Hydrogen evolution electrode catalyst, preparation method thereof and method for preparing hydrogen

Abstract

The invention relates to the technical field of water electrolysis hydrogen production, and discloses a hydrogen evolution electrode catalyst, a preparation method thereof and a hydrogen preparation method. The hydrogen evolution electrode catalyst provided by the invention has a unique dendritic structure and shows excellent hydrogen evolution capability. According to the catalyst, Ni and Ag are adopted as main raw materials, the cost of the catalyst for hydrogen production through water electrolysis is greatly reduced, and the catalyst has the potential of large-scale application due to the fact that the preparation method of the catalyst is simple, the raw materials are easy to obtain, and the requirement for equipment is low.

Description

Technical Field

[0001] The invention relates to the technical field of hydrogen production by electrolysis of water, and in particular to a hydrogen evolution electrode catalyst and a preparation method thereof and a method for preparing hydrogen. Background Art

[0002] Hydrogen energy has the advantages of high energy density, green and pollution-free, diverse sources, abundant reserves, and wide application, and can be combined with wind energy, electricity, solar energy and other energy sources. Therefore, hydrogen energy stands out among many energy sources and has become the focus of attention on the world energy stage in the 21st century. At present, hydrogen production technology is still dominated by fossil energy production, but it has inherent carbon emission problems. In the context of "dual carbon goals" and energy transformation, the development of clean water electrolysis hydrogen production technology will become the key to achieving "carbon neutrality".

[0003] Limited by the kinetics of the hydrogen evolution reaction (HER), precious metal catalysts are currently recognized as the most effective catalysts for water electrolysis. However, the high cost and low reserves of precious metals make it difficult to support large-scale production and application. Therefore, finding low-cost and high-performance hydrogen evolution catalysts is one of the key factors in promoting the promotion of hydrogen energy. Summary of the invention

[0004] The purpose of the present invention is to overcome the problems of the prior art that the noble metal catalysts for hydrogen production by electrolysis of water are high in cost and scarce in source, thus making it difficult to apply them on a large scale, and to provide a hydrogen evolution electrode catalyst and a preparation method thereof and a method for preparing hydrogen. The hydrogen evolution electrode catalyst provided by the present invention uses Ni and Ag as main raw materials, which greatly reduces the cost compared with the existing noble metal catalysts. At the same time, the catalyst also has excellent electrocatalytic hydrogen evolution performance and is suitable for industrial-scale production and application.

[0005] In order to achieve the above object, the present invention provides a hydrogen evolution electrode catalyst on one hand, wherein the catalyst comprises a carrier and Ag loaded on the carrier, and the carrier comprises NiO.

[0006] A second aspect of the present invention provides a method for preparing a hydrogen evolution electrode catalyst, the method comprising: contacting a carrier raw material made of Ni single substance with a reaction solution containing an oxidant and a silver salt, so that Ag is loaded on the carrier during the formation of NiO.

[0007] The third aspect of the present invention provides a hydrogen evolution electrode catalyst prepared by the method described in the second aspect.

[0008] A fourth aspect of the present invention provides a method for preparing hydrogen, the method comprising contacting the hydrogen evolution electrode catalyst described in the first aspect or the third aspect with an electrolyte, and reacting under electrolysis conditions.

[0009] Through the above technical solution, the present invention can at least achieve the following beneficial effects:

[0010] (1) The hydrogen evolution electrode catalyst provided by the present invention has a special dendritic structure and exhibits excellent hydrogen evolution performance. Experiments have shown that when the Ag loading on NiO / Ni is 0.45 wt%, the catalyst has a high conductivity at 10 mA cm -2 The HER overpotential at this current density is only 216 mV.

[0011] (2) The hydrogen evolution electrode catalyst provided by the present invention uses Ag to replace precious metals such as Pt in traditional hydrogen evolution catalysts, which greatly reduces the cost. In addition, since the reserves of Ag are much higher than other precious metals, it is possible to use the catalyst for industrial-scale hydrogen production.

[0012] (2) The preparation method of the hydrogen evolution electrode catalyst provided by the present invention is simple, has mild conditions, readily available raw materials, has low requirements on equipment, and is suitable for large-scale production. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 This is a SEM image of the hydrogen evolution electrode catalyst A1 obtained in Example 1.

[0014] Figure 2 1 is the LSV curve of the hydrogen evolution electrode catalyst A1 obtained in Example 1.

[0015] Figure 3 is a SEM image of the hydrogen evolution electrode catalyst A8 obtained in Example 8. DETAILED DESCRIPTION

[0016] The endpoints and any values ​​of the ranges disclosed in this article are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of each range, the endpoint values ​​of each range and the individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed in this article.

[0017] The inventor of the present invention accidentally discovered during research that by loading Ag on a material containing NiO, a composite material with good ability to produce hydrogen by electrolysis of water can be obtained. The material uses relatively cheap Ag to replace precious metals such as Pt in traditional hydrogen evolution catalysts, effectively reducing the cost of producing hydrogen by electrolysis of water and providing the possibility of industrial-scale hydrogen production.

[0018] Based on the above findings, the present invention provides a hydrogen evolution electrode catalyst in a first aspect. The catalyst comprises a carrier and Ag loaded on the carrier, and the carrier comprises NiO.

[0019] According to a preferred embodiment of the present invention, the carrier further comprises Ni.

[0020] According to some preferred embodiments of the present invention, the carrier is a composite material composed of Ni and NiO (referred to as "Ni / NiO composite material", "Ni / NiO material" or "Ni / NiO" in the present invention).

[0021] Preferably, in the carrier, the weight ratio of Ni to NiO is 20-70:1, preferably 25-50:1.

[0022] The inventors of the present invention have also found in their research that when the Ni / NiO composite material used as a carrier has a certain thickness, the prepared hydrogen evolution electrode catalyst has a better hydrogen evolution ability.

[0023] According to some preferred embodiments of the present invention, the thickness of the carrier is 0.5-2 mm, preferably 0.5-1 mm.

[0024] In order to further improve the hydrogen evolution performance of the hydrogen evolution electrode catalyst, a carrier with a certain pore structure may be selected. According to some preferred embodiments of the present invention, the pore size of the carrier is 0.01-0.6 mm, and the porosity is 70-90%.

[0025] Preferably, the average pore size of the carrier is 0.1-0.5 mm.

[0026] In the present invention, there is no particular limitation on the loading amount of Ag in the hydrogen evolution electrode catalyst, as long as it can achieve a satisfactory hydrogen evolution effect.

[0027] According to some preferred embodiments of the present invention, in the catalyst, the loading amount of Ag is 0.1-1.5 wt %, preferably 0.13-1.25 wt %, based on the total weight of the catalyst.

[0028] Preferably, the catalyst has a dendritic structure. The dendritic structure refers to a catalyst having a "trunk" and "side branches" formed on the sides of the "trunk" (for details, please refer to Figure 1 As can be seen from the figure, the side branches are arranged symmetrically and orderly, growing closely on both sides of the main trunk, and the dendrite size is uniform), which can usually be observed by scanning electron microscopy. Preferably, in the "dendritic structure" of the catalyst provided by the present invention, the main trunk is 5-15μm long and 0.5-3μm in diameter, and the side branches (in rod-like morphology) are 1-5μm long and 0.3-2.5μm in diameter.

[0029] Preferably, calculated on an element basis, in the catalyst, the weight ratio of Ag to Ni provided by NiO is 1:3-17, preferably 1:5-12.

[0030] The present invention has no particular restrictions on the specific preparation method of the above-mentioned hydrogen evolution electrode catalyst provided, and the catalyst can be prepared by the existing method for preparing a supported catalyst. However, the inventors of the present invention cleverly discovered during the research process that, compared with the conventional method of loading silver on Ni / NiO materials by impregnation, the hydrogen evolution electrode catalyst prepared by introducing silver during the oxidation of the nickel elemental material (for example, the nickel can be brought into contact with a silver-containing compound during oxidation) has a tighter combination of Ag and the carrier, thereby having a longer stable service life.

[0031] Based on the above findings, the second aspect of the present invention provides a method for preparing a hydrogen evolution electrode catalyst, the method comprising: contacting a carrier raw material made of Ni single substance with a reaction solution containing an oxidant and a silver source, so that Ag is loaded on the carrier during the formation of NiO.

[0032] In the present invention, there is no particular restriction on the specific form (such as shape, size, etc.) of the carrier raw material, as long as the material is nickel. For example, common Ni materials in the form of flakes or plates, blocks or particles, wires, nets, powders, etc. can be used as the carrier raw material, and special metal materials made of Ni such as nickel foam can also be used.

[0033] According to some preferred embodiments of the present invention, the carrier raw material is selected from nickel foam.

[0034] Preferably, the thickness of the nickel foam is 0.5-2 mm, preferably 0.5-1 mm.

[0035] Preferably, the pore size of the nickel foam is 0.01-0.6 mm, and the porosity is 70-90%.

[0036] Preferably, the average pore size of the nickel foam is 0.1-0.5 mm.

[0037] In the present invention, the oxidant refers to a compound that can be used to oxidize Ni in the carrier raw material to form NiO. According to some preferred embodiments of the present invention, the oxidant is at least one selected from persulfuric acid, persulfate and hydrogen peroxide.

[0038] Preferably, the oxidant is selected from at least one of persulfate or persulfate, preferably at least one of ammonium persulfate, sodium persulfate and potassium persulfate.

[0039] In the present invention, the silver source refers to a compound that provides Ag for loading thereon during the Ni oxidation process. The present invention has no particular limitation on the specific amount of the silver source, as long as a catalyst with a satisfactory hydrogen evolution effect can be obtained. According to some preferred embodiments of the present invention, the content of the silver salt in the reaction solution is such that the Ag loading in the prepared catalyst is 0.1-1.5 wt %, preferably 0.13-1.25 wt %, based on the total weight of the catalyst.

[0040] Preferably, in the reaction solution, the weight ratio of the silver source to the oxidant is 1:10-50.

[0041] Preferably, the silver source is selected from water-soluble compounds of Ag, preferably silver nitrate.

[0042] According to a preferred embodiment of the present invention, the contacting method includes placing the carrier raw material in the reaction solution and leaving it to stand for 10-30 hours. In order to make the Ag distribution on the prepared catalyst more uniform, it is preferred that the carrier raw material is completely immersed in the reaction solution.

[0043] According to a preferred embodiment of the present invention, the method further comprises a step of first cleaning the carrier material before contacting with the reaction solution. The purpose of the first cleaning is to remove grease, dust and other attachments on the surface of the carrier material.

[0044] Any cleaning method that can achieve the above purpose can be applied to the present invention. Preferably, the first cleaning method comprises washing the carrier raw material with an organic solvent and an inorganic acid in sequence.

[0045] Preferably, the organic solvent is selected from at least one of organic solvents having a carbon atom number not exceeding 5 (eg, ethanol, acetone, etc.).

[0046] Preferably, the inorganic acid is selected from an aqueous solution of at least one of sulfuric acid, hydrochloric acid and nitric acid, preferably wherein H + The concentration does not exceed 3M, preferably 0.5-2M.

[0047] Preferably, the first cleaning is performed by ultrasonic cleaning, preferably in an organic solvent and an inorganic acid, respectively, for 5-60 minutes, preferably 10-40 minutes.

[0048] According to a preferred embodiment of the present invention, the method further comprises the step of second washing and drying the reacted carrier raw material after contact (completion). The purpose of the second washing is to remove the reaction liquid on the surface of the material, preferably by washing with water or an organic solvent.

[0049] Preferably, the drying conditions include: temperature 20-60° C., and drying time 4-12 h.

[0050] The third aspect of the present invention provides a hydrogen evolution electrode catalyst prepared by the method described in the second aspect. The characteristics of the catalyst are as described above and will not be repeated here.

[0051] A fourth aspect of the present invention provides a method for preparing hydrogen, the method comprising contacting the hydrogen evolution electrode catalyst described in the first aspect or the third aspect with an electrolyte, and reacting under electrolysis conditions.

[0052] The present invention will be described in detail below by way of examples. It should be understood that the following examples are only used to further explain and illustrate the content of the present invention by way of example, and are not intended to limit the present invention.

[0053] In the following examples, unless otherwise specified, all reagents used were commercial products purchased from regular chemical suppliers and were of analytical grade.

[0054] In the following embodiments, unless otherwise specified, the thickness of the nickel foam used is 0.5 mm, the pore size is 0.01-0.6 mm (the average pore size is about 0.4 mm), and the porosity is about 80%.

[0055] In the following examples, unless otherwise specified, the operating temperature is room temperature (25±5°C).

[0056] Example 1

[0057] The hydrogen evolution electrode catalyst was prepared by the following method:

[0058] (1) Take a 2 cm × 2 cm nickel foam, immerse it in ethanol for ultrasonic cleaning for 30 min, then take it out and immerse it in 1 M sulfuric acid solution for ultrasonic cleaning for 10 min to obtain a clean nickel foam;

[0059] (2) 30 mL of ammonium persulfate solution (containing 0.44 g of ammonium persulfate) was prepared and 0.018 g of silver nitrate was added thereto, dissolved and mixed to obtain a reaction solution.

[0060] (3) The clean nickel foam was completely immersed in the reaction solution and allowed to react for 10 hours. After the reaction was completed, the nickel foam was taken out, washed with deionized water, and dried at 40° C. for 10 hours. The hydrogen evolution electrode catalyst A1 was obtained.

[0061] Example 2

[0062] The method in Example 1 was used, except that the reaction solution was prepared as follows: 0.008 g of silver nitrate was added to 50 mL of ammonium persulfate solution (containing 0.3 g of ammonium persulfate), dissolved and mixed. Other operations and conditions were the same as in Example 1 to obtain hydrogen evolution electrode catalyst A2.

[0063] Example 3

[0064] The method in Example 1 was used, except that the reaction solution was prepared as follows: 0.032 g of silver nitrate was added to 80 mL of ammonium persulfate solution (containing 0.9 g of ammonium persulfate), dissolved and mixed. Other operations and conditions were the same as in Example 1 to obtain hydrogen evolution electrode catalyst A3.

[0065] Example 4

[0066] The method in Example 1 was used, except that the reaction solution was prepared as follows: 0.045 g of silver nitrate was added to 60 mL of ammonium persulfate solution (containing 0.6 g of ammonium persulfate), dissolved and mixed. Other operations and conditions were the same as in Example 1 to obtain hydrogen evolution electrode catalyst A4.

[0067] Example 5

[0068] The method in Example 1 was adopted, except that a nickel foam with a thickness of 1 mm (with unchanged pore size) was used as the carrier raw material. Other operations and conditions were the same as those in Example 1, to obtain a hydrogen evolution electrode catalyst A5.

[0069] Example 6

[0070] The method in Example 1 was adopted, except that nickel foam with a thickness of 0.8 mm (with unchanged pore size) was used as the carrier raw material. Other operations and conditions were the same as those in Example 1, to obtain hydrogen evolution electrode catalyst A6.

[0071] Example 7

[0072] The method in Example 1 was adopted, except that nickel foam with a thickness of 1.6 mm (with unchanged pore size) was used as the carrier raw material. Other operations and conditions were the same as those in Example 1, to obtain hydrogen evolution electrode catalyst A7.

[0073] Example 8

[0074] The method in Example 1 was used, except that the silver nitrate in the reaction solution was replaced with 0.001 g of Ag particles (average particle size of about 0.2 μm). Other operations and conditions were the same as in Example 1 to obtain hydrogen evolution electrode catalyst A8.

[0075] Example 9

[0076] The method in Example 1 was used, except that silver nitrate was not added to the reaction solution. Instead, after the nickel foam was made into Ni / NiO material (i.e., carrier) using the reaction solution, 0.001 g of Ag particles (average particle size of about 0.2 μm) were loaded on the Ni / NiO material by an impregnation method. Other operations and conditions were the same as those in Example 1 to obtain a hydrogen evolution electrode catalyst A9.

[0077] Test Example 1

[0078] The catalysts obtained in the above examples were observed using a scanning electron microscope, and it was found that catalysts A1-A7 had a unique dendritic structure ( Figure 1 The SEM image of A1 is shown in the figure, and the SEM images of A2-A7 are similar). Catalysts A8 and A9 do not have such a dendritic structure, and the Ag particles are directly loaded on the surface of the Ni / NiO material ( Figure 3 The SEM image of catalyst A8 is shown, and the SEM image of A9 has similar features).

[0079] The content of Ni and NiO in the catalysts obtained in the above examples and the loading amount of Ag were detected by X-ray photoelectron spectroscopy (XPS) respectively, and the weight ratio of Ni and NiO in the carrier of each catalyst and the weight ratio of Ni provided by Ag and NiO in the catalyst were calculated. The results are shown in Table 1.

[0080] Table 1

[0081] catalyst Weight ratio of Ni to NiO Ag loading (wt.%) Weight ratio of Ni provided by Ag to NiO A1 30 0.45 1:7.7 A2 45 0.2 1:11 A3 22 0.8 1:5.5 A4 32 1.02 1:3.1 A5 58 0.21 1:8.2 A6 47 0.30 1:7.1 A7 64 0.14 1:11.4 A8 34 0.8 1:3.7 A9 41 0.5 1:4.9

[0082] Test Example 2

[0083] The catalyst prepared in the above example was used as a working electrode to detect its HER performance.

[0084] The specific method is as follows:

[0085] The electrochemical test experiment was conducted using the Shanghai Chenhua 760E electrochemical workstation. Before the test, N2 was passed through the electrolyte for about 30 minutes to saturate the electrolyte with N2. Subsequently, the three-electrode test system was assembled so that the voltage test range was set at (-0.1 to 0.1V (vs. RHE)) and the number of test cycles was set to 20 cycles to fully activate the sample and expose the active sites. H2 was then passed through the electrolyte using a hydrogen generator for 30 minutes to fully saturate the electrolyte with H2, and an LSV test was performed at 0 to -0.6V. Using 1M KOH as the electrolyte, at 10mA·cm -2 The HER overpotential of the catalyst was tested at the current density. The electrolysis conditions were kept unchanged, and the HER overpotential of the catalyst was tested again after the working electrode worked continuously for 12 hours. The results are shown in Table 2. Figure 2 The LSV diagram (0h) of catalyst A1 is shown as an example for reference.

[0086] Table 2

[0087]

[0088] Note: It is difficult for catalysts A8 and A9 to achieve long-term continuous operation. After about 10 hours, the hydrogen evolution capacity has decreased by more than 10%, so the overpotential after 12 hours of continuous operation was not tested.

[0089] The preferred embodiments of the present invention are described in detail above, but the present invention is not limited thereto. Within the technical concept of the present invention, the technical solution of the present invention can be subjected to a variety of simple modifications, including the combination of various technical features in any other suitable manner, and these simple modifications and combinations should also be regarded as the contents disclosed by the present invention and belong to the protection scope of the present invention.

Claims

1. A hydrogen evolution electrode catalyst, characterized in that The catalyst includes a carrier and Ag loaded on the carrier, and the carrier includes NiO.

2. The hydrogen evolution electrode catalyst according to claim 1, wherein The carrier further comprises Ni, and more preferably the carrier is a composite material composed of Ni and NiO; Preferably, in the carrier, the weight ratio of Ni to NiO is 20-70:1, preferably 25-50:

1.

3. The hydrogen evolution electrode catalyst according to claim 1, wherein The thickness of the carrier is 0.5-2 mm, preferably 0.5-1 mm; And / or, the carrier has a pore size of 0.01-0.6 mm and a porosity of 70-90%.

4. The hydrogen evolution electrode catalyst according to claim 1, wherein In the catalyst, the loading amount of Ag is 0.1-1.5 wt %, preferably 0.13-1.25 wt %, based on the total weight of the catalyst; Preferably, the catalyst has a dendritic structure, preferably a dendrite trunk length of 5-15 μm, a diameter of 0.5-3 μm, a side branch length of 1-5 μm, and a diameter of 0.3-2.5 μm; Preferably, calculated on an element basis, in the catalyst, the weight ratio of Ag to Ni provided by NiO is 1:3-17, preferably 1:5-12.

5. A method for preparing a hydrogen evolution electrode catalyst, characterized in that: The method comprises: contacting a carrier raw material made of a single substance Ni with a reaction solution containing an oxidant and a silver source, so that Ag is loaded on the carrier during the formation of NiO.

6. The method according to claim 5, wherein: The carrier raw material is selected from nickel foam; Preferably, the thickness of the nickel foam is 0.5-2 mm, preferably 0.5-1 mm; Preferably, the pore size of the nickel foam is 0.01-0.6 mm, and the porosity is 70-90%.

7. The method according to claim 5, wherein: The oxidant is selected from at least one of persulfate, persulfate and hydrogen peroxide; Preferably, the oxidant is selected from at least one of persulfate or persulfate, preferably at least one of ammonium persulfate, sodium persulfate and potassium persulfate; and / or, the content of the silver source in the reaction solution is such that the Ag loading in the prepared catalyst is 0.1-1.5 wt %, preferably 0.13-1.25 wt %, based on the total weight of the catalyst; Preferably, in the reaction solution, the weight ratio of the silver source to the oxidant is 1:10-50; Preferably, the silver source is selected from water-soluble compounds of Ag, preferably silver nitrate.

8. The method according to any one of claims 5 to 7, wherein: The contacting method includes placing the carrier raw material into the reaction solution and leaving it to stand for 10-30 hours. Preferably, the carrier raw material is completely immersed in the reaction solution.

9. A hydrogen evolution electrode catalyst prepared according to the method according to any one of claims 5 to 8.

10. A method for preparing hydrogen, characterized in that: The method comprises contacting the hydrogen evolution electrode catalyst according to any one of claims 1 to 4 and 9 with an electrolyte and reacting under electrolysis conditions.

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