M2C/carbon nanosheet composite material and preparation method and application thereof
阅读说明：本技术 M2c/碳纳米片复合材料及其制备方法和应用 (M2C/carbon nanosheet composite material and preparation method and application thereof ) 是由 翟俊宜 雷瑛 于 2019-09-05 设计创作，主要内容包括：本发明涉及电催化材料领域,具体涉及M_2C/碳纳米片复合材料及其制备方法和应用。所述复合材料包括多孔碳纳米片基体,以及生长在所述多孔碳纳米片基体上的M_2C颗粒,其中,M为Mo元素和/或W元素。所得复合材料催化剂具有很大的比表面积和电化学活性面积,能够暴露更多活性位点,使得催化剂电催化析氢能力得到极大的增强。(The invention relates to the field of electrocatalytic materials, in particular to M 2 C/carbon nanosheet composite material and preparation method and application thereof. The composite material comprises a porous carbon nanosheet substrate and M growing on the porous carbon nanosheet substrate 2 C particles, wherein M is Mo element and/or W element. The obtained composite catalyst has large specific surface area and electrochemical active area, and can expose more active sites, so that the electro-catalytic hydrogen evolution capability of the catalyst is greatly enhanced.)
1. M2A C/carbon nanoplate composite, the composite comprising a porous carbon nanoplate matrix, and M grown on the porous carbon nanoplate matrix2C particles, wherein M is Mo element and/or W element.
2. The composite material of claim 1, wherein the specific surface area of the composite material is 1000-1600m2(ii)/g, average pore diameter is 1-10 nm;
Preferably, the electrochemical active area of the composite material is 400-700m2/g。
3. The composite material according to claim 1 or 2, wherein M is2The total weight of the C/carbon nano sheet composite material is taken as a reference, M2the content of the C particles is 10-60 wt%, and the content of the porous carbon nanosheet substrate is 40-90 wt%.
4. Preparation of M2A method of C/carbon nanoplatelet composites, the method comprising the steps of:
(1) Will MS2First contacting with dopamine source and base to form MS2Polydopamine complexes;
(2) Will be describedMS described above2Carrying out carbonization reaction on the polydopamine compound in inert gas atmosphere to obtain MS2A carbon composite;
(3) The MS is connected to the mobile station2The/carbon compound is in second contact with KOH solution, and then is subjected to first drying to obtain KOH/MS2a carbon mixture;
(4) The KOH/MS is added2heat treating the/carbon mixture to obtain M2A C/carbon nanosheet composite;
Wherein M is an Mo element and/or a W element.
5. The method according to claim 4, wherein, in step (1), the base is selected from at least one of tris (hydroxymethyl) aminomethane, aqueous ammonia, and tetrabutylammonium hydroxide.
6. The method of claim 4, wherein the conditions of the first contacting comprise: the temperature is 15-35 ℃, and the time is 10-40 h;
Preferably, the dopamine source is selected from at least one of dopamine hydrochloride, dopamine and dopamine hydrobromide.
7. the method according to claim 4, wherein, in the step (2), the carbonization reaction conditions include: the temperature is 500-750 ℃, and the time is 0.5-8 h; preferably the temperature is 550-650 ℃, and the time is 0.5-5 h;
Preferably, the inert gas is selected from N2At least one of Ar and He.
8. The method of claim 4, wherein, in step (3), the MS2the mass ratio of the dosage of the/carbon compound to the KOH in the KOH solution is 1: (1.5-4.5), preferably 1: (2-4);
Preferably, the first drying condition includes: the temperature is 50-250 ℃ and the time is 2-10 h.
9. The method according to claim 4, wherein, in step (4), the conditions of the heat treatment include: the temperature is 700 ℃ and 1000 ℃, and the time is 0.2-4 h; preferably, the temperature is 750-900 ℃, and the time is 0.5-1.5 h;
Preferably, the washing is water washing and/or dilute hydrochloric acid washing.
10. M as claimed in claim 1 or 22c/carbon nanoplatelet composites and/or M prepared by the method of any of claims 4-92The C/carbon nanosheet composite material is applied to the field of electro-catalysis hydrogen evolution as a catalyst, wherein M is Mo element and/or W element.
Technical Field
The invention relates to the field of electrocatalytic materials, in particular to M2C/carbon nanosheet composite material and preparation method and application thereof.
Background
environmental pollution and energy crisis have become major problems to be solved for sustainable development. The key point for solving the problem is to find a clean renewable energy source to replace non-renewable fossil fuel which can generate greenhouse gas. Hydrogen production by electrocatalytic decomposition of water is considered an effective solution.
At present, the catalyst for electrocatalytic hydrogen evolution mainly adopts a Pt-containing noble metal electrocatalyst. But their use is limited by the high price of precious metals due to their scarce reserves. Therefore, the development of a non-noble metal electrocatalyst with low price and abundant reserves is of great significance.
So far, transition metal based composite electrocatalysts (such as transition metal sulfides, carbides, nitrides, phosphides, oxides and hydroxides) are widely used for electrocatalytic hydrogen production. Among them, molybdenum carbide has attracted much interest due to its electronic structure similar to that of Pt. The electrocatalytic properties of molybdenum carbide are mainly based on the exposure of the catalytically active area and good electrical conductivity. However, the existing molybdenum carbide synthesis methods all require high temperature, and the method can cause particle aggregation, so that the specific surface area is smaller, the catalytic activity area is reduced, and the catalytic performance is reduced. To reduce particle agglomeration, some have used a substrate material and molybdenum carbide to form a composite material, but this approach has limited effect on the increase in the active catalytic area and performance of the catalyst.
Therefore, there is a need for an electrocatalytic material for electrocatalytic hydrogen evolution having a high specific surface area and having a large number of catalytically active areas.
Disclosure of Invention
One of the objects of the present invention is to overcome the problem of agglomeration of molybdenum carbide particles present in the prior art preparation processes.
The second purpose of the invention is to provide a composite electrocatalytic material which has large specific surface area and electrochemical active area, more active sites and stronger electrocatalytic hydrogen evolution capability.
In order to achieve the above object, a first aspect of the present invention provides an M2A C/carbon nanoplate composite, the composite comprising a porous carbon nanoplate matrix, and M grown on the porous carbon nanoplate matrix2C particles, wherein M is Mo element and/or W element.
In a second aspect of the invention, there is provided a process for preparing M2A method of C/carbon nanoplatelet composites, the method comprising the steps of:
(1) Will MS2First contacting with dopamine source and base to form MS2Polydopamine complexes;
(2) The MS is connected to the mobile station2carrying out carbonization reaction on the polydopamine compound in inert gas atmosphere to obtain MS2A carbon composite;
(3) The MS is connected to the mobile station2The/carbon compound is in second contact with KOH solution, and then is subjected to first drying to obtain KOH/MS2A carbon mixture;
(4) The KOH/MS is added2Heat treating the/carbon mixture to obtain M2A C/carbon nanosheet composite;
wherein M is an Mo element and/or a W element.
In a third aspect of the invention there is provided a compound according to the first aspect of the invention2C/carbon nanosheet composite or M prepared by the method of the second aspect of the present invention2The C/carbon nanosheet composite material is applied to the field of electro-catalysis hydrogen evolution as a catalyst, wherein M is Mo element and/or W element.
in a fourth aspect of the invention there is provided M according to the third aspect of the invention2C/carbon nanosheet composite or M prepared by the method of the second aspect of the present invention2The C/carbon nanosheet composite material is applied to the field of electro-catalysis hydrogen evolution as a catalyst, wherein M is Mo element and/or W element.
In a fifth aspect, the present invention provides an electrocatalytic hydrogen evolution process using M according to the first aspect of the invention2C/carbon nanosheet composite and/or M produced by the method of the second aspect of the present invention2The C/carbon nano-sheet composite material is used as a catalyst.
M of the invention2The C/carbon nanosheet composite material has a large specific surface area and an electrochemical active area, and can expose more active sites, so that the electro-catalytic hydrogen evolution capacity of the catalyst is greatly enhanced. In a preferred embodiment, the hydrogen evolution overpotential of the molybdenum carbide/carbon nanosheet composite of the present invention is up to 93 mV.
M of the invention2c/carbonThe preparation method of the nano-sheet composite material overcomes the problem of aggregation of molybdenum carbide particles, the used raw materials are rich in reserves and low in price, the reaction conditions are mild, and the obtained composite material catalyst has a large specific surface area and an electrochemical active area, can expose more active sites and has a high electro-catalytic hydrogen evolution capacity.
Drawings
Fig. 1 is an XRD spectrum of molybdenum carbide/carbon nanosheet composite a1 provided in example 1 of the present invention;
Fig. 2 is an SEM photograph of molybdenum carbide/carbon nanosheet composite a1 provided in example 1 of the present invention;
Fig. 3 is a TEM photograph of a molybdenum carbide/carbon nanosheet composite a1 provided in example 1 of the present invention;
FIG. 4 is an SEM photograph of the molybdenum carbide/carbon nanosheet composite D1 obtained in comparative example 1;
Fig. 5 is a polarization curve (LSV) curve of the electrocatalytic hydrogen evolution performance of the molybdenum carbide/carbon nanosheet composite material a1 provided in example 1 of the present invention.
Detailed Description
The endpoints of the ranges and any values disclosed herein are not limited to the precise range or value, and such ranges or values should be understood to encompass values close to those ranges or values. For ranges of values, between the endpoints of each of the ranges and the individual points, and between the individual points may be combined with each other to give one or more new ranges of values, and these ranges of values should be considered as specifically disclosed herein.
The invention provides in a first aspect a method for producing a compound2A C/carbon nanoplate composite, the composite comprising a porous carbon nanoplate matrix, and M grown on the porous carbon nanoplate matrix2c particles, wherein M is Mo element and/or W element.
Herein, "M" is2C/carbon nanosheet composite "refers to M2And C, growing the particles on the porous carbon nanosheet substrate to form the composite material.
According to the composite material of the present invention, preferably, the polyThe length of the porous carbon nanoplatelets substrate is 1-10 μm, for example 2 μm. Preferably, M2The particle size of the C particles is not more than 70nm, preferably 1-50 nm.
As used herein, the term "length" refers to the longest distance between two points on the porous carbon nanoplatelet substrate. The "particle size" refers to the equivalent particle size of the measured particle, that is, when the physical property of the measured particle is most similar to a homogeneous sphere with a certain diameter, the diameter of the sphere is taken as the equivalent particle size of the measured particle.
It can be seen from Scanning Electron Microscope (SEM) photographs (with a scale of 10 μm, as shown in fig. 2) that the molybdenum carbide/carbon nanosheet composite prepared according to one embodiment of the present invention exhibits an obvious lamellar structure. The molybdenum carbide particles can be seen from the Transmission Electron Microscope (TEM) photograph (500 nm scale, as shown in FIG. 3).
according to the composite material of the invention, the specific surface area of the composite material is preferably 1000-1600m2/g, preferably 1350-2(ii)/g, the average pore diameter is 1-10 nm. The specific surface area, i.e., BET specific surface area, is measured by the BET low temperature nitrogen adsorption method.
Preferably, the electrochemical active area of the composite material is 400-700m2G, preferably 500-700m2(ii) in terms of/g. The electrochemical active area is obtained by measuring the electric double layer capacitance through cyclic voltammetry.
In a preferred embodiment, M is used2The total weight of the C/carbon nano sheet composite material is taken as a reference, M2the content of C particles is 10-60 wt%, and the content of the porous carbon nanosheet substrate is 40-90 wt%; preferably M2The content of the C particles is 30-50 wt%, and the content of the porous carbon nanosheet substrate is 50-70 wt%.
In a preferred embodiment, M is Mo, Mo being Mo2the crystalline phase of the C particles is beta-Mo2And C, having a hexagonal lattice structure.
In a second aspect of the invention, there is provided the preparation of M2A method of C/carbon nanoplatelet composites, the method comprising the steps of:
(1) Will MS2With dopamine source, alkaliRow first contact, forming MS2Polydopamine complexes;
(2) The MS is connected to the mobile station2carrying out carbonization reaction on the polydopamine compound in inert gas atmosphere to obtain MS2A carbon composite;
(3) The MS is connected to the mobile station2The/carbon compound is in second contact with KOH solution, and then is subjected to first drying to obtain KOH/MS2a carbon mixture;
(4) The KOH/MS is added2Heat treating the/carbon mixture to obtain M2A C/carbon nanosheet composite;
Wherein M is an Mo element and/or a W element.
As used herein, the term "dopamine source" refers to a substance used to provide dopamine, an effective raw material.
According to the method of the present invention, in step (1), the MS is performed2Making first contact with dopamine and base, wherein dopamine is polymerized to form polydopamine under catalysis of base, and the Polydopamine (PDA) is coated on MS2The surface was formed into a PDA film. In a preferred embodiment, the MS2Is added in the form of particles, and the particle diameter of the particles is 0.01-10 μm.
in a preferred embodiment, the MS2The mass ratio of the dosage (calculated by M element) to the dosage (calculated by C element) of dopamine is (0.5-4): 1, in order to obtain better catalytic performance, the ratio of (2-2.5): 1.
To control the MS2A poly-dopamine film synthesized on the surface and controlling the dopamine polymerization rate, preferably, the base is at least one selected from the group consisting of tris (hydroxymethyl) aminomethane, ammonia water, and tetrabutylammonium hydroxide. The base is used in an amount such that MS is present2The pH of the mixture with dopamine and alkali is 8-10. The base can be obtained commercially, for example, usingbase。
Preferably, the conditions of the first contacting include: the temperature is 15-35 ℃, and the time is 10-40 h; preferably at a temperature of 20-30 ℃ for 12-24 h.
in a preferred embodiment, the dopamine source is selected from at least one of dopamine hydrochloride, dopamine and dopamine hydrobromide.
According to the method of the present invention, in step (2), the MS is used2The polydopamine compound is subjected to carbonization reaction in inert gas atmosphere, and is wrapped in MS in the carbonization reaction process2The poly-dopamine film on the surface is converted into a carbon film.
in order to further obtain a higher specific surface area of the resulting carbon film, preferably, the carbonization reaction conditions include: the temperature is 500-750 ℃, and the time is 0.5-8 h; preferably, the temperature is 550-700 ℃ and the time is 0.5-5 h.
In the carbonization process, in order to prevent the carbon from being oxidized while further obtaining a higher specific surface area, preferably, the inert gas is selected from N2and at least one of Ar or He.
according to the method of the present invention, in step (3), the MS is performed2The/carbon compound is in second contact with KOH solution, and then is subjected to first drying to obtain KOH/MS2A carbon mixture.
In order to further increase the specific surface area of the catalyst and simultaneously further increase the catalytic performance of the catalyst, preferably, MS2The mass ratio of the dosage of the/carbon compound to the KOH in the KOH solution is 1: (1.5-4.5), preferably 1: (2-4).
Preferably, the conditions of the second contacting include: the temperature is 0-40 ℃.
The first drying step is to obtain KOH/MS2In order to further remove water without other side reactions, the first drying condition preferably includes: the temperature is 50-250 ℃ and the time is 2-10 h.
According to the method of the present invention, in the step (4), the KOH/MS is added2The/carbon mixture is subjected to a heat treatment during which two reactions, one activation of KOH and one M, actually take place2C formation reaction, the inventors of the present invention conducted several experiments, and the experimental studies showed that the two reactionsthe reaction is as follows:
MoS2+4KOH→2K2S+MoO2+2H2O；
2MoO2+C+4H2→Mo2C+4H2O；
in order to further improve the catalytic performance of the catalyst, preferably, the heat treatment conditions include: the temperature is 700 ℃ and 1000 ℃, and the time is 0.2-4 h; preferably at a temperature of 750 ℃ and 900 ℃ for 0.5-1.5 h.
In order to remove K produced during the reaction2CO3Water soluble salt is added, the obtained product is preferably washed and dried for the second time to obtain M with impurities removed2c/carbon nano-sheet composite material. Preferably, the washing is water washing and/or dilute hydrochloric acid washing, preferably deionized water washing. The number of washing times can be adjusted according to actual requirements. In order to ensure that moisture is removed without undesirable chemical reactions occurring, preferably, the conditions of the second drying include: the temperature is 50-100 ℃ and the time is 10-24 h.
In a third aspect, the invention provides M prepared by the method of the second aspect2the C/carbon nano-sheet composite material is characterized in that M is Mo element and/or W element.
Preferably, the composite material comprises a porous carbon nanosheet substrate, and M grown on the porous carbon nanosheet substrate2And C, particles. Preferably, the length of the porous carbon nanoplatelet matrix is 1-10 μm, for example 2 μm. Preferably, M2The particle size of the C particles is not more than 70nm, preferably 1-50 nm.
As used herein, the term "length" refers to the longest distance between two points in the plane of the porous carbon nanoplatelet substrate. In this context, the term "particle size" refers to the equivalent particle size of the measured particle, i.e., when the physical property of the measured particle is closest to a homogeneous sphere having a certain diameter, the diameter of the sphere is taken as the equivalent particle size of the measured particle.
It can be seen from Scanning Electron Microscope (SEM) photographs (with a scale of 10 μm, as shown in fig. 2) that the molybdenum carbide/carbon nanosheet composite prepared according to one embodiment of the present invention exhibits a distinct lamellar structure. The molybdenum carbide particles can be seen from the Transmission Electron Microscope (TEM) photograph (500 nm scale, as shown in FIG. 3).
According to the composite material of the invention, the specific surface area of the composite material is preferably 1000-1600m2(ii)/g, the average pore diameter is 1-10 nm. The specific surface area, i.e., BET specific surface area, is measured by the BET low temperature nitrogen adsorption method.
preferably, the electrochemical active area of the composite material is 400-700m2(ii) in terms of/g. The electrochemical active area is obtained by measuring the electric double layer capacitance through cyclic voltammetry.
In a preferred embodiment, M2In the C/carbon nano-sheet composite material, M is added2The total weight of the C/carbon nano sheet composite material is taken as a reference, M2the content of C particles is 10-60 wt%, and the content of the porous carbon nanosheet substrate is 40-90 wt%; preferably M2The content of the C particles is 30-50 wt%, and the content of the porous carbon nanosheet substrate is 50-70 wt%.
in a preferred embodiment, M is Mo, Mo being Mo2The crystalline phase of C is beta-Mo2And C, having a hexagonal lattice structure.
in a fourth aspect of the invention there is provided M according to the third aspect of the invention2C/carbon nanosheet composite or M prepared by the method of the second aspect of the present invention2The C/carbon nanosheet composite material is applied to the field of electro-catalysis hydrogen evolution as a catalyst, wherein M is Mo element and/or W element.
Will be described in this application as M2When the C/carbon nano-sheet composite material is used as a catalyst in the field of electrocatalytic hydrogen evolution, the C/carbon nano-sheet composite material has a remarkably lower hydrogen evolution overpotential, for example, the current density is 10mA/cm2When the catalyst is used, the overpotential for hydrogen evolution is not more than 300mv, even less than 200mv, which means that more hydrogen can be generated under the same electric energy, and the catalyst has a remarkably good catalytic effect.
Fifth aspect of the inventionThere is provided an electrocatalytic hydrogen evolution process using M according to the first aspect of the invention2C/carbon nanoplatelet composites and/or M made by the method of the second aspect of the invention2The C/carbon nano-sheet composite material is used as a catalyst.
M of the invention2The beneficial effects of the C/carbon nanosheet composite can be summarized as follows:
(1) The composite material does not contain noble metal elements, the price of the contained transition metal elements is low, and the reserves in the crust are relatively rich;
(2) The carbon nano-sheet with a porous structure forms a composite material, so that the conductivity and the electrochemical active area of the catalyst are increased, and the performance of the catalyst is improved;
(3) The composite material has good catalytic performance and stability when being used for electro-catalytic hydrogen evolution, overcomes the aggregation problem of a molybdenum carbide electro-catalyst, improves the electro-catalytic hydrogen evolution efficiency, has the hydrogen evolution overpotential not more than 300mv, even less than 200mv, and has good application prospect.
The present invention will be described in detail below by way of examples.
The following examples, comparative examples relate to test methods:
(1) Test for catalytic Performance
The test was performed using a standard three-electrode system with catalyst samples dropped onto a glassy carbon electrode as the working electrode (with catalyst loading of 0.305mg cm-2) The Ag/AgCl electrode is used as a reference electrode, and the carbon rod is used as a counter electrode for testing. At 5mV s-1The sweep speed of (2) was tested to obtain a polarization curve.
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