Palladium-coated ZrCo hydrogen storage alloy with resistance to oxygen poisoning and long-term cycle stability, its preparation and application

Abstract

This invention discloses a palladium-coated ZrCo hydrogen storage alloy with resistance to oxygen poisoning and long-term cycling stability, its preparation method, and its application in hydrogen isotope storage. The palladium-coated ZrCo hydrogen storage alloy has a composite structure consisting of an outer palladium coating layer, a Pd3Zr transition layer, and a ZrCo alloy matrix, wherein the Pd3Zr is coherent with the Pd and ZrCo alloy matrix. Preparation method: Palladium-coated ZrCo alloy particles are subjected to high-temperature dynamic vacuum at 500–550℃ for 5–55 minutes, followed by cooling to obtain the palladium-coated ZrCo hydrogen storage alloy. This invention solves the common problem of palladium film detachment in palladium-coated ZrCo alloys.

Description

Technical Field

[0001] This invention relates to the field of hydrogen storage materials, specifically to a palladium-coated ZrCo hydrogen storage alloy with resistance to oxygen poisoning and long-term cycle stability, its preparation method, and its application. Background Technology

[0002] Energy is a crucial material foundation for economic development and social operation. However, due to the over-exploitation and use of fossil fuels, problems such as energy shortages and environmental pollution are becoming increasingly prominent, making energy transition imperative. Developing renewable and clean energy is the only way to achieve this transition. Among various clean energy sources, nuclear fusion energy, based on deuterium-tritium plasma reactions, has attracted widespread attention from countries around the world due to its high energy output and lack of high-level radioactive waste.

[0003] As fuel gases for nuclear fusion reactions, hydrogen isotopes deuterium and tritium are extremely scarce and radioactive. Therefore, to achieve the supply or recovery of hydrogen isotope gases, safe and efficient hydrogen isotope storage methods must be developed. Among various hydrogen storage materials, ZrCo-based hydrogen storage alloys are considered the most promising hydrogen isotope storage materials due to their extremely low room-temperature hydrogen absorption equilibrium pressure, rapid room-temperature hydrogen absorption kinetics, and good helium fixation ability. However, in practical applications, ZrCo alloys are highly susceptible to poisoning by impurity gases (especially oxygen) in hydrogen, leading to a decline in hydrogen absorption capacity and kinetics. Therefore, improving the oxygen poisoning resistance of ZrCo hydrogen storage alloys has become a crucial focus.

[0004] Considering palladium's catalytic dissociation properties and selective permeability to hydrogen, and the widespread industrial application of electroless palladium plating, depositing a palladium coating on the surface of hydrogen storage alloys via electroless plating is widely used to improve the alloys' resistance to poisoning by impurity gases. However, due to palladium's hydrogen embrittlement and the poor adhesion between the coating and the substrate, the palladium coating is prone to breakage and detachment during cyclic hydrogen absorption and desorption, leading to a decline in the palladium-plated alloy's resistance to poisoning. Therefore, to achieve long-term protection of the alloy substrate by the palladium film and improve the service life of the palladium-plated alloy, it is essential to solve the problem of palladium film detachment during cyclic hydrogen absorption and desorption.

[0005] Alloying can effectively improve the hydrogen embrittlement resistance and mechanical properties of palladium films, ensuring their stability during hydrogen absorption and desorption cycles. Currently, palladium alloy films can be formed on the surface of hydrogen storage alloy particles using co-deposition and sequential deposition electroless plating methods, but both methods have limitations. Co-deposition involves mixing palladium plating solutions with those of other alloying elements, allowing palladium and other alloying elements to deposit simultaneously on the carrier surface, forming a palladium alloy coating. However, due to the different oxidizing properties of metal ions in the plating solution, the deposition order of different metals varies, making it difficult to control the distribution and proportion of elements in the alloy film, thus compromising the uniformity and density of the prepared palladium alloy film. Sequential deposition involves performing two separate electroless plating processes on the alloy surface to prepare a thin film composed of two sequentially arranged metal layers, followed by annealing to form the alloy film layer. While sequential deposition can achieve some degree of control over the film composition, the complex and cumbersome process undoubtedly increases production costs and preparation difficulty. Furthermore, while alloying can modify the film layer and improve its stability during hydrogen absorption and desorption cycles, it cannot effectively solve the problem of weak adhesion between the film layer and the substrate in electroless plating. Therefore, to achieve long-term protection of the alloy substrate by the palladium film and improve the service life of the palladium-plated alloy, it is necessary to improve the stability of the film layer while ensuring a strong bond between the film layer and the substrate.

[0006] In conclusion, the development of palladium-coated ZrCo hydrogen storage alloys with resistance to oxygen poisoning and long-term cycle stability is of great significance for hydrogen isotope storage in fusion reactors. Summary of the Invention

[0007] This invention provides a palladium-coated ZrCo hydrogen storage alloy with resistance to oxygen poisoning and long-term cycle stability, which can solve the problem of palladium film peeling that is common in palladium-coated ZrCo alloys.

[0008] A palladium-coated ZrCo hydrogen storage alloy with resistance to oxygen poisoning and long-term cycle stability has a composite structure consisting of an outer palladium coating layer, a Pd3Zr transition layer, and a ZrCo alloy matrix (which can be represented as a Pd / Pd3Zr@ZrCo alloy matrix composite structure), wherein the Pd3Zr forms a coherent relationship with the outer Pd layer and the inner ZrCo alloy matrix.

[0009] In one embodiment, the palladium content in the palladium-coated ZrCo hydrogen storage alloy is 5% to 15% by mass.

[0010] The present invention also provides a method for preparing the palladium-coated ZrCo hydrogen storage alloy, wherein palladium-coated ZrCo alloy particles are subjected to high-temperature dynamic vacuuming at 500-550°C for 5-55 minutes, and then cooled to obtain the palladium-coated ZrCo hydrogen storage alloy.

[0011] This invention involves subjecting palladium-plated ZrCo alloy particles to a high-temperature dynamic vacuum at 500–550°C for 5–55 minutes. This process causes a partial reaction between the Pd in ​​the outer palladium coating and the inner ZrCo alloy matrix, transforming it into Pd3Zr, thus forming a composite structure consisting of an outer Pd layer, an intermediate Pd3Zr layer, and an inner ZrCo alloy matrix. The above preparation method requires appropriate control of the processing temperature and time. If the processing time is too short or the temperature is too low, the phase transformation to Pd3Zr cannot be initiated. For example, the inventors found in experiments that at a processing temperature of 450°C, even with a processing time extended to 1 hour, the outer Pd layer remained stable, with no Pd3Zr formation. Conversely, if the processing time is too long or the temperature is too high, the Pd in ​​the outer palladium coating will completely transform into Pd3Zr, forming a bilayer structure consisting only of a Pd3Zr coating and an inner ZrCo alloy matrix. Such a bilayer structure exhibits relatively poor resistance to oxygen poisoning.

[0012] In one embodiment, the method for preparing the palladium-plated ZrCo alloy particles includes the following steps:

[0013] (1) Place Zr and Co elemental raw materials in stoichiometric ratio into a magnetic levitation induction melting furnace, and melt-cool solidify under argon atmosphere protection to obtain ZrCo alloy ingots.

[0014] (2) ZrCo alloy ingots are crushed into particles by hydrogenation pulverization to obtain hydrogen-absorbing ZrCo alloy particles.

[0015] (3) Place the hydrogen-absorbing ZrCo alloy particles in a reactor and dynamically vacuum them at 540-560°C for 50-70 minutes to obtain fine ZrCo alloy particles.

[0016] (4) Place the fine ZrCo alloy particles in a fluorination solution and stir at 65-75°C for 0.5-1.5 hours to fluorinate them. Then wash the particles with deionized water at 65-75°C to remove impurities from the particle surface and obtain fluorinated ZrCo alloy particles.

[0017] (5) Place the fluorinated ZrCo alloy particles in a sensitization solution and stir for 1 to 2 minutes at room temperature to sensitize them. Wash the impurities on the particle surface with deionized water to obtain sensitized ZrCo alloy particles.

[0018] (6) Place the sensitized ZrCo alloy particles in an activation solution and stir for 1 to 2 minutes at room temperature to activate them. Wash the surface impurities of the particles with deionized water to obtain activated ZrCo alloy particles.

[0019] (7) Place the activated ZrCo alloy particles in the plating solution and stir at 45-55°C for 15-25 minutes to perform electroless palladium plating. Wash the impurities on the particle surface with deionized water and remove water by vacuum at 75-85°C to obtain the palladium-plated ZrCo alloy particles.

[0020] In one embodiment, in step (4), the solute in the fluorination solution is 0.5-1.5 mL / L hydrofluoric acid and 0.5-1.5 g / L potassium fluoride, and the mass concentration of HF in the hydrofluoric acid is 48%-50%.

[0021] In one embodiment, in step (4), the mass ratio of the ZrCo alloy fine particles to the volume of the fluorinated solution is 2-4 g: 200 mL.

[0022] In one embodiment, in step (5), the solute in the sensitization solution is 4-6 g / L stannous chloride and 15-25 mL / L hydrochloric acid, and the mass concentration of HCl in the hydrochloric acid is 36%-38%.

[0023] In one embodiment, in step (5), the mass ratio of the fluorinated ZrCo alloy particles to the volume of the sensitized solution is 2-4 g: 200 mL.

[0024] In one embodiment, in step (6), the solute in the activation solution is 0.2-0.3 g / L palladium chloride and 2-3 mL / L hydrochloric acid, and the mass concentration of HCl in the hydrochloric acid is 36%-38%.

[0025] In one embodiment, in step (6), the mass ratio of the sensitized ZrCo alloy particles to the volume of the activation solution is 2-4 g: 200 mL.

[0026] One execution of steps (5) and (6) is recorded as one sensitization-activation process. In one embodiment, steps (5) and (6) are repeated for a total of 2 to 4 sensitization-activation processes.

[0027] In one embodiment, in step (7), the solutes in the plating solution are 4-5 g / L palladium chloride, 45-55 g / L disodium ethylenediaminetetraacetate, 45-55 mg / L ammonium chloride, 0.04-0.06 mol / L hydrazine hydrate, and 240-260 mL / L ammonia water, wherein the mass concentration of NH3 in the ammonia water is 25%-28%.

[0028] In one embodiment, in step (7), the ratio of the mass of the activated ZrCo alloy particles to the volume of the plating solution is 2-4 g: 100 mL.

[0029] The preparation method of the palladium-coated ZrCo hydrogen storage alloy described in this invention is simple. By subjecting the palladium-coated ZrCo hydrogen storage alloy to a high-temperature, short-time heating pretreatment, the Pd portion at the film / substrate interface is transformed into Pd3Zr, generating a stable Pd3Zr transition layer. Since a large amount of surface Pd elemental is retained during the pretreatment process, the alloy exhibits excellent resistance to oxygen poisoning. Furthermore, the Pd3Zr transition layer not only maintains structural stability during hydrogen absorption and desorption but also forms a coherent relationship with the Pd layer and the ZrCo matrix, achieving a tight bond between the film and the matrix, thereby inhibiting palladium film shedding and improving the cycling stability of the palladium-coated ZrCo alloy. The palladium-coated ZrCo hydrogen storage alloy with a Pd / Pd3Zr@ZrCo alloy matrix composite structure constructed in this invention possesses both excellent resistance to oxygen poisoning and long-term cycling stability, providing valuable reference for anti-poisoning research in the field of hydrogen isotope storage.

[0030] The present invention also provides the application of the palladium-coated ZrCo hydrogen storage alloy in hydrogen isotope storage.

[0031] Compared with the prior art, the beneficial effects of this invention are as follows:

[0032] 1. This invention addresses the issue of palladium film detachment from the palladium-coated hydrogen storage alloy during cyclic hydrogen absorption and desorption by enhancing the adhesion between the palladium coating and the substrate. A Pd3Zr transition layer is generated at the Pd / ZrCo interface through a high-temperature, short-time pretreatment of the palladium-coated ZrCo alloy. Pd3Zr can simultaneously form a coherent relationship with both Pd and ZrCo, achieving a tight bond between the Pd film and the ZrCo substrate. Therefore, it effectively suppresses palladium film detachment during cyclic hydrogen absorption and desorption, achieving long-term protection of the substrate. The prepared palladium-coated ZrCo hydrogen storage alloy retains over 90% of its capacity after 10 cycles in hydrogen gas containing 1.0 vol% O2.

[0033] 2. This invention constructs a Pd / Pd3Zr@ZrCo alloy matrix composite structure, enabling the prepared Pd / Pd3Zr surface film to possess the characteristics of both Pd and Pd3Zr, thus exhibiting excellent comprehensive performance. The surface palladium film has selective permeability to hydrogen, effectively preventing oxygen poisoning of the alloy matrix; while the hydrogen-inert Pd3Zr transition layer is less prone to hydrogen embrittlement, possesses good thermal stability and mechanical properties, and remains stable during hydrogen absorption and desorption. Therefore, constructing a Pd / Pd3Zr@ZrCo alloy matrix composite structure allows the prepared alloy sample to possess both excellent resistance to oxygen poisoning and long-term cyclic hydrogen storage stability.

[0034] 3. Compared with other electroless plating methods for palladium alloy films (co-deposition method and sequential deposition method), the present invention is simpler and easier to control. The palladium-coated ZrCo alloy obtained has a unique Pd / Pd3Zr@ZrCo coherent structure, which has good reference value for anti-poisoning research in the field of hydrogen isotope storage. Attached Figure Description

[0035] Figure 1 X-ray diffraction (XRD) patterns of the alloys prepared in Comparative Examples 1-2 and Example 1;

[0036] Figure 2 Transmission electron microscope (TEM) image and lattice structure diagram of the palladium-coated ZrCo hydrogen storage alloy prepared in Example 1;

[0037] Figure 3 This is a schematic diagram of the Pd / Pd3Zr@ZrCo alloy matrix composite structure of the palladium-coated ZrCo hydrogen storage alloy prepared in Example 1.

[0038] Figure 4 The hydrogen absorption kinetics at room temperature for the alloys prepared in Comparative Examples 1-2 and Example 1 in a hydrogen atmosphere containing 1.0 vol% O2;

[0039] Figure 5 The figure shows the results of first-principles calculations of the interaction between H2 and O2 on three matrices: ZrCo, Pd3Zr, and Pd.

[0040] Figure 6 Comparative graph showing the cycling stability of the alloys prepared in Comparative Example 1 and Example 1 in a hydrogen atmosphere containing 1.0 vol% O2;

[0041] Figure 7 Scanning electron microscope (SEM) and energy dispersive spectroscopy (EDS) images of the alloy prepared for Comparative Example 1 after 10 cycles in a hydrogen atmosphere containing 1.0 vol% O2.

[0042] Figure 8 SEM and EDS images of the palladium-coated ZrCo hydrogen storage alloy prepared in Example 1 after 10 cycles in a hydrogen atmosphere containing 1.0 vol% O2. Detailed Implementation

[0043] The present invention will be further described below with reference to the accompanying drawings and specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention.

[0044] Comparative Example 1

[0045] The sample consists of two parts: a palladium coating layer and a ZrCo matrix (denoted as Pd@ZrCo). The preparation process includes the following steps:

[0046] 1) Stoichiometric proportions of elemental Zr and Co raw materials were placed in a magnetic levitation induction melting furnace and melted under an argon atmosphere to obtain ZrCo alloy ingots. The ZrCo alloy ingots were then crushed into particles using a hydrogenation pulverization method, and dehydrogenated under dynamic vacuum at 550℃ for 60 minutes to obtain fine ZrCo alloy particles. 3g of these fine ZrCo alloy particles were placed in 200mL of a fluorination solution (solutes being 1mL / L hydrofluoric acid and 1g / L potassium fluoride, with an HF mass concentration of 49% in the hydrofluoric acid), stirred at 70℃ for 1 hour, and then washed with deionized water at 70℃ to remove surface impurities, yielding fluorinated ZrCo alloy particles. 3g of fluorinated ZrCo alloy particles were sequentially placed in 200mL of sensitization solution (solutes: 5g / L stannous chloride and 20mL / L hydrochloric acid, with an HCl mass concentration of 36%–38%) and 200mL of activation solution (solutes: 0.25g / L palladium chloride and 2.5mL / L hydrochloric acid, with an HCl mass concentration of 36%–38%). Sensitization and activation were performed by stirring for one minute at room temperature. After each sensitization or activation, the particle surface was washed with deionized water to remove impurities. This sensitization-activation process was repeated three times to obtain activated ZrCo alloy particles. 3g of activated ZrCo alloy particles were placed in 100mL of plating solution (solutes were 4.2g / L palladium chloride, 50g / L disodium ethylenediaminetetraacetate, 50mg / L ammonium chloride, 0.05mol / L hydrazine hydrate, and 250mL / L ammonia water, with an NH3 mass concentration of 25%–28%), and electroless palladium plating was performed by stirring at 50℃ for 20 minutes. After washing away impurities on the particle surface with deionized water, the particles were dehydrated by vacuuming at 80℃ for 12 hours to obtain palladium-plated ZrCo alloy particles, in which the mass percentage of palladium was 9.8%.

[0047] 2) To activate the particle surface, the palladium-plated ZrCo alloy particles need to be placed in a reactor for heating and vacuum pretreatment at a temperature of 380℃ for 10 minutes. After cooling to room temperature, Pd@ZrCo samples are obtained.

[0048] Comparative Example 2

[0049] The sample consists of two parts: a Pd3Zr coating layer and a ZrCo matrix (denoted as Pd3Zr@ZrCo). The preparation process includes the following steps:

[0050] 1) Same as Comparative Example 1, Step 1).

[0051] 2) To ensure that the palladium coating on the surface of the alloy particles is completely transformed into Pd3Zr, the palladium-plated ZrCo alloy particles need to be placed in a reactor for high-temperature vacuum pretreatment at 550℃ for 60 minutes. After cooling to room temperature, Pd3Zr@ZrCo samples are obtained.

[0052] Example 1

[0053] The sample consists of three parts: an outer palladium coating layer, a middle Pd3Zr transition layer, and an inner ZrCo alloy matrix (denoted as Pd / Pd3Zr@ZrCo). The preparation process includes the following steps:

[0054] 1) Same as step 1) of Comparative Example 1;

[0055] 2) To form a Pd3Zr transition layer between the Pd coating and the ZrCo matrix, the palladium-plated ZrCo alloy particles need to be placed in a reactor for high-temperature vacuum pretreatment at 550°C for 10 minutes. After cooling to room temperature, Pd / Pd3Zr@ZrCo samples are obtained.

[0056] Example 2

[0057] To compare the changes in alloy phase structure in this invention, the XRD patterns of the alloy particles in Comparative Examples 1-2 and Example 1 are shown below. Figure 1 As shown, it can be seen that by adjusting the pretreatment parameters of the palladium-plated ZrCo alloy particles, samples with three different phase structures, namely Pd+ZrCo, Pd3Zr+ZrCo, and Pd+Pd3Zr+ZrCo, were prepared.

[0058] The structure of Pd / Pd3Zr@ZrCo was further characterized by TEM, and the results are as follows: Figure 2 As shown, the lattice fringes and diffraction spots reveal the simultaneous presence of three phases: Pd, Pd3Zr, and ZrCo. Pd is distributed in the outermost layer, with the Pd3Zr phase gradually appearing with increasing depth, and finally the ZrCo matrix. According to the edge-to-edge matching model, when a new phase precipitates from the parent phase, if the mismatch between the close-packed plane spacing and the parent phase is less than 6%, and the mismatch between the atomic spacing in the close-packed directions on the close-packed planes is less than 10%, then the new phase and the parent phase can form a coherent relationship. The mismatch degree between the close-packed plane Pd3Zr(202) and Pd(111) is 3.81%, and the mismatch degree with ZrCo(110) is 4.53%. The mismatch degree between Pd3Zr

[010] and Pd

[110] in the close-packed direction is 1.95%, and the mismatch degree with ZrCo

[111] is 1.66%, indicating that Pd3Zr forms a coherent relationship with both Pd and ZrCo.

[0059] Figure 3 The Pd / Pd3Zr@ZrCo alloy matrix composite structure of the palladium-coated ZrCo hydrogen storage alloy prepared in Example 1 is shown.

[0060] Example 3

[0061] To evaluate the anti-poisoning performance of the samples, the hydrogen absorption kinetics of the samples in an oxygen-containing impurity atmosphere at room temperature were tested using a Sieverts-type instrument via a constant-volume method. The kinetic tests were conducted in a hydrogen atmosphere containing 1.0 vol% O2 at 2 bar. First, the partial pressures of H2 and O2 were calculated based on the total gas pressure and the H2 / O2 ratio. Then, O2 and H2 at the corresponding pressures were sequentially introduced into the instrument, and after thorough mixing, a hydrogen gas atmosphere containing 1.0 vol% O2 at 2 bar was prepared. Finally, the prepared hydrogen-oxygen mixture was introduced into the reactor containing the samples, and its hydrogen absorption kinetics were tested.

[0062] The hydrogen absorption kinetic curves of Comparative Examples 1-2 and Example 1 are as follows: Figure 4 As shown, the horizontal axis represents time (in hours), and the vertical axis represents the current hydrogen absorption capacity / maximum hydrogen absorption capacity (in %). It can be seen that the Pd@ZrCo sample of Comparative Example 1 and the Pd / Pd3Zr@ZrCo sample of Example 1 can rapidly absorb hydrogen under an oxygen-containing impurity atmosphere, while the hydrogen absorption rate of the Pd3Zr@ZrCo sample of Comparative Example 2 is slow. This is based on first-principles calculations (…). Figure 5 O2 can spontaneously decompose on the Pd3Zr surface with an adsorption energy of -5.6827 eV, while on the Pd surface it only exhibits adsorption with an adsorption energy of -0.9999 eV. This indicates that O2 can interact more strongly with Pd3Zr, meaning that Pd has better resistance to oxygen poisoning than Pd3Zr. Therefore, the Pd@ZrCo and Pd / Pd3Zr@ZrCo samples with palladium coatings have better resistance to oxygen poisoning, while the Pd3Zr@ZrCo sample in Comparative Example 2 has relatively poor resistance to oxygen poisoning.

[0063] Example 4

[0064] To evaluate the effectiveness of constructing a Pd3Zr transition layer in improving the cycling stability of palladium-plated ZrCo alloys, the Pd@ZrCo samples of Comparative Example 1 and the Pd / Pd3Zr@ZrCo samples of Example 1 were subjected to 10 hydrogen adsorption / desorption cycles using a Sieverts-type instrument via a constant-volume method. The capacity retention rate for each cycle was recorded, and the results are as follows: Figure 6 As shown. The cycle was conducted in a hydrogen atmosphere containing 1.0 vol% O2 at 2 bar. First, the partial pressures of H2 and O2 were calculated based on the total gas pressure and the H2 / O2 ratio. O2 and H2 at the corresponding pressures were then sequentially introduced into the testing instrument, and after thorough mixing, a hydrogen gas containing 1.0 vol% O2 at 2 bar was prepared. The prepared hydrogen-oxygen mixture was then introduced into the reactor containing the sample, and its hydrogen absorption kinetics were tested. After hydrogen absorption, the sample was dynamically evacuated at 380°C for 10 minutes to completely remove hydrogen. After cooling to room temperature, the prepared hydrogen-oxygen mixture was introduced again for the next hydrogen absorption cycle. Figure 6It can be seen that after 10 cycles, the capacity retention rate of the Pd@ZrCo sample was 84.93%, and the capacity retention rate of the Pd / Pd3Zr@ZrCo sample was 90.83%, indicating that constructing a Pd3Zr transition layer is beneficial to improving the cycling stability of palladium-coated ZrCo alloy.

[0065] The microstructure and elemental distribution of the cyclic Pd@ZrCo and Pd / Pd3Zr@ZrCo samples were analyzed by SEM and EDS. The results are as follows: Figure 7 , Figure 8 As shown, the Pd film on the surface of the cycled Pd@ZrCo sample detaches, and a clear interface exists between the Pd film and the ZrCo matrix, indicating weak adhesion between the Pd film and the ZrCo matrix. However, the Pd / Pd3Zr@ZrCo sample does not exhibit film detachment after cycling and retains a significant amount of Pd, demonstrating that constructing the Pd / Pd3Zr@ZrCo alloy matrix composite structure effectively solves the problem of palladium film detachment during the hydrogen absorption / desorption process of the palladium-coated ZrCo alloy. This is partly due to the stable thermodynamic properties of Pd3Zr and its inertness to hydrogen, allowing it to maintain structural stability during hydrogen absorption / desorption cycling. Furthermore, the new Pd3Zr phase formed at the Pd / ZrCo interface can coherently interact with both Pd and ZrCo, thus the Pd3Zr transition layer acts as an anchor point for Pd on the ZrCo matrix, effectively suppressing film detachment. During cycling, the stable film layer that is well bonded to the substrate is not easily detached and can continuously protect the ZrCo substrate from oxygen poisoning. Therefore, the Pd / Pd3Zr@ZrCo sample exhibits high cycling stability.

[0066] Furthermore, it should be understood that after reading the above description of the present invention, those skilled in the art can make various alterations or modifications to the present invention, and these equivalent forms also fall within the scope defined by the appended claims.

Claims

1. A method for preparing a palladium-coated ZrCo hydrogen storage alloy with resistance to oxygen poisoning and long-term cycling stability, characterized in that, Palladium-coated ZrCo alloy particles were subjected to dynamic vacuuming at 500–550°C for 5–55 minutes and then cooled to obtain the palladium-coated ZrCo hydrogen storage alloy. The palladium-coated ZrCo hydrogen storage alloy has a composite structure consisting of an outer palladium coating layer, a Pd3Zr transition layer, and a ZrCo alloy matrix, wherein the Pd3Zr forms a coherent relationship with the outer Pd layer and the inner ZrCo alloy matrix.

2. The preparation method according to claim 1, characterized in that, The palladium content in the palladium-coated ZrCo hydrogen storage alloy is 5% to 15% by mass.

3. The preparation method according to claim 1, characterized in that, The method for preparing the palladium-plated ZrCo alloy particles includes the following steps: (1) Place Zr and Co elemental raw materials in stoichiometric ratio into a magnetic levitation induction melting furnace, and melt-cool solidify under argon atmosphere protection to obtain ZrCo alloy ingots. (2) ZrCo alloy ingots are crushed into particles by hydrogenation pulverization to obtain hydrogen-absorbing ZrCo alloy particles. (3) Place the hydrogen-absorbing ZrCo alloy particles in a reactor and dynamically vacuum them at 540-560°C for 50-70 minutes to obtain fine ZrCo alloy particles. (4) Place the fine ZrCo alloy particles in a fluorination solution and stir at 65-75°C for 0.5-1.5 hours to fluorinate them. Then wash the particles with deionized water at 65-75°C to remove impurities from the particle surface and obtain fluorinated ZrCo alloy particles. (5) Place the fluorinated ZrCo alloy particles in a sensitization solution and stir for 1 to 2 minutes at room temperature to sensitize them. Wash the impurities on the particle surface with deionized water to obtain sensitized ZrCo alloy particles. (6) Place the sensitized ZrCo alloy particles in an activation solution and stir for 1 to 2 minutes at room temperature to activate them. Wash the surface impurities of the particles with deionized water to obtain activated ZrCo alloy particles. (7) Place the activated ZrCo alloy particles in the plating solution and stir at 45-55°C for 15-25 minutes to perform electroless palladium plating. Wash the impurities on the particle surface with deionized water and remove water by vacuum at 75-85°C to obtain the palladium-plated ZrCo alloy particles.

4. The preparation method according to claim 3, characterized in that, In step (4): The solute in the fluorinated solution is 0.5-1.5 mL / L hydrofluoric acid and 0.5-1.5 g / L potassium fluoride, and the mass concentration of HF in the hydrofluoric acid is 48%-50%. The mass ratio of the ZrCo alloy fine particles to the volume of the fluorinated solution is 2-4 g: 200 mL.

5. The preparation method according to claim 3, characterized in that, In step (5): The solute in the sensitization solution is 4-6 g / L stannous chloride and 15-25 mL / L hydrochloric acid, wherein the mass concentration of HCl in the hydrochloric acid is 36%-38%. The mass ratio of the fluorinated ZrCo alloy particles to the volume of the sensitized solution is 2-4 g: 200 mL.

6. The preparation method according to claim 3, characterized in that, In step (6): The solute in the activation solution is 0.2-0.3 g / L palladium chloride and 2-3 mL / L hydrochloric acid, wherein the mass concentration of HCl in the hydrochloric acid is 36%-38%. The mass ratio of the sensitized ZrCo alloy particles to the volume of the activation solution is 2-4 g: 200 mL.

7. The preparation method according to claim 3, characterized in that, Each execution of steps (5) and (6) is recorded as one sensitization-activation process. Steps (5) and (6) are repeated for a total of 2 to 4 sensitization-activation processes.

8. The preparation method according to claim 3, characterized in that, In step (7): The solutes in the plating solution are 4-5 g / L palladium chloride, 45-55 g / L disodium ethylenediaminetetraacetate, 45-55 mg / L ammonium chloride, 0.04-0.06 mol / L hydrazine hydrate, and 240-260 mL / L ammonia water, wherein the mass concentration of NH3 in the ammonia water is 25%-28%. The ratio of the mass of the activated ZrCo alloy particles to the volume of the plating solution is 2-4 g: 100 mL.

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