substrate.

[0010] Furthermore, the layer is attached to the substrate at room temperature.

[0011] Furthermore, the layer is attached to the substrate by immersion at room temperature.

[0012] Furthermore, the layer does not need to be deposited electrochemically.

[0013] Furthermore, the self-supporting electrode is -2 The stable operation time under current density conditions is not less than 500 hours.

[0014] Furthermore, the self-supporting electrode can reach 100 mA / cm2 in an alkaline medium of 1M KOH. 2 The overpotential required for the catalytic current density is no higher than 350 mV.

[0015] Furthermore, the potential measurement conditions are as follows: the self-supporting electrode is used as the working electrode in the electrolytic cell, the mercury / mercuric oxide electrode is used as the reference electrode, the platinum wire is used as the counter electrode, and 1 M KOH is used as the electrolyte.

[0016] Furthermore, when the substrate is a nickel mesh, the mesh size of the nickel mesh is 40-200 meshes.

[0017] Furthermore, when the substrate is a stainless steel mesh, the mesh size of the nickel mesh is 40-200 meshes.

[0018] Furthermore, when the substrate is nickel foam, the pore size of the nickel foam is 100-120 PPI.

[0019] In a second aspect, the present application proposes a method for preparing a self-supporting electrode, comprising the following steps: Step 1) preparing a substrate, wherein the substrate is any one of nickel mesh, nickel foam or stainless steel mesh; Step 2) preparing an etching solution, wherein the etching solution is a solution prepared from a water-soluble iron salt, a phosphate and water; Step 3) cleaning the substrate in step 1) to obtain a cleaned substrate; Step 4) preparing the layer, soaking the substrate obtained in step 3) in the etching solution obtained in step 2) for 10-30 minutes, taking out the substrate, and drying at room temperature to obtain a self-supporting electrode.

[0020] Furthermore, in step 1), the step of preparing the substrate further includes ultrasonically cleaning the substrate with 1 M HCl, acetone, ethanol, and water in sequence, and the optional cleaning time is 5-15 minutes.

[0021] Furthermore, in step 2), the iron salt is at least one or more of ferric nitrate, ferric chloride and ferric sulfate; and the phosphate is at least one or more of sodium hydrogen phosphate, sodium dihydrogen phosphate, potassium hydrogen phosphate and potassium dihydrogen phosphate.

[0022] Furthermore, in step 2), the molar volume ratio of the metal salt to ultrapure water is 0.1-1 mmol:10 mL; and the molar volume ratio of the phosphate to ultrapure water is 0.3-1 mmol:10 mL.

[0023] Furthermore, the layer in step 4) is nickel iron phosphide oxide.

[0024] In a third aspect, the present application discloses the use of the self-supporting electrode according to the first aspect or the self-supporting electrode prepared by the method of the second aspect, for electrocatalytic water splitting to release oxygen in an alkaline environment.

[0025] Furthermore, the self-supporting electrode has excellent performance of high stability and high activity in the application of electrocatalytic water splitting to decompose hydrogen in an alkaline environment.

[0026] Furthermore, the self-supporting electrode reaches 100 mA / cm in 1M KOH. 2 The overpotential at the current density is about 309 mV. And at 1000 mA / cm -2 The stable operation time under current density conditions exceeds 500 hours.

[0027] Beneficial effects of the present invention: The materials used in the present invention are non-precious metal materials, which are highly abundant in nature, low in price, and easy to obtain. They are prepared by a one-step etching method to obtain a self-supporting electrode in one piece. The synthesis process is rapid and highly repeatable, which greatly reduces the preparation cost and is suitable for large-scale production without the need for electrodeposition.

[0028] The present invention prepares a self-supporting electrode by in-situ growing an active material on a substrate such as Ni, which is easy to manufacture on a large scale and can be directly used in industrial electrolytic cells. It effectively prevents catalyst shedding in working environments.

[0029] The synthetic raw materials of the present invention have a wide range of sources and have significant cost advantages compared with traditional ruthenium and ethylene noble metal catalysts.

[0030] The nickel-based electrode material prepared by the present invention has high electrocatalytic oxygen evolution activity under alkaline conditions, and can be used for electrocatalytic oxygen evolution at a current density of 100 mA cm -2In certain embodiments, the Tafel slope of the catalyst is 55.3 mV / dec.

[0031] The nickel-based electrode material prepared by the present invention has stable performance and can withstand 1000 mA / cm -2 It can run stably for more than 500 hours with good repeatability. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 : Raman spectrum of the self-supporting electrode prepared in Example 1.

[0033] Figure 2 : Hydrogen polarization curves of water splitting analysis of Example 1 and Comparative Examples 1-2 in alkaline electrolyte (1 M KOH).

[0034] Figure 3 : X-ray diffraction (XRD) pattern of the self-supporting electrode prepared in Example 1.

[0035] Figure 4 : Optical photographs of the nickel mesh and the nickel mesh electrode after immersion in Example 1.

[0036] Figure 5 : Scanning electron microscope (SEM) photograph of the self-supporting electrode prepared in Example 1; Figure 5 The scale bar in (a) is 50㎛. Figure 5 The scale bar in (b) is 50㎛. Figure 5 The scale bar in (c) is 1㎛.

[0037] Figure 6 : Polarization curve of the surface-modified nickel mesh electrode prepared in Example 1 in water splitting and oxygen release in an alkaline electrolyte (1 M KOH); Figure 6 The horizontal axis is the voltage (relative to the reversible hydrogen electrode) and the vertical axis is the current density. The data were obtained by measuring the polarization curve using the Shanghai Chenhua CHI 650e electrochemical workstation.

[0038] Figure 7 : Repeatability experiment of polarization curve of water splitting and oxygen decomposition of the surface modified nickel mesh electrode prepared in Example 1 in alkaline electrolyte (1 M KOH).

[0039] Figure 8 :Example 1 is enlarged to obtain 1 m 2 Optical photograph of surface-modified nickel material electrode.

[0040] Figure 9 : Example 1 was scaled up to obtain 1 m 2 Polarization curves of oxygen released by water splitting over a surface-modified nickel mesh electrode in an alkaline electrolyte (1 M KOH).

[0041] Figure 9 The horizontal axis is (relative to the reversible hydrogen electrode) and the vertical axis is the current density. The data were measured by Shanghai Chenhua CHI 650e electrochemical workstation.

[0042] Figure 10 :Example 1 is enlarged to obtain 1 m 2 Polarization curves of surface-modified nickel mesh electrode for oxygen desorption by water splitting in industrial alkaline electrolyte (30 wt% KOH).

[0043] Figure 10 The horizontal axis is the potential (relative to the reversible hydrogen electrode) and the vertical axis is the current density. The data were measured by Shanghai Chenhua CHI 650e electrochemical workstation.

[0044] Figure 11 Water splitting analysis hydrogen polarization curves of the surface modified nickel material electrode and the material of comparative example 1 before and after 5000 cycles of CV testing. DETAILED DESCRIPTION Example 1

[0045] Preparation of FeP / NM self-supporting electrode (NM is the abbreviation of nickel mesh in English): a method for preparing a self-supporting electrode: 1. Cut the nickel mesh into strips of 1 cm x 3 cm in length and width, and ultrasonically clean them with 1 M HCl, acetone, ethanol, and water for 10 min, respectively. Then, air-dry them and set aside. 2. Weigh 0.355 g (0.87 mmol) of ferric nitrate nonahydrate and 0.06899 g (0.5 mmol) of sodium dihydrogen phosphate into a beaker. Then add 10 mL of ultrapure water and stir to fully dissolve the raw materials to obtain an etching solution. 3. Soak the nickel mesh after ultrasonic cleaning in the above-prepared etching solution, let it soak for 15 minutes, and dry it naturally at room temperature to obtain a FeP / NM electrode self-supporting electrode.

[0046] The same concentration of etching solution was expanded to 30 L, and 1 m 2 The nickel mesh was placed in the etching solution and soaked for 20 min, then taken out and dried at room temperature to prepare a large-area surface-modified nickel mesh electrode. Examples 2-4

[0047] Compared with Example 1, the immersion time in the etching solution was changed to 15 min, 30 min, and 60 min to prepare surface-modified self-supporting nickel-based electrodes.

[0048] In 1 M KOH electrolyte, the current density reached 100 mA cm -2When , the required overpotentials are 308 mV, 315 mV and 311 mV respectively. Examples 5-7

[0049] Compared with Example 1, the molar mass of iron nitrate was adjusted to 0.1 mmol, 0.4 mmol, and 0.87 mmol, and the surface-modified self-supporting nickel material electrode was prepared by immersing for 15 min. In 1 M KOH electrolyte, the current density reached 100 mA cm -2 When , the required overpotentials are 350 mV, 320 mV and 308 mV respectively. Examples 8-10

[0050] Compared with Example 1, the molar mass of P was adjusted to 0.3 mmol, 0.5 mmol, and 0.8 mmol, and the surface-modified self-supporting nickel material electrode was prepared by immersing for 15 min. In 1 M KOH electrolyte, the current density reached 100 mA cm -2 When , the required overpotentials are 292 mV, 261 mV, and 254 mV respectively. Example 11

[0051] Compared with Example 1, the nickel mesh substrate was replaced with nickel foam to obtain a surface-modified self-supporting nickel material electrode. In 1M KOH electrolyte, the current density reached 100 mA cm -2 When , the required overpotential is 283 mV. Example 12

[0052] Compared with Example 1, the surface-modified self-supporting electrode can be obtained by replacing the nickel mesh substrate with a stainless steel mesh substrate. In 1M KOH electrolyte, the current density reaches 100 mA cm -2 When , the required overpotential is 356 mV. Comparative Example 1

[0053] The preparation method of this comparative example 1 is basically the same as that of Example 1. Compared with Example 1, the etching solution used in this comparative example is prepared by adding only ferric nitrate, and the self-supporting electrode is prepared by immersion. In 1M KOH electrolyte, the current density reaches 100 mA cm -2 When , the required overpotential is 317 mV. Comparative Example 2

[0054] The preparation method of this comparative example 2 is basically the same as that of Example 1. Compared with Example 1, the etching solution used in this comparative example is prepared by adding only sodium dihydrogen phosphate, and the self-supporting electrode is prepared by immersion. In 1M KOH electrolyte, the current density reaches 90 mA cm -2 When , the required overpotential is 398 mV.

[0055] Analyze with the accompanying drawings: Figure 1 The Raman spectrum of the FeP / NM self-supporting electrode is shown in Figure 560.2 cm -1 Assigned to Ni-O or Fe-O, 677.9 cm -1 It belongs to Fe-O, which means that the FeP / NM material is nickel iron phosphide oxide. The present invention successfully prepares the FeP / NM material through the preparation method of the self-supporting electrode.

[0056] Figure 2 The hydrogen polarization curves of water splitting analysis in alkaline electrolyte (1 M KOH) for Example 1 and the comparative example are shown.

[0057] Figure 3 The XRD spectrum of the obtained FeP / NM shows that the original characteristic peak of the nickel mesh base in the spectrum belongs to Ni, indicating that the substance on the surface of the surface-modified nickel-based electrode exists in an amorphous form and has an amorphous structure.

[0058] Figure 4 These are optical photos of the electrode material before and after immersion of the nickel mesh. After immersion, the color of the nickel mesh becomes darker, and the substrate is successfully etched in the etching solution.

[0059] Figure 5 This is a scanning electron microscope (SEM) photograph of the obtained surface-modified FeP / NM material. It can be seen that the surface of the obtained FeP / NM material is flaky.

[0060] The FeP / NM electrode was used as the working electrode, the mercury / mercuric oxide electrode was used as the reference electrode, the platinum wire was used as the counter electrode, and 1 M KOH was used as the electrolyte. The current density reached 100 mA cm -2 The required overpotential is 309 mV. It should be noted that in the electrocatalytic tests, all potentials obtained using the mercury / mercury oxide electrode as the reference electrode were converted to reversible hydrogen electrode potentials in the property diagrams, and the external power supply was the main battery of the electrochemical workstation.

[0061] Figure 6 The electrocatalytic oxygen evolution properties of the material in 1 M KOH electrolyte were plotted at a current density of 100 mA cm -2 When the overpotential is 309 mV (corresponding to 1.539 V in the horizontal axis), the overpotential required for the FeP / NM electrode is 83 mV lower than that of NM (392 mV, corresponding to 1.622 V in the horizontal axis).

[0062] Figure 7The experimental results of repeated electrocatalytic oxygen evolution properties of the material in 1 M KOH electrolyte are shown, indicating that the integrated nickel-based electrode material obtained by the preparation method has stable performance and good repeatability.

[0063] Figure 8 Surface modified nickel material electrode material 1 m 2 Enlarged optical photos before and after immersion in the experiment show that the large area of nickel mesh was evenly etched after immersion.

[0064] Figure 9 On the surface modified nickel material electrode 1 m 2 Magnified experimental diagram of electrocatalytic oxygen evolution in 1 M KOH electrolyte, with a current density of 100 mA cm -2 When , the required overpotential is 309 mV.

[0065] Figure 10 Surface modified nickel material electrode 1 m 2 Scale-up experiment of electrocatalytic oxygen evolution in 30 wt% KOH electrolyte (under industrial conditions) at 25°C, with a current density of 100 mA cm -2 When , the required overpotential is 269 mV.

[0066] Figure 11 The hydrolysis analysis hydrogen polarization curves of the surface-modified nickel material electrode Example 1 and Comparative Example 1 were tested before and after 5000 cycles of CV testing. The activity of Comparative Example 1 was significantly attenuated, while the performance of Example 1 was stable.

[0067] The above embodiments are only preferred exemplary embodiments of the present application, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any person skilled in the art can easily think of development or replacement within the technical scope disclosed by the present invention, which shall fall within the protection scope and disclosure scope of the present invention.

Claims

1. A self-supporting electrode, characterized in that: The method comprises: a substrate, wherein the substrate is any one of nickel mesh, nickel foam, and stainless steel mesh; A layer is attached to the substrate, wherein the layer is nickel iron phosphide hydroxide.

2. The self-supporting electrode according to claim 1, characterized in that The self-supporting electrode, at 1000 mA / cm -2 The stable operation time under current density conditions is not less than 500 hours.

3. The self-supporting electrode according to claim 1, wherein The self-supporting electrode can reach 100 mA / cm in the alkaline medium of 1M KOH. 2 The overpotential required for the catalytic current density is no higher than 350 mV.

4. The self-supporting electrode according to claim 3, wherein The potential measurement conditions are as follows: the self-supporting electrode is used as the working electrode in the electrolytic cell, the mercury / mercuric oxide electrode is used as the reference electrode, the platinum wire is used as the counter electrode, and 1 M KOH is used as the electrolyte.

5. A method for preparing a self-supporting electrode according to any one of claims 1 to 4, characterized in that: The steps include: Step 1) preparing a substrate, wherein the substrate is any one of nickel mesh, nickel foam or stainless steel mesh; Step 2) preparing an etching solution, wherein the etching solution is a solution prepared from a water-soluble iron salt, a phosphate and water; Step 3) cleaning the substrate in step 1) to obtain a cleaned substrate; Step 4) preparing the layer, soaking the substrate obtained in step 3) in the etching solution obtained in step 2) for 10-30 minutes, taking out the substrate, and drying it to obtain a self-supporting electrode.

6. The method for preparing a self-supporting electrode according to claim 5, wherein: In step 1), the step of preparing the substrate further includes ultrasonically cleaning the substrate with 1 M HCl, acetone, ethanol, and water in sequence, and the optional cleaning time is 5-15 minutes.

7. The method for preparing a self-supporting electrode according to claim 5, wherein: In step 2), the iron salt is ferric nitrate; and the phosphate is one or more of sodium hydrogen phosphate and sodium dihydrogen phosphate.

8. The method for preparing a self-supporting electrode according to claim 5, wherein: In step 2), the molar volume ratio of the metal salt to pure water is 0.1-1 mmol:10 mL; the molar volume ratio of the phosphate to pure water is 0.3-1 mmol:10 mL.

9. The method for preparing a self-supporting electrode according to any one of claims 5 to 8, characterized in that: The layer in step 4) is nickel iron phosphide oxide.

10. Use of the self-supporting electrode according to any one of claims 1 to 4 or the self-supporting electrode prepared by the method according to any one of claims 5 to 9, characterized in that: Used for electrocatalytic water splitting and oxygen extraction in alkaline environment.

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