The disclosure herein relates to a general method for the synthesis of FeCoNiCu-based high-entropy alloy and their application for electrocatalytic water splitting, belonging to the technical field of preparation of composite materials.
Energy is an important material basis for human survival and development of civilization. The depletion of fossil fuels, such as oil, coal and natural gas, has forced people to seek for a new renewable energy source with abundant reserves. Hydrogen is considered to be one of the most promising green energies in the 21st century due to its high combustion heat, non-polluting combustion products and recyclability. Therefore, the development of hydrogen energy has become one of the research hotspots in the field of new energy. Although hydrogen is the most common element in nature (making up about 75% of the mass of the universe), it is mainly stored in water in the form of a compound and cannot be used directly. Therefore, the realization of a cheap, efficient and large-scale pathway for hydrogen production is the precondition for the development of hydrogen economy.
Hydrogen production from fossil fuels, hydrogen production from biomass, photocatalytic hydrogen production and hydrogen production by electrolysis of water are currently the main methods of hydrogen production. Among them, electrolysis of water is an important means to realize industrialized and cheap production of hydrogen, produced H2 and O2 have high purity, and the conversion rate is close to 100%. However, the electrocatalytic process requires high energy consumption, so a catalyst is needed to reduce cathodic overpotential. More importantly, the electrode materials for electrocatalytic water splitting in traditional industries mainly rely on the noble metal Pt and oxides thereof that have high price, small specific surface area and poor stability, which limits the industrialization process of electrocatalytic hydrogen production. Therefore, research and development of electrode materials for electrocatalytic water splitting with low cost, high efficiency and high stability are of great economic value and social significance.
In 2018, Hu Liangbing et al. from the University of Maryland proposed a five- to eight-element nanoscale high-entropy alloy prepared by carbothermal shock. This alloy maintains a single solid solution structure instead of being separated into different intermetallic phases. In high-entropy alloys, the large number of elements will maximize the configuration entropy, such that the alloys have unusual properties. However, the carbothermal shock method requires harsh conditions and is difficult for mass production, so finding a simple preparation method of nanoscale high-entropy alloys is one of the challenges at present.
Carbon nanofibers (CNFs) prepared by electrospinning have the advantages of high efficiency and stability, large specific surface area, high porosity, good adsorbability, etc. Compared with the traditional method, using the carbon nanofibers as a reaction vessel and support, alloy nanoparticles with good dispersion, uniform particle size and single phase can be prepared and can be used as a self-supporting catalytic electrode material for electrolysis of water.
In order to solve the problems of high cost, low catalytic activity, poor stability and poor conductivity of the existing catalytic material for electrolysis of water, the disclosure herein provides a FeCoNiCu-based high-entropy alloy catalytic material for electrolysis of water and a preparation method thereof. In the disclosure herein, electrospinning and high-temperature gas-assisted carbonization are used to prepare the carbon nanofiber-supported FeCoNiCu-based high-entropy alloy nanoparticles. The method is low in cost, and the obtained composite material has high hydrogen evolution and oxygen evolution activities under alkaline conditions, and has good stability.
A first objective of the disclosure herein is to provide a preparation method of a FeCoNiCu-based high-entropy alloy catalytic material for electrolysis of water (FeCoNiCuX HEA/CNFs, X=Sn, Mn, V, HEA=High entropy alloy). The preparation method includes the following steps:
(1) preparation of nanofibers containing four elements of Fe, Co, Ni and Cu and one or more elements of Sn, Mn and V: adding precursors of the elements of Fe, Co, Ni and Cu, a precursor (precursors) of one or more elements of the Sn, Mn and V, and a polymer material into a carbon fiber precursor solution, and stirring the mixture uniformly to obtain a mixed solution; and then spinning the mixed solution by electrospinning to obtain the nanofibers containing four elements of the Fe, Co, Ni and Cu and one or more elements of the Sn, Mn and V; and
(2) preparation of carbon nanofibers-supported FeCoNiCu-based high-entropy alloy nanoparticle electrocatalytic material: calcining the nanofibers prepared in step (1), and carrying out preoxidation by raising the temperature to 230° C.-280° C. at a heating rate of 10-30° C./min and holding the temperature for 1-3 hours in an air atmosphere; after the completion of the holding, carrying out carbonization by raising the temperature to 800-1200° C. at a rate of 10-30° C./min in an inert gas atmosphere and holding the temperature for 1-3 hours; and after the completion of the holding, cooling the nanofibers to room temperature under the protection of the inert gas to obtain the carbon nanofibers-supported FeCoNiCu-based high-entropy alloy nanoparticle catalytic material.
In an implementation of the disclosure herein, the precursor of the element Fe in step (1) is one or more of ferric chloride, ferric acetate, ferric nitrate and ferric acetylacetonate.
In an implementation of the disclosure herein, the precursor of the element Co in step (1) is one or more of cobalt chloride, cobalt acetate, cobalt nitrate and cobalt acetylacetonate.
In an implementation of the disclosure herein, the precursor of the element Ni in step (1) is one or more of nickel chloride, nickel acetate, nickel nitrate and nickel acetylacetonate.
In an implementation of the disclosure herein, the precursor of the element Cu in step (1) is one or more of cupric chloride, cupric acetate, cupric nitrate and cupric acetylacetonate.
In an implementation of the disclosure herein, the precursor of the element Sn in step (1) is one or both of stannic chloride and stannic tetraacetate.
In an implementation of the disclosure herein, the precursor of the element Mn in step (1) is one or more of manganese chloride and manganese acetate.
In an implementation of the disclosure herein, the precursor of the element V in step (1) is one or more of vanadium chloride, vanadium acetylacetonate and vanadyl acetylacetonate.
In an implementation of the disclosure herein, an addition amount of the precursor of the element Fe in step (1) is 0.1-0.5 mmol.
In an implementation of the disclosure herein, an addition amount of the precursor of the element Co in step (1) is 0.1-0.5 mmol.
In an implementation of the disclosure herein, an addition amount of the precursor of the element Ni in step (1) is 0.1-0.5 mmol.
In an implementation of the disclosure herein, an addition amount of the precursor of the element Cu in step (1) is 0.1-0.5 mmol.
In an implementation of the disclosure herein, an addition amount of the precursor of the element Sn in step (1) is 0.1-0.5 mmol.
In an implementation of the disclosure herein, an addition amount of the precursor of the element Mn in step (1) is 0.1-0.5 mmol.
In an implementation of the disclosure herein, an addition amount of the precursor of the element V in step (1) is 0.1-0.5 mmol.
In an implementation of the disclosure herein, a content of each of the four elements of the Fe, Co, Ni and Cu in the nanofibers in step (1) is 5-35 wt %, and a total content of the one or more elements of the Sn, Mn and V is 5-35 wt %.
In an implementation of the disclosure herein, a mole ratio of Fe:Co:Ni:Cu:one or more elements of the Sn, Mn and V in the nanofibers in step (1) is (1-2):(1-4):(1-4):(1-4):(1-4).
In an implementation of the disclosure herein, a mole ratio of Fe:Co:Ni:Cu:one or more elements of the Sn, Mn and V in the nanofibers in step (1) is 1:1:1:1:1.
In an implementation of the disclosure herein, the carbon fiber precursor in step (1) is any one of polyacrylonitrile, polyvinylpyrrolidone and polyvinyl alcohol, or a mixture of polyacrylonitrile and polyvinylpyrrolidone, and a mass ratio of the polyacrylonitrile to the polyvinylpyrrolidone in the mixture is 1:(0.5-2).
In an implementation of the disclosure herein, when the carbon fiber precursor is the polyacrylonitrile, a solvent in the carbon fiber precursor solution is N,N-dimethylformamide or dimethyl sulfoxide; when the carbon fiber precursor is the polyvinylpyrrolidone, a solvent in the carbon fiber precursor solution is N,N-dimethylformamide, dimethyl sulfoxide, water or ethanol; and when the carbon fiber precursor is the polyvinyl alcohol, a solvent in the carbon fiber precursor solution is water.
In an implementation of the disclosure herein, the polymer material added in step (1) is dicyandiamide.
In an implementation of the disclosure herein, conditions of the electrospinning in step (1) are as follows: a spinning voltage is controlled to 10-30 kV, a distance between a receiver and a needle is 15-30 cm, and a solution flow rate is 0.05-0.30 mL/min.
In an implementation of the disclosure herein, an amount of the FeCoNiCu-based high-entropy alloy nanoparticles supported on the carbon nanofibers in step (2) is 2-30 wt %.
In an implementation of the disclosure herein, the FeCoNiCu-based high-entropy alloy nanoparticles in step (2) have a size of 5-100 nm.
In an implementation of the disclosure herein, the carbon nanofiber material in step (2) have a diameter of 50-600 nm.
In an implementation of the disclosure herein, the calcining in step (2) includes putting the nanofibers prepared in step (1) into a corundum boat and calcining the nanofibers after placing the corundum boat in the middle of a tube furnace.
In an implementation of the disclosure herein, the inert gas in step (2) is one or both of argon and nitrogen.
In an implementation of the disclosure herein, the heating rate in step (2) is one or more of 10° C./min, 15° C./min, 20° C./min, 25° C./min and 30° C./min.
In an implementation of the disclosure herein, the heating rate in step (2) is 20° C./min.
In an implementation of the disclosure herein, a temperature of the carbonization in step (2) is 1000° C.
A second objective of the disclosure herein is to provide a FeCoNiCu-based high-entropy alloy catalytic material for electrolysis of water obtained by the above preparation method.
A third objective of the disclosure herein is to provide a method of hydrogen production by electrolysis of water. The method uses the above FeCoNiCu-based high-entropy alloy catalytic material for electrolysis of water.
The disclosure herein has the following beneficial effects:
(1) According to the FeCoNiCu-based high-entropy alloy prepared in the disclosure herein, multiple metal elements form a single solid solution. No longer limited by the properties of a single element and the position of a single element in the electrocatalysis volcano plot, the catalyst with high activity is formed.
(2) Using one-dimensional carbon nanofibers as the reaction vessel for induced growth of FeCoNiCu-based high-entropy alloy nanoparticles, a method of growing a high-entropy alloy using a one-dimensional carbon material is developed. Meanwhile, there exists strong electronic coupling between the one-dimensional carbon nanofiber material prepared by electrospinning and the high-entropy alloy nanoparticles, thereby further improving the catalytic activity.
(3) The FeCoNiCu-based high-entropy alloy catalytic material for electrolysis of water prepared in the disclosure herein has a high active area, which facilitates diffusion of the electrolyte. Besides, the carbon nanofibers can effectively protect the high-entropy alloy nanoparticles from erosion of the electrolyte, and endow the catalytic material with good stability. Meanwhile, the catalytic material prepared in the disclosure herein can be directly used as an electrode, and does not need to be coated to the electrode surface.
In order to better understand the disclosure herein, the contents of the disclosure herein will be further illustrated below in combination with the examples. However, the contents of the disclosure herein are not limited to the examples given below.
Preparation of FeCoNiCuSn HEA/CNFs Catalytic Material for Electrolysis of Water
(1) 0.1 mmol of ferric chloride, 0.1 mmol of cobalt chloride, 0.1 mmol of nickel chloride, 0.1 mmol of cupric chloride, 0.1 mmol of stannic chloride and 0.2 g of dicyandiamide were added to 30 g of polyacrylonitrile/N,N-dimethylformamide solution with a mass fraction of 18 wt %, the mixture was magnetically stirred uniformly, and then the solution was spun by electrospinning to obtain mixed nanofibers. A spinning voltage was controlled to 15 kV, a distance between a receiver and a spinning needle was 15 cm, and a solution flow rate was 0.05 mL/min.
(2) 0.5 g of the mixed nanofibers prepared in the step (1) was put into a corundum boat, and the corundum boat was placed in the middle of a tube furnace. The temperature was raised to 230° C. at a heating rate of 20° C./min and held for 3 hours in an air atmosphere. After the completion of the holding, carbonization was carried out by raising the temperature to 1000° C. at a rate of 20° C./min in an argon atmosphere and holding the temperature at 1000° C. for 3 hours. After the completion of the holding, the nanofibers were cooled to room temperature under the protection of the argon to obtain the catalytic material FeCoNiCuSn HEA/CNFs, recorded as FeCoNiCuSn−1/CNFs.
Morphology Characterization
A SEM image was taken on the obtained FeCoNiCuSn HEA/CNFs catalytic material for electrolysis of water.
Microstructure Characterization
Electrocatalytic Performance Test
Electrocatalysis was measured in 1 M KOH using a standard three-electrode system. Using the prepared FeCoNiCuSn high-entropy alloy nano material as a working electrode, a saturated calomel electrode as a reference electrode and a carbon rod as a counter electrode, the test was carried out in an ordinary electrolytic cell. The test was carried out using a Chenhua CHI660E electrochemical workstation. For the hydrogen evolution process, the polarization curve used linear sweep voltammetry, and the sweep voltage ranged from 0 to −0.6 V. For the oxygen evolution process, the sweep voltage ranged from 0 to 0.6 V. The Pt/C electrode and the IrO2 were purchased from Tianjin Aida Hengsheng Technology Development Co., Ltd. The test method was the same as the above, except that the test was carried out using the 20% Pt/C electrode and the IrO2 electrode as the working electrode.
Preparation of MnZnNiCuSn/CNFs Catalytic Material:
(1) 0.1 mmol of manganese chloride, 0.1 mmol of zinc chloride, 0.1 mmol of nickel chloride, 0.1 mmol of cupric chloride, 0.1 mmol of stannic chloride and 0.2 g of dicyandiamide were added to 30 g of polyacrylonitrile/N,N-dimethylformamide solution with a mass fraction of 18 wt %, the mixture was magnetically stirred uniformly, and then the solution was spun by electrospinning to obtain mixed nanofibers. A spinning voltage was controlled to 15 kV, a distance between a receiver and a spinning needle was 15 cm, and a solution flow rate was 0.2 mL/min.
(2) The MnZnNiCuSn/CNFs catalytic material was prepared in the same way as step (2) in Example 1.
Characterization test:
Preparation of FeCoNiCuSn-a/CNFs Catalytic Material:
(1) In the same way as step (1) of Example 1.
(2) 0.5 g of the prepared mixed nanofibers was put into a corundum boat, and the corundum boat was placed in the middle of a tube furnace. The temperature was raised to 230° C. at a heating rate of 5° C./min and held for 3 hours in an air atmosphere. After the completion of the holding, carbonization was carried out by raising the temperature to 1000° C. at a rate of 5° C./min in an argon atmosphere and holding the temperature at 1000° C. for 3 hours. After the completion of the holding, the nanofibers were cooled to room temperature under the protection of the argon to obtain the catalytic material, recorded as FeCoNiCuSn-a/CNFs.
Structural characterization test: The obtained FeCoNiCuSn-a/CNFs catalytic material was subjected to a structural test.
(1) 1 mmol of ferric chloride, 0.3 mmol of cobalt chloride, 0.2 mmol of nickel chloride, 0.6 mmol of cupric chloride, 0.1 mmol of stannic chloride and 0.2 g of dicyandiamide were added to 30 g of polyacrylonitrile/N,N-dimethylformamide solution with a mass fraction of 18 wt %, the mixture was magnetically stirred uniformly, and then the solution was spun by electrospinning to obtain mixed nanofibers. A spinning voltage was controlled to 15 kV, a distance between a receiver and a spinning needle was 15 cm, and a solution flow rate was 0.2 mL/min.
(2) In the same way as step (2) in Example 1, the obtained catalytic material was recorded as FeCoNiCuSn−2/CNFs.
Electrocatalytic test: The electrocatalytic test method was the same as the test method in Example 1.
For the oxygen evolution reaction, to reach a current density of 10 mA cm−2, the FeCoNiCuSn high-entropy alloy material in Example 1 only needs 110 mV, and the catalytic material prepared in this example needs 190 mV, which indicates that the percentages of elements also have a great influence on the oxygen evolution performance of the alloy material.
(1) 1 mmol of ferric chloride, 0.3 mmol of cobalt chloride, 0.2 mmol of nickel chloride, 0.6 mmol of cupric chloride and 0.1 mmol of stannic chloride were added to 30 g of polyacrylonitrile/N,N-dimethylformamide solution with a mass fraction of 18 wt %, the mixture was magnetically stirred uniformly, and then the solution was spun by electrospinning to obtain mixed nanofibers. A spinning voltage was controlled to 15 kV, a distance between a receiver and a spinning needle was 15 cm, and a solution flow rate was 0.2 mL/min.
(2) In the same way as step (2) in Example 1, the obtained catalytic material was recorded as FeCoNiCuSn−3/CNFs.
Electrocatalytic test: The electrocatalytic test method was the same as the test method in Example 1.
For the oxygen evolution reaction, to reach a current density of 500 mA cm−2, the FeCoNiCuSn high-entropy alloy material in Example 1 only needs 390 mV, and the catalytic material prepared in this example needs 540 mV, which indicates that the addition of the dicyandiamide also has a great influence on the oxygen evolution performance of the alloy material.
Although the disclosure herein has been disclosed as above in the preferred examples, it is not intended to limit the disclosure herein. Any person skilled in the art can make various changes and modifications without departing from the spirit and scope of the disclosure herein. Therefore, the protection scope of the disclosure herein should be as defined in the claims.
Number | Date | Country | |
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Parent | PCT/CN2019/129204 | Dec 2019 | US |
Child | 17532219 | US |