CN111924891A - Bimetal cobalt oxide-based oxide, preparation method and application thereof - Google Patents

Bimetal cobalt oxide-based oxide, preparation method and application thereof Download PDF

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CN111924891A
CN111924891A CN202010659033.2A CN202010659033A CN111924891A CN 111924891 A CN111924891 A CN 111924891A CN 202010659033 A CN202010659033 A CN 202010659033A CN 111924891 A CN111924891 A CN 111924891A
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cobalt
oxide
mncoo
based oxide
cobalt oxide
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王松博
赵楠楠
唐娜
张蕾
杜威
程鹏高
项军
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Tianjin University of Science and Technology
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Abstract

The invention discloses a bimetal cobalt oxide-based oxide with a general formula of MaCobOnWherein a is 0 to 3, b is 0 to 3, and a and b do not include 0, n is determined by the oxidation state of other elements, M is selected from one or more of iron, nickel, manganese, zinc or copper, and the surface of the bimetallic cobalt oxide-based oxide has defects. The invention also discloses a preparation method and application of the catalyst. The invention controls the structure of the precursor by regulating and controlling the optimal metal ion ratio of two transition metals and changing the mixed alcohol solvent in the solvothermal reaction, and finally, M with different active site distributions can be obtainedaCobOn. M prepared by the inventionaCobOnThe catalyst used as an oxygen reduction catalyst has proper defects, high activity and stable performance, and simultaneously, the introduction of M metal greatly improves the electron transfer efficiency and realizes the high-efficiency oxygen reduction process. Invention MaCobOnThe preparation process is simple, the process operability is strong, and the method has good application prospect in the fields of metal-air batteries, fuel cells, electrolytic cells, super capacitors and the like.

Description

Bimetal cobalt oxide-based oxide, preparation method and application thereof
Technical Field
The invention belongs to the technical field of electrocatalysts, and particularly relates to a bimetallic cobalt oxide-based oxide (M)aCobOn) A preparation method and application of the catalyst.
Background
As fossil fuels are depleted, the development of new, green, and renewable energy sources has received widespread attention. Since fuel cells have high energy conversion efficiency and are considered to be ideal energy conversion and storage technologies for environmental friendliness, Proton Exchange Membrane Fuel Cells (PEMFCs) are currently the most widely studied fuel cells, in which an Oxygen Reduction Reaction (ORR) and a Hydrogen Oxidation Reaction (HOR) occur at a cathode and an anode, respectively, and the ORR process becomes one of the key factors limiting the performance of the fuel cells due to the involvement of complex kinetic processes. At present, ORR catalysts are mainly noble metals such as Pt, but the noble metal catalysts have limited resources and higher cost and are difficult to be commercially applied on a large scale. Therefore, it is a necessary trend to replace noble metals with low-cost, abundant non-noble metal catalysts.
Cobalt (Co) is one of the most abundant elements in the earth's crust, and its oxide (Co) is theoretically3O4CoO, etc.) is second only to the noble metal Pt, and thus cobalt oxide is considered as a desirable alternative to noble metal catalysts. But do notThat is, cobalt oxide alone is less conductive and less oxygen adsorbing, resulting in a much lower than theoretical ORR performance. The transition metals of Fe, Mn, Ni and the like have various variable valence states, and can be easily reduced and oxidized in the reaction process so as to realize catalytic cycle. Therefore, doping transition metals such as manganese in cobalt oxide to prepare bimetallic oxides such as cobalt and manganese is an effective way to improve the ORR performance of the bimetallic oxides. However, the preparation method of the metal oxide catalyst commonly used at present is still in the experimental groping stage, and especially, the double-multi-metal oxide as the electrocatalyst is not systematically explored and reveals the theoretical mechanism of the activity improvement, so that the catalytic activity of the double-multi-metal oxide catalyst is difficult to artificially regulate and control according to the requirements.
The document CN 104001520B describes a preparation process of a cobalt-manganese composite oxide material, which adopts a low-temperature growth environment to inhibit the aggregation phenomenon of precipitates, and finally obtains a manganese-based composite metal oxide catalyst with high specific surface area and high catalytic denitration activity after calcining the split-grown crystals. The bimetal composite oxide obtained in the patent has larger specific surface area (153.5 m) due to the crystal growing by splitting2In terms of/g). The higher the specific surface area, the more favorable the catalyst is in terms of its catalytic activity. However, the addition of a precipitant may result in a local concentration that is too high, resulting in agglomeration or a composition that is not sufficiently uniform, resulting in a mixture of heterogeneous oxides.
Patent document CN 105428084B discloses a nano-flocculent cobalt-manganese composite oxide as an electrode material, which has a specific capacitance of 279.9F/g, and after 5000 charge-discharge cycles, the specific capacitance retention rate is still 89.2%. The method has simple preparation process and low raw material price. However, the S element is generally present in the form of sulfate in the cobalt-manganese composite oxide, and in the use of the cobalt-manganese composite oxide as a catalyst, an oxygen electrode of a fuel cell, or the like, the S element poisons the catalyst or decomposes sulfate to generate SO2The gas shortens the service life of the cobalt-manganese composite oxide, and is not beneficial to the promotion of catalytic reaction activity.
Pan-gang-Ping in "a submicron-sized Co-Mn composite oxide material and its preparation method" (patent application number)The main preparation process is proposed for CN 104979555B): adding a solvent and a dispersant into the cobalt-manganese composite salt wet material, and then carrying out wet grinding to obtain submicron-grade cobalt-manganese composite salt slurry; and placing the submicron cobalt-manganese composite salt slurry in an aerobic atmosphere for multi-stage roasting, and sieving to obtain the submicron cobalt-manganese composite oxide material. The particle diameter of the cobalt-manganese composite oxide material is 0.8 mu m, and the specific surface area is 20.1m2In terms of a specific amount of Na, the content was 28ppm and the content of S was 45 ppm. The preparation process disclosed by the patent has the advantages of low equipment investment, simplicity and controllability in operation, low production cost and the like, and the product is good in appearance and low in impurity content. However, the cobalt-manganese oxide has a small specific surface area and poor structural stability, and thus the service life of the cobalt-manganese composite oxide is shortened.
Patent document CN 103500667 a discloses a cathode material of a lithium ion battery made of iron-cobalt-manganese composite oxide and a preparation method thereof, wherein the method comprises the following steps: dispersing the mixture of nickel salt, cobalt salt and manganese salt in water and absolute ethanol solution of carbon material or precursor of different derived carbon, reacting, and calcining at high temperature to obtain black FeCoMnO4And (3) powder. The iron-cobalt-manganese composite oxide prepared by the method has the advantages of rich raw materials, simple preparation process and easy operation, and simultaneously, the product synthesized by the hydrothermal synthesis method adopted by the method has uniform granularity, high yield and low cost. The particle size distribution is 300-600 nm, the specific mass capacity is 1140mAh/g, which is 3 times of the specific mass capacity (372mA h/g) of the current commercialized graphite. After circulating for 350 circles under the current density of 0.2A/g, the specific mass capacity is still 1.88 times of that of the graphite. But the space distribution of active sites is limited by the crystal form of the product, and the catalytic reaction activity of the product needs to be improved.
Therefore, it is desirable to prepare a high specific surface area, highly active bimetallic cobalt oxide-based oxide.
Disclosure of Invention
The invention aims to provide a bimetallic cobalt oxide-based oxide (M) which has high specific surface area and high activity and can be synthesizedaCobOn) The method of (1). The method of the invention is characterized in that different polyols are used as reaction solvents and transition metal cobaltAnd reacting with metal salts such as nickel or iron to prepare a bimetallic organic precursor, and roasting at high temperature to obtain the bimetallic cobalt oxide-based oxide with controllable defect type spatial distribution. Defects in the catalyst can be used as active sites for catalytic reaction, the content and distribution of the active sites are critical to the catalytic performance of the catalyst, and the defects which enable the cobalt oxide-based catalyst to have a proper amount and are beneficial to ORR reaction are main control variables of the invention by controlling a synthesis method and the type of the polyalcohol.
The invention successfully synthesizes the bimetallic cobalt oxide-based oxide (M)aCobOn) The presence of suitable amounts of defects and metal ions with a suitable spatial distribution results in a catalyst with excellent ORR performance. Electrochemical test results show that the catalyst synthesized in the polyol mixed solvent and with the optimal metal proportion has the half-wave potential as high as 0.79mV Vs RHE in an alkaline medium, is only 20mV worse than commercial Pt/C, is superior to the reported performance, and has excellent stability.
In a first aspect, the invention provides a bimetallic cobalt oxide-based oxide of the general formula MaCobOnWherein a is 0 to 3, b is 0 to 3, a and b do not include 0, n is determined by the oxidation state of other elements, and M is one or more selected from iron, nickel, manganese, zinc or copper. The surface of the bimetal cobalt oxide-based oxide has defect sites, and a proper amount of defects are used as active sites to enable the bimetal cobalt oxide-based oxide to have excellent oxygen reduction ORR performance. In the present invention, the total amount of surface defects and active sites contained in the oxide can be calculated by XPS.
The second aspect of the present invention provides a method for preparing a bimetal cobalt oxide-based oxide, comprising the steps of:
s1, preparing an alcohol mixed solution, placing the alcohol mixed solution in a Teflon lining reaction kettle, simultaneously dropwise adding a cobalt source and an M metal source into the alcohol mixed solution, magnetically stirring, and then carrying out a solvothermal reaction;
s2, quenching the reaction product obtained in the step S1, separating, washing and drying to obtain a bimetallic cobalt oxide-based oxide precursor; the centrifugal separation method can be adopted, and the washed product is put into a vacuum drying oven for drying;
and S3, grinding the bimetal cobalt oxide based oxide precursor in the step S2, and then roasting to obtain the bimetal cobalt oxide based oxide.
Preferably, in step S1, the cobalt source is selected from one or more of cobalt chloride, cobalt acetate and cobalt nitrate; the M metal source is selected from one or more of nitrate, acetate or chloride of M metal. Different kinds of M metal sources or cobalt sources may affect the ORR performance of the prepared catalyst, probably because different kinds of M metal sources or cobalt sources may affect the crystallinity of the product and the spatial distribution of the microscopic active sites after calcination. The bimetallic cobalt oxide-based oxide prepared by taking cobalt acetate as a cobalt source and acetate as an M metal source is used as an ORR catalyst and shows more excellent catalytic activity in an alkaline medium.
Preferably, the alcohol mixed solution is a mixed solution of at least one alcohol selected from ethylene glycol, 1, 2-propylene glycol, 1, 3-butylene glycol, 1, 4-butylene glycol or glycerol and ethanol, and the alcohol mixed solution is at least two selected from ethanol, ethylene glycol, 1, 2-propylene glycol, 1, 3-butylene glycol, 1, 4-butylene glycol or glycerol. The main function of the alcohol mixed solvent in the solvothermal reaction process is to generate a bimetallic ester salt precursor, and in the subsequent calcining process, the catalyst product obtained after the precursor is calcined keeps mesoporous and large specific surface area through the decomposition of hydrocarbon components of the precursor and the gradual volatilization of the solvent, so that the catalytic reaction efficiency of the catalyst is improved.
Preferably, the alcohol mixed solution is a mixed solution of 1, 3-propylene glycol and ethanol, and the volume ratio of the 1, 3-propylene glycol to the ethanol is (1-3): (3-1); the mass ratio of the cobalt source to the M metal source is (1-4): (4-1). The ethanol in the alcohol mixed solution only plays a role of diluting an alcohol solvent except ethanol in the solvothermal reaction so as to promote the forward reaction. And the alcohol solvent other than ethanol in the alcohol mixed solution is called a target alcohol solvent, and the target refers to the alcohol solvent which is expected to be used for generating the metal ester salt. With the increase of the dosage of different solvents, metal ions in the reaction system completely react to obtain a precursor, and then the precursor is calcined to obtain the cobalt manganese oxide with the designed bimetallic ratio. However, it is preferred in the present invention that the alcohol solvent of interest in the mixed alcohol solution: the volume ratio of ethanol is not suitable to be too high, and when the volume ratio of ethanol is too high, the yield and the precursor quality in a reaction system are reduced, so that metal ions cannot completely react with a target alcohol solvent, and further the content of two metals in a reaction product, namely a bimetallic oxide, deviates from the designed metal ratio; therefore, the volume ratio of the target alcohol solvent to the ethanol is particularly preferably controlled to be (1-3): (3-1). In the step S1, the stirring time is 0.5-1 h, the solvothermal reaction temperature is 150-300 ℃, and the solvothermal reaction time is 1-5 h.
Preferably, the drying temperature in the step S2 is 50-70 ℃, and the drying time is 10-24 h.
Preferably, the roasting temperature in the step S3 is 200-1000 ℃, and the roasting time is 1-3 h.
Wherein the bimetal cobalt oxide based oxide (M)aCobOn) In conjunction with XPS, the results of the analysis allow the total amount of defects and active sites contained in the sample to be calculated.
In a third aspect of the invention, there is provided a use of said bimetallic cobalt oxide-based oxide, said MaCobOnAs a catalyst for catalyzing the cathode oxygen reduction reaction of a metal-air battery. And can be widely applied to electrode materials of catalytic supercapacitors and electrolytic cells.
The fourth aspect of the present invention provides a use of said bimetallic cobalt oxide-based oxide, said MaCobOnAs a catalyst for increasing the rate of the oxygen reduction reaction on the cathode side of a hydrogen-oxygen fuel cell.
Compared with the prior art, the invention has the following advantages:
1. aiming at the technical problem that products of the existing methods such as a coprecipitation method, a sol-gel method and the like are easy to agglomerate or the composition is not uniform enough, the invention develops a preparation process based on the process idea of 'solvothermal synthesis method-roasting', and successfully prepares the bimetallic cobalt oxide-based oxide MaCobOnAnd the bimetallic oxygenThe ORR catalytic performance of the cobalt-based catalyst is obviously improved relative to the catalytic performance of cobalt oxide and M metal oxide alone.
2. In the preparation process of the bimetallic cobalt oxide-based oxide, a mixed solution of ethanol and at least one of ethylene glycol, 1, 2-propylene glycol, 1, 3-butylene glycol, 1, 4-butylene glycol or glycerol is selected as a solvent for solvothermal reaction, and ethanol in the alcohol mixed solution only plays a role in diluting an alcohol solvent except ethanol in the solvothermal reaction so as to promote the forward progress of the reaction. And the alcohol solvent other than ethanol in the alcohol mixed solution is called a target alcohol solvent, and the target refers to the alcohol solvent which is expected to be used for generating the metal ester salt. The number and type of alcoholic hydroxyl groups in the mixed alcohol solution can affect the structure of the precursor, so that the bimetal cobalt oxide-based oxide is finally affected. Compared with a single ethanol solvent, the mixed solvent of ethanol and propylene glycol is selected as the solvent for the solvothermal reaction, so that the prepared MnCoO-Pg has the highest half-wave potential and more excellent ORR performance.
3. Different kinds of M metal sources or cobalt sources in the preparation process of the bimetallic cobalt oxide-based oxide can influence the ORR performance of the prepared catalyst, and the reason is that the different kinds of M metal sources or cobalt sources can influence the crystallinity of the product and the spatial distribution of the calcined microscopic active sites. The bimetallic cobalt oxide-based oxide prepared by taking cobalt acetate as a cobalt source and acetate as an M metal source is used as an ORR catalyst and shows more excellent catalytic activity in an alkaline medium.
4. The molar ratio of the M metal source to the cobalt source in the preparation process of the bimetal cobalt oxide-based oxide can also influence the ORR performance of the prepared catalyst, the surface defect contents of the bimetal cobalt oxide-based oxide prepared by different molar ratios of the M metal source to the cobalt source are different, the ORR catalytic activity of the bimetal cobalt oxide-based oxide catalyst in an alkaline medium is changed along with the change of the surface defect, and when the molar ratio of the Mn metal source to the cobalt source is 2: the MnCoO-Pg sample prepared at the time 3 has the total defect concentration of 16.31 percent and has better ORR catalytic activity.
5. According to the invention, a precursor is prepared by a solvent thermal synthesis method, and then is roasted, organic matters in the bimetal cobalt oxide based oxide precursor are oxidized to form water vapor and carbon dioxide after roasting, a large number of mesopores which are not easy to agglomerate are formed in the remaining oxide, and the roasting temperature is preferably selected to form a crystal form with favorable distribution of active sites, so that the catalytic activity is greatly improved.
6. The final bimetal cobalt oxide based oxide (M) prepared by the inventionaCobOn) The composite material has a large surface area, a proper amount of defects are used as active sites, the structural stability is good, and the application of the composite material in industries such as fuel cell catalysts, metal-air cell electrode materials and the like can be expanded; the preparation process has the advantages of less equipment investment, simple and controllable operation, low production cost, easily obtained raw materials, short production period and the like, and is very easy to realize mass production.
Drawings
FIG. 1 shows Mn prepared in examples 1,2 and 33O4-Pg、Co3O4XRD patterns of Pg, MnCoO-Pg.
FIG. 2 shows Mn prepared in examples 1,2 and 33O4-Pg、Co3O4-electron Scanning Electron Microscopy (SEM) images of Pg, MnCoO-Pg.
FIG. 3 shows Mn prepared in examples 1,2 and 33O4-Pg、Co3O4-graph of linear scan curve (LSV) of ORR of Pg, MnCoO-Pg.
FIG. 4 is a view showing the surface N of MnCoO-Pg bimetal cobalt oxide based oxide prepared in example 32Adsorption, de-attachment and pore size distribution.
FIG. 5 is a graph of the linear scanning curve (LSV) of MnCoO-Et, MnCoO-Eg, MnCoO-Gly, MnCoO-Pg bimetal cobalt oxide based oxides ORR prepared in examples 3, 4, 5, 6.
FIG. 6 is a graph of the linear scan curve (LSV) of the ORR of FeCoO-Pg, ZnCoO-Pg, CuCoO-Pg, and NiCoO-Pg bimetallic cobalt oxide-based oxides prepared in examples 7-10 and 3.
FIG. 7 is a graph of linear scanning curves (LSV) of MnCoO-Pg-1, MnCoO-Pg-2, and MnCoO-Pg-3 bimetal cobalt oxide based oxides ORR prepared in examples 11 to 13.
FIG. 8 is a graph of linear scanning curves (LSV) of MnCoO-Pg-11, MnCoO-Pg-22, and MnCoO-Pg-33 bimetal cobalt oxide based oxides ORR prepared in examples 14 to 16.
Detailed Description
The present invention will be described in further detail below for the sake of clarity and clarity, but the scope of the present invention is not limited to the following specific examples. In the nomenclature of the catalysts prepared in the following examples, the suffix-Et means that the solvent is ethanol alone when the solvothermal reaction is carried out during the preparation; the suffix-Pg refers to the mixture of ethanol and propylene glycol as the solvent during the solvothermal reaction in the preparation process; the suffix-Eg means that the solvent is a mixture of ethanol and ethylene glycol when the solvothermal reaction is carried out in the preparation process; the suffix-Gly means that the solvent in the preparation process is a mixture of ethanol and glycerol when the solvothermal reaction is carried out.
Example 1:
cobalt oxide (Co)3O4Preparation of Pg): 0.0012mol manganese (II) acetate tetrahydrate, 0.0048mol cobalt (II) acetate tetrahydrate and 60mL ethanol, 20mL 1, 3-propanediol were mixed with stirring in a 100mL teflon liner for half an hour. The stainless steel reaction vessel was then heated in an oven at 180 ℃ for 1.5 hours. Thereafter, the resulting cobalt oxide precursor (i.e., CoPg) was collected, washed with ethanol, centrifuged, and dried at 60 ℃ overnight. Subsequently, the dried precursor was ground to obtain a powdery precursor. Finally, calcination was carried out in air at 300 ℃ for 2 hours (heating rate 5 ℃ C. min.)-1). The method described above gives Co3O4-Pg。
Example 2:
manganese oxide (Mn)3O4Preparation of Pg): 0.0060mol manganese (II) acetate tetrahydrate and 60mL ethanol, 20mL 1, 3-propanediol were mixed with stirring in 100mL teflon liner for half an hour. The stainless steel reaction vessel was then heated in an oven at 180 ℃ for 1.5 h. Thereafter, the resulting manganese oxide precursor (i.e., MnPg) was collected, washed with ethanol, centrifuged, and dried at 60 ℃ overnight. Subsequently, the dried precursor is ground to obtain a powderA precursor in a powder form. Finally, calcination was carried out in air at 300 ℃ for 2 hours (heating rate 5 ℃ C. min.)-1) Mn was prepared as described above3O4-Pg。
Example 3:
preparing a manganese-cobalt bimetallic cobalt oxide-based oxide: 0.0012mol manganese (II) acetate tetrahydrate, 0.0048mol cobalt (II) acetate tetrahydrate and 60mL ethanol, 20mL 1, 3-propanediol were mixed with stirring in a 100mL teflon liner for half an hour. The stainless steel reaction vessel was then heated in an oven at 180 ℃ for 1.5 hours. Thereafter, the resulting manganese-cobalt bimetallic precursor (i.e., MnCoPg) was collected, washed with ethanol, centrifuged, and dried at 60 ℃ overnight. Subsequently, the dried precursor was ground to obtain a powdery precursor. Finally, calcination was carried out in air at 300 ℃ for 2 hours (heating rate 5 ℃ C. min.)-1). MnCoO-Pg is obtained.
FIG. 2 shows Mn prepared in examples 1,2 and 33O4-Pg、Co3O4-electron Scanning Electron Microscope (SEM) images of Pg, MnCoO-Pg, wherein fig. 2(a) is a Scanning Electron Microscope (SEM) image of the synthesized cobalt oxide catalyst precursor (CoPg) as a hollow spherical structure; FIG. 2(b) is a synthesized cobalt oxide catalyst product (Co)3O4-Pg) to clearly show that the catalyst product has a fluffy morphology; FIG. 2(e) is a Scanning Electron Microscope (SEM) image of a synthesized manganese oxide catalyst precursor (MnPg) in the form of a bar-shaped bulk structure; FIG. 2(f) is a graph of the synthesized manganese oxide catalyst product (Mn)3O4-Pg) which becomes a collapsed cumquat-like morphology; FIG. 2(c) is a Scanning Electron Microscope (SEM) image of a synthesized manganese-cobalt bimetallic cobalt oxide-based oxygen reduction catalyst precursor (MnCoPg) which is a fine cotton-like structure; fig. 2(d) is a Scanning Electron Microscope (SEM) image of the synthesized manganese-cobalt bimetallic cobalt oxide-based catalyst product (MnCoO-Pg), which maintains the fluffy morphology of the precursor and thus has a large specific surface area, facilitates the rapid transmission of electrolyte ions in the electrode body phase, and significantly improves the electrochemical performance.
FIG. 1 shows examples 1,2 and 3Mn produced3O4-Pg、Co3O4XRD patterns of Pg, MnCoO-Pg. The characterization result shows that the MnCoO-Pg is in a spinel crystal form.
FIG. 4 shows MnCoO-Pg surface N2Adsorption, de-attachment and pore size distribution. The characterization result shows that the specific surface area of MnCoO-Pg is as high as 115m under the synthesis condition of the example2And it has a mesoporous structure which is favorable for oxygen adsorption.
FIG. 3 shows Mn prepared in examples 1,2 and 33O4-Pg、Co3O4-graph of linear scan curve (LSV) of ORR of Pg, MnCoO-Pg. As can be seen from FIG. 3, Co3O4Pg shows poor ORR catalytic activity in alkaline medium with a half-wave potential of 0.61mV Vs RHE. Mn3O4The catalyst shows lower ORR catalytic activity in an alkaline medium, and the half-wave potential of the catalyst is as high as 0.76mV Vs RHE. The MnCoO-Pg catalyst shows excellent ORR catalytic activity in an alkaline medium, the half-wave potential of the MnCoO-Pg catalyst is as high as 0.79mV Vs RHE, the half-wave potential is only 20mV worse than that of commercial Pt/C, the MnCoO-Pg catalyst is superior to the reported performance, and the MnCoO-Pg catalyst has excellent stability. The ORR performance of the prepared MnCoO-Pg catalyst is obviously superior to that of pure Mn3O4、Co3O4A catalyst.
TABLE 1 Mn prepared in examples 1,2, 33O4-Pg、Co3O4-X-ray photoelectron spectroscopy (XPS) measurements of Pg, MnCoO-Pg, calculated surface defect content.
TABLE 1 content of surface defects calculated from X-ray photoelectron spectroscopy (XPS) data of different samples
Figure BDA0002577829420000081
Examples 4 to 6:
examples 4 to 6 were conducted by using different kinds of alcohol mixed solutions as solvents for solvothermal reaction, and examining the influence of the different alcohol solvents on the ORR performance of a bimetal cobalt oxide based oxide.
Examples 4 to 6 respectively prepare MnCoO-Et, MnCoO-Eg and MnCoO-Gly by the same preparation method as example 3 except that the solvent for the solvothermal reaction is different, and the specific preparation conditions and the electrochemical characterization results are shown in Table 2.
TABLE 2 preparation conditions of bimetallic cobalt oxide-based oxides and ORR properties thereof in examples 4-6
Figure BDA0002577829420000091
FIG. 5 is a linear scanning curve (LSV) diagram of the oxygen reduction reaction of four kinds of bimetallic cobalt oxide-based oxides, MnCoO-Et, MnCoO-Eg, MnCoO-Gly, MnCoO-Pg, and as can be seen from FIG. 5 and Table 2, the four kinds of bimetallic cobalt oxide-based oxides, MnCoO-Et, MnCoO-Eg, MnCoO-Gly, MnCoO-Pg, as ORR catalysts, exhibit the catalytic activity sequences in alkaline medium as follows: MnCoO-Et is smaller than MnCoO-Gly and smaller than MnCoO-Eg and smaller than MnCoO-Pg, namely, compared with the method of using single ethanol as a solvent in the solvothermal reaction, the method has the advantages that the ORR performance of the prepared bimetallic cobalt oxide-based oxide is better, and the mixed solvent of ethanol and propylene glycol is used as the solvent in the solvothermal reaction, so that the prepared MnCoO-Pg has the highest half-wave potential and the ORR performance is more excellent.
Examples 7 to 10:
examples 7 to 10 were each prepared using different metals M to prepare a bimetal oxide-based oxide, and the influence of the different metals M on the ORR performance of the bimetal oxide-based oxide was examined.
Examples 7 to 10 were prepared FeCoO-Pg, NiCoO-Pg, CuCoO-Pg, and ZnCoO-Pg, respectively, in the same manner as in example 3 except that the M metal species was different, and specific preparation conditions and electrochemical characterization results are shown in Table 3.
TABLE 3 preparation conditions of bimetallic cobalt oxide-based oxides and ORR properties thereof in examples 7-10
Figure BDA0002577829420000092
Figure BDA0002577829420000101
FIG. 6 is a linear sweep curve (LSV) diagram of oxygen reduction reaction of five kinds of bimetallic cobalt oxide based oxides, FeCoO-Pg, ZnCoO-Pg, CuCoO-Pg, NiCoO-Pg, MnCoO-Pg, and in combination with FIG. 6 and Table 3, five kinds of bimetallic cobalt oxide based oxides, FeCoO-Pg, ZnCoO-Pg, CuCoO-Pg, NiCoO-Pg, MnCoO-Pg, as ORR catalysts, show catalytic activity sequences in alkaline medium as follows: FeCoO-Pg is smaller than ZnCoO-Pg and smaller than CuCoO-Pg and smaller than NiCoO-Pg and smaller than MnCoO-Pg, namely, MnCoO-Pg prepared by taking manganese as M metal has the highest half-wave potential and more excellent ORR performance.
Examples 11 to 16:
examples 11 to 16 bimetal oxide based oxides were prepared using different M metal sources and cobalt sources, respectively, and the influence of the different M metal sources and cobalt sources on the ORR performance of the bimetal oxide based oxides was examined.
Examples 11 to 16 were prepared MnCoO-Pg-1, MnCoO-Pg-2, MnCoO-Pg-3, MnCoO-Pg-11, MnCoO-Pg-22, and MnCoO-Pg-33, respectively, in the same manner as in example 3 except that the M metal source and the cobalt source were different, and specific preparation conditions and electrochemical characterization results are shown in Table 4.
TABLE 4 preparation conditions of bimetallic cobalt oxide-based oxides and ORR properties thereof in examples 11 to 16
Figure BDA0002577829420000102
Figure BDA0002577829420000111
FIG. 7 is a graph of the linear scanning curves (LSV) of three types of bimetallic cobalt oxide based oxide oxygen reduction reactions, MnCoO-Pg-1, MnCoO-Pg-2, and MnCoO-Pg-3; FIG. 8 is a graph of the linear scanning curves (LSV) of three types of bimetallic cobalt oxide-based oxide oxygen reduction reactions, MnCoO-Pg-11, MnCoO-Pg-22, and MnCoO-Pg-33; as can be seen from fig. 7, fig. 8 and table 4, the catalytic activity sequences exhibited by the different bimetallic cobalt oxide based oxides as ORR catalysts in the alkaline medium in examples 11-16 are: MnCoO-Pg-1, MnCoO-Pg-2, MnCoO-Pg-3; MnCoO-Pg-11 MnCoO-Pg-22 MnCoO-Pg-33, that is, under the same condition, the prepared bimetallic cobalt oxide based oxide has more excellent ORR performance by adopting the acetate of M metal and cobalt acetate as an M metal source and a cobalt source.
Examples 17 to 19:
examples 17 to 19 the molar ratio of the M metal source to the cobalt source in the preparation process was adjusted to 1: 4. 1: 1. 3: 2. 4: 1 to obtain MnCoO-Pg (1: 4), MnCoO-Pg (1: 1), MnCoO-Pg (3: 2) and MnCoO-Pg (4: 1). The preparation method is the same as that of example 3, only the molar ratio of the Mn metal source to the cobalt source is different, and the specific preparation conditions and electrochemical characterization results are shown in Table 5.
TABLE 5 preparation conditions of bimetallic cobalt oxide-based oxides and ORR properties thereof in examples 7-10
Figure BDA0002577829420000112
Figure BDA0002577829420000121
XPS characterization of MnCoO-Pg, MnCoO-Pg (1: 4), MnCoO-Pg (3: 2), MnCoO-Pg (4: 1) calculated surface defect levels, and half-wave potentials for each catalyst sample are shown in the table above. As can be seen from the data in table 5, the ORR catalytic activity of the MnCoO-Pg catalyst in alkaline medium varies with the surface defects, wherein when the molar ratio of the M metal source to the cobalt source is 1: the MnCoO-Pg sample prepared at 4 has a total defect concentration of 16.31 percent and has better ORR catalytic activity.
The foregoing illustrates and describes the principles, general features, and advantages of the present invention. It should be understood by those skilled in the art that the above embodiments do not limit the present invention in any way, and all technical solutions obtained by means of equivalent substitution, addition or equivalent transformation fall within the protection scope of the present invention.

Claims (10)

1. A bimetallic cobalt oxide-based oxide characterized by the general formula MaCobOnWherein a is 0 to 3, b is 0 to 3, and a and b do not include 0, n is determined by the oxidation state of other elements, M is selected from one or more of iron, nickel, manganese, zinc or copper, and the surface of the bimetal cobalt oxide based oxide has defects.
2. A method for preparing a bimetal cobalt oxide based oxide as claimed in claim 1, comprising the steps of:
s1, preparing an alcohol mixed solution, putting the alcohol mixed solution into a Teflon lining reaction kettle, simultaneously dropwise adding a cobalt source and an M metal source into the alcohol mixed solution, stirring, and then carrying out a solvothermal reaction;
s2, quenching the reaction product obtained in the step S1, separating, washing and drying to obtain a bimetallic cobalt oxide-based oxide precursor;
and S3, grinding the bimetal cobalt oxide based oxide precursor in the step S2, and then roasting to obtain the bimetal cobalt oxide based oxide.
3. The preparation method according to claim 2, wherein in step S1, the cobalt source is selected from one or more of cobalt chloride, cobalt acetate and cobalt nitrate; the M metal source is selected from one or more of nitrate, acetate or chloride of M metal.
4. The method according to claim 2, wherein the alcohol mixed solution is a mixed solution of ethanol and at least one alcohol selected from the group consisting of ethylene glycol, 1, 2-propanediol, 1, 3-butanediol, 1, 4-butanediol, and glycerin.
5. The preparation method according to claim 2, wherein the alcohol mixed solution is a mixed solution of 1, 3-propanediol and ethanol, and the volume ratio of the 1, 3-propanediol to the ethanol is (1-3): (3-1); the mass ratio of the cobalt source to the M metal source is (1-4): (4-1).
6. The method according to claim 2, wherein the stirring time in step S1 is 0.5-1 h, the solvothermal reaction temperature is 150-300 ℃, and the solvothermal reaction time is 1-5 h.
7. The method according to claim 2, wherein the drying temperature in step S2 is 50-70 ℃ and the drying time is 10-24 hours.
8. The method according to claim 2, wherein the calcination temperature in step S3 is 200-1000 ℃ and the calcination time is 1-3 hours.
9. Use of a bimetallic cobalt oxide-based oxide according to claim 1, wherein M is addedaCobOnAs a catalyst for catalyzing the cathode oxygen reduction reaction of a metal-air battery.
10. Use of a bimetallic cobalt oxide-based oxide according to claim 9, characterized in that M is addedaCobOnAs a catalyst for increasing the rate of the oxygen reduction reaction on the cathode side of a hydrogen-oxygen fuel cell.
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