阅读说明：本技术 一种四氧化三钴催化剂及其制备方法和应用 (Cobaltosic oxide catalyst, preparation method and application thereof ) 是由 李星运 于强 赵修松 于 2019-09-24 设计创作，主要内容包括：本发明公开了一种四氧化三钴催化剂及其制备方法和应用,制备方法包括：(a)制备暴露晶面为(110)的四氧化三钴纳米棒Co<Sub>3</Sub>O<Sub>4</Sub>-110；(b)将N原子掺杂于Co<Sub>3</Sub>O<Sub>4</Sub>-110的表面,得到四氧化三钴催化剂N-Co<Sub>3</Sub>O<Sub>4</Sub>-110。本发明的四氧化三钴催化剂的制备方法,反应条件易控,常温下即可操作,通过改变氮气等离子体处理时间,可得到不同氮掺杂量和氧空位含量。本发明的制备方法得到的四氧化三钴催化剂,其原料简单易得,且成本较铂、钯等更低,方法操作简单适于工业应用。四氧化三钴催化剂具有更多的表面缺陷、更大的表面氧含量、更大的电荷转移效率、可以用于催化多种氧化反应。(The invention discloses a cobaltosic oxide catalyst and a preparation method and application thereof, wherein the preparation method comprises the following steps: (a) preparing cobaltosic oxide nanorod Co with exposed crystal face of (110) 3 O 4 -110; (b) doping N atoms into Co 3 O 4 Surface of-110 to obtain tricobalt tetroxide catalyst N-Co 3 O 4 -110. The preparation method of the cobaltosic oxide catalyst has the advantages that the reaction conditions are easy to control, the catalyst can be operated at normal temperature, and different nitrogen doping amounts and oxygen vacancy contents can be obtained by changing the treatment time of the nitrogen plasma. The cobaltosic oxide catalyst prepared by the preparation method has the advantages of simple and easily obtained raw materials and lower cost than platinum, palladium and the likeThe method is simple to operate and suitable for industrial application. The cobaltosic oxide catalyst has more surface defects, larger surface oxygen content and larger charge transfer efficiency, and can be used for catalyzing various oxidation reactions.)

1. A method of preparing a tricobalt tetroxide catalyst, the method comprising:

(a) preparing cobaltosic oxide nanorod Co with exposed crystal face of (110)₃O₄-110；

(b) Doping N atoms into the cobaltosic oxide nanorod Co₃O₄Surface of-110 to obtain tricobalt tetroxide catalyst N-Co₃O₄-110。

2. The method of preparing a tricobalt tetroxide catalyst as claimed in claim 1,

the step (a) includes:

(1) mixing ammonia water and polyalcohol solution, and adding Na₂CO₃Uniformly mixing the solution to obtain a mixed solution;

(2) adding Co (NO) into the mixed solution₃)₂·6H₂Mixing the O solution uniformly to obtain sol;

(3) placing the sol into a hydrothermal high-pressure autoclave, and placing the hydrothermal high-pressure autoclave into a drying box to be heated;

(4) washing and drying the product obtained in the step (3);

(5) calcining the product obtained in the step (4) in a muffle furnace to obtain a cobaltosic oxide nanorod Co with an exposed crystal face of (110)₃O₄-110。

3. The method of preparing a tricobalt tetroxide catalyst as set forth in claim 2,

in the step (1), the polyalcohol solution is obtained by uniformly mixing ethylene glycol and deionized water according to the volume ratio of 1: 1;

the ammonia water, the polyhydric alcohol solution and the Na₂CO₃The volume ratio of the solution is (1-3): (4-6): (0.1-0.5);

the Na is₂CO₃The concentration of the solution is 0.5-2mol L^-1。

4. The method of preparing a tricobalt tetroxide catalyst as set forth in claim 3,

in the step (2), the Co (NO)₃)₂·6H₂The concentration of the O solution is 0.5-2mol L^-1Said Co (NO)₃)₂·6H₂The volume ratio of the O solution to the mixed solution is (0.5-1.5): (6-9).

5. The method of preparing a tricobalt tetroxide catalyst as set forth in claim 2,

in the step (3), the temperature of the hydrothermal autoclave is raised to 160-180 ℃, and is maintained for 17-30 h.

6. The method of preparing a tricobalt tetroxide catalyst as set forth in claim 2,

in the step (4), the product is washed by deionized water and then dried for 8-20h at 50-80 ℃;

in the step (5), the calcination temperature is 200-600 ℃, and the calcination time is 2-5 h.

7. The method of preparing a tricobalt tetroxide catalyst as claimed in claim 1,

the step (b) comprises: the cobaltosic oxide nano rod Co obtained in the step (a) is used₃O₄Placing the cobaltosic oxide nanorod Co in a plasma cleaning instrument, vacuumizing, and carrying out treatment on the cobaltosic oxide nanorod Co₃O₄110, performing nitrogen plasma treatment to obtain cobaltosic oxide catalyst N-Co₃O₄-110。

8. The method of preparing a tricobalt tetroxide catalyst as claimed in claim 7,

in the step (b), the power of the plasma cleaning instrument is 20-40W, and the nitrogen flow is 40-70mLmin^-1The plasma treatment time is 10-30 min.

9. The tricobalt tetroxide catalyst obtained by the preparation method of the tricobalt tetroxide catalyst according to any one of claims 1 to 8, characterized in that the tricobalt tetroxide catalyst is a nanosheet having an exposed crystal face (110) and a surface doped with N atoms.

10. Use of the tricobalt tetroxide catalyst obtained by the process for preparing a tricobalt tetroxide catalyst according to any one of claims 1 to 8 in catalytic combustion of methane.

Technical Field

The invention belongs to the technical field of nano material preparation, and particularly relates to a cobaltosic oxide catalyst, and a preparation method and application thereof.

Background

Natural gas has become an important diversified energy supply to alleviate excessive dependence on oil and coal. Particularly, with the rise of the shale gas revolution, the increasing share of the natural gas which is abundant on the earth is seen in the global energy structure. However, the use of natural gas also raises concerns about methane (CH)₄) As its main component, it is a greenhouse gas whose greenhouse effect is about 25 times that of carbon dioxide (adv. funct. mater. 2019, 29 (8), 1807519). Therefore, the aftertreatment of unconverted methane from power plants, Compressed Natural Gas Vehicles (CNGVs), the chemical industry, etc. has also attracted considerable attention (appl. Cat. B: environ. 2018, 237, 844-. Considering CH₄The direct methane combustion needs to be carried out at extremely high temperature, and the high temperature can oxidize N in the air₂Production of toxic NO_xA contaminant. Therefore, the catalyst is an effective way to assist the low-temperature methane combustion. Currently, Pd-based catalysts exhibit excellent methane oxidation activity due to their excellent C — H bond activation capability (Small 2017, 13 (31), 1700941). Nevertheless, the disadvantages of high cost, susceptibility to deactivation, etc. are their limiting factors and there is a continuing need to explore low cost but highly effective noble metal-donating catalysts.

Nanostructured spinel cobalt oxide (Co)₃O₄) Due to its porous structure, mixed cation valence (+ 2, + 3), abundant active oxygen species, good poison resistance and lower cost, it is an attractive non-noble metal catalyst candidate. The research shows that Co₃O₄The surface oxygen in (1) is the active center for activating the C-H bond. Oxygen vacancies as an important defect structure are critical to promote the mobility and reactivity of active surface oxygen. Wang et al introduced strain and detuning into Co by a method of limited oxidation₃O₄Surface, thereby promoting the catalytic activity of methane combustion (nat. commu. 2015, 6, 7181). By alloying a second metal, such as Ni, Ce, etc., into the lattice, cationic defects and structural changes are created, which can promote redox properties and increase oxygen mobility. Li et al discuss the importance of surface defects, indicating thatCo with high index facets₃O₄The nanoplatelets are more active (J. Am. chem. Soc. 2008, 130, 16136-16137). In spite of the above efforts, there is room for great progress in the improvement of catalytic activity, and the search for structure-performance relationships is more intensive.

Disclosure of Invention

The invention aims to provide a cobaltosic oxide catalyst, a preparation method and application thereof, wherein the preparation method is simple and easy to operate, and the prepared cobaltosic oxide catalyst has more surface defects, higher surface oxygen content and high catalytic activation performance on methane.

To this end, the present invention provides a method for preparing a tricobalt tetroxide catalyst, the method comprising:

(a) preparing cobaltosic oxide nanorod Co with exposed crystal face of (110)₃O₄-110；

(b) Doping N atoms into Co₃O₄Surface of-110 to obtain tricobalt tetroxide catalyst N-Co₃O₄-110。

Preferably, the step (a) includes:

(1) mixing ammonia water and polyalcohol solution, and adding Na₂CO₃Uniformly mixing the solution to obtain a mixed solution;

(2) adding Co (NO) into the mixed solution₃)₂·6H₂Mixing the O solution uniformly to obtain sol;

(3) placing the sol into a hydrothermal high-pressure autoclave, and placing the hydrothermal high-pressure autoclave into a drying box to be heated;

(4) washing and drying the product obtained in the step (3);

(5) calcining the product obtained in the step (4) in a muffle furnace to obtain a cobaltosic oxide nanorod Co with an exposed crystal face of (110)₃O₄-110。

Preferably, in the step (1), the polyol solution is obtained by uniformly mixing ethylene glycol and deionized water according to a volume ratio of 1: 1; the ammonia water, thePolyol solution and Na as described₂CO₃The volume ratio of the solution is (1-3): (4-6): (0.1-0.5); the Na is₂CO₃The concentration of the solution is 0.5-2mol L^-1。

Preferably, in the step (2), the Co (NO) is₃)₂·6H₂The concentration of the O solution is 0.5-2mol L^-1Said Co (NO)₃)₂·6H₂The volume ratio of the O solution to the mixed solution is (0.5-1.5): (6-9).

Preferably, in the step (3), the temperature of the hydrothermal autoclave is raised to 160-180 ℃ and maintained for 17-30 h.

Preferably, in the step (4), the product is dried for 8-20h at 50-80 ℃ after being washed by deionized water; in the step (5), the calcination temperature is 200-600 ℃, and the calcination time is 2-5 h.

Preferably, the step (b) comprises: the cobaltosic oxide nano rod Co obtained in the step (a) is used₃O₄Placing the cobaltosic oxide nanorod Co in a plasma cleaning instrument, vacuumizing, and carrying out treatment on the cobaltosic oxide nanorod Co₃O₄110, performing nitrogen plasma treatment to obtain cobaltosic oxide catalyst N-Co₃O₄-110。

Preferably, in the step (b), the power of the plasma cleaning instrument is 20-40W, and the nitrogen flow rate is 40-70mLmin^-1The plasma treatment time is 10-30 min.

The cobaltosic oxide catalyst obtained by the preparation method of the cobaltosic oxide catalyst is a nanosheet, and the nanosheet has an exposed crystal face (110) and is doped with N atoms on the surface.

The cobaltosic oxide catalyst prepared by the preparation method of the cobaltosic oxide catalyst can be applied to methane catalytic combustion.

Compared with the prior art, the invention has the advantages and positive effects that: the invention provides a cobaltosic oxide catalyst and a preparation method and application thereof, wherein the preparation method comprises the following steps: (a) preparing cobaltosic oxide nanorod Co with exposed crystal face of (110)₃O₄-110; (b) doping N atoms into Co₃O₄Surface of-110 to obtain tricobalt tetroxide catalyst N-Co₃O₄-110。

The preparation method of the cobaltosic oxide catalyst has the advantages that the reaction conditions are easy to control, the catalyst can be operated at normal temperature, and different nitrogen doping amounts and oxygen vacancy contents can be obtained by changing the treatment time of the nitrogen plasma. The cobaltosic oxide catalyst prepared by the preparation method has the advantages of simple and easily obtained raw materials, lower cost than platinum, palladium and the like, simple operation and suitability for industrial application. Firstly, preparing and obtaining cobaltosic oxide nano rod Co with active exposed crystal face of (110)₃ O ₄110, the surface activity of the cobaltosic oxide catalyst can be high; then through N₂The plasmas are subjected to surface treatment, so that N atoms are doped on the surface of the plasmas, and meanwhile, the cobaltosic oxide nano rod can be partially etched to expose a more active outer surface, so that the cobaltosic oxide catalyst generates more surface defects and obtains higher surface oxygen content, and the cobaltosic oxide nano plate rich in oxygen vacancies is obtained and has more active centers; meanwhile, the introduction of N can obviously reduce the active energy barrier of methane, and the excellent catalytic oxidation performance of methane is shown.

Other features and advantages of the present invention will become more apparent from the following detailed description of the invention when taken in conjunction with the accompanying drawings.

Drawings

FIG. 1 shows Co prepared in example 1₃O₄SEM picture of-110;

FIG. 2 shows Co prepared in example 1₃O₄TEM image of-110;

FIG. 3 shows the N-Co prepared in example 2₃O₄SEM picture of-110;

FIG. 4 shows the N-Co prepared in example 2₃O₄-an XPS total spectrum of 110;

FIG. 5 shows Co prepared in examples 1 and 2₃O₄-110 and N-Co₃O₄-an XRD spectrum of 110;

FIG. 6 shows the results of examples 1 and 2Co of (A)₃O₄-110 and N-Co₃O₄-XPSO 1s spectrum of 110;

FIG. 7 shows Co prepared in examples 1 and 2₃O₄-110 and N-Co₃O₄-a BET curve of 110;

FIG. 8 shows Co prepared in examples 1 and 2₃O₄-110 and N-Co₃O₄-110 vs. methane catalytic oxidation conversion diagram.

Detailed Description

The following detailed description of specific embodiments of the present invention is provided to illustrate and explain the present invention and to be understood not to limit the present invention.

The preparation method of the cobaltosic oxide catalyst comprises the following steps:

(a) preparing cobaltosic oxide nanorod Co with exposed crystal face of (110)₃O₄-110；

(b) Doping N atoms into cobaltosic oxide nanorod Co₃O₄Surface of-110 to obtain tricobalt tetroxide catalyst N-Co₃O₄-110。

Specifically, the step (a) comprises the following steps:

(1) mixing ammonia water and polyalcohol solution, and adding Na₂CO₃Uniformly mixing the solution to obtain a mixed solution;

(2) adding Co (NO) into the mixed solution₃)₂·6H₂Mixing the O solution uniformly to obtain sol; the mixed solution contains ammonia water and Na₂CO₃Two alkaline solutions, which can be mixed with Co (NO)₃)₂·6H₂Synthesis of Co (CO) by O reaction₃)_0.5(OH)·_0.11The material is calcined to finally form Co₃O₄。

(3) Placing the sol in a hydrothermal high-pressure autoclave, placing the hydrothermal high-pressure autoclave in a drying box, and heating;

(4) washing and drying the product obtained in the step (3);

(5) will be provided withCalcining the product obtained in the step (4) in a muffle furnace to obtain a cobaltosic oxide nanorod Co with an exposed crystal face of (110)₃O₄-110。

In the step (1), the polyalcohol solution is obtained by uniformly mixing ethylene glycol and deionized water according to the volume ratio of 1: 1. Ammonia, polyol solution and Na₂CO₃The volume ratio of the solution is (1-3): (4-6): (0.1-0.5), Na₂CO₃The concentration of the solution is 0.5-2mol L^-1. By ammonia, polyol solution and Na₂CO₃Volume ratio of solution and Na₂CO₃The concentration of the solution can influence the crystal orientation and the growth speed in the synthesis process, so that the cobaltosic oxide nano rod with different appearances and different exposed crystal faces can be synthesized. In the present invention, aqueous ammonia, a polyhydric alcohol solution and Na₂CO₃The volume ratio of the solution is (1-3): (4-6): (0.1-0.5), Na₂CO₃The concentration of the solution is 0.5-2mol L^-1Obtaining the cobaltosic oxide nanorod Co with the exposed crystal face of (110)₃O₄-110; the surface oxygen content with the exposed crystal face of (110) is the highest, and the cobaltosic oxide nanorod with the exposed crystal face of (110) has larger specific surface area due to the porous and rod-shaped appearance, can expose more catalytic active sites, and is more beneficial to CH₄The molecules are adsorbed and activated on their surface; in addition, the specific atomic arrangement of the (110) crystal face is also beneficial to reducing the energy barrier of catalytic reaction and is more beneficial to catalytic combustion of methane.

In step (2), Co (NO)₃)₂·6H₂Concentration of O solution and Co (NO)₃)₂·6H₂The volume ratio of the O solution to the mixed solution can influence the crystal orientation and the growth speed in the synthesis process, so that the cobaltosic oxide nano rod with different appearances and different exposed crystal faces can be synthesized. In the present invention, Co (NO)₃)₂·6H₂The concentration of the O solution is 0.5-2mol L^-1， Co(NO₃)₂·6H₂The volume ratio of the O solution to the mixed solution is (0.5-1.5): (6-9) can obtain an exposed crystal face of (110) Cobaltosic oxide nanorod Co₃O₄-110; the surface oxygen content with the exposed crystal face of (110) is the highest, and the cobaltosic oxide nanorod with the exposed crystal face of (110) has larger specific surface area due to the porous and rod-shaped appearance, can expose more catalytic active sites, and is more beneficial to CH₄The molecules are adsorbed and activated on their surface; in addition, the specific atomic arrangement of the (110) crystal face is also beneficial to reducing the energy barrier of catalytic reaction and is more beneficial to catalytic combustion of methane.

In the step (3), the hydrothermal autoclave is heated to 160 ℃ and 180 ℃ and maintained for 17-30 h.

In the step (4), the product is washed by deionized water and then dried for 8-20h at 50-80 ℃.

In the step (5), the calcination temperature is 200-600 ℃, and the calcination time is 2-5 h.

Specifically, the step (b) comprises the following steps: the cobaltosic oxide nano rod Co obtained in the step (a)₃O₄Placing the powder-110 in a plasma cleaning instrument, vacuumizing, and carrying out vacuum treatment on the cobaltosic oxide nanorod Co₃O₄110, performing nitrogen plasma treatment to obtain cobaltosic oxide catalyst N-Co₃O₄-110。

In the step (b), the power of the plasma cleaning instrument is 20-40W, and the nitrogen flow is 40-70mLmin^-1The plasma treatment time is 10-30 min.

The cobaltosic oxide catalyst obtained by the preparation method is a nanosheet, has an exposed crystal face (110), is doped with N atoms on the surface, and can be used for catalytic combustion of methane.

The preparation method of the cobaltosic oxide catalyst has the advantages that the reaction conditions are easy to control, the catalyst can be operated at normal temperature, and different nitrogen doping amounts and oxygen vacancy contents can be obtained by changing the treatment time of the nitrogen plasma. The cobaltosic oxide catalyst prepared by the preparation method has the advantages of simple and easily obtained raw materials, lower cost than platinum, palladium and the like, simple operation and suitability for industrial application. Firstly, preparing and obtaining cobaltosic oxide nano rod Co with active exposed crystal face of (110)₃ O ₄110, enabling cobaltosic oxideThe catalyst has high surface activity; then through N₂The plasmas are subjected to surface treatment, so that N atoms are doped on the surface of the plasmas, and meanwhile, the cobaltosic oxide nano rod can be partially etched to expose a more active outer surface, so that the cobaltosic oxide catalyst generates more surface defects and obtains higher surface oxygen content, and the cobaltosic oxide nano plate rich in oxygen vacancies is obtained and has more active centers; meanwhile, the introduction of N can obviously reduce the active energy barrier of methane, and the excellent catalytic oxidation performance of methane is shown.