Nickel-molybdenum anode electrode based on crack induced self-passivation mechanism and preparation method thereof

Abstract

The invention relates to a nickel-molybdenum anode electrode based on a crack induced self-passivation mechanism and a preparation method of the nickel-molybdenum anode electrode. The method comprises the following steps that 1, a substrate is soaked in a solution A for 1-25 min and then taken out; 2, immersing the substrate treated in the step 1 into a solution B for 10 minutes to obtain a precursor; and 3, putting the precursor into a Joule ultrafast heating device, heating the precursor to 380-450 DEG C at a heating rate greater than or equal to 100 DEG C / min in an air or inert atmosphere, carrying out heat preservation for a certain time, and cooling to obtain the nickel-molybdenum anode electrode. According to the method, the foam nickel three-dimensional framework is free of structural damage through short-time chemical soaking, the original high porosity and interconnection network of the foam nickel three-dimensional framework are perfectly reserved, and the loss rate of the specific surface area is reduced. According to the prepared nickel-molybdenum anode electrode, by means of the self-passivation effect of the crack edge and the component storage function of the thick layer, the Mo dissolution rate is reduced by one order of magnitude, and thousand-hour-level stable operation under the low current density can be achieved.

Description

Technical Field

[0001] This invention belongs to the field of water electrolysis catalyst technology, specifically relating to a nickel-molybdenum anode electrode based on a crack-induced self-passivation mechanism and its preparation method. Background Technology

[0002] The current research and development of Ni-Mo based oxygen evolution reaction (OER) electrodes generally follows the technical paradigm of "thinning and densification". To avoid the severe bubble erosion and mechanical stress at industrial-grade current densities, academia and industry have long been committed to preparing uniform catalytic layers with a thickness of less than 200 nm and free of macroscopic cracks through methods such as magnetron sputtering and atomic layer deposition. When tested in a standard three-electrode system, these electrodes typically exhibit an overpotential of 260–300 mV at a reference current density of 10 mA / cm², indicating acceptable initial intrinsic activity. However, this optimized approach has a long-neglected but crucial stability blind spot: when these thin, crack-free electrodes are applied to long-term low-current operation scenarios—such as continuous hydrogen production in laboratories, microfluidic electrolyzers, portable hydrogen generators, or the start-up and shutdown of anion exchange membrane electrolyzers—the performance degradation mechanism is not due to mechanical exfoliation, but rather to the active components. Electrochemical dissolution and loss.

[0003] Specifically, in an alkaline electrolyte with pH=14, Even at low polarization potentials (1.48–1.55 V vs. RHE), a non-negligible dissolution equilibrium exists, where molybdenum oxide transforms into molybdate ions. The absolute reserves of Mo for conventional thin-layer electrodes are limited. Although researchers have attempted to suppress dissolution through surface carbon coating or polymer encapsulation, such protective coatings simultaneously block electrolyte contact, sacrificing catalytic activity and creating a trade-off between activity and stability. More importantly, existing technologies... The problem of loss lacks an active suppression strategy. Thin-layer structures have no component redundancy, and once the surface Mo dissolves, the interior cannot replenish it; although the dense, crack-free morphology can slow down the dissolution rate, it also locks the reaction interface, causing the dissolution process to continue within a very small geometric space, lacking dynamic repair capabilities.

[0004] Therefore, there is an urgent need for a nickel-molybdenum anode electrode based on a crack-induced self-passivation mechanism and its preparation method, in order to solve the fundamental problem of irreversible loss of active components and short lifespan of existing thin-layer crack-free electrodes during long-term low-current operation. By utilizing the self-passivation effect of crack edges and the component storage function of thick layers, the dissolution rate of Mo can be reduced by an order of magnitude, achieving key progress in significantly extending the service life in low-current applications. Summary of the Invention

[0005] The application discloses a nickel-molybdenum anode electrode based on a crack-induced self-passivation mechanism and a preparation method thereof.

[0006] The application relates to a preparation method of a nickel-molybdenum anode electrode based on a crack-induced self-passivation mechanism.

[0007] Step one, the substrate is immersed in an A solution for 1 min to 25 min and taken out;

[0008] Step two, the substrate treated in step one is immersed in a B solution for 10 min to obtain a precursor;

[0009] Step three, the precursor is placed in a joule ultrafast heating device, heated to 380 DEG C to 450 DEG C at a heating rate of greater than or equal to 100 DEG C / min in air or an inert atmosphere, and kept for a certain time, and then cooled to obtain the nickel-molybdenum anode electrode.

[0010] Further, in step one, the substrate is a nickel foam, a nickel mesh, a foam iron, a foam cobalt, a foam copper, a foam NiFe, an iron foil, a cobalt foil, a NiFe foil or a NiTi foil.

[0011] Further, in step one, the A solution is one or more of ammonium persulfate solution, potassium persulfate solution, sodium persulfate solution, sodium hypochlorite solution and hydrogen peroxide.

[0012] Further, in step one, the concentration of the A solution is 0.1 mol / L to 0.3 mol / L.

[0013] Further, in step two, the B solution is a sodium molybdate solution, an ammonium molybdate solution or a potassium molybdate solution.

[0014] Further, in step two, the concentration of the B solution is 0.005 mol / L to 0.03 mol / L.

[0015] Further, in step three, the certain time for keeping is 5 s to 50 s.

[0016] The application also relates to a nickel-molybdenum anode electrode based on a crack-induced self-passivation mechanism, which is prepared by the preparation method.

[0017] Further, the nickel-molybdenum anode electrode has a passivation-activity composite structure. The redox pair exists on the surface of the nickel-molybdenum anode electrode.

[0018] Advantages

[0019] The application provides a nickel-molybdenum anode electrode based on a crack-induced self-passivation mechanism and a preparation method thereof. BRIEF DESCRIPTION OF DRAWINGS

[0020] Figure 1 An OER overpotential column chart of the nickel-molybdenum anode electrode prepared in the embodiment one of the application;

[0021] Figure 2 A micro-morphology chart of the nickel-molybdenum anode electrode prepared in the embodiment one of the application;

[0022] Figure 3 A stability test chart of the nickel-molybdenum anode electrode prepared in the embodiment one of the application;

[0023] Figure 4 An XPS chart of the nickel-molybdenum anode electrode prepared in the embodiment one of the application. DETAILED DESCRIPTION

[0024] The following specifically describes the embodiment. Figures 1 to 4 The embodiment is specifically described.

[0025] The core technical problem to be solved by the application is that the existing thin-layer crack-free electrode has the problems of irreversible loss of active components and short service life in long-term low-current operation, and the application provides a novel electrode structure for realizing dynamic locking and gradient activation of active components through a thick layer-crack morphology. The structure utilizes the self-passivation effect of the crack edge and the component storage function of the thick layer to reduce the Mo dissolution rate by an order of magnitude, so that the electrode can be stably operated at 10 mA / cm² for more than 1000 hours without obvious performance degradation, and the service life is significantly prolonged in the low-current application field.

[0026] The application relates to a nickel-molybdenum anode electrode based on a crack-induced self-passivation mechanism and a preparation method thereof.

[0027] Step one, the substrate is immersed in a 0.1mol / L-0.3mol / L A solution for 1min-25min and then taken out.

[0028] The substrate is foamed nickel, a nickel mesh, foamed iron, foamed cobalt, foamed copper, foamed NiFe, an iron foil, a cobalt foil, a NiFe foil or a NiTi foil.

[0029] The A solution is one or more of ammonium persulfate solution, potassium persulfate solution, sodium persulfate solution, sodium hypochlorite solution, and hydrogen peroxide solution, and all of the solutions have oxidizing properties.

[0030] The surface of the substrate is oxidized and pretreated by soaking the substrate in the A solution to form an active oxidation layer. For example, when foam nickel is selected as the substrate, the surface of the foam nickel can be oxidized to form a hydroxyl nickel oxide or a nickel hydroxide layer by soaking in the A solution. The oxidation layer has a porous structure and high surface energy, which can significantly enhance the adsorption capacity of the subsequent ammonium molybdate. The concentration of the A solution determines the thickness and compactness of the oxidation layer. If the concentration is too low, the oxidation is insufficient and the active sites are few; if the concentration is too high, the foam nickel skeleton can be corroded and the three-dimensional structure can be damaged. The concentration is a key parameter that ensures moderate oxidation without damaging the substrate. The time is selected to be 1 min to 25 min to balance the efficiency and effect.

[0031] Step two, the substrate treated in step one is soaked in a B solution with a concentration of 0.005 mol / L to 0.03 mol / L for 10 min, and then taken out to obtain a precursor.

[0032] The B solution is a sodium molybdate solution, an ammonium molybdate solution, or a potassium molybdate solution.

[0033] The purpose of soaking the substrate in the B solution is to provide a molybdenum source, and the molybdenum precursor is loaded on the surface of the pre-oxidized foam nickel by ion adsorption. The addition of molybdenum is a key step to improve the OER activity. Molybdate ions will form a nickel-molybdenum composite precursor with the surface nickel oxide, which lays the foundation for the subsequent pyrolysis to generate active nickel molybdenum compounds.

[0034] Step three, the precursor is placed in a joule ultrafast heating device, heated to 380°C to 450°C at a heating rate of greater than or equal to 100°C / min in air or an inert atmosphere, and held for 5 s to 50 s, and then cooled to obtain a nickel molybdenum anode electrode.

[0035] The extremely high heating rate makes the precursor undergo a rapid thermal decomposition, redox, and phase change process in an instant. Due to the difference in thermal expansion coefficient between the nickel substrate and the molybdenum oxide, a huge internal stress is generated. This stress cannot be completely released through material diffusion in a very short heat treatment time, so a large number of micron / nanometer scale crack networks are formed in a controlled manner on the surface or interface. In the process of rapid heating, the valence of Mo also changes, inducing the formation of and The high valence of realizes self-passivation of the electrode surface to enhance stability, and The high activity promotes fast transfer of charges.

[0036] The application also relates to a nickel-molybdenum anode electrode based on a crack-induced self-passivation mechanism, which is prepared by a preparation method of the nickel-molybdenum anode electrode based on the crack-induced self-passivation mechanism. The redox pair has a passivation-activity composite structure.

[0037] Example one

[0038] A nickel-molybdenum anode electrode based on a crack-induced self-passivation mechanism and a preparation method thereof, comprising the following steps:

[0039] Step one: foam nickel with a size of 2cm*3cm is immersed in 0.2mol / L ammonium persulfate solution for 10min and then taken out.

[0040] Step two: the foam nickel is further treated by being immersed in 0.015mol / L ammonium molybdate solution for 10min to obtain a precursor.

[0041] Step three: the precursor is placed in a joule ultrafast heating device, heated to 400 DEG C at a heating rate of 200 DEG C / min in air or inert atmosphere and kept for 10s, and then cooled to obtain the nickel-molybdenum anode electrode.

[0042] Example two

[0043] The difference between the embodiment and example one is that the concentration of the ammonium molybdate solution in step two is 0.005mol / L, and the others are the same as those in example one.

[0044] Example three

[0045] The difference between the embodiment and example one is that the concentration of the ammonium molybdate solution in step two is 0.01mol / L, and the others are the same as those in example one.

[0046] Example four

[0047] The difference between the embodiment and example one is that the concentration of the ammonium molybdate solution in step two is 0.02mol / L, and the others are the same as those in example one.

[0048] Example five

[0049] The difference between the embodiment and example two is that the heating rate in step three is 100 DEG C / min, and the others are the same as those in example two.

[0050] Example six

[0051] The difference between the embodiment and example two is that the heating rate in step three is 150 DEG C / min, and the others are the same as those in example two.

[0052] Example 7

[0053] The difference between this embodiment and Embodiment 2 is that the heating rate in step 3 is 250℃ / min. Everything else is the same as in Embodiment 2.

[0054] Compared to Example 1, Examples 2 to 4 controlled the Mo source supply and precursor layer quality by changing the concentration of ammonium molybdate solution. Examples 5 to 7, compared to Example 1, adjusted the phase transition and evolution kinetics by changing the heating rate.

[0055] Figure 1 This is a bar chart of the OER overpotential of the nickel-molybdenum anode electrode prepared in Example 1 of this invention. The OER overpotential bar chart was obtained using a 1 mol / L KOH solution as the electrolyte in the electrochemical workstation test. During the OER reaction, the original nickel foam of the nickel-molybdenum anode electrode prepared in Example 1 reached 10 mA / cm². 2 The overpotential at the given current density is 363 mV. Meanwhile, the nickel-molybdenum catalyst exhibits an overpotential of 363 mV at 10 mA / cm². 2 The current density can reach an overpotential of 234mV, which is 129mV lower than the original overpotential of nickel foam, indicating that the OER activity of the nickel-molybdenum electrode prepared by this patented method is effectively improved.

[0056] Figure 2 This is a microscopic morphology image of the nickel-molybdenum anode electrode prepared according to Embodiment 1 of the present invention; the scale bar is 1 μm. As shown in the image, a relatively thick activation layer with cracks has formed on the surface of the nickel-molybdenum anode electrode prepared in Embodiment 1. The activation layer provides mechanical redundancy; even if local peeling occurs, the fresh active sites at the bottom of the cracks can continue to function. The crack network serves as a pre-designed bubble escape channel, enabling… After the bubbles coalesce within the cracks, they quickly detach, avoiding covering the active surface. Furthermore, the crack network promotes forced convection of the electrolyte, suppressing local pH fluctuations and impurity deposition.

[0057] Figure 3 This is a stability test diagram of the nickel-molybdenum anode electrode prepared in Embodiment 1 of the present invention; as shown in the diagram, without IR correction, 10 mA / cm 2 The total water splitting voltage remained stable at 1.42–1.45 V for 1000 hours without significant decay. This data directly demonstrates that the crack-thick layer morphology did not impair the intrinsic activity of the electrode; on the contrary, it achieved a perfect balance between activity and durability through a self-passivation mechanism and component reserve effect.

[0058] Figure 4 The image shows the XPS plot of the nickel-molybdenum anode electrode prepared in Embodiment 1 of the present invention; as can be seen from the figure, 232.5 eV and 235.6 eV belong to 229.8 eV and 232.9 eV correspond to The peak area indicates that molybdenum on the electrode surface is predominantly in a high valence state, and that there is... Redox pairs enable the electrode to function as both a redox pair and a redox pair. High valence state passivation stability and Mo 4+ The charge transfer activity forms a "passivation-activity" composite structure.

[0059] This invention achieves a maximum processing temperature of no more than 450℃, avoiding the risks of combustion and explosion and leakage associated with the use of high-pressure hydrogen compared to the traditional 800℃~1000℃ high-temperature hydrogen reduction process, thus realizing inherently safe production. Furthermore, the synergy between the low-temperature process and rapid heating reduces the single-batch processing cycle from 4~6 hours in the traditional process to within 1 hour. After electrochemical activation, a Mo-rich passivation layer forms at the crack edge, making... The dissolution rate is reduced by an order of magnitude, achieving an ultra-long lifespan of over 1000 hours. At the same time, the thick layer provides a larger Mo reserve than the thin layer electrode. Even if a trace amount of dissolution occurs, fresh active sites at the bottom of the crack can be exposed in a gradient, maintaining the dynamic balance of the overall Mo / Ni atomic ratio and avoiding a "cliff-like" performance degradation.

[0060] The above description of the present invention is only a preferred embodiment of the present invention and is not intended to limit the implementation of the present invention. Those skilled in the art can easily make corresponding modifications or alterations based on the main concept and spirit of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of protection claimed in the claims.

Claims

1. A method for preparing a nickel-molybdenum anode electrode based on the crack-induced self-passivation mechanism, characterized by, Includes the following steps: Step 1: Immerse the substrate in solution A for 1 to 25 minutes, then remove it. Step 2: Immerse the substrate treated in Step 1 in solution B for 10 minutes to obtain the precursor; Step 3: Place the precursor in a Joule ultrafast heating device and heat it to 380℃~450℃ in air or an inert atmosphere at a heating rate of ≥100℃ / min. Hold it at this temperature for a certain time and then cool it to obtain the nickel-molybdenum anode electrode.

2. The method for preparing a nickel-molybdenum anode electrode based on a crack-induced self-passivation mechanism according to claim 1, characterized in that, In step one, the substrate is nickel foam, nickel mesh, iron foam, cobalt foam, copper foam, NiFe foam, iron foil, cobalt foil, NiFe foil, or NiTi foil.

3. The method for preparing a nickel-molybdenum anode electrode based on a crack-induced self-passivation mechanism according to claim 1, characterized in that, In step one, solution A is one or more of ammonium persulfate solution, potassium persulfate solution, sodium persulfate solution, sodium hypochlorite solution, and hydrogen peroxide.

4. The method for preparing a nickel-molybdenum anode electrode based on a crack-induced self-passivation mechanism according to claim 1, characterized in that, In step one, the concentration of solution A is 0.1 mol / L to 0.3 mol / L.

5. The method for preparing a nickel-molybdenum anode electrode based on a crack-induced self-passivation mechanism according to claim 1, characterized in that, In step two, solution B is a sodium molybdate solution, an ammonium molybdate solution, or a potassium molybdate solution.

6. The method for preparing a nickel-molybdenum anode electrode based on a crack-induced self-passivation mechanism according to claim 1, characterized in that, In step two, the concentration of solution B is 0.005 mol / L to 0.03 mol / L.

7. The method for preparing a nickel-molybdenum anode electrode based on a crack-induced self-passivation mechanism according to claim 1, characterized in that, In step three, the heat preservation time is 5 to 50 seconds.

8. A nickel-molybdenum anode electrode based on a crack-induced self-passivation mechanism, characterized in that, It is prepared using the method for preparing a nickel-molybdenum anode electrode based on a crack-induced self-passivation mechanism as described in any one of claims 1-9.

9. The nickel-molybdenum anode electrode based on crack-induced self-passivation mechanism according to claim 8, characterized in that, The surface of the nickel-molybdenum anode electrode has Redox pairs possess a passivation-activation composite structure.

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