阅读说明：本技术 一种CoN析氧和氧还原电催化剂制备方法 (Preparation method of CoN oxygen evolution and oxygen reduction electrocatalyst ) 是由 杨秀林 郭嫚 胡艳 于 2021-08-09 设计创作，主要内容包括：本发明涉及金属-空气电池技术领域,具体为一种CoN析氧和氧还原电催化剂的制备方法,本发明通过水热及低温氮化处理的方法得到CoN催化材料,所述水热是将钴生长在碳布上,获得Co LDH前驱体；将所述钴基前驱体在氨气气氛下进行低温氮化处理。本发明制备方法简单,在碱性条件下具有优异的电催化析氧和氧还原性能,其作为空气阴极组装锌-空气电池时,表现出良好的长期稳定性和可观的功率密度,在锌-空气电池方面展现出了实际应用潜力。(The invention relates to the technical field of metal-air batteries, in particular to a preparation method of a CoN oxygen evolution and oxygen reduction electrocatalyst, wherein a CoN catalytic material is obtained by a hydrothermal and low-temperature nitridation treatment method, cobalt grows on carbon cloth in the hydrothermal process, and a Co LDH precursor is obtained; and carrying out low-temperature nitridation treatment on the cobalt-based precursor in an ammonia atmosphere. The preparation method is simple, has excellent electrocatalytic oxygen evolution and oxygen reduction performance under an alkaline condition, shows good long-term stability and considerable power density when being used as an air cathode to assemble the zinc-air battery, and shows practical application potential in the aspect of the zinc-air battery.)

1. A preparation method of a CoN oxygen evolution and oxygen reduction electrocatalyst is characterized by comprising the following steps: the method comprises the steps of obtaining a CoN material by a hydrothermal reaction and a low-temperature nitriding treatment method, wherein the hydrothermal reaction takes carbon cloth as a substrate to grow a cobalt-based precursor; and carrying out low-temperature nitridation treatment on the cobalt-based precursor in an ammonia atmosphere to obtain the CoN material.

2. The method of claim 1, wherein: the cobalt-based precursor is prepared by ultrasonically dissolving cobalt acetate tetrahydrate and polyvinylpyrrolidone into an ethylene glycol solution to obtain a mixed solution, adding a methanol solution, stirring for 30 minutes, and then placing carbon in the mixed solution to perform hydrothermal reaction.

3. The method of claim 2, wherein: the hydrothermal reaction temperature is 120 ℃, and the reaction time is 12 hours.

4. The production method according to claim 3, characterized in that: the low-temperature nitriding treatment is carried out by raising the temperature to 200-400 ℃ at a rate of 5 ℃/min, keeping the temperature for 3 hours, and then naturally cooling to room temperature.

Technical Field

The invention belongs to the field of metal-air batteries, and particularly relates to a preparation method of a CoN oxygen evolution and oxygen reduction electrocatalyst.

Background

The development of high-efficiency non-noble metal-based oxygen evolution and reduction electrocatalysts is a necessary way to improve zinc-air batteries. Despite the tremendous efforts of scientists, the slow kinetics of oxygen evolution and oxygen reduction still limit the practical applications of zinc-air cells. In recent years, the abundance of transition metals on earth has attracted much attention and research by scientists, wherein ruthenium and platinum-based electrocatalysts exhibit excellent electrocatalytic properties in oxygen evolution and oxygen reduction reactions, respectively, but their large-scale commercial applications are limited by the disadvantages of scarcity, poor stability, high cost, and the like. Therefore, the development of a non-noble metal-based catalyst with low cost, high efficiency and abundant earth reserves is of great significance to the rechargeable zinc-air battery.

Disclosure of Invention

The invention aims to provide a preparation method of a CoN oxygen evolution and oxygen reduction electrocatalyst, and solves the problems in the background technology.

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

a preparation method of a CoN oxygen evolution and oxygen reduction electrocatalyst comprises the steps of obtaining a CoN material by a hydrothermal reaction and a low-temperature nitridation treatment method, wherein the hydrothermal reaction takes carbon cloth as a substrate to grow a cobalt-based precursor; and carrying out low-temperature nitridation treatment on the cobalt-based precursor in an ammonia atmosphere to obtain the CoN material.

Further, the cobalt-based precursor is prepared by ultrasonically dissolving cobalt acetate tetrahydrate and polyvinylpyrrolidone in an ethylene glycol solution to obtain a mixed solution, adding a methanol solution, stirring for 30 minutes, and then placing carbon in the mixed solution to perform hydrothermal reaction.

Further, the hydrothermal reaction temperature is 120 ℃, and the reaction time is 12 hours.

Further, the low-temperature nitriding treatment is carried out by raising the temperature to 200-400 ℃ at a rate of 5 ℃/min, keeping the temperature for 3 hours, and then naturally cooling to room temperature.

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

the preparation method is simple, the CoN catalytic material is obtained by performing simple hydrothermal and low-temperature nitridation treatment on carbon cloth, the CoN catalytic material has excellent electrocatalytic oxygen evolution and oxygen reduction performances under an alkaline condition, and when the CoN catalytic material is used as an air cathode to assemble a zinc-air battery, the CoN catalytic material shows good long-term stability and considerable power density, and shows practical application potential in the aspect of the zinc-air battery.

Drawings

FIG. 1X-ray powder diffraction pattern of CoN-300/CC prepared in example 1 of the present invention;

FIG. 2X-ray powder diffraction patterns of composites prepared according to examples 2 and 3 of the present invention;

FIG. 3X-ray powder diffraction patterns of CoN materials prepared by examples 4 and 5 of the present invention;

FIG. 4 is a linear scanning curve of electrocatalytic oxygen evolution of the catalytic materials prepared in examples 1, 2 and 3 of the present invention;

FIG. 5 is a linear scanning curve of electrocatalytic oxygen evolution of the catalytic materials prepared in examples 1, 4 and 5 of the present invention;

FIGS. 6 (a-c) are scanning electron micrographs of carbon cloth, Co LDH and CoN-300/CC of example 1 of the present invention; FIG. 6 (d) is a transmission electron micrograph; FIG. 6 (e) is a selected area electron diffraction pattern; FIG. 6 (f) shows a high resolution TEM image and lattice fringes; FIG. 6 (g) is a transmission electron microscope image of a high-angle annular dark field and the elements are uniformly distributed in the catalytic material;

FIG. 7 is an X-ray photoelectron spectrum of the CoN catalytic material of the present invention at different temperatures;

FIG. 8 shows the Co LDH precursor, the material at different temperatures for nitridation and the noble metal RuO prepared in example 1 of the present invention₂The formed oxygen evolution linear scanning curve;

FIG. 9 is a long term stability curve of CoN material prepared in example 1 of the present invention at high current density in 1.0M KOH;

FIG. 10 is a linear scan curve of the electrocatalytic oxygen reduction under alkaline conditions for example 1 of the present invention;

FIG. 11 long-term stability curves for electrocatalytic oxygen reduction under alkaline conditions for example 1 of the present invention;

fig. 12 (a) shows the polarization curve and power density curve of the zinc-air battery under alkaline conditions in example 1 of the present invention, and (b) shows the long-term stability of the zinc-air battery under alkaline conditions in example 1 of the present invention.

Detailed Description

The technical solution in the embodiment of the present invention will be described below with reference to fig. 1 to 12 in the embodiment of the present invention.

Firstly, firstly preparing RuO₂As an electrode sampleArticle, for comparison with the examples of the invention: weighing 2 mg of RuO₂Dissolving the RuO in 495 muL deionized water, 495 muL absolute ethyl alcohol and 10 muL Nafion solution, carrying out ultrasonic treatment for 30 minutes, and uniformly dispersing the RuO₂The slurry drops at 1 cm²And drying the carbon cloth at room temperature for later use.

Commercial Pt/C was selected as the electrode sample for comparison with the inventive examples: weighing 2 mg of commercial Pt/C, dissolving the Pt/C in 100 muL deionized water, 300 muL isopropanol and 10 muL Nafion solution, carrying out ultrasonic treatment for 30 minutes, and dropping the Pt/C slurry after uniform dispersion on a glassy carbon electrode with the diameter of 5.61 mm (the loading amount is 0.1 mg cm)^-2) And drying at room temperature for later use.

II, zinc-air battery cathode catalyst:

first, commercial Pt/C and RuO were prepared₂As electrode samples, for comparison with examples of the present invention: weighing 1 mg commercial Pt/C and 1 mg RuO₂Dissolving the mixture in 100 muL deionized water, 300 muL isopropyl alcohol and 10 muL Nafion solution, carrying out ultrasonic treatment for 30 minutes, and uniformly dispersing Pt/C and RuO by ultrasonic treatment₂The mixed slurry drops at 1.5 x 2 cm²The loading amount of the carbon paper is 1 mg cm^-2And drying at room temperature for later use.

Third, example 1: preparation of CoN-300/CC Material

Treating the carbon cloth in the step (1): cutting carbon cloth into 1 × 1.5 cm²Size. Then ultrasonic washing is carried out for 15 minutes in 0.5 mol/L sulfuric acid solution, deionized water and ethanol respectively, the washing is carried out for three times in a circulating way, and the washing is naturally dried for standby.

Preparing a cobalt acetate solution in the step (2): 200 mg of cobalt acetate tetrahydrate and 400 mg of PVP were weighed out and dissolved in 7.5 mL of ethylene glycol solution by ultrasonic wave, and 22.5 mL of methanol solution was added and stirred vigorously for 30 minutes.

Step (3) hydrothermal reaction: and (3) placing the carbon cloth treated in the step (1) into the solution in the step (2), and keeping the temperature in an oven at 120 ℃ for 12 hours. And after natural cooling, washing the carbon cloth with a large amount of water, and airing at room temperature for later use to obtain the CoLDH/CC cobalt-based precursor material.

Step (4), nitriding treatment: and (4) placing the carbon cloth of the cobalt-based precursor in the step (3) in the middle of a quartz tube, heating to 200, 300 and 400 ℃ at a heating rate of 5 ℃/min in an ammonia atmosphere, keeping for 3 hours, naturally cooling to room temperature, taking out, washing with a large amount of deionized water, and airing at room temperature to obtain the CoN material prepared at different temperatures. If not stated otherwise, example 1 refers to the nitriding of the resulting material CoN-300 at 300 ℃.

Fourth, example 2: preparation of CoN-CoCH/CC Material

Treating the carbon cloth in the step (1): cutting carbon cloth into 1 × 1.5 cm²Size. Then ultrasonic washing is carried out for 15 minutes in 0.5 mol/L sulfuric acid solution, deionized water and ethanol respectively, the washing is carried out for three times in a circulating way, and the washing is naturally dried for standby.

Preparing a cobalt nitrate solution: weighing 2 mmol of cobalt nitrate hexahydrate and 10 mmol of urea, dissolving in 35 mL of deionized water, and vigorously stirring for 30 minutes to obtain a cobalt nitrate solution with the concentration of 0.06 mol/L.

Step (3) hydrothermal reaction: a piece of carbon cloth was placed in a 100 mL reaction vessel and kept at 120 ℃ in an oven for 6 hours. And after natural cooling, washing the carbon cloth with a large amount of water, and airing at room temperature for later use.

Step (4), nitriding treatment: and (4) placing the carbon cloth containing the cobalt-based precursor in the step (3) in the middle of a quartz tube, heating to 300 ℃ at a heating rate of 5 ℃/min in an ammonia atmosphere, keeping for 3 hours, naturally cooling to room temperature, taking out, washing with a large amount of deionized water, and airing at room temperature to obtain the CoN-CoCH/CC material.

Fifth, example 3: preparation of ZIF 67-N₃₀₀[ CC ] Material

Treating the carbon cloth in the step (1): cutting carbon cloth into 1 × 1.5 cm²Size. Then ultrasonic washing is carried out for 15 minutes in 0.5 mol/L sulfuric acid solution, deionized water and ethanol respectively, the washing is carried out for three times in a circulating way, and the washing is naturally dried for standby.

Preparing a cobalt nitrate solution: 1.6 mmol of cobalt nitrate hexahydrate and 8.0 mmol of dimethyl imidazole are weighed and dissolved in 20 mL of deionized water, and the mixture is stirred for 10 minutes to obtain a cobalt nitrate solution with the concentration of 0.08 mol/L.

And (3) reacting at room temperature: a piece of carbon cloth was placed in the solution of step (2) and stirred at room temperature for 6 hours. And then washing the carbon cloth with a large amount of water, and airing at room temperature for later use.

Step (4), nitriding treatment: placing the carbon cloth containing the cobalt-based precursor in the step (3) in the middle of a quartz tube, heating to 300 ℃ at a heating rate of 5 ℃/min in an ammonia atmosphere, keeping for 3 hours, naturally cooling to room temperature, taking out, washing with a large amount of deionized water, and airing at room temperature to obtain ZIF 67-N₃₀₀/CC。

Sixth, example 4: preparation of CoN-P₁₂₃[ CC ] Material

Treating the carbon cloth in the step (1): cutting carbon cloth into 1 × 1.5 cm²Size. Then ultrasonic washing is carried out for 15 minutes in 0.5 mol/L sulfuric acid solution, deionized water and ethanol respectively, the washing is carried out for three times in a circulating way, and the washing is naturally dried for standby.

Preparing a cobalt acetate solution in the step (2): 200 mg of cobalt acetate tetrahydrate and 400 mg of P were weighed out₁₂₃Dissolved in 7.5 mL of ethylene glycol solution, and then 22.5 mL of methanol solution was added thereto and stirred vigorously for 30 minutes.

Step (3) hydrothermal reaction: placing a piece of carbon cloth in the solution of the step (2), and keeping the temperature in an oven at 120 ℃ for 12 hours. And naturally cooling, washing the carbon cloth with a large amount of water, and airing at room temperature for later use.

Step (4), nitriding treatment: placing the carbon cloth containing the cobalt-based precursor in the step (3) in the middle of a quartz tube, heating to 300 ℃ at a heating rate of 5 ℃/min in an ammonia atmosphere, keeping for 3 hours, naturally cooling to room temperature, taking out, washing with a large amount of deionized water, and airing at room temperature to obtain CoN-P₁₂₃a/CC material.

Seventhly, embodiment 5: preparation of CoN-F₁₂₇[ CC ] Material

Treating the carbon cloth in the step (1): cutting carbon cloth into 1 × 1.5 cm²Size. Then ultrasonic washing is carried out for 15 minutes in 0.5 mol/L sulfuric acid solution, deionized water and ethanol respectively, the washing is carried out for three times in a circulating way, and the washing is naturally dried for standby.

Preparing a cobalt acetate solution in the step (2): 200 mg of cobalt acetate tetrahydrate and 400 mg of F were weighed out₁₂₇Dissolved in 7.5 mL of ethylene glycol solution and added22.5 mL of methanol solution was added and stirred vigorously for 30 minutes.

Step (3) hydrothermal reaction: placing a piece of carbon cloth in the solution of the step (2), and keeping the temperature in an oven at 120 ℃ for 12 hours. And naturally cooling, washing the carbon cloth with a large amount of water, and airing at room temperature for later use.

Step (4), nitriding treatment: placing the carbon cloth containing the cobalt-based precursor in the step (3) in the middle of a quartz tube, heating to 300 ℃ at a heating rate of 5 ℃/min in an ammonia atmosphere, keeping for 3 hours, naturally cooling to room temperature, taking out, washing with a large amount of deionized water, and airing at room temperature to obtain CoN-F₁₂₇a/CC material.

Eight, electrochemical testing

Electrochemical test (1): the electrochemical oxygen evolution test was carried out on an electrochemical workstation (Bio-Logic VMP3, France) using a three-electrode system. The CoN-300/CC material prepared in example 1 is used as a working electrode, a graphite plate is used as a counter electrode, a saturated calomel electrode is used as a reference electrode, 1.0 mol/L potassium hydroxide solution is used as an electrolyte, the test temperature is 25 ℃, the scanning speed is 10 mV/s, and the scanning range is-0.9 to-1.5V. The electrode potential was obtained by applying a saturated calomel electrode, and a Reversible Hydrogen Electrode (RHE) and impedance compensation correction were performed. All oxygen evolution potentials herein are obtained according to the following nernst equation:

E_RHE = E_SCE+0.241+0.059pH-iR

whereiniFor the current tested, R is the solution impedance.

Electrochemical test (2): electrochemical oxygen reduction tests were performed on an electrochemical workstation (shanghai CHI 760E and U.S. PINE) using a three-electrode system. The CoN-300 catalyst prepared in example 1 was dropped on a glassy carbon electrode as a working electrode, a carbon rod as a counter electrode, a saturated silver-silver chloride electrode as a reference electrode, and a 0.1 mol/L potassium hydroxide solution as an electrolyte, and the test temperature was 25 ℃, the scanning speed was 10 mV/s, and the scanning range was-0.9 to-0.2V. The electrode potential was obtained for a saturated silver-silver chloride electrode and corrected for a Reversible Hydrogen Electrode (RHE). All oxygen reduction potentials herein are obtained according to the following nernst equation:

E_RHE = E_Ag/AgCl + 0.196 + 0.059pH

electrochemical test (3): zinc-air cell testing was performed on an electrochemical workstation (shanghai CHI 760E) and a blue cell testing system (BT 2016A). The CoN-300/CC material prepared in example 1 was used as an air cathode, a zinc plate was used as an anode, a mixed solution of 6 mol/L potassium hydroxide and 0.2 mol/L zinc acetate was used as an electrolyte, and the test temperature was 25 ℃. The power density is obtained according to the following equation:

P = UI

sixth, test results

FIG. 1 shows that the sample of example 1 has characteristic peaks typical of CoN in X-ray powder diffraction.

FIG. 2 (a) shows X-ray powder diffraction patterns of the composite materials prepared in examples 2 and 3, and it can be seen that the cobalt-based precursor of example 1 is not completely converted into CoN after nitriding at 300 ℃, but is a composite of CoN and other substances; example 2 had no significant characteristic diffraction peak of CoN after nitridation.

Fig. 3 shows that the samples prepared in examples 4 and 5 have characteristic peaks typical of the X-ray powder diffraction of CoN, and it can be seen that changing the kind of surfactant during the synthesis process does not affect the crystal form of the nitrided CoN.

FIG. 4 shows that CoN-300 prepared by the present invention has more excellent oxygen evolution performance than examples 2 and 3.

FIG. 5 shows that the CoN-300 prepared by the surfactant used in the present invention has better oxygen evolution performance than those of examples 4 and 5.

FIG. 6 (a) is a graph of carbon cloth, Co LDH/CC and CoN-300/CC under a scanning electron microscope of example 1, showing that a large amount of plate-like substances are grown on the carbon cloth; FIG. 2 (d) shows a view under a transmission electron microscope; FIG. 2 (e) shows a selected area electron diffraction pattern; FIG. 2 (f) shows a high resolution TEM image and lattice fringes; FIG. 2 (g) shows a transmission electron microscope image of a high-angle annular dark field and the elements are uniformly distributed in the material.

FIG. 7 shows that the relative peak strength of Co-N is strongest and the surface percentage is as high as 89.1% at 300 ℃ nitridation temperature, indicating that 300 ℃ is most favorable for the formation of Co-N bonds, thereby increasing catalyst activity.

FIG. 8 shows CoN-300 prepared by the present invention at a current density of 10 mA cm^-2The lowest overpotential (243 mV) under the condition proves that the CoN-300 prepared by the invention has excellent oxygen evolution performance.

FIG. 9 shows CoN-300 prepared by the present invention at 100 mA cm^-2The stability under high current density is as long as 100 h, and the potential has no obvious change, which proves that the CoN-300 prepared by the invention has excellent stability.

FIG. 10 shows the linear curve of electrocatalytic oxygen reduction of CoN-300 prepared by the present invention under alkaline conditions, and it can be seen that the limiting current density is greater than that of the most advanced Pt/C catalyst, indicating that CoN-300 prepared by the present invention has excellent oxygen reduction characteristics.

FIG. 11 shows the oxygen reduction stability of CoN-300 prepared by the present invention under alkaline conditions, and after 4000 seconds of continuous operation, CoN-300 maintained 92.5% of the initial current density, indicating that the catalyst prepared by the present invention has good oxygen reduction stability.

FIG. 12 shows the application of the CoN-300 material prepared by the invention in a zinc-air battery. Graph (a) shows that the power density of CoN-300 is significantly higher than commercial Pt/C and RuO₂Mixing a catalyst; and (b) is a cycle stability test of the zinc-air battery, the performance is hardly degraded after the continuous operation for 260 circles, and the CoN-300 material prepared by the invention has better stability.

Comparing examples 1, 2, 3, 4 and 5, example 1 carries out simple hydrothermal reaction, carbon cloth with Co LDH precursor growing thereon is subjected to nitridation treatment at different temperatures, and the CoN-300 material obtained when the nitridation temperature is 300 ℃ has excellent oxygen evolution and oxygen reduction activity and stability. Example 2, performing a simple hydrothermal reaction, and directly performing low-temperature nitridation treatment on the carbon cloth on which the cobalt-based precursor grows to obtain CoN-CoCH/CC; example 3 a cobalt-based precursor was grown on a carbon cloth at room temperature, naturally dried, and then subjected to low-temperature nitridation treatment,obtaining ZIF 67-N₃₀₀(ii)/CC; example 4 simple hydrothermal reaction was performed to obtain CoN-P by subjecting carbon cloth on which a cobalt precursor was grown to low-temperature nitridation₁₂₃(ii)/CC; example 5 simple hydrothermal reaction and Low-temperature nitridation treatment of carbon cloth on which a cobalt precursor was grown to obtain CoN-F₁₂₇and/CC. As shown in fig. 4, 5, 8, example 1 showed better electrocatalytic oxygen evolution performance under alkaline conditions than examples 2, 3, 4, 5; as shown in FIGS. 10 and 11, example 1 exhibited-5.2 mA cm under alkaline conditions^-2Current density and excellent stability over commercial Pt/C catalysts (-4.9 mA cm)^-2) The CoN-300 prepared by the invention has better electrocatalytic oxygen reduction performance; as shown in FIG. 12, the power density of the zinc-air battery assembled by the CoN-300 prepared by the invention reaches 120 mW cm^–2And after the continuous cyclic operation for 260 circles, no obvious decline exists, and the CoN-300 prepared by the invention is proved to have the potential of practical application in zinc-air batteries.

In conclusion, the CoN-300 catalytic material is obtained by simple hydrothermal and low-temperature nitridation treatment on the carbon cloth, has excellent electrocatalytic oxygen evolution and oxygen reduction performance under alkaline conditions, and has long service life. When the zinc-air battery is assembled as an air cathode, the zinc-air battery shows good long-term stability and considerable power density, and shows practical application potential in the aspect of zinc-air batteries.

While the invention has been described with reference to a preferred embodiment, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention.