A high-activity carbon atom site catalyst and its preparation method

Abstract

The present invention specifically provides a high-activity carbon atom site catalyst and its preparation method, which mainly regulates the surrounding carbon atoms by saturating the coordinated single atom p The carbon atom sites have high electrocatalytic oxygen reduction reaction activity by the center; the doped carbon catalyst containing 0.2~5 wt% saturated coordinated single atoms is synthesized by simple co-precipitation and high-temperature pyrolysis. The synthesis method is simple. And using carbon atoms as catalytic sites instead of unsaturated coordinated metal atoms can make the electrocatalyst more stable and avoid the defects of metal dissolution and poisoning during the catalytic reaction. Using saturated coordinated metal atoms to regulate the carbon in the system p The center of the band can reduce the shortcomings of non-metallic catalysts such as poor activity and many side reactions. In addition, the loading of different metal atoms with saturated coordination can precisely control the selectivity of the reaction, which means that the system has good universality in catalysis.

Description

Technical Field

[0001] The present invention relates to the technical field of electrocatalysis, and in particular to a high-activity carbon atom site catalyst and a preparation method thereof. Background Art

[0002] Fuel cells and metal-air batteries are among the cleanest technologies for future portable electronics and transportation systems. However, the slow four-electron transfer process of the cathode oxygen reduction reaction (ORR) significantly limits the overall efficiency of the battery. Although platinum (Pt) and its alloys are currently considered the most efficient catalysts for ORR, their high cost and scarce reserves significantly hinder their large-scale commercial application. In this regard, the exploration of Earth-abundant, non-precious metal-based catalysts to replace Pt-based ORR counterparts is highly encouraged.

[0003] Non-noble metal-based electrocatalysts, metal-nitrogen / carbon (MNC, where M = Fe, Cu, Co, Ni, Mn, etc.) and their doped derivatives (MN / XC, where X = O, P, S, B, etc.) have been widely studied due to their advantages such as high atomic utilization efficiency, tunable electronic structure, and good activity. For example, Fe-NC-based catalysts containing unsaturated Fe-N4 sites have a good performance in the 4e - In the past decade, a lot of research has been devoted to optimizing the adsorption behavior of ORR intermediates by adjusting the electronic structure of the Fe center atom, such as adjusting the coordinated atomic species (Fe-N / S / OC), integrating multiple atomic active centers (Fe-MNC), and focusing on regulating the unsaturated coordinated Fe center. d orbitals, thereby regulating the catalytic activity of Fe metal atoms. However, if unsaturated coordinated metal atoms directly participate in the ORR reaction, the metal will dissolve in the solution during the adsorption and desorption process of oxygen, and the unsaturated coordinated metal is easily "poisoned". On the other hand, carbon-based metal-free catalysts do not have metal leaching, metal ion contamination and degradation related to Fenton-like reactions, so they have the natural advantage of good stability. The strategies for regulating sp2 carbon as an ORR active electrocatalyst mainly include: 1) chemical doping; 2) physical transfer of intermolecular charge; 3) structural defects. However, these regulation methods are imprecise and weak. At present, the catalytic activity of reported carbon-based metal-free catalysts is generally low, and side reactions are prone to occur. Summary of the Invention

[0004] The purpose of the present invention is to overcome the shortcomings and deficiencies of the prior art and to provide a highly active carbon atom site catalyst and a preparation method thereof.

[0005] The technical solutions adopted by the present invention are as follows:

[0006] A high-activity carbon atom site catalyst is obtained by high-temperature heat treatment of a precursor material obtained by mixing a mixed solution containing a transition metal salt and a zinc salt solution, washing, and drying.

[0007] A method for preparing a highly active carbon atom site catalyst comprises the following steps:

[0008] S1: adding a transition metal salt to a mixed solution of ammonia water, 2,3-pyridinedicarboxylic acid and water;

[0009] S2: dissolving a certain amount of zinc salt in anhydrous ethanol to obtain a zinc-ethanol solution, slowly pouring the solution obtained in step S1 into the zinc-ethanol solution, reacting for a certain period of time, centrifuging, washing, and drying to obtain a complex precursor material;

[0010] S3: subjecting the complex precursor material obtained in step S2 to high-temperature heat treatment under an inert atmosphere to obtain the highly active carbon atom site catalyst.

[0011] Preferably, in step S1, the transition metal salt is one or more of sulfates, chlorides, and ammonium salts of transition metals, and the transition metal is one or more of iron, cobalt, nickel, manganese, chromium, copper, ruthenium, palladium, and platinum.

[0012] Preferably, in step S1, the concentration of the transition metal salt in the mixed solution is 0.002-0.04 mol / L, the concentration of aqueous ammonia in the mixed solution is 0.04-1.6 mol / L, and the concentration of 2,3-pyridinedicarboxylic acid in the mixed solution is 0.02-0.8 mol / L.

[0013] Preferably, in step S1, the mixed solution further contains an oxygen-containing acid salt.

[0014] Preferably, the oxyacid salt is one or more oxyacid salts of transition metals / non-metals containing one or more oxygen atoms.

[0015] Preferably, the oxygen-containing acid salt is one or more of ammonium sulfate, diammonium hydrogen phosphate, ammonium dihydrogen phosphate, and ammonium molybdate.

[0016] Preferably, the concentration of the oxygen-containing salt in the mixed solution is 0-0.04 mol / L.

[0017] Preferably, in step S2, the zinc salt is dissolved in anhydrous ethanol and stirred in a water bath at a constant temperature of 10-80° C., and the reaction time is 0.5-4 h.

[0018] Preferably, in step S2, the precursor drying temperature is 40-80° C., and the drying time is 8-12 hours.

[0019] Preferably, in step S3, the heat treatment temperature is 900-1050° C., and the time is 0.5-2 h.

[0020] The beneficial effects of the present invention are as follows:

[0021] The present invention provides a method for preparing a catalyst with carbon as the catalytic active site, mainly by regulating the surrounding carbon atoms through saturated coordination of single atoms p The center of the carbon atom makes the carbon atom site have high efficiency in electrocatalytic oxygen reduction reaction activity;

[0022] The doped carbon catalyst containing 0.2~5 wt% saturated coordinated single atoms was synthesized by simple co-precipitation and high temperature pyrolysis. The synthesis method is simple. In addition, the use of carbon atoms as catalytic sites instead of unsaturated coordinated metal atoms can make the electrocatalyst more stable and avoid the defects of metal dissolution and poisoning during the catalytic reaction. The use of saturated coordinated metal atoms to regulate the carbon in the system p The center of the band can reduce the shortcomings of non-metallic catalysts such as poor activity and many side reactions. In addition, the loading of different metal atoms with saturated coordination can precisely control the selectivity of the reaction, which means that the system has good universality in catalysis. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, without paying any creative work, other drawings obtained based on these drawings still fall within the scope of the present invention.

[0024] Figure 1 This is the X-ray diffraction pattern of the complex precursor prepared in Example 1 of the present invention;

[0025] Figure 2 This is the X-ray diffraction pattern of the catalyst prepared in Example 1 of the present invention;

[0026] Figure 3 This is a scanning electron microscope image of the catalyst prepared in Example 1 of the present invention;

[0027] Figure 4 The local coordination analysis of the iron atom of the catalyst prepared in Example 1 of the present invention;

[0028] Figure 5 This is the linear sweep voltammetry curve of the catalyst prepared in Example 1 of the present invention;

[0029] Figure 6 The ORR catalytic performance of each catalyst prepared in the present invention is compared. DETAILED DESCRIPTION

[0030] In order to make the objectives, technical solutions and advantages of the present invention more clear, the present invention will be described in further detail below with reference to the accompanying drawings.

[0031] In Example 1-13, a saturated iron atom-loaded and sulfur / nitrogen co-doped carbon catalyst was prepared by pyrolysis of an iron / sulfur-doped rod-shaped zinc-quinoline coordination polymer precursor. The preparation method is as follows:

[0032] S1: Prepare a 10 ml mixed solution by mixing 0.5 mL of ammonia water, 0.40 g of 2,3-pyridinedicarboxylic acid, and water. Add a certain amount of ferrous ammonium sulfate hexahydrate to the solution, seal the container, and stir evenly.

[0033] S2: Dissolve 1.40 g of zinc nitrate in 30 ml of anhydrous ethanol solution and stir uniformly in a water bath at a constant temperature to obtain a zinc-ethanol solution. Slowly pour the solution obtained in step S1 into the zinc-ethanol solution, react for 0.5 h, and then centrifuge, wash, and dry to obtain an iron-sulfur-doped rod-shaped zinc-quinoline coordination polymer.

[0034] S3: The obtained complex was heat treated under Ar protection at 5°C·min -1 The temperature was raised to the pyrolysis temperature at a rate of 10000 ℃ and then naturally cooled to obtain the carbon catalyst FeO6-N2-SC.

[0035] Table 1 shows the mass, pyrolysis temperature and pyrolysis time of ammonium ferrous sulfate hexahydrate added in Examples 1-13:

[0036]

[0037] like Figure 1 Shown is the XRD spectrum of the iron-sulfur doped rod-shaped zinc-quinoline coordination polymer, which is consistent with the crystal form of the zinc-quinoline coordination polymer. Figure 2 The XRD spectrum of the carbon catalyst FeO6-N2-SC obtained by pyrolysis shows that no characteristic peaks of metal particles were observed. Figure 3 The SEM image shows that the morphology of the carbon catalyst FeO6-N2-SC is long and thin leaf-like. Figure 4 This is the local coordination analysis of the iron atoms in the FeO6-N2-SC catalyst. The Fe element in the catalyst is loaded on the carbon material in a saturated coordinated and monodispersed form. Figure 5 The linear sweep voltammetry curves show that the catalyst has excellent ORR performance.

[0038] By rationally designing the coordinated saturated iron single atoms (FeO6) and introducing external N / S dopants into the carbon matrix, the prepared FeO6-N2-SC nanorods have good ORR performance, a half-wave potential of 0.895 V, four-electron path selectivity and excellent long-term catalytic stability. The catalyst has high industrial application prospects.

[0039] In Examples 13-16, a saturated iron atom-loaded and sulfur / nitrogen co-doped carbon catalyst was prepared by pyrolysis of an iron / phosphorus-doped rod-shaped zinc-quinoline coordination polymer precursor. The preparation method is as follows:

[0040] S1: Prepare a 10 ml mixed solution by mixing 0.5 mL of ammonia water, 0.40 g of 2,3-pyridinedicarboxylic acid, and water. Add a certain amount of ferrous chloride tetrahydrate and diammonium hydrogen phosphate to the solution.

[0041] S2: Dissolve 1.40 g of zinc nitrate in 30 ml of anhydrous ethanol solution and stir in a water bath at a constant temperature to obtain a zinc-ethanol solution. Slowly pour the solution obtained in step S1 into the zinc-ethanol solution, react for 0.5 h, centrifuge, wash, and dry to obtain an iron-phosphorus-doped rod-shaped zinc-quinoline coordination polymer.

[0042] S3: The obtained complex was heat treated under Ar protection at 5°C·min -1 The temperature was raised to the pyrolysis temperature at a rate of 10000 ℃ and then naturally cooled to obtain the carbon catalyst FeO6-N2-PC.

[0043] Table 2 shows the mass, pyrolysis temperature and pyrolysis time of ferrous chloride tetrahydrate and diammonium hydrogen phosphate added in Examples 13-16:

[0044]

[0045] In Examples 16-23, a platinum-doped rod-shaped zinc-quinoline coordination polymer precursor was thermally decomposed to prepare a catalyst loaded with saturated coordinated platinum atoms and nitrogen-doped carbon. The preparation method is as follows:

[0046] S1: Prepare a 10 ml mixed solution of 0.5 mL ammonia water, 0.40 g 2,3-pyridinedicarboxylic acid, and water, and add a certain amount of platinum chloride to the solution;

[0047] S2: Dissolve 1.40 g of zinc nitrate in 30 ml of anhydrous ethanol solution and stir in a water bath at a constant temperature to obtain a zinc-ethanol solution. Slowly pour the solution obtained in step S1 into the zinc-ethanol solution, react for 0.5 h, and then centrifuge, wash, and dry to obtain a platinum-doped rod-shaped zinc-quinoline coordination polymer.

[0048] S3: The obtained complex was heat treated under Ar protection at 5°C·min-1 The temperature was raised to the pyrolysis temperature at a rate of 10000 ℃ and then naturally cooled to obtain the carbon catalyst PtO6-N2-C.

[0049] Table 3 shows the mass, pyrolysis temperature and pyrolysis time of platinous chloride added in Examples 16-23:

[0050]

[0051] In Examples 24-33, copper / sulfur-doped rod-shaped zinc-based quinoline coordination polymers were thermally decomposed to prepare carbon catalysts loaded with saturated coordinated copper atoms and nitrogen / sulfur co-doped. The preparation method is as follows:

[0052] S1: Prepare a 10 ml mixed solution of 0.5 mL ammonia water, 0.40 g 2,3-pyridinedicarboxylic acid, and water. Add a certain amount of copper sulfate pentahydrate to the solution.

[0053] S2: Dissolve 1.40 g of zinc nitrate in 30 ml of anhydrous ethanol solution and stir in a water bath at a constant temperature to obtain a zinc-ethanol solution. Slowly pour the solution obtained in step S1 into the zinc-ethanol solution, react for 0.5 h, and then centrifuge, wash, and dry to obtain a copper / sulfur-doped rod-shaped zinc-based quinoline coordination polymer.

[0054] S3: The obtained complex was heat treated under Ar protection at 5°C·min -1 The temperature was raised to the pyrolysis temperature at a rate of , and then naturally cooled to obtain the carbon catalyst CuO6-N2-SC.

[0055] Table 4 shows the mass, pyrolysis temperature and pyrolysis time of platinous chloride added in Examples 24-33:

[0056]

[0057] As can be seen from the above examples, a doped carbon catalyst with highly adjustable doping elements can be prepared by using a rod-shaped zinc-based pyridine dicarboxylic acid coordination polymer doped with different elements as a precursor and then subjecting it to high-temperature heat treatment. The synthesis method is simple and has good reproducibility, indicating that this method has high industrial application value.

[0058] like Figure 6 As shown, the ORR catalytic performance of each catalyst prepared in the present invention is compared, which proves that the selectivity of the reaction can be precisely controlled by loading different metal atoms with saturated coordination.

[0059] The above disclosure is merely a preferred embodiment of the present invention and certainly cannot be used to limit the scope of the present invention. Therefore, equivalent changes made according to the claims of the present invention are still within the scope of the present invention.

Claims

1. A method for preparing a highly active carbon atom site catalyst, characterized in that: The following steps are involved: S1: adding a transition metal salt to a mixed solution of ammonia water, 2,3-pyridinedicarboxylic acid and water; S2: dissolving a certain amount of zinc salt in anhydrous ethanol to obtain a zinc-ethanol solution, slowly pouring the solution obtained in step S1 into the zinc-ethanol solution, reacting for a certain period of time, centrifuging, washing, and drying to obtain a complex precursor material; S3: subjecting the complex precursor material obtained in step S2 to a high-temperature heat treatment under an inert atmosphere to obtain the high-activity carbon atom site catalyst, wherein the high-activity carbon atom site catalyst has saturated coordinated metal atoms and uses high-activity carbon atoms as catalytic sites; In step S1, the transition metal salt is one or more of sulfate, chloride, and ammonium salt of a transition metal, and the transition metal is one or more of iron, cobalt, nickel, manganese, chromium, copper, ruthenium, palladium, and platinum.

2. The method for preparing a highly active carbon atom site catalyst according to claim 1, wherein: In step S1, the concentration of the transition metal salt in the mixed solution is 0.002-0.04 mol / L, the concentration of aqueous ammonia in the mixed solution is 0.04-1.6 mol / L, and the concentration of 2,3-pyridinedicarboxylic acid in the mixed solution is 0.02-0.8 mol / L.

3. The method for preparing a highly active carbon atom site catalyst according to claim 1, wherein: In step S1, the mixed solution also contains an oxygen-containing acid salt.

4. The method for preparing a highly active carbon atom site catalyst according to claim 3, wherein: The oxyacid salt is one or more oxyacid salts of transition metals / non-metals containing one or more oxygen atoms.

5. The method for preparing a highly active carbon atom site catalyst according to claim 4, characterized in that: The oxygen-containing acid salt is one or more of ammonium sulfate, diammonium hydrogen phosphate, ammonium dihydrogen phosphate, and ammonium molybdate.

6. The method for preparing a highly active carbon atom site catalyst according to claim 3, wherein: The concentration of the oxygen-containing salt in the mixed solution is c1, 0<c1≤0.04 mol / L.

7. The method for preparing a highly active carbon atom site catalyst according to any one of claims 1 to 6, characterized in that: In step S2, the zinc salt is dissolved in anhydrous ethanol and stirred in a water bath at a constant temperature of 10-80° C., and the reaction time is 0.5-4 h.

8. The method for preparing a highly active carbon atom site catalyst according to any one of claims 1 to 6, characterized in that: In step S2, the precursor drying temperature is 40-80°C, and the drying time is 8-12 hours.

9. The method for preparing a high-activity carbon atom site catalyst according to any one of claims 1 to 6, characterized in that: In step S3, the heat treatment temperature is 900-1050° C., and the time is 0.5-2 h.

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