A cobalt-based oxygen evolution catalyst and a preparation method and application thereof

Abstract

The application belongs to the technical field of electrocatalysis, and particularly relates to a cobalt-based oxygen evolution catalyst and a preparation method and application thereof. The cobalt-based oxygen evolution catalyst of the application is coated with a uniform cobalt-based boride nanosheet layer on a cobalt-based precursor material to form a petal structure. The catalyst has good water electrolysis oxygen evolution reaction catalytic performance.

Description

Technical Field

[0001] This invention belongs to the field of electrocatalysis technology, specifically relating to a cobalt-based oxygen evolution catalyst, its preparation method, and its application. Background Technology

[0002] Hydrogen production technologies can be mainly divided into three categories: 1) fossil fuel hydrogen production, 2) biomass hydrogen production, and 3) water electrolysis hydrogen production. Fossil fuel hydrogen production technologies are mature, such as industrialized natural gas-to-hydrogen (SMR) and coal-to-hydrogen processes, but the hydrogen production process emits large amounts of carbon dioxide, polluting the environment. Biomass hydrogen production has lower carbon dioxide emissions, but the unstable hydrogen production process limits its large-scale application. In contrast, water electrolysis hydrogen production technology is environmentally friendly and pollution-free, and can be combined with wind and solar power generation technologies for large-scale hydrogen production. It is a sustainable technology for producing green hydrogen fuel with broad development prospects.

[0003] Hydrogen production through water electrolysis utilizes the electrolysis of water to produce "green hydrogen." Catalysts for water electrolysis are mainly classified into two categories: noble metals and non-noble metals. Noble metal catalysts possess high catalytic activity, but their limited global reserves and high cost restrict their large-scale industrial application. Non-noble metal catalysts mainly include transition metal-based compounds and carbon-based catalysts, offering the advantage of low cost, but with limited activity. Therefore, improving the activity and stability of transition metal-based catalysts has become a research hotspot and challenge. From the perspective of the reaction mechanism of water electrolysis, the hydrogen evolution reaction is a two-electron reaction process, while the oxygen evolution reaction involves a four-electron reaction process, exhibiting slower reaction kinetics. Therefore, developing efficient and durable oxygen evolution reaction catalysts is of great significance to the development of water electrolysis hydrogen production technology.

[0004] The prior art discloses a Co-B / Co-MOF nanomaterial and its preparation method and application (CN113463125B). The preparation process of this method is complex and not conducive to large-scale commercial use. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention provides a cobalt-based oxygen evolution catalyst, its preparation method, and its applications. The cobalt-based oxygen evolution catalyst obtained by this invention comprises a uniform layer of cobalt-based boride nanosheets coated on a carbon-based material, forming a petal structure. This catalyst exhibits excellent catalytic performance in the oxygen evolution reaction of water electrolysis.

[0006] The technical solution provided by this invention is as follows:

[0007] A method for preparing a cobalt-based oxygen evolution catalyst includes the following steps:

[0008] Step 1: Pretreatment: The carbon cloth electrode is ultrasonically treated in ethanol, acetone and deionized water in sequence, and then cleaned and dried to obtain the carbon cloth electrode material;

[0009] Step 2: Hydrophilic treatment: Soak the carbon cloth in a mixture of concentrated sulfuric acid and concentrated nitric acid, then rinse and dry it with deionized water;

[0010] Step 3: Dissolve a certain amount of cobalt salt in deionized water to form solution A; dissolve a certain amount of 2-methylimidazole in deionized water to form solution B;

[0011] Step 4: Place the carbon cloth obtained in Step 2 into solution A and sonicate for 5 minutes, then slowly add solution B while stirring continuously to carry out the reaction; rinse the reacted carbon cloth alternately with deionized water and anhydrous ethanol, and then dry it in a vacuum drying oven to prepare carbon cloth with cobalt-based precursor material.

[0012] Step 5: Weigh out a certain amount of cobalt salt, sodium succinate (C4H4Na2O4), sodium sulfate, and dimethylaminoborane (C2H 10 BN), add deionized water to prepare a homogeneous solution C;

[0013] Step 6: Place the carbon cloth with cobalt-based precursor material obtained in Step 4 into solution C prepared in Step 5 for a mild boration process. After the reaction, take it out, wash it with deionized water, and then dry it in a vacuum drying oven.

[0014] Step 7: Calcine the material obtained in Step 6 to obtain a cobalt-based boride catalyst electrode material.

[0015] Specifically, in step 2:

[0016] Concentrated sulfuric acid and concentrated nitric acid are mixed at a volume ratio of 3:(0.9–1.1);

[0017] Soaking time is 10 to 14 hours.

[0018] Specifically, in step 3:

[0019] The cobalt salt is cobalt nitrate hexahydrate, with a cobalt ion concentration of 0.055–0.065 mol / L;

[0020] The molar concentration of 2-methylimidazole is 0.45–0.50 mol / L;

[0021] The reaction time is: stirring for 5.5 to 6.5 hours, settling for 5.5 to 6.5 hours.

[0022] Specifically, in step 4: the temperature of the vacuum drying oven is 35-45℃, and the drying time is 6-12 hours.

[0023] Specifically, in step 5:

[0024] The cobalt salt is cobalt nitrate hexahydrate, with a cobalt ion concentration of 0.045–0.055 mol / L;

[0025] The molar concentration of sodium succinate is 0.08–0.1 mol / L;

[0026] The molar concentration of sodium sulfate is 0.009–0.011 mol / L;

[0027] The molar concentration of dimethylaminoborane is 0.09–0.11 mol / L.

[0028] Specifically, in step 6: the borylation process takes 0.8 to 1.2 hours, the vacuum drying oven temperature is 35 to 45°C, and the drying time is 6 to 12 hours.

[0029] Specifically, in step 7, the calcination treatment is as follows:

[0030] Argon gas was introduced at a pressure of 91–111 kPa;

[0031] The calcination temperature is 195–205℃;

[0032] Heating rate: 4.5–5.5 °C / min;

[0033] Insulation time: 1.5–2.5 hours;

[0034] Remove from the refrigerator after it has cooled to room temperature naturally.

[0035] The present invention also provides a cobalt-based oxygen evolution catalyst having a sheet-like matrix formed from a cobalt-based precursor material, wherein the sheet-like matrix is ​​externally coated with cobalt-based boride nanosheets, the cobalt-based boride nanosheets forming a petal structure.

[0036] The present invention also provides the application of cobalt-based oxygen evolution catalysts as catalysts for the oxygen evolution reaction of water electrolysis under alkaline conditions.

[0037] The catalyst of this invention exhibits excellent electrochemical oxygen evolution reaction activity. Under the conditions of water electrolysis with 1M KOH at 25°C, it can achieve 10 mA / cm² at a voltage of 1.479V. 2 The current density and stability performance after 20 hours were good.

[0038] Specifically, at 10mA / cm 2 The overpotential at the current density is less than or equal to 249mV.

[0039] The catalyst provided by this invention has a smaller overpotential for the oxygen evolution reaction, which is beneficial to the catalytic process of the oxygen evolution reaction.

[0040] Preferably, in step 1, the carbon cloth size is 2cm×4cm; the amount of deionized water, ethanol, and acetone is 10ml each, and the ultrasonic time is: 15 minutes for ethanol, 15 minutes for acetone, and 15 minutes for deionized water.

[0041] Preferably, in step 2, concentrated sulfuric acid and concentrated nitric acid are mixed at a volume ratio of 3:1, with 15 ml of concentrated sulfuric acid and 5 ml of concentrated nitric acid.

[0042] Preferably, in step 3, the cobalt salt is cobalt nitrate hexahydrate, and the molar concentration of cobalt ions is 0.06 mol / L; the molar concentration of 2-methylimidazole is 0.48 mol / L; and the reaction time is: stirring for 6 hours and settling for 6 hours.

[0043] Preferably, in step 4, the deionized water and anhydrous ethanol are alternately rinsed 2 to 3 times, the temperature of the vacuum drying oven is 40°C, and the drying time is 6 to 12 hours.

[0044] Preferably, in step 5, the cobalt salt is cobalt nitrate hexahydrate, with a cobalt ion concentration of 0.05 mol / L; the sodium succinate concentration is 0.09 mol / L; the sodium sulfate concentration is 0.01 mol / L; and the dimethylaminoborane concentration is 0.1 mol / L.

[0045] Preferably, in step 6, the boration reaction time is 1 hour, the vacuum drying oven temperature is 40°C, and the drying time is 6 to 12 hours.

[0046] Preferably, in step 7, the calcination treatment specifically involves: introducing argon gas at a pressure of 1-101 kPa, calcining at a temperature of 200°C, a heating rate of 5°C / min, holding for 2 hours, and then removing the product after natural cooling to room temperature.

[0047] This step involves heat treatment of the catalyst material to improve its crystalline structure.

[0048] Compared with the prior art, the present invention has the following beneficial effects:

[0049] 1) The cobalt-based oxygen evolution reaction catalyst prepared by this invention is grown in situ on carbon cloth and can be directly used as the working electrode for electrolysis reaction, which has commercial application prospects.

[0050] 2) The cobalt-based oxygen evolution reaction catalyst prepared by this invention has a larger specific surface area, exposes more active sites, and has better catalytic performance. It also exhibits excellent activity and stability in alkaline electrolytes.

[0051] 3) The preparation process of this invention is relatively mild, and the catalyst precursor can be synthesized in an aqueous solution at room temperature. Attached Figure Description

[0052] Figure 1 This is a scanning electron microscope (SEM) image of the cobalt-based precursor material prepared in step 3 of Example 1 of the present invention.

[0053] Figure 2 This is a scanning electron microscope (SEM) image of the cobalt-based boride catalyst electrode material prepared in step 5 of Example 2 of the present invention.

[0054] Figure 3 This is the elemental distribution (EDS) diagram of the cobalt-based boride catalyst electrode material prepared in step 5 of Example 2 of the present invention.

[0055] Figure 4 The graphs show the oxygen evolution reaction performance of the cobalt-based boride catalyst electrode materials prepared in Examples 1 to 3 of this invention under 1 M KOH conditions.

[0056] Figure 5 This is a voltage-time stability test curve of the cobalt-based boride catalyst electrode material prepared in step 5 of Example 2 of the present invention under a 1M KOH environment. Detailed Implementation

[0057] The principles and features of the present invention are described below. The embodiments given are for illustrative purposes only and are not intended to limit the scope of the invention. Unless otherwise specified, the test methods used in the embodiments are conventional methods; the materials and reagents used are commercially available unless otherwise specified.

[0058] Example 1

[0059] A method for preparing a cobalt-based oxygen evolution reaction catalyst includes the following steps:

[0060] Step 1, carbon cloth pretreatment: Sonicate a 2cm×4cm piece of carbon cloth in 10ml ethanol, 10ml acetone and 10ml deionized water for 15 minutes in sequence, and then dry it in a vacuum drying oven at 40℃ for 6 hours.

[0061] Step 2, hydrophilic treatment: Soak the pretreated carbon cloth in an acid solution of 15ml concentrated sulfuric acid and 5ml concentrated nitric acid for 12 hours, then wash it with deionized water and dry it in a vacuum drying oven at 40℃ for 6 hours.

[0062] Step 3: Preparation of cobalt-based precursor material: Add 1.74g of Co(NO3)2·6H2O to 100ml of deionized water to form solution A. Place the treated carbon cloth into solution A and sonicate for 5 minutes. Add 3.96g of 2-methylimidazole to 100ml of deionized water to form solution B, and slowly pour it into solution A and stir for 6 hours, then let it stand for 6 hours. Take out the carbon cloth, rinse it three times alternately with deionized water and anhydrous ethanol, and then dry it in a vacuum drying oven at 40℃ for 6 hours to prepare the cobalt-based precursor material.

[0063] Step 4: Add 1.5g Co(NO3)2·6H2O, 1.45g C4H4Na2O4, 0.72g Na2SO4, and 0.6g C2H4O to 200ml of water in sequence. 10 BN is stirred for 5 minutes to dissolve it, thus obtaining a mildly borated reaction solution. The prepared cobalt-based precursor material is placed in the solution and reacted for 1 hour. After that, it is taken out, washed with deionized water, and dried in a vacuum drying oven at 40°C for 6 hours.

[0064] Example 2

[0065] A method for preparing a cobalt-based oxygen evolution reaction catalyst includes the following steps:

[0066] Step 1, carbon cloth pretreatment: Sonicate a 2cm×4cm piece of carbon cloth in 10ml ethanol, 10ml acetone and 10ml deionized water for 15 minutes in sequence, and then dry it in a vacuum drying oven at 40℃ for 6 hours.

[0067] Step 2, hydrophilic treatment: Soak the pretreated carbon cloth in an acid solution of 15ml concentrated sulfuric acid and 5ml concentrated nitric acid for 12 hours, then wash it with deionized water and dry it in a vacuum drying oven at 40℃ for 6 hours.

[0068] Step 3: Preparation of cobalt-based precursor material: Add 1.74g of Co(NO3)2·6H2O to 100ml of deionized water to form solution A. Place the treated carbon cloth into solution A and sonicate for 5 minutes. Add 3.96g of 2-methylimidazole to 100ml of deionized water to form solution B, and slowly pour it into solution A and stir for 6 hours, then let it stand for 6 hours. Take out the carbon cloth, rinse it three times alternately with deionized water and anhydrous ethanol, and then dry it in a vacuum drying oven at 40℃ for 6 hours to prepare the cobalt-based precursor material.

[0069] Step 4: Add 1.5g Co(NO3)2·6H2O, 1.45g C4H4Na2O4, 0.72g Na2SO4, and 0.6g C2H4O to 200ml of water in sequence. 10BN is stirred for 5 minutes to dissolve it, thus obtaining a mildly borated reaction solution. The prepared cobalt-based precursor material is placed in the solution and reacted for 1 hour. It is then removed, washed with deionized water, and dried in a vacuum drying oven at 40°C for 6 hours.

[0070] Step 5: Calcine the material obtained in the previous step under an argon atmosphere of 101 kPa at a temperature of 200°C, a heating rate of 5°C / min, and a holding time of 2 hours. After naturally cooling to room temperature, the material is removed to obtain the cobalt-based boride catalyst electrode material.

[0071] Example 3

[0072] This embodiment is basically the same as embodiment 2, except that the calcination temperature is different in step 5. The calcination is carried out in an argon atmosphere of 101 kPa, the calcination temperature is 500℃, the heating rate is 5℃ / min, the holding time is 2 hours, and after natural cooling to room temperature, it is taken out to obtain the cobalt-based boride catalyst electrode material.

[0073] The morphology of the catalyst material was observed using scanning electron microscopy.

[0074] Figure 1 The image shows the SEM image of the cobalt-based precursor material prepared in step 3 of Example 1. It can be clearly seen that the cobalt-based precursor material is a sheet-like array structure that is uniformly grown on the surface of carbon cloth fibers.

[0075] Figure 2 The image shows an SEM image of the cobalt-based precursor material prepared in step 5 of Example 2. It can be clearly seen that the nanosheets of cobalt-based boride form a petal structure, uniformly coating the sheet-like matrix formed by the cobalt-based precursor material.

[0076] Figure 3 The image shows the elemental distribution of the cobalt-based boride catalyst electrode material prepared in step 5 of Example 2. It can be seen from the image that the Co, O, N and B elements are evenly distributed on the cobalt-based boride material.

[0077] The cobalt-based boride catalysts prepared in Examples 1-3 were applied to the oxygen evolution reaction in water electrolysis. The electrochemical performance of these catalysts was tested using a Chenhua CHI 760E electrochemical workstation. The test system was a three-electrode system: a carbon rod was used as the counter electrode, Hg / HgO as the reference electrode, and the prepared cobalt-based boride catalyst electrode material was used as the working electrode, held in place by a platinum electrode clamp. 1.0 M KOH was used as the electrolyte solution. The test results are as follows: Figure 4 , Figure 5 As shown.

[0078] Figure 4The graphs show the oxygen evolution reaction (OER) performance of the cobalt-based boride catalyst electrode materials prepared in Examples 1-3 under an alkaline environment of 1.0 M KOH. The test results show that the sample prepared in Example 2 has the best OER catalytic performance at 10 mA / cm². 2 The overpotential at current density is only 249mV, which is lower than in other embodiments.

[0079] Figure 5 The voltage-time stability curve of the cobalt-based boride catalyst electrode material prepared in Example 2 under a 1.0 M KOH alkaline environment is shown at 10 mA / cm². 2 It can operate stably for up to 20 hours at current density.

[0080] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing a cobalt-based oxygen evolution catalyst, characterized in that, Includes the following steps: Step 1: Pretreatment: The carbon cloth electrode was ultrasonically treated in ethanol, acetone and deionized water in sequence, and then cleaned and dried to obtain the carbon cloth electrode material; Step 2: Hydrophilic treatment: Soak the carbon cloth in a mixture of concentrated sulfuric acid and concentrated nitric acid, then rinse and dry it with deionized water; Step 3: Dissolve a certain amount of cobalt salt in deionized water to form solution A; dissolve a certain amount of 2-methylimidazole in deionized water to form solution B; Step 4: Place the carbon cloth obtained in Step 2 into solution A and sonicate for 5 min, then slowly add solution B while stirring continuously to carry out the reaction; rinse the reacted carbon cloth alternately with deionized water and anhydrous ethanol, and then dry it in a vacuum drying oven to prepare carbon cloth with cobalt-based precursor material. Step 5: Weigh a certain amount of cobalt salt, sodium succinate, sodium sulfate and dimethylaminoborane, add deionized water to prepare a homogeneous solution C; Step 6: Place the carbon cloth with cobalt-based precursor material obtained in Step 4 into solution C prepared in Step 5 for a mild boration process. After the reaction, take it out, wash it with deionized water, and then dry it in a vacuum drying oven. Step 7: Introduce argon gas and calcine the material obtained in Step 6 to obtain cobalt-based boride catalyst electrode material. The calcination temperature is 195-205℃ and the holding time is 1.5-2.5 hours.

2. The method for preparing the cobalt-based oxygen evolution catalyst according to claim 1, characterized in that, In step 2: Concentrated sulfuric acid and concentrated nitric acid are mixed at a volume ratio of 3:(0.9~1.1); Soaking time is 10 to 14 hours.

3. The method for preparing the cobalt-based oxygen evolution catalyst according to claim 1, characterized in that, In step 3: The cobalt salt is cobalt nitrate hexahydrate, with a cobalt ion concentration of 0.055–0.065 mol / L; The molar concentration of 2-methylimidazole is 0.45–0.50 mol / L.

4. The method for preparing the cobalt-based oxygen evolution catalyst according to claim 1, characterized in that, In step 4: The temperature of the vacuum drying oven is 35-45℃, and the drying time is 6-12 hours; The reaction time is: stirring for 5.5 to 6.5 hours, settling for 5.5 to 6.5 hours.

5. The method for preparing the cobalt-based oxygen evolution catalyst according to claim 1, characterized in that, In step 5: The cobalt salt is cobalt nitrate hexahydrate, with a cobalt ion concentration of 0.045–0.055 mol / L; The molar concentration of sodium succinate is 0.08–0.1 mol / L; The molar concentration of sodium sulfate is 0.009–0.011 mol / L; The molar concentration of dimethylaminoborane is 0.09–0.11 mol / L.

6. The method for preparing the cobalt-based oxygen evolution catalyst according to claim 1, characterized in that, In step 6: the borylation process takes 0.8 to 1.2 hours, the vacuum drying oven temperature is 35 to 45°C, and the drying time is 6 to 12 hours.

7. The method for preparing the cobalt-based oxygen evolution catalyst according to claim 1, characterized in that, In step 7, the calcination treatment specifically involves: Argon gas was introduced at a pressure of 91–111 kPa; Heating rate: 4.5–5.5 °C / min; Remove from the refrigerator after it has cooled to room temperature naturally.

8. A cobalt-based oxygen evolution catalyst prepared by the method according to any one of claims 1 to 7, characterized in that: A cobalt-based precursor material is loaded onto carbon cloth to form a sheet-like matrix, and the sheet-like matrix is ​​wrapped with a nano-flower-like structure, which is formed by sheet-like cobalt-based borides as petals.

9. An application of the cobalt-based oxygen evolution catalyst according to claim 8, characterized in that: It serves as a catalyst for the oxygen evolution reaction in water electrolysis under alkaline conditions.

10. The application according to claim 9, characterized in that: At 10 mA / cm 2 The overpotential at the current density is less than or equal to 249 mV.

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