CN116024603A - BiFeO 3 Preparation method and application of perovskite catalytic electrode - Google Patents

Abstract

The invention discloses a preparation method and application of a _BiFeO3 perovskite catalytic electrode. In the present invention, the sol-gel prepared by bismuth nitrate, ferric nitrate, ethylene glycol and citric acid is kept at high temperature to obtain a precursor, and then kept in a muffle furnace and sintered to obtain a _BiFeO3 perovskite catalytic material. Then the BiFeO ₃ perovskite catalytic material is supported on the surface of the hydrophilic carbon cloth to obtain an electrode sheet for the electrocatalytic reduction of nitrate to produce ammonia. By passing a current to the electrode, the morphology of the electrode is regulated to produce a single Bi material, which is then used to electrocatalyze the reduction of nitrate to produce ammonia. In the present invention, current is passed through the electrode so that the morphology of the electrode is regulated. Compared with the electrode without current, the performance of the BiFeO ₃ perovskite catalytic electrode after the configuration is significantly improved. The BiFeO ₃ perovskite catalytic material disclosed by the present invention has excellent catalytic performance and good cycle stability, solves the degradation problem of nitrate pollutants, generates useful ammonia, and plays an important role in the harmlessness and resource utilization of nitrate meaning.

Description

A kind of preparation method and application of BiFeO3 perovskite catalytic electrode

technical field

The invention relates to the technical field of catalytic materials, in particular to a preparation method and application of a _BiFeO3 perovskite catalytic electrode.

Background technique

Ammonia has the characteristics of high hydrogen content, high energy density, easy storage, transportation, and no carbon emissions. It is considered to be a new energy source with long-term large-scale energy storage prospects. Ammonia is also indispensable for agriculture, industry, and medicine. The missing basic chemicals are the key to sustainable production in many industries and have high application value. At present, the synthesis of ammonia is mainly produced through the Haber process. High temperature greater than 450°C, high pressure of 150-350 atm, and large-scale and centralized infrastructure are necessary conditions for the Haber process. The Haber process is an energy-intensive process that will consume global 2% of annual energy supply. In addition, the Haber process utilizes hydrogen derived from fossil fuels, which will generate 400 million tons of carbon dioxide per year, accounting for 1.2% of global annual carbon emissions. Similar to hydrogen and hydrocarbon derivatives such as methanol, ammonia can likewise be converted and produced using renewable energy. At present, people are committed to exploring some renewable energy-generated electricity to achieve ammonia synthesis routes, including: (1) electrochemical technology to reduce nitrogen to ammonia; (2) plasma-driven synthesis of nitrogen and hydrogen to ammonia; (3) ) electrocatalytic conversion of nitrogen oxides to ammonia. At the same time, compared with high-cost process technologies such as compressed hydrogen, hydrogen liquefaction and storage, electrocatalytic ammonia synthesis using sustainable energy supply is quite attractive. Nitrate ions are theoretically more reactive than nitrogen, and the dissociation energy of the N=O bond is 204kJ·mol ^-1 , and the dissociation energy of N≡N is 941kJ·mol ^-1 , because the N=O bond The dissociation energy is much lower than that of N≡N, and the reduction reaction of nitrate to ammonia is not limited by the low solubility of nitrogen in water environment, which is more thermodynamically favorable. Therefore, nitrate reduction to ammonia is a practical alternative route for nitrogen reduction.

Electrocatalysts are the key to electrochemical reduction reactions, and the development of high-performance and high-stability catalysts that can achieve nitrate degradation and product selectivity control is an urgent problem to be solved. Transition metal compounds, including transition metal oxides, nitrides, sulfides, etc., are expected to replace the current commercial noble metal catalysts due to their wide source, low price, and good electrocatalytic ability, and have great application value in the future. Among them, taking the perovskite material as an example, it has tunable metal elements, chemical composition, stable and reliable structural framework, adjustable catalytic activity, and a wide range of applications. However, in the field of electrocatalysis, perovskite materials often have problems such as insufficient electrocatalytic activity, ammonia nitrogen selectivity, and insufficient current efficiency, which lead to limited catalytic performance and application prospects.

The invention of "A Preparation Method and Application of Strontium-Based Perovskite Catalytic Cathode" involves the preparation of inorganic perovskite and its application in nitrate. However, the activity of inorganic perovskite is not high enough, and in situ on porous Ti To generate perovskite powder, the invention is cumbersome and complicated to operate, which limits its catalytic application.

In order to solve the above problems, the present invention provides a preparation method and application of a _BiFeO3 perovskite catalytic electrode.

Contents of the invention

The object of the present invention is to provide a preparation method of a BiFeO ₃ perovskite catalytic electrode and its application, so as to solve the problems raised in the above-mentioned background technology.

In order to solve the above technical problems, the present invention provides the following technical solutions:

A kind of preparation method of BiFeO ₃ perovskite catalytic electrode, comprises the following steps:

Step 1: adding bismuth nitrate, ferric nitrate, and citric acid into the ethylene glycol solution, stirring evenly to obtain a mixed solution; heating the mixed solution, drying the water in it, and obtaining a dried sol-gel;

Step 2: Sintering the dried sol-gel to obtain the dried BiFeO ₃ perovskite catalytic material;

Step 3: Take the dried BiFeO ₃ perovskite catalytic material, ethanol, and Nafion binder solution, and mix them evenly to obtain a catalyst slurry; coat the catalyst slurry on one side of the conductive substrate, and dry to obtain BiFeO ₃ perovskite mine catalytic electrode.

More optimally, the BiFeO ₃ perovskite catalytic electrode is subjected to morphology regulation and control, and the morphology regulation adopts a three-electrode system, selects a platinum sheet as a counter electrode, and Ag/AgCl as a reference electrode, and performs an electrocatalytic test; The electrolyte uses 50mM Na ₂ SO ₄ , the concentration of NO ₃ ^- is 0.1mol/L, and the catalytic electrode is fed with a current of 15-20mA/cm ² for 8-12h, and the voltage range is 1.1-1.4V to obtain BiFeO ₃ calcium Titanium ore catalytic electrode.

More optimally, in step 1, the molar ratio of raw material metal ion: ethylene glycol: citric acid is 80:4:1, and the molar ratio of Bi:Fe in the metal ion is 1:1.

More optimally, in step 1, add bismuth nitrate, ferric nitrate, and citric acid into the ethylene glycol solution, stir evenly, and obtain a mixed solution; keep the mixed solution at 80-90° C. for 10-12 hours, and continue at 120 ℃ for 10-12 hours to obtain dried sol-gel.

More optimally, in step 2, heat the dried sol-gel at 300-330°C for 2-3 hours, raise the temperature to 700-720°C, continue to keep warm for 3-4h, and control the heating rate to 5°C/min to obtain _BiFeO3 perovskite catalytic material after drying.

More optimally, in step 3, the conductive substrate is hydrophilic carbon cloth, and the preparation method of the hydrophilic carbon cloth is: take the carbon cloth, add concentrated sulfuric acid, concentrated nitric acid, and deionized water to treat for 6-8 hours; The mass ratio of concentrated sulfuric acid: concentrated nitric acid: deionized water is 1:1:1.

More optimally, the loading amount of the catalyst slurry on the conductive substrate is 2.5-4.5 mg/cm ² .

The invention discloses a _BiFeO3 perovskite catalytic electrode prepared by a method for preparing a _BiFeO3 perovskite catalytic electrode.

An application of a BiFeO ₃ perovskite catalytic electrode, the BiFeO ₃ perovskite catalytic electrode is applied to electrocatalyze the reduction of nitrate to produce ammonia.

More optimally, the step of electrocatalyzing the reduction of nitrate to produce ammonia is as follows: connect the working electrode to the _BiFeO3 perovskite catalytic electrode, use platinum as the counter electrode, silver chloride as the reference electrode, and use nitrate as the raw material , the electrolysis time is 20-30min to obtain ammonia.

Compared with the prior art, the beneficial effects achieved by the present invention are:

(1) The primary purpose of the present invention is to provide the preparation of the BiFeO ₃ perovskite catalytic material electrode and change its morphology and structure through potential driving to improve the electrocatalytic performance. Another object of the present invention is to provide the application of the BiFeO ₃ perovskite catalytic material electrode based on the above reaction in the electrocatalytic reduction of nitrate to ammonia production. Compared with the existing reports on the reduction of nitrate to produce ammonia, the electrode material prepared by the present invention can realize the efficient reduction of nitrate to produce ammonia after the reconstruction of the morphology and structure, and the rate of ammonia production is higher than that of most reported As a result of the research, it also has good cycle stability.

The invention prepares the sol-gel prepared from bismuth nitrate, ferric nitrate, ethylene glycol and citric acid, heat-preserves and sinters to obtain the _BiFeO3 perovskite catalytic material. Then the BiFeO ₃ perovskite catalytic material is loaded on the surface of the hydrophilic carbon cloth treated with an acid solution. Since the catalytic slurry will pass through the surface of the carbon cloth, the BiFeO ₃ perovskite catalytic material is coated on one side of the conductive substrate. , the electrode sheet used for the electrocatalytic reduction of nitrate to produce ammonia can be obtained.

Since the morphology regulation of the surface of the material is mainly affected by the voltage, by passing a current to the electrode and controlling the voltage range of 1.1-1.4V at the same time, the electrode morphology can be regulated to produce a simple Bi material, which can be used for electrocatalytic nitrate recovery. Native ammonia. The electrode prepared by the BiFeO ₃ perovskite catalytic material disclosed in the invention has extremely high activity of electrocatalyzing the reduction of nitrate to produce ammonia and cycle stability. The BiFeO ₃ perovskite catalytic material of the present invention improves electrocatalytic performance based on morphology control under cathode reduction, has high nitrate removal efficiency and ammonia production rate, and is of great significance to the harmlessness and resource utilization of nitrate.

In the present invention, current is passed through the electrode so that the morphology of the electrode is regulated. Compared with the electrode without current, the performance of the BiFeO ₃ perovskite catalytic electrode after the configuration is significantly improved. The _BiFeO3 perovskite catalytic material disclosed by the invention has excellent catalytic performance and good cycle stability. It not only solves the problem of degradation of nitrate pollutants, but also generates ammonia with value for use. It provides an extremely effective reference for future energy recycling, and has a good prospect in practical applications.

Description of drawings

The accompanying drawings are used to provide a further understanding of the present invention, and constitute a part of the description, and are used together with the embodiments of the present invention to explain the present invention, and do not constitute a limitation to the present invention. In the attached picture:

Fig. 1 is the XRD figure of the _BiFeO3 perovskite catalytic material of the embodiment of the present invention;

Fig. 2 is the SEM figure of the _BiFeO3 perovskite catalytic material of the embodiment of the present invention;

Fig. 3 is the SEM picture of the _BiFeO3 perovskite catalytic material of the embodiment of the present invention after the morphology regulation;

Fig. 4 is an effect diagram of ammonia production in the process of controlling the electrode morphology of the _BiFeO3 perovskite material electrode at a constant current of 15mA/ ^cm in Example 5 of the present invention;

Fig. 5 is a comparison chart of ammonia nitrogen yields before and after adjusting the electrode morphology of the BiFeO ₃ perovskite material in the sixth embodiment of the present invention under the constant current mode.

Detailed ways

The following will clearly and completely describe the technical solutions in the embodiments of the present invention with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only some, not all, embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by persons of ordinary skill in the art without making creative efforts belong to the protection scope of the present invention.

Embodiment 1: The preparation of BiFeO ₃ perovskite catalytic material electrode, concrete steps are as follows:

Step 1: Add 3.02g of bismuth nitrate, 2.273g of iron nitrate, and 5.25g of citric acid into 30.58mL of ethylene glycol solution, stir evenly, and incubate in an oven at 80°C and 120°C for 10 hours respectively to obtain a precursor.

Step 2: Put the precursor in a porcelain boat, heat it in a muffle furnace at 300°C for 2 hours and 700°C for 3 hours, control the temperature rise rate of the muffle furnace at 5°C/min, and obtain the dried BiFeO ₃ calcium Titanium catalyst material.

Step 3: Take the dried BiFeO ₃ perovskite catalytic material, 0.9mL of ethanol, and 100 microliters of Nafion binder solution (act as a binder, a commercially available product, the manufacturer is DuPont) and mix to obtain Catalyst slurry; The catalyst slurry is brushed on one side of the hydrophilic carbon cloth (manufacturer is Taiwan Carbon Energy Technology Co., Ltd.) that is 1.5cm * 1.0cm after the acidification treatment; The carbon cloth after brushing is at 27 °C for 3 hours to obtain a _BiFeO3 perovskite catalytic material electrode.

The preparation method of the hydrophilic carbon cloth is as follows: take the carbon cloth, add concentrated sulfuric acid, concentrated nitric acid, and deionized water to treat for 6-8 hours; the mass ratio of the concentrated sulfuric acid: concentrated nitric acid: deionized water is 1:1: 1.

The BiFeO ₃ perovskite catalytic material electrode is an electrode for electrocatalytic reduction of nitrate to produce ammonia, and the loading capacity of the catalyst slurry on the hydrophilic carbon cloth is 2.5 mg/cm ² .

Embodiment two: the preparation of BiFeO ₃ perovskite catalytic material electrode, concrete steps are as follows:

Step 1: Add 3.02g of bismuth nitrate, 2.273g of iron nitrate, and 5.25g of citric acid into 30.58mL of ethylene glycol solution, stir evenly, and incubate in an oven at 80°C and 120°C for 10 hours respectively to obtain a precursor.

Step 2: Put the precursor in a porcelain boat, heat it in a muffle furnace at 300°C for 2 hours and 700°C for 3 hours, control the temperature rise rate of the muffle furnace at 5°C/min, and obtain the dried BiFeO ₃ calcium Titanium catalyst material.

Step 3: Weigh the dried BiFeO ₃ perovskite catalytic material, 0.9mL of ethanol, and 100 microliters of Nafion binder solution and mix to obtain a catalyst slurry; brush the catalyst slurry on a piece of acidification treatment, and the size is 1.5 cm×1.0cm hydrophilic carbon cloth; the carbon cloth after brushing was dried at 25°C for 3 hours to obtain BiFeO ₃ perovskite catalytic material electrode.

The preparation method of the hydrophilic carbon cloth is as follows: take the carbon cloth, add concentrated sulfuric acid, concentrated nitric acid, and deionized water to treat for 6-8 hours; the mass ratio of the concentrated sulfuric acid: concentrated nitric acid: deionized water is 1:1: 1.

The BiFeO ₃ perovskite catalytic material electrode is an electrode for electrocatalytic reduction of nitrate to produce ammonia, and the loading capacity of the catalyst slurry on the hydrophilic carbon cloth is 3 mg/cm ² .

Embodiment three: the preparation of BiFeO ₃ perovskite catalytic material electrode, concrete steps are as follows:

Step 1: Add 3.02g of bismuth nitrate, 2.273g of iron nitrate, and 5.25g of citric acid into 30.58mL of ethylene glycol solution, stir evenly, and incubate in an oven at 80°C and 120°C for 10 hours respectively to obtain a precursor.

Step 2: Put the precursor in a porcelain boat, heat it in a muffle furnace at 300°C for 2 hours and 700°C for 3 hours, control the temperature rise rate of the muffle furnace at 5°C/min, and obtain the dried BiFeO ₃ calcium Titanium catalyst material.

Step 3: Weigh the dried BiFeO ₃ perovskite catalytic material, 0.9 mL of ethanol, and 100 microliters of Nafion binder solution, and mix them evenly to obtain a catalyst slurry; brush the catalyst slurry on a piece of acidified On a hydrophilic carbon cloth of 1.5cm×1.0cm; the carbon cloth after brushing was dried at 30°C for 3 hours to obtain a BiFeO ₃ perovskite catalytic material electrode.

The preparation method of the hydrophilic carbon cloth is as follows: take the carbon cloth, add concentrated sulfuric acid, concentrated nitric acid, and deionized water to treat for 6-8 hours; the mass ratio of the concentrated sulfuric acid: concentrated nitric acid: deionized water is 1:1: 1.

The BiFeO ₃ perovskite catalytic material electrode is an electrode for electrocatalytic reduction of nitrate to produce ammonia, and the loading capacity of the catalyst slurry on the hydrophilic carbon cloth is 3.5 mg/cm ² .

Embodiment four: the preparation of BiFeO ₃ perovskite catalytic material electrode, concrete steps are as follows:

Step 1: Add 3.02g of bismuth nitrate, 2.273g of ferric nitrate, and 5.25g of citric acid into 30.58mL of ethylene glycol solution and stir evenly, and keep warm in an oven at 80°C and 120°C for 10 hours respectively to obtain the precursor.

Step 2: Put the precursor in a porcelain boat, heat it in a muffle furnace at 300°C for 2 hours and 700°C for 3 hours, control the temperature rise rate of the muffle furnace at 5°C/min, and obtain the dried BiFeO ₃ calcium Titanium catalyst material.

Step 3: Weigh the dried BiFeO ₃ perovskite catalytic material, 0.9mL of ethanol, and 100 microliters of Nafion binder solution and mix to obtain a catalyst slurry; brush the catalyst slurry on a piece of acidification treatment, and the size is 1.5 cm×1.0cm hydrophilic carbon cloth; the brushed carbon cloth was dried at 30°C for 3 hours to obtain a BiFeO ₃ perovskite catalytic material electrode.

The preparation method of the hydrophilic carbon cloth is as follows: take the carbon cloth, add concentrated sulfuric acid, concentrated nitric acid, and deionized water to treat for 6-8 hours; the mass ratio of the concentrated sulfuric acid: concentrated nitric acid: deionized water is 1:1: 1.

The BiFeO ₃ perovskite catalytic material electrode is an electrode for electrocatalytic reduction of nitrate to produce ammonia, and the loading capacity of the catalyst slurry on the hydrophilic carbon cloth is 4.5 mg/cm ² .

Embodiment five: electrification is carried out to regulate and control BiFeO ₃ Morphological structure, specific steps are as follows:

Morphology control is achieved by connecting the catalytic material on the electrode to the voltage of the negative electrode. The specific operation is: connect the BiFeO ₃ perovskite catalytic material electrode prepared in Example 3 to a constant current of 15 mA/cm ² , corresponding to a constant voltage of 1.4V, the morphology is controlled, and the solution system is 50mM Na ₂ SO ₄ and 10mM NO ₃ ^- , and every hour is a cycle. The effect of reducing nitrate to produce ammonia is shown in Figure 4.

Conclusion: Figure 4 is the effect diagram of ammonia production during the process of adjusting the electrode morphology of the BiFeO ₃ perovskite material under constant current 15mA/cm ² in Example 5. It can be found from the figure that the performance of ammonia production has been occurring in the first 8 hours change, the selectivity is steadily improving, and the current efficiency has also increased significantly in the first 5 hours. In addition, the figure shows that after 15 cycles of testing, the catalyst can still show excellent ammonia production rate and ammonia production Faraday The efficiency proves that the catalyst can work stably for a long time and efficiently reduce nitrate to produce ammonia. From the XRD patterns before and after the reaction and the SEM images before and after the reaction, it is found that the specific surface area of the electrode becomes larger after the regulation, and a new substance of Bi is produced.

Embodiment six:

The BiFeO ₃ perovskite catalytic material electrode prepared in Example ³ was tested _by an electrochemical workstation. The catalytic material electrode is connected to the negative electrode of the voltmeter, the platinum plate is used as the counter electrode to connect the positive electrode, the silver chloride is used as the reference electrode, and the electrolytic cell is an H-type electrolytic cell. After the assembly is completed, use 50mM Na ₂ SO ₄ , NO ₃ ^- at a concentration of 0.1mol/L as the electrolyte, and the electrolysis time is 20 minutes. The performance of electrocatalytic reduction of nitrate to ammonia before and after morphology control was compared.

Conclusion: Figure 5 is a comparison chart of the ammonia nitrogen yield before and after the BiFeO ₃ perovskite material electrode morphology is adjusted in the constant current mode. It can be found that the performance of the electrode after reconstruction is significantly improved compared with that of the electrode without reconstruction. The _BiFeO3 perovskite catalytic material disclosed by the invention has excellent catalytic performance and good cycle stability. It not only solves the degradation problem of nitrate pollutants, but also generates valuable ammonia, which provides an extremely effective reference for future energy recycling and has a good prospect in practical application.

Finally, it should be noted that: the above is only a preferred embodiment of the present invention, and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, for those skilled in the art, it still The technical solutions recorded in the foregoing embodiments may be modified, or some technical features thereof may be equivalently replaced. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention shall be included within the protection scope of the present invention.

Claims (10)

1. BiFeO ₃ The preparation method of the perovskite catalytic electrode is characterized by comprising the following steps of: the method comprises the following steps:

step one: adding bismuth nitrate, ferric nitrate and citric acid into the glycol solution, and uniformly stirring to obtain a mixed solution; heating the mixed solution, and drying the water in the mixed solution to obtain dried sol-gel;

step two: sintering the dried sol gel to obtain dried BiFeO ₃ A perovskite catalytic material;

step three: taking dried BiFeO ₃ Uniformly mixing perovskite catalytic material, ethanol and Nafion binder solution to obtain catalyst slurry; coating the catalyst slurry on one surface of a conductive substrate, and drying to obtain BiFeO ₃ Perovskite catalytic electrodes.

2. A BiFeO according to claim 1 ₃ The preparation method of the perovskite catalytic electrode is characterized by comprising the following steps of: the BiFeO ₃ The perovskite catalytic electrode is subjected to morphology regulation treatment, a three-electrode system is adopted for morphology regulation, a platinum sheet is selected as a counter electrode, ag/AgCl is selected as a reference electrode, and 50mM Na is adopted as electrolyte ₂ SO ₄ And 10mM NO ₃ ^- Introducing the catalytic electrode into the reactor at a concentration of 15-20mA/cm ² The current of (2) is 8-12h, and the voltage is 1.1-1.4V.

3. A BiFeO according to claim 1 ₃ The preparation method of the perovskite catalytic electrode is characterized by comprising the following steps of: in the first step, raw material metal ions: ethylene glycol: the molar ratio of citric acid is 80:4:1, and Bi in metal ions: the molar ratio of Fe is 1:1.

4. a BiFeO according to claim 1 ₃ The preparation method of the perovskite catalytic electrode is characterized by comprising the following steps of: adding bismuth nitrate, ferric nitrate and citric acid into an ethylene glycol solution, and uniformly stirring to obtain a mixed solution; and (3) preserving the temperature of the mixed solution at 80-90 ℃ for 10-12 hours, and preserving the temperature of the mixed solution at 120 ℃ for 10-12 hours to obtain the dried sol-gel.

5. A BiFeO according to claim 1 ₃ The preparation method of the perovskite catalytic electrode is characterized by comprising the following steps of: in the second step, the dried sol-gel is kept at 300-330 ℃ for 2-3 hours, the temperature is raised to 700-720 ℃, the heat preservation is continued for 3-4 hours, and the temperature raising rate is controlled to be 5 ℃/min, so as to obtain the dried BiFeO ₃ Perovskite catalytic material.

6. A BiFeO according to claim 1 ₃ The preparation method of the perovskite catalytic electrode is characterized by comprising the following steps of: in the third step, the conductive substrate is hydrophilic carbon cloth, and the preparation method of the hydrophilic carbon cloth comprises the following steps: adding concentrated sulfuric acid, concentrated nitric acid and deionized water into carbon cloth for treatment for 6-8 hours; the concentrated sulfuric acid: concentrated nitric acid: the mass ratio of deionized water is 1:1:1.

7. a BiFeO according to claim 1 ₃ The preparation method of the perovskite catalytic electrode is characterized by comprising the following steps of: the loading of the catalyst slurry on the conductive substrate is 2.5-4.5mg/cm ² 。

8. A BiFeO according to any one of claims 1-7 ₃ BiFeO prepared by perovskite catalytic electrode preparation method ₃ Perovskite catalytic electrodes.

9. A BiFeO according to claim 8 ₃ The application of the perovskite catalytic electrode is characterized in that: the BiFeO ₃ Perovskite catalytic electrodes are used to electro-catalyze nitrate reduction to produce ammonia.

10. A BiFeO according to claim 9 ₃ The application of the perovskite catalytic electrode is characterized in that: the electrocatalytic nitrate reduction ammonia production comprises the following steps: combining working electrode with BiFeO ₃ The perovskite catalytic electrode is connected, a platinum sheet counter electrode and silver chloride are used as reference electrodes, nitrate is used as raw material, and the electrolysis time is 20-30min, so as to obtain ammonia.

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