阅读说明：本技术 一种自生长碳管复合zif-8氧还原电催化剂 (Self-growing carbon tube composite ZIF-8 oxygen reduction electrocatalyst ) 是由 朱威 马猛猛 庄仲滨 于 2019-11-01 设计创作，主要内容包括：本发明涉及一种运用催化法形成碳管的策略制备碳管复合ZIF?8纳米材料用于氧还原反应的非贵金属电催化剂。在合成ZIF?8的过程中添加适量铁源形成铁负载的ZIF?8，然后通过冷冻干燥法再添加一部分铁源，最后通过高温碳化，一部分铁源形成Fe?N<Sub>x</Sub>?C位点，另一部分铁源催化形成碳管，从而一步法得到碳管与ZIF?8的复合催化材料。本方法采用外加铁源的方法，在碳化阶段同时形成活性位点和碳管。该方法简单高效，廉价可靠，制备的催化剂同时具有ZIF基催化剂的高活性和碳管的高稳定性，具备一定的商业价值。(The invention relates to a non-noble metal electrocatalyst for preparing a carbon tube composite ZIF-8 nano material for an oxygen reduction reaction by using a strategy of forming a carbon tube by a catalytic method. Adding a proper amount of iron source to form iron-loaded ZIF-8 in the process of synthesizing ZIF-8, then adding a part of iron source through a freeze-drying method, and finally carbonizing at high temperature to form Fe-N from a part of iron source x And the other part of the iron source catalyzes and forms a carbon tube, so that the composite catalytic material of the carbon tube and ZIF-8 is obtained by a one-step method. The method adopts a method of adding an iron source, and forms an active site and a carbon tube simultaneously in a carbonization stage. The method is simple, efficient, cheap and reliable, and the prepared catalyst has the high activity of the ZIF-based catalyst and the carbon tubeHigh stability and certain commercial value.)

1. A preparation process of a self-growing carbon tube composite ZIF-8 oxygen reduction electrocatalyst comprises the following steps:

step 1) dimethyl imidazole, zinc nitrate hexahydrate and ferric salt are directly used for synthesizing evenly distributed ZIF-8, then a part of ferric salt and ZIF-8 are evenly mixed through a freeze-drying method, a certain amount of dimethyl imidazole is weighed and evenly stirred to be dispersed in a solvent to be named as A, a certain amount of zinc nitrate hexahydrate is weighed and then added into a certain amount of ferric salt, the mixture is evenly stirred to be dispersed in the solvent to be named as B, A and B are mixed at a certain temperature for reacting for a period of time, the mixture is washed by the solvent and filtered by suction to obtain sediment, ZIF with evenly distributed iron, nitrogen and carbon is obtained, then a part of iron source and ZIF-8 are evenly mixed through a freeze-drying method to obtain ZIF-8+ Fe,

and 2) transferring the uniformly mixed ZIF-8+ Fe into a porcelain boat, calcining the porcelain boat in a tubular furnace in an inert atmosphere at a certain temperature for a certain time, naturally cooling to room temperature, and further carrying out acid pickling to obtain the non-noble metal electrocatalyst for the oxygen reduction reaction.

2. The method of preparing a non-noble metal electrocatalyst for oxygen reduction reaction according to claim 1, wherein: the ferric salt in the step 1) can be one or two of ferric nitrate nonahydrate, ferric chloride hexahydrate, ammonium ferrous sulfate hexahydrate, ferrous sulfate, ferric sulfate, ferrous chloride tetrahydrate, ferrous acetate tetrahydrate, anhydrous ferrous chloride and anhydrous ferric chloride.

3. The method of preparing a non-noble metal electrocatalyst for oxygen reduction reaction according to claim 1, wherein: the molar ratio of the zinc nitrate hexahydrate and the dimethyl imidazole in the certain amount in the step 1) can be 1 (3-8).

4. The method of claim 1 for preparing a non-noble metal electrocatalyst for oxygen reduction reaction, wherein: the solvent for dispersing the dimethyl imidazole 16563in the step 1) can be one or two of methanol, ethanol, deionized water, N-dimethylformamide and N, N-dimethylacetamide.

5. The method of preparing a non-noble metal electrocatalyst for oxygen reduction reaction according to claim 1, wherein: the solvent for dispersing the zinc nitrate hexahydrate and the ferric salt in the step 1) can be one or two of methanol, ethanol, deionized water, N-dimethylformamide and N, N-dimethylacetamide.

6. The method of claim 1 for preparing a non-noble metal electrocatalyst for acidic oxygen reduction reaction, wherein: the mixing in step 1) may be 20-80 ℃ at a certain temperature.

7. The method of claim 1 for preparing a non-noble metal electrocatalyst for acidic oxygen reduction reaction, wherein: the reaction time in step 1) may be 4 to 24 hours.

8. The method of claim 1 for preparing a non-noble metal electrocatalyst for acidic oxygen reduction reaction, wherein: the solvent used in the suction filtration in the step 1) can be one or two of methanol, ethanol, deionized water, N-dimethylformamide and N, N-dimethylacetamide.

9. The method of claim 1 for preparing a non-noble metal electrocatalyst for acidic oxygen reduction reaction, wherein: the inert gas introduced into the high-temperature tube furnace in the step 2) can be argon or nitrogen, and the gas flow can be 30-120ml/min.

10. The method of claim 1 for preparing a non-noble metal electrocatalyst for acidic oxygen reduction reaction, wherein: in the step 2), the calcining process in the high-temperature tubular furnace is a calcining process, wherein the temperature is increased to 150-250 ℃ at the speed of 1-10 ℃/min, and the temperature is kept for 0.5-3.0 hours; then the temperature is raised to 800-1000 ℃ at the speed of 1-5 ℃/min, and the temperature is preserved for 0.5-3.0 hours.

Technical Field

The invention relates to a method for preparing a carbon tube by a catalytic method, which can obtain a carbon tube and ZIF-8 composite nano material in one step without adding an exogenous carbon tube. Part of the iron source forms Fe-N in the high-temperature carbonization process _x -C active sites, the other part of the iron source is agglomerated to form iron nanoparticles, and the iron nanoparticles catalyze the carbon source to grow into carbon nanotubes at high temperature. One-step method for simultaneously preparing carbon tube and catalytic active site to obtain ZIF-8-based Fe-N _x High-efficiency oxygen reduction catalyst compounded by-C and carbon tube in zinc airThe battery field has wide application prospect.

Background

Zinc-air batteries are considered to be one of the most promising energy storage and conversion devices due to their high conversion, environmental friendliness, and little emission of nitrogen oxides and sulfides. Zinc is a cheap metal resource, has abundant reserves on the earth, has the advantages of no toxicity, negative electrode potential and the like, and is always an anode widely applied to chemical power sources. The industrial production is started as early as 90 s in the 19 th century, and the anode material of the zinc-manganese battery which is still widely used globally at present is zinc. The zinc or zinc alloy is used as the anode of the fuel cell, and the cathode adopts air, so that the zinc-air cell is assembled. Zinc air cells are an energy conversion technology that is intermediate between fuel cells and conventional batteries. It has the design features of conventional cells with metallic zinc as the cathode, on the other hand, they are like fuel cells, with a porous anode structure that requires oxygen from the ambient air as a reactant. Theoretically, with oxygen in the air as the cathode, the positive electrode capacity is nearly infinite and outside the cell, the space inside the cell can be filled with more anode material. Thus, zinc-air cells are the highest specific energy among zinc-type cells, up to 1086 Wh kg-1 (including oxygen), and the cathode material is from air, with zero cost.

At present, the cathode oxygen reduction electrocatalysis of the zinc-air battery is mainly made of noble metals such as Pt and the like and alloys thereof. Although the oxygen reduction catalytic performance of the noble metal Pt catalyst is high, the noble metal Pt catalyst is expensive, scarce in resources and poor in stability, and the commercial development and application of the noble metal Pt catalyst are limited. Researches show that the functionalized carbon material can catalyze the oxygen reduction reaction, and carbon tubes and ZIF-8-based Fe-N are prepared by a catalytic method _x the-C composite material catalyst not only has high-efficiency oxygen reduction catalytic performance, but also has low raw material cost and simple and high-efficiency method. Since carbon tubes serve as supports and are very suitable for exhibiting good stability in a device such as a zinc-air battery, a carbon material catalyst doped with non-noble metal atoms is an important research direction for oxygen reduction catalysts.

Disclosure of Invention

The technical problem solved by the invention is as follows: the composite material of the carbon tube and the ZIF-8 is synthesized in one step in the carbonization process only depending on proper iron salt amount without adding an exogenous carbon tube, and simultaneously has ZIF-8-based Fe-N _x High activity of C, and stability conferred by carbon tubes. Low cost, simplicity and high efficiency. The problems of low catalytic performance, poor stability, high cost and difficulty in large-scale popularization of the zinc-air battery cathode catalyst are solved.

The invention is realized by the following modes:

step 1) dimethylimidazole, zinc nitrate hexahydrate and ferric salt are directly used for synthesizing uniformly distributed ZIF-8, and then a part of ferric salt and ZIF-8 are uniformly mixed by a freeze-drying method. Weighing a certain amount of dimethyl imidazole, uniformly stirring to disperse the dimethyl imidazole in a solvent to be named as A, weighing a certain amount of zinc nitrate hexahydrate, adding a certain amount of ferric salt, and uniformly stirring to disperse the zinc nitrate hexahydrate in the solvent to be named as B. Mixing A and B, reacting for a period of time at a certain temperature, washing with a solvent, and carrying out suction filtration to obtain a precipitate, thereby obtaining the ZIF with uniformly distributed iron, nitrogen and carbon. And then, uniformly mixing a part of iron source with ZIF-8 by a freeze-drying method to obtain ZIF-8+ Fe.

And 2) transferring the uniformly mixed ZIF-8+ Fe into a porcelain boat, putting the porcelain boat into a tubular furnace, calcining the porcelain boat in an inert atmosphere at a certain temperature for a certain time, naturally cooling the porcelain boat to room temperature, and further pickling the porcelain boat to obtain the non-noble metal electrocatalyst for the oxygen reduction reaction.

Further preferred is

The ferric salt in the step 1) can be one of ferric nitrate nonahydrate, ferric chloride hexahydrate, ammonium ferrous sulfate hexahydrate, ferrous sulfate, ferric sulfate, ferrous chloride tetrahydrate, ferrous acetate tetrahydrate, anhydrous ferrous chloride and anhydrous ferric chloride.

The molar ratio of the zinc nitrate hexahydrate to the dimethyl imidazole in the step 1) is 1 (3-8), and the preferred ratio is 1 (4-6).

The inert gas introduced into the high-temperature tube furnace in the step 2) can be argon or nitrogen, and the gas flow is 50-120ml/min.

In the step 2), the calcining process in the high-temperature tube furnace is to heat up to 150-250 ℃ at the speed of 1-10 ℃/min and preserve heat for 0.5-3.0 hours; then the temperature is raised to 800-1000 ℃ at the speed of 1-5 ℃/min, and the temperature is preserved for 0.5-3.0 hours.

THE ADVANTAGES OF THE PRESENT INVENTION

The invention utilizes the catalysis method to synthesize the carbon tube and ZIF-8 composite material for the non-noble metal electrocatalyst of the oxygen reduction reaction, the synthesis method is simple, and the prepared electrocatalyst has excellent oxygen reduction catalysis performance and good stability. Compared with the prior art, the invention has the following advantages:

1) The invention synthesizes the carbon tube by a catalytic method, and obtains the composite material of the carbon tube and ZIF-8 without adding an exogenous carbon tube. The method is simple, low in cost and easy to popularize.

2) According to the invention, proper iron salt amount is regulated and controlled twice, so that the ZIF-8-based metal-nitrogen-carbon-oxygen reduction active site with excellent performance is prepared while the carbon tube is formed through catalysis.

3) The catalyst obtained by combining the high activity of the ZIF-8 based catalyst and the high stability of the carbon tube is very suitable for being applied to components of a zinc-air battery.

Drawings

FIG. 1 is a linear scanning voltammogram of the catalyst obtained after acid washing of the carbon tube and ZIF-8 composite synthesized by the catalytic method in example 1.

FIG. 2 is a linear sweep voltammogram of the carbonless ZIF-8 based catalyst of comparative example 1.

FIG. 3 is a linear scanning voltammogram of the carbon tube and ZIF-8 composite catalyst synthesized by the catalytic method in comparative example 2.

FIG. 4 is a graph comparing the linear scanning voltammograms of the catalysts synthesized in example 1, comparative example 1, and comparative example 2.

FIG. 5 is a transmission electron microscope photograph of the catalyst obtained after acid washing the carbon tube and ZIF-8 composite synthesized by the catalytic method in example 1.

FIG. 6 shows IrO and a catalyst obtained by acid-washing a carbon tube and ZIF-8 composite synthesized by a catalytic method in example 1 ₂ And (5) a test result graph of the zinc-air battery is assembled in a mixed mode.

Detailed Description