阅读说明：本技术 一种复合MnZn单原子碳基氧还原催化剂的制备方法 (Preparation method of composite MnZn single-atom carbon-based oxygen reduction catalyst ) 是由 田植群 张潇然 王运秋 沈培康 于 2021-08-30 设计创作，主要内容包括：本发明公开了一种复合MnZn复合氮掺杂碳基氧还原电催化剂的制备方法：(1)制备含氮聚合物前驱体；(2)将锰、锌金属盐按照不同的摩尔比例与前驱体络合,络合后所得物质干燥,得到固体混合物；(3)高温处理：第一次高温热解,冷却至室温,得到MnZn单原子氮共掺杂碳材料；(4)第二次高温热裂解,得到MnZn单原子氮共掺杂碳材料粉体,即为复合MnZn复合氮掺杂碳基氧还原电催化剂。本发明方法具有操作简单,生产成本低,可控性好,可以对Mn,Zn双金属单原子的掺杂含量和比例进行调控,易于工业化生产等优点,易于结构设计形状自由度高,是一种非常优异的复合MnZn复合氮掺杂碳基氧还原电催化剂的制备方法。(The invention discloses a preparation method of a composite MnZn composite nitrogen-doped carbon-based oxygen reduction electrocatalyst, which comprises the following steps: (1) preparing a nitrogen-containing polymer precursor; (2) complexing manganese and zinc metal salts with a precursor according to different molar ratios, and drying substances obtained after complexing to obtain a solid mixture; (3) high-temperature treatment: carrying out high-temperature pyrolysis for the first time, and cooling to room temperature to obtain a MnZn monatomic nitrogen co-doped carbon material; (4) and performing high-temperature thermal cracking for the second time to obtain MnZn monatomic nitrogen co-doped carbon material powder, namely the composite MnZn composite nitrogen-doped carbon-based oxygen reduction electrocatalyst. The method has the advantages of simple operation, low production cost, good controllability, capability of regulating and controlling the doping content and proportion of the bimetallic atoms of Mn and Zn, easiness for industrial production and the like, is easy to realize high freedom degree of structural design and shape, and is a preparation method of the excellent composite MnZn composite nitrogen-doped carbon-based oxygen reduction electrocatalyst.)

1. A preparation method of a composite MnZn composite nitrogen-doped carbon-based oxygen reduction electrocatalyst is characterized by comprising the following operation steps of:

(1) preparing a nitrogen-containing polymer precursor;

(2) complexing manganese and zinc metal salts with the nitrogen-containing polymer precursor obtained in the step (1) according to different molar ratios, and drying substances obtained after complexing to obtain a solid mixture; the molar ratio of the manganese metal salt to the zinc metal salt is 1: 5-5: 1;

(3) high-temperature treatment: carrying out first high-temperature pyrolysis on the solid mixture obtained in the step (2) under the protection of protective atmosphere, and cooling to room temperature to obtain a MnZn monatomic nitrogen co-doped carbon material;

(4) acid pickling treatment: and (4) pickling the MnZn monatomic nitrogen co-doped carbon material obtained in the step (3), filtering, drying, and performing secondary high-temperature thermal cracking on the powder obtained after drying to obtain MnZn monatomic nitrogen co-doped carbon material powder, namely the composite MnZn composite nitrogen-doped carbon-based oxygen reduction electrocatalyst.

2. The method of claim 1, wherein: the preparation of the nitrogen-containing polymer precursor in the step (1) is to perform sufficient dehydration condensation reaction on 2, 6-diacetylpyridine according to a molar ratio of 10:1 and ethanol as a solvent under the condition of an oxalic acid catalyst.

3. The method of claim 1, wherein: the manganese metal salt in the step (1) is manganese chloride; the zinc metal salt is zinc acetate.

4. The method of claim 1, wherein: the manganese metal salt and the zinc metal salt in the step (2) are respectively obtained by dissolving in an ethanol solvent and then mixing.

5. The method of claim 1, wherein: and (3) the protective atmosphere is a gas mixed by inert gas and hydrogen.

6. The method of claim 1, wherein: in the step (3), the high-temperature pyrolysis in the step (4) is carried out for 1h at 900 ℃.

7. The method of claim 1, wherein: the step (4) of acid washing is to disperse the MnZn monatomic nitrogen co-doped carbon material to 0.5M H₂SO₄Heating the solution to 80 deg.C, and magnetically stirring for 10 hr.

Technical Field

The invention relates to a novel MnZn atom composite nitrogen-doped carbon-based non-noble metal catalyst, in particular to a preparation method of a composite MnZn single-atom carbon-based oxygen reduction catalyst.

Background

The cathode oxygen reduction reaction is the core reaction of low temperature Fuel Cells (FCs) and metal air cells (MABs)In one aspect, the reaction process involves a multi-step four electron transfer process resulting in a kinetic reaction that is relatively slow compared to the anodic reaction. To date, the most widely used Oxygen Reduction Reaction (ORR) catalyst is a platinum (Pt) -based noble metal catalyst. However, platinum is a low-cost precious metal, which has severely hampered the commercial application of fuel cell technology. In such cases, it is highly desirable to develop alternatives to low cost platinum-based noble metal catalysts. The transition metal coordination nitrogen-doped carbon-based catalyst (M-N-C) is widely researched and rapidly developed due to good catalytic performance, and active sites of the transition metal coordination nitrogen-doped carbon-based catalyst mainly comprise MN_xC_yMetal carbide, metal nitride, etc., wherein MN_xC_yThe active site has the highest ORR activity. This site readily activates O₂And the energy barrier of the O ═ O bond is broken with relatively low energy, promoting ORR catalytic activity. In fact, the nature of the transition metal in M-N-C also affects O₂And other ORR intermediates in MN_xC_yThe bonds at the sites can cause differences in activity and durability. The M-N-C catalyst reported at present mainly comprises Fe and Co, and particularly the catalytic activity of Fe-N-C is close to the level of a Pt/C catalyst, and represents the latest development level of a non-noble metal catalyst. However, improving the durability of Fe-N-C in an electrochemical oxidation environment is a great challenge. Fe dissolved in catalyst²⁺Can be reacted with H₂O₂(by-product of ORR) reaction generates strong oxidizing radicals, which not only decompose the fuel cell membrane, but also attack the catalyst itself, leading to rapid device failure, and therefore, the development of a highly active iron-free ORR catalyst is essential. Manganese ions, unlike iron and cobalt ions, and H₂O₂The reactivity therebetween is low, and it is difficult to generate hydroxyl radicals by fenton reaction. The density functional theory calculation shows that MnN₄The active site is expected to be obtained together with FeN₄Reports on the comparable ORR activity of the active site suggest that it has the potential to replace iron-based ORR catalysts. Although studies of Mn-N-C catalysts have been widely reported, it is noteworthy that the current Mn-N-C catalysts still have catalytic activity comparable to commercial platinum-carbon catalystsThe differentiation of the agents is enormous. However, relevant studies show that the catalytic activity and selectivity can be further optimized in the ORR reaction of the catalyst with bimetallic or multi-metallic active sites. The structure formed by the coordination of the bimetallic atom to the nitrogen atom is more favorable to O than a single metal site₂Cleavage of the bond. The interaction between the electronic structures can optimize the structure, so that the adsorption and desorption of the reaction intermediate reach a proper state, and the catalyst has higher catalytic activity. Therefore, the exploration of new metal components and catalytic sites to develop efficient Mn-N-C group, multi-metal atom composite nitrogen-doped carbon-based oxygen reduction catalysts is very urgent.

Disclosure of Invention

In order to overcome the defects of the prior art, the invention develops a novel composite MnZn atomic nitrogen-doped carbon-based oxygen reduction electrocatalyst material to solve the problems of low activity and poor stability of a transition metal monatomic nitrogen-doped carbon material in the prior art. The invention adopts a method of directly pyrolyzing 2,6 diaminopyridine to complex Mn and Zn precursors, and can prepare a novel composite MnZn single-atom carbon-based oxygen reduction electrocatalyst material with uniform appearance and adjustable electrochemical performance after high-temperature treatment.

In order to achieve the purpose, the technical scheme provided by the invention is as follows:

a preparation method of a composite MnZn composite nitrogen-doped carbon-based oxygen reduction electrocatalyst comprises the following operation steps:

(1) preparing a nitrogen-containing polymer precursor;

(2) complexing manganese and zinc metal salts with the nitrogen-containing polymer precursor obtained in the step (1) according to different molar ratios, and drying substances obtained after complexing to obtain a solid mixture; the molar ratio of the manganese metal salt to the zinc metal salt is 1: 5-5: 1;

(3) high-temperature treatment: carrying out first high-temperature pyrolysis on the solid mixture obtained in the step (2) under the protection of protective atmosphere, and cooling to room temperature to obtain a MnZn monatomic nitrogen co-doped carbon material;

(4) acid pickling treatment: and (4) pickling the MnZn monatomic nitrogen co-doped carbon material obtained in the step (3), filtering, drying, and performing secondary high-temperature thermal cracking on the powder obtained after drying to obtain MnZn monatomic nitrogen co-doped carbon material powder, namely the composite MnZn composite nitrogen-doped carbon-based oxygen reduction electrocatalyst.

Preferably, the nitrogen-containing polymer precursor is prepared in step (1) by sufficiently performing a dehydration condensation reaction of 2, 6-diacetylpyridine in a molar ratio of 10:1 in an ethanol solvent under an oxalic acid catalyst.

Preferably, the manganese metal salt in the step (1) is manganese chloride; the zinc metal salt is zinc acetate.

Preferably, the manganese metal salt and the zinc metal salt in the step (2) are respectively obtained by dissolving in an ethanol solvent and then mixing.

Preferably, the protective atmosphere in step (3) is a mixture of an inert gas and hydrogen.

Preferably, the high-temperature pyrolysis in the step (3), the step (4) and the high-temperature pyrolysis are all pyrolysis at 900 ℃ for 1 hour.

Preferably, the acid washing in the step (4) is to disperse the MnZn monatomic nitrogen-co-doped carbon material to 0.5M H₂SO₄Heating the solution to 80 deg.C, and magnetically stirring for 10 hr.

In the system, the prepared composite MnZn composite nitrogen-doped carbon-based oxygen reduction electrocatalyst is prepared, and according to a TEM test result, Mn and Zn exist in a single-atom form and are uniformly dispersed in carbon spheres; the nitrogen content is 4at percent to 5at percent, and the single atom content of Mn and Zn is 0.1 to 0.5at percent; the composite MnZn composite nitrogen-doped carbon-based oxygen reduction electrocatalyst shows excellent oxygen reduction catalytic activity, the initial potential of the catalyst is 1.0V in 0.1M KOH solution, the corresponding half-wave potential of the catalyst is 0.90V which is superior to that of a commercial platinum-carbon catalyst, and meanwhile, the composite MnZn composite nitrogen-doped carbon-based oxygen reduction electrocatalyst shows good circulation stability and provides a basis for wide commercial application.

Compared with the prior art, the invention has the following beneficial effects:

the composite MnZn composite nitrogen-doped carbon-based oxygen reduction electrocatalyst prepared by the method is used as a high-efficiency oxygen reduction catalyst, is different from a conventional single-metal atom-doped oxygen reduction catalyst material, shows better catalytic activity compared with a single-metal single-atom carbon material, is far higher than the catalytic activity and stability of commercial platinum carbon, and provides a good basis for wide commercial application; furthermore, the method has the advantages of simple operation, low production cost, good controllability, capability of regulating and controlling the doping content and proportion of the bimetallic atoms of Mn and Zn, easiness for industrial production and the like, is easy for structural design, has high degree of freedom of shape and is a very excellent preparation method of the composite MnZn composite nitrogen-doped carbon-based oxygen reduction electrocatalyst.

Drawings

FIG. 1 is a TEM image of a MnZn composite N-doped C-based oxygen-reducing electrocatalyst prepared in example 1 of the present invention; (a) and (b) are graphs of different multiples, respectively.

FIG. 2 is an XRD and Raman spectrum of the composite Mn monatomic carbon material prepared in example 1 of the present invention; (a) and (b) are graphs of different multiples, respectively.

Fig. 3(a) is an XRD pattern of the composite Mn monatomic carbon material prepared in example 1, example 2, and example 3 of the present invention, and (b) is a raman photograph of the composite Mn monatomic carbon material prepared in example 1 of the present invention.

FIG. 4 is a specific surface and pore size distribution diagram of a composite Mn monatomic carbon material prepared in example 1, example 2 or example 3 of the present invention; (a) is a nitrogen adsorption and desorption isotherm diagram, and (b) a pore diameter distribution diagram.

FIG. 5 shows the synchrotron radiation of the composite MnZn composite N-doped C-based oxygen reduction electrocatalyst prepared in example 1, example 2 and example 3; (a) a near-edge absorption spectrum, and (b) an extended-edge absorption spectrum.

FIG. 6 is a graph showing oxygen evolution performance of the composite MnZn composite nitrogen-doped carbon-based oxygen reduction electrocatalyst prepared in example 1, example 2 or example 3 of the present invention; (a) is the LSV plot, and (b) is the Tafel slope curve.

FIG. 7 is a scanning electron micrograph of the composite MnZn composite N-doped C-based oxygen reduction electrocatalyst prepared in example 2 of the present invention; (a) is the LSV plot, and (b) is the stability plot.

Detailed Description

The following detailed description is to be read in connection with the accompanying drawings, but it is to be understood that the scope of the invention is not limited to the specific embodiments. The raw materials and reagents used in the examples were all commercially available unless otherwise specified.

Example 1

A preparation method of a composite MnZn composite nitrogen-doped carbon-based oxygen reduction electrocatalyst comprises the following operation steps:

(1) preparation of a nitrogen-containing polymer precursor: sequentially dissolving 2, 6-diacetylpyridine (DMP, 0.6g) and oxalic acid (0.01g, catalyst) in 55mL of ethanol to obtain a mixed solution, and placing the mixed solution on a magnetic stirrer at room temperature for dehydration condensation reaction for 12 hours to form a dark yellow precursor;

(2) 1.06g of manganese chloride (MnCl)₂·4H₂O, same molar as 2,6 diacetylpyridine) and 0.875g of zinc acetate (Zn (CH)₃COO)₂) Respectively dissolving in 10mL of ethanol, simultaneously injecting into the dark yellow precursor obtained in the step (1), stirring for 12 hours at room temperature until substances are separated out, separating out the precipitate by using a vacuum adsorption filter, and drying in a vacuum oven at 80 ℃ for 10 hours to obtain a solid mixture;

(3) high-temperature treatment: subjecting the solid mixture obtained in step (4) to argon and H at 900 DEG C₂(5％H₂) Carrying out first pyrolysis for 1h (5 ℃/min) in a mixed gas environment, and cooling to room temperature to obtain a MnZn monatomic nitrogen co-doped carbon material;

(4) acid pickling treatment: dispersing the MnZn monatomic nitrogen co-doped carbon material obtained in the step (3) to 0.5M H₂SO₄Heating the solution to 80 deg.C, magnetically stirring for 10 hr to remove unstable metal substances, filtering, drying the solid obtained after filtering, and adding Ar and H₂(5％H₂) And carrying out second pyrolysis for 1h at 900 ℃ under the condition of mixed atmosphere to obtain the final Mn/Zn-N-C-1 catalyst, wherein the molar ratio of Mn to Zn is 1: 0.25, namely the composite MnZn composite nitrogen-doped carbon-based oxygen reduction electrocatalyst.

Example 2

A preparation method of a composite MnZn composite nitrogen-doped carbon-based oxygen reduction electrocatalyst comprises the following operation steps:

(1) preparation of a nitrogen-containing polymer precursor: sequentially dissolving 2, 6-diaminopyridine (DMP, 0.6g) and oxalic acid (0.01g, catalyst) in 55mL of ethanol to obtain a mixed solution, and placing the mixed solution on a magnetic stirrer at room temperature for dehydration condensation reaction for 12 hours to form a dark yellow precursor;

(2) 1.06g of manganese chloride (MnCl)₂·4H₂O, same moles as 2,6 diacetylpyridine) with 1.635g of zinc acetate (Zn (CH)₃COO)₂) Respectively dissolving in 10mL of ethanol, simultaneously injecting into the dark yellow precursor obtained in the step (1), stirring for 12 hours at room temperature until substances are separated out, separating out the precipitate by using a vacuum adsorption filter, and drying in a vacuum oven at 80 ℃ for 10 hours to obtain a solid mixture;

(3) high-temperature treatment: subjecting the solid mixture obtained in step (4) to argon and H at 900 DEG C₂(5％H₂) Carrying out first pyrolysis for 1h (5 ℃/min) in a mixed gas environment, and cooling to room temperature to obtain a MnZn monatomic nitrogen co-doped carbon material;

(4) acid pickling treatment: dispersing the MnZn monatomic nitrogen co-doped carbon material obtained in the step (3) to 0.5M H₂SO₄Heating the solution to 80 deg.C, magnetically stirring for 10 hr to remove unstable metal substances, filtering, drying the solid obtained after filtering, and adding Ar and H₂(5％H₂) And carrying out second pyrolysis for 1h at 900 ℃ under the condition of mixed atmosphere to obtain the final Mn/Zn-N-C-2 catalyst, wherein the molar ratio of Mn to Zn is 1: 1, namely the composite MnZn composite nitrogen-doped carbon-based oxygen reduction electrocatalyst.

Example 3

A preparation method of a composite MnZn composite nitrogen-doped carbon-based oxygen reduction electrocatalyst comprises the following operation steps:

(1) preparation of a nitrogen-containing polymer precursor: sequentially dissolving 2, 6-diaminopyridine (DMP, 0.6g) and oxalic acid (0.01g, catalyst) in 55mL of ethanol to obtain a mixed solution, and placing the mixed solution on a magnetic stirrer at room temperature for dehydration condensation reaction for 12 hours to form a dark yellow precursor;

(2) 1.06g of manganese chloride (MnCl)₂·4H₂O, same moles as 2,6 diacetylpyridine) with 2.069g of zinc acetate (Zn (CH)₃COO)₂) Respectively dissolving in 10mL of ethanol, simultaneously injecting into the dark yellow precursor obtained in the step (1), stirring for 12 hours at room temperature until substances are separated out, separating out the precipitate by using a vacuum adsorption filter, and drying in a vacuum oven at 80 ℃ for 10 hours to obtain a solid mixture;

(3) high-temperature treatment: subjecting the solid mixture obtained in step (4) to argon and H at 900 DEG C₂(5％H₂) Carrying out first pyrolysis for 1h (5 ℃/min) in a mixed gas environment, and cooling to room temperature to obtain a MnZn monatomic nitrogen co-doped carbon material;

(4) acid pickling treatment: dispersing the MnZn monatomic nitrogen co-doped carbon material obtained in the step (3) to 0.5M H₂SO₄Heating the solution to 80 deg.C, magnetically stirring for 10 hr to remove unstable metal substances, filtering, drying the solid obtained after filtering, and adding Ar and H₂(5％H₂) And carrying out second pyrolysis for 1h at 900 ℃ under the condition of mixed atmosphere to obtain the final Mn/Zn-N-C-3 catalyst, wherein the molar ratio of Mn to Zn is 11.5, and the final Mn/Zn composite nitrogen-doped carbon-based oxygen reduction electrocatalyst is obtained.

FIG. 1 is a Scanning Electron Microscope (SEM) image of a product obtained in example 1, and it can be seen that the prepared MnZn double-monatomic nitrogen-doped carbon material has a spherical morphology structure.

Fig. 2 is an XRD and raman spectrum of the composite Mn monatomic carbon material prepared in example 1 of the present invention, from which it is apparent that Mn and Zn are uniformly dispersed in the form of monatomic atoms inside the carbon sphere.

Fig. 3 is an XRD pattern and Raman photograph of the products obtained in examples 1, 2, and 3, showing that the MnZn diatomic nitrogen doped carbon material has an amorphous carbon structure.

FIG. 4 is a specific surface area and pore size distribution diagram of products obtained in examples 1, 2 and 3, and shows that the MnZn double monatomic nitrogen-doped carbon material has a high specific surface area and a hierarchical pore structure.

Fig. 5 is the synchrotron radiation characterization of the products obtained in examples 1, 2 and 3, and verifies that the MnZn nitrogen-doped carbon material has a Mn, Zn double-monoatomic doping structure.

FIG. 6 is a graph of the electrochemical performance of the products obtained in examples 1, 2 and 3 under alkaline conditions (0.1MKOH), and it is obvious that the three examples are different in that different proportions of Mn and Zn are simply adjusted to have different oxygen reduction catalytic activities.

FIG. 7 shows the product obtained in example 2 under acidic conditions (0.5 MH)₂SO₄) The electrochemical performance graph shows that the catalyst shows catalytic activity equivalent to Pt/C, and meanwhile, the catalyst has good stability through 10000 cycles of cycle stability test.

The foregoing descriptions of specific exemplary embodiments of the present invention have been presented for purposes of illustration and description. It is not intended to limit the invention to the precise form disclosed, and obviously many modifications and variations are possible in light of the above teaching. The exemplary embodiments were chosen and described in order to explain certain principles of the invention and its practical application to enable one skilled in the art to make and use various exemplary embodiments of the invention and various alternatives and modifications as are suited to the particular use contemplated. It is intended that the scope of the invention be defined by the claims and their equivalents.