NiCu alloy electrode preparation method based on electrochemical micromachining and electric crystallization coordinated regulation

Abstract

The invention discloses a NiCu alloy electrode preparation method based on electrochemical micromachining and electro-crystallization coordinated regulation and control, which comprises the following steps: (1) electrochemical micromachining: cutting a nickel net, clamping the longer end of the nickel net by using an electrode clamp with a platinum sheet, ensuring the effective area of an electrode immersed in an electrolyte, electrifying the nickel net in an acid solution, and carrying out electrochemical micromachining on the nickel net; cleaning and drying for later use; and (2) Ni-Cu gradient crystallization is conducted, specifically, nickel crystallization is conducted firstly, then copper crystallization is conducted, a Ni-rich compact bottom layer is formed in the initial stage of crystallization, a Ni-Cu mixed columnar crystal transition layer is formed in the middle stage of crystallization, and a Cu-rich nano dendritic crystal surface layer is formed in the later stage of crystallization. According to the preparation method, a multi-scale micro-nano composite structure is constructed through electrochemical micromachining, a micron framework-nano dendritic crystal composite structure is formed through Ni-Cu gradient crystallization, micron-scale gaps generated by electrochemical micromachining are filled, the NiCu alloy interface characteristics are optimized, the electro-catalytic performance is remarkably improved, and the method is close to a precious metal platinum catalyst.

Description

Technical Field

[0001] The present invention relates to the technical field of electrocatalytic materials, and particularly relates to a preparation method of a NiCu alloy electrode based on the synergistic regulation of electrochemical micromachining and electrocrystallization. Background Art

[0002] As a clean energy, hydrogen energy has the characteristics of high efficiency and no pollution. Due to the unique characteristics of hydrogen, high efficiency, almost no pollution, and the ability to produce high-purity hydrogen, it has attracted great research interest. There are different methods for hydrogen production. Among them, electrochemical water splitting for hydrogen production is an important and common method for clean hydrogen production. In this method, the hydrogen evolution reaction (HER) occurs at the cathode, and the oxygen evolution reaction (OER) occurs at the anode. The hydrogen evolution reaction (HER) is one of the key steps in water splitting.

[0003] Appropriate electrocatalytic activity and active surface area are the main parameter conditions for realizing electrocatalytic HER activity. At present, platinum group metals (such as Pt, Ru, Ir, and Rh, etc.) are recognized as efficient HER catalysts. However, due to their limited uses, high costs, and weak stability, their large-scale applications are restricted. Therefore, replacing this group of noble metal-based catalysts with suitable metals with low cost and high efficiency is the focus of current research.

[0004] Nickel-copper alloy (NiCu) is considered a potential alternative material due to its good catalytic performance and stability. However, the existing catalytic performance of NiCu alloy is still inferior to that of platinum catalysts. Therefore, how to improve the electrochemical performance of NiCu alloy by optimizing the preparation process has become the focus of current research. Summary of the Invention

[0005] Aiming at the deficiencies of the existing technology, the purpose of the present invention is to provide a preparation method of a NiCu alloy electrode based on the synergistic regulation of electrochemical micromachining and electrocrystallization. Through the technology combining electrochemical micromachining and electrocrystallization, precise regulation of the surface microstructure of the two-step coordination of micromachining-crystallization is realized. Not only the precise design of the surface morphology is achieved, but also the catalytic performance of the electrode is significantly improved through the coupling effect of the multi-level structure, narrowing the gap with platinum catalysts.

[0006] In order to achieve the above purpose, the technical solution adopted by the present invention is as follows: A preparation method of a NiCu alloy electrode based on the synergistic regulation of electrochemical micromachining and electrocrystallization, comprising the following steps:

[0007] (1) Electrochemical micromachining: Cut the nickel mesh, use an electrode clip with a platinum sheet to clamp the longer end, ensure the effective area of the electrode immersed in the electrolyte, energize the nickel mesh in an acidic solution, and after cleaning, dry it for standby;

[0008] (2) Ni-Cu gradient crystallization: First, nickel crystallization is carried out, followed by copper crystallization. At the initial stage of crystallization, a dense bottom layer rich in Ni is formed. In the middle stage, a columnar crystal transition layer of Ni-Cu mixture is formed. In the later stage, a nanodendrite surface layer rich in Cu is formed.

[0009] As a preferred solution, the size of the nickel mesh cut in the step (1) is 1×1.2 cm 2 , and the effective area of the electrode immersed in the electrolyte during testing is 1 cm 2 , and the nickel mesh is energized in a 0.5 mol / L H 2 SO 4 solution for 30 min, and the current is 0.05 A.

[0010] As a preferred solution, the Ni-Cu gradient crystallization in the step (2) is specifically the first electrocrystallization and the second electrocrystallization. In the first electrocrystallization, the nickel mesh is used as the working electrode, platinum is used as the counter electrode and reference electrode, and a layer of Ni is crystallized on the nickel mesh by using the three-electrode method. In the second electrocrystallization, the nickel mesh after the first electrocrystallization is used as the working electrode, the graphite rod is used as the counter electrode, and Ag / AgCl is used as the reference electrode to crystallize Cu.

[0011] As a preferred solution, the experimental conditions for the first electrocrystallization are: the electrolyte includes 0.5 - 1.5 mol / L NiCl 2 ·6H 2 O, 0.5 mol / L H 3 BO 3 and 1.5 mol / L ethylenediamine hydrochloride, the experimental current is 0.01 - 0.1 A, the temperature is 10 - 70 °C, the pH value of the electrolyte is maintained at 4.2 ± 0.1, and the time is 15 min.

[0012] As a preferred solution, the experimental conditions for the first electrocrystallization are: the Ni 2+ concentration is 1.0 mol / L, the temperature is 50 °C, the current is 0.1 A, and the time is 15 min.

[0013] As a preferred solution, in the first electrocrystallization, the influence of the experimental conditions of Ni 2+ concentration, temperature, and current on the hydrogen evolution reaction (HER) is evaluated by the double-layer capacitance (Cdl) and the Tafel slope (Tafel), where the double-layer capacitance is 18.2 - 36.4 mF*cm -2 , and the Tafel slope is 98.3 - 123.8 mV*dec -1 .

[0014] As a preferred solution, the experimental conditions for the second electrocrystallization are: the electrolyte includes 0.1 - 0.2 mol / L CuSO 4 ·5H 2O, 0.5 mol / L Na 3 C 6 H 5 O 7 (sodium citrate), the experimental current is 0.01 - 0.1 A, the temperature is 10 - 50 °C, the pH value of the electrolyte is maintained at 4.2 ± 0.1, and the time is 15 min.

[0015] As a preferred embodiment, the experimental conditions for the second-step electrocrystallization are: Cu 2+ The concentration is 0.15 mol / L, the temperature is 50 °C, the current is 0.1 A, and the time is 15 min.

[0016] As a preferred embodiment, in the second-step electrocrystallization, the experimental conditions of the Cu 2+ concentration, temperature, and current on the hydrogen evolution reaction (HER) are evaluated by the double-layer capacitance (Cdl) and the Tafel slope (Tafel), where the double-layer capacitance is 23.5 - 38.5 mF*cm -2 , and the Tafel slope is 82.1 - 124.2 mV*dec -1 .

[0017] As a preferred embodiment, the nickel mesh is electrochemically micro-machined in a 0.5 mol / L H 2 SO 4 solution with a current of 0.05 A for 30 min, and then the first-step electrocrystallization is carried out. The first-step crystallization conditions are: the electrolyte includes 1.0 mol / L NiCl 2 ·6H 2 O, 0.5 mol / L H 3 BO 3 and 1.5 mol / L ethylenediamine hydrochloride. The experimental current is 0.1 A, the temperature is 50 °C, and the time is 15 min; after obtaining the sample, the second-step electrocrystallization is carried out. The second-step crystallization conditions are: the electrolyte includes 0.15 mol / L CuSO 4 ·5H 2 O, 0.5 mol / L Na 3 C 6 H 5 O 7 (sodium citrate), the experimental current is 0.1 A, the temperature is 50 °C, and the time is 15 min; the double-layer capacitance of the obtained NiCu alloy after electrochemical testing is 38.5 mF*cm -2 , and the Tafel slope is 82.1 mV*dec -1 .

[0018] Compared with the prior art, the beneficial effects of the present invention: The NiCu alloy prepared by the experimental method of the present invention has a double-layer capacitance (Cdl) of 38.5 mF*cm-2 , which is nearly 8 times that of the original nickel mesh, and the Tafel slope is 82.1 mV*dec -1 , which is nearly 40% lower than that of the original nickel mesh, significantly superior to traditional NiCu alloys, and close to the performance of platinum catalysts (the Tafel slope is 43 mV*dec -1 ), greatly narrowing the gap with platinum catalytic performance. The present invention significantly improves the electrocatalytic performance of NiCu alloys and reduces costs through a technology combining electrochemical microfabrication and electrodeposition. Detailed implementation manners

[0019] The present invention will be further described below in conjunction with specific embodiments. The following embodiments are only used to more clearly illustrate the technical solutions of the present invention and cannot be used to limit the protection scope of the present invention.

[0020] Embodiment 1:

[0021] A preparation method of a NiCu alloy electrode based on the synergistic regulation of electrochemical microfabrication and electrodeposition, comprising the following steps:

[0022] (1) Electrochemical microfabrication: Cut the nickel mesh into a size of 1×1.2 cm 2 , clamp the longer end with an electrode clip with a platinum sheet, ensure that the effective area of the electrode immersed in the electrolyte is 1 cm 2 , place the nickel mesh in a 0.5 mol / L H 2 SO 4 solution and energize it for 30 min with a current of 0.05 A, then clean it with an ultrasonic cleaner and dry it for standby;

[0023] (2) First electrodeposition: Use the nickel mesh as the working electrode, platinum as the counter electrode and reference electrode, and deposit a layer of Ni on the nickel mesh by the three-electrode method; the electrolyte includes 1.0 mol / L NiCl 2 ·6H 2 O, 0.5 mol / L H 3 BO 3 and 1.5 mol / L ethylenediamine hydrochloride, the experimental current is 0.01 A, the temperature is 10 °C, the pH value of the electrolyte is maintained at 4.2±0.1, and the time is 15 min;

[0024] (3) Second electrodeposition: Use the nickel mesh after the first electrodeposition as the working electrode, a graphite rod as the counter electrode, and Ag / AgCl as the reference electrode to deposit Cu; the electrolyte includes 0.15 mol / L CuSO 4 ·5H 2 O, 0.5 mol / L Na 3 C 6 H 5 O 7(Sodium citrate), the experimental current is 0.01 A, the temperature is 10 °C, the pH value of the electrolyte is maintained at 4.2 ± 0.1, and the time is 15 min.

[0025] Furthermore, change the experimental conditions of the first electrocrystallization in step (2):

[0026] (a) Ni 2+ Effect of concentration on HER: To compare the hydrogen evolution activities of samples at different Ni + concentrations, three-electrode alkaline electrolysis tests were carried out on nickel electrodes at three concentrations respectively. Table 1 shows the double-layer capacitance (Cdl) and Tafel slope of samples at different Ni 2 concentrations;

[0027] Table 1

[0028]

[0029] (b) Effect of temperature on HER: Under the conditions of (a), keep other conditions unchanged and compare the hydrogen evolution activities of samples at different temperatures. The results are shown in Table 2;

[0030] Table 2

[0031]

[0032] (c) Effect of current on HER: Under the conditions of (b), keep other conditions unchanged and compare the hydrogen evolution activities of samples at different currents. The results are shown in Table 3;

[0033] Table 3

[0034]

[0035]

[0036] Even further, change the experimental conditions of the second electrocrystallization in step (3):

[0037] (d) Cu 2+ Effect of concentration on HER: The change in the Cu 2+ concentration in the deposition solution will affect the composition of nickel and copper in the NiCu alloy electrode to a certain extent. To compare the hydrogen evolution activities of samples at different Cu 2+ concentrations, under the conditions of a current of 0.01 A, a temperature of 10 °C, and a time of 15 min, the concentrations were set to 0.1 mol / L, 0.15 mol / L, and 0.2 mol / L respectively. The effect of the Cu 2+ concentration on the catalytic performance of the NiCu alloy electrode was studied through hydrogen evolution performance tests in an alkaline electrolytic cell. The results are shown in Table 4;

[0038] Table 4

[0039]

[0040] (e) Influence of temperature on HER: An increase in temperature can accelerate the diffusion of ions in the deposition solution, reduce concentration polarization, increase the conductivity of the solution, reduce pinholes, and improve the quality of the NiCu alloy coating. Therefore, under the condition of the optimal Cu 2+ concentration, while keeping other experimental parameters unchanged, the experimental temperature was changed to 10 °C (ice-water bath), 30 °C (room temperature), and 50 °C (water bath heating), and the hydrogen evolution performance of the alkaline electrolytic cell was used for research. The results are shown in Table 5;

[0041] Table 5

[0042]

[0043]

[0044] (f) Influence of current on HER: The current density mainly has a greater influence on the fineness of the coating crystallization. Therefore, under the conditions of (e), the hydrogen evolution activities of samples under different currents were compared. The results are shown in Table 6;

[0045] Table 6

[0046] Sample 1 2 <![CDATA[Cu 2+ Concentration / mol*L -1 > 0.15 0.15 Temperature / °C 50 50 Current / A 0.01 0.1 <![CDATA[Double-layer capacitance (Cdl) / mF*cm -2 > 33.4 38.5 <![CDATA[Tafel slope / mV*dec -1 > 100.6 82.1

[0047] Preferably, the platinum electrode was placed under the condition of 30 wt% KOH electrolyte for HER testing and compared with the current sample. The results are shown in Table 7.

[0048] Table 7

[0049]

[0050] In summary, after the nickel mesh was electrochemically micromachined in a 0.5 mol / L H 2 SO 4 solution with a current of 0.05 A for 30 min, the first-step electrocrystallization was carried out. The conditions for the first-step crystallization were as follows: the electrolyte included 1.0 mol / L NiCl 2 ·6H 2 O, 0.5 mol / L H 3 BO 3 and 1.5 mol / L ethylenediamine hydrochloride. The experimental current was 0.1 A, the temperature was 50 °C, and the time was 15 min; after obtaining the sample, the second-step electrocrystallization was carried out. The conditions for the second-step crystallization were as follows: the electrolyte included 0.15 mol / L CuSO 4 ·5H 2 O, 0.5 mol / L Na 3 C 6 H 5 O7 (Sodium citrate), the experimental current was 0.1 A, the temperature was 50 °C, and the time was 15 min; the double-layer capacitance of the NiCu alloy after electrochemical testing was 38.5 mF*cm -2 , which was nearly 8 times that of the original nickel mesh, and the Tafel slope was 82.1 mV*dec -1 , which was nearly 40% lower than that of the original nickel mesh, greatly narrowing the gap with the catalytic performance of platinum.

[0051] Therefore, the test method of the present invention is different from the conventional electro-deposition method for preparing electrodes. The present invention uses a method combining electrochemical microfabrication and electrocrystallization to prepare a NiCu alloy electrode. Electrochemical microfabrication refers to the process of making different microstructural patterns on the surface of a nickel mesh by applying a current, and electrocrystallization refers to the process of passing a current through an electrolyte to reduce metal cations in the electrolyte and grow them on the surface of the nickel mesh. The introduction of electrochemical microfabrication constructs a micro-nano composite structure on the surface of the nickel electrode, thereby increasing the specific surface area of the nickel electrode, providing more electrochemically active sites for the next electrocrystallization, and improving the electrochemical performance of the NiCu alloy. Moreover, on this basis, by precisely controlling the electrocrystallization process, the Ni-Cu gradient crystallization method is used to achieve fine regulation of the surface microstructure through two-step coordination of microfabrication and crystallization for the sub-micron-level fine modification of the nickel substrate after microfabrication. That is, first, microfabrication constructs a micron-scale skeleton structure on the electrode surface, and then the electrocrystallization process uses these structures as a substrate to induce the growth of dendritic nanostructures, forming a composite structure of micron-scale skeleton-nanodendrites. The gradient deposition sequence of Ni-Cu (Ni first and then Cu) and precise pH regulation (maintained at 4.2 ± 0.1) and temperature regulation (50 °C ± 0.5 °C) are crucial for forming an ideal crystal orientation. In particular, a large current of 0.1 A is used for short-time secondary electrocrystallization to induce the in-situ growth of unique dendritic nanostructures, which fill the sub-micron-level voids generated by microfabrication. This experimental method for synergistically constructing a multi-level structure of the present invention not only optimizes the interfacial properties of the NiCu alloy, but also significantly improves its electrocatalytic performance, greatly narrowing the performance gap with noble metal platinum catalysts.

[0052] The above is only the preferred embodiment of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the technical principle of the present invention, several improvements and deformations can be made, and these improvements and deformations should also be regarded as the protection scope of the present invention.

Claims

1. A method for preparing a NiCu alloy electrode based on coordinated control of electrochemical micromachining and electrocrystallization, characterized in that: The following steps are involved: (1) Electrochemical micromachining: Cut the nickel mesh and clamp the longer end of the mesh with an electrode clamp with a platinum sheet to ensure that the effective area of ​​the electrode is immersed in the electrolyte. Then, energize the nickel mesh in an acidic solution, clean it, and dry it for later use. (2) Ni-Cu gradient crystallization: nickel crystallization is performed first and then copper crystallization. In the early stage of crystallization, a dense Ni-rich bottom layer is formed, a Ni-Cu mixed columnar crystal transition layer is formed in the middle stage, and a Cu-rich nano-dendrite surface layer is formed in the later stage.

2. The method for preparing a NiCu alloy electrode based on coordinated control of electrochemical micromachining and electrocrystallization according to claim 1, characterized in that: The size of the nickel mesh cut in step (1) is 1×1.2 cm 2 During the test, the effective area of ​​the electrode immersed in the electrolyte is 1 cm 2 , the nickel mesh was electrified in a 0.5 mol / L H2SO4 solution for 30 min with a current of 0.05 A.

3. The method for preparing a NiCu alloy electrode based on coordinated control of electrochemical micromachining and electrocrystallization according to claim 1, characterized in that: The Ni-Cu gradient crystallization in step (2) specifically includes a first step of electrocrystallization and a second step of electrocrystallization, wherein the first step of electrocrystallization uses a nickel mesh as a working electrode, platinum as a counter electrode and a reference electrode, and a layer of Ni is crystallized on the nickel mesh using a three-electrode method, and the second step of electrocrystallization uses the nickel mesh that has undergone the first step of electrocrystallization as a working electrode, a graphite rod as a counter electrode, and Ag / AgCl as a reference electrode to crystallize Cu.

4. The method for preparing a NiCu alloy electrode based on coordinated control of electrochemical micromachining and electrocrystallization according to claim 3, characterized in that: The experimental conditions for the first step of electrocrystallization are: the electrolyte includes 0.5-1.5 mol / L NiCl2·6H2O, 0.5 mol / L H3BO3 and 1.5 mol / L ethylenediamine hydrochloride, the experimental current is 0.01-0.1 A, the temperature is 10-70° C., the pH value of the electrolyte is maintained at 4.2±0.1, and the time is 15 min.

5. The method for preparing a NiCu alloy electrode based on coordinated control of electrochemical micromachining and electrocrystallization according to claim 4, characterized in that: The experimental conditions of the first step of electrocrystallization are: Ni 2+ The concentration was 1.0 mol / L, the temperature was 50°C, the current was 0.1 A, and the time was 15 min.

6. The method for preparing a NiCu alloy electrode based on coordinated control of electrochemical micromachining and electrocrystallization according to claim 4, characterized in that: In the first step of electrocrystallization, Ni 2+ The effects of experimental conditions of concentration, temperature, and current on the hydrogen evolution reaction (HER) were evaluated by double layer capacitance (Cdl) and Tafel slope (Tafel), where the double layer capacitance is 18.2 to 36.4 mF*cm -2 , Tafel slope is 98.3~123.8mV*dec -1 .

7. The method for preparing a NiCu alloy electrode based on coordinated control of electrochemical micromachining and electrocrystallization according to claim 3, characterized in that: The experimental conditions for the second step of electrocrystallization are: the electrolyte includes 0.1-0.2 mol / L CuSO4·5H2O, 0.5 mol / L Na3C6H5O7 (sodium citrate), the experimental current is 0.01-0.1A, the temperature is 10-50°C, the pH value of the electrolyte is maintained at 4.2±0.1, and the time is 15 min.

8. The method for preparing a NiCu alloy electrode based on coordinated control of electrochemical micromachining and electrocrystallization according to claim 7, characterized in that: The experimental conditions of the second step electrocrystallization are: Cu 2+ The concentration is 0.15 mol / L, the temperature is 50°C, the current is 0.1A, and the time is 15 min.

9. The method for preparing a NiCu alloy electrode based on coordinated control of electrochemical micromachining and electrocrystallization according to claim 7, characterized in that: In the second step of electrocrystallization, Cu 2+ The effects of experimental conditions of concentration, temperature, and current on the hydrogen evolution reaction (HER) were evaluated by double layer capacitance (Cdl) and Tafel slope (Tafel), where the double layer capacitance is 23.5 to 38.5 mF*cm -2 , Tafel slope is 82.1~124.2mV*dec -1 .

10. The method for preparing a NiCu alloy electrode based on coordinated control of electrochemical micromachining and electrocrystallization according to claim 1, characterized in that: After the nickel mesh was electrochemically micro-machined in a 0.5 mol / L H2SO4 solution at a current of 0.05 A for 30 min, the first step of electrocrystallization was performed. The first step of crystallization conditions were: the electrolyte included 1.0 mol / L NiCl2·6H2O, 0.5 mol / L H3BO3 and 1.5 mol / L ethylenediamine hydrochloride, the experimental current was 0.1 A, the temperature was 50 °C, and the time was 15 min; After obtaining the sample, the second step of electrocrystallization was carried out. The conditions of the second step of crystallization were: the electrolyte included 0.15 mol / L CuSO4·5H2O and 0.5 mol / L Na3C6H5O7 (sodium citrate), the experimental current was 0.1A, the temperature was 50°C, and the time was 15 min. The double layer capacitance of the obtained NiCu alloy after electrochemical testing was 38.5 mF*cm -2 , the Tafel slope is 82.1mV*dec -1 .

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