CN113488664A

CN113488664A - Catalyst substrate material, transition metal-nitrogen co-doped pyrolytic polypyridine carbon-based electrocatalytic material, and preparation method and application thereof

Info

Publication number: CN113488664A
Application number: CN202110546191.1A
Authority: CN
Inventors: 王丹; 邓龙; 刘栋; 蒲源; 王洁欣; 陈建峰
Original assignee: Beijing University of Chemical Technology
Current assignee: Beijing University of Chemical Technology
Priority date: 2021-05-19
Filing date: 2021-05-19
Publication date: 2021-10-08
Anticipated expiration: 2041-05-19
Also published as: CN113488664B

Abstract

The invention discloses a catalyst base material, a transition metal-nitrogen co-doped pyrolysis polypyridine carbon-based electrocatalytic material and a preparation method and application thereof. The catalyst base material provided by the present invention is poly-2,6-diaminopyridine, and the poly-2,6-diaminopyridine is prepared by oxidative polymerization of cyanamide and 2,6-diaminopyridine. The transition metal-nitrogen co-doped pyrolysis polypyridine carbon-based electrocatalytic material provided by the present invention includes a catalyst base material and a transition metal doped in the catalyst base material, wherein the catalyst base material is poly-2,6 ‑Diaminopyridine. The present invention also provides the preparation method and application of the above material. In the present invention, cyanamide is used to participate in the oxidative polymerization process of 2,6-diaminopyridine, and the obtained poly-2.6-diaminopyridine is used as a catalyst base material to obtain a catalyst with high porosity and large specific surface area. quality has a significant strengthening effect.

Description

Catalyst substrate material, transition metal-nitrogen co-doped pyrolytic polypyridine carbon-based electrocatalytic material, and preparation method and application thereof

Technical Field

The present invention relates to electrocatalytic materials. More particularly, relates to a catalyst substrate material, a transition metal-nitrogen co-doped pyrolytic polypyridine carbon-based electrocatalytic material, and a preparation method and application thereof.

Background

At present, in order to achieve the goals of carbon peak reaching, carbon neutralization and the like, researchers hope to completely consume greenhouse gases directly or indirectly generated by human activities through technical and effective methods such as photovoltaic, hydrogen production, fuel cells, carbon dioxide catalytic conversion and the like. As a link for connection between cycles, energy conversion and energy storage devices such as Proton Exchange Membrane Fuel Cells (PEMFCs), Metal-Air (Metal-Air) cells and the like can convert part of chemical energy in the cathode material into electric energy without Carnot cycle, thereby reducing unnecessary power consumption in the process and achieving higher conversion efficiency. Among these, the Oxygen Reduction Reaction (ORR) occurring at the cathode is critical to improving the efficiency of the overall electrochemical process.

The ORR reaction mainly relies on a platinum-based catalyst (Pt/C) to reduce the half-reaction activation energy barrier, but the catalyst of the type is limited by the problems of low reserves of noble metals, high price, easy poisoning and inactivation and the like, and cannot be widely produced and applied. The non-noble metal catalyst (NPMC) aims at overcoming the defects of the platinum-based catalyst by the characteristics of low price, high efficiency and easy popularization.

Among non-noble metal catalysts, the M (transition metal) -N-C catalyst taking polymer derived carbon as a substrate is distinguished by excellent catalytic activity and a convenient preparation method, and can be a reliable substitute of a Pt/C catalyst. However, the main difficulties of industrial production and commercial use are: 1) the polymerization mechanism in the substrate production process is complex, and the dynamics, mass transfer and heat transfer processes in a homogeneous/heterogeneous system are difficult to judge; 2) the distribution of metal active centers is not uniform, and the catalytic activity is difficult to completely express; 3) the catalyst has low batch yield, high price and difficult popularization. Therefore, it is desirable to provide an efficient and simple method for preparing a catalyst, which should have high activity and stability in an electrolyte.

Therefore, the invention provides a catalyst substrate material, a transition metal-nitrogen co-doped pyrolytic polypyridine carbon-based electrocatalytic material, and a preparation method and application thereof, so as to solve at least one of the problems.

Disclosure of Invention

A first object of the present invention is to provide a catalyst base material.

A second object of the present invention is to provide a method for preparing a catalyst base material.

The third purpose of the invention is to provide a transition metal-nitrogen co-doped pyrolytic polypyridine-based electrocatalytic material.

The fourth purpose of the invention is to provide a preparation method of the transition metal-nitrogen co-doped pyrolytic polypyridine carbon-based electrocatalytic material.

The fifth purpose of the invention is to provide application of the transition metal-nitrogen co-doped pyrolytic polypyridine carbon-based electrocatalytic material.

In order to achieve the purpose, the invention adopts the following technical scheme:

in a first aspect, the present invention provides a catalyst base material, which is poly-2, 6-diaminopyridine, wherein the poly-2, 6-diaminopyridine is prepared by oxidative polymerization of cyanamide and 2, 6-diaminopyridine. The method provided by the invention uses cyanamide to participate in the oxidative polymerization process of 2, 6-diaminopyridine, and adjusts the bonding mode of the 2, 6-diaminopyridine and other molecules in the polymerization process, so that the specific surface area and the porosity of the catalyst prepared by pyrolysis of poly-2, 6-diaminopyridine are greatly improved, and the method has an obvious reinforcing effect on the mass transfer of the catalyst and electrolyte in a medium.

Preferably, the molar ratio of the cyanamide to the 2, 6-diaminopyridine is 1:2 to 12, more preferably 1:3 to 8, and still more preferably 1: 8.

Preferably, the preparation of the poly-2, 6-diaminopyridine is carried out in a rotating packed bed reactor. The invention preferably selects the rotary packed bed reactor to strengthen the oxidation polymerization process of the 2, 6-diaminopyridine, and compared with the method without adopting the rotary packed bed, the conversion rate of the 2, 6-diaminopyridine in the polymerization reaction is improved by about 10 percent, the polymerization time is shortened, and the preparation efficiency of the polymer is greatly improved. The polymerization engineering is different from the traditional micromolecule chemical engineering, and has the characteristics of complex mechanism, difficult judgment of dynamic process, various mass and heat transfer processes of homogeneous and heterogeneous systems and the like. Therefore, the strengthening of polymerization engineering often requires specific analysis of specific target products, and the performance of the products is improved by applying appropriate measures and equipment to controllably prepare the related products. The rotary packed bed reactor can generate a supergravity field to push reaction materials entering a system (gas-liquid, liquid-liquid and liquid-solid) into a filler with a complex pore channel structure, and tear liquid to a liquid film, liquid drops and liquid threads from micron to nanometer by utilizing shearing force provided by far supernormal stirring, so that a phase interface is quickly updated, and interphase mass transfer is greatly improved, thereby achieving the purpose of strengthening the chemical process. Therefore, the uniqueness of the method is applied to solve the defects of low conversion rate, long reaction time and the like of the 2, 6-diaminopyridine in the polymerization reaction.

In a second aspect, the present invention provides a method for preparing a catalyst base material, comprising the steps of:

the catalyst base material is prepared by oxidizing and polymerizing cyanamide and 2, 6-diaminopyridine.

Preferably, the preparation of the catalyst base material is carried out in a rotating packed bed reactor.

Preferably, the preparation method of the catalyst base material specifically comprises the following steps:

1) dissolving 2, 6-diaminopyridine and cyanamide in an alkaline solution to obtain a feed liquid A; dissolving an oxidant in water to obtain a feed liquid B;

2) adding the feed liquid A and the feed liquid B into a rotary packed bed reactor, and reacting to obtain a product A;

3) taking out the product A, and stirring at a constant speed to react to obtain a product B;

4) and separating, washing and drying the product B to obtain the catalyst substrate material.

Preferably, the alkaline solution in the step 1) is an aqueous solution of sodium hydroxide, potassium hydroxide or calcium hydroxide with the concentration of 7.57-15.15 mg/L.

Preferably, the oxidant in step 1) is ammonium persulfate, potassium persulfate or sodium persulfate.

Preferably, the volume ratio of the feed liquid A to the feed liquid B in the step 1) is 5-1: 1, and more preferably 1: 1.

Preferably, the volumes of the feed liquid A and the feed liquid B in the step 1) are 240 mL.

Preferably, the molar ratio of the oxidizing agent to 2, 6-diaminopyridine in step 1) is greater than or equal to 1: 1.

Preferably, the hypergravity horizontal value of the rotating packed bed reactor in the step 2) is 50-250, and more preferably 250.

Preferably, the temperature of the reaction in step 2) is less than or equal to 20 ℃.

Preferably, the reaction time in the step 2) is 40-50 s. The invention utilizes the rotary packed bed reactor to shorten the polymerization time from the original 660-720 min to 150-180 min, thereby greatly improving the preparation efficiency of the polymer

Preferably, the feed liquid A and the feed liquid B in the step 2) are pumped into the rotating packed bed reactor by a peristaltic pump.

Preferably, the feeding speed of the peristaltic pump is 240-480 mL/min, and more preferably 320 mL/min.

Preferably, the stirring speed in the step 3) is 300-500 rpm. In the invention, only the synthesis of oligomers such as dimer, trimer and the like of 2, 6-diaminopyridine is carried out in a rotating packed bed reactor, and the subsequent polymerization reaction is completed in a stirring system with the rotating speed of 300-500 rpm.

Preferably, the temperature of the stirring reaction in step 3) is less than or equal to 20 ℃.

Preferably, the stirring reaction time in the step 3) is 150-720 min.

Preferably, the drying in the step 4) is vacuum drying, the drying temperature is preferably 20-80 ℃, and the drying time is preferably 3-6 h.

In a third aspect, the invention provides a transition metal-nitrogen co-doped pyrolytic polypyridine carbon-based electrocatalytic material, which comprises a catalyst substrate material and a transition metal doped in the catalyst substrate material; wherein the catalyst substrate material is poly 2, 6-diaminopyridine. The transition metal-nitrogen co-doped pyrolytic polypyridine carbon-based electrocatalytic material provided by the invention adopts poly 2, 6-diaminopyridine as a catalyst substrate material, and the specific surface area of the prepared catalyst reaches 640-720 m²The pore volume reaches 0.10-0.34 cm³Between the volume ratio of the pores with the pore diameter of more than 0.5nm and less than 1nm is greatly improved, which is beneficial to improving the mass transfer effect of the catalyst and the hydrated ions in the electrolyte; the mesoporous proportion of the pore diameter larger than 2nm and smaller than 5nm is also obviously improved. Helps expose active sites of the catalyst in the electrolyte; has obvious strengthening effect on the mass transfer with the electrolyte in the medium.

Preferably, the specific surface area of the transition metal-nitrogen co-doped pyrolytic polypyridine carbon-based electrocatalytic material is 640-720 m²(iv)/g, more preferably 645.4226m²/g。

Preferably, the transition metal is transition metal iron and/or transition metal manganese.

Preferably, the transition metal-nitrogen co-doped pyrolytic polypyridine carbon-based electrocatalytic material is prepared by carrying a transition metal precursor on poly (2, 6-diaminopyridine) through pyrolysis.

Preferably, the transition metal precursor is a transition metal iron precursor and/or a transition metal manganese precursor.

Preferably, the transition metal iron precursor is one or more of ferric nitrate, ferric chloride and ferric acetate, and more preferably ferric nitrate.

Preferably, the transition metal manganese precursor is one or more of manganese nitrate, manganese acetate and manganese chloride, and more preferably is manganese acetate.

Preferably, the molar ratio of the transition metal iron precursor to the transition metal manganese precursor is 1: 0.025-2, more preferably 1: 0.05-0.5, and still more preferably 1: 0.05.

Preferably, the preparation process of the transition metal-nitrogen co-doped pyrolytic polypyridine carbon-based electrocatalytic material is carried out in a rotating packed bed reactor. Because how the active center of the catalyst is synthesized and evenly anchored on the polymer derived carbon determines whether the catalyst can show enough activity, which is a control problem of heterogeneous reaction, and the rotating packed bed has obvious strengthening effect on mass transfer between solid and liquid phases and is beneficial to solving the problems, the invention uses the loading process of the transition metal precursor of the rotating packed bed reactor for strengthening, and uses a triple reaction system to load the transition metal precursor in the rotating packed bed reactor as the catalyst substrate material to prepare the catalyst with the performance equivalent to that of the catalyst in a beaker experiment reaction system, thereby preliminarily solving the amplification effect of catalyst preparation.

In a fourth aspect, the invention provides a preparation method of a transition metal-nitrogen co-doped pyrolytic polypyridine-carbon-based electrocatalytic material, which comprises the following steps:

the transition metal-nitrogen co-doped pyrolytic polypyridine carbon-based electrocatalytic material is prepared by loading a transition metal precursor on a catalyst substrate material and carrying out pyrolysis; wherein the catalyst substrate material is poly 2, 6-diaminopyridine.

Preferably, the pyrolysis process is to heat the mixture to 800-1200 ℃ at a heating rate of 4-6 ℃/min, keep the temperature for 2-4 h, and then naturally cool the mixture.

Preferably, the preparation method of the transition metal-nitrogen co-doped pyrolytic polypyridine carbon-based electrocatalytic material specifically comprises the following steps:

s1, ultrasonically dispersing poly-2, 6-diaminopyridine in water to obtain feed liquid C; dissolving a transition metal precursor in water to obtain a feed liquid D;

s2, adding the material taking liquid D and the material liquid C into a rotary packed bed reactor to react to obtain a product C, and separating, washing and drying the product C to obtain a product D;

s3, pyrolyzing the product D to obtain a product E;

and S4, carrying out acid washing and separation on the product E, and then carrying out secondary pyrolysis to obtain the transition metal-nitrogen co-doped pyrolytic polypyridine carbon-based electrocatalytic material.

Preferably, the concentration of the feed liquid C in the step S1 is 0.5-20 mg/mL.

Preferably, the concentration of the feed liquid D in the step S1 is 1-3 mg/mL.

Preferably, the amount of the poly-2, 6-diaminopyridine used in step S1 is 200 to 1000mg, and more preferably 600 mg.

Preferably, the volume of the feed liquid C in the step S1 is 60-300 mL, and more preferably 180 mL.

Preferably, the transition metal precursor in step S1 is a transition metal iron precursor and/or a transition metal manganese precursor.

Preferably, the transition metal iron precursor in step S1 is one or more of ferric nitrate, ferric chloride and ferric acetate, and more preferably ferric nitrate.

Preferably, the transition metal manganese precursor in step S1 is one or more of manganese nitrate, manganese acetate and manganese chloride, and more preferably manganese acetate.

Preferably, the molar ratio of the transition metal iron precursor to the transition metal manganese precursor in step S1 is 1: 0.025-2, more preferably 1: 0.05-0.5, and still more preferably 1: 0.05.

Preferably, the volume ratio of the feed liquid D to the feed liquid C in the step S2 is 1-3: 12, and more preferably 1: 6.

Preferably, the temperature of the reaction in step S2 is 60-80 ℃.

Preferably, the reaction time in the step S2 is 5-7 h, and more preferably 6 h.

Preferably, the hypergravity horizontal value of the rotating packed bed reactor in the step S2 is 100-200, and more preferably 150.

Preferably, the drying in step S2 is vacuum drying; the drying temperature is preferably 60-80 ℃, and more preferably 70 ℃; the drying time is preferably 3-6 h.

Preferably, in the step S3, the pyrolysis process is performed by heating to 800-1200 ℃ at a heating rate of 4-6 ℃/min in a nitrogen atmosphere, maintaining for 2-4 h, and then naturally cooling.

Preferably, the pyrolysis in step S3 is performed in a tube furnace.

Preferably, the acid washing in the step S4 is washing in sulfuric acid for 8-9 h.

Preferably, the concentration of the sulfuric acid is 0.4-0.6 mol/L, and more preferably 0.5 mol/L.

Preferably, the acid washing in the step S4 is performed at a temperature of 80-95 ℃.

Preferably, the secondary pyrolysis conditions in step S4 are the same as the pyrolysis conditions in step S3.

In the process of applying the rotary packed bed reactor to the hydrothermal adsorption of the transition metal precursor of the poly-2, 6-diaminopyridine, the preparation of the catalyst precursor can be completed in a larger reaction system compared with the traditional stirring, and after the proportion of each element in the catalyst obtained after pyrolysis is roughly analyzed by an X-ray electron diffraction spectrogram, the proportion of the iron element and/or the manganese element serving as an active center is obviously increased, which shows that the reactor has a reinforcing effect on the strategy of preparing the catalyst by loading the transition metal on a substrate in situ by methods such as impregnation and the like, and can efficiently complete the uniform distribution of the active center.

In a fifth aspect, the invention provides an application of a transition metal-nitrogen co-doped pyrolytic polypyridine carbon-based electrocatalytic material as a negative oxygen reduction reaction catalyst in a zinc-air battery.

The invention has the following beneficial effects:

(1) the catalyst prepared by adopting the dicyandiamide to participate in the oxidative polymerization process of the 2, 6-diaminopyridine and taking the obtained poly-2, 6-diaminopyridine as a catalyst substrate material has high porosity and large specific surface area, and has obvious strengthening effect on mass transfer with electrolyte in a medium;

(2) according to the invention, the enhancement effect of the rotary packed bed on the micromixing of a reaction system and the solid-liquid interphase mass transfer process is utilized, so that the oxidation polymerization process of the 2, 6-diaminopyridine is enhanced, the conversion rate of raw materials is improved by about 10%, the reaction time is shortened, the preparation efficiency of a polymer is greatly improved, and the economical efficiency of a chemical reaction is greatly improved; the main preparation process of the transition metal-nitrogen co-doped pyrolytic polypyridine carbon-based electrocatalytic material is strengthened, and the uniform distribution of active centers is efficiently completed;

(3) according to the invention, the preparation cost of the transition metal-nitrogen co-doped pyrolytic polypyridine carbon-based electrocatalytic material can be remarkably saved by applying the graphitization process of the transition metal manganese precursor under the condition of not changing the pyrolysis temperature; meanwhile, the current density of the transition metal-nitrogen co-doped pyrolytic polypyridine carbon-based electrocatalytic material in a medium test can be obviously improved by improving the graphitization degree of the material.

Drawings

In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings needed to be used in the description of the embodiments will be briefly introduced below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is obvious for those skilled in the art to obtain other drawings based on these drawings without creative efforts.

FIG. 1 shows the conversion of 2, 6-diaminopyridine as a function of time for oxidative polymerization in example 1 according to the invention and in comparative example 1.

FIG. 2 shows an enlarged graph of the reaction time of 120-720 min in FIG. 1.

FIG. 3 shows a comparison of the infrared spectra of poly-2, 6-diaminopyridine obtained in inventive example 1 and comparative example 2.

Fig. 4 shows a comparison graph of linear voltammetry scan test curves of transition metal-nitrogen co-doped pyrolytic polypyridine carbon-based electrocatalytic materials prepared under different molar ratios of the dicyandiamide and the 2, 6-diaminopyridine in examples 7 to 12 of the present invention.

Fig. 5 shows a Scanning Electron Microscope (SEM) image of the transition metal-nitrogen co-doped pyrolytic polypyridine carbon-based electrocatalytic material prepared in example 13 of the present invention.

Fig. 6 shows a Transmission Electron Microscope (TEM) image of the transition metal-nitrogen co-doped pyrolytic polypyridine carbon-based electrocatalytic material prepared in example 13 of the present invention.

Fig. 7 shows a nitrogen isothermal adsorption and desorption graph of transition metal-nitrogen co-doped pyrolytic polypyridine carbon-based electrocatalytic materials prepared in example 13 of the present invention and comparative example 3.

Fig. 8 is a graph showing a comparison of pore size distributions of transition metal-nitrogen co-doped pyrolytic polypyridine carbon-based electrocatalytic materials prepared in example 13 of the present invention and comparative example 3.

FIG. 9 is a graph showing a comparison of linear voltammetry sweep test curves of the transition metal-nitrogen co-doped pyrolyzed polypyridine carbon-based electrocatalytic material prepared in example 13 of the present invention and comparative example 4 and a commercial Pt/C catalyst.

Fig. 10 shows comparison graphs of linear voltammetry scan test curves of transition metal-nitrogen co-doped pyrolytic polypyridine carbon-based electrocatalytic materials prepared under different molar ratios of a transition metal Mn precursor and a Fe precursor in examples 13 to 18 and comparative example 5 of the present invention.

FIG. 11 is a graph showing the comparison of the results of potentiostatic time measurement current (I-T stability) of the transition metal-nitrogen co-doped type pyrolyzed polypyridine carbon-based electrocatalytic material prepared in example 13 of the present invention and a commercial Pt/C catalyst.

Fig. 12 is a graph comparing the results of the methanol stability test of the transition metal-nitrogen co-doped pyrolytic polypyridine carbon-based electrocatalytic material prepared in example 13 of the present invention and a commercial Pt/C catalyst.

Fig. 13 is a graph showing a comparison of the results of power density tests in which the transition metal-nitrogen co-doped pyrolytic polypyridine carbon-based electrocatalytic material prepared in example 13 of the present invention and comparative example 4 and a commercial Pt/C catalyst were used in a zinc-air battery, respectively.

Detailed Description

In order to make the technical solutions and advantages of the present invention more apparent, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

It should be noted that, the execution order of the steps is not limited in the embodiment of the present invention; all numerical designations of the invention (e.g., temperature, time, concentration, weight, and the like, including ranges for each) may generally be approximations that vary (+) or (-) in increments of 0.1 or 1.0 as appropriate. All numerical designations should be understood as preceded by the term "about".

All electrochemical tests in the invention were carried out in oxygen-saturated 0.1M KOH electrolyte, and a three-electrode system consisted of a glassy carbon electrode (rotating disk electrode) coated with catalyst, a platinum wire electrode, and an Ag/Agcl electrode. In the medium, the rotation speed of RDE is 1600rpm, and a linear volt-ampere scanning test (LSV), a constant potential timing current stability test and an anti-methanol stability test are completed within a voltage range of 1.1-0V (vs. RHE) at a scanning speed of 5 mV/s. The zinc-air battery tests all adopt a molybdenum net as an air transmission layer, and the electrolyte is 6mol/L KOH.

Example 1

This example provides a method for preparing poly-2, 6-diaminopyridine as a catalyst substrate material, comprising the following steps:

1) weighing 3.06g of NaOH to dissolve in 240mL of deionized water to obtain NaOH aqueous solution, then weighing 5.57g of 2, 6-diaminopyridine to add into the NaOH aqueous solution, and after completely dissolving, adding cyanamide to mix and dissolve to obtain feed liquid A, wherein the molar ratio of the cyanamide to the 2, 6-diaminopyridine is 1: 8;

preparation of 240mL of a solution having 17.4g (NH) dissolved therein₄)₂S₂O₈The deionized water solution is feed liquid B;

2) pumping the material liquid A and the material liquid B into a rotary packed bed reactor (external circulation) by a peristaltic pump at a flow rate of 480mL/min, and reacting for 48s under the conditions of room temperature and a supergravity level of 250 to synthesize an oligomer solid-liquid dispersion phase, namely a product A;

3) then transferring the product A into a beaker, stirring at the room temperature at the speed of 400rpm, and polymerizing the product A for 12 hours along with slight heat release and ammonia generation to obtain a product B;

4) after the reaction is finished, filtering and separating the solid, and drying the solid in a vacuum oven with the preset temperature of 70 ℃ for 24 hours to obtain poly (2.6-Diaminopyridine) (DAP) solid, namely the catalyst substrate material.

FIGS. 1 and 2 show the conversion of 2, 6-diaminopyridine as a function of time for oxidative polymerization in example 1 according to the invention and in comparative example 1. In example 1, a rotating packed bed reactor was used, and in comparative example 1, a rotating packed bed reactor was not used. The time for mixing the 2, 6-diaminopyridine with the oxidant in example 1 was about 48s, and the time required for the process in the experiment of comparative example 1 was about 40 min; the pyridine conversion in example 1 was about 20% higher than that in comparative example 1 at the instant the oxidant addition was completed. After 180min of rapid polymerization, the molecular conversion ratio of 2, 6-diaminopyridine in example 1 is not changed any more and is stabilized at 91.61% (about 9% higher than that in comparative example 1), and 4.78% of pyridine in comparative example 1 is still reacted continuously, which proves that the reaction can reach the end point rapidly after the process is strengthened by the rotating packed bed, and the reaction time is greatly reduced.

FIG. 3 shows a comparison of the infrared spectra of poly-2, 6-diaminopyridine obtained in inventive example 1 and comparative example 2. Example 1 after the addition of the cyanamide, the infrared spectrum of the product is 2200cm^-1The stretching vibration peak attributed to-CN completely disappears, and the infrared spectrum peak pattern is similar to that of poly 2, 6-diaminopyridine prepared by comparative example 2 without adding cyanamide, thus proving that the cyanamide reaction is complete under the proportion; remained at 1450cm^-1And 1590cm^-1At the wavelength, the stretching vibration peak of the C-H bond on the six-membered ring containing pyridine nitrogen is located at 3300-^-1Between are-NH₂Bimodal (amino) proved to be the main component participating in the polymer, 2, 6-diaminopyridine.

Comparative example 1

The comparative example provides a method for preparing a catalyst substrate material poly 2, 6-diaminopyridine, comprising the steps of:

2) slowly dropwise adding 80mL of feed liquid B into the feed liquid A prepared in the step 1), stirring at the speed of 400rpm, and polymerizing for 12h with slight heat release and ammonia generation; after the reaction is finished, filtering and separating the solid, and drying the solid in a vacuum oven with the preset temperature of 70 ℃ for 24 hours to obtain poly (2.6-Diaminopyridine) (DAP) solid, namely the catalyst substrate material.

Comparative example 2

1) weighing 3.06g of NaOH to dissolve in 240mL of deionized water to obtain NaOH aqueous solution, then weighing 5.57g of 2, 6-diaminopyridine to add into the NaOH aqueous solution, and obtaining feed liquid A after complete dissolution;

Example 2

1) weighing 3.06g of NaOH to dissolve in 240mL of deionized water to obtain NaOH aqueous solution, then weighing 5.57g of 2, 6-diaminopyridine to add into the NaOH aqueous solution, and after completely dissolving, adding cyanamide to mix and dissolve to obtain feed liquid A, wherein the molar ratio of the cyanamide to the 2, 6-diaminopyridine is 1: 2;

Example 3

1) weighing 3.06g of NaOH to dissolve in 240mL of deionized water to obtain NaOH aqueous solution, then weighing 5.57g of 2, 6-diaminopyridine to add into the NaOH aqueous solution, and after completely dissolving, adding cyanamide to mix and dissolve to obtain feed liquid A, wherein the molar ratio of the cyanamide to the 2, 6-diaminopyridine is 1: 3;

Example 4

1) weighing 3.06g of NaOH to dissolve in 240mL of deionized water to obtain NaOH aqueous solution, then weighing 5.57g of 2, 6-diaminopyridine to add into the NaOH aqueous solution, and after completely dissolving, adding cyanamide to mix and dissolve to obtain feed liquid A, wherein the molar ratio of the cyanamide to the 2, 6-diaminopyridine is 1: 4;

Example 5

1) weighing 3.06g of NaOH to dissolve in 240mL of deionized water to obtain NaOH aqueous solution, then weighing 5.57g of 2, 6-diaminopyridine to add into the NaOH aqueous solution, and after completely dissolving, adding cyanamide to mix and dissolve to obtain feed liquid A, wherein the molar ratio of the cyanamide to the 2, 6-diaminopyridine is 1: 5;

Example 6

1) weighing 3.06g of NaOH to dissolve in 240mL of deionized water to obtain NaOH aqueous solution, then weighing 5.57g of 2, 6-diaminopyridine to add into the NaOH aqueous solution, and after completely dissolving, adding cyanamide to mix and dissolve to obtain feed liquid A, wherein the molar ratio of the cyanamide to the 2, 6-diaminopyridine is 1: 12;

Example 7

The comparative example provides a preparation method of a transition metal-nitrogen co-doped pyrolytic polypyridine carbon-based electrocatalytic material, which comprises the following steps:

s1, measuring 180ml of deionized water, dispersing 200mg of the catalyst substrate material prepared in the embodiment 1 in a beaker, and obtaining feed liquid C;

preparation of 60ml transition Metal nitrate (weighing and dissolving 33.44mg Fe (NO)₃)₃·9H₂O) in another beaker to obtain a feed liquid D;

s2, mixing the feed liquid C obtained in the step S1 with 10ml of feed liquid D, stirring and reacting for 6 hours in a water bath at 70 ℃ to obtain a product C, carrying out suction filtration on the product C to separate a solid, washing, and drying for 2-4 hours in a vacuum oven at 70 ℃ to obtain a transition metal loaded carbon-based catalytic material precursor, namely the product D;

s3, placing the product D in a tube furnace, and heating from room temperature to 1000 ℃ at a heating rate of 5 ℃/min under the blowing of nitrogen atmosphere, and carrying out constant-temperature pyrolysis for 3h to obtain a black and fine product E;

s4, post-processing the product E: a flask was taken and the product E obtained was dispersed in 100ml of 0.5mol/L H₂SO₄In 8And (4) pickling for 8h in water bath at 0 ℃, performing suction filtration to separate solid particles, drying for 0.5h in a vacuum oven at the preset temperature of 70 ℃, and performing secondary pyrolysis under the same condition as the step S3 to obtain the transition metal-nitrogen co-doped pyrolytic polypyridine carbon-based electrocatalytic material.

Example 8

s1, measuring 180ml of deionized water, dispersing 200mg of the catalyst substrate material prepared in the embodiment 2 in a beaker, and obtaining feed liquid C;

s4, post-processing the product E: a flask was taken and the product E obtained was dispersed in 100ml of 0.5mol/L H₂SO₄And (3) carrying out acid washing for 8h in a water bath at the temperature of 80 ℃, carrying out suction filtration to separate solid particles, drying for 0.5h in a vacuum oven at the preset temperature of 70 ℃, and carrying out secondary pyrolysis under the same condition as that in the step S3 to obtain the transition metal-nitrogen co-doped pyrolytic polypyridine carbon-based electrocatalytic material.

Example 9

s1, measuring 180ml of deionized water, dispersing 200mg of the catalyst substrate material prepared in the embodiment 3 in a beaker, and obtaining feed liquid C;

Example 10

s1, measuring 180ml of deionized water, dispersing 200mg of the catalyst substrate material prepared in the embodiment 4 in a beaker, and obtaining feed liquid C;

Example 11

s1, measuring 180ml of deionized water, dispersing 200mg of the catalyst substrate material prepared in the embodiment 5 in a beaker, and obtaining feed liquid C;

Example 12

s1, measuring 180ml of deionized water, dispersing 200mg of the catalyst substrate material prepared in the embodiment 6 in a beaker, and obtaining feed liquid C;

Fig. 4 shows a comparison graph of linear voltammetry scan test curves of transition metal-nitrogen co-doped pyrolytic polypyridine carbon-based electrocatalytic materials prepared in examples 7 to 12 of the present invention under conditions of molar ratios of 1:8, 1:2, 1:3, 1:4, 1:5, and 1:12, respectively. The result of the half-wave potential change is obtained from the test data, and the ratio of the addition amount of the cyanamide to the 2, 6-diaminopyridine is preferably 1:3 to 8, most preferably 8:1

Example 13

The embodiment provides a preparation method of a transition metal-nitrogen co-doped pyrolytic polypyridine carbon-based electrocatalytic material, which comprises the following steps:

preparation of 60ml transition Metal nitrate (i.e., weighing and dissolving 33.44mg Fe (NO)₃)₃·9H₂O, and Mn (AC)₂·4H₂O miscible in which Mn (AC)₂·4H₂O and Fe (NO)₃)₃·9H₂The molar ratio of O is 1:0.05) in another beaker to obtain feed liquid D;

s2, mixing the feed liquid C obtained in the step S1 with 10ml of feed liquid D, reacting for 6 hours at room temperature in a rotary packed bed reactor (internal circulation) with the supergravity level of 150 to obtain a product C, carrying out suction filtration on the product C to separate solid, washing, and drying for 2-4 hours in a vacuum oven with the preset temperature of 70 ℃ to obtain a transition metal loaded carbon-based catalytic material precursor, namely the product D;

Fig. 5 and 6 respectively show a Scanning Electron Microscope (SEM) image and a Transmission Electron Microscope (TEM) image of the transition metal-nitrogen co-doped pyrolytic polypyridine carbon-based electrocatalytic material prepared in example 13 of the present invention, and it can be seen that the overall morphology is uniformly spherical and has relatively obvious pores.

FIG. 7 shows the nitrogen isothermal adsorption and desorption curves of the transition metal-nitrogen co-doped pyrolytic polypyridine carbon-based electrocatalytic material prepared in example 13 of the invention and unmodified pyrolytic poly-2, 6-diaminopyridine prepared in comparative example 3. After the catalyst is prepared by the method shown in the embodiment 13, the specific surface area of the catalyst is obviously improved compared with that of pyrolyzed unmodified poly-2, 6-diaminopyridine, and the specific surface area can reach 640-720 m²/g。

FIG. 8 is a graph showing the comparison of pore size distribution of unmodified thermal depolymerization 2, 6-diaminopyridine in the transition metal-nitrogen co-doped thermal depolymerization pyridine-based electrocatalytic material prepared in example 13 of the present invention and comparative example 3. As can be seen from fig. 8, the transition metal-nitrogen co-doped pyrolytic polypyridine carbon-based electrocatalytic material prepared in example 13 has micropores with a pore diameter smaller than 1nm, mesopores with a pore diameter of 1-2 nm, and a mesopore ratio of 2-5nm, which are all significantly improved. According to literature reports, micropores with the pore diameter larger than 0.5nm are beneficial to mass transfer of hydrated ions in electrolyte, and mesopores with the pore diameter of 2-5nm can expose more active sites and enhance mass transfer of a catalyst in the electrolyte, so that the transition metal-nitrogen co-doped pyrolytic polypyridine carbon-based electrocatalytic material prepared in the embodiment 3 has better performance compared with the transition metal-nitrogen co-doped pyrolytic polypyridine carbon-based electrocatalytic material prepared by using a catalyst substrate material prepared without adding cyanamide in the comparative example 3.

FIG. 9 is a graph showing a comparison of linear voltammetry sweep test curves of the transition metal-nitrogen co-doped pyrolyzed polypyridine carbon-based electrocatalytic material prepared in example 13 of the present invention and comparative example 4 and a commercial Pt/C catalyst. The half-wave potential of the transition metal-nitrogen co-doped pyrolytic polypyridine carbon-based electrocatalytic material prepared in example 13 in 0.1M KOH electrolyte reaches 0.891V, is 57mV higher than that of commercial Pt/C (0.834V), and shows nearly 1mA/cm higher current density in the test compared with that of the catalyst prepared in comparative example 4²The half-wave potential is higher than about 8 mV. Has the advantages of high catalytic activity,

fig. 10 shows comparison graphs of linear voltammetry scan test curves of transition metal-nitrogen co-doped pyrolytic polypyridine-based electrocatalytic materials prepared in the following manner that the molar ratios of a transition metal Fe precursor to a Mn precursor in examples 13 to 18 and comparative example 5 are 1:0.05, 1:0.025, 1:0.25, 1:0.5, 1:1, 1:2, and 1:0. The comparison of the addition amounts of the transition metals Mn and Fe is preferably 0.05 to 0.5:1, most preferably 0.05:1, as a result of the half-wave potential change obtained from the test data. In comparative example 5, no transition metal Mn was added, and the catalyst had a lower degree of graphitization, so that its current density was lower than that of example 13.

FIG. 11 is a graph showing the comparison of the results of potentiostatic time measurement current (I-T stability) of the transition metal-nitrogen co-doped type pyrolyzed polypyridine carbon-based electrocatalytic material prepared in example 13 of the present invention and a commercial Pt/C catalyst. Fig. 11 shows that the current of the transition metal-nitrogen co-doped pyrolytic polypyridine carbon-based electrocatalytic material prepared in example 13 of the present invention still maintains 86% of the initial current after a test of 25000s, while the current of the commercial Pt/C decreases to 65% of the initial current, which proves that the transition metal-nitrogen co-doped pyrolytic polypyridine carbon-based electrocatalytic material prepared in example 13 of the present invention has excellent stability.

Fig. 12 is a graph comparing the results of the methanol stability test of the transition metal-nitrogen co-doped pyrolytic polypyridine carbon-based electrocatalytic material prepared in example 13 of the present invention and a commercial Pt/C catalyst. The principle of the test is the same as that of a constant potential timing current test, 5mL of methanol is added into 100mL of electrolyte at 250s, the current shown by the transition metal-nitrogen co-doped pyrolytic polypyridine carbon-based electrocatalytic material prepared in example 13 rapidly recovers to be normal after fluctuation, and commercial Pt/C is rapidly inactivated, so that the transition metal-nitrogen co-doped pyrolytic polypyridine carbon-based electrocatalytic material prepared in example 13 is proved to have excellent methanol resistance stability.

Fig. 13 is a graph showing a comparison of the results of power density tests in which the transition metal-nitrogen co-doped pyrolytic polypyridine carbon-based electrocatalytic material prepared in example 13 of the present invention and comparative example 4 and a commercial Pt/C catalyst were used in a zinc-air battery, respectively. The transition metal-nitrogen co-doped pyrolytic polypyridine carbon-based electrocatalytic material prepared in example 13 shows 178.18mW/cm in a zinc-air battery²Power density of 141.12mW/cm in a zinc-air cell, relative to the catalyst prepared in comparative example 4 without a rotating packed bed reactor²The power density is improved by about 30mW/cm²(ii) a 130-135 mW/cm compared with the common performance of commercial Pt/C²The power density is obviously improved, and the result shows that the transition metal-nitrogen co-doped pyrolytic polypyridine carbon-based electrocatalytic material prepared by adopting the rotary packed bed reactor has better performance.

Comparative example 3

s1, measuring 180ml of deionized water, dispersing 200mg of the catalyst substrate material prepared in the comparative example 2 in a beaker, and obtaining feed liquid C;

Comparative example 4

Example 14

preparation of 60ml transition Metal nitrate (i.e., weighing and dissolving 33.44mg Fe (NO)₃)₃·9H₂O, and Mn (AC)₂·4H₂O miscible in which Mn (AC)₂·4H₂O and Fe (NO)₃)₃·9H₂The molar ratio of O is 1:0.025) in another beaker to obtain feed liquid D;

s4, post-processing the product E: and (3) taking a flask, dispersing the obtained product E in 100ml of 0.5mol/L H2SO4, carrying out acid washing for 8H in a water bath at 80 ℃, carrying out suction filtration to separate solid particles, drying for 0.5H in a vacuum oven at 70 ℃, and carrying out secondary pyrolysis under the same condition as that in the step S3 to obtain the transition metal-nitrogen co-doped pyrolytic polypyridine carbon-based electrocatalytic material.

Example 15

preparation of 60ml transition Metal nitrate (i.e., weighing and dissolving 33.44mg Fe (NO)₃)₃·9H₂O, and Mn (AC)₂·4H₂O miscible in which Mn (AC)₂·4H₂O and Fe (NO)₃)₃·9H₂Putting a deionized water solution with the molar ratio of O being 1:0.25 into another beaker to obtain a feed liquid D;

Example 16

preparation of 60ml transition Metal nitrate (i.e., weighing and dissolving 33.44mg Fe (NO)₃)₃·9H₂O, and Mn (AC)₂·4H₂O miscible in which Mn (AC)₂·4H₂O and Fe (NO)₃)₃·9H₂The molar ratio of O is 1:0.5) in another beaker to obtain feed liquid D;

Example 17

preparation of 60ml transition Metal nitrate (i.e., weighing and dissolving 33.44mg Fe (NO)₃)₃·9H₂O, and Mn (AC)₂·4H₂O miscible in which Mn (AC)₂·4H₂O and Fe (NO)₃)₃·9H₂Putting the deionized water solution with the molar ratio of O being 1:1) into another beaker to obtain feed liquid D;

Example 18

preparation of 60ml transition Metal nitrate (33.44 mg Fe (NO3) 3.9H weighed out and dissolved)₂O, and Mn (AC)₂·4H₂O miscible in which Mn (AC)₂·4H₂O and Fe (NO)₃)₃·9H₂Deionized water solution with the molar ratio of O being 1:2) is put into another beaker to obtain feed liquid D;

Comparative example 5

preparation of 60ml transition Metal nitrate (i.e., weighing and dissolving 33.44mg Fe (NO)₃)₃·9H₂O) in another beaker to obtain a feed liquid D;

It should be understood that the above-mentioned embodiments of the present invention are only examples for clearly illustrating the present invention, and are not intended to limit the embodiments of the present invention, and it will be obvious to those skilled in the art that other variations or modifications may be made on the basis of the above description, and all embodiments may not be exhaustive, and all obvious variations or modifications may be included within the scope of the present invention.

Claims

1. The catalyst base material is characterized in that the catalyst base material is poly-2, 6-diaminopyridine, and the poly-2, 6-diaminopyridine is prepared by oxidizing and polymerizing cyanamide and 2, 6-diaminopyridine.

2. The catalyst substrate material according to claim 1, wherein the molar ratio of the cyanamide to the 2, 6-diaminopyridine is 1:2 to 12; preferably, the preparation of the poly-2, 6-diaminopyridine is carried out in a rotating packed bed reactor.

3. A method for producing the catalyst base material according to claim 1 or 2, comprising the steps of: the catalyst base material is prepared by oxidizing and polymerizing cyanamide and 2, 6-diaminopyridine;

4. The method for producing a catalyst base material according to claim 3, characterized by specifically comprising the steps of:

5. The method for preparing a catalyst base material according to claim 4, wherein the alkaline solution in step 1) is an aqueous sodium hydroxide solution having a concentration of 7.57 to 15.15 mg/L; preferably, the oxidant in step 1) is ammonium persulfate, potassium persulfate or sodium persulfate;

preferably, the volume ratio of the feed liquid A to the feed liquid B in the step 1) is 5-1: 1;

preferably, the volumes of the feed liquid A and the feed liquid B in the step 1) are both 240 mL;

preferably, the molar ratio of the oxidizing agent to 2, 6-diaminopyridine in step 1) is greater than or equal to 1: 1;

preferably, the supergravity horizontal value of the rotary packed bed reactor in the step 2) is 50-250;

preferably, the temperature of the reaction in step 2) is less than or equal to 20 ℃;

preferably, the reaction time in the step 2) is 40-50 s;

preferably, the feed liquid A and the feed liquid B in the step 2) are pumped into a rotating packed bed reactor by a peristaltic pump;

preferably, the feeding speed of the peristaltic pump is 240-480 mL/min;

preferably, the stirring speed in the step 3) is 300-500 rpm;

preferably, the temperature of the stirring reaction in step 3) is less than or equal to 20 ℃;

preferably, the stirring reaction time in the step 3) is 150-720 min;

6. A transition metal-nitrogen co-doped pyrolytic polypyridine carbon-based electrocatalytic material, which is characterized by comprising the catalyst substrate material as defined in claim 1 or 2 and a transition metal doped in the catalyst substrate material; wherein the catalyst substrate material is poly 2, 6-diaminopyridine.

7. The transition metal-nitrogen co-doped pyrolytic polypyridine carbon-based electrocatalytic material as claimed in claim 6, wherein the transition metal-nitrogen co-doped pyrolytic polypyridine carbon-based electrocatalytic material has a specific surface area of 640-720 m²/g；

Preferably, the transition metal is transition metal iron and/or transition metal manganese;

preferably, the transition metal-nitrogen co-doped pyrolytic polypyridine carbon-based electrocatalytic material is prepared by carrying a transition metal precursor on poly (2, 6-diaminopyridine) through pyrolysis;

preferably, the transition metal precursor is a transition metal iron precursor and/or a transition metal manganese precursor;

preferably, the transition metal iron precursor is one or more of ferric nitrate, ferric chloride and ferric acetate, and more preferably ferric nitrate;

preferably, the transition metal manganese precursor is one or more of manganese nitrate, manganese acetate and manganese chloride, and more preferably is manganese acetate;

preferably, the molar ratio of the transition metal iron precursor to the transition metal manganese precursor is 1: 0.025-2;

preferably, the preparation process of the transition metal-nitrogen co-doped pyrolytic polypyridine carbon-based electrocatalytic material is carried out in a rotating packed bed reactor.

8. The preparation method of the transition metal-nitrogen co-doped pyrolytic polypyridine carbon-based electrocatalytic material as in claim 6 or 7, comprising the following steps:

the transition metal-nitrogen co-doped pyrolytic polypyridine carbon-based electrocatalytic material is prepared by loading a transition metal precursor on the catalyst substrate material of claim 1 or 2 and performing pyrolysis; wherein the catalyst substrate material is poly 2, 6-diaminopyridine;

9. The preparation method of the transition metal-nitrogen co-doped pyrolytic polypyridine carbon-based electrocatalytic material as claimed in claim 8, comprising the following steps:

s3, pyrolyzing the product D to obtain a product E;

s4, carrying out acid washing and separation on the product E, and then carrying out secondary pyrolysis to obtain the transition metal-nitrogen co-doped pyrolytic polypyridine carbon-based electrocatalytic material;

preferably, the concentration of the feed liquid C in the step S1 is 0.5-20 mg/mL;

preferably, the concentration of the feed liquid D in the step S1 is 1-3 mg/mL;

preferably, the amount of the poly-2, 6-diaminopyridine used in step S1 is 200-1000 mg;

preferably, the volume of the feed liquid C in the step S1 is 60-300 mL;

preferably, the volume ratio of the feed liquid D to the feed liquid C in step S2 is 1: 3-12;

preferably, the temperature of the reaction in the step S2 is 60-80 ℃;

preferably, the reaction time in the step S2 is 5-7 h;

preferably, the hypergravity horizontal value of the rotating packed bed reactor in the step S2 is 100-200, and more preferably 150;

preferably, the drying in step S2 is vacuum drying; the drying temperature is preferably 60-80 ℃, and more preferably 70 ℃; the drying time is preferably 3-6 h;

preferably, in the step S3, the pyrolysis process is to heat the mixture to 800-1200 ℃ at a heating rate of 4-6 ℃/min in a nitrogen atmosphere, keep the temperature for 2-4 h, and naturally cool the mixture;

preferably, the pyrolysis in step S3 is performed in a tube furnace;

preferably, the acid washing in the step S4 is washing in sulfuric acid for 8-9 h;

preferably, the concentration of the sulfuric acid is 0.4-0.6 mol/L;

preferably, the acid washing in the step S4 is carried out at the temperature of 80-95 ℃;

10. The application of the transition metal-nitrogen co-doped pyrolytic polypyridine carbon-based electrocatalytic material as defined in claim 6 or 7 as a negative oxygen reduction reaction catalyst in a zinc-air battery.