Low-cost alkaline medium oxygen evolution catalyst as well as preparation method and application thereof

Abstract

The invention discloses a low-cost alkaline medium oxygen evolution catalyst as well as a preparation method and application thereof, and relates to the technical field of electrochemistry. The preparation method comprises the following steps: step 1, mixing an iron metal source and a cobalt metal source, and preparing a salt solution A with a certain concentration; step 2, washing foamed nickel or a nickel metal source with concentrated hydrochloric acid and deionized water, drying, placing in the salt solution A, and standing for a certain time after ultrasonic treatment; step 3, preparing an alkali solution B with a certain concentration from an alkali solution source; slowly dropwise adding the alkali solution B into the salt solution A to precipitate metal ions; and step 4, taking out the foamed nickel or the nickel metal source in the solution, washing with deionized water and absolute ethyl alcohol, and drying to prepare the oxygen evolution catalyst. The oxygen evolution catalyst disclosed by the invention can be used for preparing a self-supporting OER electrode for catalyzing oxygen evolution, and has the advantages of low cost, high catalytic activity, capability of realizing large-scale production, relatively low environmental influence and the like.

Description

Technical Field

[0001] The invention relates to the field of electrochemical technology, and in particular to a low-cost alkaline medium oxygen evolution catalyst and a preparation method and application thereof. Background Art

[0002] Hydrogen can be synthesized in a variety of ways because of its high calorific value. At present, the main hydrogen production process is to produce hydrogen by methane cracking or water electrolysis. Among them, when methane cracking is used to produce hydrogen, on the one hand, the raw material of this method is fossil fuel, which is a non-renewable synthesis method; on the other hand, this method produces a large amount of carbon dioxide, which does not conform to the concept of clean and pollution-free. Hydrogen production by water electrolysis is an efficient, green and pollution-free hydrogen production method, which has the advantages of high hydrogen purity (hydrogen purity>99%), large-scale industrial production of hydrogen, and relatively simple process. In the process of hydrogen production by water electrolysis, there are two half reactions: oxygen evolution reaction (OER) and hydrogen evolution reaction (HER). Compared with the simple two-electron reaction of hydrogen evolution reaction, oxygen evolution reaction is a four-electron complex reaction with a relatively higher energy barrier. The activity of OER catalyst determines the efficiency and power of water electrolysis. Precious metal catalysts are often used as OER catalysts because of their high catalytic activity and stable properties, but their scarce reserves and high prices limit their application as catalysts for large-scale electrolyzers.

[0003] Transition metals (Ni, Fe, Mn, Co, etc.) have good catalytic activity as OER catalysts due to their unique valence band structure, and their reserves are relatively high, the cost is low, and the stability is good. They are expected to become OER catalysts for large-scale water electrolysis to produce hydrogen in the future. At present, self-supporting electrodes based on nickel foam have light weight, high mechanical strength, good chemical stability, high porosity, large specific surface area and good electrical conductivity, which has attracted great attention. However, the existing self-supporting electrode synthesis and preparation processes mostly use hydrothermal methods, high-temperature calcination and other methods. The synthesis conditions are relatively harsh, making it difficult to use it as an efficient, large-scale industrial production method.

[0004] Therefore, technicians in this field are committed to developing a non-precious metal catalyst with low cost, high catalytic activity and large-scale production to replace the existing precious metal catalyst. Summary of the invention

[0005] In view of the above-mentioned defects of the prior art, the technical problem to be solved by the present invention is to develop a non-precious metal catalyst with low cost, high catalytic activity and large-scale production capability to replace the existing precious metal catalyst.

[0006] To achieve the above object, the present invention provides a method for preparing a low-cost alkaline medium oxygen evolution catalyst, comprising the following steps:

[0007] Step 1, mixing an iron metal source and a cobalt metal source, and preparing a salt solution A of a certain concentration;

[0008] Step 2, washing the nickel foam or nickel metal source with concentrated hydrochloric acid and deionized water and drying, placing it in salt solution A, and standing it for a certain period of time after ultrasonic treatment;

[0009] Step 3, preparing an alkaline solution source into an alkaline solution B of a certain concentration; slowly adding the alkaline solution B dropwise into the salt solution A to precipitate the metal ions;

[0010] Step 4: taking out the nickel foam or nickel metal source from the solution, washing it with deionized water and anhydrous ethanol and drying it to prepare an oxygen evolution catalyst.

[0011] In a preferred embodiment of the present invention, in step 1, the iron metal source is selected from one or more of anhydrous ferric acetate, ferric acetate hydrate, anhydrous ferric chloride, ferric chloride hydrate, anhydrous ferric nitrate, ferric nitrate hydrate, anhydrous ferric sulfate, and ferric sulfate hydrate; the cobalt metal source is selected from one or more of anhydrous cobalt acetate, cobalt acetate hydrate, anhydrous cobalt chloride, cobalt chloride hydrate, anhydrous cobalt nitrate, cobalt nitrate hydrate, anhydrous cobalt sulfate, and cobalt sulfate hydrate.

[0012] In a preferred embodiment of the present invention, in step 2, the nickel metal source is selected from one or more of nickel nitrate, nickel nitrate hydrate, nickel chloride, nickel chloride hydrate, nickel acetate, and nickel acetate hydrate.

[0013] In a preferred embodiment of the present invention, the alkaline solution source is selected from one or more of potassium hydroxide, sodium hydroxide, ammonia potassium carbonate, sodium carbonate, and ammonium carbonate.

[0014] In a preferred embodiment of the present invention, in step 1, the molar concentration of iron element in the salt solution A is twice that of cobalt element.

[0015] Further, in step 1, the molar concentration of iron in the salt solution A is 0.1 mol / L, and the molar concentration of cobalt is 0.05 mol / L; in step 2, the molar concentration of OH in the alkaline solution B is 0.1 mol / L. - Concentration range: 0.5mol / L.

[0016] In a preferred embodiment of the present invention, in step 2, the ultrasonic time is 10 minutes, the ultrasonic temperature is 25-100° C., and the standing time is 8 hours.

[0017] In a preferred embodiment of the present invention, in step 2 and step 4, the drying is carried out by vacuum drying, and the vacuum drying temperature is 60-80° C., and the drying time is 12-24 hours.

[0018] The invention also discloses an oxygen evolution catalyst prepared by the preparation method.

[0019] The present invention also discloses an application of the oxygen evolution catalyst as described above in the preparation of a self-supporting OER electrode for catalytic oxygen evolution.

[0020] Compared with the prior art, the present invention has the following beneficial effects:

[0021] 1. The present invention provides a low-cost alkaline medium oxygen evolution catalyst, which can be used as an OER catalyst in the water decomposition process and can achieve an electrocatalytic reaction with high Faraday efficiency. Its XRD spectrum shows that the surface deposited powder is Fe3O4 and CoFe2O 4， Its size is nanoparticles, with uniform size and good dispersion. The iron and cobalt elements help to enhance the catalytic activity of the nickel foam itself.

[0022] 2. The catalyst preparation process of the present invention is simple, the conditions are mild, it has strong repeatability, and it has good catalytic performance under alkaline conditions, and is expected to be widely used in the field of anion exchange membrane water electrolysis hydrogen production;

[0023] 3. Among the raw materials of the oxygen evolution catalyst of the present invention, the mixed oxide of iron (Fe), nickel (Ni), and cobalt (Co) is one of the most effective mixed transition metal oxides, among which the iron element has low cost and high reserves, and the combination of Fe and Ni elements can optimize the electronic structure of Ni elements, thereby significantly improving its electrochemical activity. Compared with other catalysts, the oxide has strong stability and can improve its tolerance under alkaline conditions. It is applied to the self-supporting OER electrode, which can be suitable for electrolysis of water in an alkaline environment and has good catalytic activity, because iron enhances the catalytic activity of nickel foam, and it also has high conductivity and low Tafel slope, has low cost advantages, and has certain market competitiveness;

[0024] 4. The present invention studies the oxygen evolution catalyst (OER) in alkaline medium, and also has significant technical advances in the following aspects:

[0025] (1) High activity and low overpotential: The self-supporting OER electrode exhibits high activity in the OER reaction, which is manifested by a low overpotential (e.g., the overpotential to reach a current density of 100 mA / cm2 in 1 M KOH is 227 mV), which is one of the key parameters for measuring catalyst efficiency. A lower overpotential means that in practical applications, such as water electrolysis, less additional energy is required;

[0026] (2) Stability: Stability is a key indicator of OER catalysts under alkaline conditions. The nickel foam substrate of the self-supporting OER electrode provides good chemical stability and durability, making it suitable for long-term, high-potential electrolysis processes;

[0027] (3) Low cost: Traditional OER catalysts, especially those based on precious metals such as platinum and iridium, have high performance but are relatively expensive. Self-supporting OER electrode synthesis uses relatively low-cost raw materials and is prepared by a simple deposition method, thereby reducing the overall cost.

[0028] (4) Easy to scale up: The synthesis process involves common chemicals and standard chemical processing steps, and the synthesis steps are simple, which facilitates the large-scale production of the catalyst;

[0029] (5) Environmentally friendly: The inorganic metal salts and alkaline solutions used in the synthesis process have lower environmental impact compared to many organic solvents.

[0030] The concept, specific structure and technical effects of the present invention will be further described below in conjunction with the accompanying drawings to fully understand the purpose, characteristics and effects of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 This is the XRD pattern of the oxygen evolution catalyst prepared in the embodiment of the present invention;

[0032] Figure 2 This is a scanning electron microscope (SEM) image of the oxygen evolution catalyst prepared in an embodiment of the present invention;

[0033] Figure 3 This is an energy dispersive spectrum analysis (EDS) image of the oxygen evolution catalyst prepared in an embodiment of the present invention;

[0034] Figure 4 This is a linear voltammetric sweep curve (LSV) graph obtained by evaluating the oxygen evolution catalyst prepared in an embodiment of the present invention as a self-supporting OER electrode in a 1 M KOH solution using a three-electrode battery system. DETAILED DESCRIPTION

[0035] The following describes several preferred embodiments of the present invention with reference to the drawings in the specification, so that the technical content is clearer and easier to understand. The present invention can be embodied in many different forms of embodiments, and the protection scope of the present invention is not limited to the embodiments mentioned in the text.

[0036] In the drawings, components with the same structure are indicated by the same numerical reference numerals, and components with similar structures or functions are indicated by similar numerical reference numerals. The size and thickness of each component shown in the drawings are arbitrarily shown, and the present invention does not limit the size and thickness of each component. In order to make the illustration clearer, the thickness of the components is appropriately exaggerated in some places in the drawings.

[0037] Example 1

[0038] Objective: To synthesize a self-supporting OER electrode with an area of ​​4cm*4cm.

[0039] Raw materials: 4cm*4cm nickel foam, 6.06g iron nitrate nonahydrate, 0.873g cobalt nitrate hexahydrate, appropriate amount of potassium hydroxide, concentrated hydrochloric acid, deionized water, and anhydrous ethanol.

[0040] Synthesis steps

[0041] 1. Take 150 ml of deionized water and pour it into beaker A. Weigh 6.06 g of iron nitrate nonahydrate and 0.873 g of cobalt nitrate hexahydrate. Stir them under magnetic stirring for 30 min to mix them evenly to obtain a 0.1 M Fe(NO3)3, 0.05 M Co(NO3)2 mixed salt solution A.

[0042] 2. Put the nickel foam into a beaker, add an appropriate amount of concentrated hydrochloric acid, and clean it by ultrasonic for 10 minutes; then add an appropriate amount of deionized water, and clean it by ultrasonic for 10 minutes. Repeat the deionized water cleaning step 3 times, and then vacuum dry it at 60°C for 12 hours;

[0043] 3. Place the nickel foam in salt solution A, ultrasonicate for 10 minutes, and then let it stand for 8 hours;

[0044] 4. Prepare 200 ml of 0.5 M KOH solution B;

[0045] 5. Slowly add the prepared solution B into the salt solution A to precipitate the metal ions;

[0046] 6. After the addition of solution B is completed, the nickel foam is taken out, washed three times with deionized water, and then washed three times with anhydrous ethanol, and then vacuum dried at 60°C for 24 hours to prepare an oxygen evolution catalyst.

[0047] Used as a self-supporting OER electrode.

[0048] Example 2

[0049] Objective: To synthesize a self-supporting OER electrode with an area of ​​10cm*10cm.

[0050] Raw materials: 10cm*10cm nickel foam, 6.06g iron nitrate nonahydrate, 0.873g cobalt nitrate hexahydrate, appropriate amount of potassium hydroxide, concentrated hydrochloric acid, deionized water, and anhydrous ethanol.

[0051] Synthesis steps

[0052] 1. Take 150 ml of deionized water and pour it into beaker A. Weigh 6.06 g of ferric nitrate nonahydrate and 0.873 g of cobalt nitrate hexahydrate. Stir for 30 min under magnetic stirring to mix them evenly to obtain a 0.1 MFe(NO3)3, 0.05 MCo(NO3)2 mixed salt solution A.

[0053] 2. Put the nickel foam into a beaker, add an appropriate amount of concentrated hydrochloric acid, and clean it by ultrasonic for 10 minutes; then add an appropriate amount of deionized water, and clean it by ultrasonic for 10 minutes. Repeat the deionized water cleaning step 3 times, and then vacuum dry it at 60°C for 12 hours;

[0054] 3. Place the nickel foam in salt solution A, ultrasonicate for 10 minutes, and then let it stand for 8 hours;

[0055] 4. Prepare 200 ml of 0.5 M KOH solution B;

[0056] 5. Slowly add the prepared solution B into the salt solution A to precipitate the metal ions;

[0057] 6. After the addition of solution B is completed, the nickel foam is taken out, washed three times with deionized water, and then washed three times with anhydrous ethanol, and then vacuum dried at 60°C for 24 hours to prepare an oxygen evolution catalyst for use as a self-supporting OER electrode.

[0058] Test example

[0059] 1. XRD was performed on the oxygen evolution catalyst prepared in the above embodiment of the present invention. The results are as follows: Figure 1 shown.

[0060] Depend on Figure 1 It can be seen that the XRD energy spectrum shows that iron nitrate and cobalt nitrate will precipitate under alkaline conditions, and a layer of cobalt-iron compound powder, which is Fe3O4 and CoFe2O4, can be deposited on the surface of nickel foam.

[0061] 2. The oxygen evolution catalyst prepared in the above embodiment of the present invention was subjected to electron microscope (SEM) scanning and energy spectrum analysis (EDS) analysis. The results are as follows: Figure 2 , Figure 3 shown.

[0062] Depend on Figure 2 , Figure 3 It can be seen that the oxygen evolution catalyst prepared in the above embodiment of the present invention is in the form of nanoparticles with uniform size and good dispersibility. The iron and cobalt elements help to enhance the catalytic activity of the nickel foam itself.

[0063] 3. The oxygen evolution catalyst prepared in the above embodiment of the present invention is used as a self-supporting OER electrode and electrochemical tests are performed:

[0064] Among them, in this test example, all electrochemical tests were performed using an electrochemical workstation (model CHI760E). The catalytic activity of the self-supporting OER electrode prepared in the present invention in an alkaline electrolyte was tested using a three-electrode system, wherein the working electrode was a platinum electrode clamp clamping a cut 1cm*1cm self-supporting OER electrode, the counter electrode was a commercial platinum sheet, the reference electrode was saturated calomel, and the electrolyte was 1M KOH.

[0065] The OER activity of the prepared self-supporting electrode was evaluated using a three-electrode battery system in 1M KOH solution. The linear voltammetric scan curve (LSV) was obtained to evaluate the OER curve. All LSV polarization curves were obtained at a scan rate of 5mV / s. The overpotential was calculated by the equation overpotential=E0+0.059*PH+0.098-1.23. All LSV polarization curves were calibrated to take into account the ohmic voltage drop in the solution. The results are shown in Figure 4 shown.

[0066] Depend on Figure 4 It can be seen that the self-supporting OER electrode shows high activity in the OER reaction, which is manifested by a lower overpotential. The overpotential to reach a current density of 100mA / cm2 in 1M KOH is 227mV, which is one of the key parameters for measuring catalyst efficiency. A lower overpotential means that in practical applications, such as water electrolysis, less additional energy is required.

[0067] The preferred specific embodiments of the present invention are described in detail above. It should be understood that ordinary technicians in the field can make many modifications and changes based on the concept of the present invention without creative work. Therefore, all technical solutions that can be obtained by technicians in the technical field based on the concept of the present invention through logical analysis, reasoning or limited experiments on the basis of the prior art should be within the scope of protection determined by the claims.

Claims

1. A method for preparing a low-cost alkaline medium oxygen evolution catalyst, characterized in that: The steps include: Step 1, mixing an iron metal source and a cobalt metal source, and preparing a salt solution A of a certain concentration; Step 2, washing the nickel foam or nickel metal source with concentrated hydrochloric acid and deionized water and drying, placing it in salt solution A, and standing it for a certain period of time after ultrasonic treatment; Step 3, preparing an alkaline solution source into an alkaline solution B of a certain concentration; slowly adding the alkaline solution B dropwise into the salt solution A to precipitate the metal ions; Step 4: taking out the nickel foam or nickel metal source from the solution, washing it with deionized water and anhydrous ethanol and drying it to prepare an oxygen evolution catalyst.

2. The method for preparing a low-cost alkaline medium oxygen evolution catalyst according to claim 1, characterized in that: In step 1, the iron metal source is selected from one or more of anhydrous ferric acetate, ferric acetate hydrate, anhydrous ferric chloride, ferric chloride hydrate, anhydrous ferric nitrate, ferric nitrate hydrate, anhydrous ferric sulfate, and ferric sulfate hydrate; the cobalt metal source is selected from one or more of anhydrous cobalt acetate, cobalt acetate hydrate, anhydrous cobalt chloride, cobalt chloride hydrate, anhydrous cobalt nitrate, cobalt nitrate hydrate, anhydrous cobalt sulfate, and cobalt sulfate hydrate.

3. The method for preparing a low-cost alkaline medium oxygen evolution catalyst according to claim 1, characterized in that: In step 2, the nickel metal source is selected from one or more of nickel nitrate, nickel nitrate hydrate, nickel chloride, nickel chloride hydrate, nickel acetate, and nickel acetate hydrate.

4. The method for preparing a low-cost alkaline medium oxygen evolution catalyst according to claim 1, characterized in that: The alkaline solution source is selected from one or more of potassium hydroxide, sodium hydroxide, ammonia potassium carbonate, sodium carbonate and ammonium carbonate.

5. The method for preparing a low-cost alkaline medium oxygen evolution catalyst according to claim 1, characterized in that: In step 1, in the salt solution A, the molar concentration of iron element is twice that of cobalt element.

6. The method for preparing a low-cost alkaline medium oxygen evolution catalyst according to claim 5, characterized in that: In step 1, the molar concentration of iron in the salt solution A is 0.1 mol / L, and the molar concentration of cobalt is 0.05 mol / L; in step 2, the molar concentration of OH in the alkaline solution B is 0.1 mol / L. - Concentration range: 0.5mol / L.

7. The method for preparing a low-cost alkaline medium oxygen evolution catalyst according to claim 1, characterized in that: In step 2, the ultrasonic time is 10 minutes, the ultrasonic temperature is 25-100° C., and the standing time is 8 hours.

8. The method for preparing a low-cost alkaline medium oxygen evolution catalyst according to claim 1, characterized in that: In step 2 and step 4, the drying is carried out by vacuum drying, and the vacuum drying temperature is 60-80° C. and the drying time is 12-24 hours.

9. An oxygen evolution catalyst prepared by the preparation method according to any one of claims 1 to 8.

10. Use of the oxygen evolution catalyst according to claim 9 in preparing a self-supporting OER electrode for catalytic oxygen evolution.

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