A porous platinum for magnesium melt de-alloying and a method for preparing the same

Abstract

The application discloses a magnesium melt de-alloying porous platinum and a preparation method thereof, and relates to the technical field of precious metal material preparation.The preparation method of the magnesium melt de-alloying porous platinum comprises the following steps: first, pre-treating a platinum-based binary alloy to obtain an alloy sample; then, placing the alloy sample in a liquid magnesium melt to perform liquid de-alloying treatment, and in-situ forming a porous platinum skeleton structure material; and finally, performing acid pickling, cleaning and drying on the porous platinum skeleton structure material to obtain the magnesium melt de-alloying porous platinum.The porous platinum skeleton is in-situ formed through liquid de-alloying, has a continuous three-dimensional ligament network structure, a high specific surface area and good structural stability, and can avoid the problems of serious precious metal loss, limited de-alloying depth and environmental pollution in the traditional acid de-alloying process.The porous platinum material prepared by the application has uniform pore structure, good skeleton integrity, excellent catalytic activity and mass transfer performance, and has a wide application prospect in the fields of electrochemistry, sensors and energy storage.

Description

Technical Field

[0001] This invention relates to a porous platinum de-alloying process for magnesium melt and its preparation method, belonging to the field of precious metal material preparation technology. Background Technology

[0002] Porous platinum materials, due to their high specific surface area, excellent electrical conductivity, good chemical stability, and abundant surface active sites, have broad application prospects in fuel cells, electrocatalysis, electrochemical sensors, energy storage devices, and energy conversion. In particular, porous Pt framework materials with continuous three-dimensional interconnected structures can not only significantly increase the number of reactive sites but also enhance electron transport and mass diffusion performance, thus becoming an important research direction in the field of porous noble metal materials.

[0003] The preparation methods for porous Pt materials mainly include chemical etching dealloying, electrochemical dealloying, template methods, high-temperature volatilization, and nanoparticle assembly. Among these, acid etching and electrochemical dealloying are more widely used. However, these methods still have the following problems: (1) Strong acids, strong bases or complex electrolytes are usually required in the dealloying process, which causes significant environmental pollution.

[0004] (2) Traditional dealloying methods have low mass transfer rates and limited dealloying depths, and are prone to surface passivation and internal composition gradients. They are usually only suitable for small-sized samples with a thickness of tens to hundreds of micrometers. It is difficult to achieve uniform and continuous dealloying for raw materials with a thickness greater than 1 mm.

[0005] (3) During the dealloying process, the pore structure is easily coarsened and the skeleton collapses, making it difficult to obtain a uniform and continuous three-dimensional porous structure.

[0006] (4) Precious metals are prone to dissolution loss during the dealloying process, which leads to a decrease in the utilization rate of precious metals and an increase in preparation costs.

[0007] (5) The relevant dealloying methods are mainly applicable to small-sized samples with low acid sensitivity. The application range of the process is limited and it is difficult to meet the needs of complex alloy systems and large-scale preparation.

[0008] Therefore, in order to obtain a uniform and continuous three-dimensional porous platinum structure and solve the problems of pore structure coarsening and skeleton collapse caused by the dealloying process, it is necessary to develop a method that utilizes the thermodynamic miscibility and diffusion rate difference between magnesium melt and non-precious metal components of platinum-based binary alloy to selectively remove non-precious metal components and form a continuous porous platinum skeleton structure in situ. Summary of the Invention

[0009] To address the shortcomings of related technologies, this invention provides a porous platinum solution for magnesium melt dealloying and its preparation method. Utilizing the thermodynamic miscibility and diffusion rate differences between the magnesium melt and the non-precious metal components of a platinum-based binary alloy, the selective removal of the non-precious metal components is achieved, resulting in the in-situ formation of a continuous porous platinum framework structure. The prepared porous platinum possesses a continuous, interconnected three-dimensional ligament network structure, high specific surface area, and good structural stability. It exhibits uniform pore structure, good framework integrity, and excellent catalytic activity and mass transfer performance. This invention solves the problems of low dealloying efficiency, significant environmental pollution, easy framework collapse, and limited applicability in traditional dealloying methods.

[0010] One objective of this invention is to provide a method for preparing porous platinum from magnesium melt dealloying, specifically comprising the following steps: (1) The platinum-based binary alloy was pretreated to obtain an alloy sample.

[0011] (2) Melt pure magnesium raw materials to obtain liquid magnesium melt.

[0012] (3) The alloy sample is placed in liquid magnesium melt for liquid dealloying treatment to form a porous platinum skeleton structure material in situ.

[0013] (4) The porous platinum skeleton material is taken out, and after pickling, cleaning and drying, a magnesium melt dealloying porous platinum is obtained.

[0014] Preferably, in step (1), the platinum-based binary alloy is either a Pt-Ni alloy or a Pt-Cu alloy, and the atomic ratio of Pt to Ni or Cu in the platinum-based binary alloy is 10:90 to 70:30, and the sum of the atomic percentages of Pt and Ni or Cu is 100%.

[0015] Preferably, the alloy sample in step (1) is in the form of strip or sheet with a thickness of 0.2~1.0 mm.

[0016] More preferably, the alloy sample in step (1) is in the form of a thin sheet.

[0017] More preferably, the pretreatment method in step (1) is to cut, grind and clean the platinum-based binary alloy.

[0018] Preferably, in step (2), the pure magnesium raw material is smelted under a protective atmosphere; the smelting temperature is 650~800℃.

[0019] More preferably, the protective atmosphere in step (2) is one or a combination of argon, helium, and nitrogen.

[0020] Preferably, in step (3), the alloy sample is added to the liquid magnesium melt at a mass ratio of 1:(10~30) of the alloy sample to the liquid magnesium melt; the liquid dealloying treatment time is 5~20 min.

[0021] Preferably, the pickling solution in step (4) is one or more of hydrochloric acid, nitric acid, acetic acid, and ammonium chloride aqueous solution, and the concentration of the pickling solution is 0.01~0.5mol / L.

[0022] More preferably, the pickling solution in step (4) is one of nitric acid, acetic acid, or ammonium chloride aqueous solution, and the concentration of the pickling solution is 0.5 mol / L.

[0023] More preferably, the cleaning in step (4) is carried out using one or more cleaning media selected from deionized water, anhydrous ethanol, and acetone, and the number of cleaning cycles is 1 to 10, with each cleaning cycle lasting 1 to 30 minutes; the drying is carried out using one or more of vacuum drying, inert atmosphere (such as argon) drying, or air drying, with a drying temperature of 40 to 120°C and a drying time of 1 to 24 hours.

[0024] The porous platinum framework structure material prepared by the method of the present invention has a continuous ligament network structure with a pore size of 10nm~100nm.

[0025] In step (3) of this invention, the difference in thermodynamic miscibility and diffusion driving force between Mg melt and platinum-based binary alloy is utilized to allow Ni or Cu elements to preferentially diffuse and dissolve into Mg melt, while Pt elements are retained and gradually form a continuous porous Pt skeleton structure in situ.

[0026] Another object of the present invention is to provide a magnesium melt dealloying porous platinum prepared by the present method.

[0027] Mechanism of the invention: This invention uses Pt-Ni or Pt-Cu binary alloys as precursors, with Ni or Cu as the main sacrificial component. Utilizing the solubility of Ni or Cu in liquid Mg, Ni or Cu continuously migrates from the interior of the alloy into the Mg melt, while Pt remains in situ and gradually forms a porous framework. This invention selectively extracts Ni or Cu directly from the Pt-based binary alloy. In this invention, Ni is primarily removed as a sacrificial component, its role being to provide space for pore formation and Pt framework reconstruction by migrating from the Pt-Ni alloy. The properties of the material obtained by this invention mainly stem from the synergistic effect of the high specific surface area, abundant active sites, continuous conductive network, and interconnected mass transfer channels of the porous Pt framework itself. Through the continuous migration of Ni or Cu from the interior of the sample into the Mg melt, this invention gradually transforms the original Pt-based binary alloy into one with Pt ligaments. The Pt material is a continuous three-dimensional porous framework with Ni or Cu as the main component. The target structure does not rely on the undealloyed amorphous matrix for support. As Ni or Cu is removed, the remaining Pt atoms are enriched, rearranged, and connected under the influence of reduced interfacial energy and surface diffusion, gradually forming a continuous and interconnected network of pores and ligaments, thereby obtaining a porous Pt material with good integrity and self-support. This invention is carried out in a high-temperature liquid Mg environment. The dealloying process is mainly driven by the chemical potential difference, thermodynamic dissolution tendency, and concentration gradient of Ni or Cu between the Pt-based alloy and the Mg melt. Ni or Cu diffuses from the interior of the alloy to the solid-liquid interface, then crosses the interface and dissolves into the liquid Mg. It is then carried away from the vicinity of the interface through liquid-phase mass transfer. The continuous containment and transport of Ni or Cu by the liquid Mg can maintain the concentration gradient at the solid-liquid interface, providing a continuous driving force for the further outward diffusion of non-noble metal components.

[0028] The beneficial effects of this invention are: This invention utilizes the differences in thermodynamic miscibility and diffusion rates between magnesium melt and non-precious metal components in platinum-based binary alloys to synergistically achieve the selective removal of non-precious metal components. During the dealloying process, Ni or Cu preferentially diffuses into the Mg melt and dissolves under the drive of chemical potential and concentration gradients, while Pt, due to its low miscibility with Mg, can remain in situ. As the non-precious metal components continue to migrate and be removed, the remaining Pt atoms undergo continuous rearrangement and connection under the drive of interfacial diffusion and energy minimization, gradually forming a continuous and interconnected three-dimensional porous framework structure. This process, through the synergistic effect of rapid mass transfer and in-situ self-supporting framework construction, effectively avoids the problems of surface passivation, framework collapse, and precious metal loss that easily occur in traditional acid dealloying processes, thereby obtaining porous platinum with uniform pore structure, good connectivity, and high structural stability. Compared with traditional acid corrosion and electrochemical dealloying methods, this invention has the following advantages: (1) The element diffusion rate is fast during the dealloying process of liquid Mg, which can achieve deep and uniform dealloying of large-sized samples. (2) No large amount of strong acid or complex electrolyte is required, resulting in less environmental pollution and a green and environmentally friendly process.

[0029] (3) The obtained porous Pt skeleton has a uniform and continuous three-dimensional ligament network structure with good pore connectivity.

[0030] (4) The Pt skeleton has a low dissolution loss during the dealloying process, which is beneficial to improving the utilization rate of precious metals.

[0031] (5) The obtained porous Pt material has a high specific surface area and excellent structural stability, and has good application prospects in the fields of electrocatalysis, fuel cells and energy conversion.

[0032] (6) The porous platinum material prepared by the present invention has a uniform pore structure, good framework integrity, and excellent catalytic activity and mass transfer performance. Attached Figure Description

[0033] Figure 1 This is a microscopic image of the porous platinum melt dealloyed from magnesium melt prepared in Example 1 of the present invention.

[0034] Figure 2 This is a microscopic image of the porous platinum melt dealloyed from magnesium melt prepared in Example 2 of the present invention.

[0035] Figure 3 This is a microscopic image of the porous platinum melt dealloyed from magnesium melt prepared in Example 3 of the present invention. Detailed Implementation

[0036] To better illustrate the purpose, technical solution, and advantages of this invention, the invention will be further described below with reference to specific embodiments. In the embodiments and comparative examples of this invention, unless otherwise specified, all chemical reagents used were commercially available analytical grade reagents.

[0037] Example 1 A method for preparing porous platinum from magnesium melt dealloying specifically includes the following steps: (1) The Pt-Ni alloy was cut into thin slices with a size of 10mm×10mm×1.0mm (the atomic ratio of Pt to Ni in the Pt-Ni alloy is 70:30, and the sum of the atomic percentages of Pt and Ni is 100%). The slices were polished step by step with sandpaper, and then ultrasonically cleaned once with acetone, anhydrous ethanol and deionized water in sequence. Each cleaning time was 5min. After that, the sample was dried to remove moisture and the alloy sample was obtained.

[0038] (2) Place the pure magnesium block in a crucible and melt it at 800°C for 30 minutes under an argon atmosphere to obtain a stable molten liquid magnesium melt.

[0039] (3) The alloy sample was placed in the liquid magnesium melt for 20 min of liquid dealloying treatment (the alloy sample was immersed in the liquid magnesium melt), wherein the alloy sample was immersed in the liquid magnesium melt at a mass ratio of 1:30. During the dealloying process, Ni preferentially diffused and dissolved into the Mg melt, while Pt was retained and gradually formed a porous platinum skeleton structure material in situ.

[0040] (4) The porous platinum framework material was taken out and cooled naturally. Then it was placed in a 0.5 mol / L nitric acid aqueous solution for 30 min to remove residual Mg and reaction products. Then it was ultrasonically cleaned once with acetone, anhydrous ethanol and deionized water in sequence, each time for 5 min. Finally, it was dried at 120℃ for 1 h under argon atmosphere to obtain magnesium melt dealloyed porous platinum.

[0041] The obtained porous Pt skeleton SEM morphology is as follows Figure 1 As shown, by Figure 1 It can be seen that after dealloying, a uniform and continuous porous ligament network structure was formed, with good connectivity of the pore structure and no obvious skeletal collapse was observed.

[0042] The porous Pt metal framework prepared using Example 1 of the present invention has a specific surface area that is about 12 times larger than that of the original Pt-Ni alloy, and also has excellent structural stability.

[0043] Example 2 A method for preparing porous platinum from magnesium melt dealloying specifically includes the following steps: (1) Cut the Pt-Cu alloy into thin slices with dimensions of 10mm×10mm×0.5mm (the atomic ratio of Pt to Cu in the Pt-Cu alloy is 50:50, and the sum of the atomic percentages of Pt and Cu is 100%), and polish them step by step with sandpaper. Then, clean them once with acetone, anhydrous ethanol, and deionized water in sequence, with each cleaning time being 5min. After that, dry them to remove moisture and obtain the alloy sample.

[0044] (2) Place the pure magnesium block in a crucible and melt it at 720°C for 25 minutes under a nitrogen atmosphere to obtain a stable molten liquid magnesium melt.

[0045] (3) The alloy sample is placed in the liquid magnesium melt for 10 min of liquid dealloying treatment (the alloy sample is immersed in the liquid magnesium melt), wherein the alloy sample is immersed in the liquid magnesium melt at a mass ratio of 1:20 of the alloy sample and the liquid magnesium melt; during the dealloying process, Pt is retained and gradually forms a porous platinum skeleton structure material in situ.

[0046] (4) The porous platinum framework material was taken out and cooled naturally. Then it was placed in a 0.5 mol / L ammonium chloride aqueous solution for 20 min to remove residual Mg and reaction products. Then it was ultrasonically cleaned once with acetone, anhydrous ethanol and deionized water in sequence, each time for 5 min. Finally, it was dried in a vacuum drying oven at 80℃ for 10 h to obtain magnesium melt dealloyed porous platinum.

[0047] The obtained porous Pt skeleton SEM morphology is as follows Figure 2 As shown, by Figure 2 It can be seen that after dealloying, a uniform and continuous three-dimensional porous ligament network structure was formed, with a relatively uniform distribution of pores, and no obvious cracks or collapses were observed on the surface of the skeleton.

[0048] The porous Pt framework prepared using Example 2 of this invention has a specific surface area that is about 15 times larger than that of the original Pt-Cu alloy, and it also has excellent electrical conductivity and structural stability, showing promising application prospects in the fields of electrocatalysis and fuel cells.

[0049] Example 3 A method for preparing porous platinum from magnesium melt dealloying specifically includes the following steps: (1) The Pt-Ni alloy was cut into thin slices with dimensions of 10 mm × 10 mm × 0.2 mm (the atomic ratio of Pt to Ni in the Pt-Ni alloy is 10:90, and the sum of the atomic percentages of Pt and Ni is 100%), and polished step by step with sandpaper. Then, it was ultrasonically cleaned once with acetone, anhydrous ethanol, and deionized water in sequence, with each cleaning time being 5 min; then dried to remove moisture, and the alloy sample was obtained.

[0050] (2) Place the pure magnesium block in a crucible and melt it at 650°C for 60 minutes under a helium atmosphere to obtain a stable molten liquid magnesium melt.

[0051] (3) The alloy sample was placed in the liquid magnesium melt for 5 minutes for liquid dealloying treatment (the alloy sample was immersed in the liquid magnesium melt), wherein the alloy sample was immersed in the liquid magnesium melt at a mass ratio of 1:10. During the dealloying process, Ni preferentially diffused and dissolved into the Mg melt, while Pt was retained and gradually formed a porous platinum skeleton structure material in situ.

[0052] (4) The porous platinum framework material was removed and allowed to cool naturally. Then it was placed in a 0.5 mol / L acetic acid solution for 30 min to remove residual Mg and reaction products. Then it was ultrasonically cleaned once with acetone, anhydrous ethanol and deionized water, each time for 5 min. Finally, it was dried at 40 °C for 24 h in air atmosphere to obtain magnesium melt dealloyed porous platinum.

[0053] Depend on Figure 3 The obtained SEM morphology of the porous Pt skeleton shows that the porous Pt skeleton prepared by Example 3 of the present invention has a uniform pore structure and good connectivity, indicating that under the process parameters of this example, the effective selective removal of Ni element in Pt-Ni alloy can be achieved, and a structurally stable continuous porous Pt skeleton can be obtained.

[0054] The porous Pt metal framework prepared using Example 3 of the present invention has a specific surface area that is about 13 times larger than that of the original Pt-Ni alloy, and also has excellent structural stability.

[0055] Comparative Example 1 A method for preparing porous platinum specifically includes the following steps: (1) Cut the Pt-Cu alloy into thin slices with dimensions of 10mm×10mm×0.5mm (the atomic ratio of Pt to Cu in the Pt-Cu alloy is 50:50, and the sum of the atomic percentages of Pt and Cu is 100%), and polish them step by step with sandpaper. Then, clean them once with acetone, anhydrous ethanol, and deionized water in sequence, with each cleaning time being 5min. After that, dry them to remove moisture and obtain the alloy sample.

[0056] (2) The alloy sample was completely immersed in a 1 mol / L HNO3 aqueous solution and soaked for 20 h at room temperature to obtain the crude de-alloyed product.

[0057] (3) The crude product of dealloying was washed once with deionized water and once with anhydrous ethanol. Each washing time was 5 min, and the product was dried in vacuum at 60℃ for 12 h to obtain porous platinum.

[0058] SEM observation revealed that the porous platinum prepared in this comparative example only formed a porous Pt structure on the surface, while the interior still retained undealloyed regions. The pore structure uniformity was poor, and the dealloying time was long. This is because the comparative example used an acid leaching dealloying method, which mainly relies on the electrochemical dissolution reaction between the acid and the Cu component in the alloy. As dealloying proceeds, a continuous Pt enrichment layer gradually forms on the surface. This Pt layer hinders the further penetration of the acid into the alloy interior and reduces the diffusion rate of Cu atoms to the surface. As a result, the dealloying reaction is gradually limited by both mass transfer and solid-state diffusion processes, leading to a limited dealloying depth. A porous structure is only formed on the surface of the material, making it difficult to obtain a three-dimensional continuous porous Pt framework that runs through the entire sample.

[0059] Comparative Example 2 A method for preparing porous platinum specifically includes the following steps: (1) The Pt-Ni alloy was cut into thin slices with a size of 10mm×10mm×0.5mm (the atomic ratio of Pt to Ni in the Pt-Ni alloy is 30:70, and the sum of the atomic percentages of Pt and Ni is 100%). The slices were polished step by step with sandpaper, and then ultrasonically cleaned once with acetone, anhydrous ethanol and deionized water, with each cleaning time being 5min. After that, the sample was dried to remove moisture and the alloy sample was obtained.

[0060] (2) Using the alloy sample as the working electrode, Pt sheet as the counter electrode, and Ag / AgCl as the reference electrode, cyclic voltammetric dealloying was performed in 0.1 mol / L HClO4 aqueous solution. The scanning potential range was 0.05~1.2V (converted to a reversible hydrogen electrode, i.e., RHE system), the scanning rate was 50 mV / s, and a total of 20 voltammetric cycles were performed to obtain the crude dealloying product.

[0061] (3) The crude product of dealloying was washed once with deionized water and once with anhydrous ethanol. Each washing time was 5 min, and the product was dried in vacuum at 60℃ for 12 h to obtain porous platinum.

[0062] SEM observation revealed that a porous Pt layer was formed on the porous platinum surface prepared in this comparative example, but dealloying mainly occurred in the near-surface region, making it difficult to achieve uniform dealloying of the entire sample for thicker samples.

[0063] This demonstrates that traditional dealloying methods are limited by element diffusion rates and mass transfer processes, making it difficult to achieve deep and uniform dealloying of Pt-based alloys. In contrast, the magnesium melt liquid dealloying method of this invention can achieve rapid and selective removal of non-precious metal components and obtain a continuous and uniform porous Pt framework structure.

[0064] This invention utilizes molten liquid magnesium as a selective dissolution medium. Through high-temperature driving, non-noble metal components (Ni or Cu) in Pt-Ni or Pt-Cu precursors continuously migrate to and are removed from the magnesium melt, allowing Pt atoms to remain in situ and self-assemble collaboratively to form a porous framework with a continuous, interconnected three-dimensional network. This method not only achieves deep, uniform dealloying of large-sized samples, effectively avoiding the surface passivation, framework collapse, and noble metal loss problems that easily occur in traditional acid corrosion, but also yields a porous Pt framework with high specific surface area, abundant active sites, a continuous conductive network, and excellent mass transfer channels, showing promising application prospects in electrocatalysis, fuel cells, and energy conversion.

[0065] The various embodiments of the present invention have been described above. These descriptions are exemplary and not exhaustive, nor are they limited to the disclosed embodiments. Many modifications and variations will be apparent to those skilled in the art without departing from the scope and spirit of the described embodiments. The terminology used herein is chosen to best explain the principles, practical application, or improvement of the technology in the market, or to enable others skilled in the art to understand the embodiments disclosed herein.

Claims

1. A method for preparing porous platinum from magnesium melt dealloying, characterized in that, Specifically, the following steps are included: (1) The platinum-based binary alloy was pretreated to obtain an alloy sample; (2) Melt pure magnesium raw materials to obtain liquid magnesium melt; (3) The alloy sample was placed in liquid magnesium melt for liquid dealloying treatment to form a porous platinum skeleton structure material in situ; (4) The porous platinum skeleton material is taken out, and after acid washing, cleaning and drying, a magnesium melt dealloying porous platinum is obtained.

2. The method for preparing porous platinum from magnesium melt dealloying according to claim 1, characterized in that, In step (1), the platinum-based binary alloy is either a Pt-Ni alloy or a Pt-Cu alloy. The atomic ratio of Pt to Ni or Cu in the platinum-based binary alloy is 10:90 to 70:30, and the sum of the atomic percentages of Pt and Ni or Cu is 100%.

3. The method for preparing porous platinum from magnesium melt dealloying according to claim 1, characterized in that, The alloy sample in step (1) is in strip or sheet form with a thickness of 0.2~1.0 mm.

4. The method for preparing porous platinum from magnesium melt dealloying according to claim 1, characterized in that, In step (2), the pure magnesium raw material is smelted under a protective atmosphere; the smelting temperature is 650~800℃.

5. The method for preparing porous platinum from magnesium melt dealloying according to claim 1, characterized in that, In step (3), the alloy sample is added to the liquid magnesium melt at a mass ratio of 1:(10~30); the liquid dealloying treatment takes 5~20 minutes.

6. The method for preparing porous platinum from magnesium melt dealloying according to claim 1, characterized in that, The pickling solution in step (4) is one or more of hydrochloric acid, nitric acid, acetic acid, and ammonium chloride aqueous solution, and the concentration of the pickling solution is 0.01~0.5mol / L.

7. The magnesium melt dealloying porous platinum prepared by the method according to any one of claims 1 to 6.

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