CN108816258B - In-situ doped hollow cobalt phosphide nanoparticle hollow carbon material, preparation method and application thereof in catalytic electrolysis of water for hydrogen production - Google Patents

Abstract

The invention discloses a preparation method of a hollow carbon material with dodecahedral morphology doped with hollow cobalt phosphide nanoparticles in situ and its application in the catalytic electrolysis of water for hydrogen production, belonging to the technical field of catalytic electrolysis of water for hydrogen production. The specific steps are: (1) preparation of metal-organic framework material ZIF-67 containing cobalt ions with dodecahedral morphology; (2) reaction of cobalt-containing metal framework material ZIF-67 with dopamine monomer to generate cobalt-containing complex Site-doped hollow polymer nanomaterials; (3) preparation of cobalt oxide/carbon composite hollow nanomaterials; (4) preparation of hollow cobalt phosphide/carbon composite hollow nanomaterials. The size of the material can be adjusted according to the size of ZIF-67; in the performance test of catalytic electrolysis of water for hydrogen production, the electrode material used as the cathode showed very good electrocatalytic activity and stability. Therefore, the material of the present invention has a very good application prospect as an electrode material for catalyzing the electrolysis of water for hydrogen production.

Description

In-situ doped hollow cobalt phosphide nanoparticle hollow carbon material and preparation method and its application in catalytic electrolysis of water for hydrogen production

technical field

The invention belongs to the technical field of catalytic electrolysis of water for hydrogen production, and in particular relates to a hollow carbon material with dodecahedral morphology doped with hollow cobalt phosphide nanoparticles in situ, a preparation method and its application in catalytic electrolysis of water for hydrogen production.

Background technique

Due to the global energy crisis and related environmental problems, researchers are making efforts to find renewable energy sources that can replace fossil fuels. Hydrogen production from water electrolysis is a very promising approach. Due to the advantages of high energy conversion efficiency, almost no pollution, and broad application prospects, electrolysis of water for hydrogen production has attracted extensive attention of researchers on electrode materials. At present, platinum group metals have the highest hydrogen production activity, but the disadvantages of high cost and low yield limit their wide application. Therefore, the exploration of non-precious metal materials with high catalytic activity has received more attention. Although many emerging materials have some obvious advantages compared to noble metal materials, there are still some shortcomings in current hydrogen-producing electrode materials, such as complex fabrication process, low catalytic activity, and small specific surface area. There are two main factors that affect the catalytic activity, one is the interaction energy between metal and hydrogen, and the other is the structure and specific surface area of the material. In this regard, using a hollow carbon material with a large specific surface area and supporting transition metal nanoparticles with high hydrogen adsorption capacity in it can effectively overcome the above problems. For example, Chen's research group used the metal-organic framework material ZIF-8@ZIF-67 with a core-shell structure as a template ^[1] , and after carbonization and phosphating, a composite material with a hollow structure and containing cobalt phosphide nanoparticles was prepared. The material exhibits excellent catalytic water electrolysis for hydrogen and oxygen production (overpotentials are 115mV and 310mV, respectively, at a current density of 10mA/cm ^-2 ).

Based on this, the present invention proposes a hollow nano-material of hollow metal phosphide and carbon composite as an electrode material to be used in catalytic electrolysis of water for hydrogen production. The cobalt-loaded polymer hollow nanomaterials are prepared by the method of coordination competition induced polymerization, and then carbonized and phosphated to obtain hollow carbon materials containing hollow cobalt phosphide particles. catalytic activity and stability.

SUMMARY OF THE INVENTION

The purpose of the present invention is to provide a hollow cobalt phosphide/carbon composite hollow carbon material with dodecahedral morphology doped with hollow cobalt phosphide nanoparticles in situ, a preparation method and its application in catalytic electrolysis of water to produce hydrogen. By loading hollow metal phosphide in hollow carbon nanoparticles with dodecahedral morphology, the catalytic activity of the material can be effectively improved. At the same time, the hollow material can provide more active sites, improve the overall stability of the material, make the material have a longer service life, and be more suitable for actual production.

In the present invention, the metal organic framework material ZIF-67 containing cobalt ions is used as a template, and the cobalt ion-doped hollow polymer nanomaterial is prepared by the method of coordinating competition induced polymerization. Then, high temperature carbonization is carried out under the protection of an inert gas atmosphere to obtain a cobalt oxide/carbon composite hollow nanomaterial. Finally, the material is phosphated to convert the cobalt oxide into hollow cobalt phosphide nanoparticles to obtain hollow cobalt phosphide/carbon composite hollow nanomaterials. The material exhibits excellent performance and excellent stability in catalytic electrolysis of water for hydrogen production.

The raw materials used in the present invention are all commercially available substances, the reaction process is simple, the experimental operation is simple, the conditions are mild, the danger is small, and the invention has very good repeatability and can be mass-produced.

The hollow cobalt phosphide/carbon composite hollow carbon material with dodecahedral morphology and in-situ doped hollow cobalt phosphide nanoparticles according to the present invention can be prepared by the following steps: (1) a cobalt ion containing Preparation of metal-organic framework material ZIF-67 with dodecahedral morphology; (2) Cobalt-containing metal framed material ZIF-67 reacts with dopamine monomer to generate cobalt-coordinated doped hollow polymer nanomaterials; (3) ) Preparation of cobalt oxide/carbon composite hollow nanomaterials; (4) preparation of hollow cobalt phosphide/carbon composite hollow nanomaterials. specifically,

(1) Preparation of metal-organic framework material ZIF-67 containing cobalt ions with dodecahedral morphology: 200-1000 mg of Co(NO ₃ ) ₂ ·6H ₂ O and 500-3000 mg of 2-methylimidazole were prepared separately Dissolve in 25-100mL methanol to obtain a clear solution, then mix the two solutions evenly to obtain a purple solution and stand at room temperature for 6-24h; then the above reaction product is processed by centrifugation (3000-5000rpm, 10-15min), and used Washing with methanol for 3 to 5 times, drying at 40 to 60 °C for 10 to 15 h, to obtain a metal-organic framework material ZIF-67 containing cobalt ions with dodecahedral morphology;

(2) Preparation of hollow polymer nanomaterials containing cobalt coordination doping: Weigh 40-60 mg of ZIF-67 prepared in step (1), and disperse it in 50-75 mL of methanol to obtain ZIF-67 dispersion; Then, take 10-15 mL of methanol solution of 20 mM dopamine hydrochloride, mix the ZIF-67 dispersion obtained earlier with the methanol solution of dopamine hydrochloride, and place the reaction system at 40-60 ℃ under reflux and stir for 6-12 h, to obtain The product was centrifuged (3000-5000rpm, 8-15min), and washed with methanol for 3-5 times until the supernatant was colorless and clear; the supernatant was removed, and the solid product was retained to obtain a cobalt-coordinated doped hollow polymer nanomaterials;

(3) Preparation of cobalt oxide/carbon composite hollow nanomaterials: The hollow polymer nanomaterials containing cobalt coordination doping prepared in step (2) were carbonized at 700-800 °C under the protection of argon gas for 2 ~4h (the heating rate is 3~5℃/min), and after cooling to room temperature, the cobalt oxide/carbon composite hollow nanomaterial is obtained;

(4) Preparation of hollow cobalt phosphide/carbon composite hollow nanomaterials: under the protection of argon, the cobalt oxide/carbon composite hollow nanomaterials obtained in step (3) are phosphated, and the phosphorus source is NaH ₂ PO ₂ ·H ₂ O, the phosphating temperature is 300-400°C, the phosphating time is 1-3h (the heating rate is 2-5°C/min), and the in-situ doped hollow phosphating according to the present invention is obtained after cooling to room temperature Cobalt nanoparticle hollow cobalt phosphide/carbon composite hollow carbon material with dodecahedral morphology.

Description of drawings

Figure 1: Transmission electron microscope and scanning electron microscope photos of the hollow cobalt phosphide/carbon composite hollow nanomaterial prepared in Example 1; (A) is a photo of a transmission electron microscope, and (B) is a photo of a scanning electron microscope;

Figure 2: Transmission electron microscope and scanning electron microscope pictures of the hollow cobalt phosphide/carbon composite hollow nanomaterial prepared in Example 2. (A) is the photo of transmission electron microscope, (B) is the photo of scanning electron microscope;

Figure 3: X-ray diffraction pattern of the hollow cobalt phosphide/carbon composite hollow nanomaterial prepared in Example 1;

Figure 4: The performance curve of the catalytic electrolysis of water for hydrogen production of the hollow cobalt phosphide/carbon composite hollow nanomaterial prepared in Example 1; (A) is the linear voltammetry scan curve, (B) is the Tafel slope curve, (C) is the Hydrogen production stability test curve, (D) is the AC impedance spectrum curve.

Detailed ways

The present invention will be further described below with reference to examples, rather than limiting the present invention.

Example 1

(1) Preparation of metal-organic framework material ZIF-67 with dodecahedral morphology containing cobalt ions: 498 mg of Co(NO ₃ ) ₂ ·6H ₂ O and 1400 mg of 2-methylimidazole were dissolved in 50 mL of methanol, respectively , and then the two solutions were mixed uniformly to obtain a purple solution and allowed to stand at room temperature for 6 h. The product was purified by centrifugation (5000rpm, 10min), washed three times with methanol, and dried at 60°C for 12h. Finally, a metal-organic framework material ZIF-67 with a dodecahedron morphology was obtained with a product mass of 400mg.

(2) Preparation of hollow polymer nanomaterials containing cobalt coordination doping: Weigh 60 mg of ZIF-67 prepared in step (1) and disperse it in 75 mL of methanol. Then, 56.9 mg of dopamine hydrochloride was weighed and dissolved in 15 mL of methanol to prepare a dopamine solution. The ZIF-67 dispersion was mixed with the dopamine solution, and the reaction system was placed at 60°C under reflux for stirring for 6h. The obtained product was processed by centrifugation (5000 rpm, 10 min) and washed three times with methanol until the supernatant was colorless and clarified to obtain a cobalt-containing polymer hollow nanomaterial with a product mass of 25 mg.

(3) Preparation of cobalt oxide/carbon composite hollow nanomaterials: The prepared hollow polymer nanomaterials were carbonized at 700 °C for 2 h under the protection of argon (the heating rate was 5 °C/min), and after cooling to room temperature , the cobalt oxide/carbon composite hollow nanomaterial was obtained, and the product mass was 20 mg.

(4) Preparation of hollow cobalt phosphide/carbon composite hollow nanomaterials: under the protection of argon, put 20 mg of the hollow material obtained in step (3) on one end of the porcelain boat, and put 500 mg of NaH _on the other end. The PO ₂ ·H ₂ O was phosphated at a temperature of 300°C and a phosphating time of 2h (heating rate of 3°C/min). After cooling to room temperature, the in-situ doped hollow phosphating of the present invention was obtained. Cobalt nanoparticles are hollow carbon materials with dodecahedral morphology, and the product mass is 22 mg.

The prepared hollow cobalt phosphide/carbon composite hollow nanomaterial has a size of about 200-260 nm, its morphology maintains the dodecahedral shape of the template material ZIF-67, and has a hollow structure at the same time, and the hollow cobalt phosphide particles are distributed in the hollow space. cavity, as shown in Figure 1. It can be seen from the XRD characterization of Fig. 3 that the cobalt in the material exists in the form of cobalt phosphide.

Example 2

(1) Preparation of metal-organic framework material ZIF-67 containing cobalt ions with dodecahedral morphology: 498 mg of Co(NO ₃ ) ₂ ·6H ₂ O and 700 mg of 2-methylimidazole were dissolved in 50 mL of methanol to obtain a clear purple color solution, after which the solution was mixed well and allowed to stand at room temperature for 24 h. The product was purified by centrifugation (5000rpm, 10min), washed with methanol three times, and dried at 60°C for 12h. Finally, a metal-organic framework material ZIF-67 with a dodecahedron morphology was obtained, and the product mass was 100mg.

(2) Preparation of hollow polymer nanomaterials containing cobalt coordination doping: Weigh 60 mg of ZIF-67 prepared in step (1) and disperse it in 75 mL of methanol. Then, 56.9 mg of dopamine hydrochloride was weighed and dissolved in 15 mL of methanol to prepare a dopamine solution. The ZIF-67 dispersion was mixed with the dopamine solution, and the reaction system was placed at 60°C under reflux for stirring for 12h. The obtained product was processed by centrifugation (5000 rpm, 10 min) and washed three times with methanol until the supernatant was colorless and clarified to obtain a cobalt-containing polymer hollow nanomaterial with a product mass of 25 mg.

(3) Preparation of cobalt oxide/carbon composite hollow nanomaterials: The prepared hollow polymer nanomaterials were carbonized at 700 °C for 2 h under the protection of argon (the heating rate was 5 °C/min), and after cooling to room temperature , the cobalt oxide/carbon composite hollow nanomaterial was obtained, and the product mass was 20 mg.

(4) Preparation of hollow cobalt phosphide/carbon composite hollow nanomaterials: under the protection of argon, put 20 mg of the hollow material obtained in step (3) on one end of the porcelain boat, and put 500 mg of NaH ₂ PO on the other end ₂ · H ₂ O is phosphated at a temperature of 300° C. and a phosphating time of 2 h (heating rate of 3° C./min). After cooling to room temperature, the in-situ doped hollow cobalt phosphide according to the present invention is obtained. Nanoparticles of hollow carbon material with dodecahedral morphology, the product mass is 22 mg.

The prepared hollow cobalt phosphide/carbon composite hollow nanomaterial has a size of about 450-500 nm, and its morphology maintains the dodecahedral shape of the template material ZIF-67, and has a hollow structure at the same time, and the hollow cobalt phosphide particles are distributed in the hollow space. cavity, as shown in Figure 2.

Example 3

(1) Preparation of electrocatalytic working electrode: Dissolve 10 mg of the hollow cobalt phosphide/carbon composite hollow nanomaterial prepared in Example 1 in a mixed solvent of 900 μL methanol and 100 μL, 2wt% perfluorosulfonic acid resin, ultrasonically Treated for 30min to make it into a homogeneous dispersion. Then, 10 μL of dispersion droplets were taken on the glassy carbon electrode and dried at room temperature.

(2) Linear voltammetry test: the voltage range of the linear voltammetry test is 0～-0.6V, the scanning speed is 10mV per second, and the electrolyte used is 0.5M sulfuric acid solution.

(3) Catalytic stability test: First, the cyclic voltammetry scan was performed, the test voltage range was 0-0.6V, the scan speed was 100mV per second, and the number of scan cycles was 1000. Then perform the linear voltammetry scan test in step (2), and compare the results with the results in step (2).

(4) Electrochemical AC impedance test: In the results obtained by the linear voltammetry test, the voltage corresponding to the current density of 10 mA/cm ^-2 is the initial voltage, the high frequency is 10 ⁵ Hz, and the low frequency is 0.1 Hz.

The performance results of catalytic water electrolysis for hydrogen production are shown in Figure 4. The hollow cobalt phosphide/carbon composite hollow material has an overpotential of only 119mV at a current density of 10mA/cm ^-2 , and can still maintain a good catalytic performance after 1000 cycles active. The current density only decayed to 90% of the original value after the voltage was continuously applied for 12 h. The above results indicate that the material has excellent catalytic activity, high stability and long cycle life.

references

[1] Pan, Y.; Sun, K.; Liu, S.; Cao, X.; Wu, K.; Cheong, W-C.; Chen, Z.; Wang, Y.; Li, Y.; Liu, Y.; Wang, D.; Peng, Q.; Chen, C.; Li, Y.J.Am.Chem.Soc.2018,140,2610-2618.

Claims (3)

1. A method for preparing a hollow carbon material with a dodecahedron shape by in-situ doping hollow cobalt phosphide nanoparticles comprises the following steps:

(1) preparing a cobalt ion-containing metal organic framework material ZIF-67 with a dodecahedron morphology: mixing 200-1000 mg Co (NO)₃)₂·6H₂Dissolving O and 500-3000 mg of 2-methylimidazole in 25-100 mL of methanol respectively to obtain a clear solution, then uniformly mixing the two solutions to obtain a purple solution, and standing at room temperature for 6-24 hours; then centrifuging the reaction product, washing the reaction product for 3-5 times by using methanol, and drying the reaction product for 10-15 hours at the temperature of 40-60 ℃ to obtain a metal organic framework material ZIF-67 containing cobalt ions and having a dodecahedron shape;

(2) preparing a hollow polymer nano material containing cobalt coordination doping: weighing 40-60 mg of ZIF-67 prepared in the step (1), and dispersing the ZIF-67 in 50-75 mL of methanol to obtain a ZIF-67 dispersion liquid; then taking 10-15 mL of 20mM dopamine hydrochloride methanol solution, mixing the obtained ZIF-67 dispersion liquid with the dopamine hydrochloride methanol solution, placing the reaction system at 40-60 ℃, refluxing and stirring for 6-12 hours, centrifuging the obtained product, and washing for 3-5 times by using methanol until the supernatant is colorless and clear; removing the supernatant, and retaining the solid product, thereby obtaining the hollow polymer nano material containing the coordination doping of cobalt;

(3) preparing a cobalt oxide/carbon composite hollow nano material: carbonizing the hollow polymer nano material containing the cobalt coordination doping prepared in the step (2) at 700-800 ℃ for 2-4 h under the protection of argon, and cooling to room temperature to obtain a cobalt oxide/carbon composite hollow nano material;

(4) preparing a hollow cobalt phosphide/carbon composite hollow nano material: under the protection of argon, the cobalt oxide/carbon composite hollow obtained in the step (3)The nano material is phosphorized, and the phosphorus source is NaH₂PO₂·H₂And O, the phosphorization temperature is 300-400 ℃, the phosphorization time is 1-3 h, and the hollow cobalt phosphide/carbon composite hollow carbon material with the dodecahedron morphology, which is doped with hollow cobalt phosphide nanoparticles in situ, is obtained after cooling to room temperature.

2. A hollow carbon material with dodecahedron morphology and in-situ doped hollow cobalt phosphide nanoparticles is characterized in that: is prepared by the method of claim 1.

3. The use of the hollow carbon material with dodecahedron morphology of in-situ doped hollow cobalt phosphide nanoparticles as claimed in claim 2 in the production of hydrogen by catalytic electrolysis of water.

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