Preparation method of anode catalyst of anion exchange membrane water electrolyzer

Abstract

The application belongs to the technical field of new energy materials, and specifically discloses a preparation method of an anode catalyst of an anion exchange membrane water electrolyzer, which comprises the following steps: (1) preparing a precursor solution: dissolving a Ni salt and a Fe salt in an oleylamine solution, and stirring and uniformly mixing to obtain the precursor solution; (2) adding a phosphorus source and a reducing agent: adding the phosphorus source and the reducing agent to the precursor solution prepared in step (1), stirring and uniformly mixing to obtain a mixed solution; (3) preparing NiFeP: passing the mixed solution prepared in step (2) into a protective gas for gas washing to remove impurities; adjusting the temperature and setting a temperature rising program, running the program, and after the temperature rising process is completed, the preparation of the NiFeP catalyst is completed. The nanoscale NiFeP catalyst prepared by the application exhibits extremely low cell voltage in AEMWE testing, which is superior to commercial IrO2; the NiFeP catalyst has excellent stability and excellent energy efficiency, and thus has a wide application prospect and high commercial value.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of new energy materials, and particularly relates to a preparation method of an anode catalyst of an anion exchange membrane water electrolyzer. BACKGROUND

[0002] An anion exchange membrane water electrolyzer (AEMWE) is a new type of water electrolysis technology, which uses an anion exchange membrane (AEM) to separate the anode and the cathode in the electrolyzer. The high ion selectivity of the AEM can effectively transfer OH - to prevent gas crossover and electrolyte crossover, thereby improving the electrolysis efficiency and the purity of hydrogen. The high overpotential of the anode oxygen evolution reaction (OER) is much higher than that of the cathode hydrogen evolution reaction (HER), which means that most of the energy loss occurs in the OER of the anode during the water electrolysis process, resulting in excessively high cell voltage. Therefore, it is necessary to develop a new type of anode catalyst to reduce the energy consumption of the reaction and accelerate the rate of water electrolysis to produce hydrogen.

[0003] Hydrogen is a green and efficient energy carrier, and water electrolysis to produce hydrogen is widely considered as one of the most promising green hydrogen production methods due to its environmental friendliness, pure product and no carbon emissions during production. In the process of water electrolysis, OER is a key half-reaction responsible for the decomposition of water or hydroxide into oxygen. However, the high energy consumption of the OER reaction, especially its large overpotential, has become a major obstacle to the large-scale application of this technology. Therefore, researchers are working to find solutions to achieve the commercial deployment of water electrolysis to produce hydrogen technology. Although traditional noble metal catalysts perform excellently in terms of performance, they face the main problem of limited natural resources and high cost. Therefore, it is particularly crucial to develop non-noble metal catalysts that are both high in catalytic performance and cost-effective. Commercial RuO2 and IrO2 are usually used as standards for evaluating OER performance, but compared with NiFe-based catalysts, they are extremely cost-ineffective. Therefore, developing advanced NiFe-based catalysts to replace traditional noble metal catalysts not only has broad application prospects, but also has significant commercial value. SUMMARY

[0004] The purpose of the present application is to overcome the defects existing in the prior art, and to provide a preparation method of an anode catalyst of an anion exchange membrane water electrolyzer.

[0005] Nickel iron phosphide (NiFeP) is a transition metal phosphide, in which Ni and Fe belong to 3d group materials, and their d orbital holes may be related to catalytic activity, providing active sites during the reaction and helping the OER to proceed. The present application prepares a nanoscale NiFeP catalyst, which, in AEMWE testing, has a current density of 60 ℃, 1 Acm -2The NiFeP prepared by the method exhibits extremely low slot voltage (1.71 V) under the condition, which is superior to commercial IrO2. In addition, the NiFeP has excellent stability and energy efficiency, and exhibits excellent performance in AEMWE test. Therefore, the NiFeP prepared by the method can play an important role in future hydrogen energy conversion technology due to high activity and low cost.

[0006] To achieve the above object, one of the technical solutions of the present application is a preparation method of an anion exchange membrane water electrolysis cell anode catalyst, comprising the following steps:

[0007] (1) configuring a precursor solution: dissolving a Ni salt and a Fe salt in oleylamine to obtain a precursor solution;

[0008] (2) adding a phosphorus source and a reducing agent: adding a phosphorus source and a reducing agent to the precursor solution prepared in step (1) to obtain a mixed solution;

[0009] (3) preparing NiFeP: passing the mixed solution prepared in step (2) into a protective gas to remove impurities; adjusting the temperature and setting the temperature rising program, running the program, and completing the preparation of the NiFeP catalyst after the temperature rising process is completed.

[0010] In a preferred embodiment of the present application, the Ni salt in step (1) is nickel acetylacetone, the Fe salt is iron acetylacetone, the concentration of the Ni salt in the precursor solution is 0.01-0.04 mol / L, and the concentration of the Fe salt in the precursor solution is 0.01-0.05 mol / L.

[0011] In a preferred embodiment of the present application, the concentration of the oleylamine solution in step (1) is 70-85 vol%.

[0012] In a preferred embodiment of the present application, the phosphorus source and the reducing agent in step (2) are n-octyl phosphine, which is both a reducing agent and a phosphating agent. Adding the "P" source and the reducing agent means adding 180-250 uL of n-octyl phosphine with a purity of 99% to the above 10 mL mixed solution, at which time the n-octyl phosphine is both a reducing agent and a phosphating agent, and finally stirring for 30 min to fully mix the solution.

[0013] In a preferred embodiment of the present application, the volume ratio of the phosphorus source and the reducing agent to the precursor solution in step (2) is 180-250:800-1200.

[0014] In a preferred embodiment of the present application, the protective atmosphere in step (3) is high-purity inert gas N2 or Ar.

[0015] In a preferred embodiment of the present application, the temperature rising procedure in step (3) is a three-stage temperature rising procedure, the first stage is to rise the temperature from 20 DEG C to 50 DEG C at a temperature rising rate of 8-10 DEG C / min, keep the temperature for 20-40 min, the second stage is to rise the temperature from 50 DEG C to 100 DEG C at a temperature rising rate of 18-22 DEG C / min, keep the temperature for 20-40 min, the third stage is to rise the temperature from 100 DEG C to 270 DEG C at a temperature rising rate of 14-16 DEG C / min, keep the temperature for 50-70 min, and then naturally cool to room temperature after the temperature keeping is completed.

[0016] To achieve the above object, the second technical scheme of the present application is an anode catalyst for an anion exchange membrane water electrolyzer prepared by the above preparation method.

[0017] Compared with the prior art, the present application has the following beneficial effects:

[0018] 1. The prepared catalyst NiFeP can effectively promote the generation of oxygen in the water splitting reaction in AEMWE, and has high activity and energy efficiency;

[0019] 2. The prepared NiFeP catalyst exhibits excellent electrochemical stability in AEMWE, can withstand corrosion and oxidation during long-term electrolysis, and maintains high activity during long-term operation, thereby improving the overall economic benefit;

[0020] 3. The prepared NiFeP catalyst has extremely low cost compared with RuO2 or IrO2 and Pt / C, and has great potential in large-current AEMWE hydrogen production technology, and the development of NiFeP catalyst to replace traditional noble metal oxides has great application prospect and commercial value;

[0021] 4. The synthesis process of the NiFeP catalyst of the present application usually adopts an environmentally friendly chemical method, and the catalytic process does not produce harmful substances, which meets the principles of sustainable development and green chemistry. BRIEF DESCRIPTION OF DRAWINGS

[0022] Figure 1 TEM of NiFeP prepared for Example 1 at different resolutions and particle size distribution diagram of NiFeP;

[0023] Figure 2 Dark field TEM of NiFeP prepared for Example 1, and EDX element mapping of each element;

[0024] Figure 3 EDX element content of Ni, Fe and P in NiFeP prepared for Example 1;

[0025] Figure 4a and 4b are the lattice spacing of NiFeP prepared in Example 1, Figure 4 c-d are the XPS spectra of Ni 2p and Fe 2p, respectively;

[0026] Figure 5 a is the LSV of NiFeP tested in RDE, the solution is 1.0M KOH, and the scan rate is 5mV / s, Figure 5 b is a schematic diagram of NiFeP used in AEMWE device, Figure 5 c is the data line of AEMWE test, Figure 5 d is the stability of NiFeP tested in AEMWE device, the current density is 1Acm -2 , Figure 5 e is the voltage efficiency and potential decay rate of NiFeP tested in AEMWE device at 1Acm -2 . DETAILED DESCRIPTION

[0027] In order to make the purpose, technical scheme and advantages of the present application more clear, the present application is described in more detail below in combination with the drawings and specific examples, but the protection scope of the present application is not limited to these examples.

[0028] A preparation method of an anion exchange membrane water electrolysis cell anode catalyst, comprising the following steps:

[0029] (1) configuring a precursor solution: dissolving Ni salt and Fe salt in oleylamine, stirring and mixing uniformly to obtain a precursor solution;

[0030] (2) adding a phosphorus source and a reducing agent: adding a phosphorus source and a reducing agent to the precursor solution prepared in step (1), stirring and mixing uniformly to obtain a mixed solution;

[0031] (3) preparing NiFeP: passing the mixed solution prepared in step (2) into a protective gas for gas washing to remove impurities; adjusting the temperature and setting the temperature rising program, running the program, and when the temperature rising process is completed, the preparation of the NiFeP catalyst is completed.

[0032] In the step (1), the Ni salt is nickel acetylacetonate, the Fe salt is iron acetylacetonate, the concentration of the Ni salt in the precursor solution is 0.01-0.04mol / L, and the concentration of the Fe salt in the precursor solution is 0.01-0.05mol / L.

[0033] In the step (1), the concentration of the oleylamine solution is 70-85vol%.

[0034] In the step (2), the phosphorus source and the reducing agent are n-octyl phosphine, which is both a reducing agent and a phosphating agent.

[0035] The volume ratio of the phosphorus source and the reducing agent to the precursor solution in the step (2) is 180-250:800-1200.

[0036] The protective atmosphere in the step (3) is high-purity inert gas N2 or Ar.

[0037] The temperature rising procedure in the step (3) is a three-stage temperature rising control procedure, the first stage is to rise the temperature from 20℃ to 50℃ at a temperature rising rate of 8-10℃ / min, and to keep the temperature for 20-40min, the second stage is to rise the temperature from 50℃ to 100℃ at a temperature rising rate of 18-22℃ / min, and to keep the temperature for 20-40min, the third stage is to rise the temperature from 100℃ to 270℃ at a temperature rising rate of 14-16℃ / min, and to keep the temperature for 50-70min, and to naturally cool down to room temperature after the keeping temperature procedure is completed.

[0038] An anion exchange membrane water electrolyzer anode catalyst prepared by the above preparation method.

[0039] The anion exchange membrane water electrolyzer anode catalyst needs to be treated with carbon loading before testing, first, a mixed solution of ethanol and n-hexane with a volume ratio of 5:1 is used as a cleaning agent to clean the catalyst to remove residues; the anode catalyst NiFeP catalyst is dispersed in n-hexane, a corresponding amount of carbon carrier is added, and then anhydrous ethanol is added for ultrasonic dispersion, and finally centrifugal separation is carried out at a centrifugal speed of 10000-12000r / min to obtain a carbon-loaded NiFeP with a mass fraction of 20%-50%.

[0040] Example 1

[0041] (1) Take 0.473mmol of acetylacetone nickel and 0.159mmol of acetylacetone iron, mix them in 15mL of 70vol% oleylamine, and stir for 30min to make the above solution fully mixed and uniform. Then take 1mL of the above solution and dilute it to 10mL with 70% oleylamine. Transfer the solution to a three-necked flask and stir thoroughly, add 200uL of n-octyl phosphine and ultrasonic for 30min to complete the preparation stage.

[0042] (2) Transfer the flask to a programmed temperature device, wash with N2 for 20min, and then proceed with the programmed temperature rising. The first stage is to rise the temperature from 20℃ to 50℃ at a rate of 10℃ / min, and to keep the temperature for 30min. The second stage is to rise the temperature from 50℃ to 100℃ at a rate of 20℃ / min, and to keep the temperature for 30min. The third stage is to rise the temperature from 100℃ to 270℃ at a rate of 15℃ / min, and to keep the temperature for 60min. After the 270℃ keeping temperature procedure is completed, naturally cool down to room temperature in the heating jacket. The obtained brown-black sample is NiFeP. Then clean the sample with a mixed solution of ethanol and n-hexane with a volume ratio of 5:1, and finally centrifuge at a speed of 10000r / min to complete the cleaning of NiFeP.

[0043] (3) 1.45 mg of NiFeP was dispersed in 10 mL of n-hexane, 5.77 mg of XC-72 was added, and ultrasonic treatment was performed for 20 min. Then, 30 mL of anhydrous ethanol was added, and ultrasonic treatment was performed for 10 min. Centrifugal separation was performed, and carbon-supported NiFeP was finally obtained.

[0044] Example 2

[0045] (1) 0.315 mmol of nickel acetylacetonate and 0.318 mmol of iron acetylacetonate were mixed in 15 mL of oleylamine with a concentration of 70%, and stirring was performed for 30 min. The solution was sufficiently mixed and uniform. Then, 1 mL of the solution was diluted to 10 mL with 70% oleylamine. The solution was transferred to a three-necked flask, and stirring was performed. Then, 200 uL of n-octyl phosphine was added, and ultrasonic treatment was performed for 30 min. The preparation stage was completed.

[0046] (2) The flask was transferred to a temperature programmed device, and N2 washing was performed for 20 min. Then, temperature programming was performed. In the first stage, the temperature was increased from 20°C to 50°C at a rate of 10°C / min, and temperature maintenance was performed for 30 min. In the second stage, the temperature was increased from 50°C to 100°C at a rate of 20°C / min, and temperature maintenance was performed for 30 min. In the third stage, the temperature was increased from 100°C to 270°C at a rate of 15°C / min, and temperature maintenance was performed for 60 min. After the temperature maintenance program at 270°C was completed, natural cooling was performed in the heating jacket to room temperature. A brown-black sample, i.e., NiFeP, was obtained. Then, the sample was washed, and ultrasonic treatment was performed with a mixed solution of ethanol and n-hexane in a volume ratio of 5:1. Finally, centrifugal separation was performed at a rotation speed of 10,000 r / min, and the washing of NiFeP was completed.

[0047] (3) 1.45 mg of NiFeP was dispersed in 10 mL of n-hexane, 5.77 mg of XC-72 was added, and ultrasonic treatment was performed for 20 min. Then, 30 mL of anhydrous ethanol was added, and ultrasonic treatment was performed for 10 min. Centrifugal separation was performed, and carbon-supported NiFeP was finally obtained.

[0048] Example 3

[0049] (1) 0.315 mmol of nickel acetylacetonate and 0.318 mmol of iron acetylacetonate were mixed in 15 mL of oleylamine with a concentration of 70%, and stirring was performed for 30 min. The solution was sufficiently mixed and uniform. Then, 1 mL of the solution was diluted to 10 mL with 70% oleylamine. The solution was transferred to a three-necked flask, and stirring was performed. Then, 200 uL of n-octyl phosphine was added, and ultrasonic treatment was performed for 30 min. The preparation stage was completed.

[0050] (2) The flask was transferred to a temperature programmed device and washed with N2for 20 min, then temperature programmed. The first stage was to heat from 20 °C to 50 °C at a rate of 10 °C / min, and keep for 30 min. The second stage was to heat from 50 °C to 100 °C at a rate of 20 °C / min, and keep for 30 min. The third stage was to heat from 100 °C to 270 °C at a rate of 15 °C / min, and keep for 60 min. After the temperature programmed process was completed, the sample was naturally cooled to room temperature in the heating jacket. The obtained brown-black sample was NiFeP. Then the sample was washed with ethanol and n-hexane mixed solution with a volume ratio of 5:1 by ultrasonic, and finally centrifuged at a speed of 10000 r / min to complete the washing of NiFeP.

[0051] (3) 1.45 mg of NiFeP was dispersed in 10 ml of n-hexane, and then 5.77 mg of XC-72 was added and ultrasonic was performed for 20 min, followed by the addition of 30 ml of anhydrous ethanol and ultrasonic for 10 min. Finally, centrifugal separation was performed to obtain carbon-loaded NiFeP.

[0052] Figure 1 In order to perform TEM of NiFeP in case 1, it can be seen from the figure that NiFeP is nanospheres with uniform particle size. After statistics, it is known that the average particle size is about 6.5 nm. Uniformly dispersed nanoparticles and nanoscale particle size ensure ultra-high specific surface area and active sites.

[0053] Figure 2 In order to perform dark field TEM of NiFeP in case 1, the box is the scanning area of high-energy X-ray irradiation. From the mapping result on the right, the outlines of elements Ni, Fe and P are obvious, which preliminarily confirms the successful preparation of NiFeP catalyst.

[0054] Figure 3 In order to perform EDX content analysis of NiFeP in case 1, the results show that the surface Ni:Fe:P = 2.4:1:1.1, which is basically consistent with the feeding ratio, indicating that Ni and Fe are fully reduced, and further confirming the successful preparation of the catalyst.

[0055] Figure 4 a and 4b are the lattice spacings of the catalyst in case 1. By measurement, 0.215 nm and 0.227 nm were determined, which are (231) crystal plane in Ni3P and (111) crystal plane in Fe2P, respectively. Then combined with XPS test, it can be seen from the figure that the peaks of Ni-P and Fe-P are obvious, which confirms the successful preparation of NiFeP.

[0056] Figure 5 In order to test the performance of NiFeP in case 1, first Figure 5a is RDE test, from the figure can be seen that compared with commercial Ir02, NiFeP has lower potential, at 10 mA cm -2 is only 1.48 V, lower than 1.58 V of Ir02, NiFeP exhibits OER activity far superior to commercial iridium oxide. Further AEMWE test was carried out, from figure c can be seen that at 60℃, 1A cm -2 The corresponding potential is only 1.71 V, far less than the cell voltage of Ir02(1.97 V), indicating that the activity of NiFeP is superior to Ir02 in AEMWE. Subsequently, large current stability test was carried out, from figure d can be seen that at 1A cm -2 Test for 22h, the potential of NiFeP is always lower than that of Ir02, the attenuation of 22h is about 8%. While the attenuation of Ir02 is 11.5% after 17h, which indicates that the stability of NiFeP is superior to Ir02. Finally, the voltage efficiency of NiFeP and Ir02 was calculated, NiFeP is 81.3%, while Ir02 is 67.3%, indicating that NiFeP has higher hydrogen production efficiency in AEMWE. Further calculation of voltage decay rate, NiFeP is only 0.0018 mV s -1 Far less than the decay rate of Ir02. The experimental results show that NiFeP exhibits excellent activity and stability, and has great potential in the future development of green hydrogen.

[0057] The above examples are only used to illustrate the technical solutions of the present application, but not to limit it; although the present application has been described in detail with reference to the foregoing examples, those skilled in the art should understand that they can still modify the technical solutions recorded in the foregoing examples, or make equivalent replacement for part 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 catalyst for an anion exchange membrane water electrolyzer, characterized in that, Includes the following steps: (1) Preparation of precursor solution: Dissolve Ni salt and Fe salt in oleylamine solution and stir to mix evenly to obtain precursor solution; (2) Add phosphorus source and reducing agent: Add phosphorus source and reducing agent to the precursor solution obtained in step (1), stir and mix evenly to obtain a mixed solution; the phosphorus source and reducing agent is n-octylphosphine; the volume ratio of the phosphorus source and reducing agent to the precursor solution is 180-250:800-1200; (3) Preparation of NiFeP: The mixed solution obtained in step (2) is purged with protective gas to remove impurities; the temperature is adjusted and a heating program is set, the program is run, and the NiFeP catalyst is prepared after the heating process is completed; the heating program is a three-stage heating and temperature control program. In the first stage, the temperature is increased from 20℃ to 50℃ at a heating rate of 8-10℃ / min and held for 20-40min. In the second stage, the temperature is increased from 50℃ to 100℃ at a heating rate of 18-22℃ / min and held for 20-40min. In the third stage, the temperature is increased from 100℃ to 270℃ at a heating rate of 14-16℃ / min and held for 50-70min. After the holding is completed, the temperature is naturally cooled to room temperature.

2. The method for preparing the anode catalyst of the anion exchange membrane water electrolyzer as described in claim 1, characterized in that, In step (1), the Ni salt is nickel acetylacetone and the Fe salt is iron acetylacetone.

3. The method for preparing the anode catalyst of the anion exchange membrane water electrolyzer as described in claim 1, characterized in that, In step (1), the concentration of Ni salt in the precursor solution is 0.01-0.04 mol / L.

4. The method for preparing the anode catalyst of the anion exchange membrane water electrolyzer as described in claim 1, characterized in that, In step (1), the concentration of Fe salt in the precursor solution is 0.01-0.05 mol / L.

5. The method for preparing the anode catalyst of the anion exchange membrane water electrolyzer as described in claim 1, characterized in that, In step (1), the concentration of the oleylamine solution is 70-85 vol.

6. The method for preparing the anode catalyst of the anion exchange membrane water electrolyzer as described in claim 1, characterized in that, In step (3), the protective atmosphere is a high-purity inert gas N2 or Ar.

7. The anode catalyst prepared by the method for preparing the anode catalyst of the anion exchange membrane water electrolyzer according to any one of claims 1-6.

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