Iron-nitrogen co-doped carbon black-based catalyst, and preparation method and application thereof

Abstract

This invention provides an iron-nitrogen co-doped carbon black-based catalyst, its preparation method, and its application. Acidified carbon black is mixed with an alcohol solution containing iron-nitrogen macromolecules, heated, and stirred to obtain a dispersion 2. The dispersion 2 undergoes solid-liquid separation, and the resulting solid reactant is dried and calcined to obtain reactant 2. Reactant 2 is etched under acidic conditions, washed, and dried to obtain the iron-nitrogen co-doped carbon black catalyst. This catalyst, with a high iron loading, uses acidified carbon black as a conductive substrate on which iron-nitrogen macromolecules dissolved in alcohol are adsorbed. These iron-nitrogen macromolecules possess hydrophilic functional groups, and the Fe loading is determined by the amount of iron-nitrogen macromolecules. The catalyst exhibits significantly better oxygen reduction reaction performance than commercial Pt / C catalysts and demonstrates good stability, showing broad application prospects in the fields of electrocatalytic oxygen reduction reactions and zinc-air batteries.

Description

Technical Field

[0001] This invention belongs to the field of catalyst preparation technology, specifically to an iron-nitrogen co-doped carbon black-based catalyst, its preparation method, and its application. Background Technology

[0002] Zinc-air batteries have attracted widespread attention due to their high theoretical capacity and environmental friendliness. However, the slow oxygen reduction reaction (ORR) at the air cathode hinders their further development. Although platinum-based catalysts are widely used as common commercial ORR catalysts, they are scarce and expensive due to their precious metal reserves. Furthermore, their stability does not meet current requirements. Therefore, there is an urgent need to develop a cost-effective, high-performance catalyst.

[0003] Transition metals are more abundant and cheaper than noble metals, making them a promising alternative to platinum-based catalysts. Studies have shown that iron-nitrogen co-doped carbon-based catalysts with Fe-NC structures exhibit ORR activities comparable to noble metals. However, to prevent aggregation of active centers, their iron content is typically between 0.1 and 0.8 wt.%, making further improvements in ORR performance difficult. Although some organic macromolecules (such as iron phthalocyanine) have iron contents exceeding 1 wt.% and directly possess an Fe-NC structure, their extremely poor solubility limits their further application as catalysts. Summary of the Invention

[0004] To address the problems existing in the prior art, this invention provides an iron-nitrogen co-doped carbon black-based catalyst, its preparation method, and its application. This method is simple, efficient, and uses low-cost raw materials. It can prepare high-load iron-nitrogen co-doped carbon-based catalysts, which have great application value in the ORR field.

[0005] To achieve the above objectives, the present invention provides the following technical solution: an iron-nitrogen co-doped carbon black catalyst, wherein acidified carbon black is used as a conductive substrate, on which iron-nitrogen macromolecules dissolved in alcohol are adsorbed, wherein the iron-nitrogen macromolecules have hydrophilic functional groups, and the iron loading on the catalyst is determined by the amount of iron-nitrogen macromolecules.

[0006] Furthermore, the iron-nitrogen macromolecule is hydroxyheme.

[0007] This invention also provides a method for preparing an iron-nitrogen co-doped carbon black catalyst, comprising the following steps:

[0008] S1 mixes acidified carbon black with an iron-nitrogen macromolecular alcohol solution, heats and stirs to obtain dispersion 2;

[0009] S2 performs solid-liquid separation on dispersion 2, and dries and calcines the obtained solid reactant to obtain reactant 2;

[0010] After S3 reactant 2 is etched under acidic conditions, it is washed and dried to obtain an iron-nitrogen co-doped carbon black catalyst.

[0011] Furthermore, in S1, carbon black with a mass ratio of 1:100 to 1:750 is mixed with pure nitric acid and treated at 60℃ to 80℃ for 24h to 72h to perform acidification.

[0012] Further, in S1, a 0.2 mmol / L to 15 mmol / L iron-nitrogen macromolecular ethanol solution is added to the acidified carbon black, and the mixture is stirred at 600 rpm to 1000 rpm for 24 h to 72 h at 40 °C to 70 °C to obtain dispersion 2.

[0013] Furthermore, in S2, dispersion 2 is centrifuged at a speed of 6000 rpm to 10000 rpm for 5 min to 20 min to separate solids and liquids. The resulting solid reactants are dried under a vacuum of -3000 kPa to -2000 kPa and at 40°C to 80°C.

[0014] Furthermore, in S2, the calcination is carried out in a protective atmosphere at 800℃~1000℃ for 1h~3h, with a heating rate of 2℃·min. -1 ~10℃·min -1 .

[0015] Furthermore, in S3, the etching is performed using dilute hydrochloric acid of 0.05 mol / L to 0.3 mol / L, and the etching time is 20 min to 120 min.

[0016] Furthermore, in S3, the drying is carried out under vacuum conditions of -3000 kPa to -2000 kPa and 40°C to 80°C.

[0017] Furthermore, iron-nitrogen co-doped carbon black catalyst is used as the air cathode.

[0018] Compared with the prior art, the present invention has at least the following beneficial effects:

[0019] This invention provides an iron-nitrogen co-doped carbon black-based catalyst, using acidified carbon black as a conductive substrate. The iron-nitrogen macromolecules adsorbed on it serve as the active centers for ORR (Organic Reactive Protein). Because the iron-nitrogen macromolecules have hydrophilic functional groups, they can be fully soluble in alcohols. Carbon black can fully adsorb the iron-nitrogen macromolecules in alcohols. The iron-nitrogen macromolecules serve as both iron and nitrogen sources. The amount of Fe in the catalyst can be controlled by adjusting the amount of iron-nitrogen macromolecules, thereby obtaining an iron-nitrogen co-doped carbon black-based catalyst with high Fe loading.

[0020] This invention provides a method for preparing an iron-nitrogen co-doped carbon black catalyst. Acidified carbon black is added to an alcohol solution containing iron and nitrogen macromolecules. After thorough stirring, centrifugation, drying, and calcination, the catalyst is etched in acid, washed, and dried to obtain the iron-nitrogen co-doped carbon black catalyst. The iron and nitrogen macromolecules serve as both the iron and nitrogen sources. By adjusting the amount of iron and nitrogen macromolecules, a high iron loading (1.1 wt.%) iron-nitrogen co-doped carbon black-based catalyst can be prepared. The method is simple, requires no other processes, and the raw materials are inexpensive and readily available, making it highly valuable for applications in the field of electrocatalytic ORR (Organic Ratio Reduction).

[0021] Furthermore, this invention uses ferric heme as an organic macromolecule. Compared with traditional iron phthalocyanine, it contains hydrophilic functional groups such as -OH and -COOH, which significantly improves its solubility. Therefore, it is soluble in ethanol and can be fully adsorbed by carbon black. Moreover, the stable Fe-N4 coordination structure in ferric heme can effectively inhibit the aggregation of Fe during the calcination process, and can still serve as a single-atom active center for ORR.

[0022] Furthermore, compared with commercial platinum-carbon catalysts, the iron-nitrogen co-doped carbon black-based catalyst prepared in this invention exhibits better performance and better stability, and the power density of a zinc-air battery assembled using it as an air cathode can reach 90 mW / cm². -2 This can promote the further development of zinc-air batteries. Attached Figure Description

[0023] Figure 1 This is a schematic diagram of the molecular structure of hydroxymethemoglobin.

[0024] Figure 2 This is the XRD pattern of the iron-nitrogen co-doped carbon black catalyst obtained in Example 1.

[0025] Figure 3 This is a TEM image of the iron-nitrogen co-doped carbon black catalyst obtained in Example 1.

[0026] Figure 4 This is a pore size distribution diagram of the iron-nitrogen co-doped carbon black catalyst obtained in Example 1.

[0027] Figure 5 This refers to the stability of the oxygen reduction reaction of the iron-nitrogen co-doped carbon black catalyst obtained in Example 1.

[0028] Figure 6 The polarization curves of the oxygen reduction reaction of the iron-nitrogen co-doped carbon black catalyst obtained in Example 1 and the commercial platinum-carbon (Pt / C) catalyst are shown.

[0029] Figure 7 These are the polarization curves and power density curves of the zinc-air battery discharge process of the iron-nitrogen co-doped carbon black catalyst obtained in Example 1 and the commercial iridium oxide (IrO2) catalyst.

[0030] Figure 8 These are the oxygen reduction reaction polarization curves of the iron-nitrogen co-doped carbon black catalysts obtained in Examples 2-5.

[0031] Figure 9 It refers to the iron content of the iron-nitrogen co-doped carbon black catalysts obtained in Examples 1-5.

[0032] Figure 10 This is a TEM image of the iron-nitrogen co-doped carbon black catalyst obtained in Example 4.

[0033] Figure 11 This is a TEM image of the iron-nitrogen co-doped carbon black catalyst obtained in Example 5. Detailed Implementation

[0034] The present invention will be further described below with reference to the accompanying drawings and specific embodiments.

[0035] This invention provides a method for preparing an iron-nitrogen co-doped carbon black catalyst, comprising the following steps:

[0036] Step 1: Mix carbon black with pure nitric acid at a mass ratio of 1:60 to 1:750 and treat at 60℃ to 80℃ for 24h to 72h to obtain dispersion 1;

[0037] Step 2: Add 0.2 mmol / L to 15 mmol / L of an iron-nitrogen macromolecular alcohol solution to dispersion 1, and stir at 600 rpm to 1000 rpm at 40℃ to 70℃ for 24 h to 72 h to obtain dispersion 2.

[0038] Step 3: Centrifuge dispersion 2 at a speed of 6000 rpm to 10000 rpm for 5 min to 20 min to separate solid and liquid. After solid-liquid separation, dry the separated solid reactants in a vacuum oven with a vacuum degree of -3000 kPa to -2000 kPa at 40°C to 80°C to obtain powdered reactants 1.

[0039] Step 4: Calcine reactant 1 in a protective atmosphere at 800℃~1000℃ for 1h~3h, with a heating rate of 2℃·min. -1 ~10℃·min -1 Powdered reactant 2 was obtained.

[0040] Step 5: Reactant 2 is etched under acidic conditions for 20-120 min to remove metal nanoparticles that may be generated during calcination. After washing, it is dried in a vacuum oven at 40-80°C with a vacuum degree of -3000 to -2000 kPa to obtain iron-nitrogen co-doped carbon black catalyst.

[0041] Preferably, the iron-nitrogen macromolecules should have hydrophilic functional groups, and ethanol should be selected as the solvent.

[0042] Preferred, such as Figure 1 As shown, the iron-nitrogen macromolecule is hydroxyheme. Hydroxyheme naturally has an Fe-NC structure and also contains hydrophilic functional groups such as -OH and -COOH, which can improve the solubility of organic macromolecules.

[0043] Preferably, the protective atmosphere is nitrogen.

[0044] Preferably, the etching solution is a dilute hydrochloric acid solution of 0.05 mol / L to 0.3 mol / L.

[0045] A co-doped carbon black catalyst was prepared using the above method. Acidified carbon black was used as the conductive substrate, on which dissolved iron-nitrogen macromolecules were adsorbed. These macromolecules possess hydrophilic functional groups. The Fe loading on the catalyst was determined by the amount of iron-nitrogen macromolecules, specifically within the range of 0.3–1.1 wt.%. When the Fe loading reached 1.1 wt.%, the XRD pattern of the catalyst showed only broad peaks for carbon, indicating a carbon structure. TEM images showed that the catalyst morphology consisted of stacked nanosheets without obvious nanoparticles. At this point, the catalyst exhibited optimal ORR performance, with a half-wave potential of 0.93 V, and the power density of the assembled zinc-air battery reached 90 mW cm⁻¹. -2 When the Fe content reaches 1.4 and 1.8 wt.%, large-diameter nanoparticles appear, which cannot maintain the morphology of single atoms, but the oxygen reduction performance is not affected. Therefore, both can still be used as high-performance electrocatalysts for oxygen reduction reaction.

[0046] This invention involves adding acidified carbon black to an ethanol solution containing hydroxyferric heme, stirring thoroughly, centrifuging and drying, calcining, then etching in dilute hydrochloric acid and washing and drying to obtain an iron-nitrogen co-doped carbon black catalyst. The materials used are inexpensive and readily available, the method is simple, and the oxygen reduction reaction performance of the obtained catalyst is significantly better than that of commercial Pt / C, and the obtained catalyst has good stability during the oxygen reduction reaction.

[0047] Using hydroxyheme as the iron and nitrogen source and carbon black as the carrier, the iron content in the catalyst can be controlled by changing the amount of hydroxyheme. Therefore, it has broad application prospects in the fields of electrocatalytic oxygen reduction reaction and zinc-air battery.

[0048] Example 1

[0049] 1. Mix 0.2g of carbon black with 30mL of pure nitric acid, treat at 70℃ for 24h and wash;

[0050] 2. The washed carbon black was added to 50 mL of ethanol solution containing 0.1 mmol of hydroxyheme and stirred at 1000 rpm for 24 h at 60 °C.

[0051] 3. After stirring, the dispersion was centrifuged at 8000 rpm for 10 min to remove the supernatant, and then vacuum dried at 60℃ and -2000 kPa.

[0052] 4. The dried powder is dried at 2℃·min -1 The heating rate was calcined at 900℃ for 2 hours;

[0053] 5. The calcined powder was etched in 0.1 mol / L dilute hydrochloric acid for 30 min, washed, and then dried in a vacuum oven at 60 °C with a vacuum degree of -2000 kPa to obtain the iron-nitrogen co-doped carbon black catalyst.

[0054] Depend on Figure 2 It can be seen that the XRD pattern of the catalyst obtained in Example 1 only has broad peaks for carbon and no diffraction peaks for iron, indicating that iron has not agglomerated into nanoparticles, and therefore the catalyst retains the structure of carbon.

[0055] Depend on Figure 3 It can be seen that the TEM image of the catalyst obtained in Example 1 does not show obvious nanoparticles. Figure 4 The pore size distribution diagram shows that the catalyst has a distinct mesoporous structure. The polarization curve of the oxygen reduction reaction of the iron-nitrogen co-doped carbon black catalyst is shown in the figure. Figure 6 As shown in line 1, its half-wave potential is 0.93V, while Figure 6 The half-wave potential of Pt / C in line 2 is only 0.88 V. The stability of this catalyst in the oxygen reduction reaction is as follows: Figure 5 As shown, it remains stable within 10,000 s. The discharge polarization curves and power density curves of a zinc-air battery assembled with an iron-nitrogen co-doped carbon black catalyst as the air cathode are obtained from... Figure 7 As shown in line 1, the power density is 90 mW / cm². -2 much larger Figure 7 60 mW cm⁻¹ of Pt / C catalyst in line 2 -2 The iron content of the catalyst obtained in Example 1 was determined by... Figure 9 As shown in column 3, it is 1.1 wt.%.

[0056] Example 2

[0057] The washed carbon black was added to 50 mL of ethanol solution containing 0.04 mmol of hydroxyheme and stirred at 1000 rpm for 24 h at 60 °C. The remaining steps were the same as in Example 1.

[0058] Depend on Figure 8 It can be seen that the catalyst obtained in Example 2 has a half-wave potential of 0.9V for the oxygen reduction reaction. The iron content of the catalyst obtained in Example 2 is... Figure 9 As shown in column 1, it is 0.3 wt.%.

[0059] Example 3

[0060] The washed carbon black was added to 50 mL of ethanol solution containing 0.08 mmol of hydroxyheme and stirred at 1000 rpm for 24 h at 60 °C. The remaining steps were the same as in Example 1.

[0061] Depend on Figure 8 It can be seen that the catalyst obtained in Example 3 has a half-wave potential of 0.91V for the oxygen reduction reaction. The iron content of the catalyst obtained in Example 3 is... Figure 9 As shown in column 2, it is 0.6 wt.%.

[0062] Example 4

[0063] The washed carbon black was added to 50 mL of ethanol solution containing 0.15 mmol of hydroxyheme and stirred at 1000 rpm for 24 h at 60 °C. The remaining steps were the same as in Example 1.

[0064] Depend on Figure 8 It can be seen that the catalyst obtained in Example 4 has a half-wave potential of 0.93V for the oxygen reduction reaction. The iron content of the catalyst obtained in Example 4 is... Figure 9 As shown in column 4, it is 1.4 wt.%.

[0065] Depend on Figure 10 It can be seen that the catalyst obtained in Example 4 contained nanoparticles with a diameter of about 50 nm.

[0066] Example 5

[0067] The washed carbon black was added to 50 mL of ethanol solution containing 0.2 mmol of hydroxyheme and stirred at 1000 rpm for 24 h at 60 °C. The remaining steps were the same as in Example 1.

[0068] Depend on Figure 8 It can be seen that the catalyst obtained in Example 5 has a half-wave potential of 0.93V for the oxygen reduction reaction. The iron content of the catalyst obtained in Example 5 is... Figure 9 As shown in column 4, it is 1.8 wt.%.

[0069] Depend on Figure 11 It can be seen that the catalyst obtained in Example 5 contained nanoparticles with a diameter greater than 100 nm.

[0070] Example 6

[0071] 1. Mix 0.2g of carbon black with 12mL of pure nitric acid, treat at 60℃ for 72h and wash;

[0072] 2. The washed carbon black was added to 50 mL of ethanol solution containing 0.01 mmol of hydroxyheme and stirred at 70 °C and 600 rpm for 72 h.

[0073] 3. After stirring, the dispersion was centrifuged at 6000 rpm for 20 min to remove the supernatant, and then vacuum dried at 40℃ and -2500 kPa.

[0074] 4. The dried powder is dried at 5℃·min -1 The heating rate was calcined at 800℃ for 3 hours;

[0075] 5. The calcined powder was etched in 0.05 mol / L dilute hydrochloric acid for 20 min, washed, and then dried in a vacuum oven at 40 °C with a vacuum degree of -2500 kPa to obtain the iron-nitrogen co-doped carbon black catalyst.

[0076] Example 7

[0077] 1. Mix 0.2g of carbon black with 150mL of pure nitric acid, treat at 80℃ for 36h and wash;

[0078] 2. The washed carbon black was added to 50 mL of ethanol solution containing 0.75 mmol of hydroxyheme and stirred at 800 rpm for 36 h at 40 °C.

[0079] 3. After stirring, the dispersion was centrifuged at 10,000 rpm for 5 min to remove the supernatant, and then vacuum dried at 80℃ and -3000 kPa.

[0080] 4. The dried powder is dried at 10℃·min -1 The heating rate was 1000℃ for 1 hour;

[0081] 5. The calcined powder was etched in 0.03 mol / L dilute hydrochloric acid for 120 min, washed, and then dried in a vacuum oven at 80 °C with a vacuum degree of -3000 kPa to obtain the iron-nitrogen co-doped carbon black catalyst.

Claims

1. A method for preparing an iron-nitrogen co-doped carbon black catalyst, characterized in that, Includes the following steps: S1. Acidified carbon black is mixed with an iron-nitrogen macromolecular alcohol solution and stirred at 40℃~70℃ to obtain dispersion 2. S2 performs solid-liquid separation on dispersion 2, and dries and calcines the obtained solid reactant to obtain reactant 2; After S3 reactant 2 is etched under acidic conditions, it is washed and dried to obtain iron-nitrogen co-doped carbon black catalyst; The iron-nitrogen macromolecule is hydroxyheme; Ethanol is chosen as the alcohol solvent.

2. The method for preparing an iron-nitrogen co-doped carbon black catalyst according to claim 1, characterized in that, In S1, carbon black with a mass ratio of 1:100 to 1:750 is mixed with pure nitric acid and treated at 60℃ to 80℃ for 24h to 72h to achieve acidification.

3. The method for preparing an iron-nitrogen co-doped carbon black catalyst according to claim 1, characterized in that, In S1, a 0.2 mmol / L to 15 mmol / L iron-nitrogen macromolecular ethanol solution is added to acidified carbon black, and the mixture is stirred at 600 rpm to 1000 rpm for 24 h to 72 h at 40 °C to 70 °C to obtain dispersion 2.

4. The method for preparing an iron-nitrogen co-doped carbon black catalyst according to claim 1, characterized in that, In S2, dispersion 2 is centrifuged at 6000 rpm to 10000 rpm for 5 min to 20 min to separate solids and liquids. The resulting solid reactants are dried under a vacuum of -3000 kPa to -2000 kPa and at 40℃ to 80℃.

5. The method for preparing an iron-nitrogen co-doped carbon black catalyst according to claim 1, characterized in that, In S2, the calcination is carried out in a protective atmosphere at 800℃~1000℃ for 1h~3h, with a heating rate of 2℃·min. -1 ~10℃·min -1 .

6. The method for preparing an iron-nitrogen co-doped carbon black catalyst according to claim 1, characterized in that, In S3, the etching is performed using dilute hydrochloric acid with a concentration of 0.05 mol / L to 0.3 mol / L, and the etching time is 20 min to 120 min.

7. The method for preparing an iron-nitrogen co-doped carbon black catalyst according to claim 1, characterized in that, In S3, the drying is carried out under vacuum conditions of -3000 kPa to -2000 kPa and 40°C to 80°C.

8. An iron-nitrogen co-doped carbon black catalyst prepared by any one of claims 1 to 7.

9. The application of the iron-nitrogen co-doped carbon black catalyst according to claim 8 in a zinc-air battery, characterized in that, Iron-nitrogen co-doped carbon black catalyst was used as the air cathode.

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