Electrochemically etched nickel-based alloy and surface treatment method thereof, alkaline hydrogen production electrolyzer and cathode electrode thereof

Abstract

This invention relates to an electrochemical etching method for nickel-based alloys and their surface treatment, as well as an alkaline hydrogen electrolytic cell and its cathode electrode. The electrochemical etching conditions include: the etching solution is selected from at least one of KNO3 and HNO3; and the current density is 0.5–500 mA / cm². 2 The electrochemically etched nickel-based alloy obtained by this surface treatment method, when used as the cathode electrode of an alkaline hydrogen electrolyzer, is difficult to damage the electrode surface structure by reverse current and can effectively resist reverse current.

Description

Technical Field

[0001] This invention relates to the field of alkaline electrolytic hydrogen production technology, and particularly to electrochemically etched nickel-based alloys and their surface treatment methods, alkaline hydrogen production electrolytic cells and their cathode electrodes. Background Technology

[0002] Hydrogen, as a high-energy-density energy carrier, produces only water as a combustion byproduct, without generating sulfur, nitrogen, or greenhouse gases. Therefore, hydrogen is a clean fuel. Furthermore, hydrogen energy can be produced using renewable energy sources (such as wind and solar power) and can serve as an energy storage medium for wind and solar power, making it a core focus in the energy sector.

[0003] With the development of the green electricity hydrogen production industry, alkaline electrolyzers have become popular due to their mature technology and lower cost compared to PEM electrolyzers. The use of Raney nickel catalyst sprayed onto the surface of a nickel mesh in alkaline hydrogen electrolyzers to create catalytic electrodes is widely adopted; this method is primarily achieved through plasma spraying. However, during the spraying process, a significant amount of nickel-aluminum mixed powder is wasted, with only about 30% of the powder being sprayed onto the nickel mesh, resulting in a high nickel powder loss rate. This limits the potential for cost reduction in nickel mesh electrodes, making it difficult to further reduce equipment costs. Furthermore, during use, the reverse current generated by the start-up and shutdown of the electrolyzer (a phenomenon where current flows in the opposite direction to the expected direction when the positive electrode voltage is lower than the negative electrode voltage) can damage the Raney nickel structure on the electrode surface, leading to decreased electrode catalytic activity, increased voltage in the electrolyzer chamber, and poor resistance to reverse current.

[0004] Nickel mesh in alkaline hydrogen electrolyzers can also be obtained by chemical etching, a technique that removes materials using chemical reactions or physical impacts. However, chemical etching makes it difficult to control the surface uniformity of nickel-based alloy meshes and is slow.

[0005] Raney nickel, also known as Raney nickel, is a solid heterogeneous catalyst composed of fine-grained nickel-aluminum alloy with a porous structure. It is commonly used as a hydrogenation catalyst for organic compounds, particularly in the hydrogenation reduction reactions of aldehydes and ketones containing unsaturated bonds. However, Raney nickel is highly flammable when exposed to air, posing a certain degree of hazard. Therefore, a novel electrode preparation method is needed to reduce or eliminate the use of nickel powder, while simultaneously providing the electrode structure with excellent resistance to reverse current surges. Summary of the Invention

[0006] To address the technical problem of high nickel powder loss rate in the electrode fabrication process of existing technologies, this invention avoids the use of nickel powder and adopts an electrochemical etching method, proposing a nickel-based alloy electrode suitable for alkaline electrolytic cells and its preparation method.

[0007] In a first aspect, the present invention provides a surface treatment method for nickel-based alloys, which can effectively etch nickel-based alloys, and the resulting nickel-based alloys are suitable for use as cathode electrodes in alkaline electrolytic cells.

[0008] The technical solution of this invention is to treat the surface of a nickel-based alloy using electrochemical etching; the nickel-based alloy is a mesh; the conditions for electrochemical etching include: the etching solution is selected from at least one of KNO3 and HNO3; the current density is 0.5–500 mA / cm². 2 .

[0009] As a preferred technical solution, the concentration of KNO3 is 1–3 mol / L.

[0010] As a preferred technical solution, the concentration of HNO3 is 0.1–2 mol / L.

[0011] As a preferred technical solution, the nickel-based alloy is composed of Ni and other metallic elements, wherein the other metallic elements are selected from at least one of Mn, Fe, Co, Mo, Cr, and W.

[0012] As a preferred technical solution, in the nickel-based alloy, Ni accounts for 50% to 65% by weight; Cr accounts for 10% to 20% by weight; Mn accounts for 1% to 5% by weight; Fe accounts for 4% to 10% by weight; Mo accounts for 15% to 20% by weight; Co accounts for 1% to 3% by weight; and W accounts for 2% to 5% by weight.

[0013] As a preferred technical solution, in the nickel-based alloy, Ni accounts for 57% by weight; Cr accounts for 15% by weight; Mn accounts for 1% by weight; Fe accounts for 5% by weight; Mo accounts for 15% by weight; Co accounts for 2.5% by weight; and W accounts for 4.5% by weight.

[0014] As a preferred technical solution, the nickel-based alloy is one or more of nickel wire braided mesh, nickel plate stretched mesh, nickel plate perforated mesh, and nickel foam, and more preferably, nickel-based alloy nickel plate stretched mesh.

[0015] As a preferred technical solution, the nickel-based alloy is a nickel-based alloy mesh, and the thickness of the nickel-based alloy mesh includes, but is not limited to, 0.3mm, 0.6mm, 1mm, and 1.5mm; more preferably, the plate thickness is selected as 0.6mm.

[0016] As a preferred technical solution, the aperture width of the nickel-based alloy mesh includes, but is not limited to, 0.5 mm, 1 mm, and 3 mm; more preferably, the aperture width is 3 mm.

[0017] As a preferred technical solution, after the nickel-based alloy is polished and cleaned, it is placed in an etching solution, connected to the positive terminal of the power supply, and subjected to electrochemical etching treatment.

[0018] As a preferred technical solution, the grinding is performed by using a sandblasting machine to grind the surface of the nickel-based alloy; the sandblasting speed is 10-40 m / s, preferably 20 m / s;

[0019] As a preferred technical solution, the cleaning process involves first cleaning the nickel-based alloy with an alkaline solution, and then cleaning the nickel-based alloy with deionized water; the alkaline solution is selected from one or more of potassium hydroxide and sodium hydroxide, and the concentration is 1-10 mol / L.

[0020] As a preferred technical solution, the surface treatment method includes the following steps:

[0021] S1 polishing;

[0022] S2 Cleaning I;

[0023] S3 electrochemical etching;

[0024] S4 Cleans the electrochemically etched nickel-based alloy with deionized water; S5 Drys the cleaned nickel-based alloy at a temperature of 25–85°C.

[0025] The conductivity of the deionized water is ≤0.1 μS / cm.

[0026] In a second aspect, the present invention provides an electrochemically etched nickel-based alloy obtained by any of the surface treatment methods described in the first aspect.

[0027] Thirdly, the present invention provides a cathode electrode for an alkaline hydrogen production electrolyzer, wherein the cathode electrode is made of a nickel-based alloy subjected to electrochemical etching as described in the second aspect of the present invention. This electrode does not use nickel powder or plasma spraying, thus avoiding the use of nickel powder in the electrode preparation process and effectively reducing the cost of electrode preparation.

[0028] Fourthly, the present invention provides an alkaline hydrogen production electrolyzer, including the cathode electrode described in the third aspect of the present invention.

[0029] To address the technical problem of poor reverse current resistance of electrode surface structures in existing technologies, this invention performs surface treatment on nickel-based alloys, making it difficult for reverse current to damage the electrode surface structure and effectively resisting reverse current. Attached Figure Description

[0030] Figure 1 This is a flowchart of the method for preparing the nickel-based alloy mesh by electrochemical etching according to the present invention;

[0031] Figure 2 SEM image of the electrochemically etched nickel-based alloy mesh obtained in Example 4;

[0032] Figure 3This is a comparison diagram of current density and cell voltage in the electrolytic cell for comparative examples and embodiments. Detailed Implementation

[0033] The present invention will be further described below with reference to specific embodiments, but this does not constitute any limitation on the present invention.

[0034] The electrochemical etching method employed in this invention utilizes chemical reactions and charge transport for material processing. Its basic principle is to use an external electric field to cause electrons and ions to move within an electrolyte solution or electrolyte membrane, thereby generating a series of electrochemical reactions on the metal surface. Atoms or molecules undergo redox reactions to form corrosion products, ultimately achieving the processing of the metal surface.

[0035] The method for preparing the above-mentioned novel electrode includes the following steps:

[0036] The steps of the electrochemical etching method used are as follows:

[0037] Step 1: Sandblasting and polishing. Use a sandblasting machine to polish the surface of the nickel-based alloy mesh. The initial sandblasting speed is 10-40 m / s, more preferably 20 m / s.

[0038] Step 2: Surface cleaning. Use an alkaline solution to clean the surface of the nickel-based alloy mesh (which is composed of Ni and other metal elements, including but not limited to one or more of Mn, Fe, Co, Mo, Cr, and W) to remove residual stains. Then, use deionized water to clean the surface of the nickel-based alloy mesh to remove residual alkaline solution. The alkaline solution includes, but is not limited to, one or more of potassium hydroxide and sodium hydroxide, with a concentration of 1–10 mol / L, 2–9 mol / L, 3–7 mol / L, and more preferably 4–6 mol / L of potassium hydroxide.

[0039] Step 3: Electrochemical etching. The nickel-based alloy mesh is immersed in the etching solution, and the mesh is connected to the positive terminal of a power supply for etching. The etching solution consists of one or more of the following: 1–3 mol / L KNO3 and 0.1–2 mol / L HNO3. After connecting the power supply, the current density is 0.5–500 mA / cm². 2 ;

[0040] Step 4: Cleaning. Use deionized water to clean the treated multi-component nickel-based alloy mesh.

[0041] Step 5: Drying. Dry the cleaned nickel-based alloy mesh at a temperature of 25–85°C.

[0042] In steps two and four, the conductivity of deionized water is ≤0.1 μS / cm.

[0043] The instruments and materials used in the embodiments and comparative examples of this invention are described below.

[0044] Nickel-based alloy mesh: A stretched nickel plate mesh composed of nickel as the base and other elements. The weight percentage of Ni is 57%; Cr is 15%; Mn is 1%; Fe is 5%; Mo is 15%; Co is 2.5%; and W is 4.5%.

[0045] The nickel-based alloy used in this embodiment of the invention was purchased online from Danyang Xinli Alloy, and its model is Hastelloy C-276.

[0046] Comparative Example

[0047] Plasma spraying is a technology for strengthening and modifying material surfaces, enabling substrate surfaces to possess properties such as wear resistance, corrosion resistance, high-temperature oxidation resistance, electrical insulation, heat insulation, radiation protection, friction reduction, and sealing. Plasma spraying technology uses a plasma arc driven by direct current as a heat source to heat materials such as ceramics, alloys, and metals to a molten or semi-molten state, and then sprays them at high speed onto the pre-treated workpiece surface to form a firmly adhered surface layer.

[0048] A plasma-sprayed nickel mesh was obtained by using a nickel-based alloy wire mesh with a thickness of 0.6 mm and a hole width of 3 mm, and the metal powder used for spraying consisted of 80% nickel powder and 20% aluminum powder.

[0049] Step 1: Sandblasting and polishing. Use a sandblasting machine to polish the surface of the nickel-based alloy mesh. The initial sandblasting speed is 20m / s.

[0050] Step 2: Mixing. Use a mixer to mix 80% nickel powder and 20% aluminum powder at a speed of 25 rpm.

[0051] Step 3: Plasma spraying. Use plasma spraying equipment to spray the nickel-based alloy mesh. The working voltage of the spray gun is 710V, the working current is 55A, the spray gun movement speed is 750mm / min, and the spray gun angle is 90°.

[0052] Step 4: Activation. Immerse the coated electrode in a 20wt% KOH solution at 60℃ for 24 hours to activate and create pores.

[0053] Step 5: Cleaning and drying. Clean the activated pore-forming electrode with deionized water with a conductivity of 0.1 μS / cm, and then dry it at 80°C.

[0054] Example 1

[0055] An electrochemical etching method was used, employing a nickel-based alloy mesh with a plate thickness of 0.6 mm and a hole width of 3 mm. The etching solution consisted of 1 mol / L KNO3 and 0.2 mol / L HNO3.

[0056] Step 1: Sandblasting and polishing. Use a sandblasting machine to polish the surface of the nickel-based alloy mesh. The initial sandblasting speed is 20m / s.

[0057] Step 2: Surface cleaning. Use alkaline solution (6 mol / L potassium hydroxide) to clean the surface of the nickel-based alloy mesh to remove residual stains. Then use deionized water (0.1 μS / cm conductivity) to clean the surface of the multi-element nickel-based alloy mesh to remove residual alkaline solution.

[0058] Step 3: Electrochemical etching. The nickel-based alloy mesh is immersed in an etching solution (composed of 1 mol / L KNO3 and 0.2 mol / L HNO3). The nickel-based alloy mesh is connected to the positive terminal of a power supply for etching. The current density is 50 mA / cm². 2 Etching time: 5 minutes;

[0059] Step 4: Cleaning. Clean the treated nickel-based alloy mesh with deionized water (conductivity 0.1 μS / cm).

[0060] Step 5: Drying. Dry the cleaned nickel-based alloy mesh at 80°C to obtain the electrochemically etched nickel-based alloy mesh.

[0061] Example 2

[0062] An electrochemical etching method was used, employing a nickel-based alloy mesh with a plate thickness of 0.6 mm and a hole width of 3 mm. The etching solution consisted of 1 mol / L KNO3 and 0.5 mol / L HNO3.

[0063] Step 1: Sandblasting and polishing. Use a sandblasting machine to polish the surface of the nickel-based alloy mesh. The initial sandblasting speed is 20m / s.

[0064] Step 2: Surface cleaning. Use alkaline solution (6 mol / L potassium hydroxide) to clean the surface of the nickel-based alloy mesh to remove residual stains. Then use deionized water (0.1 μS / cm conductivity) to clean the surface of the nickel-based alloy mesh to remove residual alkaline solution.

[0065] Step 3: Electrochemical etching. The nickel-based alloy mesh is immersed in an etching solution (composed of 1 mol / L KNO3 and 0.5 mol / L HNO3). The nickel-based alloy mesh is connected to the positive terminal of a power supply for etching. The current density is 100 mA / cm². 2 Etching time: 10 minutes;

[0066] Step 4: Cleaning. Clean the treated nickel-based alloy mesh with deionized water (conductivity 0.1 μS / cm).

[0067] Step 5: Drying. Dry the cleaned nickel-based alloy mesh at 80°C to obtain the electrochemically etched nickel-based alloy mesh.

[0068] Example 3

[0069] An electrochemical etching method was used, employing a nickel-based alloy mesh with a plate thickness of 0.6 mm and a hole width of 3 mm. The etching solution consisted of 2 mol / L KNO3 and 0.2 mol / L HNO3.

[0070] Step 1: Sandblasting and polishing. Use a sandblasting machine to polish the surface of the nickel-based alloy mesh. The initial sandblasting speed is 20m / s.

[0071] Step 2: Surface cleaning. Use alkaline solution (6 mol / L potassium hydroxide) to clean the surface of the nickel-based alloy mesh to remove residual stains. Then use deionized water (0.1 μS / cm conductivity) to clean the surface of the nickel-based alloy mesh to remove residual alkaline solution.

[0072] Step 3: Electrochemical etching. The multi-component nickel-based alloy mesh is immersed in an etching solution (composed of 2 mol / L KNO3 and 0.2 mol / L HNO3). The nickel-based alloy mesh is connected to the positive terminal of a power supply for etching. The current density is 50 mA / cm². 2 Etching time: 20 minutes;

[0073] Step 4: Cleaning. Clean the treated nickel-based alloy mesh with deionized water (conductivity 0.1 μS / cm).

[0074] Step 5: Drying. Dry the cleaned nickel-based alloy mesh at 80°C to obtain the electrochemically etched nickel-based alloy mesh.

[0075] Example 4

[0076] An electrochemical etching method was used, employing a nickel-based alloy mesh with a plate thickness of 0.6 mm and a hole width of 3 mm. The etching solution consisted of 2 mol / L KNO3 and 0.2 mol / L HNO3.

[0077] Step 1: Sandblasting and polishing. Use a sandblasting machine to polish the surface of the nickel-based alloy mesh. The initial sandblasting speed is 20m / s.

[0078] Step 2: Surface cleaning. Use alkaline solution (6 mol / L potassium hydroxide) to clean the surface of the nickel-based alloy mesh to remove residual stains. Then use deionized water (0.1 μS / cm conductivity) to clean the surface of the multi-element nickel-based alloy wire mesh to remove residual alkaline solution.

[0079] Step 3: Electrochemical etching. The nickel-based alloy mesh is immersed in an etching solution (composed of 2 mol / L KNO3 and 0.2 mol / L HNO3). The nickel-based alloy mesh is connected to the positive terminal of a power supply for etching. The current density is 150 mA / cm². 2 Etching time: 15 minutes;

[0080] Step 4: Cleaning. Clean the treated nickel-based alloy mesh with deionized water (conductivity 0.1 μS / cm).

[0081] Step 5: Drying. The cleaned multi-component nickel-based alloy wire mesh is dried at 80°C to obtain an electrochemically etched nickel-based alloy wire mesh.

[0082] Test case

[0083] Electrochemical tests were conducted on the plasma-sprayed nickel mesh prepared in Comparative Example 1, and the electrochemically etched nickel-based alloy meshes prepared in Examples 1, 2, 3, and 4. Hg / HgO was used as the reference electrode, a graphite electrode as the counter electrode, and a 1 mol / L KOH solution as the electrolyte. The hydrogen evolution overpotential (HHE) of the cathode electrode was measured using a Chenhua CHI 660E electrochemical workstation. The HHE was converted to a relative value for the reversible hydrogen electrode using the formula EvsRHE = EvsHg / HgO + 0.098 + 0.059 × pH. The calculated value was based on the actual pH of the 30 wt% KOH solution, using the formula EvsRHE = EvsHg / HgO + 0.986. The cathode electrode underwent 1000 CV cycles within the range of -1.4 to +0.6 V (vs Hg / HgO), and the electrode overpotential after each CV cycle was measured. The electrode was installed in a small alkaline electrolytic cell for testing. The electrolyte was a 30 wt% KOH solution, and the effective active area of ​​the electrode was 0.0314 m². 2 Test current density 2500A / m 2 3000A / m 2 3500A / m 2 4000A / m 2 The voltage of the small chamber below.

[0084] Table 1

[0085]

[0086] Table 1 shows that the overpotential of the ion-sprayed nickel mesh prepared in Comparative Example 1 increased by 41 mV after multiple CV cycles, which is significantly higher than that of the Example 1. The nickel-based alloy mesh electrodes prepared by electrochemical etching in Examples 1, 2, 3, and 4 of this invention showed an increase in overpotential after multiple CV cycles. The resistance to reverse current is significantly lower than that of the comparative example, indicating better performance. In the electrolytic cell test, the nickel-based alloy mesh electrodes prepared by electrochemical etching in Examples 2, 3, and 4 of this invention performed better at 2500 A / m. 2 Cell voltage at current density The voltage of the chamber is significantly lower than that of Comparative Example 1 (1.76V), indicating that the energy consumption is lower during the process of producing hydrogen by water electrolysis.

[0087] Any numerical value mentioned in this invention, if there is only a two-unit interval between any minimum and any maximum value, includes all values ​​that increase by one unit each time from the minimum to the maximum value. For example, if the amount of a component, or the value of a process variable such as temperature, pressure, or time, is stated as 50-90, in this specification it means specifically listing values ​​such as 51-89, 52-88... and 69-71 and 70-71. For non-integer values, it may be appropriately considered that a unit is 0.1, 0.01, 0.001, or 0.0001. These are merely some specifically specified examples. In this application, in a similar manner, all possible combinations of numerical values ​​between the listed minimum and maximum values ​​are considered to have been disclosed.

[0088] It should be noted that the embodiments described above are only for explaining the present invention and do not constitute any limitation on the present invention. The present invention has been described with reference to typical embodiments, but it should be understood that the words used therein are descriptive and explanatory terms, not limiting terms. Modifications can be made to the present invention within the scope of the claims, and revisions can be made to the present invention without departing from the scope and spirit of the present invention. Although the present invention described herein relates to specific methods, materials, and embodiments, it does not mean that the present invention is limited to the specific examples disclosed herein; on the contrary, the present invention can be extended to all other methods and applications with the same function.

Claims

1. A surface treatment method for nickel-based alloys, characterized in that, Electrochemical etching was used to treat the surface of nickel-based alloys; The nickel-based alloy is in the form of a mesh; The conditions for electrochemical etching include: The etching solution is selected from at least one of KNO3 and HNO3; Current density is 0.5–500 mA / cm² 2 .

2. The surface treatment method for nickel-based alloys according to claim 1, characterized in that, The concentration of KNO3 is 1–3 mol / L; And / or, the concentration of HNO3 is 0.1–2 mol / L.

3. The surface treatment method for nickel-based alloys according to claim 1 or 2, characterized in that, The nickel-based alloy is composed of Ni and other metallic elements, wherein the other metallic elements are selected from at least one of Mn, Fe, Co, Mo, Cr, and W; Preferably, in the nickel-based alloy, Ni accounts for 50% to 65% by weight; Cr accounts for 10% to 20% by weight; Mn accounts for 1% to 5% by weight; Fe accounts for 4% to 10% by weight; Mo accounts for 15% to 20% by weight; Co accounts for 1% to 3% by weight; and W accounts for 2% to 5% by weight. And / or, in the nickel-based alloy, Ni accounts for 57% by weight; Cr accounts for 15% by weight; Mn accounts for 1% by weight; Fe accounts for 5% by weight; Mo accounts for 15% by weight; Co accounts for 2.5% by weight; and W accounts for 4.5% by weight.

4. The surface treatment method for nickel-based alloys according to any one of claims 1-3, characterized in that, The nickel-based alloy is one or more of the following: nickel wire braided mesh, nickel plate stretched mesh, nickel plate perforated mesh, and nickel foam.

5. The surface treatment method for nickel-based alloys according to any one of claims 1-4, characterized in that, After being polished and cleaned, the nickel-based alloy is placed in an etching solution, and the positive terminal of the power supply is turned on for electrochemical etching.

6. The surface treatment method for nickel-based alloys according to claim 5, characterized in that, The grinding is performed by using a sandblasting machine to grind the surface of the nickel-based alloy; the sandblasting speed is 10-40 m / s, preferably 20 m / s; And / or, the cleaning I involves first cleaning the nickel-based alloy with an alkaline solution, and then cleaning the nickel-based alloy with deionized water; the alkaline solution is selected from one or more of potassium hydroxide and sodium hydroxide, and the concentration is 1-10 mol / L.

7. The surface treatment method for nickel-based alloys according to any one of claims 1-6, characterized in that, The surface treatment method includes the following steps: S1 polishing; S2 Cleaning I; S3 electrochemical etching; S4 Cleans the electrochemically etched nickel-based alloy with deionized water (II); S5 involves drying the cleaned nickel-based alloy at a temperature of 25–85°C.

8. The nickel-based alloy obtained by the surface treatment method according to any one of claims 1-7 through electrochemical etching.

9. The cathode electrode of an alkaline hydrogen production electrolyzer, characterized in that, The cathode electrode is made of the nickel-based alloy etched by electrochemical etching as described in claim 8.

10. An alkaline hydrogen production electrolyzer, characterized in that, Includes the cathode electrode as described in claim 9.

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