CeFe-coated C / NF self-supporting electro-catalytic material, preparation method and application

Abstract

The invention relates to the technical field of electro-catalytic materials, in particular to a CeFe-coated C / NF self-supporting electro-catalytic material and a preparation method and application thereof.The preparation method comprises the steps that ferric salt, terephthalic acid and benzoic acid are dissolved in a mixed solution of N, N-dimethylformamide, ethyl alcohol and water, then a first hydrothermal reaction and calcination are conducted, and derivative powder of an Fe-based MOF precursor MIL-53 (Fe) is obtained; the preparation method comprises the following steps: adding derivative powder of a Fe-based MOF precursor MIL-53 (Fe), cerous nitrate hexahydrate and polyvinylpyrrolidone into a mixed solution of ethanol, ethylene glycol and water, and uniformly mixing to obtain a mixed solution; the foamed nickel is put into the mixed solution for a second hydrothermal reaction, and the CeFe-coated C / NF self-supporting electro-catalytic material is obtained. According to the method, monocarboxylic acid benzoic acid is adopted as a structure regulating agent to obtain an ultrathin nanosheet-shaped Fe-based MOF precursor MIL-53 (Fe) nanosheet with a controllable microstructure and a controllable crystal structure, the nanosheet is calcined and then loaded with CeO2 in situ, and the problems that in the prior art, an electrocatalyst is high in manufacturing cost, high in overpotential and low in catalytic activity are solved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of electrocatalytic materials, in particular to a CeFe@C / NF self-supporting electrocatalytic material, a preparation method and applications. BACKGROUND

[0002] To meet the challenge of the global population growth, it is a vital task to ensure the sustainable green energy supply. In recent years, as the main source of traditional energy, fossil fuels have many problems, such as greenhouse gases produced by combustion and limited reserves. With long-term exploitation, the reserves of fossil fuels are decreasing, and the demand for alternative energy is gradually increasing. Therefore, it is crucial to find an environmentally friendly, efficient and sustainable energy solution. Hydrogen energy, as a kind of secondary clean energy, has many advantages such as green environmental protection, high energy utilization rate and sustainable circulation, and is expected to replace traditional fossil fuels in the future, so it has attracted widespread attention.

[0003] In the development and application of hydrogen energy, hydrogen production technology is the core link. At present, the common hydrogen production methods mainly include fossil fuel reform hydrogen production, biomass hydrogen production and water decomposition hydrogen production, etc. Fossil fuel reform hydrogen production is one of the methods widely used in current industry. This method mainly generates hydrogen and carbon dioxide by reacting fossil fuels (such as natural gas, coal, etc.) with steam under high temperature and high pressure. Although this hydrogen production method is relatively mature, the yield is large, and it can meet the current demand of some industries for hydrogen, but it has a serious drawback, that is, it still emits a large amount of greenhouse gases such as carbon dioxide in the process of hydrogen production, which is contrary to the development concept of green energy and cannot fundamentally solve the environmental problems caused by fossil fuels. Moreover, with the increasingly strict global carbon emission restrictions, the development space of fossil fuel reform hydrogen production will be greatly limited. Biomass hydrogen production is a technology that uses biomass (such as crop straw, forestry waste, algae, etc.) to convert hydrogen through biological or thermochemical methods. Biomass, as a renewable resource, has the advantages of wide sources and wide distribution. The carbon dioxide produced in the process of biomass hydrogen production can be reabsorbed by biomass through photosynthesis during growth, realizing the recycling of carbon and reducing greenhouse gas emissions to a certain extent. However, the biomass hydrogen production technology is still in the research and development stage, and there are some technical problems to be solved. For example, the pretreatment process of biomass is complex and costly; the efficiency of biological hydrogen production is low, and the reaction speed is slow; some harmful substances may be produced in the process of thermochemical hydrogen production, which need to be further treated, etc. These factors limit the large-scale application and promotion of biomass hydrogen production technology. Water decomposition hydrogen production is considered to be a promising hydrogen production technology due to its green and efficient advantages. Water decomposition hydrogen production is mainly achieved through electrochemical methods, that is, using electric energy to drive water molecules to undergo oxidation-reduction reaction on the electrode to decompose into oxygen and hydrogen. This process not only has no pollution, but also can be driven by electric power provided by renewable energy (such as solar energy, wind energy, water energy, etc.), realizing truly green hydrogen production. Electrocatalytic hydrogen evolution is the key step of water decomposition hydrogen production, which has the advantages of green, environmental protection, high efficiency and sustainability. In the process of electrocatalytic hydrogen evolution, water molecules are reduced to generate hydrogen on the cathode under the action of catalyst, while water molecules are oxidized to generate oxygen on the anode. The whole process does not produce any pollutants, and the energy conversion efficiency is high. With the continuous development of electrochemical theory and material science, electrocatalytic hydrogen evolution technology has made significant progress, and researchers have developed various types of electrocatalysts, laying a foundation for the development of water decomposition hydrogen production technology.

[0004] The overpotential refers to a difference between an electrode potential deviating from a thermodynamic equilibrium potential in an actual electrochemical reaction in order to enable the reaction to proceed smoothly. The existence of the overpotential means that additional energy is required to drive the electrochemical reaction, which not only increases the energy consumption of the hydrogen production process, reduces the energy conversion efficiency, but also causes the working voltage of the electrolytic cell to increase, which puts higher requirements on the equipment and materials of the electrolytic cell, and increases the equipment cost and operation cost. At present, many existing electrocatalysts require a high overpotential to achieve a certain reaction rate when catalyzing the water decomposition reaction, which makes the electrocatalytic hydrogen evolution technology face the dilemma of low energy utilization efficiency and increased cost in practical application. The catalytic activity is one of the important indicators for measuring the performance of the electrocatalyst, which directly determines the rate and efficiency of the electrochemical reaction. At present, most of the electrocatalysts with excellent performance contain noble metal elements such as platinum (Pt) and palladium (Pd). These noble metals are rare in the earth's crust, difficult to mine, and expensive, so with the continuous development of the hydrogen energy industry, the demand for electrocatalysts will increase significantly. If the noble metal-based electrocatalyst is continued to be relied on, the cost of hydrogen production will be high, and the economic and sustainability goals of green energy cannot be achieved. The catalytic activity of the existing electrocatalyst is still low. The low catalytic activity means that under the same conditions, the rate of the electrocatalytic hydrogen evolution reaction is slow, and the amount of hydrogen produced per unit time is small, which cannot meet the demand of large-scale hydrogen production.

[0005] In summary, the existing electrocatalyst has the technical problems of high manufacturing cost, high overpotential and low catalytic activity, which seriously hinders the large-scale application of the electrocatalytic hydrogen evolution technology and the development of the hydrogen energy industry. Therefore, finding an electrocatalyst with low cost, low overpotential and high catalytic activity has become the research focus and difficulty in the field of electrocatalytic hydrogen evolution, and is also the key to promoting the development of green energy and realizing sustainable energy supply. SUMMARY

[0006] In view of the problems of high manufacturing cost, high overpotential and low catalytic activity of the electrocatalyst in the prior art, the present application provides a CeFe@C / NF self-supporting electrocatalytic material.

[0007] To achieve the above-mentioned purpose, the following technical solutions are adopted in the present application: The present application provides a preparation method of a CeFe@C / NF self-supporting electrocatalytic material, comprising: dissolving the iron salt, terephthalic acid and benzoic acid in a mixed solution of N,N-dimethylformamide, ethanol and water, then performing a first hydrothermal reaction, calcining to obtain a derivative powder of Fe-based MOF precursor MIL-53(Fe); Derivative powder of Fe-based MOF precursor MIL-53(Fe), cerium nitrate hexahydrate and polyvinylpyrrolidone are added into a mixed solution of ethanol, ethylene glycol and water, mixed uniformly to obtain a mixed solution; The foam nickel is placed into the mixed solution to perform a second hydrothermal reaction to obtain a CeFe@C / NF self-supporting electrocatalytic material.

[0008] Optionally, the iron salt is FeCl3, FeCl3 6H2O, Fe(NO3)3 6H2O or Fe(NO3)3 9H2O.

[0009] Optionally, the molar ratio of the iron salt, terephthalic acid and benzoic acid is 1:(0.1-5):(0.01-0.5); the volume ratio of N,N-dimethylformamide, ethanol and water in the mixed solution of N,N-dimethylformamide, ethanol and water is 1:(0.01-0.1):(0.01-0.1).

[0010] Optionally, the temperature of the first hydrothermal reaction is 120-180 DEG C, and the time is 2-6 h.

[0011] Optionally, the specific conditions of calcination are as follows: under an argon or nitrogen atmosphere, the temperature is increased from room temperature to 500-900 DEG C at a temperature increasing rate of 2-10 DEG C / min, and the calcination time is 1.5-5 h.

[0012] Optionally, the molar ratio of the derivative powder of Fe-based MOF precursor MIL-53(Fe), cerium nitrate hexahydrate and polyvinylpyrrolidone is 1:(0.1-1):(0.0001-0.01); the volume ratio of ethanol, ethylene glycol and water in the mixed solution of ethanol, ethylene glycol and water is 1:(0.1-1):(0.1-1).

[0013] Optionally, the temperature of the second hydrothermal reaction is 120-180 DEG C, and the reaction time is 5-24 h.

[0014] Optionally, the foam nickel is pretreated by the following process: The foam nickel is sequentially and completely immersed into acetone, a 3-6 mol / L hydrochloric acid solution, deionized water and anhydrous ethanol, and is respectively ultrasonically treated for 15-30 min, and is dried to complete the pretreatment of the foam nickel.

[0015] The application further provides a CeFe@C / NF self-supporting electrocatalytic material, which is prepared by the above method for preparing a CeFe@C / NF self-supporting electrocatalytic material, and the current density of the CeFe@C / NF self-supporting electrocatalytic material is 100 mA / cm2 Under the condition, the overpotential of hydrogen evolution is 150-186 mV, and the overpotential of oxygen evolution is 368-447 mV.

[0016] The application of the CeFe@C / NF self-supporting electrocatalytic material in water decomposition for hydrogen production.

[0017] Compared with the prior art, the application has the following beneficial effects: The application provides a preparation method of a CeFe@C / NF self-supporting electrocatalytic material. The method synthesizes a derivative powder of a Fe-based MOF precursor MIL-53(Fe) nanosheet by performing a simple hydrothermal reaction and calcination on iron salt, terephthalic acid and benzoic acid as raw materials. The monobasic carboxylic acid benzoic acid is selected as a structure regulator, which can replace terephthalic acid to adjust the microstructure of MIL-53(Fe) and the coordination environment of metal Fe sites. Through a "replacement-inhibition" process, the growth of MIL-53(Fe) material in the c-axis direction is inhibited, and finally the ultrathin nanosheet-shaped Fe-based MOF precursor MIL-53(Fe) nanosheet with controllable microstructure and crystal structure is obtained. The unsaturated coordination metal center serves as an active site, which is helpful to enhance the catalytic activity of the material on OH -The adsorption capacity of the material is improved, so that the material can interact with the reactants more effectively in the electrocatalytic process, thereby improving the efficiency of the electrocatalytic reaction. Calcination can realize the thermodynamic-kinetic synergistic control of the MIL-53(Fe) material, and then realize the synchronous optimization of the carbon matrix structure and the metal site, because in the pyrolysis process, the organic ligand in the MOF is decomposed, gas is released to form a PC skeleton, which significantly improves the conductivity of the skeleton, facilitates the rapid transmission of electrons in the material, and thus promotes the electrocatalytic reaction. The carbon-based material after pyrolysis effectively exposes or contacts more active sites due to its unique layered structure and high specific surface area, thereby further improving the reaction kinetics, enabling the material to participate in more reaction processes in the electrocatalytic reaction, and making the electrocatalytic reaction more efficient. Secondly, the self-supporting electrocatalytic material is prepared by loading the derived carbon-based material of Fe-based MOF precursor MIL-53(Fe) and CeO2 in situ on the foam nickel substrate. Among them, cerium is the most abundant element in rare earth elements, so the source of cerium dioxide is very rich, and cerium dioxide has the characteristics of non-toxicity, simple preparation method, high oxygen storage capacity and stable chemical properties. Compared with traditional titanium dioxide electrocatalysts, cerium dioxide has more active sites due to its easy oxidation-reduction characteristics, thereby facilitating the electrocatalytic reaction. The preparation of CeFe@C / NF composite material is beneficial to the formation of composite interface, which can ensure fast electron transmission and regulate metal site activity, promote the adsorption of reactants on the surface of the catalyst and inside the hole, increase the electrocatalytic active site, reduce the electrocatalytic overpotential, and ultimately ensure the efficient and stable electrocatalytic reaction, and reduce energy loss. The method has the advantages of simple process and low cost, and has excellent electrocatalytic performance for HER in alkaline conditions.

[0018] The application also provides a CeFe@C / NF self-supporting electrocatalytic material prepared by the preparation method of the CeFe@C / NF self-supporting electrocatalytic material. 2 Under the condition of a current density of 100 mA / cm The lower hydrogen evolution overpotential means that the material as a catalyst can drive the hydrogen evolution reaction with a relatively small applied voltage in the process of electrolytic water hydrogen production. Compared with traditional electrocatalytic materials, this greatly reduces energy consumption and improves the energy conversion efficiency of hydrogen production, so that more hydrogen can be produced under the same energy input, which has important economic significance and practical application value for large-scale industrialized hydrogen production.

[0019] The CeFe@C / NF self-supporting electrocatalytic material is applied in water decomposition for hydrogen production. Due to the low overpotential and high catalytic efficiency of the CeFe@C / NF self-supporting electrocatalytic material, the application of the CeFe@C / NF self-supporting electrocatalytic material in water electrolysis for hydrogen production helps to promote the development of clean energy, realizes efficient and environmentally friendly hydrogen production process, and provides strong support for the sustainable energy development in the future. BRIEF DESCRIPTION OF DRAWINGS

[0020] Figure 1 A preparation method flowchart of the CeFe@C / NF self-supporting electrocatalytic material.

[0021] Figure 2 An XRD pattern of the CeFe@C / NF self-supporting electrocatalytic material prepared in Example 1 of the present application.

[0022] Figure 3 SEM images of the CeFe@C / NF self-supporting electrocatalytic material prepared in Example 1 of the present application, wherein (a) is an SEM image under 5k magnification, and (b) is an SEM image under 2k magnification.

[0023] Figure 4 Electrocatalytic test results of the CeFe@C / NF self-supporting electrocatalytic material prepared in Example 1 of the present application, wherein (a) is the hydrogen evolution overpotential, and (b) is the oxygen evolution overpotential. DETAILED DESCRIPTION

[0024] In order for those skilled in the art to understand the characteristics and effects of the present application, the following is a general description and definition of the terms and phrases mentioned in the specification and claims. Unless otherwise specified, all technical and scientific words used in the text are the usual meanings understood by those skilled in the art for the present application, and in case of conflict, the definition in the specification shall prevail.

[0025] Theories or mechanisms described and disclosed herein, whether correct or not, should not be considered limiting the scope of the present application, i.e., the present application can be practiced without any particular theory or mechanism.

[0026] In this text, all features defined in the form of numerical range or percentage range, such as numerical value, quantity, content and concentration, are for the sake of brevity and convenience. Therefore, the description of numerical range or percentage range should be considered to have covered and specifically disclosed all possible sub-ranges and individual numerical values within the range (including integers and fractions).

[0027] In the present specification, unless particularly stated, "comprising", "including", "containing", "having" or like terms means "consisting of and "consisting essentially of" for example, "A comprising a" encompasses "A consisting of a and "A consisting essentially of a".

[0028] In the present specification, all possible combinations of the various technical features described in the various embodiments or examples are not described in order to simplify the description. Therefore, the various technical features in the various embodiments or examples can be combined arbitrarily as long as there is no contradiction in the combination, and all possible combinations should be considered as falling within the scope of the present specification.

[0029] The present application will be further described with reference to the following specific examples. It is to be understood that these examples are provided by way of illustration only and should not be construed as limiting the scope of the present application. Furthermore, those skilled in the art will appreciate that various modifications and adaptations of the present application can be made in light of the content of the present disclosure, and that such modifications and adaptations are intended to fall within the scope of the appended claims.

[0030] In the following examples, the apparatuses and instruments of the art are used. In the following examples, the experimental methods not specifically described are usually performed according to the conventional conditions, or according to the conditions suggested by the manufacturers. In the following examples, various raw materials are used, and unless otherwise specified, the conventional commercially available products are used, and the specifications are the conventional specifications in the art. In the specification of the present application and in the following examples, unless otherwise specified, "%" means the percentage by weight, "parts" means the parts by weight, and the ratio means the ratio by weight.

[0031] The present application will be further described with reference to the following specific examples. It is to be understood that these examples are provided by way of illustration only and should not be construed as limiting the scope of the present application. Furthermore, those skilled in the art will appreciate that various modifications and adaptations of the present application can be made in light of the content of the present disclosure, and that such modifications and adaptations are intended to fall within the scope of the appended claims.

[0032] Reference is made to Figure 1 The present application discloses a preparation method of a CeFe@C / NF self-supporting electrocatalytic material, comprising: S1: dissolving iron salt, terephthalic acid and benzoic acid in a mixed solution of N,N-dimethylformamide, ethanol and water, then performing a first hydrothermal reaction, calcining to obtain a derivative powder of Fe-based MOF precursor MIL-53(Fe); wherein the iron salt is FeCl3, FeCl3 6H2O, Fe(NO3)3 6H2O or Fe(NO3)3 9H2O; the molar ratio of the iron salt, terephthalic acid and benzoic acid is 1:(0.1-5):(0.01-0.5), wherein the molar concentration of the iron salt is 0.01-10 mol / L; the volume ratio of N,N-dimethylformamide, ethanol and water in the mixed solution of N,N-dimethylformamide, ethanol and water is 1:(0.01-0.1):(0.01-0.1); the temperature of the first hydrothermal reaction is 120-180℃, and the time is 2-6 h; the specific conditions of calcination are as follows: under the atmosphere of argon or nitrogen, the temperature is raised from room temperature to 500-900℃ at a temperature raising rate of 2-10℃ / min, and the calcination time is 1.5-5 h.

[0033] S2: a derivative powder of Fe-based MOF precursor MIL-53(Fe), cerium nitrate hexahydrate and polyvinylpyrrolidone are added into a mixed solution of ethanol, ethylene glycol and water, and mixed uniformly to obtain a mixed solution; wherein the molar ratio of the derivative powder of Fe-based MOF precursor MIL-53(Fe), cerium nitrate hexahydrate and polyvinylpyrrolidone is 1:(0.1-1):(0.0001-0.01); the volume ratio of ethanol, ethylene glycol and water in the mixed solution of ethanol, ethylene glycol and water is 1:(0.1-1):(0.1-1); S3: the nickel foam is placed into the mixed solution for the second hydrothermal reaction to obtain a CeFe@C / NF self-supporting electrocatalytic material; wherein, the nickel foam needs to be pretreated before use, and the pretreatment process is as follows: the nickel foam is completely immersed into acetone, 3-6 mol / L hydrochloric acid solution, deionized water and anhydrous ethanol in sequence, and is ultrasonically treated for 15-30 min respectively, and is dried to complete the pretreatment of the nickel foam; the temperature of the second hydrothermal reaction is 120-180℃, and the reaction time is 5-24 h.

[0034] The application also provides a CeFe@C / NF self-supporting electrocatalytic material prepared by the above-mentioned preparation method of the CeFe@C / NF self-supporting electrocatalytic material, and the CeFe@C / NF self-supporting electrocatalytic material has a current density of 100 mA / cm 2 Under the condition, the corresponding overpotential of hydrogen evolution is 150-186 mV, and the overpotential of oxygen evolution is 368-447 mV. The lower overpotential of hydrogen evolution means that in the process of electrolytic water hydrogen production, the material as a catalyst can drive the hydrogen evolution reaction with a relatively small applied voltage. Compared with traditional electrocatalytic materials, this greatly reduces energy consumption, improves the energy conversion efficiency of hydrogen production, and enables more hydrogen to be produced under the same energy input, which has important economic significance and practical application value for large-scale industrialized hydrogen production.

[0035] The CeFe@C / NF self-supporting electrocatalytic material is applied in water decomposition for hydrogen production. Due to the low overpotential and high catalytic efficiency of the CeFe@C / NF self-supporting electrocatalytic material, the application of the CeFe@C / NF self-supporting electrocatalytic material in water electrolysis for hydrogen production helps to promote the development of clean energy, realizes an efficient and environmentally friendly hydrogen production process, and provides strong support for the future sustainable energy development.

[0036] Example 1 The quantitative FeCl3, terephthalic acid and benzoic acid were weighed respectively, and then the iron salt, terephthalic acid and benzoic acid were dissolved in a mixed solution of 35 mL of N,N-dimethylformamide, 2.5 mL of anhydrous ethanol and 2.5 mL of deionized water, and the prepared solution was magnetically stirred at room temperature for 30 min to obtain a uniformly mixed solution A. Among them, the concentration of FeCl3 is 0.05 mol / L, the concentration of terephthalic acid is 0.2 mol / L, and the concentration of benzoic acid is 0.01 mol / L. Solution A was loaded into a polytetrafluoroethylene reaction kettle liner, and placed in an oven for solution heat reaction, wherein the temperature of the oven was 150℃, the reaction time was 120 min, after the reaction was completed, the solution in the reaction kettle was centrifuged, and after centrifugation was completed, the supernatant was poured out, and then the centrifugation was washed with anhydrous ethanol and deionized water several times, dried at 100℃ for 180 min, and then placed in a tube furnace for calcination. The tube furnace was heated to 800℃ at a heating rate of 5℃ / min under a nitrogen atmosphere from room temperature, and the calcination time was 240 min. After calcination was completed, it was cooled to room temperature to obtain a solid, which was ground in a mortar to obtain a Fe-based MOF precursor MIL-53(Fe) derivative powder.

[0037] The quantitative Fe-based MOF precursor MIL-53(Fe) derivative powder, cerium nitrate hexahydrate and polyvinylpyrrolidone were weighed respectively, and then the Fe-based MOF precursor MIL-53(Fe) derivative powder, cerium nitrate hexahydrate and polyvinylpyrrolidone were dissolved in a mixed solution composed of 20 mL of anhydrous ethanol, 10 mL of ethylene glycol and 10 mL of deionized water to obtain a uniformly mixed solution. Among them, the concentration of the Fe-based MOF precursor MIL-53(Fe) derivative powder is 0.04 mol / L, the concentration of cerium nitrate hexahydrate is 0.02 mol / L, and the concentration of polyvinylpyrrolidone is 0.00002 mol / L.

[0038] A suitable beaker was used to completely immerse nickel foam in acetone, 3 mol / L hydrochloric acid solution, deionized water, and anhydrous ethanol sequentially, and ultrasonically treated for 15 min each to obtain pretreated nickel foam. The pretreated nickel foam was then placed in a hydrothermal reactor containing the mixed solution and subjected to a hydrothermal reaction in an oven at 180℃ for 12 h. After the reaction, the mixture was cooled to room temperature to obtain nickel foam with CeFe@C growth. The CeFe@C-grown nickel foam was rinsed several times with anhydrous ethanol and deionized water, and then dried in a vacuum drying oven at 70℃ for 3 h to obtain CeFe@C / NF self-supporting electrocatalytic material.

[0039] XRD tests were performed on the CeFe@C / NF self-supporting electrocatalyst material prepared in this example. See [link to XRD analysis]. Figure 2 It can be seen that diffraction angles of 44.5°, 51.8°, and 76.3° correspond to the (111), (200), and (220) crystal planes of nickel foam (JCPDS No. 65-2865), respectively. Diffraction angles of 26.4°, 42.2°, and 44.4° correspond to characteristic peaks of C (JCPDS No. 41-1487); meanwhile, characteristic peaks of CeO2 (JCPDS No. 04-0593) appear at diffraction angles of 28.5°, 33.1°, and 47.5°, and characteristic peaks of Ce2O(CO3)2 appear at diffraction angles of 15.8°, 20.4°, and 23.8°. The presence of characteristic peaks for H2O (JCPDS No. 44-0617) and Fe3C (JCPDS No. 35-0772) at diffraction angles of 42.9°, 43.7°, and 44.9° indicates the successful synthesis of CeFe@C / NF self-supporting catalytic materials.

[0040] The CeFe@C / NF self-supporting electrocatalytic material prepared in this example was subjected to SEM testing, see [link to SEM]. Figure 3 It can be seen that the nanosheet-supported mesoporous microsphere structure CeFe@C obtained in this invention grows uniformly and densely in nickel foam.

[0041] See Figure 4 The electrocatalytic performance of the CeFe@C / NF self-supporting electrocatalytic material prepared in this embodiment (with the working electrode being the CeFe@C / NF self-supporting electrocatalytic material, the reference electrode being a saturated calomel electrode, the counter electrode being a graphite rod, and the electrolyte being a 1 M KOH alkaline solution) shows that the CeFe@C / NF self-supporting electrocatalytic material obtained in this invention exhibits an electrocatalytic efficiency of 100 mA / cm². 2 The corresponding hydrogen evolution and oxygen evolution overpotentials are 150 mV and 368 mV, respectively.

[0042] Example 2 Take the quantitative analysis of FeCl3 6H2O, terephthalic acid and benzoic acid, then dissolve the iron salt, terephthalic acid and benzoic acid in a mixed solution of 35 mL of N,N-dimethylformamide, 3 mL of anhydrous ethanol and 2 mL of deionized water, and magnetically stir the prepared solution at room temperature for 25 min to obtain a uniformly mixed solution A. Among them, the concentration of FeCl3 6H2O is 0.05 mol / L, the concentration of terephthalic acid is 0.1 mol / L, and the concentration of benzoic acid is 0.01 mol / L. Solution A is loaded into a polytetrafluoroethylene reactor liner and placed in an oven for solution heat reaction, wherein the temperature of the oven is 160°C and the reaction time is 300 min. After the reaction is completed, it is cooled to room temperature, the solution in the reactor is centrifuged, the supernatant is poured out after centrifugation, and the centrifugation is washed with anhydrous ethanol and deionized water several times, dried at 80°C for 240 min, and then calcined in a tube furnace, the tube furnace is heated from room temperature to 800°C at a heating rate of 4°C / min under a nitrogen atmosphere, and the calcination time is 180 min. After calcination, it is cooled to room temperature to obtain a solid, which is ground in a mortar to obtain a Fe-based MOF precursor MIL-53(Fe) derivative powder.

[0043] Take the quantitative analysis of FeCl3

[0044] Take a suitable beaker, and immerse the nickel foam into acetone, 4 mol / L hydrochloric acid solution, deionized water and anhydrous ethanol in sequence, and ultrasonic treat for 20 min respectively. Put the pretreated nickel foam into the hydrothermal reactor containing the mixed solution. Hydrothermal reaction is carried out by using an oven, and the temperature of the oven is 160°C and the reaction time is 10 h, to obtain the nickel foam with CeFe@C grown thereon. The nickel foam with CeFe@C grown thereon is washed with anhydrous ethanol and deionized water several times respectively, and then dried in a vacuum drying oven at 65°C for 3 h to obtain the CeFe@C / NF self-supporting electrocatalytic material.

[0045] The CeFe@C / NF obtained in the present example was tested by electrocatalysis. The current density of the CeFe@C / NF was 100 mA / cm 2 The corresponding hydrogen evolution and oxygen evolution overpotentials were 186 mV and 447 mV, respectively.

[0046] Example 3 A certain amount of Fe(NO3)3 6H2O, terephthalic acid and benzoic acid were weighed, and the iron salt, terephthalic acid and benzoic acid were dissolved in a mixed solution of 30 mL of N,N-dimethylformamide, 5 mL of anhydrous ethanol and 5 mL of deionized water, and the prepared solution was magnetically stirred at room temperature for 20 min to obtain a uniformly mixed solution A. The concentration of Fe(NO3)3 6H2O was 0.05 mol / L, the concentration of terephthalic acid was 0.3 mol / L, and the concentration of benzoic acid was 0.01 mol / L. Solution A was loaded into a polytetrafluoroethylene reactor liner, and the solution was subjected to a solution heat reaction in an oven, wherein the temperature of the oven was 180°C, and the reaction time was 240 min. After the reaction was completed, the solution in the reactor was cooled to room temperature, centrifuged, and the supernatant was poured out. The centrifuged solution was washed several times with anhydrous ethanol and deionized water, and then dried at 60°C for 300 min. The dried solution was calcined in a tube furnace under a nitrogen atmosphere at a heating rate of 4°C / min from room temperature to 600°C. The calcination time was 300 min, and the calcined product was cooled to room temperature. The solid product was ground in a mortar to obtain a Fe-based MOF precursor MIL-53(Fe) derivative powder.

[0047] A certain amount of Fe-based MOF precursor MIL-53(Fe) derivative powder, cerium nitrate hexahydrate and polyvinylpyrrolidone were weighed, and then the Fe-based MOF precursor MIL-53(Fe) derivative powder, cerium nitrate hexahydrate and polyvinylpyrrolidone were dissolved in a mixed solution of 25 mL of anhydrous ethanol, 7.5 mL of ethylene glycol and 7.5 mL of deionized water. The prepared solution was magnetically stirred at room temperature for 150 min to obtain a uniformly mixed solution. The concentration of the Fe-based MOF precursor MIL-53(Fe) derivative powder was 0.04 mol / L, the concentration of cerium nitrate hexahydrate was 0.06 mol / L, and the concentration of polyvinylpyrrolidone was 0.00006 mol / L.

[0048] Take a suitable beaker, and then immerse the nickel foam into acetone, 5 mol / L hydrochloric acid solution, deionized water and anhydrous ethanol in sequence, and ultrasonic treatment for 25 min respectively. Put the pretreated nickel foam into a hydrothermal reactor containing a mixed solution. Hydrothermal reaction is carried out by using an oven, and the temperature of the oven is 170℃, and the reaction time is 8 h, and then the nickel foam with CeFe@C grown thereon is obtained. The nickel foam with CeFe@C grown thereon is washed with anhydrous ethanol and deionized water several times respectively, and then is placed into a vacuum drying oven at 50℃ for drying for 3 h, and then the CeFe@C / NF self-supporting electrocatalytic material is obtained.

[0049] It is tested that the CeFe@C / NF obtained in the embodiment has a current density of 100 mA / cm 2 The corresponding hydrogen evolution and oxygen evolution overpotential are 155 mV and 377 mV respectively.

[0050] Example 4 A certain amount of Fe(NO3)3 9H2O, terephthalic acid and benzoic acid are weighed respectively, and then the iron salt, terephthalic acid and benzoic acid are dissolved in a mixed solution of 25 mL N,N-dimethylformamide, 7.5 mL anhydrous ethanol and 7.5 mL deionized water, and the prepared solution is magnetically stirred at room temperature for 40 min to obtain a uniformly mixed solution A. Among them, the concentration of Fe(NO3)3 9H2O is 0.05 mol / L, the concentration of terephthalic acid is 0.2 mol / L, and the concentration of benzoic acid is 0.025 mol / L. Solution A is loaded into a polytetrafluoroethylene reactor inner liner, and a solution heat reaction is carried out in an oven, wherein the temperature of the oven is 150℃, and the reaction time is 300 min. After the reaction is completed, the solution in the reactor is cooled to room temperature, centrifuged, and the supernatant is poured out. Then, the centrifuged solution is washed with anhydrous ethanol and deionized water several times, and then is dried at 70℃ for 120 min. Then, the sample is calcined in a tube furnace under a nitrogen atmosphere at a heating rate of 6℃ / min from room temperature to 900℃, and the calcination time is 360 min. After the calcination is completed, the sample is cooled to room temperature, and then is ground in a mortar to obtain a Fe-based MOF precursor MIL-53(Fe) derivative powder.

[0051] The derivative powder of the Fe-based MOF precursor MIL-53(Fe) for quantitative analysis, cerium nitrate hexahydrate and polyvinylpyrrolidone are weighed respectively, and then the derivative powder of the Fe-based MOF precursor MIL-53(Fe), the cerium nitrate hexahydrate and the polyvinylpyrrolidone are dissolved in a mixed solution composed of 25 mL of anhydrous ethanol, 8 mL of ethylene glycol and 7 mL of deionized water, and the prepared solution is magnetically stirred at room temperature for 210 min to obtain a mixed solution uniformly mixed. The concentration of the derivative powder of the Fe-based MOF precursor MIL-53(Fe) is 0.04 mol / L, the concentration of the cerium nitrate hexahydrate is 0.1 mol / L, and the concentration of the polyvinylpyrrolidone is 0.0001 mol / L.

[0052] Suitable beakers are taken, and the nickel foam is completely immersed in acetone, 6 mol / L hydrochloric acid solution, deionized water and anhydrous ethanol in sequence, and is ultrasonically treated for 30 min respectively. The pretreated nickel foam is placed in a hydrothermal reaction kettle containing the mixed solution. Hydrothermal reaction is carried out by using an oven, the temperature of the oven is 180℃, and the reaction time is 16 h, so that the nickel foam with CeFe@C grown thereon is obtained. The nickel foam with CeFe@C grown thereon is washed with anhydrous ethanol and deionized water respectively for several times, and is placed in a vacuum drying box at 80℃ for drying for 5 h, so that the CeFe@C / NF self-supporting electrocatalytic material is obtained.

[0053] It is tested that the CeFe@C / NF obtained in the embodiment has a current density of 10 mA / cm 2 The corresponding hydrogen evolution and oxygen evolution overpotential are 163 mV and 380 mV respectively.

[0054] The above only describes the preferred embodiments of the present application, and does not use to limit the technical solutions of the present application in any way, and those skilled in the art should understand that the technical solutions can also be modified and replaced in several simple ways without departing from the spirit and principles of the present application, and these modifications and replacements also belong to the protection scope covered by the claims.

Claims

1. A method for preparing a CeFe@C / NF self-supporting electrocatalytic material, characterized in that, The method comprises the following steps: dissolving iron salt, terephthalic acid and benzoic acid in a mixed solution of N,N-dimethylformamide, ethanol and water, then performing a first hydrothermal reaction, and calcining to obtain a derivative powder of Fe-based MOF precursor MIL-53(Fe); adding the derivative powder of Fe-based MOF precursor MIL-53(Fe), cerium nitrate hexahydrate and polyvinylpyrrolidone into a mixed solution of ethanol, ethylene glycol and water, and uniformly mixing to obtain a mixed solution; immersing the nickel foam into the mixed solution to perform a second hydrothermal reaction, and obtaining a CeFe@C / NF self-supporting electrocatalytic material.

2. The preparation method of the CeFe@C / NF self-supporting electrocatalytic material according to claim 1, characterized in that, said iron salt is FeCl3, FeCl3 6H2O, Fe(NO3)3 6H2O or Fe(NO3)3 9H2O.

3. The preparation method of the CeFe@C / NF self-supporting electrocatalytic material according to claim 1, characterized in that, The molar ratio of the iron salt, terephthalic acid and benzoic acid is 1:(0.1-5):(0.01-0.5); and the volume ratio of N,N-dimethylformamide, ethanol and water in the mixed solution of N,N-dimethylformamide, ethanol and water is 1:(0.01-0.1):(0.01-0.1).

4. The preparation method of the CeFe@C / NF self-supporting electrocatalytic material according to claim 1, characterized in that, The temperature of the first hydrothermal reaction is 120-180 DEG C, and the time is 2-6 h.

5. The method for preparing the CeFe@C / NF self-supporting electrocatalytic material according to claim 1, characterized in that, The specific conditions of the calcination are as follows: under an argon or nitrogen atmosphere, the temperature is increased from room temperature to 500-900 DEG C at a temperature increasing rate of 2-10 DEG C / min, and the calcination time is 1.5-5 h.

6. The method for preparing the CeFe@C / NF self-supporting electrocatalytic material according to claim 1, characterized in that, The molar ratio of the derivative powder of Fe-based MOF precursor MIL-53(Fe), cerium nitrate hexahydrate and polyvinylpyrrolidone is 1:(0.1-1):(0.0001-0.01); and the volume ratio of ethanol, ethylene glycol and water in the mixed solution of ethanol, ethylene glycol and water is 1:(0.1-1):(0.1-1).

7. The method for preparing the CeFe@C / NF self-supporting electrocatalytic material according to claim 1, characterized in that, The temperature of the second hydrothermal reaction is 120-180 DEG C, and the reaction time is 5-24 h. 8.The method of claim 1, wherein the CeFe@C / NF self-supporting electrocatalytic material is prepared by the following steps: (1) preparing a CeFe@C core-shell structure by a solvothermal method; (2) preparing a CeFe@C / NF self-supporting electrocatalytic material by a hydrothermal method. The nickel foam is pretreated by the following process: immersing the nickel foam into acetone, 3-6 mol / L hydrochloric acid solution, deionized water and anhydrous ethanol in sequence, and respectively ultrasonic treating for 15-30 min, and drying to complete the pretreatment of the nickel foam.

9. A CeFe@C / NF self-supporting electrocatalytic material, characterized in that, Prepared by the method of any one of claims 1-8, the CeFe@C / NF self-supported electrocatalytic material has a current density of 100 mA / cm 2 Under the conditions, the corresponding overpotential of hydrogen evolution is 150-186 mV, and the overpotential of oxygen evolution is 368-447 mV.

10. The application of the CeFe@C / NF self-supporting electrocatalytic material in claim 9 in water decomposition for hydrogen production.

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