A method for preparing Ni-Fe-Mo alloy metal nanoparticles by using a molten salt washing method

Abstract

The application belongs to the technical field of electrocatalytic materials, and discloses a method for preparing Ni-Fe-Mo alloy metal nanoparticles by adopting a molten salt washing method, which comprises the following steps: step 1, impregnation: a precursor solution obtained by mixing nickel salt, iron salt and molybdenum salt is mixed with a carbon carrier in a certain proportion; step 2, hydrothermal treatment: the mixture obtained in the previous step is subjected to hydrothermal treatment; step 3, drying: vacuum drying is performed; step 4, reduction: the dried product is reduced by a tubular furnace in a hydrogen-argon mixed gas reducing atmosphere; step 5, salt bath decarburization: the obtained sample is subjected to decarburization in a low-temperature ternary molten salt under a reducing atmosphere; step 6, water washing and salt removal: the mixture obtained by decarburization in the previous step is subjected to water washing, and the product after salt removal is filtered; and step 7, centrifugal separation: the product after salt removal is subjected to water washing again, and the obtained liquid is subjected to centrifugal treatment to realize decarburization. The application avoids the problems of corrosion and dissolution of the carbon carrier and the problem of agglomeration of metal nanoparticles in the reduction process.

Description

Technical Field

[0001] The invention belongs to the technical field of electrocatalytic materials, and particularly relates to a method for preparing Ni-Fe-Mo alloy metal nanoparticles by adopting a molten salt washing method. Background Art

[0002] Precious metal catalysts are expensive and their raw materials are scarce. Precious metal nanoparticles with uniform particle size and morphology are relatively easy to prepare, but their high cost and commercialization are limited by the availability of raw materials. Therefore, researchers have begun to explore transition metal-based catalysts, which are abundant on Earth, as alternatives to precious metal catalysts for efficient oxygen evolution reactions. Ni-Fe-Mo alloy metal nanoparticles are an effective catalytic alternative to precious metal catalysts for water electrolysis. The electrocatalytic activity of metal nanoparticles is related to the structure and morphology of the material. Non-precious metal nanoparticles have strong reducing properties and are easily oxidized. Furthermore, nanoparticles tend to agglomerate and fuse during drying and heat treatment, resulting in coarsening of the particles. Materials with smaller, thinner particles and richer pore structures exhibit better catalytic activity. Therefore, porous carbon supports are commonly used to support these alloy metal nanoparticles. However, this also makes the resulting catalytic material susceptible to corrosion, shedding, and other adverse factors, leading to deactivation. Metal catalysts prepared on carbon supports are prone to carbon corrosion when used as anode catalysts in water electrolysis, causing particles to detach from the support, resulting in reduced electrode performance. Therefore, how to solve the problem that non-precious metal nanoparticles with uniform particle size and consistent morphology are prone to oxidation, agglomeration, melting, and particle coarsening during the preparation process has become a technical problem that needs to be solved in the existing technology. Summary of the Invention

[0003] The purpose of the present invention is to provide a method for preparing Ni-Fe-Mo alloy metal nanoparticles using a molten salt washing method, so as to solve the technical problems in the prior art that Ni-Fe-Mo alloy metal nanoparticles based on porous carbon supports are prone to carbon corrosion and large-scale preparation of non-precious metal nanoparticles.

[0004] A method for preparing Ni-Fe-Mo alloy metal nanoparticles by using a molten salt washing method comprises the following steps.

[0005] Step 1. Impregnation: The precursor solution is mixed evenly with the carbon support in a certain proportion, wherein the precursor solution is a mixed solution of nickel salt, iron salt and molybdenum salt, and the mass ratio of nickel element, iron element and molybdenum element in the precursor solution is in the range of 1:1:2 to 5:1:2. The mass of the carbon support is added in proportion to the total loading mass fraction of the three metal elements of nickel, iron and molybdenum, and the loading mass fraction ratio range is 2% to 10%.

[0006] Step 2. Hydrothermal treatment: The mixture obtained in the previous step is subjected to hydrothermal treatment at a temperature ranging from 130° C. to 190° C. for 12 hours.

[0007] Step 3. Drying: The hydrothermal mixture was dried in vacuum at 100°C.

[0008] Step 4. Reduction: The dried product is reduced in a reducing atmosphere of a hydrogen-argon mixture in a tubular furnace at a reduction temperature of 500° C. to 700° C. for 2 hours.

[0009] Step 5. Salt bath decarburization: Under the reducing atmosphere of step 4, select low-temperature ternary molten salt to decarburize the sample obtained in step 4, and the decarburization temperature of the low-temperature ternary molten salt is controlled at 50°C to 120°C.

[0010] Step 6. Water washing and desalting: The mixture obtained from the decarbonization treatment in the previous step is washed with water, and the liquid obtained by washing is filtered to obtain the desalted product.

[0011] Step 7. Centrifugal separation: The desalted product is washed again with water, the obtained liquid is centrifuged, and the precipitate is dried to obtain Ni-Fe-Mo alloy metal nanoparticles.

[0012] Preferably, in step 5, high-power ultrasound is used for auxiliary treatment during the decarburization process.

[0013] Preferably, the low-temperature ternary molten salt is composed of 7% by mass of NaNO3, 53% by mass of KNO3 and 40% by mass of NaNO2.

[0014] Preferably, in step 1, the nickel salt used in the precursor solution is any one of nickel nitrate, nickel chloride and nickel sulfate, or a mixture of two or more thereof.

[0015] Preferably, in step 1, the iron salt used in the precursor solution is any one of ferric nitrate, ferric chloride and ferric sulfate, or a mixture of two or more thereof.

[0016] Preferably, in step 1, the molybdenum salt used in the precursor solution is any one of sodium molybdate, ammonium molybdate and potassium molybdate, or a mixture of two or more thereof.

[0017] Preferably, in step 1, a certain amount of methanol needs to be added dropwise to the carbon support during mixing to increase the wettability of the carbon support.

[0018] Preferably, the carbon carrier is an ordered mesoporous carbon with a pore size of 3nm to 6nm and a specific surface area of ​​600m 2 / g.

[0019] Preferably, in step 4, hydrogen accounts for 10 vol% in the hydrogen-argon mixed gas, and the heating rate is 10° C. / min.

[0020] Preferably, the particle size of the Ni-Fe-Mo alloy metal nanoparticles prepared by the method is concentrated in the range of 3nm to 4nm.

[0021] The present invention has the following advantages.

[0022] 1. When metal nanoparticles are used as electrocatalysts, they require high electrical conductivity. Furthermore, carbon supports are susceptible to oxidation and corrosion in the highly oxidizing environment of the anode. Consequently, existing technologies are prone to problems such as catalyst oxidation, dissolution, and detachment, such as the carbon dissolution problem at the anode of commercial Pt-C electrodes. However, this method eliminates these corrosion and dissolution issues by removing the carbon support during the preparation process.

[0023] 2. In the preparation process, this method first uses a carbon carrier to load the metal nanoparticles. At this time, the porous carbon carrier can effectively avoid the problem of metal nanoparticle agglomeration during the reduction process.

[0024] 3. This method has a simple synthesis process and uses very little organic matter, thus causing less environmental pollution. Furthermore, the decarbonization and water washing process can recover the carbon support and molten salt, which can be reused, thus reducing production costs.

[0025] 4. This scheme can also simply control the alloy composition by the precursor ratio and the alloy particle size by the loading amount and carrier porosity.

[0026] In summary, the present invention can not only ensure the stability, lifespan and catalytic efficiency of the metal alloy nanoparticle catalyst, but also control the preparation cost and controllability of the catalyst, thus solving the problems of the catalyst being easily oxidized, dissolved and detached in the prior art. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 The present invention is a schematic flow chart of a method for preparing Ni-Fe-Mo alloy metal nanoparticles by a molten salt washing method.

[0028] Figure 2 This is a schematic diagram of the principle of the present invention, in which the circular pattern represents Ni-Fe-Mo alloy metal nanoparticles, and the cross pattern represents the carbon support. DETAILED DESCRIPTION

[0029] The specific implementation methods of the present invention will be further explained in detail below through the description of embodiments with reference to the accompanying drawings, so as to help those skilled in the art to have a more complete, accurate and in-depth understanding of the inventive concept and technical solution of the present invention.

[0030] Example 1:

[0031] like Figure 1 、 Figure 2 As shown, the present invention provides a method for preparing Ni-Fe-Mo alloy metal nanoparticles by using a molten salt washing method, which includes the following steps.

[0032] Step 1. Impregnation: A precursor solution of nickel nitrate, ferric nitrate, and sodium molybdate is uniformly mixed with the carbon support in a predetermined ratio. The precursor solution contains nickel nitrate, iron nitrate, and molybdenum in a 1:1:2 mass ratio. The carbon support is added at a metal element loading of 10% (based on the catalyst support mass). To increase the wettability of the carbon support, a certain amount of methanol is added dropwise during mixing.

[0033] Step 2. Hydrothermal treatment: The mixture obtained in the previous step was subjected to hydrothermal treatment at a temperature of 130° C. for 12 hours.

[0034] Step 3. Drying: The hydrothermal mixture is vacuum dried at 100° C. The obtained dried product can be ground to uniform particle size.

[0035] Step 4. Reduction: The dried product was reduced in a tubular furnace with a reducing atmosphere of 10 vol% H2-Ar mixed gas (i.e., a mixture of Ar and H2, in which H2 accounts for 10 vol%), a heating rate of 10°C / min, a reduction temperature of 500°C, and a duration of 2 hours.

[0036] Step 5. Salt bath decarburization: Under the reducing atmosphere of step 4, a low-temperature ternary molten salt is selected to decarburize the sample obtained in step 4. The decarburization temperature of the low-temperature ternary molten salt is controlled at 50°C, and high-power ultrasonic waves are used for auxiliary treatment during the decarburization process to increase the decarburization efficiency. The low-temperature ternary molten salt used in the embodiment is commercial Hitec molten salt, which has a composition of 7% by mass of NaNO3, 53% by mass of KNO3, and 40% by mass of NaNO2. In application, optimization can also be performed based on the component ratio of the commercial Hitec molten salt.

[0037] Step 6. Water washing and desalting: The mixture obtained from the decarbonization treatment in the previous step is washed with water, and the liquid obtained by washing is filtered to obtain the desalted product.

[0038] Step 7. Centrifugal Separation: The desalted product is washed again with water, and the resulting liquid is centrifuged to decarbonize. The decarbonized liquid is then dried to obtain Ni-Fe-Mo alloy metal nanoparticles. The Ni-Fe-Mo alloy metal nanoparticles obtained by this method have a particle size range of 3 to 4 nm.

[0039] Example 2:

[0040] like Figure 1 、 Figure 2 As shown, the present invention provides a method for preparing Ni-Fe-Mo alloy metal nanoparticles by using a molten salt washing method, which includes the following steps.

[0041] Step 1. Impregnation: A precursor solution of nickel nitrate, ferric nitrate, and sodium molybdate is uniformly mixed with the carbon support in a predetermined ratio. The precursor solution contains nickel nitrate, iron nitrate, and molybdenum in a 2:1:2 mass ratio. The carbon support is added to achieve an 8% metal element loading. To improve wettability, methanol is added dropwise to the carbon support during mixing.

[0042] Step 2. Hydrothermal treatment: The mixture obtained in the previous step was subjected to hydrothermal treatment at a temperature of 140° C. for 12 hours.

[0043] Step 3. Drying: The hydrothermal mixture is vacuum dried at 100° C. The obtained dried product can be ground to uniform particle size.

[0044] Step 4. Reduction: The dried product was reduced in a tubular furnace with a reducing atmosphere of 10 vol% H2-Ar mixed gas, a heating rate of 10°C / min, a reduction temperature of 580°C, and a duration of 2 hours.

[0045] Step 5. Salt bath decarburization: Under the reducing atmosphere of step 4, a low-temperature ternary molten salt is selected to decarburize the sample obtained in step 4. The decarburization temperature of the low-temperature ternary molten salt is controlled at 70°C, and high-power ultrasonic waves are used for auxiliary treatment during the decarburization process to increase the decarburization efficiency. The low-temperature ternary molten salt used in the embodiment is commercial Hitec molten salt, which has a composition of 7% by mass of NaNO3, 53% by mass of KNO3, and 40% by mass of NaNO2. In application, optimization can also be performed based on the component ratio of the commercial Hitec molten salt.

[0046] Step 6. Water washing and desalting: The mixture obtained from the decarbonization treatment in the previous step is washed with water, and the liquid obtained by washing is filtered to obtain the desalted product.

[0047] Step 7. Centrifugal Separation: The desalted product is washed again with water, and the resulting liquid is centrifuged to decarbonize. The decarbonized liquid is then dried to obtain Ni-Fe-Mo alloy metal nanoparticles. The Ni-Fe-Mo alloy metal nanoparticles obtained by this method have a particle size range of 3 to 4 nm.

[0048] Example 3:

[0049] like Figure 1 、 Figure 2 As shown, the present invention provides a method for preparing Ni-Fe-Mo alloy metal nanoparticles by using a molten salt washing method, which includes the following steps.

[0050] Step 1. Impregnation: A precursor solution of nickel nitrate, ferric nitrate, and sodium molybdate is uniformly mixed with the carbon support. The precursor solution contains nickel nitrate, iron nitrate, and molybdenum in a mass ratio of 3:1:2. The carbon support is added to achieve a metal element loading of 6%. To improve wettability, a certain amount of methanol is added dropwise to the carbon support during mixing.

[0051] Step 2. Hydrothermal treatment: The mixture obtained in the previous step was subjected to hydrothermal treatment at a temperature of 160° C. for 12 hours.

[0052] Step 3. Drying: The hydrothermal mixture is vacuum dried at 100° C. The obtained dried product can be ground to uniform particle size.

[0053] Step 4. Reduction: The dried product was reduced in a tubular furnace with a reducing atmosphere of 10 vol% H2-Ar mixed gas, a heating rate of 10°C / min, a reduction temperature of 620°C, and a duration of 2 hours.

[0054] Step 5. Salt bath decarburization: Under the reducing atmosphere of step 4, a low-temperature ternary molten salt is selected to decarburize the sample obtained in step 4. The decarburization temperature of the low-temperature ternary molten salt is controlled at 90°C, and high-power ultrasonic waves are used for auxiliary treatment during the decarburization process to increase the decarburization efficiency. The low-temperature ternary molten salt used in the embodiment is commercial Hitec molten salt, which has a composition of 7% by mass of NaNO3, 53% by mass of KNO3, and 40% by mass of NaNO2. In application, optimization can also be performed based on the component ratio of the commercial Hitec molten salt.

[0055] Step 6. Water washing and desalting: The mixture obtained from the decarbonization treatment in the previous step is washed with water, and the liquid obtained by washing is filtered to obtain the desalted product.

[0056] Step 7. Centrifugal Separation: The desalted product is washed again with water, and the resulting liquid is centrifuged to decarbonize. The decarbonized liquid is then dried to obtain Ni-Fe-Mo alloy metal nanoparticles. The Ni-Fe-Mo alloy metal nanoparticles obtained by this method have a particle size range of 3 to 4 nm.

[0057] Example 4:

[0058] like Figure 1 、 Figure 2 As shown, the present invention provides a method for preparing Ni-Fe-Mo alloy metal nanoparticles by using a molten salt washing method, which includes the following steps.

[0059] Step 1. Impregnation: A precursor solution of nickel nitrate, ferric nitrate, and sodium molybdate is uniformly mixed with the carbon support. The precursor solution contains nickel nitrate, iron nitrate, and molybdenum in a 5:1:2 mass ratio. The carbon support is added to achieve a 2% metal element loading. To improve wettability, methanol is added dropwise to the carbon support during mixing.

[0060] Step 2. Hydrothermal treatment: The mixture obtained in the previous step was subjected to hydrothermal treatment at a temperature of 190° C. for 12 hours.

[0061] Step 3. Drying: The hydrothermal mixture is vacuum dried at 100° C. The obtained dried product can be ground to uniform particle size.

[0062] Step 4. Reduction: The dried product was reduced in a tubular furnace with a reducing atmosphere of 10 vol% H2-Ar mixed gas, a heating rate of 10°C / min, a reduction temperature of 700°C, and a duration of 2 hours.

[0063] Step 5. Salt bath decarburization: Under the reducing atmosphere of step 4, a low-temperature ternary molten salt is selected to decarburize the sample obtained in step 4. The decarburization temperature of the low-temperature ternary molten salt is controlled at 120°C, and high-power ultrasonic waves are used for auxiliary treatment during the decarburization process to increase the decarburization efficiency. The low-temperature ternary molten salt used in the embodiment is commercial Hitec molten salt, which has a composition of 7% by mass of NaNO3, 53% by mass of KNO3, and 40% by mass of NaNO2. In application, optimization can also be performed based on the component ratio of the commercial Hitec molten salt.

[0064] Step 6. Water washing and desalting: The mixture obtained from the decarbonization treatment in the previous step is washed with water, and the liquid obtained by washing is filtered to obtain the desalted product.

[0065] Step 7. Centrifugal Separation: The desalted product is washed again with water, and the resulting liquid is centrifuged to decarbonize. The decarbonized liquid is then dried to obtain Ni-Fe-Mo alloy metal nanoparticles. The Ni-Fe-Mo alloy metal nanoparticles obtained by this method have a particle size range of 3 nm to 4 nm.

[0066] The carbon support used in the above examples is commercial ordered mesoporous carbon with a pore size of 3 nm to 6 nm and a specific surface area of ​​600 m 2 / g. In addition to nickel nitrate, nickel salts used in the precursor solution may also include nickel chloride, nickel sulfate, and other nickel salts. In addition to iron nitrate, iron salts may also include iron chloride, iron sulfate, and other iron salts. In addition to sodium molybdate, molybdenum salts may also include ammonium molybdate, potassium molybdate, and other molybdenum salts.

[0067] The present invention is described above by way of example in conjunction with the accompanying drawings. It is obvious that the specific implementation of the present invention is not limited to the above-mentioned method. As long as various non-substantial improvements are made using the inventive concept and technical solution of the present invention, or the inventive concept and technical solution are directly applied to other occasions without improvement, they are all within the scope of protection of the present invention.

Claims

1. A method for preparing Ni-Fe-Mo alloy metal nanoparticles using a molten salt washing method, characterized in that: The following steps are involved: Step 1. Impregnation: A precursor solution is mixed uniformly with a carbon support in a certain proportion, wherein the precursor solution is a mixed solution of nickel salt, iron salt and molybdenum salt, and the mass ratio of nickel element, iron element and molybdenum element in the precursor solution ranges from 1:1:2 to 5:1:

2. The mass of the carbon support is added in proportion to the total loading mass fraction of the three metal elements of nickel, iron and molybdenum, and the loading mass fraction ratio ranges from 2% to 10%; Step 2. Hydrothermal treatment: The mixture obtained in the previous step is hydrothermally treated at a temperature ranging from 130°C to 190°C for 12 hours. Step 3. Drying: The hydrothermal mixture is vacuum dried at 100°C; Step 4. Reduction: The dried product is reduced in a reducing atmosphere of hydrogen and argon mixed gas in a tube furnace at a temperature of 500°C to 700°C for 2 hours; Step 5. Salt bath decarburization: Under the reducing atmosphere of step 4, select low-temperature ternary molten salt to decarburize the sample obtained in step 4, and the decarburization temperature of the low-temperature ternary molten salt is controlled at 50°C to 120°C; Step 6. Water washing and desalting: The mixture obtained from the decarbonization treatment in the previous step is washed with water, and the liquid obtained by washing is filtered to obtain the desalted product; Step 7. Centrifugal separation: The desalted product is washed again with water, the obtained liquid is centrifuged, and the precipitate is dried to obtain Ni-Fe-Mo alloy metal nanoparticles.

2. The method for preparing Ni-Fe-Mo alloy metal nanoparticles by a molten salt washing method according to claim 1, characterized in that: In step 5, high-power ultrasonic waves are used for auxiliary treatment during the decarburization process.

3. The method for preparing Ni-Fe-Mo alloy metal nanoparticles by molten salt washing according to claim 1, characterized in that: The composition of the low-temperature ternary molten salt is 7% by mass of NaNO3, 53% by mass of KNO3 and 40% by mass of NaNO2.

4. The method for preparing Ni-Fe-Mo alloy metal nanoparticles by a molten salt washing method according to claim 1, characterized in that: In step 1, the nickel salt used in the precursor solution is any one of nickel nitrate, nickel chloride and nickel sulfate, or a mixture of two or more thereof.

5. The method for preparing Ni-Fe-Mo alloy metal nanoparticles by molten salt washing according to claim 1, characterized in that: In the step 1, the iron salt used in the precursor solution is any one of ferric nitrate, ferric chloride and ferric sulfate, or a mixture of two or more thereof.

6. The method for preparing Ni-Fe-Mo alloy metal nanoparticles by molten salt washing according to claim 1, characterized in that: In step 1, the molybdenum salt used in the precursor solution is any one of sodium molybdate, ammonium molybdate and potassium molybdate, or a mixture of two or more thereof.

7. The method for preparing Ni-Fe-Mo alloy metal nanoparticles by molten salt washing according to claim 1, characterized in that: In step 1, a certain amount of methanol needs to be added dropwise to the carbon support during mixing to increase the wettability of the carbon support.

8. The method for preparing Ni-Fe-Mo alloy metal nanoparticles by molten salt washing according to claim 1, characterized in that: The carbon carrier is an ordered mesoporous carbon with a pore size of 3nm to 6nm and a specific surface area of ​​600m 2 / g.

9. The method for preparing Ni-Fe-Mo alloy metal nanoparticles by molten salt washing according to claim 1, characterized in that: In step 4, hydrogen accounts for 10 vol% of the hydrogen-argon mixed gas, and the heating rate is 10° C. / min.

10. The method for preparing Ni-Fe-Mo alloy metal nanoparticles by molten salt washing according to claim 1, characterized in that: The particle sizes of the Ni-Fe-Mo alloy metal nanoparticles prepared by the method are concentrated in the range of 3nm to 4nm.

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