A NiCu / MoO2 heterogeneous composite hydrogen evolution electrode based on an unalloying strategy and its preparation method
By preparing a heterojunction composite of MoO2 crystalline phase and NiCu alloy crystalline phase, the functional coupling bottleneck of Ni-Mo-Cu system catalyst was solved, and the kinetic optimization and stability improvement of alkaline HER reaction were achieved, breaking through the limitations of traditional alloying.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- CHONGQING UNIV
- Filing Date
- 2026-04-13
- Publication Date
- 2026-06-26
AI Technical Summary
In existing technologies, the catalytic performance of Ni-Mo-Cu system catalysts is limited by the functional coupling bottleneck caused by homogeneous alloying, making it difficult to simultaneously optimize the adsorption and dissociation of water molecules and the recombination and desorption of hydrogen intermediates. Conventional two-step processes cannot achieve nanoscale functional phase separation, resulting in limitations in alkaline HER kinetics.
A non-alloying strategy was adopted to prepare a heterojunction composite in which MoO2 crystal phase and NiCu alloy crystal phase coexist. Through a specific process, a thermodynamically stable phase with an independent crystal structure was formed, realizing the separation and synergy of water adsorption and dissociation functions and hydrogen intermediate recombination and desorption functions.
It significantly reduced the overpotential, decreased the Tafel slope, and improved catalytic activity and stability, exhibiting excellent resistance to component dissolution and long-term stability. The overpotential was reduced by more than 150 mV, the Tafel slope was reduced, and the performance degradation rate was less than 10% after 1500 hours of continuous operation at 1 A·cm-2.
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Abstract
Description
Technical Field
[0001] This invention relates to the field of composite electrode materials, specifically to a NiCu / MoO2 heterogeneous composite hydrogen evolution electrode based on a non-alloying strategy and its preparation method. Background Technology
[0002] The cathodic hydrogen evolution reaction (HER) for alkaline water electrolysis to produce hydrogen follows a unique "water-hydroxyl" reaction pathway, and its reaction kinetics are heavily dependent on the adsorption strength of reaction intermediates on the catalyst surface. This pathway mainly consists of two key elementary steps: First, water molecules are adsorbed and dissociated on the catalyst surface, generating adsorbed hydrogen intermediates (H) and hydroxyl ions (OH). - This step is usually called the Volmer step (H2O + e-). - →H+OH - Subsequently, H proceeds through the Heyrovsky step (H + H₃O + e⁻) - →H2+OH - The reaction proceeds via either the Tafel step (2H*→H2) to recombine and generate hydrogen gas, which then desorbs. In an alkaline medium, the initial reactants are water molecules rather than hydrated protons (H3O). + The dissociation of H+ requires high energy, therefore the Volmer step (dissociation of water) is often the rate-determining step of the entire reaction. Simultaneously, the adsorption of H+ needs to be moderate; too weak an adsorption will result in no adsorption, while too strong an adsorption will result in ineffective adsorption.
[0003] Existing technologies focus on preparing Ni-Mo-Cu ternary solid solution alloys through methods such as electroplating and co-deposition. The core idea of this approach is to seek a compromise optimization of the electronic structure through element blending within a single alloy phase, essentially falling under the category of traditional "alloying engineering." However, the active site properties on the surface of a single homogeneous catalyst tend to be similar, making it difficult to simultaneously optimize the activity of water molecules (and OH-)... -The adsorption / dissociation capacity of the active component and its adsorption / desorption capacity for hydrogen (H) are crucial factors. For example, Mo sites are favorable for water adsorption and dissociation, but often lead to excessive adsorption of H (the Gibbs free energy of hydrogen adsorption, |ΔG_H|, is negative), hindering subsequent recombination and desorption. Cu or Ni sites may have a more moderate adsorption capacity for H, but their ability to promote the dissociation of water molecules is weaker. This functional coupling bottleneck directly restricts its catalytic performance. In addition, to improve the macroscopic morphology, loading, or binding force of the electrode, two-step or multi-step methods are often used in the field to prepare coated electrodes. However, the final target product of such conventional two-step methods is still a homogeneous alloy phase or a mixed oxide / hydroxide. The process design has not, and has not been conceived of, actively guiding and precisely controlling the formation of independent phases with distinct crystal structures and catalytic functions in the final state of the active component. Therefore, a long-standing technical problem in this field is: how to break through the traditional compromise approach of alloying in the nickel-molybdenum-copper system, create a new composite catalytic structure that enables the "water adsorption and dissociation function" and "hydrogen intermediate recombination and desorption function" of the catalyst to be separated and specialized in space and phase, and achieve efficient synergy through a tight interface, thereby breaking through the kinetic limitations of basic HER from the perspective of reaction principle. Summary of the Invention
[0004] To address the aforementioned shortcomings of existing technologies, this invention provides a NiCu / MoO2 heterogeneous composite hydrogen evolution electrode based on a non-alloying strategy and its preparation method. This overcomes the inherent "functional coupling" defect of existing Ni-Mo-Cu system electrodes, which are limited to homogeneous alloys, and the shortcomings of conventional two-step processes, which can only improve the macroscopic structure but cannot achieve nanoscale "functional phase separation".
[0005] To achieve the above-mentioned objectives, the technical solution adopted by this invention is as follows: A NiCu / MoO2 heterogeneous composite hydrogen evolution electrode based on a non-alloying strategy is provided. The electrode is used for alkaline hydrogen evolution reaction. The electrode is a heterojunction composite in which MoO2 crystal phase and NiCu alloy crystal phase coexist. The MoO2 crystal phase and NiCu alloy crystal phase are respectively constructed as thermodynamically stable phases with independent crystal structures. The electrode can efficiently catalyze alkaline HER reaction.
[0006] This invention also provides a method for preparing the above-mentioned NiCu / MoO2 heterogeneous composite hydrogen evolution electrode based on an unalloying strategy, comprising the following specific steps: S1: Pretreatment of the nickel foam substrate is carried out by sequential acid washing, water washing and ultrasonic cleaning with ethanol. S2: The pretreated nickel foam substrate is immersed in a mixed solution of copper nitrate and sodium bicarbonate for hydrothermal reaction at a temperature of 100℃~200℃ for 4~10h; then calcined at 300℃ in air for 3h to obtain nickel foam with a CuO nanoneedle array intermediate layer grown on the surface. S3: The nickel foam containing the CuO interlayer obtained in S2 is immersed in a mixed solution of nickel nitrate, sodium molybdate and ammonium fluoride for hydrothermal reaction at a temperature of 100℃~200℃ for 4~10h. After the reaction is completed, it is dried and then calcined in a reducing atmosphere for 4h to obtain the NiCu / MoO2 heterogeneous composite hydrogen evolution electrode.
[0007] Furthermore, in step S2, the molar ratio of copper nitrate to sodium bicarbonate is 1:1, and the concentration of copper nitrate or sodium bicarbonate in the mixed solution is 0.0001~0.5 mol / L.
[0008] Furthermore, in step S3, the molar ratio of nickel nitrate, sodium molybdate, and ammonium fluoride is 1:1:1, and the concentration of nickel nitrate / sodium molybdate / ammonium fluoride in the mixed solution is 0.01~1 mol / L.
[0009] Furthermore, in step S3, the reducing atmosphere is a mixture of nitrogen and hydrogen, and the volume ratio of nitrogen to hydrogen is 4~9:1.
[0010] Furthermore, in step S3, the calcination temperature is 300~550℃.
[0011] Furthermore, in step S3, the heating rate used for calcination is 5℃ / min.
[0012] The beneficial effects of this invention are as follows: This invention revolutionarily proposes the design concept of "functional phase separation": that is, intentionally combining an active component (Mo species) that excels at water adsorption and dissociation with an active component (Ni species) that excels at the adsorption and recombination / desorption of hydrogen intermediates. Cu species were constructed into thermodynamically stable, crystal-structure-independent phases, and the two were made into a tight heterojunction complex at the nanoscale.
[0013] This invention, through a specific process, successfully achieved the stable existence of Mo species in the MoO2 phase and their composite with NiCu alloy. Compared with the comparative electrode obtained by a conventional one-step co-deposition method, which has been verified to be a homogeneous NiCuMo solid solution, the electrode of this invention (NiCu / MoO2 heterogeneous composite electrode) achieves a higher efficiency of 2 A·cm⁻¹. -2 The overpotential under industrial current density was significantly reduced by more than 150 mV, and the Tafel slope was greatly reduced, indicating that its basic HER intrinsic kinetics were fundamentally optimized. The present invention, due to the introduction of Cu, not only promotes the formation of a phase-separated structure, but also effectively suppresses the electrochemical dissolution of Mo elements in the adjacent MoO2 phase. Therefore, Mo exists in the more chemically stable MoO2 crystalline phase, which is less prone to cathodic dissolution, rather than in the metastable, easily migrating zero-valent Mo atoms in the solid solution. The electrode of this invention exhibits unprecedented resistance to component dissolution. Furthermore, it has a high efficiency of 1 A·cm⁻¹. -2 Excellent stability with a performance degradation rate of less than 10% after 1500 hours of continuous operation under harsh conditions. Attached Figure Description
[0014] Figure 1 The image shows a comparison of SEM images of the NiCu / MoO2 heterogeneous composite hydrogen evolution electrode prepared by the method of the present invention in Example 4. Figure 2 Here is a SEM image of the NiCuMo@NF electrode in Example 4; Figure 3 This is a comparison chart of the electrochemical tests of the NiCuMo@NF electrode and the NiCu / MoO2@NF electrode in Example 4; Figure 4 For existing LSV diagrams; Figure 5 This is a comparison chart of the lifetime stability tests of the NiCuMo@NF electrode and the NiCu / MoO2@NF electrode in Example 4; Figure 6 This is a comparison chart of the Mo dissolution concentration of the NiCuMo@NF electrode and the NiCu / MoO2@NF electrode in Example 4. Detailed Implementation
[0015] The specific embodiments of the present invention are described below to enable those skilled in the art to understand the present invention. However, it should be understood that the present invention is not limited to the scope of the specific embodiments. For those skilled in the art, various changes are obvious as long as they are within the spirit and scope of the present invention as defined and determined by the appended claims. All inventions utilizing the concept of the present invention are protected.
[0016] Example 1 The NiCu / MoO2 heterogeneous composite hydrogen evolution electrode based on an unalloying strategy was prepared using the following method: S1: The nickel foam is pretreated by acid washing, water washing and ultrasonic cleaning with ethanol in sequence; S2: Take a homogeneous mixed solution of Cu(NO3)2·3H2O and NaHCO3, with the concentrations of Cu(NO3)2·3H2O and NaHCO3 both being 0.0001 mol / L; immerse the pretreated nickel foam in the solution and react at 100℃ for 4 h; then calcine it in air atmosphere. S3: Immerse it in a mixed solution containing 0.01 mol / L Ni(NO3)2·6H2O, Na2MoO4·2H2O and NH4F for a second hydrothermal reaction; after the reaction is completed, remove and dry it, and finally reduce and calcine it at 300℃ for 4 hours in an atmosphere of N2∶H2=4∶1 at a rate of 5℃ / min to obtain the NiCu / MoO2 heterogeneous composite hydrogen evolution electrode.
[0017] In specific implementation, in step S2, the concentration of the homogeneous mixed solution of Cu(NO3)2·3H2O and NaHCO3 can also be 0.001mol / L, 0.01mol / L, 0.1mol / L, 1mol / L, 2mol / L, 3mol / L, 4mol / L or 5mol / L; In step S2, the hydrothermal temperature can also be 150℃ or 200℃, and the hydrothermal time can also be 6, 8 or 10 hours. In step S3, the concentration of the mixed solution of Ni(NO3)2·6H2O, Na2MoO4·2H2O, and NH4F can also be 0.02, 0.05, 0.1, 0.5, or 1 mol / L. The volume ratio of nitrogen to hydrogen in the reducing atmosphere can also be 5:1, 6:1, 7:1, 8:1, or 9:1; the calcination temperature in step S3 can also be 350℃, 400℃, 450℃, 500℃, or 550℃. Example 2 The difference between this embodiment and Example 1 is that the concentration of Cu(NO3)2·3H2O or NaHCO3 in the homogeneous mixed solution of Cu(NO3)2·3H2O and NaHCO3 is 0.001 mol / L.
[0018] Example 3 The difference between this embodiment and Example 1 is that the concentration of Cu(NO3)2·3H2O or NaHCO3 in the homogeneous mixed solution of Cu(NO3)2·3H2O and NaHCO3 is 5 mol / L.
[0019] Example 4 Electron microscopy was performed on the NiCu / MoO2 heterogeneous composite hydrogen evolution electrodes prepared in Examples 1, 2, and 3, respectively. The results are as follows: Figure 1 As shown, where, Figure 1 In the image, 'a' is a scanning electron microscope image of the electrode prepared in Example 1. Figure 1 In the image, b is a scanning electron microscope (SEM) image of the electrode prepared in Example 2. Figure 1 In the image, 'c' is a scanning electron microscope (SEM) image of the electrode prepared in Example 3; from Figure 1 It is known that the NiCu / MoO2@NF electrode surface prepared by the method of the present invention forms a heterojunction composite with independent NiCu and MoO2 crystal structures.
[0020] To further verify the differences in the electrodes prepared according to this invention, a comparative electrode NiCuMo@NF was prepared using an existing co-deposition method. The co-deposition method specifically involves mixing Cu(NO3)2·3H2O, NaHCO3, Ni(NO3)2·6H2O, Na2MoO4·2H2O, and NH4F together, then immersing the pretreated nickel foam in the mixture for a hydrothermal reaction. The results are as follows: Figure 2 As shown, by Figure 1 a and Figure 2 It is known that the NiCuMo@NF electrode obtained by the traditional one-step hydrothermal co-deposition method has an active component characterized as a uniform NiCuMo ternary solid solution alloy, without an independent MoO2 phase. However, the NiCu / MoO2 heterogeneous composite hydrogen evolution electrode prepared by the method of this invention forms a heterojunction composite with independent NiCu and MoO2 crystal structures on its surface.
[0021] Electrochemical tests were performed on the NiCu / MoO2@NF electrode prepared in Example 1 and the NiCuMo@NF electrode prepared by the existing co-deposition method. The specific test method was as follows: [The text abruptly ends here, so the translation stops as well.] 2 The nickel sheet is the counter electrode, 1cm 2 The sample was used as the working electrode, and mercury oxide was used as the reference electrode, forming a typical three-electrode system. Before testing, it was activated for 5 cycles at 0.05 V / s CV, followed by 5 cycles at 0.01 V / s CV. The test potential range was -0.9 to -2 vs. Hg / HgO (1.0 M KOH), and the test potential range was -0.9 to -1.9 v. The rate was 0.001 V / s. The results were as follows: Figure 3 The LSV diagram shown in 'a' is as follows; EIS was tested at -1V within the range of 100,000Hz to 0.01Hz, and the results were as follows: Figure 3 The EIS diagram shown in b is shown in the figure. A potential range of -0.85V to -0.95V was scanned at speeds of 30mV / s, 40mV / s, 50mV / s, 60mV / s, and 70mV / s for CV5 revolutions. The last revolution was then normalized to obtain the following result: Figure 3 The double-layer capacitance diagram shown in Figure c is as follows.
[0022] The measured LSV value was taken between -1V and -1.7V to prepare the following... Figure 3 The tafel slope plot shown in d is shown in the figure.
[0023] Depend on Figure 3It can be seen that, compared with the NiCuMo@NF electrode obtained by the conventional one-step co-deposition method, whose structure has been verified as a homogeneous NiCuMo solid solution, the NiCu / MoO2@NF electrode of the present invention exhibits better performance at 2A·cm⁻¹. -2 The overpotential at industrial current density is significantly reduced, with a reduction of more than 150 mV, and the Tafel slope is greatly reduced, indicating that its intrinsic kinetics of alkaline HER have been fundamentally optimized.
[0024] The existing technology, CN114150343B, "A Nanofiber NiMoCu Catalyst and Its Preparation Method," uses electroplating to prepare NiMoCu ternary alloys, and its LSV results are as follows: Figure 4 As shown, by Figure 3 a and Figure 4 The comparison shows that the NiCu / MoO2@NF electrode constructed in this invention performs better at 120 mA·cm⁻¹. -2 The overpotential at the current density is only 33mV, while the overpotential of electrodes prepared by existing technologies is as high as 160mV at the same current density.
[0025] For NiCuMo@NF electrodes and NiCu / MoO2@NF electrodes at 1 A·cm -2 Under current density, lifetime stability was tested using constant current charging with blue electric current, and the results are as follows: Figure 5 As shown in the figure, the NiCu / MoO2@NF electrode prepared in this invention exhibits high performance at 1 A·cm⁻¹. -2 It exhibits excellent stability with a performance degradation rate of <10% after 1500 hours of continuous operation under harsh conditions; while the NiCuMo@NF electrode shows significant performance changes after about 600 hours of continuous operation.
[0026] For the NiCuMo@NF electrode and NiCu / MoO2@NF electrode after 7 days of testing, the Mo content in the solution was determined using ICP-MS, and the results are as follows. Figure 5 As shown, by Figure 6 It can be seen that, after lifetime testing, the Mo dissolution concentration in the electrolyte of the NiCu / MoO2@NF electrode prepared in this invention is reduced by more than 85% compared with that of the NiCuMo@NF electrode.
Claims
1. A NiCu / MoO2 heterogeneous composite hydrogen evolution electrode based on a non-alloying strategy, characterized in that, The electrode is used for alkaline hydrogen evolution reaction. The electrode is a heterojunction composite in which MoO2 crystal phase and NiCu alloy crystal phase coexist. The MoO2 crystal phase and NiCu alloy crystal phase are respectively constructed as thermodynamically stable phases with independent crystal structures. The electrode can efficiently catalyze alkaline HER reaction.
2. A method for preparing a NiCu / MoO2 heterogeneous composite hydrogen evolution electrode based on a non-alloying strategy as described in claim 1, characterized in that, The specific steps are as follows: S1: Pretreatment of the nickel foam substrate is carried out by sequential acid washing, water washing and ultrasonic cleaning with ethanol. S2: The pretreated nickel foam substrate is immersed in a mixed solution of copper nitrate and sodium bicarbonate for hydrothermal reaction at a temperature of 100℃~200℃ for 4~10h; then calcined at 300℃ in air for 3h to obtain nickel foam with a CuO nanoneedle array intermediate layer grown on the surface. S3: The nickel foam containing the CuO interlayer obtained in S2 is immersed in a mixed solution of nickel nitrate, sodium molybdate and ammonium fluoride for hydrothermal reaction at a temperature of 100℃~200℃ for 4~10h. After the reaction is completed, it is dried and then calcined in a reducing atmosphere for 4h to obtain the NiCu / MoO2 heterogeneous composite hydrogen evolution electrode.
3. The preparation method according to claim 2, characterized in that, In step S2, the molar ratio of copper nitrate to sodium bicarbonate is 1:1, and the concentration of copper nitrate or sodium bicarbonate in the mixed solution is 0.0001~0.5 mol / L.
4. The preparation method according to claim 3, characterized in that, In step S3, the molar ratio of nickel nitrate, sodium molybdate, and ammonium fluoride is 1:1:1, and the concentration of nickel nitrate / sodium molybdate / ammonium fluoride in the mixed solution is 0.01~1 mol / L.
5. The preparation method according to claim 4, characterized in that, In step S3, the reducing atmosphere is a mixture of nitrogen and hydrogen, and the volume ratio of nitrogen to hydrogen is 4~9:
1.
6. The preparation method according to claim 5, characterized in that, In step S3, the calcination temperature is 300~550℃.
7. The preparation method according to claim 6, characterized in that, In step S3, the heating rate used for calcination is 5℃ / min.