CN114232009A

CN114232009A - A bimetallic MOF-derived catalyst and its preparation method and application

Info

Publication number: CN114232009A
Application number: CN202111412381.0A
Authority: CN
Inventors: 王新中; 冯立纲; 胡广志
Original assignee: Shenzhen Institute of Information Technology
Current assignee: Shenzhen Institute of Information Technology
Priority date: 2021-11-25
Filing date: 2021-11-25
Publication date: 2022-03-25
Anticipated expiration: 2041-11-25
Also published as: CN114232009B

Abstract

The application belongs to the technical field of catalyst preparation, and particularly relates to a bimetallic MOF (metal organic framework) derived catalyst and a preparation method and application thereof. The application provides a catalyst surface adheres to there is loose nitrogen-doped carbon nanotube, has greatly improved the electric conductivity of catalyst, the metal fluoride of dispersion between the nanometer alloy base member, the polarity of catalyst has been improved, the maximize exposes active site, nanometer alloy base member forms porous frame structure with nitrogen-doped carbon nanotube complex, stable in structure can prevent metal nanoparticle reunion, realize with the abundant contact of electrolyte, the catalytic activity of catalyst has been improved greatly.

Description

Bimetallic MOF derived catalyst and preparation method and application thereof

Technical Field

The application belongs to the technical field of catalyst preparation, and particularly relates to a bimetallic MOF derived catalyst, and a preparation method and application thereof.

Background

The green electrolytic water is a promising technology for preparing hydrogen by electrolysis, and can efficiently realize the conversion of electric energy into chemical energy. The method comprises two upper electrode reactions, namely a cathode hydrogen evolution reaction and an anode oxygen evolution reaction, but the anode oxygen evolution reaction is relatively complex and has high overpotential, and a large amount of electric energy is consumed. The existing noble metals iridium and ruthenium oxide have the problems of high cost, less resources and the like, limit the large-scale application of the noble metals, and are difficult to be applied in the future hydrogen energy economy field. Therefore, the development of low-cost, high-activity, and abundant-resource transition metal-based catalysts is needed to promote green electrolysis technology.

In the existing oxygen evolution electrocatalyst, under the condition of alkaline electrolyte, the iron-nickel based catalyst has lower cost, higher activity and stability. However, such catalysts have problems such as low catalytic activity, insufficient conductivity, few exposed active sites, poor stability, etc., which limit the practical use of these catalysts in industrial water electrolysis devices. In order to solve the problems, a composite structure is formed with other materials, which is beneficial to exposing more reaction active centers and realizing the structural optimization of the iron-nickel based catalyst, such as using conductive substrates, such as foamed nickel, carbon nano paper and the like, however, the catalyst material obtained by using the substrates is difficult to obtain a nano powder catalyst, and cannot be applied to an electrocatalyst subjected to preprocessing treatment.

Metal Organic Framework (MOF) materials have high composite porous structures, and these framework structures have unique three-dimensional nanostructures that expose different edge structures, and are widely used in the preparation of electrocatalysts (Adv Mater,29(2017) 1604898). However, such conventionally derived materials such as oxides, sulfides, and the like have problems of insufficient catalytic activity, poor conductivity, and the like. Although the formation of a carbon-based structure is facilitated by further pyrolysis carbonization treatment, and higher conductivity is realized, the carbonization treatment is easy to form a carbon-coated structure, and a dense coating structure does not facilitate the exposure of metal catalytic active centers, so that higher electrocatalytic activity is difficult to obtain. The method of surface etching such as acid etching, oxygen etching, plasma treatment and the like is helpful to expose more active sites, however, the methods are only surface treatment and are not beneficial to the continuous integrity and stability of the electrocatalyst structure.

Disclosure of Invention

The application aims to provide a bimetallic MOF derived catalyst, and a preparation method and application thereof, and aims to solve the problems of low catalytic activity, insufficient conductivity, few exposed active sites, difficult formation of active sites and poor catalytic stability to a certain extent.

In order to achieve the purpose of the application, the technical scheme adopted by the application is as follows:

in a first aspect of the application, a bimetallic MOF-derived catalyst is provided, comprising a nanoalloy matrix based on a bimetallic MOF architecture, nitrogen-doped carbon nanotubes attached to the surface of the nanoalloy matrix, and a metal fluoride dispersed between the nanoalloy matrix.

In a second aspect of the present application, there is provided a method of preparing a bimetallic MOF derived catalyst comprising the steps of:

carrying out modification treatment on the bimetallic MOF and the nonionic polymer compound in an organic solvent to obtain a first intermediate;

mixing the first intermediate, soluble zinc salt and a nitrogen-containing ligand in an organic solvent for reaction to obtain a second intermediate;

carbonizing the second intermediate to obtain a third intermediate;

and mixing the third intermediate with a fluorinating agent for fluorination treatment to obtain the catalyst.

In a third aspect of the present application, there is provided the use of a bimetallic MOF derived catalyst as described herein above and/or prepared by the above preparation method in an electrolytic water oxygen evolution reaction.

Compared with the prior art, the bimetallic MOF derived catalyst provided by the application has the advantages that the loose nitrogen-doped carbon nano tubes attached to the surface greatly improve the conductivity of the catalyst, the metal fluoride dispersed between the nano alloy substrates improves the polarity of the catalyst, active sites are exposed to the maximum degree, the nano alloy substrates and the nitrogen-doped carbon nano tubes are compounded to form a porous frame structure, the structure is stable, the agglomeration of metal nano particles can be prevented, the full contact with electrolyte is realized, and the catalytic activity of the catalyst is greatly improved.

According to the preparation method of the bimetallic MOF-derived catalyst provided by the second aspect of the application, the nitrogen-doped carbon nanotubes attached to the surface of the prepared catalyst are loose and not compact, the metal catalytic activity center is favorably exposed, higher catalytic activity is obtained, the yield of the catalyst is high, side reactions are few, the preparation process is simple, the process conditions are easy to control, and the crystal morphology and the structural performance of the prepared catalyst reach the optimal level.

The bimetallic MOF derived catalyst provided by the third aspect of the application shows excellent performance in anodic oxygen generation reaction in a water electrolysis hydrogen production process, and the catalytic activity far exceeds that of commercial IrO₂The catalyst has wide application prospect in the electrolytic water oxygen evolution reaction as a high-efficiency non-noble metal electrocatalyst

Drawings

In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings needed to be used in the embodiments or the prior art descriptions will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments of the present application, and it is obvious for those skilled in the art to obtain other drawings without creative efforts.

Fig. 1 is an SEM image of a FeNi MIL MOF sample provided in example 1 of the present application.

FIG. 2 is an SEM image of a FeNi MIL @ ZIF 8 sample provided in example 1 herein.

FIG. 3 is an XRD pattern of the FeNi @ NCNT-F catalyst provided in example 1 herein.

FIG. 4 is an SEM image of the FeNi @ NCNT-F catalyst provided in example 1 herein.

FIG. 5 is a plot of the oxygen evolution polarization of the FeNi @ NCNT-F catalyst provided in example 1 of the present application.

FIG. 6 is an SEM image of the FeNi MIL @ ZIF 81-6 catalyst provided in example 2 herein.

FIG. 7 is an SEM image of the FeNi @ NCNT-F-1-6 catalyst provided in example 2 herein.

FIG. 8 is an XRD pattern of the FeNi @ NCNT-F-1-6 catalyst provided in example 2 herein.

FIG. 9 is a graph of the oxygen evolution polarization curve performance of the FeNi @ NCNT-F-1-6 catalyst provided in example 2 herein.

FIG. 10 is an SEM image of the FeNi MIL @ ZIF 81-10 catalyst provided in example 3 herein.

FIG. 11 is an SEM image of the FeNi @ NCNT-F-1-10 catalyst provided in example 3 herein.

FIG. 12 is an XRD pattern of the FeNi @ NCNT-F-1-10 catalyst provided in example 3 herein.

FIG. 13 is a graph of the performance of the FeNi @ NCNT-F-1-10 catalyst provided in example 3 herein.

FIG. 14 is an XRD pattern of the FeNi @ C-F catalyst provided in comparative example 1 herein.

FIG. 15 is an SEM image of a FeNi @ C-F catalyst provided in comparative example 1 herein.

FIG. 16 is a graph of the performance of the FeNi @ C-F catalyst provided in comparative example 1 herein.

FIG. 17 is an SEM image of the FeNi @ NCNT catalyst provided in comparative example 2 herein.

FIG. 18 is an XRD pattern of the FeNi @ NCNT catalyst provided in comparative example 2 herein.

FIG. 19 is a graph of the performance of the FeNi @ NCNT catalyst provided in comparative example 2 herein.

Detailed Description

In order to make the technical problems, technical solutions and advantageous effects to be solved by the present application more clearly apparent, the present application is further described in detail below with reference to the embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the present application and are not intended to limit the present application.

In this application, the term "and/or" describes an association relationship of associated objects, meaning that there may be three relationships, e.g., a and/or B, which may mean: a is present alone, A and B are present simultaneously, and B is present alone. Wherein A and B can be singular or plural. The character "/" generally indicates that the former and latter associated objects are in an "or" relationship.

In the present application, "at least one" means one or more, "a plurality" means two or more. "at least one of the following" or similar expressions refer to any combination of these items, including any combination of the singular or plural items. For example, "at least one (one) of a, b, or c," or "at least one (one) of a, b, and c," may each represent: a, b, c, a-b (i.e., a and b), a-c, b-c, or a-b-c, wherein a, b, and c may be single or plural, respectively.

It should be understood that, in various embodiments of the present application, the sequence numbers of the above-mentioned processes do not mean the execution sequence, some or all of the steps may be executed in parallel or executed sequentially, and the execution sequence of each process should be determined by its function and inherent logic, and should not constitute any limitation to the implementation process of the embodiments of the present application.

The terminology used in the embodiments of the present application is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. As used in the examples of this application and the appended claims, the singular forms "a," "an," and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise.

The weight of the related components mentioned in the description of the embodiments of the present application may not only refer to the specific content of each component, but also represent the proportional relationship of the weight among the components, and therefore, the content of the related components is scaled up or down within the scope disclosed in the description of the embodiments of the present application as long as it is scaled up or down according to the description of the embodiments of the present application. Specifically, the mass in the description of the embodiments of the present application may be in units of mass known in the chemical industry, such as μ g, mg, g, and kg.

The terms "first" and "second" are used for descriptive purposes only and are used for distinguishing purposes such as substances from one another, and are not to be construed as indicating or implying relative importance or implying any number of technical features indicated. For example, a first XX may also be referred to as a second XX, and similarly, a second XX may also be referred to as a first XX, without departing from the scope of embodiments of the present application. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature.

In a first aspect, embodiments herein provide a bimetallic MOF-derived catalyst comprising a nanoalloy matrix based on a bimetallic MOF architecture, nitrogen-doped carbon nanotubes attached to the surface of the nanoalloy matrix, and a metal fluoride dispersed between the nanoalloy matrix.

It should be noted that the catalyst derived from the bimetallic MOF provided in the first aspect of the embodiment of the present application is a MOF, a Metal-organic framework material (Metal-organic frameworks), which refers to a crystalline porous material having a periodic network structure formed by self-assembly of a transition Metal and an organic ligand, and the catalyst provided in the embodiment of the present application is based on a porous framework structure formed by compounding a nano alloy matrix with a bimetallic MOF structure and a nitrogen-doped carbon nanotube, and has a stable structure, so that the aggregation of Metal nanoparticles can be prevented, the full contact with an electrolyte can be realized, and the catalytic activity of the catalyst can be greatly improved.

In a further embodiment of the present invention, the catalyst composed of the aforesaid nanoalloy matrix and nitrogen-doped carbon nanotubes and metal fluorides of the nanoalloy is FeNi @ NCNT-F, CoNi @ NCNT-F, CoFe @ NCNT-F, CoMn @ NCNT-F, NiMn @ NCNT-F, i.e., the complex Fe-Ni alloy/Fe-fluoride/Ni-fluoride, the complex Co-Ni alloy/Co-fluoride/Ni-fluoride, the complex Co-Fe alloy/Co-fluoride/Fe-fluoride of the autocatalytic nitrogen-doped carbon nanotubes, the complex Co-Mn alloy/Co-fluoride/Mn-fluoride of the autocatalytic nitrogen-doped carbon nanotubes, the complex Co-Ni-fluoride/Co-fluoride, Mn-fluoride of the autocatalytic nitrogen-doped carbon nanotubes, Self-catalyzed nitrogen-doped carbon nanotube composite nickel-manganese alloy/nickel fluoride and manganese fluoride.

The inventor researches and discovers that loose nitrogen-doped carbon nanotubes attached to the surface of a nano alloy substrate not only greatly improve the conductivity of the catalyst, but also help to expose a metal catalytic active center and obtain higher catalytic activity; the metal fluoride dispersed among the nano alloy matrixes improves the polarity of the catalyst, has a synergistic effect with the nitrogen-doped carbon nano tube, maximally exposes active sites and is beneficial to electrocatalytic reaction.

In some embodiments of the present application, the content percentage of the nano alloy matrix in the catalyst is 7.5 to 20% by mass, and the nano alloy matrix is a uniform rice grain-shaped structure with a diameter of 80 to 200nm and a length of 0.5 to 1 μm. The nano alloy matrix with the content and the size structure ensures that the catalyst has large specific surface area, more catalytic active centers and better catalytic effect.

In some embodiments of the present application, the metal element in the nanoalloy matrix comprises two of the transition elements, and is a good catalyst because the transition metal has d orbital electrons or vacant d orbitals, which can provide vacant orbitals to act as electrophiles or lone pair electrons to act as nucleophiles in chemical reactions, form intermediates, reduce activation energy of the reactions, and promote the reactions. .

In some embodiments of the present application, the content percentage of the nitrogen-doped carbon nanotube in the catalyst is 80.19 to 93.51% by mass, a loose nitrogen-doped carbon nanotube adhesion layer is formed on the surface of the rice-shaped nano alloy substrate, and the adhesion density of the nitrogen-doped carbon nanotube is 0.04mg cm^-3～0.05mg cm^-3After the nitrogen atoms are doped into the carbon material framework, more free electrons can be provided, so that the conductivity of the material is further improved.

In some embodiments of the present application, the content percentage of the metal fluoride is 5.3% to 15.6% by mass, the metal element in the metal fluoride is one of the metal elements in the nano-alloy matrix, and the fluorinating agent subjected to the fluorination treatment passes through the loose nitrogen-doped carbon nanotube adhesion layer and directly reacts with the nano-alloy matrix to generate the metal fluoride, so that the polarity of the nano-alloy matrix is enhanced, and introduction of new impurities is avoided.

In a second aspect, embodiments herein provide a method of preparing a bimetallic MOF derived catalyst, comprising the steps of:

s1: carrying out modification treatment on the bimetallic MOF and the nonionic polymer compound in an organic solvent to obtain a first intermediate;

s2: mixing the first intermediate, soluble zinc salt and a nitrogen-containing ligand in an organic solvent for reaction to obtain a second intermediate;

s3: carbonizing the second intermediate to obtain a third intermediate;

s4: and mixing the third intermediate with a fluorinating agent for fluorination treatment to obtain the catalyst.

According to the preparation method of the bimetallic MOF derived catalyst provided by the second aspect of the embodiment of the application, the nitrogen-doped carbon nano tube attached to the surface of the synthesized catalyst is loose and not compact, the metal catalytic activity center is favorably exposed, higher catalytic activity is obtained, the yield of the catalyst is high, side reactions are few, the preparation process is simple, the process conditions are easy to control, and the crystal morphology and the structural performance of the prepared catalyst reach the optimal level.

In the embodiment of the present application, the bimetallic MOF in step S1 is one of a one-dimensional bimetallic MOF, a two-dimensional bimetallic MOF, and a three-dimensional bimetallic MOF, in the further embodiment of the present application, the bimetallic MOF is a one-dimensional bimetallic MOF with a larger specific surface area and more metal active centers, in specific embodiments, the one-dimensional bimetallic MOF includes but is not limited to FeNi MOF, CoNi MOF, CoFe MOF, commn MOF, and NiMn MOF, further, the one-dimensional bimetallic MOF is preferably of MIL series, it is to be noted that MIL series materials are synthesized first by the teaching group of Frey of university of vanel, france, and MIL series materials can be classified into two types, one type is synthesized by lanthanide series and transition metal elements and dicarboxylic acids such as glutaric acid and succinic acid; the other is synthesized by trivalent metals such as chromium, iron, aluminum or vanadium and carboxylic acid such as terephthalic acid or trimesic acid, and the MIL series materials have huge specific surface area and stable structural characteristics.

In embodiments of the present application, the bimetallic MOFs can be obtained according to existing methods. As in the examples, FeNi MIL MOFs can be prepared, but not exclusively, as follows:

sequentially adding iron salt, nickel salt, carboxylic acid and alkali solution into an organic solvent, stirring to obtain a mixed solution, and carrying out heat preservation treatment on the mixed solution to obtain FeNi MIL MOF.

Wherein the temperature of the heat preservation treatment is about 100 ℃, the heat preservation time is about 15 hours, and the complete reaction of each reactant in the mixed solution is ensured.

In one particular embodiment of the present application, the FeNi MIL MOF can be made as follows: 905mg of ferric chloride, 480mg of nickel nitrate and 831mg of terephthalic acid were sequentially added to 50mL of N, N-dimethylformamide solution, and then 20mL of 0.2M NaOH solution was added thereto, and the mixture was stirred at room temperature until uniform mixing was achieved to obtain a mixed solution. And transferring the mixed solution into a polytetrafluoroethylene substrate with the volume of 100mL, setting the temperature of an oven at 100 ℃, and keeping the temperature for 15 h. And after the reaction is finished and the temperature is cooled to room temperature, washing the reaction product for multiple times by using deionized water and ethanol, centrifuging, drying in vacuum to obtain yellow powder, and testing by using a powder XRD diffractometer to obtain the FeNi MIL MOF.

In the embodiment of the application, the non-ionic high molecular compound comprises one of polyvinylpyrrolidone, polyethylene oxide-polypropylene oxide-polyethylene oxide triblock copolymer, 1, 10-non-phenanthroline, polyacrylamide and polyoxyethylene alkylamine, the non-ionic high molecular compound is adopted to modify the bimetallic MOF, so that a nano alloy matrix of the bimetallic MOF is stably dispersed without agglomeration, meanwhile, the soluble zinc salt and the nitrogen-containing ligand are guided to self-assemble on the surface of the nano alloy matrix to form a coordination polymer, and the crystal structure, the particle size and the structural performance of a second intermediate prepared by a mixing reaction in the subsequent S2 reach the optimal level.

In the examples of the present application, the organic solvent includes one of methanol, ethanol, and isopropanol, and preferably methanol, so that the second intermediate of the ZIF (porous crystalline material) crystal structure can be prepared without heating.

In the embodiment of the application, the volume ratio of the nonionic polymer compound to the organic solvent is 1 (20-25), too much or too little nonionic polymer compound does not affect the growth change of the ZIF crystal, but the appearance of the ZIF crystal of the second intermediate is affected, and the structural performance does not reach the optimal level.

In the examples of the present application, the modification treatment in step S1 is accompanied by stirring treatment, and further, the stirring time is about 15 hours, so that the bimetallic MOF is sufficiently reacted to obtain the first intermediate.

In one embodiment of the present application, the first intermediate in step S1 can be prepared as follows:

and dissolving 800mg of synthesized FeNi MIL MOF and 4g of polyvinylpyrrolidone in 80mL of methanol solution at room temperature, and stirring for 15h to obtain polyvinylpyrrolidone functionalized FeNi MIL MOF, namely a first intermediate.

In step S2, in an embodiment of the present application, the soluble zinc salt includes one of zinc nitrate, zinc acetate, zinc chloride, and zinc sulfate, the nitrogen-containing ligand includes one of imidazole, pyridine, and bipyridine, the soluble zinc salt reacts with the nitrogen-containing ligand to generate ZIF 8, in some embodiments of the present application, the nitrogen-containing ligand is 2-methylimidazole, a molar ratio of the soluble zinc salt to the 2-methylimidazole is 1 (6-10), and the molar ratio of the soluble zinc salt to the nitrogen-containing ligand includes, but is not limited to, 1 (6-10) provided in the above embodiments of the present application. In addition, Zn and a nitrogen-containing ligand of the bimetallic MOF are linked and reacted to form a crystal structure, and a second intermediate, namely the bimetallic MOF @ ZIF 8 is obtained, wherein the ZIF 8 is formed by Zn²⁺A porous material with topological structure formed by imidazole ligand is a typical representation in zeolite imidazole ester metal organic frameworks (ZIFs), and the framework structure of ZIF 8 is formed by Zn²⁺The tetrahedral structure unit formed by connecting with N atoms in the imidazolyl ligand has permanent pores, high surface area, hydrophobicity, open metal sites and excellent water stability and thermal stability.

In a specific example of the present application, the second intermediate in step S2 can be prepared as follows:

centrifuging and washing polyvinylpyrrolidone functionalized FeNi MIL MOF, namely a first intermediate, with methanol for three times, dispersing in 55mL of methanol solution to obtain a solution A, dissolving 8mmol of zinc nitrate in 100mL of methanol solution to obtain a solution B, dissolving 64mmol of 2-methylimidazole in 140mL of methanol solution to obtain a solution C, mixing and stirring the solutions A, B and C for 5min, and standing for 24h, wherein the molar ratio of the zinc nitrate to the 2-methylimidazole is 1: 8. After the reaction is finished, washing the reaction product for multiple times by using methanol and ethanol, centrifuging the reaction product, and drying the reaction product in vacuum to obtain light yellow powder FeNi MIL @ ZIF 8, namely a second intermediate.

In step S3, in the embodiment of the present application, the carbonization temperature of the carbonization process is 750-950 ℃, at this temperature, the ZIF 8 connected to the surface of the bimetallic MOF, i.e., the second intermediate, is subjected to autocatalytic carbonization, the metal node in the ZIF 8 connected to the surface of the bimetallic MOF is reduced to Zn, which vaporizes and escapes to form a porous structure, the bimetallic MOF is converted into a nano-alloy matrix in the shape of rice grains, and meanwhile, the ZIF particles are converted into nitrogen-doped carbon nanotubes (NCNT) in the high-temperature carbonization process and attached to the surface of the nano-alloy matrix in the shape of rice grains, so as to obtain a third intermediate.

In the embodiment of the application, the carbonization treatment is heated to the carbonization temperature by a programmed heating method, and further, the carbonization temperature is heated to the carbonization temperature at a heating rate of 2-3 ℃/min, so that the heating is reasonably controlled, the structural stability of the material is favorably kept, the crystal structure performance and the appearance form of the generated third intermediate reach the optimal effect, and meanwhile, the programmed heating is also favorable for prolonging the service life of the tube furnace.

In one embodiment of the present application, the third intermediate in step S3 can be prepared as follows:

heating FeNi MIL @ ZIF 8500 mg to 920 ℃ at the heating rate of 2 ℃/min, preserving the heat for 2h, and centrifugally drying to obtain a carbonized product connected with the autocatalytic nitrogen-doped nanotube, namely a third intermediate.

In step S4, in the embodiment of the present application, the fluorinating agent includes one of ammonium fluoride, ammonium fluoroborate, N-diisopropylethylamine trihydrofluoride, and hydrogen fluoride, is used for carrying out fluorination treatment on the third intermediate to generate metal fluoride which is dispersed among nano alloy matrixes to improve the polarity of the material, and further, in some embodiments herein, the mass ratio of the third intermediate to the fluorinating agent is 1: (8-12), the fluorination temperature of the fluorination treatment is 200-450 ℃, the temperature is raised to the fluorination temperature by a programmed temperature raising method, heating to the fluorination temperature at a heating rate of 2-3 ℃/min, which is favorable for maintaining the structural stability of the material, the crystal structure performance and appearance form of the generated catalyst reach the best effect, and meanwhile, the programmed temperature rise is also beneficial to prolonging the service life of the tube furnace.

In one embodiment of the present application, the catalyst in step S4 can be prepared as follows: and after the carbonization is finished, cooling to room temperature to obtain a carbonized product, namely a third intermediate, adding ammonium fluoride according to the mass ratio of the third intermediate to the ammonium fluoride of 1:10, heating to 450 ℃ at the heating rate of 3 ℃/min, preserving the temperature for 2h, cooling to room temperature, and centrifugally drying to obtain the catalyst FeNi @ NCNT-F connected with the autocatalytic nitrogen-doped nanotube.

The bimetallic MOF derived catalyst provided by the third aspect of the application has a porous structure of transition metal nano alloy matrix and metal fluoride nano powder attached to a self-catalytic nitrogen-doped nanotube on the surface, and in the water electrolysis anode oxygen precipitation reaction, the problems of poor polarity, low conductivity and the like of a conventional catalyst are solved, and the bimetallic MOF derived catalyst has rich and fully-exposed catalytic reaction active sites, high water electrolysis oxygen precipitation activity, excellent performance in the anode oxygen production reaction in the water electrolysis hydrogen production process, and catalytic activity far exceeding that of a commercial IrO2 catalyst, and has a wide application prospect in the water electrolysis oxygen precipitation reaction as a high-efficiency non-noble metal electrocatalyst.

In order to make the details and operations of the above-mentioned embodiments of the present invention clearly understood by those skilled in the art, and to make the progress of the catalyst derived from bimetallic MOF and the method for preparing the same obviously apparent, the above-mentioned technical solutions are illustrated by the following examples.

Example 1

Preparation of FeNi @ NCNT-F electrooxidation oxygen generation catalyst:

in the first step, 905mg of ferric chloride, 480mg of nickel nitrate and 831mg of terephthalic acid were sequentially added to 50mL of N, N-dimethylformamide solution, and then 20mL of 0.2M NaOH solution was added thereto, and stirred at normal temperature until they were uniformly mixed. The solution is transferred into a polytetrafluoroethylene substrate with the volume of 100mL, the temperature of an oven is set to be 100 ℃, and the heat preservation time is 15 h. And after the reaction is finished and the temperature is cooled to room temperature, washing the reaction product for multiple times by using deionized water and ethanol, centrifuging, drying in vacuum to obtain yellow powder, testing by using a powder XRD diffractometer to obtain FeNi MIL MOF, and using the FeNi MIL MOF for the next experiment.

Second, 800mg of the synthesized FeNi MIL MOF, 4g of polyvinylpyrrolidone were dissolved in 80mL of methanol solution at room temperature and stirred for 15 h.

And thirdly, centrifuging and washing the polyvinylpyrrolidone functionalized FeNi MIL MOF for three times by using methanol, dispersing the polyvinylpyrrolidone functionalized FeNi MIL MOF into 55mL of methanol solution to obtain a solution A, dissolving 8mmol of zinc nitrate into 100mL of methanol solution to obtain a solution B, dissolving 64mmol of 2-methylimidazole into 140mL of methanol solution to obtain a solution C, mixing and stirring the solutions A, B and C for 5min, and standing for 24h, wherein the molar ratio of the zinc nitrate to the 2-methylimidazole is 1: 8. After the reaction is finished, washing the reaction product for multiple times by using methanol and ethanol, centrifuging the reaction product, and drying the reaction product in vacuum to obtain light yellow powder FeNi MIL @ ZIF 8.

And fourthly, heating FeNi MIL @ ZIF 8500 mg to 920 ℃ at the heating rate of 2 ℃/min, preserving the temperature for 2h, and centrifugally drying to obtain a carbonized product connected with the autocatalytic nitrogen-doped nanotube. And (3) heating the carbonized product and ammonium fluoride to 450 ℃ at a heating rate of 3 ℃/min according to a mass ratio of 1:10, preserving the temperature for 2h, cooling to room temperature, and centrifugally drying to obtain FeNi @ NCNT-F.

FIG. 1 is an SEM image of the FeNi MIL MOF prepared in example 1, and it can be seen that the prepared FeNi MIL MOF has a uniform rice-grain structure with a length of about 1-2 μm and a width of 100-200 nm.

FIG. 2 is an SEM image of FeNi MIL @ ZIF 8 prepared in example 1, from which it can be seen that ZIF 8 successfully grows on rice-grain-shaped FeNi MIL MOF.

FIGS. 3 and 4 are an XRD pattern and an SEM image of FeNi @ NCNT-F obtained in example 1. FeNi MIL @ ZIF 8 at N₂Pyrolysis and low temperature fluorine in atmosphereAfter the crystallization, FeF appears in the crystal structure₂And FeNi alloy, Zn can be gasified at high temperature, ZIF particles fixed on the MIL surface structure are converted into CNTs in the high-temperature carbonization process and uniformly cover the surfaces of the nanorods, and the XRD pattern shows that FeF is generated₂FeNi alloys and carbon nanotubes.

FIG. 5 is a graph of the catalytic performance of the FeNi @ NCNT-F electro-oxidation catalyst obtained in example 1 in a 1M KOH electrolyte. The method is carried out by adopting a standard three-electrode system at normal temperature (25 ℃), wherein the electrolyte is 1M KOH, the working electrode is a FeNi @ NCNT-F electrocatalyst covered on a glassy carbon electrode, the counter electrode is a graphite electrode, the reference electrode is an Hg/HgO electrode, and the specific preparation process of the working electrode is as follows: 5mg of catalyst is dispersed in 950 mu L of ethanol and 50 mu L of Nafion solution to prepare catalyst ink with good dispersibility, 10 mu L of catalyst ink is dripped on the surface of the glassy carbon electrode, and the catalyst ink is dried and used for water electrolysis oxygen evolution reaction. From the electrochemical polarization curve chart of the oxygen evolution reaction, the current density reaches 10mA cm^-2The overpotential of (2) is only 238 mV.

Example 2

Preparation of FeNi @ NCNT-F-1-6 electrooxidation catalyst:

the procedure of this example is the same as in example 1 except that the molar ratio of zinc nitrate to 2-methylimidazole is 1: 6; in the second step, the preparation of the solution C is that 48mmol of 2-methylimidazole is dissolved in 100mL of methanol solution to obtain a solution C, the solution A, the solution B and the solution C are mixed and stirred for 5min and then are kept stand for 24h, and the molar ratio of zinc nitrate to 2-methylimidazole is 1: 6.

FIG. 6 is an SEM image of FeNi MIL @ ZIF 8-1-6MOF prepared in example 2, showing that particles of ZIF 8 are relatively large covering the surface of the FeNi MIL MOF. FIGS. 7 and 8 are SEM and XRD of FeNi @ NCNT-F-1-6 after the carbonization and fluorination, and the surface-coated ZIF 8 was converted to CNT, but agglomeration was still observed. FeNi MIL @ ZIF 8-1-6MOF in N₂After carbonization pyrolysis and low-temperature fluorination in atmosphere, FeF appears in the crystal structure₂And FeNi alloys.

FIG. 9 is a graph of the catalytic performance of the FeNi @ NCNT-F-1-6 electro-oxidation catalyst obtained in example 2 in a 1MKOH electrolyte. Test procedure thereofThe sequence and conditions are the same as above, and the current density reaches 10mA cm in the catalytic oxygen evolution reaction^-2The overpotential at this time was 247 mV.

Example 3

Preparation of FeNi @ NCNT-F-1-10 electrooxidation catalyst:

the procedure of this example is the same as in example 1 except that the molar ratio of zinc nitrate to 2-methylimidazole is 1: 10; specifically, in the second step, the preparation of the solution C is that 80mmol of 2-methylimidazole is dissolved in 180mL of methanol solution to obtain a solution C, the solutions A, B and C are mixed and stirred for 5min and then are kept stand for 24h, and the molar ratio of zinc nitrate to 2-methylimidazole is 1: 10.

FIG. 10 is an SEM image of FeNi MIL @ ZIF 8-1-10MOF prepared in example 3, from which it can be seen that a portion of ZIF 8 has grown on the surface of the FeNi MIL MOF. FIGS. 11 and 12 are SEM and XRD patterns of FeNi @ NCNT-F-1-10 after carbonization and fluorination, and the ZIF 8 particles are converted into a large number of CNTs covering the surface of the nanorods, and the XRD patterns show that the bulk structure is still FeF₂And FeNi alloys.

FIG. 13 is a graph of the catalytic performance of the FeNi @ NCNT-F-1-10 electro-oxidation catalyst obtained in example 3 in a 1MKOH electrolyte. The test conditions and the steps are the same, and the current density reaches 10mA cm in the catalytic oxygen evolution reaction^-2The overpotential in this case was 261 mV.

Comparative example 1

Preparation of FeNi @ C-F electrooxidation catalyst:

step one, taking 500mg of FeNi MIL MOF, heating to 920 ℃ at the heating rate of 2 ℃/min, preserving heat for 2h, cooling to room temperature, and centrifugally drying to obtain a carbonized product. And (3) heating the carbonized product and ammonium fluoride to 450 ℃ at a heating rate of 3 ℃/min according to a mass ratio of 1:10, preserving the heat for 2h, cooling to room temperature, and centrifugally drying to obtain FeNi @ C-F.

FIGS. 14 and 15 are XRD and SEM images of the resulting FeNi MIL MOF-derived FeNi @ C-F. After high-temperature carbonization and low-temperature fluorination, the rice grain structure of FeNi MIL MOF is damaged and partially agglomerated, the fluorination treatment causes defects on the surface of the rice grain structure, and the crystal structure of the rice grain structure is shown as FeF₂And FeNi alloys. FIG. 16 shows the catalysis of the FeNi @ C-F electro-oxidation catalyst obtained in comparative example 1 in a 1M KOH electrolyteChemical property profile. From the polarization curve chart, the catalyst current density reaches 10mA cm^-2The overpotential of (3) is 263 mV.

Comparative example 2

Preparation of FeNi @ NCNT electrooxidation catalyst:

in the first step, 800mg of synthesized FeNi MIL MOF, 4g of polyvinylpyrrolidone were dissolved in 80mL of methanol solution at room temperature and stirred for 15 h.

And secondly, centrifuging and washing the polyvinylpyrrolidone functionalized FeNiMIL MOF with methanol for three times, dispersing the washed FeNiMIL MOF in 55mL of methanol solution to obtain a solution A, dissolving 8mmol of zinc nitrate in 100mL of methanol solution to obtain a solution B, dissolving 64mmol of 2-methylimidazole in 140mL of methanol solution to obtain a solution C, mixing and stirring the solutions A, B and C for 5min, and standing for 24h, wherein the molar ratio of the zinc nitrate to the 2-methylimidazole is 1: 8. After the reaction is finished, washing the reaction product for many times by using methanol and ethanol, centrifuging the reaction product, and drying the reaction product in vacuum to obtain light yellow powder.

And thirdly, heating FeNi MIL @ ZIF 8500 mg to 920 ℃ at the heating rate of 2 ℃/min, preserving heat for 2h, cooling to room temperature, centrifuging, washing and drying to obtain FeNi @ NCNT.

FIGS. 17 and 18 are SEM and XRD patterns of FeNi @ NCNT prepared in comparative example 2, from which it can be seen that the rice-grain structure of the prepared FeNi @ NCNT catalyst exhibited significant amounts of CNT on the surface after high temperature calcination, and the XRD pattern showed the formation of carbon and FeNi alloys after calcination.

FIG. 19 is a graph of the catalytic performance of the FeNi @ NCNT electro-oxidation catalyst obtained in comparative example 2 in a 1MKOH electrolyte. The current density reaches 10mA cm in the catalytic oxygen evolution reaction^-2The overpotential in this case was 271 mV.

Comparative example 3

Commercial IrO that will be currently commonly used to catalyze oxygen evolution reactions₂The catalyst is used for catalytic oxygen evolution reaction, and the current density reaches 10mA cm^-2The overpotential at this time was 302 mV.

Comparative example 4

FeNi MIL @ ZnCo ZIF is taken as a template, FeNiCo @ NC-P is prepared by high-temperature carbonization and low-temperature phosphorization, and the current density reaches 10mA cm in the catalytic oxygen evolution reaction in 1M KOH solution^-2The overpotential at this time was 310 mV.

The above description is only exemplary of the present application and should not be taken as limiting the present application, as any modification, equivalent replacement, or improvement made within the spirit and principle of the present application should be included in the protection scope of the present application.

Claims

1. a bimetallic MOF-derived catalyst is characterized in that, comprising the nano-alloy matrix based on bimetallic MOF structure, the nitrogen-doped carbon nanotubes attached to the surface of the nano-alloy matrix and dispersed in the nano-alloy matrix. intermetallic fluoride.

2. The catalyst according to claim 1, wherein the metal element in the nano-alloy matrix comprises two kinds of transition elements; and/or

The metal element in the metal fluoride is one of the metal elements in the nano-alloy matrix.

3 . The catalyst according to claim 2 , wherein the nano-alloy matrix comprises one of FeNi alloy, CoNi alloy, CoFe alloy, CoMn alloy, and NiMn alloy. 4 .

4. The catalyst according to any one of claims 1-3, wherein the catalyst is FeNi@NCNT-F, CoNi@NCNT-F, CoFe@NCNT-F, CoMn@NCNT-F, NiMn@ One of NCNT-F.

5. The catalyst according to any one of claims 1-3, wherein the nano-alloy matrix is in the shape of rice grains; and/or

The diameter of the nano-alloy matrix is 80 nm to 200 nm; and/or

The length of the nano-alloy matrix is 0.5 μm˜1 μm; and/or

The adhesion density of the nitrogen-doped carbon nanotubes is 0.04 mg cm ^-3 to 0.05 mg cm ^-3 .

6. The catalyst according to any one of claims 1-3, wherein the content percentage of the nano-alloy matrix in the catalyst is 7.5%-20% by mass;

The content percentage of the nitrogen-doped carbon nanotubes is 80.19%-93.51% by mass;

The content percentage of the metal fluoride is 5.3%-15.6% by mass.

7. a preparation method of bimetallic MOF-derived catalyst, is characterized in that, comprises the following steps:

The first intermediate is obtained by modifying the bimetallic MOF and the non-ionic polymer compound in an organic solvent;

The second intermediate is obtained after mixing and reacting the first intermediate with the soluble zinc salt and the nitrogen-containing ligand in an organic solvent;

The second intermediate is carbonized to obtain the third intermediate;

The catalyst is obtained by mixing the third intermediate with a fluorinating agent and performing fluorination treatment.

8. the preparation method of catalyst according to claim 7, is characterized in that, described bimetallic MOF is a kind of in one-dimensional bimetallic MOF, two-dimensional bimetallic MOF, three-dimensional bimetallic MOF; And/or

The non-ionic polymer compounds include polyvinylpyrrolidone, polyethylene oxide-polypropylene oxide-polyethylene oxide triblock copolymer, 1,10-non-roline, polyacrylamide, polyoxyethylene one of alkylamines; and/or

The soluble zinc salt includes one of zinc nitrate, zinc acetate, zinc chloride, and zinc sulfate; and/or

The nitrogen-containing ligand includes one of imidazole, pyridine, and bipyridine; and/or

The organic solvent includes one of methanol, ethanol, and isopropanol; and/or

The carbonization temperature of the carbonization treatment is 750-950°C; and/or

The fluorinating agent includes one of ammonium fluoride, ammonium fluoroborate, N,N-diisopropylethylamine trihydrofluoride, and hydrogen fluoride; and/or

The fluorination temperature of the fluorination treatment is 200-450°C; and/or

The modification process is accompanied by agitation; and/or

The carbonization treatment is heated to the carbonization temperature by a temperature-programmed method; and/or

The fluorination treatment is heated to the fluorination temperature by a temperature-programmed method.

9 . The method for preparing a catalyst according to claim 8 , wherein the bimetallic MOF is a MIL series material. 10 .

10. The bimetallic MOF-derived catalyst prepared according to the arbitrary described bimetallic MOF-derived catalyst of claim 1-6 and/or the bimetallic MOF-derived catalyst prepared by the arbitrary described preparation method of claim 7-9 in the water electrolysis oxygen evolution reaction application.