CN115475646A - Carbon nanotube-based catalyst and preparation method and application thereof - Google Patents

Carbon nanotube-based catalyst and preparation method and application thereof Download PDF

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CN115475646A
CN115475646A CN202211148796.6A CN202211148796A CN115475646A CN 115475646 A CN115475646 A CN 115475646A CN 202211148796 A CN202211148796 A CN 202211148796A CN 115475646 A CN115475646 A CN 115475646A
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cobalt
iridium
carbon nanotube
based catalyst
nitrogen
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徐成彦
章梦甜
李豪
甄良
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Shenzhen Graduate School Harbin Institute of Technology
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Shenzhen Graduate School Harbin Institute of Technology
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J27/00—Catalysts comprising the elements or compounds of halogens, sulfur, selenium, tellurium, phosphorus or nitrogen; Catalysts comprising carbon compounds
    • B01J27/24—Nitrogen compounds
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J21/00—Catalysts comprising the elements, oxides, or hydroxides of magnesium, boron, aluminium, carbon, silicon, titanium, zirconium, or hafnium
    • B01J21/18—Carbon
    • B01J21/185—Carbon nanotubes
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J23/00—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00
    • B01J23/70—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of the iron group metals or copper
    • B01J23/89—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of the iron group metals or copper combined with noble metals
    • B01J23/8913—Cobalt and noble metals
    • B01J35/23—
    • B01J35/33—
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J37/00—Processes, in general, for preparing catalysts; Processes, in general, for activation of catalysts
    • B01J37/08—Heat treatment
    • B01J37/082—Decomposition and pyrolysis
    • B01J37/086—Decomposition of an organometallic compound, a metal complex or a metal salt of a carboxylic acid
    • C—CHEMISTRY; METALLURGY
    • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
    • C25B—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES FOR THE PRODUCTION OF COMPOUNDS OR NON-METALS; APPARATUS THEREFOR
    • C25B1/00—Electrolytic production of inorganic compounds or non-metals
    • C25B1/01—Products
    • C25B1/02—Hydrogen or oxygen
    • C25B1/04—Hydrogen or oxygen by electrolysis of water
    • C—CHEMISTRY; METALLURGY
    • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
    • C25B—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES FOR THE PRODUCTION OF COMPOUNDS OR NON-METALS; APPARATUS THEREFOR
    • C25B11/00—Electrodes; Manufacture thereof not otherwise provided for
    • C25B11/04—Electrodes; Manufacture thereof not otherwise provided for characterised by the material
    • C25B11/051—Electrodes formed of electrocatalysts on a substrate or carrier
    • C25B11/073—Electrodes formed of electrocatalysts on a substrate or carrier characterised by the electrocatalyst material
    • C25B11/091—Electrodes formed of electrocatalysts on a substrate or carrier characterised by the electrocatalyst material consisting of at least one catalytic element and at least one catalytic compound; consisting of two or more catalytic elements or catalytic compounds
    • C25B11/093—Electrodes formed of electrocatalysts on a substrate or carrier characterised by the electrocatalyst material consisting of at least one catalytic element and at least one catalytic compound; consisting of two or more catalytic elements or catalytic compounds at least one noble metal or noble metal oxide and at least one non-noble metal oxide
    • 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
    • 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
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/30—Hydrogen technology
    • Y02E60/36—Hydrogen production from non-carbon containing sources, e.g. by water electrolysis

Abstract

The invention relates to the technical field of electrochemical catalysis, in particular to a carbon nanotube-based catalyst and a preparation method and application thereof. The invention provides a carbon nanotube-based catalyst, which comprises a nitrogen-doped carbon nanotube and iridium-cobalt nanoparticles loaded in the nitrogen-doped carbon nanotube, wherein the iridium-cobalt nanoparticles are iridium-doped cobalt nanoparticles. In the catalyst, the iridium-cobalt nanoparticles are loaded in the nitrogen-doped carbon nanotube, so that rapid electron transfer can be realized, the dissolution and agglomeration of the nanoparticles are effectively inhibited, the conductivity is improved, and the active sites of catalytic reaction are protected; in addition, ir and Co have stronger electronic coupling effect, which is beneficial to improving the electrocatalytic performance of the catalyst; meanwhile, the catalyst shows excellent electrocatalytic hydrogen evolution performance in both acidic and alkaline media, and has higher activity and good stability.

Description

Carbon nanotube-based catalyst and preparation method and application thereof
Technical Field
The invention relates to the technical field of electrochemical catalysis, in particular to a carbon nanotube-based catalyst and a preparation method and application thereof.
Background
Due to the high energy storage density and zero carbon nature of hydrogen, it has been considered the most desirable energy carrier for fossil fuels. The cathodic Hydrogen Evolution Reaction (HER) of electrolysis of water is a promising method for large-scale production of high-purity hydrogen. To date, platinum (Pt) is considered to be the most effective HER electrocatalyst with negligible overpotential and excellent kinetics. However, the natural scarcity and expensive price of platinum severely hamper its widespread use. Although a large number of crystallites have been invested in the development of transition metal catalysts, the intrinsic electrocatalytic activity is still lower than that of Pt-based catalysts.
Disclosure of Invention
The invention aims to provide a carbon nanotube-based catalyst, and a preparation method and application thereof.
In order to achieve the above object, the present invention provides the following technical solutions:
the invention provides a carbon nano tube based catalyst which comprises a nitrogen-doped carbon nano tube and iridium-cobalt nano particles loaded in the nitrogen-doped carbon nano tube, wherein the iridium-cobalt nano particles are iridium-doped cobalt nano particles.
Preferably, the mass ratio of the iridium-cobalt nanoparticles to the nitrogen-doped carbon nanotubes is 1: (1-3).
Preferably, the iridium-cobalt nanoparticles have a mass ratio of iridium to cobalt of 1: (10 to 40).
Preferably, the particle size of the iridium-cobalt nanoparticles is 10-20 nm;
the nitrogen doping amount of the nitrogen-doped carbon nano tube is 1-10 wt%, the diameter is 10-20 nm, and the length-diameter ratio is 1: (50-150).
The invention also provides a preparation method of the catalyst in the technical scheme, which comprises the following steps:
firstly mixing a cobalt salt solution and a 2-methylimidazole solution, and complexing to obtain cobalt MOFs;
secondly mixing the cobalt MOFs, iridium salt and a polar solvent, and performing iridium ion adsorption to obtain iridium-adsorbed cobalt MOFs;
and thirdly, mixing the iridium-adsorbed cobalt MOFs and an organic nitrogen source, and then carrying out pyrolysis treatment to obtain the carbon nanotube-based catalyst.
Preferably, the cobalt salt in the cobalt salt solution comprises one or more of cobalt sulfate, cobalt chloride, cobalt nitrate and cobalt acetate;
the molar ratio of the cobalt salt in the cobalt salt solution to the 2-methylimidazole in the 2-methylimidazole solution is 1: (1-8).
Preferably, the iridium salt comprises one or more of iridium trichloride, iridium acetate, iridium acetylacetonate and iridium tetrachloride;
the polar solvent comprises one or more of absolute ethyl alcohol, methanol and water;
the mass ratio of the iridium salt to the cobalt MOFs is 1: (5-20).
Preferably, the organic nitrogen source comprises one or more of dicyandiamide, urea and melamine;
the mass ratio of the cobalt MOFs for adsorbing iridium to the organic nitrogen source is 1: (25 to 100).
Preferably, the pyrolysis treatment is carried out in a protective atmosphere;
the temperature of the pyrolysis treatment is 800-1000 ℃, and the heat preservation time is 2-4 h; the heating rate of heating to the temperature of the pyrolysis treatment is 1-3 ℃/min.
The invention also provides the application of the catalyst in the technical scheme or the catalyst prepared by the preparation method in the technical scheme in water electrolysis hydrogen evolution reaction or a fuel cell.
The invention provides a carbon nanotube-based catalyst, which comprises a nitrogen-doped carbon nanotube and iridium-cobalt nanoparticles loaded in the nitrogen-doped carbon nanotube, wherein the iridium-cobalt nanoparticles are iridium-doped cobalt nanoparticles. Since the efficiency of the cathodic hydrogen evolution reaction is closely related to the strength of the metal-hydrogen bonds on the catalyst surface, hydrogen reduction is allowed at lower overpotentials. Iridium (Ir) at the center of the volcano plot of HER with Gibbs free energy Δ G H (Ir-H: 0.03 eV) is very close to Pt (Pt-H: 0.09 eV), and has high HER activity. In the catalyst, the iridium-cobalt nanoparticles are loaded in the nitrogen-doped carbon nanotube, so that rapid electron transfer can be realized, the dissolution and agglomeration of the iridium-cobalt nanoparticles are effectively inhibited, the conductivity is favorably improved, and the active sites of catalytic reaction are protected; in addition, ir and Co have stronger electronic coupling effect, which is favorable for improving the electrocatalysis performance of the catalyst; meanwhile, the catalyst shows excellent electrocatalytic hydrogen evolution performance in both acidic and alkaline media, and has higher activity and good electrochemical stability.
The invention also provides a preparation method of the carbon nanotube-based catalyst in the technical scheme, which comprises the following steps: firstly mixing a cobalt salt solution and a 2-methylimidazole solution, and complexing to obtain cobalt MOFs; secondly, mixing the cobalt MOFs, iridium salt and a polar solvent, and carrying out iridium ion adsorption to obtain iridium-adsorbed cobalt MOFs; and thirdly, mixing the iridium-adsorbed cobalt MOFs and an organic nitrogen source, and then carrying out pyrolysis treatment to obtain the carbon nanotube-based catalyst. The preparation method firstly synthesizes cobalt MOFs, and then mixes the cobalt MOFs with iridium salt to realize iridium ion adsorption; and then mixing with an organic nitrogen source, and carrying out pyrolysis treatment to obtain the catalyst. The raw materials adopted in the preparation method are all cheap industrial raw materials, and compared with a commercial Pt/C catalyst, the precious metal Ir used in the method has low consumption and obvious cost advantage; the preparation method is simple and easy to implement, low in energy consumption and suitable for industrial application. Meanwhile, the preparation method of the invention takes the cobalt MOFs as a carbon source, which not only can protect metal particles from being aggregated and leached, but also can successfully prepare the carbon nano tube with porous characteristic, thereby providing active sites for electrocatalytic reaction and better improving the electrocatalytic performance of the catalyst.
Drawings
FIG. 1 is an X-ray diffraction pattern of a carbon nanotube-based catalyst as described in example 1 and comparative example 1;
FIG. 2 is an SEM picture of the IrCo @ NCNTs catalyst described in example 1;
FIG. 3 is a TEM image of the IrCo @ NCNTs catalyst described in example 1;
FIG. 4 is an elemental distribution plot of the IrCo @ NCNTs catalyst described in example 1;
FIG. 5 shows the carbon nanotube-based catalyst of example 1 at 0.5M H 2 SO 4 And hydrogen evolution polarization curve in 1.0M KOH electrolyte;
FIG. 6 shows the IrCo @ NCNTs catalyst prepared in example 1 at 0.5M H 2 SO 4 And current-time response curves in 1.0M KOH electrolyte;
FIG. 7 is a flow Al-H assembled with IrCo @ NCNTs and commercial Pt/C catalyst as cathode catalysts prepared in example 1 2 Linear voltammetry and power density curves for O hybrid cells;
FIG. 8 is a flow Al-H assembled with IrCo @ NCNTs and commercial Pt/C catalyst as cathode catalysts prepared in example 1 2 Discharge voltage curve of O hybrid cells.
Detailed Description
The invention provides a carbon nanotube-based catalyst, which comprises a nitrogen-doped carbon nanotube and iridium-cobalt nanoparticles loaded in the nitrogen-doped carbon nanotube, wherein the iridium-cobalt nanoparticles are iridium-doped cobalt nanoparticles.
In the present invention, the mass ratio of the iridium-cobalt nanoparticles to the nitrogen-doped carbon nanotubes is preferably 1: (1 to 3), more preferably 1: (1-2), most preferably 1:1.5.
in the present invention, the iridium-cobalt nanoparticle preferably has an iridium to cobalt mass ratio of 1: (10 to 40), more preferably 1: (15 to 30), most preferably 1:20.
in the present invention, the iridium-cobalt nanoparticles preferably have a particle size of 10 to 20nm; the diameter of the nitrogen-doped carbon nanotube is preferably 10-20 nm, and the length-diameter ratio is preferably 1: (50-150). In the present invention, the nitrogen doping amount in the nitrogen-doped carbon nanotube is preferably 1 to 10wt%, more preferably 2 to 8wt%, and most preferably 4 to 6wt%.
The invention also provides a preparation method of the carbon nanotube-based catalyst in the technical scheme, which comprises the following steps:
firstly mixing a cobalt salt solution and a 2-methylimidazole solution, and complexing to obtain cobalt MOFs;
secondly, mixing the cobalt MOFs, iridium salt and a polar solvent, and carrying out iridium ion adsorption to obtain iridium-adsorbed cobalt MOFs;
and thirdly, mixing the iridium-adsorbed cobalt MOFs and an organic nitrogen source, and then carrying out pyrolysis treatment to obtain the carbon nanotube-based catalyst.
In the present invention, all the starting materials for the preparation are commercially available products known to those skilled in the art unless otherwise specified.
According to the invention, a cobalt salt solution and a 2-methylimidazole solution are firstly mixed and complexed to obtain the cobalt MOFs.
In the present invention, the concentration of the cobalt salt solution is preferably 0.1 to 0.3mol/L, more preferably 0.1 to 0.2mol/L, and most preferably 0.15mol/L. In the invention, the cobalt salt in the cobalt salt solution preferably comprises one or more of cobalt sulfate, cobalt chloride, cobalt nitrate and cobalt acetate; more preferably cobalt nitrate in the presence of water; when the cobalt salts are more than two of the specific choices, the invention does not have any special limitation on the proportion of the specific substances, and the specific substances are mixed according to any proportion. In the present invention, the solvent in the cobalt salt solution preferably includes methanol and ethanol; the volume ratio of the methanol to the ethanol is preferably (1-5): 1, more preferably (2 to 4): 1, most preferably 3:1. the preparation process of the cobalt salt solution is not limited in any way, and can be carried out by adopting a process well known to a person skilled in the art.
In the present invention, the concentration of the 2-methylimidazole solution is preferably 0.3 to 0.8mol/L, more preferably 0.4 to 0.6mol/L, and most preferably 0.5mol/L. In the present invention, the solvent in the 2-methylimidazole solution preferably includes methanol and ethanol; the volume ratio of the methanol to the ethanol is preferably (1-5): 1, more preferably (2 to 4): 1, most preferably 3:1. the preparation process of the 2-methylimidazole solution is not limited in any way, and can be carried out by adopting a process well known to a person skilled in the art.
In the present invention, the molar ratio of the cobalt salt in the cobalt salt solution to the 2-methylimidazole in the 2-methylimidazole solution is preferably 1: (1 to 8), more preferably 1: (2 to 7), most preferably 1: (3-5).
In the present invention, the first mixing is preferably performed by adding a cobalt salt solution to the 2-methylimidazole solution and stirring; the method for adding the cobalt salt solution is not limited in any way, and the method can be carried out by adopting a process well known to a person skilled in the art. In the present invention, the stirring time is preferably 1 to 6 hours, more preferably 2 to 4 hours, and most preferably 2 hours; the rotation speed of the stirring is not limited in any way in the present invention, and may be any rotation speed known to those skilled in the art.
After the first mixing is completed, the present invention also preferably includes standing, centrifugal washing and drying, which are sequentially performed. In the present invention, the time for the standing is preferably 12 to 36 hours, more preferably 12 to 30 hours, and most preferably 24 hours. The process of the centrifugal washing is not particularly limited, and may be performed by a process known to those skilled in the art. In the present invention, the number of times of the centrifugal washing is preferably 1 or more, and more preferably 3 or more. In the present invention, the drying is preferably vacuum drying, and the time of the vacuum drying is preferably 8 to 24 hours, more preferably 10 to 16 hours, and most preferably 12 hours; the temperature of the vacuum drying is not limited in any way in the present invention, and the product reaches a constant weight within the above time period by using a temperature well known to those skilled in the art.
After obtaining the cobalt MOFs, secondly mixing the cobalt MOFs, iridium salt and a polar solvent, and carrying out iridium ion adsorption to obtain the iridium-adsorbed cobalt MOFs.
In the invention, the iridium salt preferably comprises one or more of iridium trichloride, iridium acetate, iridium acetylacetonate and iridium tetrachloride; more preferably iridium chloride trihydrate; when the iridium salt is more than two of the specific choices, the specific proportion of the specific substances is not limited in any way, and the iridium salt can be mixed according to any proportion.
In the present invention, the polar solvent preferably includes one or more of absolute ethanol, methanol and water; when the polar solvent is more than two of the above specific choices, the invention does not have any special limitation on the proportion of the specific substances, and the specific substances can be mixed according to any proportion.
In the present invention, the mass ratio of iridium salt to cobalt MOFs is preferably 1: (5 to 20), more preferably 1: (8 to 15), most preferably 1:10.
in the present invention, the mass ratio of the cobalt MOFs to the polar solvent is preferably 1: (200 to 800), more preferably 1: (400-600), most preferably 1:500.
in the invention, the second mixing is preferably to mix the cobalt MOFs and part of polar solvent to obtain a cobalt MOFs solution; mixing the iridium salt and the residual polar solvent to obtain an iridium salt solution; and dropwise adding the iridium salt solution into the cobalt MOFs solution. The proportion of the partial polar solvent and the residual polar solvent is not limited in any way, as long as the cobalt MOFs and the iridium salt can be uniformly dispersed. The dropping process is not particularly limited, and may be carried out by a process known to those skilled in the art.
In the invention, the iridium ion adsorption preferably comprises ultrasonic treatment and stirring which are sequentially carried out, wherein the ultrasonic treatment time is preferably 0.5-3 h, more preferably 1.0-2 h, and most preferably 1.5h; the stirring time is preferably 4 to 12 hours, more preferably 6 to 10 hours, and most preferably 7 to 9 hours. The present invention does not have any particular limitation on the speed of the ultrasound and the stirring, and the speed is known to those skilled in the art.
After the iridium ion adsorption is finished, the method also preferably comprises the steps of centrifuging, washing and drying in sequence; the present invention does not have any particular limitation in the centrifugation, washing and drying, and may be carried out by a process well known to those skilled in the art.
After obtaining the cobalt MOFs adsorbing iridium, the cobalt MOFs adsorbing iridium and an organic nitrogen source are mixed for the third time and then are subjected to pyrolysis treatment, so that the carbon nanotube-based catalyst is obtained.
In the present invention, the organic nitrogen source preferably comprises one or more of dicyandiamide, urea and melamine; when the organic nitrogen source is more than two of the above specific choices, the invention has no special limitation on the proportion of the specific substances, and the specific substances are mixed according to any proportion.
In the present invention, the mass ratio of the iridium-adsorbing cobalt MOFs to the organic nitrogen source is preferably 1: (25 to 100), more preferably 1: (30 to 90), most preferably 1: (50-60).
In the present invention, the third mixing is preferably performed under a milling condition, and the milling process is not particularly limited in the present invention, and may be performed by a process well known to those skilled in the art.
In the present invention, the pyrolysis treatment is preferably performed in a protective atmosphere, which is preferably a nitrogen atmosphere or an argon atmosphere. In the invention, the temperature of the pyrolysis treatment is preferably 800-1000 ℃, more preferably 850-950 ℃, and most preferably 880-920 ℃; the time is preferably 2 to 4 hours, more preferably 2.5 to 3.5 hours, and most preferably 2.8 to 3.2 hours; the rate of temperature rise to the temperature of the pyrolysis treatment is preferably 1 to 3 ℃/min, more preferably 1.5 to 2.5 ℃/min, and most preferably 1.8 to 2.2 ℃/min. In the present invention, the pyrolysis treatment is preferably carried out in a tube furnace.
After the pyrolysis treatment is finished, the method also preferably comprises the steps of acid washing, water washing, suction filtration and drying which are sequentially carried out. In the invention, the pickling solution used for pickling is preferably dilute hydrochloric acid with the concentration of 0.5 mol/L; the pickling is preferably carried out in a soaking mode; the process of soaking is not limited in any way, and can be carried out by a process known to those skilled in the art. In the present invention, the purpose of the acid wash is to remove unstable metal particles. The process of the water washing is not limited in any way by the present invention, and the process known to those skilled in the art is adopted and the residual hydrochloric acid can be removed completely. The process of the suction filtration is not limited in any way, and can be carried out by a process known to those skilled in the art. In the present invention, the drying method is preferably vacuum drying; the vacuum drying process is not particularly limited, and may be performed by a method known to those skilled in the art. In the embodiment of the invention, the temperature of the vacuum drying is 60 ℃ and the time is 12h.
The invention also provides the application of the catalyst in the technical scheme or the catalyst prepared by the preparation method in the technical scheme in the electrolytic water hydrogen evolution reaction and a fuel cell. The method of the present invention is not particularly limited, and the method may be performed by a method known to those skilled in the art.
The catalyst and the preparation and use thereof provided by the present invention are described in detail below with reference to examples, but they should not be construed as limiting the scope of the present invention.
Example 1
Mixing 1.746g of cobalt nitrate hexahydrate, 30mL of methanol and 10mL of absolute ethyl alcohol to obtain a cobalt nitrate solution;
mixing 1.97g of dimethyl imidazole, 30mL of methanol and 10mL of absolute ethanol to obtain a dimethyl imidazole solution;
adding the cobalt nitrate solution into the dimethyl imidazole solution, stirring at room temperature for 2 hours, standing for 24 hours, centrifugally washing for 3 times, and vacuum-drying for 12 hours to obtain purple powder;
mixing 0.1g of purple powder with 50mL of ethanol, dropwise adding 2mL of 10mg/mL iridium chloride trihydrate solution, performing ultrasonic treatment for 0.5h, stirring for 12h, performing centrifugal washing for 3 times, and performing vacuum drying for 12h to obtain a powder substance;
mixing and grinding 0.02g of the powder substance and 1g of dicyandiamide for 0.5h, placing the mixture in a tube furnace, heating the mixture to 900 ℃ at the heating rate of 3 ℃/min in the argon atmosphere for pyrolysis treatment for 3h, cooling the mixture to room temperature, taking out a product, placing the product in 0.5mol/L diluted hydrochloric acid for soaking for 5h to remove unstable metal particles, and repeatedly cleaning the product by using deionized water to remove hydrochloric acid; and finally, carrying out vacuum drying on the product at 60 ℃ for 12h to obtain a carbon nanotube-based catalyst, wherein IrCo @ NCNTs is recorded (the mass ratio of the iridium-cobalt nanoparticles to the nitrogen-doped carbon nanotube is 1.5, the mass ratio of iridium to cobalt in the iridium-cobalt nanoparticles is 1.
Example 2
Mixing 1.746g of cobalt nitrate hexahydrate, 30mL of methanol and 10mL of absolute ethyl alcohol to obtain a cobalt nitrate solution;
mixing 1.97g of dimethyl imidazole, 30mL of methanol and 10mL of absolute ethanol to obtain a dimethyl imidazole solution;
adding the cobalt nitrate solution into the dimethyl imidazole solution, stirring at room temperature for 2 hours, standing for 24 hours, centrifugally washing for 3 times, and vacuum-drying for 12 hours to obtain purple powder;
mixing 0.1g of purple powder with 50mL of ethanol, dropwise adding 1mL of 10mg/mL iridium chloride trihydrate, performing ultrasonic treatment for 0.5h, stirring for 12h, performing centrifugal washing for 3 times, and performing vacuum drying for 12h to obtain a powder substance;
mixing and grinding 0.02g of the powder substance and 1g of dicyandiamide for 0.5h, placing the mixture in a tube furnace, heating the mixture to 900 ℃ at the heating rate of 3 ℃/min in the argon atmosphere for pyrolysis treatment for 3h, cooling the mixture to room temperature, taking out a product, placing the product in 0.5mol/L diluted hydrochloric acid for soaking for 5h to remove unstable metal particles, and repeatedly cleaning the product by using deionized water to remove hydrochloric acid; and finally, carrying out vacuum drying on the product at 60 ℃ for 12h to obtain the carbon nano tube based catalyst (the mass ratio of the iridium-cobalt nano particles to the nitrogen-doped carbon nano tube is 1.
Example 3
Mixing 1.746g of cobalt nitrate hexahydrate, 30mL of methanol and 10mL of absolute ethyl alcohol to obtain a cobalt nitrate solution;
mixing 1.97g of dimethyl imidazole, 30mL of methanol and 10mL of absolute ethanol to obtain a dimethyl imidazole solution;
adding the cobalt nitrate solution into the dimethyl imidazole solution, stirring at room temperature for 2 hours, standing for 24 hours, centrifugally washing for 3 times, and vacuum-drying for 12 hours to obtain purple powder;
mixing 0.1g of purple powder with 50mL of ethanol, dropwise adding 4mL of iridium chloride trihydrate with the concentration of 10mg/mL, performing ultrasonic treatment for 0.5h, stirring for 12h, performing centrifugal washing for 3 times, and performing vacuum drying for 12h to obtain a powder substance;
mixing and grinding 0.02g of the powder substance and 1g of dicyandiamide for 0.5h, placing the mixture in a tube furnace, heating the mixture to 900 ℃ at the heating rate of 3 ℃/min in the argon atmosphere for pyrolysis treatment for 3h, cooling the mixture to room temperature, taking out a product, placing the product in 0.5mol/L diluted hydrochloric acid for soaking for 5h to remove unstable metal particles, and repeatedly cleaning the product by using deionized water to remove hydrochloric acid; and finally, carrying out vacuum drying on the product at 60 ℃ for 12h to obtain the carbon nano tube based catalyst (the mass ratio of the iridium-cobalt nano particles to the nitrogen-doped carbon nano tube is 1.
Comparative example 1
Mixing 1.746g of cobalt nitrate hexahydrate, 30mL of methanol and 10mL of absolute ethyl alcohol to obtain a cobalt nitrate solution;
mixing 1.97g of dimethyl imidazole, 30mL of methanol and 10mL of absolute ethanol to obtain a dimethyl imidazole solution;
adding the cobalt nitrate solution into the dimethyl imidazole solution, stirring at room temperature for 2 hours, standing for 24 hours, centrifugally washing for 3 times, and drying in vacuum for 12 hours to obtain purple powder;
mixing and grinding 0.02g of the purple powder and 1g of dicyandiamide for 0.5h, placing the mixture in a tube furnace, heating the mixture to 900 ℃ at a heating rate of 3 ℃/min in an argon atmosphere for pyrolysis treatment for 3h, cooling the mixture to room temperature, taking out a product, placing the product in 0.5mol/L dilute hydrochloric acid for soaking for 5h to remove unstable metal particles, and repeatedly cleaning the product by using deionized water to remove hydrochloric acid; and finally, carrying out vacuum drying on the product at 60 ℃ for 12h to obtain the carbon nanotube-based catalyst, wherein the catalyst is marked as Co @ NCNTs (the mass ratio of cobalt to nitrogen-doped carbon nanotubes is 1.6, the particle size of the cobalt is 10-20 nm, the diameter of the nitrogen-doped carbon nanotube is 10-20 nm, the length-diameter ratio is 1 (80-120), and the nitrogen doping amount in the nitrogen-doped carbon nanotube is 6.9 wt%).
Test example
FIG. 1 is an X-ray diffraction pattern of the catalysts described in example 1 and comparative example 1, and it can be seen that IrCo @ NCNTs and Co @ NCNTs have diffraction peaks at 44.2 °, 51.5 ° and 75.6 ° corresponding to the (001), (100) and (102) crystal planes of metallic Co (JCPDS No. 15-0806), respectively. The peak at 25.8 ° corresponds to the (002) crystal plane of the high temperature derivatized graphitic carbon. And the XRD pattern diffraction peak position of IrCo @ NCNTs shows a positive shift with respect to Co @ NCNTs due to the atomic radius of metallic Ir
Figure BDA0003854820170000101
Greater than the atomic radius of Co
Figure BDA0003854820170000102
Successful doping of Ir changes the lattice spacing of metallic Co.
FIG. 2 and FIG. 3 are the morphology diagrams of IrCo @ NCNTs catalyst described in example 1, and it can be seen that IrCo nanoparticles are encapsulated in bamboo-like carbon nanotubes with a diameter range of 10-20 nm;
FIG. 4 is an elemental distribution plot of the IrCo @ NCNTs catalyst described in example 1, demonstrating that the C, N elements are uniformly distributed in the carbon matrix and the Ir, co elements are clustered on the nanoparticles.
FIG. 5 shows the catalyst of example 1 at 0.5M H 2 SO 4 And hydrogen evolution polarization curve in 1.0M KOH electrolyte. The test conditions were a scan speed of 5 mV/s. IrCo @ NCNTs catalyst prepared in example 1 at 10mA/cm 2 At a current density of 0.037 overpotential in acidic and alkaline media, respectivelyV,0.027V, can be compared with the over potential value of 0.036V,0.033V of the commercial Pt/C catalyst, and has excellent hydrogen evolution catalytic performance. In contrast, in comparative example 1, the precursor powder does not incorporate metallic Ir, and thus shows poor hydrogen evolution performance in both acidic and alkaline media. Therefore, the excellent hydrogen evolution performance of the IrCo @ NCNTs catalyst may be derived from the strong electron coupling effect of Ir and Co.
FIG. 6 shows the IrCo @ NCNTs catalyst prepared in example 1 at 0.5M H 2 SO 4 And current-time response curves in 1.0M KOH electrolyte; in an acid medium, the hydrogen evolution reaction lasts for more than 24 hours, and the current density is kept at 15mA/cm 2 And almost no attenuation. In an alkaline medium, the hydrogen evolution reaction lasts for more than 12 hours, and the current density is kept at 10mA/cm 2 Without significant attenuation, it can be seen that the IrCo @ NCNTs catalyst has good stability in both acidic and basic media.
FIGS. 7 and 8 are flowing Al-H assembled by IrCo @ NCNTs and commercial Pt/C catalyst prepared in example 1 as cathode catalyst 2 O hybrid battery, linear volt-ampere curve, power density curve and discharge voltage curve obtained by testing; the flowing Al-H 2 The O hybrid cell uses aluminum as an anode, irCo @ NCNTs and commercial Pt/C catalyst as cathode catalysts, electrolyte in an anode chamber is 4.0M NaOH, and electrolyte in a cathode chamber is 2.0M H 2 SO 4 The anode chamber and the cathode chamber are separated by a bipolar membrane. The curve shows that the IrCo @ NCNTs catalyst prepared by the method is in flowing Al-H 2 The power density of the O hybrid battery in an assembly test is slightly superior to that of Pt/C, which shows the potential application value of the O hybrid battery in the field of fuel cells.
In conclusion, the invention provides a preparation method and application of a nitrogen-doped carbon nanotube supported iridium-cobalt catalyst. The preparation method of the nitrogen-doped carbon nanotube supported iridium-cobalt catalyst adopts cheap industrial raw materials of cobalt nitrate, dimethyl imidazole and dicyandiamide; compared with a commercial Pt/C catalyst, the method has the advantages that the using amount of the noble metal Ir is low, and the cost advantage is obvious; the preparation method is simple and easy to implement, low in energy consumption and suitable for industrial application. In the prepared nitrogen-doped carbon nanotube supported iridium-cobalt catalyst, irCo nanoparticles are encapsulated in the carbon nanotube which grows in situ, so that rapid electron transfer can be realized, the dissolution and agglomeration of the nanoparticles are effectively inhibited, the conductivity is favorably improved, and the active sites of catalytic reaction are protected. In addition, the metal Ir and the metal Co have stronger electronic coupling effect, which is beneficial to improving the electrocatalytic performance of the catalyst; the product nitrogen-doped carbon nanotube supported iridium-cobalt catalyst shows excellent electrocatalytic hydrogen evolution performance in acidic and alkaline media, is comparable to the performance of commercial Pt/C, and has higher activity and good stability; in addition, the catalyst can be applied to electrolytic water electrolysis cells and fuel cells.
The foregoing is only a preferred embodiment of the present invention, and it should be noted that, for those skilled in the art, various modifications and amendments can be made without departing from the principle of the present invention, and these modifications and amendments should also be considered as the protection scope of the present invention.

Claims (10)

1. The carbon nanotube-based catalyst is characterized by comprising a nitrogen-doped carbon nanotube and iridium-cobalt nanoparticles loaded in the nitrogen-doped carbon nanotube, wherein the iridium-cobalt nanoparticles are iridium-doped cobalt nanoparticles.
2. The carbon nanotube-based catalyst of claim 1, wherein the iridium-cobalt nanoparticles to nitrogen-doped carbon nanotubes mass ratio is 1: (1-3).
3. The carbon nanotube-based catalyst according to claim 1 or 2, wherein the iridium and cobalt in the iridium-cobalt nanoparticles are present in a mass ratio of 1: (10 to 40).
4. The carbon nanotube-based catalyst according to claim 3, wherein the iridium-cobalt nanoparticles have a particle size of 10 to 20nm;
the nitrogen doping amount of the nitrogen-doped carbon nano tube is 1-10 wt%, the diameter is 10-20 nm, and the length-diameter ratio is 1: (50-150).
5. The method for preparing the carbon nanotube-based catalyst according to any one of claims 1 to 4, comprising the steps of:
firstly mixing a cobalt salt solution and a 2-methylimidazole solution, and complexing to obtain cobalt MOFs;
secondly, mixing the cobalt MOFs, iridium salt and a polar solvent, and carrying out iridium ion adsorption to obtain iridium-adsorbed cobalt MOFs;
and thirdly, mixing the iridium-adsorbed cobalt MOFs and an organic nitrogen source, and then carrying out pyrolysis treatment to obtain the carbon nanotube-based catalyst.
6. The preparation method of claim 5, wherein the cobalt salt in the cobalt salt solution comprises one or more of cobalt sulfate, cobalt chloride, cobalt nitrate and cobalt acetate;
the molar ratio of the cobalt salt in the cobalt salt solution to the 2-methylimidazole in the 2-methylimidazole solution is 1: (1-8).
7. The production method according to claim 5, wherein the iridium salt comprises one or more of iridium trichloride, iridium acetate, iridium acetylacetonate, and iridium tetrachloride;
the polar solvent comprises one or more of absolute ethyl alcohol, methanol and water;
the mass ratio of iridium salt to cobalt MOFs is 1: (5-20).
8. The method according to claim 5, wherein the organic nitrogen source comprises one or more of dicyandiamide, urea and melamine;
the mass ratio of the cobalt MOFs for adsorbing iridium to the organic nitrogen source is 1: (25 to 100).
9. The method of claim 5, wherein the pyrolysis treatment is performed in a protective atmosphere;
the temperature of the pyrolysis treatment is 800-1000 ℃, and the heat preservation time is 2-4 h; the heating rate of heating to the temperature of the pyrolysis treatment is 1-3 ℃/min.
10. Use of the carbon nanotube-based catalyst according to any one of claims 1 to 4 or the carbon nanotube-based catalyst prepared by the preparation method according to any one of claims 5 to 9 in an electrolytic water hydrogen evolution reaction or a fuel cell.
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