CN111346652A

CN111346652A - Fluorine-doped spinel structure cobaltosic oxide electrocatalytic material and preparation method thereof

Info

Publication number: CN111346652A
Application number: CN202010295357.2A
Authority: CN
Inventors: 马吉伟; 曾辉炎; 黄云辉
Original assignee: Tongji University
Current assignee: Tongji University
Priority date: 2020-04-15
Filing date: 2020-04-15
Publication date: 2020-06-30

Abstract

The invention provides a fluorine-doped spinel structure cobaltosic oxide electrocatalytic material and a preparation method thereof, belonging to the field of inorganic materials. The structural formula of the fluorine-doped spinel-structured cobaltosic oxide electrocatalytic material provided by the invention is Co₃O_4‑xF_xWherein, 0<x<0.15, the preparation method is as follows: co to have oxygen defects₃O_4‑xAnd XeF₂Placing the mixture into a high-pressure reaction kettle, sealing the reaction kettle, and then reacting the mixture for 10 to 14 hours at the temperature of between 80 and 100 ℃ to obtain Co₃O_4‑xF_x. The invention provides a materialThe material combines the advantages of defect chemistry and fluorine chemistry, and adopts a method of substituting oxygen vacancy by F, so that the doping efficiency of F is improved, the electronic structure of the catalyst is improved, and the cobalt-based oxide has higher OER electrocatalytic activity under the alkaline condition. In addition, the preparation method provided by the invention is simple and efficient, has mild reaction conditions, and meets the requirements of large-scale production.

Description

Fluorine-doped spinel structure cobaltosic oxide electrocatalytic material and preparation method thereof

Technical Field

The invention relates to the field of inorganic materials, in particular to a fluorine-doped spinel structure cobaltosic oxide electrocatalytic material and a preparation method thereof.

Background

Electrocatalytic decomposition of water is a sustainable development strategy that provides efficient clean energy through Oxygen Evolution Reactions (OERs) and Hydrogen Evolution Reactions (HERs). Theoretically, OER is a reaction with thermodynamic energy rise and is accompanied by a process of gradual four-electron transfer at high overpotential, but the reaction kinetics is very slow, which is also a key bottleneck limiting the large-scale industrialization development of electrolyzed water. Ru-based and Ir-based compounds are currently the most effective OER electrolytic water catalysts, but their high cost and scarcity greatly limit large-scale commercial applications. Therefore, it remains a great challenge to develop efficient catalysts that can substantially reduce the overpotential of the OER electrocatalytic reaction.

The transition metal (hydrogen) oxide has abundant reserves, low price and higher activity of electrocatalytic decomposition water Oxygen Evolution (OER) under alkaline conditions, and is widely concerned by researchers. Co₃O₄With Co₄O₄Cubane units and Co^3+/4+And thus exhibits higher OER electrocatalytic activity. In Co₃O₄In, Co³⁺And Co²⁺The relative content of (A) is that of Co₃O₄A key element of the electrocatalytic activity of OER, Co in tetrahedral voids²⁺The sites favor the formation of cobalt oxyhydroxide (CoOOH), which is the active site for the oxidation reaction of water. And oxygen vacancies can significantly affect the OER electrocatalytic properties of Co-based oxide catalyst materials, such as NaBH₄The oxygen vacancy can be effectively constructed by methods such as treatment and plasma etching.

In addition, F-doped oxides have been investigated in various energy conversion and storage devices, F^-Having a strong polarity, F^-Doping can change the electronic structure of the catalyst material so as to improve the intrinsic conductivity; and the mechanical adsorption force between hydroxide and a matrix can be enhanced, so that the electrochemical performance of the compound is effectively improved.

Disclosure of Invention

The present invention has been made to solve the above problems, and an object of the present invention is to provide a fluorine-doped spinel-structured cobaltosic oxide electrocatalytic material prepared by a simple method of partial regular fluorination in an atmosphere, and a method for preparing the same.

The invention provides a fluorine-doped spinel structure cobaltosic oxide electrocatalytic material, which has the characteristics that the structural formula is as follows: co₃O_4-xF_xWherein, 0<x<0.15。

The invention also provides a preparation method of the fluorine-doped spinel structure cobaltosic oxide electrocatalytic material, which is characterized by comprising the following steps of: co to have oxygen defects₃O_4-xAnd XeF₂Placing the mixture into a high-pressure reaction kettle, sealing the reaction kettle, and then reacting the mixture for 10 to 14 hours at the temperature of between 80 and 100 ℃ to obtain Co₃O_4-xF_x。

The preparation method of the fluorine-doped spinel structure cobaltosic oxide electrocatalytic material provided by the invention can also have the following characteristics: wherein the Co having oxygen defects₃O_4-xThe preparation method comprises the following steps: step 1, dissolving an amphiphilic triblock copolymer in a mixed solution of concentrated hydrochloric acid/water under a heating condition, adding tetraethoxysilane, stirring for 12-36 h, reacting for 12-36 h at 90-110 ℃ in a high-pressure reaction kettle, performing suction filtration, taking a solid, washing, and calcining for 4-6 h at 500-600 ℃ to obtain an intermediate; step 2, dipping the intermediate in an ethanol solution of cobalt nitrate hexahydrate, removing the solvent, calcining for 5-8 h at 180-220 ℃, dipping in the ethanol solution of cobalt nitrate hexahydrate again, removing the solvent, calcining for 5-8 h at 400-500 ℃, soaking in alkali liquor for 12-36 h, filtering and drying to obtain Co with oxygen defects₃O_4-x。

The preparation method of the fluorine-doped spinel structure cobaltosic oxide electrocatalytic material provided by the invention can also have the following characteristics: wherein the amphiphilic triblock polymer is EO₂₀–PO₇₀–EO₂₀(molecular weight 5800, Aldrich).

The preparation method of the fluorine-doped spinel structure cobaltosic oxide electrocatalytic material provided by the invention can also have the following characteristics: wherein the heating condition is heating to 35-40 ℃.

The preparation method of the fluorine-doped spinel structure cobaltosic oxide electrocatalytic material provided by the invention can also have the following characteristics: wherein, the calcination in the step 2 is carried out in an air atmosphere.

The preparation method of the fluorine-doped spinel structure cobaltosic oxide electrocatalytic material provided by the invention can also have the following characteristics: wherein the temperature rise rate of the calcination in the step 2 is 1 ℃ min^-1-3℃·min^-1。

The preparation method of the fluorine-doped spinel structure cobaltosic oxide electrocatalytic material provided by the invention can also have the following characteristics: wherein the alkali liquor is NaOH aqueous solution with the concentration of 1-3 mol/L.

The preparation method of the fluorine-doped spinel structure cobaltosic oxide electrocatalytic material provided by the invention can also have the following characteristics: wherein the concentration of the ethanol solution of the cobalt nitrate hexahydrate is 0.1g/mL-0.15 g/mL.

The preparation method of the fluorine-doped spinel structure cobaltosic oxide electrocatalytic material provided by the invention can also have the following characteristics: wherein, Co₃O_4-xAnd XeF₂The feeding mass ratio is 100: (0.35-5.25).

Action and Effect of the invention

According to the fluorine-doped spinel structure cobaltosic oxide electrocatalytic material, the specific surface area is large, so that the electrochemical activity area between the catalyst and the electrolyte in the reaction process is increased, more OER active sites are provided, and the OER electrocatalytic activity of the catalyst is improved.

According to the fluorine-doped cobaltosic oxide electrocatalytic material with the spinel structure, due to the combination of the advantages of defect chemistry and fluorine chemistry, the doping efficiency of F is effectively improved by adopting a method of substituting oxygen vacancies with F, the electronic structure of the catalyst is improved, and cobalt-based oxide has higher OER electrocatalytic activity under alkaline conditions, so that the cobalt-based oxide has wide application prospect.

According to the preparation method of the fluorine-doped spinel structure cobaltosic oxide electrocatalytic material, the preparation method is simple and efficient, and the reaction conditions are mild, so that the preparation method meets the requirements of large-scale production, and can be widely applied to the field of electrocatalytic oxygen precipitation.

Drawings

FIG. 1 shows example 1Co of the present invention₃O_3.87F_0.13And comparative example 1Co₃O_3.87□_0.13An X-ray diffraction (XRD) refinement pattern of the sample;

FIG. 2 shows Co of example 1 of the present invention₃O_3.87F_0.13A schematic of the crystal structure of the sample;

FIG. 3 shows Co of example 1 of the present invention₃O_3.87F_0.13And comparative example 1Co₃O_3.87□_0.13 Co 2p X ray photoelectron spectroscopy (XPS) of the sample;

FIG. 4 shows Co of example 1 of the present invention₃O_3.87F_0.13And comparative example 1Co₃O_3.87□_0.13O1s X-ray photoelectron spectroscopy (XPS) of the sample;

FIG. 5 shows Co of example 1 of the present invention₃O_3.87F_0.13F1s X-ray photoelectron spectroscopy (XPS) of the sample;

FIG. 6 shows Co of example 1 of the present invention₃O_3.87F_0.13Scanning electron microscope X-ray energy spectrum elemental distribution (SEM-EDX);

FIG. 7 shows Co of example 1 of the present invention₃O_3.87F_0.13A Scanning Electron Microscope (SEM) image of the sample;

FIG. 8 shows Co of example 1 of the present invention₃O_3.87F_0.13A Transmission Electron Microscope (TEM) image of the sample;

FIG. 9 shows example 1Co of the present invention₃O_3.87F_0.13N of the sample₂Adsorption-desorption curves and pore size distribution curves;

FIG. 10 is a drawing of the present inventionExample 1Co₃O_3.87F_0.13Cyclic voltammetry test plots (CVs) of samples prepared in comparative examples 1 and 2;

FIG. 11 shows Co of example 1 of the present invention₃O_3.87F_0.13Linear sweep voltammetric polarization profiles (LSV) of the samples prepared in comparative examples 1 and 2;

FIG. 12 shows Co of example 1 of the present invention₃O_3.87F_0.13Tafel curves of samples prepared in comparative example 1 and comparative example 2;

FIG. 13 shows example 1Co of the present invention₃O_3.87F_0.13Comparison of conversion efficiency (TOF) with samples prepared in comparative examples 1 and 2;

FIG. 14 shows example 1Co of the present invention₃O_3.87F_0.13Apparent electrochemical activation energy (E) of the samples prepared in comparative examples 1 and 2_a) Compare the figures.

Detailed Description

In order to make the technical means, the creation features, the achievement purposes and the effects of the invention easy to understand, the invention is specifically described below by combining the embodiment and the attached drawings.

< example 1>

A fluorine-doped spinel structure cobaltosic oxide electrocatalytic material is prepared by the following steps:

step 1, 10g of amphiphilic triblock polymer P123 (EO)₂₀–PO₇₀–EO₂₀5800, Aldrich (Aldrich)) was added to a mixture of 50mL concentrated HCI (37 wt%) and 325mL deionized water, dissolved by magnetic stirring in an oil bath at 38 ℃ until the solution became white, and then 20.8g of Tetraethylorthosilicate (TEOS) was added and magnetic stirring was continued for 24h to give a milky white mixture; pouring the milky white mixed solution into a lining of a 50mL high-pressure reaction kettle, and carrying out solvothermal reaction for 24h at 100 ℃; filtering and washing the solvent thermal reaction product for 3 times by using water and ethanol to obtain a white sample; finally, calcining the white sample in a muffle furnace at 550 ℃ for 5h at the heating rate of 2 ℃ min^-1Obtaining SBA-15;

step 2, 1.1642g of cobalt nitrate hexahydrate [ Co (NO)₃)₂·6H₂O]Dissolving in 10mL ethanol, adding 0.5g SBA-15, magnetically stirring at room temperature for 1h to form a uniformly dispersed solution, evaporating ethanol at 50 deg.C, calcining the dried composite at 200 deg.C in a muffle furnace for 6h at a heating rate of 2 deg.C/min^-1Decomposing the nitrate; then, carrying out a second impregnation process under the same experimental conditions, evaporating ethanol, and calcining in a muffle furnace at 450 ℃ in the air atmosphere for 6 hours to change the composite powder from pink to grey-black; 2mol of L are subsequently added^-1The NaOH aqueous solution is magnetically stirred and dipped for 24 hours to remove SiO₂A template; finally, carrying out suction filtration and water washing for 3 times by using deionized water, and drying for 24 hours at 50 ℃ to obtain a sample Co₃O_3.87□_0.13(□ means an atom vacancy in the present invention, the same applies hereinafter);

step 3, weighing 100mg Co₃O_3.87□_0.13The sample is placed in CeF₄In a pre-fluorinated nickel crucible; then weigh 5.2mg XeF₂(15% excess) was added to the 25mL autoclave liner; and will be provided with Co₃O_3.87□_0.13The nickel crucible is placed in the inner liner of a reaction kettle, the high-pressure reaction kettle is sealed, and the steps are carried out in an argon glove box; taking the high-pressure reaction kettle out of the argon glove box, putting the high-pressure reaction kettle into an oven to react for 12 hours at 90 ℃ to obtain a powder sample Co₃O_3.87F_0.13。

Co obtained in this example₃O_3.87F_0.13And comparative example 1Co₃O_3.87□_0.13The crystallographic data of (a) are shown in table 1.

TABLE 1Co₃O_3.87F_0.13And Co₃O_3.87□_0.13Crystallographic data of

FIG. 1 shows example 1Co of the present invention₃O_3.87F_0.13And comparative example 1Co₃O_3.87□_0.13X-ray diffraction (XRD) refinement pattern of the sample. FIG. 2 is a drawing of the present inventionExample 1Co₃O_3.87F_0.13Schematic of the crystal structure of the sample.

As shown in fig. 1, the experimental results of the present example 1 and the comparative example 1 are better matched with the calculation results. Wherein F occupies the original O atom position instead of the oxygen vacancy, and the detailed unit cell parameters, reliability factors, atom position, thermal displacement parameters and occupancy are shown in Table 1, and Co₃O_3.87F_0.13And Co₃O_3.87□_0.13All diffraction peaks of the sample showed a spinel structure with a space group Fd-3 m.

FIG. 3 shows Co of example 1 of the present invention₃O_3.87F_0.13And comparative example 1Co₃O_3.87□_0.13 Co 2p X radiation photoelectron spectroscopy (XPS) of the sample. FIG. 4 shows Co of example 1 of the present invention₃O_3.87F_0.13And comparative example 1Co₃O_3.87□_0.13O1s X-ray photoelectron spectroscopy (XPS) of the sample. FIG. 5 shows Co of example 1 of the present invention₃O_3.87F_0.13F1s X-ray photoelectron spectroscopy (XPS) of the sample.

The test results of example 1 and comparative example 1 are shown in fig. 3, fig. 4, fig. 5, and table 2.

TABLE 2 Co₃O_3.87F_0.13And Co₃O_3.87□_0.13XPS spectrum data of

As shown in FIG. 3 and Table 2, example 1Co₃O_3.87F_0.13And comparative example 1Co₃O_3.87□_0.13Co of sample²⁺All higher than the sample of comparative example 2 (Co)₃O₄Middle Co²⁺/Co³⁺0.5). Example Co, as shown in FIG. 4₃O_3.87F_0.13And comparative example Co₃O_3.87□_0.13Oxygen vacancies exist in the sample. As shown in FIG. 5, this example provides Co₃O_3.87F_0.13Presence of F in the sample^-。

FIG. 6 shows Co of example 1 of the present invention₃O_3.87F_0.13Scanning electron microscope X-ray energy spectrum elemental profile (SEM-EDX).

As shown in FIG. 6, this example provides Co₃O_3.87F_0.13Co, O and F elements in the sample are uniformly distributed.

FIG. 7 shows Co of example 1 of the present invention₃O_3.87F_0.13Scanning Electron Microscope (SEM) images of the samples. FIG. 8 shows Co of example 1 of the present invention₃O_3.87F_0.13Transmission Electron Microscopy (TEM) images of the samples. FIG. 9 shows example 1Co of the present invention₃O_3.87F_0.13N of the sample₂Adsorption and desorption curves and pore size distribution curves.

As shown in FIGS. 7 to 9, this example provides Co₃O_3.87F_0.13The sample has larger surface area and mesoporous structure, and shows a rod-shaped three-dimensional mesoporous hierarchical structure.

< comparative example 1>

Co₃O_3.87□_0.13The preparation method comprises the following steps:

step 1, 10g of amphiphilic triblock polymer P123 (EO)₂₀–PO₇₀–EO₂₀5800, Aldrich (Aldrich)) was added to a mixture of 50mL concentrated HCI (37 wt%) and 325mL deionized water and dissolved by magnetic stirring in a 38 ℃ oil bath until the solution turned white; then 20.8g of Tetraethoxysilane (TEOS) is added to continue to carry out magnetic stirring for 24 hours to obtain a milky mixed solution; pouring the milky white mixed solution into a lining of a 50mL high-pressure reaction kettle, and carrying out solvothermal reaction for 24h at 100 ℃; then, carrying out suction filtration and washing on the solvent thermal reaction product for 3 times by using water and ethanol to obtain a white sample; finally, calcining the white sample in a muffle furnace at 550 ℃ for 5h at the heating rate of 2 ℃ for min^-1Obtaining SBA-15;

step 2, 1.1642g of cobalt nitrate hexahydrate [ Co (NO)₃)₂·6H₂O]Dissolved in 10mL of ethanol and 0.5g of SBA-15 was added and stirred magnetically at room temperature for 1h to form a well-dispersed solution, after which the ethanol was evaporated at 50 ℃. However, the device is not suitable for use in a kitchenThen calcining the dried compound in a muffle furnace at 200 ℃ for 6h, wherein the heating rate is 2 ℃ for min^-1The nitrate is decomposed. Following a second impregnation procedure under the same experimental conditions, the composite powder changed from pink to grey-black by calcining in a muffle furnace at 450 ℃ in an air atmosphere for 6 h. 2mol of L are subsequently added^-1The NaOH aqueous solution is magnetically stirred and dipped for 24 hours to remove SiO₂A template; finally, carrying out suction filtration and water washing for 3 times by using deionized water, and drying for 24 hours at 50 ℃ to obtain a sample Co₃O_3.87□_0.13。

< comparative example 2>

Cobaltosic oxide (Co)₃O₄) From Aladdin (Aladdin).

< test example 1>

Electrochemical performance test

The samples obtained in example 1 and comparative examples 1 to 2 were subjected to electrochemical performance tests as follows:

and (3) carrying out ultrasonic treatment on the mixed slurry for 10min by using an ultrasonic cell crusher, uniformly carrying out ultrasonic treatment, then dropwise coating 3 mu L of the slurry on the surface of a glassy carbon electrode, and representing the electrocatalytic performance of the sample by using a rotary disc electrode and an electrochemical workstation. In this test example, a mixed slurry was prepared by mixing 5mg of sample, 750. mu.L of deionized water, 250. mu.L of isopropyl alcohol, and 60. mu.L of Nafion solution (5 wt%), using a glassy carbon electrode (GC) of 5mm diameter, and a sample loading of 0.072mg cm^-2。

FIG. 10 shows example 1Co of the present invention₃O_3.87F_0.13Cyclic voltammetry test patterns (CV) of the samples prepared in comparative examples 1 and 2. FIG. 11 shows Co of example 1 of the present invention₃O_3.87F_0.13Linear sweep voltammetric polarization profiles (LSV) of the samples prepared in comparative examples 1 and 2. FIG. 12 shows Co of example 1 of the present invention₃O_3.87F_0.13Tafel curves of samples prepared in comparative example 1 and comparative example 2. FIG. 13 shows example 1Co of the present invention₃O_3.87F_0.13Graph comparing the conversion efficiency (TOF) of the samples prepared in comparative examples 1 and 2.

As shown in FIGS. 10-13, Co₃O_3.87F_0.13The sample was oxidized at a lower potential to generate active sites, with lower OER overpotential, smaller Tafel slope, and larger TOF than comparative example 1 and comparative example 2, thus exhibiting better OER electrocatalytic performance.

As shown in FIG. 14, Co₃O_3.87F_0.13The sample had the lowest activation energy, indicating that it had a reduced binding energy of the intermediate product during the OER reaction.

Effects and effects of the embodiments

According to the fluorine-doped spinel-structured cobaltosic oxide electrocatalytic material, the advantages of defect chemistry and fluorine chemistry are combined, and the doping efficiency of F is effectively improved by adopting a method of substituting oxygen vacancies with F, so that the sample provided by the embodiment 1 improves the electronic structure of the catalyst, and the cobalt-based oxide has high OER electrocatalytic activity under an alkaline condition, and has a wide application prospect.

According to the preparation method of the fluorine-doped spinel-structured cobaltosic oxide electrocatalytic material, which is disclosed by the embodiment 1, the preparation method is simple and efficient, and the reaction conditions are mild, so that the preparation method disclosed by the embodiment 1 meets the requirements of large-scale production, and can be widely applied to the field of electrocatalytic oxygen precipitation.

The above embodiments are preferred examples of the present invention, and are not intended to limit the scope of the present invention.

Claims

1. A fluorine-doped spinel structure cobaltosic oxide electrocatalytic material is characterized by having a structural formula as follows:

Co₃O_4-xF_x，

wherein 0< x < 0.15.

2. A method for preparing a fluorine-doped spinel-structured cobaltosic oxide electrocatalytic material, which is used for preparing the fluorine-doped spinel-structured cobaltosic oxide electrocatalytic material as described in claim 1, and is characterized by comprising the following steps of:

co to have oxygen defects₃O_4-xAnd XeF₂Placing the mixture into a high-pressure reaction kettle, sealing the reaction kettle, and then reacting the mixture for 10 to 14 hours at the temperature of between 80 and 100 ℃ to obtain Co₃O_4-xF_x。

3. The method for preparing a fluorine-doped spinel-structured cobaltosic oxide electrocatalytic material as set forth in claim 2, wherein:

wherein the Co having oxygen defects₃O_4-xThe preparation method comprises the following steps:

step 1, dissolving an amphiphilic triblock copolymer in a mixed solution of concentrated hydrochloric acid/water under a heating condition, adding tetraethoxysilane, stirring for 12-36 h, reacting for 12-36 h at 90-110 ℃ in a high-pressure reaction kettle, performing suction filtration, taking a solid, washing, and calcining for 4-6 h at 500-600 ℃ to obtain an intermediate;

step 2, dipping the intermediate in an ethanol solution of cobalt nitrate hexahydrate, removing the solvent, calcining for 5-8 h at 180-220 ℃, dipping in the ethanol solution of cobalt nitrate hexahydrate again, removing the solvent, calcining for 5-8 h at 400-500 ℃, soaking in alkali liquor for 12-36 h, filtering and drying to obtain Co with oxygen defects₃O_4-x。

4. The method for preparing a fluorine-doped spinel-structured cobaltosic oxide electrocatalytic material as set forth in claim 3, wherein:

wherein the amphiphilic triblock polymer is EO₂₀–PO₇₀–EO₂₀。

5. The method for preparing a fluorine-doped spinel-structured cobaltosic oxide electrocatalytic material as set forth in claim 3, wherein:

wherein the heating condition is heating to 35-40 ℃.

6. The method for preparing a fluorine-doped spinel-structured cobaltosic oxide electrocatalytic material as set forth in claim 3,

wherein, the calcination in the step 2 is carried out in an air atmosphere.

7. The method for preparing a fluorine-doped spinel-structured cobaltosic oxide electrocatalytic material as set forth in claim 3,

wherein the temperature rise rate of the calcination in the step 2 is 1 ℃ for min^-1-3℃min^-1。

8. The method for preparing a fluorine-doped spinel-structured cobaltosic oxide electrocatalytic material as set forth in claim 3,

wherein the alkali liquor is NaOH aqueous solution with the concentration of 1-3 mol/L.

9. The method for preparing a fluorine-doped spinel-structured cobaltosic oxide electrocatalytic material as set forth in claim 3,

wherein the concentration of the ethanol solution of the cobalt nitrate hexahydrate is 0.1g/mL-0.15 g/mL.

10. The method for preparing a fluorine-doped spinel-structured cobaltosic oxide electrocatalytic material as set forth in claim 2, wherein the step of forming the oxide layer on the substrate,

wherein, Co₃O_4-xAnd XeF₂The feeding mass ratio is 100: (0.35-5.2).