AEMWE anode non-noble metal catalyst, catalyst slurry, membrane electrode, electrolytic cell and preparation method

Abstract

The invention belongs to the technical field of water electrolysis, and particularly relates to an anode non-noble metal catalyst for AEMWE, catalyst slurry, a membrane electrode, an electrolytic bath and a preparation method. The non-noble metal catalyst NiCo2O4 prepared by the preparation method of the anode non-noble metal catalyst for AEMWE provided by the invention is excellent in performance and simple in preparation cost; meanwhile, the preparation method of the catalyst NiCo2O4 is further improved by controlling the ratio of the water-soluble nickel salt to the water-soluble cobalt salt in the preparation method, controlling the addition of the alkaline solution and controlling the sintered nickel-cobalt hydroxide, so that the technical problem that a large-scale synthesis method of the anode catalyst for the high-performance AEMWE is lacked in the prior art is solved.

Description

Technical Field

[0001] This application belongs to the technical field of electrolyzed water, and particularly relates to an anode non-precious metal catalyst for AEMWE, a catalyst slurry, a membrane electrode, an electrolytic cell, and a preparation method thereof. Background Technique

[0002] When hydrogen and oxygen react to release energy, water is generated. Therefore, the hydrogen produced by electrolyzing water to produce hydrogen is a green and clean energy source. Currently, the production of hydrogen by electrolyzing water mainly includes four technologies: alkaline electrolyzed water for hydrogen production, proton exchange membrane electrolyzed water for hydrogen production, anion exchange membrane electrolyzed water for hydrogen production (AEMWE), and high-temperature solid oxide electrolyzed water for hydrogen production.

[0003] Alkaline electrolyzed water has the advantages of low cost and the use of non-precious metal catalysts, etc. However, problems such as strong corrosiveness of its electrolyte and low electrolysis efficiency limit the development of this technology. Proton exchange membrane electrolyzed water has the advantages of high current density and high electrolysis efficiency, etc., but usually requires the use of noble metal catalysts such as IrO 2 etc., which increases the cost of hydrogen production. High-temperature solid oxide electrolyzed water for hydrogen production is to electrolyze water through a solid oxide electrolytic cell at a high temperature of about 800 °C to generate hydrogen at the cathode and oxygen at the anode. The high-temperature environment makes the catalyst more active and improves the catalytic efficiency. However, the catalytic process requires additional energy to maintain the high-temperature operating state, has a slow start-stop speed and fast attenuation. And anion exchange membrane electrolyzed water (AEMWE) uses non-precious metal catalysts and conducts OH - ions through an anion exchange membrane. It combines the advantages of low cost of alkaline electrolyzed water for hydrogen production and high electrolysis efficiency of proton exchange membrane electrolyzed water for hydrogen production, and is generally considered to be the most promising hydrogen production technology in the future.

[0004] Anion exchange membrane electrolyzed water (AEMWE) is usually carried out in an electrolytic cell. Its core component is a membrane electrode assembly. The anode side of the membrane electrode assembly is an oxygen evolution reaction, and the reaction principle is 4OH - →O 2 +2H 2 O + 4e, and the cathode side is a hydrogen evolution reaction, and the reaction principle is 2H 2 O + 2e → H 2 + 2OH - ; Through the reaction principle, it can be found that the oxygen evolution reaction (OER) on the anode side proceeds through 4-electron transfer, while the hydrogen evolution reaction (HER) on the cathode side proceeds through 2-electron transfer. Therefore, the slow kinetics of the oxygen evolution reaction (OER) is the main factor limiting the electrolysis efficiency of anion exchange membrane electrolyzed water (AEMWE); Although noble metal catalysts IrO 2 and RuO 2It is widely used in the research of anion exchange membrane water electrolysis (AEMWE) due to its low overpotential and used as a benchmark catalyst. However, its high cost and low stability limit the large-scale commercial application of AEMWE. It is crucial to develop a non-noble metal catalyst with high catalytic activity and high stability for the oxygen evolution reaction (OER) on the anode side in AEMWE. Transition metal catalysts (such as Ni, Fe, Co, etc.) are very suitable for use in AEMWE as anode non-noble metal catalysts because of their rich raw material resources, low price, and high catalytic activity in alkaline media. Currently, the anode catalysts for AEMWE prepared using transition metal catalysts mainly include self-supporting LDH catalysts and NiFe catalysts. The unique layered structure of LDH catalysts gives them a large specific surface area, which can provide more active sites, facilitate the adsorption and reaction of reactant molecules, and improve the catalytic efficiency. However, LDH catalysts are generally prepared by electrodeposition or hydrothermal growth methods. The synthesis conditions are harsh, the growth may be poor in some local areas, the uniformity is poor, and the synthesis amount at one time is small. For NiFe catalysts, they are currently mainly prepared by co-precipitation method, electrodeposition or hydrothermal synthesis method. The NiFe catalysts have poor stability and low performance. Currently, there is a lack of a large-scale synthesis method for high-performance anode catalysts for AEMWE. Summary of the Invention

[0005] In view of this, the present application provides an anode non-noble metal catalyst for AEMWE, a catalyst slurry, a membrane electrode and an electrolytic cell, and a preparation method thereof, which are used to solve the technical problem of the lack of a large-scale synthesis method for high-performance anode catalysts for AEMWE.

[0006] The first aspect of the present application provides a preparation method of an anode non-noble metal catalyst for AEMWE. The preparation method includes the following steps:

[0007] Step S1: Dissolve a water-soluble nickel salt and a water-soluble cobalt salt in water to obtain a nickel-cobalt aqueous solution;

[0008] Step S2: Add an alkali solution to the nickel-cobalt aqueous solution for a precipitation reaction to obtain nickel-cobalt hydroxide;

[0009] Step S3: Sinter the nickel-cobalt hydroxide at a high temperature to obtain the anode non-noble metal catalyst nickel cobalt nickelate for AEMWE.

[0010] Preferably, in step S1, the water-soluble nickel salt is selected from at least one of nickel acetate, nickel citrate, nickel sulfate, nickel nitrate, and nickel chloride;

[0011] The water-soluble cobalt salt is selected from at least one of cobalt acetate, cobalt oxalate, cobalt sulfate, cobalt nitrate, cobalt chloride, or their hydrates.

[0012] Preferably, in step S2, the alkali solution is selected from at least one of sodium hydroxide solution, potassium hydroxide solution, barium hydroxide solution, and ammonia water.

[0013] Preferably, in step S1, the molar ratio of nickel ions to cobalt ions in the nickel-cobalt aqueous solution is 1:2.

[0014] Preferably, the molar ratio of hydroxide ions in the alkali solution in step S2, nickel ions, and cobalt ions in the nickel-cobalt aqueous solution in step S1 is 8:1:2.

[0015] Preferably, the process of adding the alkali solution in step S2 to the nickel-cobalt aqueous solution for precipitation reaction is as follows:

[0016] The alkali solution is added dropwise to the nickel-cobalt aqueous solution until the color of the nickel-cobalt aqueous solution no longer changes, obtaining a nickel-cobalt hydroxide precursor solution;

[0017] Detect the pH of the nickel-cobalt hydroxide precursor solution. When the pH of the nickel-cobalt hydroxide precursor solution is less than 12, add the alkali solution again to obtain a nickel-cobalt hydroxide precursor solution with a pH greater than 12, and let it stand overnight for 12 h for precipitation reaction;

[0018] Detect the pH of the nickel-cobalt hydroxide precursor solution. When the pH of the nickel-cobalt hydroxide precursor solution is greater than 12, let it stand overnight for 12 h for precipitation reaction.

[0019] This application adopts a three-stage pH control strategy of "dropwise addition - color change - detection", uses the color change of the solution as a real-time indication of the reaction process, combines the end-point control with a forced pH ≥ 12 to ensure that the hydroxide precipitation rate > 99%, close to complete precipitation, and through a 12-hour standing process, realizes the uniform growth of hydroxides.

[0020] Preferably, in step S3, the heating rate of the high-temperature sintering is 4 °C / min, the temperature is 300 - 400 °C, and the time is 2 - 6 h.

[0021] Preferably, the sintering temperature is 350 °C.

[0022] The second aspect of this application provides a non-precious metal anode catalyst for AEMWE, which is prepared by the preparation method described in the first aspect.

[0023] The third aspect of this application provides a non-precious metal anode catalyst slurry for AEMWE, which is obtained by mixing a non-precious metal anode catalyst for AEMWE prepared in the first aspect, a Nafion solution, and isopropanol.

[0024] The fourth aspect of the present application provides a membrane electrode, comprising an anion exchange membrane, a cathode electrode and an anode electrode;

[0025] The cathode electrode is disposed on the cathode side of the anion exchange membrane, and the anode electrode is disposed on the anode side of the anion exchange membrane. The catalyst layer in the anode electrode is obtained by drying the anode non-precious metal catalyst slurry for AEMWE described in the third aspect.

[0026] The fifth aspect of the present application provides an electrolytic cell, comprising a membrane electrode described in the fourth aspect.

[0027] Compared with the prior art, the anode non-precious metal catalyst for AEMWE provided by the present application has at least the following beneficial effects:

[0028] 1. The anode non-precious metal catalyst NiCo for AEMWE prepared by the preparation method provided by the present application 2 O 4 has a low overpotential, can generate a higher current density at the same potential, requires a lower voltage at the same current density, and has good stability. It is an anode non-precious metal catalyst with excellent performance for AEMWE; at the same time, the preparation process is simple, without harsh conditions, and is particularly suitable for batch preparation above the large kilogram level to meet the commercial application requirements of AEMWE.

[0029] 2. In the step of preparing the nickel-cobalt aqueous solution in the preparation method of the anode non-precious metal catalyst NiCo for AEMWE provided by the present application 2 O 4 by controlling the addition amounts of the water-soluble nickel salt and the water-soluble cobalt salt, the molar ratio of nickel ions to cobalt ions in the nickel-cobalt aqueous solution is 1:2, corresponding to the chemical composition of the NiCo 2 O 4 spinel structure, realizing one-step stoichiometric control and avoiding secondary formulation of the traditional process.

[0030] 3. In the step of adding an alkali solution to the nickel-cobalt aqueous solution for precipitation reaction in the preparation method of the anode non-precious metal catalyst NiCo for AEMWE provided by the present application 2 O 4 a three-stage pH control strategy of "dropwise addition - color change - detection" is adopted. By using the color change of the solution as a real-time indication of the reaction progress and combining the end-point control with a forced pH≥12, it is ensured that the precipitation rate of nickel-cobalt hydroxide >99%, approaching complete precipitation, and through a 12-hour static process, uniform growth of the hydroxide is achieved.

[0031] 4. The anode non-precious metal catalyst NiCo for AEMWE provided by the present application 2 O 4In the sintering step of the preparation method, low-temperature sintering at 350 °C is combined with a gradient heating rate of 4 °C / min to achieve the spinel phase transformation of NiCo while maintaining the integrity of the nanostructure. 2 O 4 spinel phase transformation. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] In order to more clearly illustrate the specific embodiments of the present application or the technical solutions in the prior art, the following will briefly introduce the drawings required for the description of the specific embodiments or the prior art. Obviously, the drawings in the following description are some embodiments of the present application. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0033] Figure 1 X-ray diffraction pattern of the anode non-noble metal catalyst for AEMWE prepared by the preparation method provided in Example 1 of the present application;

[0034] Figure 2 Polarization curve of the anode non-noble metal catalyst for AEMWE prepared by the preparation method provided in Example 1 of the present application and the commercially available catalyst IrO 2 of;

[0035] Figure 3 Polarization curve of the anode non-noble metal catalyst for AEMWE prepared by the preparation method provided in Example 1 of the present application and the commercially available catalysts IrO 2 , NiCoRu, Co 3 O 4 Overpotential test results of, NiMn;

[0036] Figure 4 Voltage-current density test results of the anode non-noble metal catalyst for AEMWE prepared by the preparation method provided in Example 1 of the present application and NiCoRu, Co 3 O 4 , NiPt;

[0037] Figure 5 Stability result diagram of the anode non-noble metal catalyst for AEMWE prepared by the preparation method provided in Example 1 of the present application. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0038] The present application provides an anode non-noble metal catalyst for AEMWE, a catalyst slurry, a membrane electrode, an electrolytic cell, and a preparation method, which are used to solve the technical problem of the lack of a large-scale synthesis method for high-performance anode catalysts for AEMWE.

[0039] The technical solution of the present application will be clearly and completely described below in conjunction with the accompanying drawings. Obviously, the described embodiments are part of the embodiments of the present application, rather than all of them. All other embodiments obtained by those of ordinary skill in the art based on the embodiments in the present application without creative efforts shall fall within the protection scope of the present application.

[0040] Example 1

[0041] The preparation method of the anodic non-noble metal catalyst for AEMWE provided in Example 1 of the present application includes the steps of preparing a nickel-cobalt aqueous solution, preparing nickel-cobalt hydroxide, and high-temperature sintering.

[0042] The step of preparing the nickel-cobalt aqueous solution includes: weighing 10 mol of nickel chloride and 20 mol of cobalt chloride hexahydrate according to a molar ratio of 1:2, adding them to a reaction kettle, and then adding a certain amount of water, with a weight 50 times the total mass of nickel chloride and cobalt chloride hexahydrate, and stirring for 30 min to dissolve to form a nickel-cobalt aqueous solution.

[0043] The step of preparing nickel-cobalt hydroxide includes: weighing 40 L of 2 mol / L NaOH solution according to a molar ratio of 8:1:2, adding it to the nickel-cobalt aqueous solution and stirring, standing overnight for 12 h to precipitate, and then washing the precipitate 3 times with deionized water to remove chlorides, and centrifuging to obtain nickel-cobalt hydroxide.

[0044] The step of high-temperature sintering includes: first drying the nickel-cobalt hydroxide at 80 °C to remove moisture, and then heating it to 350 °C at a heating rate of 4 °C / min and sintering for 4 h to obtain a black anodic non-noble metal catalyst NiCo for AEMWE 2 O 4 .

[0045] Example 2

[0046] The preparation method of the anodic non-noble metal catalyst for AEMWE provided in Example 2 of the present application is different from that of Example 1 in the step of adding an alkali solution to prepare nickel-cobalt hydroxide, including the steps of preparing a nickel-cobalt aqueous solution, preparing nickel-cobalt hydroxide, and high-temperature sintering.

[0047] The step of preparing the nickel-cobalt aqueous solution includes: weighing 10 mol of nickel chloride and 20 mol of cobalt chloride hexahydrate according to a molar ratio of 1:2, adding them to a reaction kettle, and then adding a certain amount of water, with a weight 50 times the total mass of nickel chloride and cobalt chloride hexahydrate, and stirring for 30 min to dissolve to form a nickel-cobalt aqueous solution.

[0048] The steps for preparing nickel-cobalt hydroxide include: while stirring, adding 2 mol / L NaOH solution dropwise to the nickel-cobalt aqueous solution. During this process, the color of the solution will change from green to blue. After the solution no longer changes color, measure its pH value. At this time, the pH is generally above 12. If the pH is not above 12, continue to add NaOH solution to prevent insufficient pH from resulting in a small amount of precipitate. Let it stand overnight for 12 h to precipitate the precipitate, and then wash the precipitate 3 times with deionized water to remove chlorides, and centrifuge to obtain nickel-cobalt hydroxide.

[0049] The steps for high-temperature sintering include: first drying the nickel-cobalt hydroxide at 80 °C to remove moisture, and then heating it to 350 °C at a heating rate of 4 °C / min and sintering for 4 h to obtain the black anode non-noble metal catalyst NiCo for AEMWE. 2 O 4 。

[0050] Experimental Example 1

[0051] In this Experimental Example 1, the anode non-noble metal catalyst NiCo for AEMWE provided in Example 1 2 O 4 was subjected to performance testing.

[0052] The performance testing process includes: adding a Nafion solution with a mass fraction of about 20% and a certain amount of isopropanol solvent to the anode non-noble metal catalyst NiCo for AEMWE 2 O 4 , stirring at high speed to disperse evenly to form a stable catalyst slurry, and then evenly coating the catalyst slurry on the nickel felt to form a CCS electrode as the test sample; at the same time, the performances of commercially available catalysts IrO 2 , NiCoRu, Co 3 O 4 , NiMn, and NiPt were also tested.

[0053] Among them, the X-ray diffraction of the anode non-noble metal catalyst NiCo for AEMWE prepared in the example 2 O 4 is as shown in Figure 1 . It can be seen from Figure 1 that the XRD peaks of the anode non-noble metal catalyst NiCo for AEMWE prepared by the preparation method provided in the example 2 O 4 are completely consistent with the standard card, indicating that the preparation method provided in this example successfully prepared NiCo 2 O 4 .

[0054] The anode non-noble metal catalyst NiCo for AEMWE prepared in the example 2 O4 and the catalyst IrO 2 The polarization curves are as follows Figure 2 shown Figure 2 The abscissa in is the potential (V) relative to the reversible hydrogen electrode (RHE), and the ordinate is the current density (mA / cm²); it can be seen from Figure 2 that at the same potential, the higher the current density of the AEMWE using the anodic non-noble metal catalyst NiCo 2 O 4 is, the better the electrocatalytic activity of the catalyst NiCo 2 O 4 is, which can generate a larger current per unit area and promote the progress of the electrochemical reaction.

[0055] The anodic non-noble metal catalyst NiCo 2 O 4 for AEMWE prepared in the examples and the catalysts IrO 2 , NiCoRu, Co 3 O 4 , NiMn were tested for overpotential as Figure 3 shown; it can be seen from Figure 3 that the overpotential of the catalyst NiCo 2 O 4 is the lowest, being 271 mV, indicating that the catalyst NiCo 2 O 4 requires less additional energy to drive the reaction at the same current density, and the electrocatalytic performance of the catalyst NiCo 2 O 4 is better.

[0056] The anodic non-noble metal catalyst NiCo 2 O 4 for AEMWE prepared in the examples and the catalysts NiCoRu, Co 3 O 4 , electrodeposited NiPt were tested for voltage-current density at 80 °C and 1 mol / L KOH conditions as Figure 4 shown; it can be seen from Figure 4 that at the same current density, the lower the voltage required for the catalyst NiCo 2 O 4 , for example, at a current density of 1 A / cm 2 , NiCo 2 O 4 only requires a voltage of 1.75 V, while the voltages of NiCo 2 Ru, Co 3 O 4 and electrodeposited NiPt are 1.87 V, 1.97 V and 1.90 V respectively, which indicates that the catalyst NiCo2 O 4 The smaller the energy loss in the electrochemical reaction, the more excellent the electrocatalytic performance.

[0057] The anode non-noble metal catalyst NiCo for AEMWE prepared in the examples 2 O 4 Under the conditions of 80 °C and a constant current of 1 A / cm 2 A test lasting for 70 hours was carried out as Figure 5 shown; from Figure 5 it can be seen that the catalyst NiCo 2 O 4 hardly degrades, which indicates that the catalyst NiCo 2 O 4 has high stability.

[0058] The above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit them; although the present application has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that: they can still modify the technical solutions recorded in the foregoing embodiments, or perform equivalent replacements on some or all of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present application.

Claims

1. A method for preparing an anode non-precious metal catalyst for AEMWE, characterized in that: The following steps are involved: Step S1, dissolving a water-soluble nickel salt and a water-soluble cobalt salt in water to obtain a nickel-cobalt aqueous solution; Step S2, adding an alkaline solution into a nickel-cobalt aqueous solution to carry out a precipitation reaction to obtain nickel-cobalt hydroxide; Step S3, sintering nickel cobalt hydroxide at high temperature to obtain anode non-precious metal catalyst for AEMWE.

2. The method for preparing an anode non-precious metal catalyst for AEMWE according to claim 1, characterized in that: The water-soluble nickel salt is selected from at least one of nickel acetate, nickel citrate, nickel sulfate, nickel nitrate and nickel chloride; The water-soluble cobalt salt is selected from at least one of cobalt acetate, cobalt oxalate, cobalt sulfate, cobalt nitrate and cobalt chloride or a hydrate thereof; The alkaline solution is selected from at least one of sodium hydroxide solution, potassium hydroxide solution, barium hydroxide solution and ammonia water.

3. The method for preparing an anode non-precious metal catalyst for AEMWE according to claim 1, characterized in that: The molar ratio of nickel ions to cobalt ions in the nickel-cobalt aqueous solution is 1:

2.

4. The method for preparing an anode non-precious metal catalyst for AEMWE according to claim 1, characterized in that: The molar ratio of the hydroxide in the alkaline solution to the nickel ions and the cobalt ions in the nickel-cobalt aqueous solution is 8:1:

2.

5. The method for preparing an anode non-precious metal catalyst for AEMWE according to claim 1, characterized in that: The process of adding the alkaline solution into the nickel-cobalt aqueous solution to carry out precipitation reaction is: Adding the alkaline solution dropwise into the nickel-cobalt aqueous solution until the nickel-cobalt aqueous solution no longer changes color, thereby obtaining a nickel-cobalt hydroxide precursor solution; Detecting the pH of the nickel-cobalt hydroxide precursor solution, and when the pH of the nickel-cobalt hydroxide precursor solution is less than 12, adding the alkaline solution again to obtain a nickel-cobalt hydroxide precursor solution with a pH greater than 12, and standing it overnight for 12 hours to perform a precipitation reaction; The pH of the nickel-cobalt hydroxide precursor solution was detected. When the pH of the nickel-cobalt hydroxide precursor solution was greater than 12, the solution was allowed to stand overnight for 12 hours for precipitation reaction.

6. The method for preparing an anode non-precious metal catalyst for AEMWE according to claim 1, characterized in that: The high temperature sintering has a heating rate of 4°C / min, a temperature of 300-400°C, and a time of 2-6h.

7. An anode non-precious metal catalyst for AEMWE, characterized in that: The catalyst is prepared by the method for preparing an anode non-precious metal catalyst for AEMWE as described in any one of claims 1 to 6.

8. A non-precious metal anode catalyst slurry for AEMWE, characterized in that: The AEMWE is obtained by mixing the anode non-precious metal catalyst for AEMWE as described in claim 7, Nafion solution and isopropanol.

9. A membrane electrode, characterized in that: It includes an anion exchange membrane, a cathode electrode and an anode electrode; The cathode electrode is arranged on the cathode side of the anion exchange membrane, the anode electrode is arranged on the anode side of the anion exchange membrane, and the catalyst layer in the anode electrode is obtained by drying the anode non-precious metal catalyst slurry for AEMWE as described in claim 8.

10. An electrolytic cell, characterized in that: A membrane electrode comprising the membrane electrode as claimed in claim 9.

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