Iron phosphide catalyst for separating hydrogen isotopes from PEM electrolyzed water and preparation method of iron phosphide catalyst
By preparing iron phosphide catalyst instead of precious metal platinum carbon catalyst, the problem of low separation factor in PEM electrolyzed water separation of hydrogen isotopes is solved, and efficient and stable hydrogen isotope separation is achieved, which has industrial application value.
Patent Information
- Application Number
- CN202510508486.8
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-04-22
- Publication Date
- 2025-07-25
AI Technical Summary
In the existing PEM electrolytic water separation method, the commonly used cathode catalyst is the precious metal platinum carbon, which has few reserves, is expensive and has a low separation factor.
Iron phosphide catalyst is used to replace the noble metal platinum carbon catalyst. The iron salt and carbon black are mixed and phosphated at high temperature through the preparation method. The iron phosphide catalyst is prepared as a cathode for PEM electrolyzing water to separate hydrogen isotopes.
The hydrogen isotope separation factor is significantly improved to 6 to 8, reducing costs, and the cathode iron phosphide catalyst has high stability, and the stack can operate stably for a long time, which is suitable for industrial applications.
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Figure CN120366829A_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to the technical field of electrocatalysis, and particularly to an iron phosphide catalyst for separating hydrogen isotopes by PEM electrolysis of water and a preparation method thereof. Background Art
[0002] The three isotopes of hydrogen, protium, deuterium, and tritium, have extensive applications in energy, industry, national defense, scientific research, and medical treatment respectively. However, due to the similar physical and chemical properties of hydrogen isotopes, the separation of hydrogen isotopes is a difficult challenge. Currently, no less than dozens of hydrogen isotope separation methods have been reported. For example, cryogenic distillation method, Girdler sulfide method, quantum sieving method, thermal diffusion method, chromatography method, and metal hydride absorption method have been widely studied. However, considering various indicators such as separation scale, separation factor, and separation economy, currently only the Girdler sulfide method and the cryogenic distillation method are applied to industrial-scale separation. However, the Girdler sulfide method not only has a low separation factor, but also requires a very large amount of H2S. Hydrogen sulfide gas is not only toxic but also highly corrosive, so it does not meet the requirements of green environmental protection. The cryogenic distillation method needs to operate under the low-temperature environment required for liquid hydrogen distillation (about 20K). Its separation factor is not only low (about 1.5), but also the lower temperature means greater energy consumption. At the same time, in terms of the composition of the entire device, cryogenic technology must be relied on, combined with distillation equipment and refrigeration cycle equipment, so the technology is complex and the cost is high.
[0003] As a secondary energy source with rich sources, green and low-carbon, and wide applications, hydrogen energy plays an important role in helping China achieve the goals of carbon peak and carbon neutrality. With the development of hydrogen production technology, due to its advantages such as large current density, high hydrogen purity, fast response speed, and safety, PEM electrolysis of water technology has been widely studied, and the separation of hydrogen isotopes by PEM electrolysis of water has once again come into people's view. Although the method of separating hydrogen isotopes by PEM electrolysis of water has the advantages of simple equipment, easy operation, high safety, green environmental protection, mild operating conditions, and large scale potential, currently the commonly used cathode catalyst for PEM electrolysis of water is platinum-carbon catalyst. The precious metal platinum has a small reserve and a high price, and its separation factor in the separation of hydrogen isotopes by PEM electrolysis of water is relatively low, only 3 - 4. Summary of the Invention
[0004] The present invention aims to solve the problems that the commonly used cathode catalyst for PEM electrolysis of water is platinum-carbon catalyst, the precious metal platinum has a small reserve and a high price, and its separation factor in the separation of hydrogen isotopes by PEM electrolysis of water is relatively low, and provides an iron phosphide catalyst for separating hydrogen isotopes by PEM electrolysis of water and a preparation method thereof.
[0005] In order to achieve the above technical objectives, the technical solution provided by the present invention is as follows:
[0006] Application of Iron Phosphide Catalyst in Hydrogen Isotope Separation by PEM Water Electrolysis, wherein the loading amount of the iron phosphide catalyst as the cathode is 0.1 mg / cm 2 ~20 mg / cm 2 .
[0007] The present invention also provides a preparation method of an iron phosphide catalyst, comprising the following steps:
[0008] Step 1: Add iron salt and carbon black into a solvent in a certain proportion for dispersion, and obtain a uniform mixture of iron salt and carbon black after the solvent evaporates;
[0009] Step 2: Heat the mixture obtained in Step 1 at a high temperature and introduce a hydrogen-argon mixed gas to obtain an intermediate product Fe / C;
[0010] Step 3: Perform high-temperature phosphidation of Fe / C and red phosphorus under argon protection to obtain an iron phosphide catalyst.
[0011] Furthermore, in Step 1, the iron salt and carbon black are in a mass ratio of iron element to carbon black of 1:9 to 1:1, preferably 3:7.
[0012] Furthermore, in Step 2, the heating temperature is 300~700 °C and the heating time is 0.5~5 h.
[0013] Furthermore, in Step 3, the temperature is 400~700 °C and the heating time is 0.5~5.
[0014] Furthermore, the mass ratio of Fe / C to red phosphorus is 5:1~1:20.
[0015] The present invention also provides an iron phosphide catalyst prepared according to the above preparation method.
[0016] The present invention also provides a method for separating hydrogen isotopes by PEM water electrolysis, using the prepared iron phosphide catalyst as the cathode catalyst.
[0017] Furthermore, the electrolysis temperature is 5~90 °C and the electrolysis current is 0.1~4 A / cm 2 .
[0018] The present invention has the following beneficial effects:
[0019] 1. The present invention synthesizes a non-noble metal iron phosphide catalyst to replace the traditional noble metal platinum-carbon catalyst, reduces the cost, and significantly improves the hydrogen isotope separation factor to 6~8.
[0020] 2. The cathode iron phosphide catalyst of the present invention has high stability, and its performance hardly decays after a long-term electrolysis reaction. At a current density of 0.5 A / cm 2Under such conditions, the stack can operate stably for about 2,000 hours or more, having high industrial application value. Description of the Drawings
[0021] Figure 1 is the separation factor α of iron phosphide (FeP) and platinum-carbon (Pt / C) catalysts under different temperature conditions;
[0022] Figure 2 is the separation factor α of iron phosphide (FeP) and platinum-carbon (Pt / C) catalysts under different current density conditions;
[0023] Figure 3 is the stability test of iron phosphide catalyst for PEM stack;
[0024] Figure 4 is the XRD pattern of iron phosphide (FeP) catalyst. Detailed Embodiments
[0025] The technical solutions of the present invention will be described clearly and completely below with reference to the accompanying drawings. Apparently, the described embodiments are some but not all of the embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the scope of protection of the present invention.
[0026] In addition, the technical features involved in different embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.
[0027] Glossary:
[0028] Separation factor: It represents the degree of separation of two substances by a certain unit separation operation or a certain separation process, generally denoted by α. In the process of electrolyzing water to separate hydrogen isotopes, its separation factor α is defined as:
[0029]
[0030] In the formula, "gas" is the hydrogen gas evolved, "liq" is the feed water before electrolysis, and [D] and [H] are the atomic fractions of D and H in the feed water and the evolved gas, respectively.
[0031] PEM water electrolysis: PEM is the English abbreviation of Proton Exchange Membrane. PEM water electrolysis is that under a certain voltage, water molecules are first decomposed into oxygen and hydrogen positive ions (H+) under the catalysis of the anode catalyst, and then H + passes through the proton exchange membrane and is catalyzed by the cathode catalyst to generate hydrogen gas. Since the hydrogen gas generated at the cathode and the oxygen gas generated at the anode are separated by the PEM membrane, the hydrogen production purity of this method is relatively high.
[0032] OER: The English abbreviation for Oxygen Evolution Reaction.
[0033] HER: The English abbreviation for Hydrogen Evolution Reaction.
[0034] Example 1
[0035] Preparation of iron phosphide catalyst: First, 3.1 g of iron(III) nitrate nonahydrate and 1 g of carbon black (xc-72) were added to 50 ml of ethanol and dried by rotary evaporation at 60 °C. The dried product was placed in a tube furnace, and 10% H2 / Ar gas was passed through. It was reduced at 350 °C for 2 h to obtain an Fe / C intermediate product. 1 g of red phosphorus and 0.4 g of Fe / C were respectively placed at the front and rear ends of a ceramic boat. The ceramic boat was transferred to the tube furnace, and the gas in the quartz tube was evacuated by a vacuum pump and purged twice with argon to ensure that all the air in the quartz tube was exhausted. At an argon flow rate of 200 sccm, the vacuum tube furnace was heated to 500 °C at a heating rate of 5 °C / min and maintained for 2 h to ensure that the phosphidation reaction proceeded fully. After cooling to room temperature, the reacted sample was collected, washed with water, dried, and ground to obtain iron phosphide.
[0036] Deionized water and isopropanol were mixed at a volume ratio of 1:3, and iron phosphide powder was added. Then, Nafion solution was added until the weight percentage of Nafion to iron phosphide was 30 w%. After ultrasonic dispersion, the cathode solution was prepared.
[0037] Isopropanol and deionized water were mixed at a volume ratio of 1:2, and IrO2 powder was added. Then, Nafion solution was added until the weight percentage of Nafion to IrO2 was 33 w%. After ultrasonic dispersion, the anode solution was prepared.
[0038] The anode solution and the cathode solution were respectively sprayed on both sides of a Nafion 115 proton exchange membrane by an ultrasonic sprayer to obtain a membrane electrode with an IrO2 loading of 1.6 mg / cm 2 and a cathode iron phosphide loading of 2 mg / cm 2 of the membrane electrode.
[0039] Testing: A water isotope with a deuterium content of 0.5% was prepared, and the current of the membrane electrode was controlled at 1 A / cm 2 . After the electrolysis was stable, the hydrogen isotope content was detected, and the separation factor α under different temperature conditions was obtained. As Figure 1 shown, the separation factor of iron phosphide was 6 - 8, significantly higher than that of platinum-carbon catalyst, which was 3 - 4.
[0040] Example 2
[0041] Preparation of Iron Phosphide Catalyst: First, 3.1 g of iron(III) nitrate nonahydrate and 1 g of carbon black (xc-72) were added to 50 ml of ethanol and dried by rotary evaporation at 60 °C. The dried product was placed in a tubular furnace, and a 10% H2 / Ar gas was passed through. It was reduced at 300 °C for 5 h to obtain an Fe / C intermediate product. 1 g of red phosphorus and 0.4 g of Fe / C were respectively placed at the front and rear ends of a ceramic boat. The ceramic boat was transferred to the tubular furnace. The gas in the quartz tube was evacuated by a vacuum pump and purged twice with argon to ensure that all the air in the quartz tube was completely removed. Under an argon flow rate of 200 sccm, the vacuum tubular furnace was heated to 400 °C at a heating rate of 5 °C / min and maintained for 5 h to ensure that the phosphidation reaction proceeded fully. After cooling to room temperature, the reacted sample was collected, washed with water, dried, and ground to obtain iron phosphide.
[0042] Deionized water and isopropanol were mixed at a volume ratio of 1:3 and then added to iron phosphide powder. Then, Nafion solution was added until the weight percentage of Nafion to iron phosphide was 30 w%. After ultrasonic dispersion, a cathode solution was prepared.
[0043] Isopropanol and deionized water were mixed at a volume ratio of 1:2 and then added to IrO2 powder. Then, Nafion solution was added until the weight percentage of Nafion to IrO2 was 33 w%. After ultrasonic dispersion, an anode solution was prepared.
[0044] The anode solution and the cathode solution were respectively sprayed on both sides of a Nafion 115 proton exchange membrane by an ultrasonic sprayer to obtain a membrane electrode with an IrO2 loading of 1.6 mg / cm 2 and a cathode iron phosphide loading of 20 mg / cm 2 of the membrane electrode.
[0045] Testing: A water isotope with a deuterium content of 0.5% was prepared. The current of the membrane electrode was controlled at 1 A / cm 2 . After the electrolysis was stable, the hydrogen isotope content was detected to obtain the separation factor α under different temperature conditions. The separation factor of iron phosphide was 6 - 8, which was significantly higher than that of the platinum-carbon catalyst (3 - 4).
[0046] Example 3
[0047] Preparation of iron phosphide catalyst: First, 3.1 g of iron(III) nitrate nonahydrate and 1 g of carbon black (xc-72) were added to 50 ml of ethanol and dried by rotary evaporation at 60 °C. The dried product was placed in a tubular furnace, and a 10% H2 / Ar gas was passed through. It was reduced at 700 °C for 0.5 h to obtain an Fe / C intermediate product. 1 g of red phosphorus and 0.4 g of Fe / C were respectively placed at the front and rear ends of a ceramic boat. The ceramic boat was transferred to the tubular furnace, and the gas in the quartz tube was evacuated by a vacuum pump and purged twice with argon to ensure that all the air in the quartz tube was exhausted. At an argon flow rate of 200 sccm, the vacuum tubular furnace was heated to 700 °C at a heating rate of 5 °C / min and maintained for 0.5 h to ensure that the phosphidation reaction proceeded fully. After cooling to room temperature, the reacted sample was collected, washed with water, dried, and ground to obtain iron phosphide.
[0048] Deionized water and isopropanol were mixed at a volume ratio of 1:3, and iron phosphide powder was added. Then, Nafion solution was added until the weight percentage of Nafion to iron phosphide was 30 w%. After ultrasonic dispersion, the cathode solution was prepared.
[0049] Isopropanol and deionized water were mixed at a volume ratio of 1:2, and IrO2 powder was added. Then, Nafion solution was added until the weight percentage of Nafion to IrO2 was 33 w%. After ultrasonic dispersion, the anode solution was prepared.
[0050] The anode solution and the cathode solution were respectively sprayed on both sides of a Nafion 115 proton exchange membrane by an ultrasonic spraying machine to obtain a membrane electrode with an IrO2 loading of 1.6 mg / cm 2 and a cathode iron phosphide loading of 0.1 mg / cm 2 of the membrane electrode.
[0051] Testing: A water isotope with a deuterium content of 0.5% was prepared, and the current of the membrane electrode was controlled at 1 A / cm 2 . After the electrolysis was stable, the hydrogen isotope content was detected, and the separation factor α under different temperature conditions was obtained. The separation factor of iron phosphide was 6 - 8, which was significantly higher than that of the platinum-carbon catalyst, which was 3 - 4.
[0052] Example 4:
[0053] The preparation of the iron phosphide catalyst was the same as that in Example 1 and will not be elaborated here.
[0054] Deionized water and isopropanol were mixed at a volume ratio of 1:3, and iron phosphide powder was added. Then, Nafion solution was added until the weight percentage of Nafion to Pt / C was 30 w%. After ultrasonic dispersion, the cathode solution was prepared.
[0055] Isopropanol and deionized water were mixed at a volume ratio of 1:2, and then IrO2 powder was added. Subsequently, Nafion solution was added until the weight percentage of Nafion to IrO2 was 33 w%, and the anolyte was prepared after ultrasonic dispersion.
[0056] The anolyte and the catholyte were respectively sprayed on both sides of a Nafion 115 proton exchange membrane using an ultrasonic spraying machine, and a membrane electrode with an IrO2 loading of 1.6 mg / cm 2 and a FeP loading of 2 mg / cm 2 was obtained.
[0057] Test: Water isotope with a deuterium content of 0.5% was prepared. After the electrolysis was stable, the hydrogen isotope content was detected, and the separation factor α under different current density conditions was obtained. As Figure 2 shown, the separation factor of iron phosphide was 6.4 - 7.5, significantly higher than that of platinum-carbon catalyst (3.8 - 4.2), and the separation factor remained high at high current densities, which was suitable for the application of large-scale hydrogen isotope separation at high current densities.
[0058] Example 5:
[0059] The test conditions were changed to a water bath at 45 °C and a current density of 0.5 A / cm 2 . The remaining steps were the same as those in Example 1. The long-term operation stability of the stack was investigated, and the change in the stack voltage was tested. As Figure 3 shown, the stack maintained a cell voltage of 2.0 V without significant attenuation after stable operation for 1800 hours.
[0060] Example 6:
[0061] The phosphidation temperature was adjusted to 450 °C, and the remaining steps were the same as those in Example 1. The separation factor α was tested and showed no significant change.
[0062] Example 7:
[0063] The iron salt was changed to ferric chloride, and the remaining steps were the same as those in Example 1. The separation factor α was tested and showed no significant change.
[0064] Comparative Example 1
[0065] Deionized water and isopropanol were mixed at a volume ratio of 1:3, and then Pt / C powder was added. Subsequently, Nafion solution was added until the weight percentage of Nafion to Pt / C was 20 w%, and the catholyte was prepared after ultrasonic dispersion.
[0066] Isopropanol and deionized water were mixed at a volume ratio of 1:2, and then IrO2 powder was added. Subsequently, Nafion solution was added until the weight percentage of Nafion to IrO2 was 33 w%, and the anolyte was prepared after ultrasonic dispersion.
[0067] The anolyte and catholyte were respectively sprayed on both sides of a Nafion 115 proton exchange membrane by an ultrasonic spraying machine to obtain a membrane electrode with an IrO₂ loading of 1.6 mg / cm 2 and a Pt loading of 0.5 mg / cm 2 on the cathode side.
[0068] Water isotope with a deuterium content of 1% was prepared, and the current of the membrane electrode was controlled at 1 A / cm 2 . After the electrolysis was stable, the hydrogen isotope content was detected to obtain the separation factor under different temperature conditions, as Figure 1 shown.
[0069] Comparative Example 2
[0070] Isopropanol and deionized water were mixed at a volume ratio of 1:2, and then IrO₂ powder was added. Subsequently, Nafion solution was added until the weight percentage of Nafion to IrO₂ was 33 w%, and the anolyte was prepared after ultrasonic dispersion.
[0071] Deionized water and isopropanol were mixed at a volume ratio of 1:3, and then Pt / C powder was added. Subsequently, Nafion solution was added until the weight percentage of Nafion to Pt / C was 20 w%, and the catholyte was prepared after ultrasonic dispersion.
[0072] The anolyte and catholyte were respectively sprayed on both sides of a Nafion 115 proton exchange membrane by an ultrasonic spraying machine to obtain a membrane electrode with an IrO₂ loading of 1.6 mg / cm 2 and a Pt loading of 0.5 mg / cm 2 on the cathode side.
[0073] Test: Water isotope with a deuterium content of 1% was prepared. After the electrolysis was stable, the hydrogen isotope content was detected to obtain the separation factor α under different current density conditions, as Figure 2 shown.
[0074] As Figure 4 shown is the XRD pattern of the iron phosphide (FeP) catalyst. Its diffraction peaks are consistent with those of FeP (PDF No. 39 - 0809), and the diffraction peak at 23.9° belongs to the C(002) diffraction peak, indicating that the product after phosphidation, the iron phosphide catalyst, is a mixture of FeP and C.
[0075] Although the embodiments of the present invention have been shown and described, it will be understood by those of ordinary skill in the art that various changes, modifications, substitutions, and variations can be made to these embodiments without departing from the principles and spirit of the present invention. The scope of the present invention is defined by the appended claims and their equivalents.
[0076] The above specific embodiments are detailed descriptions of the present invention. It cannot be determined that the specific embodiments of the present invention are only limited to these descriptions. For those of ordinary skill in the technical field to which the present invention pertains, without departing from the concept of the present invention, several simple deductions and substitutions can still be made, and all should be regarded as falling within the protection scope of the present invention.
Claims
1. Application of iron phosphide catalyst in hydrogen isotope separation of PEM electrolyzed water, characterized in that, The loading amount of the iron phosphide catalyst as the cathode is 0.1 mg / cm 2 ~20 mg / cm 2 .
2. A preparation method of an iron phosphide catalyst, characterized in that, It includes the following steps: Step 1: Add iron salt and carbon black into a solvent in a certain proportion for dispersion. After the solvent evaporates, a uniform mixture of iron salt and carbon black is obtained; Step 2: Heat the mixture obtained in Step 1 at a high temperature and introduce a hydrogen-argon mixed gas to obtain an intermediate product Fe / C; Step 3: High-temperature phosphating of Fe / C and red phosphorus under argon protection to obtain an iron phosphide catalyst.
3. The preparation method of an iron phosphide catalyst according to claim 2, characterized in that, In Step 1, the iron salt and carbon black are in a mass ratio of iron element to carbon black of 1:20 to 2:1, preferably 3:
7.
4. The preparation method of an iron phosphide catalyst according to claim 2, wherein, In Step 2, the high-temperature heating temperature is 300-700°C, and the heating time is 0.5-5 h.
5. The preparation method of an iron phosphide catalyst according to claim 2, wherein In Step 3, the high temperature is 400-700°C, the heating time is 0.5-5 h, and the ratio of Fe / C to red phosphorus is 5:1 to 1:
20.
6. The preparation method of an iron phosphide catalyst according to claim 2, characterized in that, In Step 3, the mass ratio of Fe / C to red phosphorus is 5:1 to 1:
20.
7. An iron phosphide catalyst prepared by the preparation method according to any one of claims 2-6.
8. A method for separating hydrogen isotopes by PEM electrolysis of water, characterized in that, Use the iron phosphide catalyst prepared as claimed in claim 7 as the cathode catalyst.
9. The method for separating hydrogen isotopes by PEM electrolyzed water according to claim 8, wherein The electrolysis temperature is 5 to 90 °C, and the electrolysis current is 0.1 to 4 A / cm 2 .