A composite hydrogen filtration membrane with an amorphous nickel-tungsten alloy as the intermediate diffusion layer and a preparation method thereof

Abstract

The present invention relates to a composite hydrogen filtration membrane with an amorphous nickel-tungsten alloy as an intermediate diffusion layer and a preparation method thereof. The composite hydrogen filtration membrane is composed of a porous alumina ceramic support, an amorphous nickel-tungsten layer, and a pure palladium layer. First, the porous ceramic support is pretreated, and its surface is sensitized and activated by a dilute hydrochloric acid solution of SnCl2 and PdCl2, and then a layer of pure palladium is plated by electroless plating. Then, an amorphous nickel-tungsten layer is obtained by electroplating, and finally, a pure palladium layer is electrolessly plated on the surface. The pure palladium layer provides the dissociation and desorption of hydrogen. On the one hand, the amorphous nickel-tungsten layer provides better strength and ductility, ensuring the long-term stable operation of the composite membrane. On the other hand, it replaces part of the palladium material with a material of lower price, reducing the manufacturing cost of the composite hydrogen filtration membrane. Since the tungsten element with a lower hydrogen retention amount is used as an alloying element and has a unique amorphous structure, the amorphous nickel-tungsten alloy layer prepared by the present invention is not prone to hydrogen embrittlement caused by the accumulation of hydrogen atoms during the diffusion process of hydrogen atoms.

Description

Technical Field

[0001] The present invention relates to a palladium-based composite hydrogen permeable membrane with an amorphous nickel-tungsten alloy as an intermediate diffusion layer and a preparation method thereof, belonging to the technical field of hydrogen purification. Specifically, it relates to a composite hydrogen permeable membrane with electroplated amorphous nickel-tungsten alloy as a diffusion layer and electrolessly plated pure palladium as a hydrogen separation and desorption layer, and a preparation method thereof. Background Art

[0002] With the increasing energy demand of society, hydrogen energy is widely regarded as an effective alternative to traditional fossil fuels. Compared with traditional fossil fuels, hydrogen energy has a higher calorific value and can generate more heat with the same mass. In addition, with the impact of human activities and climate change on the environment, the pollution problems of traditional energy are also increasingly concerned. As a clean energy, hydrogen energy only produces water during combustion and hardly pollutes the environment, having great application potential.

[0003] Traditional hydrogen production methods mainly include fossil fuel hydrogen production, industrial by-product hydrogen production, electrolytic hydrogen production, biomass hydrogen production, etc. The hydrogen produced often contains by-products such as carbon monoxide, carbon dioxide, and sulfides, and cannot be directly used in fuel cell systems or as raw materials for chemical products. Therefore, developing efficient hydrogen purification technology is one of the keys to realizing the application of hydrogen energy in energy substitution and chemical industry.

[0004] Currently, the separation and purification of hydrogen are mainly carried out by pressure swing adsorption, cryogenic distillation, and membrane separation methods. Among them, compared with the other two methods, the membrane separation method has lower requirements for equipment, smaller required equipment units, and lower energy consumption, and is very suitable for the production of small-scale high-purity hydrogen. Moreover, the hydrogen obtained by the membrane separation method has a higher purity compared with other methods.

[0005] The commonly used membrane materials for the membrane separation method can be divided into supported membranes and self-supported membranes. Among them, self-supported membranes are generally obtained by the melting and rolling method; supported membranes are obtained by depositing a polymer membrane or a metal membrane on the surface of a support. The hydrogen permeation efficiency of self-supported membranes is limited by the thickness of the membrane, and it is difficult to obtain micron-scale membrane materials by rolling; supported membranes can obtain membrane materials with a thickness of microns or even nanometers on the surface of a porous support, greatly reducing the hindrance of the membrane thickness to the hydrogen permeation efficiency. Among them, compared with metal membranes, polymer supported membranes have low selectivity for hydrogen, it is difficult to obtain high-purity hydrogen, and their mechanical properties are worse than those of metal membranes, making it difficult to be applied in high-temperature and high-pressure environments.

[0006] The commonly used support materials for supported membranes include porous ceramics, porous glass, and porous stainless steel. Compared with the other two, porous ceramics are not prone to element diffusion and pore structure collapse, have good thermal stability and chemical stability, and also have good compatibility with metal membranes. In addition, the forming process of porous ceramics is relatively simple, and the micro-nano scale pore diameter is conducive to the adhesion of metal membranes.

[0007] The metal film materials on the surface of the support film can be divided into crystalline and amorphous types. Currently, relatively mature palladium-silver films, palladium-copper films, palladium-gold films, palladium-ruthenium films, etc. all belong to crystalline metal films. Due to their high hydrogen solubility, these crystalline metal films can exhibit high hydrogen permeability during application. The permeation of hydrogen depends on the solubility of hydrogen atoms in the metal on the one hand and the diffusivity of hydrogen atoms in the metal on the other hand. Amorphous alloys achieve hydrogen permeation through a high diffusivity of hydrogen atoms. On the one hand, this is because amorphous alloys have a unique atomic stacking structure and do not have the characteristics of crystalline materials such as grains, grain boundaries, and dislocations; on the other hand, it is because amorphous alloys have a lower density compared to crystalline materials of the same composition, their atomic packing density is less than that of crystalline alloys, and there are more voids to absorb hydrogen atoms and provide a fast channel for hydrogen atoms to diffuse in the film.

[0008] Compared with vanadium, niobium, tantalum and their alloys that absorb hydrogen atoms in the form of metal hydrides (M-H) to achieve high hydrogen solubility, amorphous alloys mainly store hydrogen atoms in the voids of atomic packing. During use, although the hydrogen permeation efficiency of crystalline materials such as vanadium and niobium is high, most of them will show serious hydrogen embrittlement phenomena, which affect their service life. Due to its unique structure, amorphous materials eliminate defects such as grain boundaries and dislocations and have good hydrogen embrittlement resistance; and during use, hydrogen atoms can be enriched in the amorphous alloy to produce "lattice expansion", which is beneficial to hydrogen permeation. Therefore, amorphous alloys have obvious advantages as hydrogen permeable materials.

[0009] Currently, most hydrogen permeable metal films are obtained by melting. For example, a Chinese patent (publication number CN1990094A) discloses a method for preparing a hydrogen permeable membrane. A nickel-zirconium alloy ingot is prepared by melting, and then the ingot is remelted and pressure-sprayed onto a water-cooled copper roller to form an amorphous nickel-zirconium alloy foil. A Chinese patent (publication number CN110306096A) discloses a nickel / titanium / vanadium nanowire alloy hydrogen permeable membrane, which is also prepared by first obtaining an alloy ingot by melting and then forging and drawing. The melting process consumes a large amount of energy, the preparation environment is highly dangerous, and it is difficult to obtain micro-nano scale thin films. The thickness of the alloy film seriously hinders the hydrogen permeation efficiency.

[0010] The present invention uses a method combining electroless plating and electroplating to prepare a palladium-based composite hydrogen filtration membrane with an amorphous nickel-tungsten alloy as the intermediate diffusion layer. The preparation method is simple, requires low equipment, consumes less energy, has good safety in the working environment, and by controlling parameters such as time and current, micro-nano scale thin films can be obtained, reducing the hindrance of thickness to hydrogen permeation efficiency, and is suitable for popularization and application. Summary of the Invention

[0011] The present invention aims to develop a palladium-nickel-tungsten-palladium composite hydrogen permeable membrane with an amorphous alloy as the intermediate diffusion layer on the surface of a porous ceramic support and a method therefor.

[0012] To achieve the above object, the specific content of the present invention is as follows:

[0013] A composite hydrogen permeable membrane with an amorphous nickel-tungsten alloy as the intermediate diffusion layer, the composite membrane comprising a porous alumina ceramic support, a pure palladium layer A, an amorphous nickel-tungsten layer, and a pure palladium layer B; wherein the porous alumina ceramic support may be a tubular porous alumina ceramic or a sheet-shaped alumina ceramic, with a pore diameter of 30 nm to 2 μm and a porosity of 20% to 40%; the thicknesses of the pure palladium layer A and the pure palladium layer B are 0.5 to 5 μm, the thickness of the amorphous nickel-tungsten layer is 1 to 20 μm, and the total thickness of the alloy hydrogen permeable membrane is 2 to 30 μm.

[0014] A method for preparing a composite hydrogen permeable membrane with an amorphous nickel-tungsten alloy as the intermediate diffusion layer, the method comprising the following steps:

[0015] (1) Surface pretreatment of the porous alumina ceramic support

[0016] The porous alumina ceramic support is successively placed in a NaOH solution with a concentration of 5 to 20 g / L and deionized water, and ultrasonically cleaned for 2 to 10 minutes to remove the oil and dust on the surface of the ceramic support;

[0017] (2) Sensitization and activation treatment of the ceramic support

[0018] ① The pretreated ceramic support is immersed in a SnCl2 / HCl sensitization solution and ultrasonically treated for 0.5 to 10 minutes for sensitization, and then placed in deionized water and ultrasonically cleaned for 10 to 60 seconds. The concentration of the sensitization solution is:

[0019] SnCl2: 3 to 10 g / L; HCl: 1 mL / L;

[0020] ② The sensitized ceramic support is placed in a PdCl2 / HCl activation solution and ultrasonically treated for 0.5 to 10 minutes for activation, and then placed in deionized water and ultrasonically cleaned for 10 to 60 seconds. The concentration of the activation solution is:

[0021] PdCl2: 0.1 to 0.5 g / L; HCl: 2 mL / L;

[0022] The above steps are repeated 3 to 10 times to uniformly deposit palladium nuclei on the surface of the ceramic support. At this time, the surface of the ceramic support shows a uniformly distributed dark brown color;

[0023] (3) Electroplating palladium on the surface of the activated ceramic support by electroless plating

[0024] Put the ceramic support processed in step (2) into the prepared palladium chloride electroless plating solution, place it in a water bath at a temperature of 40 - 70 °C, stir magnetically, add the hydrazine hydrate solution in portions every 5 - 30 min, replace the electroless plating solution after adding hydrazine hydrate 3 - 6 times, repeat the above operation 2 - 10 times, rinse the sample with deionized water for 30 - 90 s after taking it out, and dry it with cold air for standby; the concentration requirements of the palladium electroless plating solution are as follows:

[0025] PdCl2: 1 - 4 g / L; EDTA: 25 - 50 g / L; NH3·H2O (25% - 28%): 200 - 250 mL / L; hydrazine hydrate: 0.05 - 0.3 mol / L;

[0026] (4) Electroplate nickel - tungsten on the surface after electroless plating of palladium

[0027] Put the sample processed in step (3) into the nickel - tungsten plating solution, place it in a water bath at a temperature of 30 - 70 °C, use a pure nickel plate as the anode, set the on - off time and current, electroplate for 5 - 120 min, take out the sample, rinse it with deionized water for 30 - 90 s, and dry it with cold air for standby; the concentration requirements of the nickel - tungsten electroplating solution are as follows:

[0028] NiSO4·6H2O: 10 - 25 g / L; Na2WO4: 30 - 60 g / L; citric acid monohydrate: 15 - 80 g / L; NH3·H2O (25 - 28%): 2 - 50 mL / L;

[0029] The current parameter requirements are as follows:

[0030] Current density: 50 - 120 mA / cm 2 ;

[0031] Select the current as a positive - pulse current, the conduction time is equal to the turn - off time: 1 - 5 ms;

[0032] (5) Surface plating of palladium

[0033] Repeat steps (2) and (3) for the sample processed in step (4) to electrolessly plate palladium on the surface;

[0034] (6) Drying treatment

[0035] Put the sample plated with palladium in step (5) into a drying oven at a temperature of 100 °C and dry it for 2 - 4 h to obtain a composite hydrogen - permeable membrane with an amorphous nickel - tungsten alloy as the intermediate diffusion layer.

[0036] Compared with the prior art, the beneficial effects of the present invention are:

[0037] (1) Electroless plating has lower requirements for the substrate, the obtained pure palladium coating has a higher bonding strength with the substrate, and the concentration of the palladium solution required for electroless plating is lower, and the utilization rate of palladium in the solution is higher.

[0038] (2) Palladium is only used on both sides of the composite hydrogen filtration membrane for the dissociation and desorption of hydrogen, effectively reducing the usage amount of expensive palladium element and the manufacturing cost of the composite hydrogen filtration membrane.

[0039] (3) Compared with other metal alloys, hydrogen atoms are not easily formed into metal hydrides in the amorphous nickel-tungsten layer, with less hydrogen retention and not easily prone to hydrogen embrittlement, thus improving the service life of the composite hydrogen filtration membrane. Description of the Drawings

[0040] Figure 1 is a schematic structural diagram of a sheet-shaped composite hydrogen filtration membrane;

[0041] Figure 2 is an SEM photograph of the surface morphology of the electroplated amorphous nickel-tungsten layer;

[0042] Figure 3 is an EDS spectrum of the electroplated amorphous nickel-tungsten layer;

[0043] Figure 4 is an XRD spectrum of the electroplated amorphous nickel-tungsten layer;

[0044] Figure 5 is an SEM photograph of the surface morphology of the electrolessly deposited pure palladium layer;

[0045] Figure 6 is a schematic structural diagram of a tubular composite hydrogen filtration membrane. Specific Embodiments

[0046] The present invention will be further described below with reference to the accompanying drawings.

[0047] The object of the present invention is to develop a composite hydrogen permeation membrane with an amorphous intermediate diffusion layer. To achieve the above object, the present invention uses a porous alumina ceramic as a support, and obtains an amorphous nickel-tungsten intermediate diffusion layer by electroplating; deposits pure palladium layers on both sides of the amorphous nickel-tungsten intermediate diffusion layer by electroless plating as the dissociation and desorption layers of hydrogen.

[0048] Example 1:

[0049] A composite hydrogen filtration membrane with an amorphous nickel-tungsten alloy as the intermediate diffusion layer, the composite membrane includes a porous alumina ceramic support, pure palladium layer A, amorphous nickel-tungsten layer, pure palladium layer B; wherein the porous alumina ceramic support is a sheet-shaped alumina ceramic with a diameter of 18 mm, a thickness of 2 mm, a pore diameter of 70 nm, and a porosity of 30%; the average thicknesses of the obtained pure palladium layer A and pure palladium layer B are both 1.2 μm, the average thickness of the amorphous nickel-tungsten layer is 15 μm, and the average total thickness of the alloy hydrogen filtration membrane is 17.4 μm. The schematic diagram of the sheet-shaped composite hydrogen filtration membrane with an amorphous nickel-tungsten alloy as the intermediate diffusion layer is as Figure 1 shown.

[0050] The preparation method of the intermediate diffusion layer for the composite hydrogen permeable membrane of amorphous nickel-tungsten alloy includes the following steps:

[0051] (1) Surface pretreatment of the porous alumina ceramic support: Place a sheet-shaped porous alumina ceramic support with a diameter of 18 mm, a thickness of 2 mm, a pore diameter of 70 nm, and a porosity of 30% in a 10 g / L NaOH solution and deionized water in sequence, and ultrasonically clean for 5 min to remove surface impurities and oil stains. Then, blow dry the surface moisture with cold air for later use;

[0052] (2) Sensitization and activation treatment of the ceramic support

[0053] Prepare a 50 mL sensitizing solution containing 5 g / L SnCl2 and 1 mL / L HCl with deionized water;

[0054] Prepare a 25 mL activating solution containing 0.2 g / L PdCl2 and 2 mL / L HCl with deionized water;

[0055] Put the alumina ceramic support pretreated in step (1) into the sensitizing solution and ultrasonically treat for 3 min, then take it out and put it into a beaker containing deionized water for ultrasonic cleaning for 30 s, and then put it into the prepared activating solution for ultrasonic treatment for 3 min. After taking it out, put it into a beaker containing deionized water for ultrasonic cleaning for 30 s;

[0056] Repeat the above operation 5 times. The surface of the porous alumina ceramic shows uniform dark brown, and uniform palladium nuclei are obtained.

[0057] (3) Deposit palladium on the surface of the activated ceramic support by electroless plating

[0058] Prepare a 50 mL palladium chloride electroless plating solution with deionized water, with a concentration of PdCl2: 2 g / L; EDTA: 31.5 g / L; NH3·H2O (25% - 28%): 230 mL / L;

[0059] Prepare a hydrazine hydrate solution with deionized water, with a concentration of 0.1 mol / L;

[0060] Take 25 mL of the prepared palladium chloride electroless plating solution, put the ceramic support treated in step (2) into the plating solution, and heat it in a water bath to 60 °C;

[0061] Add 0.2 mL of 0.1 mol / L hydrazine hydrate to the electroless plating solution and stir magnetically;

[0062] Add 0.1 mol / L hydrazine hydrate once every 20 min, 0.2 mL each time. After 5 times, replace the plating solution and repeat the above operation once;

[0063] Take out the sample, rinse it with deionized water for 30 s, and blow dry the surface for later use.

[0064] (4) Electroplate nickel-tungsten on the surface after electroless palladium plating

[0065] Prepare 100 mL of nickel-tungsten plating solution with deionized water, and the concentrations are: NiSO4·6H2O: 13.1 g / L; NaWO4: 49.5 g / L; citric acid monohydrate: 31.5 g / L; NH3·H2O (25 - 28%): 20 mL / L;

[0066] Set the current density to 100 mA / cm 2 , the conduction time and the off time are 2 ms, the water bath temperature is 60 °C, and electroplate for 90 min;

[0067] After electroplating, take out the sample, rinse it with deionized water for 30 s, and dry the surface with cold air for standby;

[0068] The SEM photograph of the electroplated amorphous nickel-tungsten layer is as Figure 2 shown, and its EDS spectrum is as Figure 3 shown, and its XRD spectrum is as Figure 4 shown.

[0069] (5) Surface palladium plating

[0070] Repeat steps (2) and (3) for the sample processed in step (4) to electrolessly plate palladium on the surface. The SEM photograph of the surface morphology after palladium plating is as Figure 5 shown.

[0071] (6) Drying treatment

[0072] Put the sample after palladium plating in step (5) into an oven at 100 °C, take it out after drying for 3 h, and obtain a composite hydrogen permeable membrane with an amorphous nickel-tungsten alloy as the intermediate diffusion layer.

[0073] Example 2:

[0074] A composite hydrogen permeable membrane with an amorphous nickel-tungsten alloy as the intermediate diffusion layer. The composite membrane includes a porous alumina ceramic support, a pure palladium layer A, an amorphous nickel-tungsten layer, and a pure palladium layer B; among them, the porous alumina ceramic support is a tubular porous alumina ceramic with an outer diameter of 12 mm, an inner diameter of 8 mm, a length of 10 mm, a pore diameter of 1.5 μm, and a porosity of 37%; the average thicknesses of the obtained pure palladium layer A and pure palladium layer B are both 1.4 μm, the average thickness of the amorphous nickel-tungsten layer is 13 μm, and the average total thickness of the composite hydrogen permeable membrane is 15.8 μm. The schematic diagram of the tubular composite hydrogen permeable membrane with an amorphous nickel-tungsten alloy as the intermediate diffusion layer is as Figure 6 shown.

[0075] The preparation method of the composite hydrogen permeable membrane with an amorphous nickel-tungsten alloy as the intermediate diffusion layer includes the following steps:

[0076] (1) Surface pretreatment of the porous alumina ceramic support: A tubular porous alumina ceramic support with an outer diameter of 12 mm, an inner diameter of 8 mm, a length of 10 mm, a pore diameter of 1.5 μm, and a porosity of 37% was successively placed in a 15 g / L NaOH solution and deionized water for ultrasonic cleaning for 3 min to remove surface impurities and oil. Subsequently, the surface moisture was dried with cold air, and both ends of the tube were sealed with rubber stoppers for later use;

[0077] (2) Sensitization and activation treatment of the ceramic support

[0078] Prepare a 50 mL sensitizing solution containing 7 g / L SnCl2 and 1 mL / L HCl with deionized water;

[0079] Prepare a 25 mL activating solution containing 0.3 g / L PdCl2 and 2 mL / L HCl with deionized water;

[0080] Put the alumina ceramic support pretreated in step (1) into the sensitizing solution for ultrasonic treatment for 2 min, then take it out and put it into a beaker containing deionized water for ultrasonic cleaning for 30 s, and then put it into the prepared activating solution for ultrasonic treatment for 2 min. After taking it out, put it into a beaker containing deionized water for ultrasonic treatment for 30 s;

[0081] Repeat the above operation 5 times. The surface of the porous alumina ceramic shows a uniform dark brown color, and a uniform palladium nucleus is obtained.

[0082] (3) Electroless plating of palladium on the surface of the activated ceramic support

[0083] Prepare a 50 mL electroless palladium plating solution with deionized water, with a concentration of PdCl2: 3 g / L; EDTA: 40 g / L; NH3·H2O (25% - 28%): 230 mL / L;

[0084] Prepare a hydrazine hydrate solution with deionized water, with a concentration of 0.15 mol / L;

[0085] Take 25 mL of the prepared electroless palladium plating solution, and put the ceramic support treated in step (2) into the plating solution, and heat it in a water bath to 50 °C;

[0086] Add 0.15 mol / L hydrazine hydrate once every 15 min, 0.2 mL each time. After 5 times, replace the plating solution and repeat the above operation once;

[0087] Take out the sample, rinse it with deionized water for 30 s, and dry the surface with cold air for later use.

[0088] (4) Electroplating nickel-tungsten on the surface of the sample after electroless plating of palladium

[0089] Prepare 100 mL of nickel-tungsten plating solution with deionized water, and the concentrations are as follows: NiSO4·6H2O: 18.4 g / L; NaWO4: 33 g / L; citric acid monohydrate: 21 g / L; NH3·H2O (25 - 28%): 20 mL / L;

[0090] Set the current density to 80 mA / cm 2 , the conduction time and the off time are 2 ms, the water bath temperature is 60 °C, and electroplate for 90 min;

[0091] After the electroplating is completed, take out the sample, rinse it with deionized water for 30 s, and dry the surface with cold air.

[0092] (5) Palladium plating on the surface

[0093] Repeat steps (2) and (3) for the sample processed in step (4) to electrolessly plate palladium on the surface.

[0094] (6) Drying treatment

[0095] After rinsing the sample plated with palladium in step (5) with deionized water for 60 s, put it into a drying oven at a temperature of 100 °C, take it out after drying for 3 h, and obtain a composite hydrogen permeable membrane with an amorphous nickel-tungsten alloy as the intermediate diffusion layer.

Claims

1. A palladium-nickel-tungsten-palladium composite hydrogen permeable membrane with an amorphous alloy as the intermediate diffusion layer prepared on the surface of a porous ceramic support, characterized in that The composite hydrogen filtration membrane includes a porous alumina ceramic support, a pure palladium layer A, an amorphous nickel-tungsten layer, and a pure palladium layer B. The porous alumina ceramic support can be a tubular porous alumina ceramic or a sheet-shaped alumina ceramic, with a pore diameter of 30 nm to 2 μm and a porosity of 20% to 40%. The thickness of the pure palladium layer A and the pure palladium layer B is 0.5 to 5 μm, the thickness of the amorphous nickel-tungsten layer is 1 to 15 μm, and the total thickness of the alloy hydrogen filtration membrane is 2 to 30 μm.

2. A method for preparing a composite hydrogen filtration membrane with an amorphous nickel-tungsten alloy as the intermediate diffusion layer, characterized in that The method includes the following steps: (1) Surface pretreatment of the porous alumina ceramic support The porous alumina ceramic support is successively placed in a NaOH solution with a concentration of 5 to 20 g / L and deionized water, and ultrasonically cleaned for 2 to 10 minutes to remove oil and dust on the surface of the ceramic support. (2) Sensitization and activation treatment of the ceramic support ① The pretreated ceramic support is immersed in a SnCl2 / HCl sensitization solution and ultrasonically treated for 0.5 to 10 minutes for sensitization, and then ultrasonically cleaned in deionized water for 10 to 60 seconds. The concentration of the sensitization solution is: SnCl2: 3 to 10 g / L; HCl: 1 mL / L; ② The sensitized ceramic support is placed in a PdCl2 / HCl activation solution and ultrasonically treated for 0.5 to 10 minutes for activation, and then ultrasonically cleaned in deionized water for 10 to 60 seconds. The concentration of the activation solution is: PdCl2: 0.1 to 0.5 g / L; HCl: 2 mL / L; Repeat the above steps 3 to 10 times to evenly deposit palladium nuclei on the surface of the ceramic support. At this time, the surface of the ceramic support shows a uniformly distributed dark brown color. (3) Plating palladium on the surface of the activated ceramic support by electroless plating The ceramic support treated in step (2) is placed in the prepared palladium chloride electroless plating solution, placed in a water bath at a temperature of 40 to 70 °C, and magnetically stirred. A hydrazine hydrate solution is added in portions every 5 to 30 minutes. After adding hydrazine hydrate 3 to 6 times, the electroless plating solution is replaced. Repeat the above operation 2 to 10 times. After taking out the sample, it is rinsed with deionized water for 30 to 90 seconds and dried with cold air for standby. The concentration requirements of the palladium electroless plating solution are: PdCl2: 1 to 4 g / L; EDTA: 25 to 50 g / L; NH3·H2O (25% to 28%): 200 to 250 mL / L; hydrazine hydrate: 0.05 to 0.3 mol / L; (4) Electroplating nickel-tungsten on the surface after electroless plating of palladium The sample plated with palladium in step (3) is placed in a nickel-tungsten plating solution, placed in a water bath at a temperature of 30 to 70 °C, using a pure nickel plate as the anode, setting the on-off time and current, electroplating for 5 to 120 minutes, taking out the sample, rinsing with deionized water for 30 to 90 seconds, and drying with cold air for standby. The concentration requirements of the nickel-tungsten electroplating solution are: NiSO4·6H2O: 10 to 25 g / L; Na2WO4: 30 to 60 g / L; citric acid monohydrate: 15 to 80 g / L; NH3·H2O (25 to 28%): 2 to 50 mL / L; The current parameters requirements are: Current density: 50 - 120 mA / cm 2 ; Select a forward pulse current, and the conduction time is equal to the off time: 1 to 5 ms; (5) Plating palladium on the surface Repeat steps (2) and (3) for the sample processed in step (4) to electrolessly plate palladium on the surface; (6) Drying treatment Put the sample plated with palladium in step (5) into a drying oven at a temperature of 100 °C and dry for 2 - 4 h to obtain a composite hydrogen permeable membrane with an amorphous nickel-tungsten alloy as the intermediate diffusion layer.

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