CN113224325A - High-efficiency bifunctional oxygen electrocatalyst with heterogeneous structure and heterogeneous metals, and preparation and application thereof - Google Patents

High-efficiency bifunctional oxygen electrocatalyst with heterogeneous structure and heterogeneous metals, and preparation and application thereof Download PDF

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CN113224325A
CN113224325A CN202110175168.6A CN202110175168A CN113224325A CN 113224325 A CN113224325 A CN 113224325A CN 202110175168 A CN202110175168 A CN 202110175168A CN 113224325 A CN113224325 A CN 113224325A
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heterogeneous
cobalt
manganese
catalyst
electrocatalyst
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陈作锋
牛艳丽
滕雪
巩帅奇
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Tongji University
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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
    • H01M4/90—Selection of catalytic material
    • H01M4/9016—Oxides, hydroxides or oxygenated metallic salts
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B82—NANOTECHNOLOGY
    • B82Y—SPECIFIC USES OR APPLICATIONS OF NANOSTRUCTURES; MEASUREMENT OR ANALYSIS OF NANOSTRUCTURES; MANUFACTURE OR TREATMENT OF NANOSTRUCTURES
    • B82Y30/00—Nanotechnology for materials or surface science, e.g. nanocomposites
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B82—NANOTECHNOLOGY
    • B82Y—SPECIFIC USES OR APPLICATIONS OF NANOSTRUCTURES; MEASUREMENT OR ANALYSIS OF NANOSTRUCTURES; MANUFACTURE OR TREATMENT OF NANOSTRUCTURES
    • B82Y40/00—Manufacture or treatment of nanostructures
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M12/00—Hybrid cells; Manufacture thereof
    • H01M12/08—Hybrid cells; Manufacture thereof composed of a half-cell of a fuel-cell type and a half-cell of the secondary-cell type
    • 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
    • H01M4/9041—Metals or alloys
    • 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

Abstract

The invention relates to a high-efficiency bifunctional oxygen electrocatalyst with heterogeneous structure and heterogeneous metals, and preparation and application thereof, wherein the catalyst is prepared by the following method: (1) dispersing soluble cobalt salt, soluble manganese salt and nitrilotriacetic acid serving as raw materials in a solvent, uniformly mixing, heating for reaction, cooling, centrifuging and drying to obtain a cobalt-manganese-based metal organic compound precursor; (2) and carrying out pyrolysis treatment on the cobalt-manganese-based metal organic compound precursor to obtain a target product. The catalyst prepared by the invention has a one-dimensional material with a large aspect ratio, which is beneficial to shortening an ion/electron diffusion path and improving reaction kinetics; the heterogeneous interface can remarkably promote the transfer of charges from metal to metal oxide, so that more active sites are exposed, the catalytic activity of the catalyst is improved, in addition, the preparation method is low in cost and easy to operate, and the product has good oxygen reduction (ORR) and Oxygen Evolution (OER) electrocatalytic activity and the like in an alkaline electrolyte.

Description

High-efficiency bifunctional oxygen electrocatalyst with heterogeneous structure and heterogeneous metals, and preparation and application thereof
Technical Field
The invention belongs to the technical field of catalysts, and relates to a high-efficiency bifunctional oxygen electrocatalyst with a heterostructure and heterogeneous metals, and preparation and application thereof.
Background
The growing energy demand and the ever-increasing environmental concerns have prompted the development and utilization of clean, renewable energy technologies, such as fuel cells, metal air cells, and electrolyzed water. Among these energy conversion and storage systems, rechargeable zinc-air batteries are receiving increasing attention due to their high theoretical energy density, low cost, environmental protection, high safety, and the like. The discharge and charge processes of zinc-air batteries are driven by Oxygen Reduction Reactions (ORR) and Oxygen Evolution Reactions (OER), respectively. However, ORR and OER react slowly at the air cathode, which greatly hinders their commercial application. Although noble metal based electrocatalysts (Pt/C, RuO)2Etc.) can effectively promote these reactions, but some problems remain, including low precious metal reserves, high prices, poor stability, and susceptibility to small molecules (SO)XCO, etc.) to be inactivated. In addition, these noble metal catalyst materials tend to have a single catalytic performance, so designing nanomaterials with bifunctional ORR/OER catalytic activity is critical to meet practical applications.
The transition metal compound has low price, rich resources and environmental protection, and is a potential substitute. In particular manganese oxide (MnO) having a plurality of three-dimensional electronic structures and various morphologies and phasesx) Materials, have attracted a great deal of attention. MnOxCan effectively assist charge transfer, adsorb oxygen on the surface of the catalyst and promote HO2 -Decomposition of (3). But its poor durability and poor electrical conductivity prevent its wide application in oxygen electrocatalysis processes. The cobalt-based hybrid material has better catalytic activity and alkali resistance, and can remarkably improve the OER performance of the material. Thus MnO is reducedxCombination with Co may be a viable method of making a bifunctional catalyst.
Not only the design of an excellent catalyst needs to be considered, but also the optimization of the structure of the catalyst is important. Recent research shows that the construction of interface engineering can effectively promote electron transfer, and the synergistic effect generated by compounding the interface engineering with a carbon carrier can expose more active sites, thereby enhancing the catalytic activity and stability. However, the metal/metal oxide heterostructures reported so far are mostly based on the same metallic element, since the different metallic components tend to grow separately, eventually resulting in a complete mixture of the different metallic components.
Therefore, how to further optimize the structure and components of the catalyst and improve the stability and catalytic activity of the catalyst is particularly necessary. The present invention has been made in view of the above problems.
Disclosure of Invention
The invention aims to provide a high-efficiency bifunctional oxygen electrocatalyst with heterogeneous structures and heterogeneous metals, and preparation and application thereof.
The purpose of the invention can be realized by the following technical scheme:
one of the technical schemes of the invention provides a high-efficiency dual-function oxygen electrocatalyst with heterogeneous structure and heterogeneous metals, which is formed by coating cobalt/manganese monoxide heterogeneous nano particles with a nitrogen-doped carbon layer.
The second technical scheme of the invention provides a preparation method of a high-efficiency bifunctional oxygen electrocatalyst with heterogeneous structures and dissimilar metals, which comprises the following steps:
(1) dispersing soluble cobalt salt, soluble manganese salt and nitrilotriacetic acid serving as raw materials in a solvent, uniformly mixing, heating for reaction, cooling, centrifuging and drying to obtain a cobalt-manganese-based metal organic compound precursor;
(2) and carrying out pyrolysis treatment on the cobalt-manganese-based metal organic compound precursor to obtain a target product.
Further, in the step (1), the soluble cobalt salt is cobalt chloride, and the soluble manganese salt is manganese chloride.
Further, in the step (1), the solvent used is a mixture of water and isopropanol. Preferably, the volume ratio of water to isopropanol is 7: 1.
Further, in the step (1), the mass ratio of the soluble cobalt salt to the soluble manganese salt is 1: 2-2: 1. Preferably, the mass ratio of nitrilotriacetic acid to total metal salts (i.e., the sum of the mass of soluble cobalt salt and soluble manganese salt) is 2: 3.
Further, in the step (1), the heating reaction temperature is 80-160 ℃, and the time is 2-6 h.
Further, in the step (2), the pyrolysis treatment is carried out under an inert gas protective atmosphere.
Further, in the step (2), the pyrolysis temperature is 650-.
The third technical scheme of the invention provides application of a high-efficiency dual-function oxygen electrocatalyst with a heterostructure and heterogeneous metals, wherein the oxygen electrocatalyst is used for ORR and OER under an alkaline condition.
Further, the oxygen electrocatalyst is used in an alkaline liquid or solid zinc-air battery.
Compared with the prior art, the invention has the following advantages:
(1) a unique chelating agent. Nitrilotriacetic acid (NTA) can form stable complexes with different transition metals under hydrothermal conditions and self-assemble into nanowire structures.
(2) The structure is stable. Conventional simple MOFs would choose high temperature pyrolysis in order to enhance the conductivity of the catalyst, but would typically result in structural collapse. The Co/MnO @ NC catalyst prepared by the invention maintains the structure of the precursor Co/Mn-NTA nanowire, is beneficial to shortening the transmission path of electrons and ions, and improves the reaction kinetics to a certain extent. Importantly, when the nano-wire is used as an air electrode, the nano-wire can form a 3D porous structure, and gas diffusion is facilitated.
(3) And (5) interface construction. The Co/MnO heterostructure constructed by the invention effectively promotes charge transfer, and the interface of the heterostructure can be used as a main catalytic active site to accelerate the dynamics of ORR and OER.
Drawings
FIG. 1-1 is an infrared spectrum of Co-NTA, Mn-NTA and Co/Mn-NTA precursors prepared in example 1 of the present invention;
FIG. 1-2 shows X-ray diffraction (XRD) spectra of Co-NTA, Mn-NTA and Co/Mn-NTA precursors prepared in example 1 of the present invention;
FIGS. 1 to 3 are scanning electron micrographs (SEM, a to f) of Co-NTA, Mn-NTA and Co/Mn-NTA precursors prepared in example 1 of the present invention;
FIG. 2-1 is an X-ray diffraction (XRD) spectrum of catalysts Co @ NC, MnO @ NC and Co/MnO @ NC prepared in example 2 of the present invention;
FIG. 2-2 is a Raman spectrum of the catalyst prepared in example 2 of the present invention;
FIGS. 2-3 are scanning electron micrographs (SEM, a-b) of the Co/MnO @ NC catalyst prepared in example 2 of the present invention;
FIGS. 2-4 are elemental distribution plots of Co/MnO @ NC catalyst prepared in example 2 of the present invention;
FIG. 3-1 is a scanning electron microscope (SEM, a-b) image of comparative example 3 of the present invention without introducing nitrilotriacetic acid;
FIG. 3-2 is a Scanning Electron Microscope (SEM) photograph of comparative example 4 of the present invention incorporating trimesic acid;
FIG. 4-1 shows the Co/MnO @ NC catalyst prepared in example 2 of the present invention and RuO catalyst2Linear sweep voltammogram (a) and corresponding tafel slope plot (b) at 1M potassium hydroxide electrolyte;
FIG. 4-2 is a plot of cyclic voltammograms (a) of the Co/MnO @ NC catalyst prepared in example 2 of the present invention at different sweep rates; (b) the relationship curve of the current density difference of the catalyst at the relative reduction hydrogen potential of 1.05V and different sweep rates is shown;
FIGS. 4-3 are impedance profiles of different electrodes;
FIGS. 4-4 are stability plots for Co/MnO @ NC electrodes;
FIG. 5-1 is a plot of linear sweep voltammogram (a) and corresponding Tafel slope values (b) for the catalyst Co/MnO @ NC prepared in example 2 of the present invention and the commercial catalyst Pt/C (20%) in 0.1M potassium hydroxide electrolyte;
FIG. 5-2 is a plot of linear sweep voltammograms at different rotational speeds and K-L at different potentials for the catalyst Co/MnO @ NC prepared in example 2 of the present invention;
FIGS. 5-3 are dual function LSV curves for different electrodes;
FIG. 6 is a graph of the application of the Co/MnO @ NC catalyst prepared in example 2 of the present invention in a liquid zinc-air cell;
FIG. 7 is a graph of the application of the Co/MnO @ NC catalyst prepared in example 2 of the present invention in a solid state zinc-air cell.
Detailed Description
The invention is described in detail below with reference to the figures and specific embodiments. The present embodiment is implemented on the premise of the technical solution of the present invention, and a detailed implementation manner and a specific operation process are given, but the scope of the present invention is not limited to the following embodiments.
The high efficiency bifunctional oxygen electrocatalyst according to the present invention will be described in detail below.
The invention provides a high-efficiency bifunctional oxygen electrocatalyst with heterogeneous structure heterogeneous metals, which is formed by coating cobalt/manganese monoxide heterogeneous nanoparticles with a nitrogen-doped carbon layer.
The method for preparing the high-efficiency bifunctional oxygen electrocatalyst according to the present invention will be described in detail.
The invention provides a preparation method of a high-efficiency bifunctional oxygen electrocatalyst with heterogeneous structure heterogeneous metals, which comprises the following steps:
(1) dispersing soluble cobalt salt, soluble manganese salt and nitrilotriacetic acid serving as raw materials in a solvent, uniformly mixing, heating for reaction, cooling, centrifuging and drying to obtain a cobalt-manganese-based metal organic compound precursor (namely Co/MnO-NTA);
(2) and carrying out pyrolysis treatment on the cobalt-manganese-based metal organic compound precursor to obtain the target product, namely the high-efficiency bifunctional oxygen electrocatalyst Co/MnO @ NC.
In some embodiments, in step (1), the soluble cobalt salt is cobalt chloride and the soluble manganese salt is manganese chloride.
In some embodiments, in step (1), the solvent used is a mixture of water and isopropanol. Preferably, the volume ratio of water to isopropanol is 7: 1.
In some embodiments, in step (1), the mass ratio of the soluble cobalt salt to the soluble manganese salt is 1:2 to 2: 1. Preferably, the mass ratio of nitrilotriacetic acid to total metal salts is 2: 3.
In some embodiments, in step (1), the temperature of the heating reaction is between 80 and 160 ℃ for 2 to 6 hours.
In some embodiments, in step (2), the pyrolysis treatment is performed under an inert gas atmosphere. Preferably, the pyrolysis treatment is performed in a mixed gas of argon and hydrogen, and more preferably, VAr:VH2＝9:1。
In some embodiments, in step (2), the pyrolysis temperature is 650-.
Specifically, in the preparation process, cobalt chloride, manganese chloride and nitrilotriacetic acid are respectively used as a metal source and a ligand, and the strong binding force of carboxyl functional groups in the nitrilotriacetic acid to metal ions is utilized in the hydrothermal synthesis process to form Co/MnO-NTA, and the Co/MnO-NTA is self-assembled into a nanowire structure. In this step, nitrilotriacetic acid is in excess, ensuring that the metal ions are fully chelated and the yield can be increased. Hydrothermal temperatures above 140 ℃ are required so that nitrilotriacetic acid is effective in chelating metal ions.
Finally, converting the precursor into cobalt/manganese monoxide heterogeneous nanoparticles coated by a nitrogen-doped carbon layer through high-temperature pyrolysis carbonization, wherein the morphology is collapsed due to overhigh carbonization temperature, and the active sites are reduced due to the agglomeration of the nanoparticles; when the temperature is too low, the graphitization degree of the catalyst is not strong, so that the conductivity of the catalyst is poor.
The third technical scheme of the invention provides application of a high-efficiency dual-function oxygen electrocatalyst with a heterostructure and heterogeneous metals, wherein the oxygen electrocatalyst is used for ORR and OER under an alkaline condition.
Further, the oxygen electrocatalyst is used in an alkaline liquid or solid zinc-air battery.
In particular, the one-dimensional nanowire structure with a large aspect ratio in the catalyst of the present invention is advantageous for shortening the ion/electron diffusion path and improving the reaction kinetics. The coating of the graphitized carbon layer enhances the conductivity and stability of the catalyst. The method has low cost and easy operation, and the product has good oxygen reduction (ORR) and Oxygen Evolution (OER) electrocatalytic activity in alkaline electrolyte and has good application in rechargeable zinc-air batteries.
The above embodiments will be described in more detail with reference to specific examples.
In the following examples, potassium hydroxide and isopropanol were obtained from Merlin Biotechnology Inc., Shanghai, and nitrilotriacetic acid, manganese chloride tetrahydrate, and cobalt chloride hexahydrate, from Aladdin reagent, Shanghai, were obtained. The remaining raw material products or processing techniques which are not specifically described are conventional commercial products or conventional processing techniques in the art.
Electrochemical data were collected by CHI760E (shanghai chenhua) and a rotating disk test system.
Example 1:
preparation of precursor Co/Mn-NTA:
(1) weighing cobalt chloride, manganese chloride and nitrilotriacetic acid, and dissolving in a mixed solvent of water and isopropanol. The mass of nitrilotriacetic acid is 1.2g, the mass of cobalt chloride and manganese chloride are both 0.6g, and the volume of water and isopropanol is 35 mL;
(2) and (2) uniformly stirring the solution in the step (1), and then transferring the solution into a polytetrafluoroethylene inner container for solvothermal pretreatment, wherein the reaction temperature is 140 ℃ and the reaction time is 6 hours. And after the reaction is finished, cooling to room temperature, centrifuging to remove impurities, collecting, and finally drying in a vacuum drying oven at 80 ℃ for 10h to obtain the Co/Mn-NTA precursor.
Example 2:
preparation of Co/MnO @ NC bifunctional catalyst:
and carbonizing the Co/Mn-NTA precursor in the embodiment 1 in a hydrogen-argon mixed gas protection environment to obtain the Co/MnO @ NC dual-function oxygen electrocatalyst, wherein the carbonization temperature is 750 ℃, the carbonization time is 3h, and the heating rate is 3 ℃/min.
FIG. 1-1 shows the infrared spectra of ligand NTA and precursor, from which it can be seen that NTA is 3100--1Broad peak between (3042, 2994, 2956 cm)-1) And 1725cm-1The band at (a) is due to the stretching vibration of C-H and C ═ O, respectively. For NTA complex, Co (II) and/or Mn (II) coordinate with NTA and are positioned at 3042, 2988 and 2960cm-1Shifted to 2970 and 2945cm-1. Furthermore, 1725cm-1The peaks disappeared and were found to be 1691, 1657, 1617 and 1588cm-1A broad band consisting of four peaks is shown, further demonstrating the successful coordination of Co (II) and Mn (II) to NTA in Co/Mn-NTA. FIGS. 1-2 are XRD representations of Co/Mn-NAT, showing that it has a very good crystalline form. FIGS. 1 to 3 are SEM images of Co-NTA, Mn-NTA and Co/Mn-NTA, and the precursors thereof all showed one-dimensional linear structures and had smooth surfaces.
FIGS. 2-1 and 2-2 are XRD and Raman plots of the target products Co/MnO @ NC, Co @ NC and MnO @ NC, respectively, and it can be seen that the cobalt simple substance and manganese monoxide coexist in the Co/MnO @ NC, and the cobalt simple substance improves the graphitization degree of the carbon layer.
FIGS. 2-3 and 2-4 are topographical representations of Co/MnO @ NC, which can be seen to preserve the structure of the precursor nanowires, and after carbonization, the nanoparticles are uniformly dispersed on the porous nitrogen-doped carbon nanowires; the elemental profiles of the products of FIGS. 2-4 show that the products are composed primarily of the three elements Co, Mn and O.
Comparative example 1:
compared with the embodiment 1, the method is mostly the same, except that the addition of cobalt chloride is omitted, and a Mn-NTA precursor is correspondingly obtained, and meanwhile, after the carbonization process of the embodiment 2, the catalyst MnO @ NC is obtained.
Comparative example 2:
compared with the embodiment 1, the method is mostly the same, except that the addition of manganese chloride is omitted, a Co-NTA precursor is correspondingly obtained, and meanwhile, after the carbonization process of the embodiment 2, the catalyst Co @ NC is obtained.
Comparative example 3:
compared to example 1, most of them are the same except that the addition of nitrilotriacetic acid is omitted.
Comparative example 4:
compared to example 1, most of them are the same except that nitrilotriacetic acid is changed to the common ligand trimesic acid (BTC).
FIG. 3-1 is a diagram showing the morphology of the target product without introducing nitrilotriacetic acid into the system, from which it can be seen that the nanoparticle stacking is a polymerization of metal salts, and the structure of the nanowire is not present;
FIG. 3-2 is a graphical representation of the target product when replacing nitrilotriacetic acid in the system with a trimesic acid ligand, which presents a bulk structure and also does not form a nanowire structure, so that the introduction of nitrilotriacetic acid is necessary.
Test method for preparing Co/MnO @ NC as bifunctional oxygen electrocatalyst
(1) The final product catalyst obtained in example 2 was taken as OER catalyst: the reaction system is a three-electrode system, the graphite rod is a counter electrode, and mercury/mercury oxide is a reference potential. 5mg of the catalyst is weighed and ultrasonically dispersed in 0.49mL of isopropanol and 10 mu L of 5 wt% Nafion to form a uniform suspension, 5 mu L of the suspension is absorbed by a pipette and dropped on a 5mm clean glassy carbon electrode, and the suspension is naturally dried for standby. The electrolyte used in the test was 1M potassium hydroxide. Before testing, the electrode is activated by 50 cycles of cyclic voltammetry scanning, and the scanning speed of a linear voltammetry curve is 5mV s-1. The electrochemical impedance spectrum measured under different overpotentials ranges from 10khz to 0.1hz, and the amplitude is 5 mV. The stability is measured at 10mA cm by constant current time potential method-2The next 12h of continuous testing. The results of the examples are shown in FIGS. 3-1 to 3-4.
RuO, as shown in FIG. 3-1, compared to commercial catalyst2The synthesized Co/MnO @ NC exhibits a greater current density and a lower overpotential, and the graph b shows the Tafel slopes of the two, from which it can be seen that the Tafel slope value of Co/MnO @ NC is only 53mV dec-1Far below the catalyst RuO2This indicates that the prepared catalyst has an oxygen evolution kinetic rate superior to that of the noble metal RuO2。
Fig. 3-2 is a cyclic voltammogram of the catalyst at different scan rates, and the difference between the oxidation current and the reduction current at 1.05V is selected to be one half of the capacitance current. The scanning speed is used as an abscissa, the capacitance current under different scanning speeds is used as an ordinate,the capacitance current is in direct proportion to the scanning speed, the slope of the straight line is the double-layer capacitance of the material, and the electrochemical active area is in direct proportion to the double-layer capacitance. The capacitance value of an electric double layer of Co/MnO @ NC is 12.3mF cm-2Indicating that it has a large number of oxygen producing active sites.
From fig. 3-3Co/MnO @ NC possessing a minimum semicircular diameter (Rct ═ 18.2 Ω) and a steeper slope, it is demonstrated that it has faster charge transfer rates, lower electrode/electrolyte interface resistance and faster mass diffusion. Figures 3-4 show that this catalyst also has good stability.
(2) The final product catalyst obtained in example 2 was taken as ORR catalyst: the reaction system is a three-electrode system, the graphite rod is a counter electrode, and mercury/mercury oxide is a reference potential. 5mg of the catalyst was dispersed in 0.49mL of isopropanol and 10. mu.L of 5 wt% Nafion by sonication to form a uniform suspension, and 12. mu.L of the suspension was pipetted onto 5mm clean RDE and allowed to dry. The electrolyte used in the test was 0.1M potassium hydroxide. Before testing, the electrode is activated by 50 cycles of cyclic voltammetry scanning, and the scanning speed of a linear voltammetry curve is 5mV s-1。
FIG. 4-1, panel a, shows the linear sweep voltammogram at 1600rpm on a rotating disk electrode for different catalysts, from which it can be seen that the onset and half-wave potentials are relatively similar, and the Tafel slope of panel b, indicates that Co/MnO @ NC has faster ORR reaction kinetics.
FIG. 4-2 shows that the K-L curves at different potentials show a good linear relationship, indicating that the first order reaction kinetics of ORR is consistent with the concentration of dissolved oxygen, and the reaction path of catalytic oxygen reduction is dominated by four electrons.
Figures 4-3 show that the catalyst has good stability. The dual-function linear sweep voltammograms for the different electrodes in fig. 4-4.
Evaluation of Co/MnO @ NC as air electrode of Zinc-air Battery
The air cathode consisted of a hydrophilic carbon paper with a gas diffusion layer on the side facing air and a catalyst layer (1 mg cm loading) on the side facing water-2). Polishing the anodeThe thickness of the zinc sheet is 0.3 mm. With 0.2M Zn (CH)3COO)2+6M KOH mixed solution was used as electrolyte. With a commercial catalyst of 20% Pt/C + RuO2(mass ratio 1:1) as a comparison. Testing the polarization curve of the cell by taking the open-circuit voltage as the initial potential and the scanning speed is 2mV s-1. The current density of the charge-discharge cycle test is 20mA cm-2The interval of 20 minutes of charging and 20 minutes of discharging is one.
The solid zinc-air battery replaces the zinc sheet with zinc deposited by carbon cloth, the electrolyte is PANA, and the test conditions are the same as above.
FIG. 6 is a charge-discharge cycle test of a Co/MnO @ NC catalyst prepared in example 2 of the present invention in a liquid zinc-air cell, a commercial catalyst for comparison. As shown, at a larger constant current density (20mA cm)-2) And the voltage can reach 1.15V after discharging for 600 circles after continuous charging and discharging, which shows that the catalyst has good cycle stability.
FIG. 7 is a charge-discharge cycle test of the Co/MnO @ NC catalyst prepared in different solid electrolytes, as shown in the figure, when the constant current density is set to 5mA cm-2In the process, the catalyst can be circulated for 500 circles under the PANA electrolyte, and is superior to a PVA electrolyte, which shows that the PANA electrolyte has good water-retaining property.
In general, the present invention employs nitrilotriacetic acid as a chelating agent, by which a stable complex can be formed by chelating with most transition metals, and can self-assemble into a nanowire network structure under hydrothermal conditions. After pyrolysis is carried out at a proper temperature, the target product still maintains the nanowire structure of the precursor, and a large amount of cobalt/manganese monoxide heterogeneity appears in the target product by utilizing the difference of conditions required by reduction of metal manganese and cobalt. The interface exposes more active sites, thereby facilitating the catalytic activity of the material.
The embodiments described above are described to facilitate an understanding and use of the invention by those skilled in the art. It will be readily apparent to those skilled in the art that various modifications to these embodiments may be made, and the generic principles described herein may be applied to other embodiments without the use of the inventive faculty. Therefore, the present invention is not limited to the above embodiments, and those skilled in the art should make improvements and modifications within the scope of the present invention based on the disclosure of the present invention.

Claims (10)

1. The high-efficiency bifunctional oxygen electrocatalyst with heterogeneous structure and heterogeneous metals is characterized in that the oxygen electrocatalyst is formed by coating cobalt/manganese monoxide heterogeneous nanoparticles with a nitrogen-doped carbon layer.
2. A method of preparing a bifunctional highly efficient oxygen electrocatalyst with heterostructured heterogeneous metals according to claim 1, comprising the steps of:
(1) dispersing soluble cobalt salt, soluble manganese salt and nitrilotriacetic acid serving as raw materials in a solvent, uniformly mixing, heating for reaction, cooling, centrifuging and drying to obtain a cobalt-manganese-based metal organic compound precursor;
(2) and carrying out pyrolysis treatment on the cobalt-manganese-based metal organic compound precursor to obtain a target product.
3. The method according to claim 2, wherein in the step (1), the soluble cobalt salt is cobalt chloride, and the soluble manganese salt is manganese chloride.
4. The method for preparing a bifunctional oxygen electrocatalyst with high efficiency and heterogeneous metal in heterostructure according to claim 2, wherein in step (1), the solvent is a mixture of water and isopropanol, and the volume ratio of water to isopropanol is 7: 1.
5. The preparation method of the high-efficiency bifunctional oxygen electrocatalyst with heterogeneous structure metals as claimed in claim 2, wherein in the step (1), the mass ratio of the soluble cobalt salt to the soluble manganese salt is 1: 2-2: 1.
6. The method for preparing a bifunctional oxygen electrocatalyst with high efficiency and heterogeneous metal in heterostructure according to claim 2, wherein in step (1), the temperature of the heating reaction is 80-160 ℃ and the time is 2-6 h.
7. The method for preparing a bifunctional oxygen electrocatalyst with heterogeneous structure of heterogeneous metals according to claim 2, wherein in step (2), the pyrolysis treatment is performed under an inert gas atmosphere.
8. The method as claimed in claim 2, wherein the pyrolysis temperature in step (2) is 650-850 ℃ and the pyrolysis time is 1-4 h.
9. Use of a high efficiency bifunctional oxygen electrocatalyst with heterostructural dissimilar metals according to claim 1, characterised in that the oxygen electrocatalyst is used in ORR and OER under basic conditions.
10. Use of a high efficiency bifunctional oxygen electrocatalyst with heterostructural dissimilar metals according to claim 9, characterised in that the oxygen electrocatalyst is used in alkaline liquid or solid zinc-air cells.
CN202110175168.6A 2021-02-07 2021-02-07 High-efficiency bifunctional oxygen electrocatalyst with heterogeneous structure and heterogeneous metals, and preparation and application thereof Pending CN113224325A (en)

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Application publication date: 20210806