CN113113613B - High-electrocatalytic-property superfine cobalt oxide particle/cobalt-nitrogen-carbon thin layer/carbon composite material and preparation method thereof - Google Patents

High-electrocatalytic-property superfine cobalt oxide particle/cobalt-nitrogen-carbon thin layer/carbon composite material and preparation method thereof Download PDF

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CN113113613B
CN113113613B CN202110349198.4A CN202110349198A CN113113613B CN 113113613 B CN113113613 B CN 113113613B CN 202110349198 A CN202110349198 A CN 202110349198A CN 113113613 B CN113113613 B CN 113113613B
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cobalt
carbon
nitrogen
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composite material
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CN113113613A (en
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郭兴梅
万小晗
张俊豪
段梦婷
史静
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Jiangsu University of Science and Technology
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/86—Inert electrodes with catalytic activity, e.g. for fuel cells
    • H01M4/8647—Inert electrodes with catalytic activity, e.g. for fuel cells consisting of more than one material, e.g. consisting of composites
    • H01M4/8657—Inert electrodes with catalytic activity, e.g. for fuel cells consisting of more than one material, e.g. consisting of composites layered
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/86—Inert electrodes with catalytic activity, e.g. for fuel cells
    • H01M4/88—Processes of manufacture
    • H01M4/8878—Treatment steps after deposition of the catalytic active composition or after shaping of the electrode being free-standing body
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/86—Inert electrodes with catalytic activity, e.g. for fuel cells
    • H01M4/90—Selection of catalytic material
    • H01M4/9016—Oxides, hydroxides or oxygenated metallic salts
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/86—Inert electrodes with catalytic activity, e.g. for fuel cells
    • H01M4/90—Selection of catalytic material
    • H01M4/9075—Catalytic material supported on carriers, e.g. powder carriers
    • H01M4/9083—Catalytic material supported on carriers, e.g. powder carriers on carbon or graphite
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Abstract

The invention discloses a high-dispersion ultrafine cobalt oxide particle/cobalt-nitrogen-carbon thin layer/carbon composite material and a preparation method thereof. The composite material is composed of cobalt oxide nanoparticles, a cobalt-nitrogen-carbon thin layer and a mesoporous carbon matrix, wherein the cobalt oxide nanoparticles are uniformly dispersed in the cobalt-nitrogen-carbon thin layer and loaded on the mesoporous carbon matrix. The diameter of the cobalt oxide nano-particles is 2-5nm, and the cobalt oxide nano-particles account for 2-10% of the composite material by mass; the thickness of the cobalt-nitrogen-carbon thin layer is less than 2nm and accounts for 10-20% of the composite material by mass percent. The invention utilizes the coordination dispersion of dicyanodiamine to cobalt ions and the confinement effect of a mesoporous carbon matrix to prepare highly dispersed and small-sized cobalt oxide nanoparticles and a cobalt-nitrogen-carbon thin layer, and the cobalt-nitrogen-carbon thin layer is loaded in the mesoporous carbon matrix and used as an anode electrocatalyst of a metal-air battery, the activity of the cobalt-nitrogen-carbon thin layer is close to that of commercial platinum carbon, and the stability of the cobalt-nitrogen-carbon thin layer is higher than that of the commercial platinum carbon.

Description

High-electrocatalytic-property superfine cobalt oxide particle/cobalt-nitrogen-carbon thin layer/carbon composite material and preparation method thereof
Technical Field
The invention belongs to the technical field of electrocatalytic materials, and particularly relates to a high-dispersion ultrafine cobalt oxide particle/cobalt-nitrogen-carbon thin layer/carbon composite material and a preparation method thereof.
Background
The metal-air battery as an important energy storage and conversion device has the advantages of high energy density, good safety performance, no environmental pollution and the like. However, the oxygen reduction reaction of the anode is slow in reaction kinetics, and a highly efficient and stable electrocatalyst is required. Commercial Pt/C has excellent catalytic activity, but is limited by high price and low stability, and cannot be applied on a large scale. Therefore, the research and development of the cheap, efficient and stable non-noble metal oxygen reduction electrocatalyst has important significance for the development of metal-air batteries.
Cobalt oxides and cobalt-nitrogen-carbon have received increasing attention due to their excellent electrocatalytic activity. However, cobalt oxide has poor conductivity, and the density of active sites of cobalt-nitrogen-carbon is not high, and the cobalt oxide needs to be loaded on a conductive substrate to ensure efficient electron transfer, and meanwhile, the effective contact area with the electrolyte is increased, and the utilization rate of active ingredients is improved. However, during the catalytic process, the oxides and cobalt-nitrogen-carbon are easily detached from the substrate or agglomerated, reducing activity and stability. Therefore, the cobalt oxide is firmly and uniformly dispersed in a fine grain form, and the cobalt-nitrogen-carbon is stably supported in a nano thin layer form, which is the research focus and difficulty of the cobalt oxide and the cobalt-nitrogen-carbon as the electrocatalyst. The size of the cobalt oxide nano-particles reported at present is generally within the range of 20-100 nm, even exceeds 100nm, and is difficult to be below 5 nm; in addition, the cobalt-nitrogen-carbon reported so far is difficult to be supported on a carbon substrate in an integral thin layer form.
Disclosure of Invention
The invention aims to overcome the problems and the defects of the prior art and provide a high-dispersion ultrafine cobalt oxide particle/cobalt-nitrogen-carbon thin layer/carbon composite material and a preparation method thereof aiming at the research difficulty in the field.
In order to achieve the purpose, the technical scheme adopted by the invention is as follows:
a high-dispersity superfine cobalt oxide particle/cobalt-nitrogen-carbon thin layer/carbon composite material is composed of cobalt oxide nanoparticles, a cobalt-nitrogen-carbon thin layer and a mesoporous carbon matrix. The cobalt oxide nanoparticles are uniformly dispersed in the cobalt-nitrogen-carbon thin layer and loaded on the mesoporous carbon matrix. The diameter of the cobalt oxide nano-particles is 2-5nm, the cobalt oxide nano-particles account for 2-10% of the composite material by mass, the thickness of the cobalt-nitrogen-carbon thin layer is less than 2nm, and the cobalt-nitrogen-carbon thin layer accounts for 10-20% of the composite material by mass.
In order to achieve the purpose, the invention adopts another technical scheme as follows:
a preparation method of a high-dispersion ultrafine cobalt oxide particle/cobalt-nitrogen-carbon thin layer/carbon composite material comprises the following steps:
(1) functionalization of mesoporous carbon substrates
Soaking the mesoporous carbon matrix in a strong acid solution, placing the solution in a reaction kettle, preserving heat for 2-6 hours at 100-200 ℃ to oxidize the carbon surface to form a large number of oxygen-containing groups, then naturally cooling, and centrifugally cleaning with water or ethanol to obtain the functionalized mesoporous carbon matrix.
(2) Disperse co-adsorption of cobalt ions and dicyanodiamide on mesoporous carbon
Immersing the functionalized mesoporous carbon matrix into a mixed solution of cobalt salt and dicyanodiamide (DCDA), wherein the molar ratio of the cobalt salt to the DCDA is 1: 10-1: 50; stirring for 0.5-2 h to obtain Co2+Adsorbing the carbon powder and DCDA together on a mesoporous carbon matrix; in the Co-adsorption process, Co2+Under the coordination action of DCDA molecules, high dispersion is kept; and finally, centrifugally cleaning the mixture by using water or ethanol, and drying the mixture at the temperature of 30-80 ℃ for later use.
(3) Calcining to obtain the high-dispersion superfine cobalt oxide particles/cobalt-nitrogen-carbon thin layer/carbon composite material
Will adsorb Co2+Calcining the mesoporous carbon matrix of DCDA in inert atmosphere, and under the confinement effect of mesopores, partially calcining Co2+Together with DCDA, into a thin layer of Co-N-C, a portion of Co2+Aggregation to fine CoO nanoparticles occurs. Thereby obtaining the high-dispersion ultrafine cobalt oxide particles/cobalt-nitrogen-carbon thin layer/carbon (CoO/Co-N-C/C) composite material.
Further preferably, the strong acid solution in the step (1) is 1-2 mol L-1The effect of the nitric acid solution is optimal.
Further preferably, the cobalt salt solution in the step (2) is a cobalt chloride solution, a cobalt nitrate solution or a cobalt sulfate solution.
Further preferably, the concentration of the cobalt salt solution in the step (2) is 1-10 mmol L-1The concentration of the DCDA solution is 0.1-0.5 mol L-1。
Further preferably, Co will be adsorbed in step (3)2+And calcining the DCDA mesoporous carbon matrix material in an inert atmosphere, wherein the calcining process comprises the following steps: heating the mixture from room temperature to 500-650 ℃ at the speed of 0.5-10 ℃/min, preserving the heat for 2-4 h, and naturally cooling.
Further preferably, the inert atmosphere in step (3) is nitrogen or argon atmosphere.
The invention relates to application of a high-dispersion ultrafine cobalt oxide particle/cobalt-nitrogen-carbon thin layer/carbon composite material as an electrocatalyst.
The high-dispersion ultrafine cobalt oxide particles/cobalt-nitrogen-carbon thin layer/carbon composite material is applied to a positive electrode catalyst of a metal-air battery.
Compared with the prior art, the invention has the following advantages and beneficial effects:
through a large amount of exploration and experiments, the invention utilizes DCDA to carry out Co2+The coordination dispersion and the confinement effect of the mesoporous pore canal, and highly dispersed and small-sized cobalt oxide nano particles and a cobalt-nitrogen-carbon thin layer are obtained by adsorption-calcination and are loaded in a mesoporous carbon matrix. The composite material has rich active sites and a stable load structure as an electrocatalyst, the half-wave potential of the electrocatalysis for the oxygen reduction reaction is only 30mV lower than that of a commercial platinum-carbon noble metal electrocatalyst, and the current density after continuous catalysis for 20000s is 86.7 percent of the initial value and is superior to the current retention rate of commercial platinum-carbon (57.5 percent); as a zinc-air cell positive electrode electrocatalyst, an open circuit potential of 1.397V was obtained, second only to commercial platinum-carbon catalyzed zinc-air cells (1.465V); the LED lighted by connecting two zinc-air batteries in series has the advantages that the brightness is maintained for 12h without obvious reduction, and high stability is shown.
Drawings
FIG. 1 is a scanning electron micrograph of mesoporous carbon CMK-3(a) and CoO/Co-N-C/C-550(b) in example 1.
FIG. 2 is an XRD pattern of CoO/Co-N-C/C-550 of example 1.
FIG. 3 shows TEM images (a) of CMK-3 of example 1 and TEM images (b), (C), and (d) of the prepared CoO/Co-N-C/C-550.
FIG. 4 shows XPS survey spectra (a), Co 2p3/2 high resolution spectra (b), C1s high resolution spectra (C), and N1s high resolution spectra (d) of CoO/Co-N-C/C-550 in example 1.
FIG. 5 is a graph of CoO/Co-N-C/C-550 prepared in example 1 and commercial Pt/C in O2Saturated 0.1mol L- 1LSV curve in KOH electrolyte, scan rate 10mV s-1The rotation speed is 1600 rpm.
FIG. 6 is a current-time curve (a) for CoO/Co-N-C/C-550 and commercial Pt/C prepared in example 1 and a current-time test curve with methanol added at 600 s.
FIG. 7 shows the discharge polarization curves and corresponding power density (a), open circuit voltage-time curve (b) at 10mA cm for a zinc-air cell assembled with CoO/Co-N-C/C-550 prepared in example 1 and commercial Pt/C as a positive electrode catalyst-2The constant current discharge curve (C), the specific capacity (d), the discharge curve (e) under different current densities, and two CoO/Co-N-C/C-550 zinc-air batteries connected in series light a light-emitting diode.
FIG. 8 is an XRD pattern of CoO/Co-N-C-500 prepared in example 2.
FIG. 9 shows the CoO/Co-N-C-500 prepared in example 2 and commercial Pt/C in O2LSV curve in saturated 0.1M KOH electrolyte, scan rate 10mV s-1The rotation speed is 1600 rpm.
FIG. 10 is an XRD pattern of CoO/Co-N-C-600 prepared in example 3.
FIG. 11 is a graph of CoO/Co-N-C-600 prepared in example 3 and commercial Pt/C in O2LSV curve in saturated 0.1M KOH electrolyte, scan rate 10mV s-1The rotation speed is 1600 rpm.
FIG. 12 is a CoO prepared in example 4xXRD pattern of/Co-N-C-650.
FIG. 13 is a CoO prepared in example 4xCo-N-C-650 and commercial Pt/C in O2LSV curve in saturated 0.1M KOH electrolyte, scan rate 10mV s-1The rotation speed is 1600 rpm.
FIG. 14 is a SEM image of CoO/C in example 5.
FIG. 15 is the XRD pattern of CoO/C in example 5.
FIG. 16 is the CoO/C and commercial Pt/C in O prepared in example 52Saturated 0.1mol L-1LSV curve in KOH electrolyte, scan rate 10mV s-1The rotation speed is 1600 rpm.
FIG. 17 is an SEM image of N-C/C in example 6.
FIG. 18 is the XRD spectrum of N-C/C in example 6.
FIG. 19 shows an embodimentN-C/C and commercial Pt/C prepared in example 6 in O2LSV curve in saturated 0.1M KOH electrolyte, scan rate 10mV s-1The rotation speed is 1600 rpm.
Detailed Description
For a better understanding of the nature of the invention, its description is given below in conjunction with the accompanying drawings.
Example 1:
the preparation method of the CoO/Co-N-C/C-550 composite material comprises the following steps:
(1) functionalization treatment of the mesoporous carbon substrate: soaking 80mg of mesoporous carbon (CMK-3) in 15mL of 1mol L-1Stirring the mixture at room temperature for 0.5 h; then transferred to a Teflon lined 25mL reaction kettle and held at 150 ℃ for 4 h; naturally cooling, opening the kettle, centrifugally separating the sample, and respectively centrifugally cleaning the sample for three times by using deionized water or absolute ethyl alcohol; and finally, drying the sample at 60 ℃ for 12h in vacuum to obtain the mesoporous carbon modified with rich oxygen-containing groups.
(2)Co2+And dispersion co-adsorption of DCDA on mesoporous carbon matrix: first 100mg CoCl2·6H2Dissolving O and 1g of DCDA in 50mL of deionized water, adding 50mg of functionalized CMK-3, stirring for 1h, centrifuging and washing the precipitate for multiple times, and drying at 60 ℃ overnight to obtain a precursor material.
(3) Calcining to obtain a CoO/Co-N-C/C-500 composite material: will adsorb Co2+And mesoporous carbon of DCDA in N2In an atmosphere at 2 deg.C for min-1The temperature rising rate is increased from room temperature to 550 ℃, the temperature is kept for 2h, and the obtained sample is marked as CoO/Co-N-C/C-550.
FIG. 1 is SEM images of CMK-3 mesoporous carbon and CoO/Co-N-C/C-550, and it can be seen that the overall structure of the mesoporous carbon is preserved after adsorption-calcination, and the substrate is obviously covered with a thin layer of material. FIG. 2 is an XRD pattern of CoO/Co-N-C/C-550, and a weak CoO diffraction peak can be seen, which is caused by very fine CoO crystal grains. FIG. 3a is a TEM image of original mesoporous carbon, consisting of one-dimensionally ordered mesopores; FIG. 3b is a TEM image of CoO/Co-N-C/C-550; FIG. 3c is a sheet structure after enlargement, showing a large number of uniformly dispersed particles, 2-5nm in diameter; from the high resolution lattice image of fig. 3d, the compound particle is CoO. FIG. 4a is an XPS survey of CoO/Co-N-C/C-550 showing C, N, O, Co elements; FIG. 4b is a high resolution spectrum of Co 2p3/2, showing that the cobalt element exists mainly in the form of Co-N (61.7%) mainly from Co-N-C lamellae and Co-O (38.3%) mainly from CoO grains; FIG. 4C is a C1s high resolution spectrum of the sample; FIG. 4d is the high resolution spectrum of N1s for the sample, where Co-N accounts for 31.58% of the total N element content.
Electrocatalytic oxygen reduction and zinc-air battery performance test:
using a rotary disk electrode modified with CoO/Co-N-C/C-550 as a working electrode, a graphite rod as an auxiliary electrode, an Ag/AgCl electrode as a reference electrode, and 0.1mol L of the electrode-1And (3) taking the KOH aqueous solution as an electrolyte, continuously introducing oxygen into the electrolyte, and testing the electrocatalytic oxygen reduction performance of the material. FIG. 5 is a polarization curve (1600rpm) for electrocatalytic oxygen reduction of CoO/Co-N-C/C-550 and commercial Pt/C (20 wt%). Wherein the initial potential of CoO/Co-N-C/C-550 is 0.88V vs. RHE, and the half-wave potential is 0.78V vs. RHE, which is close to that of commercial Pt/C. Furthermore, as can be seen from FIG. 6, CoN-CoOxStability and methanol tolerance of/C-700 are due to commercial Pt/C.
CoO/Co-N-C/C-550 or commercial Pt/C is used as a catalyst, and is mixed with carbon black and Nafion solution to be dripped on carbon paper (the amount of the catalyst on the carbon paper is 0.4mg cm)-2) And then assembling the zinc-air battery by using the anode. Fig. 7a is a polarization and power density curve of the assembled zinc-air cell. The maximum power density of the zinc-air battery taking CoO/Co-N-C/C-550 as the catalyst is up to 132mW cm-2Comparison with commercial Pt/C (152mW cm)-2) Slightly lower. FIG. 7b shows the open circuit voltage as a function of time, with the open circuit voltage of 1.397V for cells catalyzed by CoO/Co-N-C/C-550, which is comparable to the voltage of Pt/C catalyzed cells. Also, the voltage remained almost unchanged after 20 h. When the current density of the discharge is 10mA cm-2Meanwhile, the zinc-air battery using CoO/Co-N-C/C-550 as the catalyst still has a voltage of 1.22V after 20h of discharge, and the stability of the catalyst is proved, as shown in FIG. 7C. FIG. 7d is 10mA cm-2Discharge curve of CoO/Co-N-C/C-550 zinc-air battery under the condition of specific volumeThe amount is 842.3mAh gZn -1Near commercial Pt/C (857.0mAh g)Zn -1). The test curves at different current densities shown in fig. 7e illustrate that the cell has good rate capability. FIG. 7f is a photograph of a 2.2V LED lit up with two CoO/Co-N-C/C-550 zinc-air cells connected in series, and there was no significant change in brightness after 12 h.
Example 2
Preparation and test of a CoO/Co-N-C/C-500 composite material:
the difference from example 1 is that in step (3), Co is adsorbed2+And DCDA in a mesoporous carbon matrix of N2In an atmosphere at 2 deg.C for min-1The heating rate was changed from the target temperature of room temperature heating to 500 ℃ and the obtained sample was labeled as CoO/Co-N-C-500. FIG. 8 is an XRD pattern of the sample, showing that CoO crystals were not evident at 500 ℃. FIG. 9 is a polarization curve (1600rpm) for the electrocatalytic oxygen reduction reaction of CoO/Co-N-C-500 and commercial Pt/C. It can be seen that the limiting current density of CoO/Co-N-C-500 is 3.77mA cm-2The initial potential was 0.86V vs. rhe, and the half-wave potential was 0.77V vs. rhe.
Example 3
Preparation and test of a CoO/Co-N-C/C-600 composite material:
the difference from example 1 is that in step (3), Co is adsorbed2+And DCDA in a mesoporous carbon matrix of N2In an atmosphere at 2 deg.C for min-1The ramp rate was changed from the target temperature at room temperature to 600 deg.C, and the sample obtained was labeled CoO/Co-N-C-600. FIG. 10 is an XRD pattern of the sample, showing that CoO grains are formed at 600 ℃. FIG. 11 is a polarization curve (1600rpm) for the electrocatalytic oxygen reduction reaction of CoO/Co-N-C-600 and commercial Pt/C. It can be seen that the limiting current density of CoO/Co-N-C-600 is 5.30mA cm-2The initial potential was 0.87V vs. rhe and the half-wave potential was 0.77V vs. rhe.
Example 4
CoOxPreparation and test of/Co-N-C/C-650 composite:
the difference from example 1 is that in step (3), Co is adsorbed2+And a mesoporous carbon matrix of DCDAIn N2In an atmosphere at 2 deg.C for min-1The temperature rising rate is changed from the target temperature of room temperature rising to 650 ℃, and the obtained sample is marked as CoOxCo-N-C-650. FIG. 12 is an XRD pattern of the sample, showing that at 650 deg.C, the crystallization becomes more and more pronounced and there is Co3O4And (4) generating. FIG. 13 is CoOxPolarization curves (1600rpm) for electrocatalytic oxygen reduction reactions of/Co-N-C-650 and commercial Pt/C. From the figure, CoO can be seenxThe limiting current density of the/Co-N-C-650 was 3.45mA cm-2The initial potential was 0.85V vs. rhe, and the half-wave potential was 0.76V vs. rhe.
Example 5
Preparation and testing of CoO/C composite material:
the difference from example 1 is that only CoCl is added in step (2)2·6H2O was dissolved in 50mL of deionized water without adding DCDA, yielding Co alone2+The adsorbed mesoporous carbon matrix is calcined to obtain a CoO/C material, an SEM image of the sample is shown in figure 14, and the structure surface has nanoparticle characteristics. FIG. 15 is an XRD pattern of the sample, illustrating the conversion of cobalt ions to CoO at 550 ℃. FIG. 16 is a polarization curve (1600rpm) for the electrocatalytic oxygen reduction reaction of CoO/C and commercial Pt/C. It can be seen that the limiting current density of CoO/C is 3.67mA cm-2The initial potential was 0.83V vs. rhe, and the half-wave potential was 0.69V vs. rhe.
Example 6
Preparation and testing of the N-C/C composite material:
the difference from example 1 is that only DCDA was dissolved in 50mL of deionized water in step (2) without adding CoCl2·6H2O, obtained is a mesoporous carbon matrix with only DCDA adsorbed, and after calcination, an N — C/C material was obtained, and SEM images of the sample are shown in fig. 17, where it can be seen that the matrix is clearly covered with the lamellar component. FIG. 18 is the XRD pattern of the sample, and N-C/C shows two broad peaks at 24.1 and 44.1, which correspond to the (002) and (101) crystal planes of the graphitized region of the mesoporous carbon matrix. FIG. 19 is a polarization curve (1600rpm) for N-C/C and the electrocatalytic oxygen reduction reaction of commercial Pt/C. As can be seen, the limiting current density of CoO/C is 3.87mA cm < -2 >, the initial potential is 0.86V vs. RHE, and the half-wave potential is 0.74V vs. RHE.
The foregoing shows and describes the general principles and features of the present invention, together with the advantages thereof. It will be understood by those skilled in the art that the present invention is not limited to the embodiments described above, and that the foregoing description is only illustrative of the principles of the invention, and that various changes and modifications may be made without departing from the spirit and scope of the invention, which fall within the scope of the invention as claimed. The scope of the invention is defined by the appended claims.

Claims (7)

1. A high-dispersion superfine cobalt oxide particle/cobalt-nitrogen-carbon thin layer/carbon composite material is composed of cobalt oxide nanoparticles, a cobalt-nitrogen-carbon thin layer and a mesoporous carbon matrix; the cobalt oxide nano particles are uniformly dispersed in the cobalt-nitrogen-carbon thin layer and loaded on the mesoporous carbon substrate; the diameter of the cobalt oxide nano-particles is 2-5nm, the cobalt oxide nano-particles account for 2-10% of the composite material by mass, the thickness of the cobalt-nitrogen-carbon thin layer is less than 2nm, and the cobalt oxide nano-particles account for 10-20% of the composite material by mass; and is prepared by the following steps:
(1) functionalization of mesoporous carbon substrates
Soaking a mesoporous carbon matrix in a strong acid solution, placing the solution in a reaction kettle, preserving heat for 2-6 hours at 100-200 ℃ to oxidize the carbon surface to form a large number of oxygen-containing groups, then naturally cooling, and centrifugally cleaning with water or ethanol to obtain a functionalized mesoporous carbon matrix;
(2) dispersion and co-adsorption of cobalt ions and dicyanodiamide on mesoporous carbon matrix
Immersing the functionalized mesoporous carbon matrix into a mixed solution of cobalt salt and dicyanodiamide (DCDA), wherein the molar ratio of the cobalt salt to the DCDA is 1: 10-1: 50; stirring for 0.5-2 h to obtain Co2+Adsorbing the carbon powder and DCDA together on a mesoporous carbon matrix; in the Co-adsorption process, Co2+Under the coordination action of DCDA molecules, high dispersion is kept; finally, centrifugally cleaning the mixture by using water or ethanol, and drying the mixture at the temperature of 30-80 ℃ for later use;
(3) calcining to obtain the high-dispersion superfine cobalt oxide particles/cobalt-nitrogen-carbon thin layer/carbon composite material
Will suckWith Co2+And calcining the mesoporous carbon matrix of DCDA in inert atmosphere, wherein the calcining process comprises the following steps: heating the mixture from room temperature to 500-650 ℃ at the speed of 0.5-10 ℃/min, preserving the heat for 2-4 h, and naturally cooling; under the confinement effect of mesopores, a part of Co2+Converted into a thin Co-N-C layer together with DCDA, a part of Co2+Aggregation and transformation into fine CoO nanoparticles occurs; thereby obtaining the high-dispersion superfine cobalt oxide particles/cobalt-nitrogen-carbon thin layer/carbon (CoO/Co-N-C/C) composite material.
2. A method for preparing the highly dispersed ultrafine cobalt oxide particles/cobalt-nitrogen-carbon thin layer/carbon composite material according to claim 1, comprising the steps of:
(1) functionalization of mesoporous carbon substrates
Soaking a mesoporous carbon matrix in a strong acid solution, placing the solution in a reaction kettle, preserving heat for 2-6 hours at 100-200 ℃ to oxidize the carbon surface to form a large number of oxygen-containing groups, then naturally cooling, and centrifugally cleaning with water or ethanol to obtain a functionalized mesoporous carbon matrix;
(2) dispersion and co-adsorption of cobalt ions and dicyanodiamide on mesoporous carbon matrix
Immersing the functionalized mesoporous carbon matrix into a mixed solution of cobalt salt and dicyanodiamide (DCDA), wherein the molar ratio of the cobalt salt to the DCDA is 1: 10-1: 50; stirring for 0.5-2 h to obtain Co2+Adsorbing the carbon powder and DCDA together on a mesoporous carbon matrix; in the Co-adsorption process, Co2+Under the coordination action of DCDA molecules, high dispersion is kept; finally, centrifugally cleaning the mixture by using water or ethanol, and drying the mixture at 30-80 ℃ for later use;
(3) calcining to obtain the high-dispersion superfine cobalt oxide particles/cobalt-nitrogen-carbon thin layer/carbon composite material
Will adsorb Co2+And calcining the mesoporous carbon matrix of DCDA in inert atmosphere, wherein the calcining process comprises the following steps: heating the mixture from room temperature to 500-650 ℃ at the speed of 0.5-10 ℃/min, preserving the heat for 2-4 h, and naturally cooling; under the confinement effect of mesopores, a part of Co2+Together with DCDA, into a thin layer of Co-N-C, a portion of Co2+Aggregation and transformation into fine CoO nanoparticles occurs; thereby obtaining high-dispersion ultrafine cobalt oxide particles/cobalt-a nitrogen-carbon thin layer/carbon (CoO/Co-N-C/C) composite.
3. The method for preparing the highly dispersed ultrafine cobalt oxide particles/cobalt-nitrogen-carbon thin layer/carbon composite material according to claim 2, wherein the strong acid solution in the step (1) is 1-2 mol L-1The nitric acid solution of (1).
4. The method for preparing highly dispersed ultrafine cobalt oxide particles/cobalt-nitrogen-carbon thin layer/carbon composite material according to claim 2, wherein the cobalt salt solution in the step (2) is cobalt chloride solution, cobalt nitrate solution or cobalt sulfate solution.
5. The method for preparing the highly dispersed ultrafine cobalt oxide particles/cobalt-nitrogen-carbon thin layer/carbon composite material according to claim 2, wherein the concentration of the cobalt salt solution in the step (2) is 1-10 mmol L-1The concentration of the DCDA solution is 0.1-0.5 mol L-1。
6. The method for preparing highly dispersed ultrafine cobalt oxide particles/cobalt-nitrogen-carbon thin layer/carbon composite material according to claim 2, wherein the inert atmosphere in the step (3) is nitrogen atmosphere or argon atmosphere.
7. The use of the highly dispersed ultrafine cobalt oxide particles/cobalt-nitrogen-carbon thin layer/carbon composite material according to claim 1 as a positive electrode catalyst for a metal-air battery.
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