CN109847753B

CN109847753B - Porous Co @ C nano material and preparation method and application thereof

Info

Publication number: CN109847753B
Application number: CN201910099773.2A
Authority: CN
Inventors: 张金水; 侯乙东; 理解; 安平
Original assignee: Fuzhou University
Current assignee: Fuzhou University
Priority date: 2019-01-31
Filing date: 2019-01-31
Publication date: 2021-08-31
Anticipated expiration: 2039-01-31
Also published as: CN109847753A

Abstract

The invention belongs to the technical field of material preparation and photocatalysis, and particularly relates to a porous Co @ C nano material as well as a preparation method and application thereof. The porous Co @ C nano material is synthesized by a hard template method, and the preparation method is simple and convenient in preparation process, low in cost and easy for large-scale industrial production. Compared with a nano tubular structure which naturally grows in a bulk phase, the surface porous structure of the nano tubular structure greatly promotes the transfer of excited electrons and improves the surface hydrogen production dynamics behavior, thereby obviously improving the photocatalytic hydrogen production performance of a photosensitizer dye-alcohol-water system and having wide application prospect in the aspect of developing sustainable green energy.

Description

Porous Co @ C nano material and preparation method and application thereof

Technical Field

The invention belongs to the technical field of material preparation and photocatalysis. In particular to a porous Co @ C nano material, a preparation method thereof and application thereof in photocatalytic hydrogen production.

Background

With the gradual exhaustion of petrochemical energy, the increasing aggravation of environmental pollution and greenhouse effect, the development of new energy (including solar energy, biomass energy, wind energy and the like) has become a global consensus and is also listed in the energy development strategy of China. The direct conversion from solar energy to hydrogen energy is realized by utilizing the photocatalytic technology to prepare hydrogen, and the method is an ideal way for obtaining new energy. Currently, although many photocatalytic materials have good light absorption properties, the quantum efficiency of photocatalytic hydrogen production systems is low, for the following reasons: the hydrogen evolution kinetics of the light absorber itself is poor. To solve this problem, noble metal hydrogen evolution catalysts have been used in photocatalytic hydrogen production systems to prove to be a very effective approach. However, noble metals are both expensive and rare, necessarily affecting their practical large-scale use. Therefore, it is very important to develop a hydrogen evolution catalyst with low cost and high catalytic activity to replace noble metals for application in a photocatalytic hydrogen production system.

Disclosure of Invention

Aiming at the problems, the invention provides a porous Co @ C nano material, a preparation method and application thereof.

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

a preparation method of a porous Co @ C nano material comprises the following steps:

(1) dissolving a certain amount of cobalt precursor and carbon precursor in water at 80 ℃, stirring for 2h, and then adding SiO₂Template, SiO added₂The mass ratio of the cobalt precursor to the total mass of the carbon precursor is 1-8: 1, continuously heating and stirring for 2 hours; then putting into liquid nitrogen for cooling, freezing and drying; and then calcining in a tube furnace in argon atmosphere for 1 h at 500-550 ℃ in the first stage and 2h at 700-800 ℃ in the second stage to obtain Co @ C and SiO₂Mixing;

the cobalt precursor is CoCl₂·6H₂O、Co(CH₃COO)₂·4H₂O or cobalt phthalocyanine; the carbon precursor is cyanamide, dicyandiamide or melamine;

(2) mixing Co @ C with SiO₂And soaking the mixture in an ammonium bifluoride solution with the concentration of 1-4M for 12-36 h, centrifuging, and drying in a vacuum oven to obtain the Co @ C nano material.

The load amount of Co in the porous Co @ C nano material is 0.7 wt%.

The application of the porous Co @ C nano material as a photocatalyst in photocatalytic hydrogen production is as follows: the photocatalytic hydrogen production is carried out in a photosensitizer dye-alcohol-water system.

The photosensitizer dye comprises: one or more of eosin Y, rhodamine B and methyl orange; the alcohol comprises: one or more of triethanolamine, ethylene glycol, methanol and ethanol.

Compared with the prior art, the invention has the following advantages:

(1) the porous Co @ C nano material is prepared by a hard template method, has a porous structure, increases reactive active sites for hydrogen evolution, promotes the transfer of photogenerated electrons, improves the surface hydrogen production dynamics behavior, and thus obviously improves the performance of a photocatalytic hydrogen production system. Research results show that the activity of the porous Co @ C nano material is obviously higher than that of a nano tubular structure Co @ C naturally grown in a bulk phase.

(2) The method has the advantages of simple process, low raw material price, mild reaction conditions, low production cost, greenness and environmental protection, and is suitable for large-scale production.

Drawings

FIG. 1 is SEM spectra of photocatalysts prepared in example 1 (right) and comparative example 1 (left);

fig. 2 is XRD spectra of the photocatalysts prepared in example 1 and comparative example 1;

FIG. 3 is specific surface area and pore volume distribution data for the photocatalysts prepared in example 1 and comparative example 1;

fig. 4 is a graph showing photocatalytic hydrogen production performance of the photocatalysts prepared in example 1 and comparative example 1.

Detailed Description

In order to make the present invention more comprehensible, the technical solutions of the present invention are further described below with reference to specific embodiments, but the present invention is not limited thereto.

Example 1 (porous Co @ C)

1g of CoCl₂·6H₂O and 2g dicyandiamide are dispersed in deionized water, stirred in an oil bath at 80 ℃ for 2h, and then 12 g SiO are added₂And (4) continuously heating and stirring the template for 2 hours. And then putting the sample into liquid nitrogen for cooling, freezing and drying the sample until the water of the sample is drained. Then calcining the mixture in a tube furnace in argon atmosphere at 500 ℃ for 1 h, 750 ℃ for 2h to obtain Co @ C and SiO₂And (3) mixing. Mixing Co @ C with SiO₂The mixture was soaked in 4M ammonium bifluoride solution for 24 h, centrifuged, and vacuum oven dried to obtain porous Co @ C particles, with Co loading of 0.7 wt%, labeled Co @ CNS.

Example 2 (porous Co @ C)

1g of CoCl₂·6H₂O and 2g dicyandiamide are dispersed in deionized water, stirred in an oil bath at 80 ℃ for 2h, and then 15 g SiO are added₂And (4) continuously heating and stirring the template for 2 hours. And then putting the sample into liquid nitrogen for cooling, freezing and drying the sample until the water of the sample is drained. Then calcining the mixture in a tube furnace in argon atmosphere for 1 h at 550 ℃ in the first stage and 2h at 800 ℃ in the second stage to obtain Co @ C and SiO₂And (3) mixing. Mixing Co @ C with SiO₂The mixture is soaked in an ammonium bifluoride solution with the concentration of 4M for 24 hours, and then the porous Co @ C particles are obtained after centrifugation and drying in a vacuum oven, wherein the load of Co is 0.7 wt%.

Comparative example 1 (bulk Co @ C)

1g of CoCl₂·6H₂O and 2g of dicyandiamide are dispersed in deionized water, stirred in an oil bath at 80 ℃ for 4 h, and no template is added. And then putting the sample into liquid nitrogen for cooling, freezing and drying the sample until the water of the sample is drained. And then, calcining in a tube furnace in an argon atmosphere for 1 h at the calcining temperature of 500 ℃ in the first stage, for 2h at the calcining temperature of 750 ℃ in the second stage to obtain the black tubular phase Co @ C. And soaking the Co @ C in an ammonium bifluoride solution with the concentration of 4M for 24 hours, centrifuging, and drying in a vacuum oven to obtain black tubular phase Co @ C, wherein the load of Co is 1.5 wt%, and the mark is Co @ CNT.

Application example

1 mg of the Co @ C nanomaterial prepared in example 1 and comparative example 1 and 50 mg of eosin Y were added to 100 mL of triethanolamine (10 vol%) aqueous solution, mixed by sonication, poured into a reactor, magnetically stirred at a certain speed to maintain the catalyst in solution in suspension, and the reaction system was maintained at about 5 ℃ by circulating condensed water. After the reactor and the solution were evacuated repeatedly several times, the light source (300W xenon lamp) was turned on to perform the photocatalytic reaction, the amount of hydrogen generated in the system was measured by gas chromatography, the detector was a thermal conductivity detector, and argon was used as a carrier gas.

FIG. 1 is a scanning electron micrograph of bulk Co @ C on the left, which can be clearly seenIn the figure the bulk phase Co @ C is present in the form of nanotubes. FIG. 1 shows the right scanning electron micrograph of the porous Co @ C particles, which are about 30 nm in size. Figure 2 is a ray diffraction pattern of porous and bulk Co @ C X, showing that both have cobalt and carbon of the same crystalline composition. FIG. 3 is data of the specific surface area and pore volume distribution of porous and bulk Co @ C, showing that the specific surface area of porous Co @ C is 257 m² g^-1And bulk Co @ C has a specific surface area of 75 m² g^-1The porous Co @ C has a specific surface area that is more than 3 times that of the bulk Co @ C. FIG. 4 is a graph of the photocatalytic hydrogen production activity of porous and bulk Co @ C samples, with the hydrogen production activity of porous Co @ C being significantly higher than that of bulk Co @ C in 4 cycles: in the 1 st cycle, the photocatalytic hydrogen production performance of the porous Co @ C is more than 3 times that of the bulk Co @ C, and as the bulk Co @ C is more obviously attenuated than the porous Co @ C, the photocatalytic hydrogen production performance of the porous Co @ C is more than 5 times that of the bulk Co @ C by the 4 th cycle.

The above description is only a preferred embodiment of the present invention, and all equivalent changes and modifications made in accordance with the claims of the present invention should be covered by the present invention.

Claims

1. A preparation method of a porous Co @ C nano material is characterized by comprising the following steps: the method comprises the following steps:

(1) dissolving 1g of cobalt precursor and 2g of carbon precursor in water at 80 ℃, stirring for 2h, and then adding SiO₂Template, SiO added₂The mass ratio of the cobalt precursor to the total mass of the carbon precursor is 1-8: 1, continuously heating and stirring for 2 hours; then putting into liquid nitrogen for cooling, freezing and drying; and then calcining in a tube furnace in argon atmosphere for 1 h at 500-550 ℃ in the first stage and 2h at 700-800 ℃ in the second stage to obtain Co @ C and SiO₂Mixing;

(2) mixing Co @ C with SiO₂Soaking the mixture in a fluorinated solution of 1-4MAnd (3) centrifuging the ammonium hydroxide solution for 12-36 hours, and drying the ammonium hydroxide solution in a vacuum oven to obtain the porous Co @ C nano material.

2. The preparation method of the porous Co @ C nanomaterial according to claim 1, characterized in that: the loading amount of Co in the porous Co @ C nano material is 0.7 wt%.

3. A porous Co @ C nanomaterial obtained by the preparation method as claimed in claim 1 or 2.

4. The application of the porous Co @ C nanomaterial as a photocatalyst in photocatalytic hydrogen production is characterized in that: the photocatalytic hydrogen production is carried out in a photosensitizer dye-alcohol-water system; the photosensitizer dye comprises: one or more of eosin Y, rhodamine B and methyl orange; the alcohol comprises: one or more of triethanolamine, ethylene glycol, methanol and ethanol.