Preparation method and application of medium-entropy boride electrocatalyst FeNiSnMnAl-Bs / CC

Abstract

The invention discloses a medium-entropy boride electrocatalyst FeNiSnMnAl-Bs / CC as well as a preparation method and application thereof, and belongs to the technical field of electrochemical materials. The electrocatalyst is a medium-entropy iron-nickel-tin boride material (FeNiSnMnAl-Bs / CC) loaded on the surface of carbon cloth and containing a small amount of manganese and aluminum. The FeNiSnMnAl-Bs / CC medium entropy boride catalyst is prepared on the surface of the carbon cloth through a potentiostatic method, the catalyst has high alkaline water electrolysis performance, and when the current density reaches 100 mAcm <-2 >, the required hydrogen evolution overpotential and the required oxygen evolution overpotential are 147 mV and 262 mV respectively. When the electrocatalyst is used as a cathode and an anode of an electrolytic bath, the current density of 20 mAcm <-2 > can be obtained only by the electrolytic voltage of 1.59 V, which is superior to that of most electrocatalysts reported at present. The preparation method is mild, simple to operate, stable in current output, long in service life, low in cost, high in efficiency and suitable for practical application and popularization.

Description

Technical Field

[0001] The invention belongs to the technical field of electrochemical materials, and in particular relates to a preparation method of a medium-entropy boride electrocatalyst FeNiSnMnAl-Bs / CC and application thereof. Background Art

[0002] With the rapid development of clean energy technology around the world, water electrolysis plays an important role in the field of renewable energy. The design of efficient catalysts is the key to improving the efficiency of water electrolysis. However, the slow kinetics of hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) limit the practical application of water electrolysis. This has prompted researchers to develop efficient electrocatalysts with lower overpotentials. Currently, platinum-based and ruthenium-based precious metal catalysts are the benchmark electrocatalysts for HER and OER, respectively. However, low abundance and high cost significantly restrict their large-scale application. In addition, most reported electrocatalysts fail to exhibit excellent HER and OER performance simultaneously in the same electrolyte solution. Therefore, there is an urgent need to construct cost-effective bifunctional non-precious metal electrocatalysts.

[0003] Among non-precious metal-based catalysts, transition metal borides are widely used due to their excellent stability. However, most of the reported transition metal borides are single metal or binary metal-based catalysts, and their small composition limits their performance adjustment and wide application to a certain extent. In recent years, medium / high entropy materials (M / HEMs) containing three or more metal elements have attracted the attention of researchers due to their unique properties. Medium / high entropy materials have high elemental diversity and component disorder, which leads to rich active sites on their surface. In addition, the synergistic effect between multiple metal elements can optimize the electronic structure, which is crucial to improving the efficiency of HER and OER. Research and exploration of the reasonable adjustment of the types and proportions of different metal elements in medium / high entropy materials and the optimization of the adsorption / desorption behavior of reaction intermediates to significantly improve the catalytic activity of HER and OER is a current research hotspot and direction. Summary of the invention

[0004] The present invention aims at the problems in the prior art. A medium-entropy boride material containing a small amount of doping elements is prepared by a simple method. The high stability of the boride and the synergistic effect between metal elements are combined to adjust the electronic configuration and surface morphology, thereby enhancing its HER, OER and overall water splitting performance, providing an effective strategy for large-scale water electrolysis to produce hydrogen.

[0005] In order to achieve the above technical objectives, the technical solution adopted by the present invention is: A method for preparing a medium-entropy boride electrocatalyst FeNiSnMnAl-Bs / CC comprises the following steps: (1) Carbon cloth treatment: Place the carbon cloth in a reactor, add concentrated nitric acid and heat to react, then take it out, rinse it with ultrapure water, and dry it for later use; (2) preparing an electroplating solution: dissolving citric acid, a boron source, an iron source, a nickel source, a manganese source, a tin source and an aluminum source in ultrapure water, stirring and mixing to obtain an electroplating solution; (3) Electrodeposition: Using a saturated calomel electrode as a reference electrode, a platinum wire as a counter electrode, and the carbon cloth treated in step (1) as a working electrode, constant potential deposition is performed in the electroplating solution prepared in step (2), the deposition potential is -1.5 V, the deposition time is 2 h, and after the deposition is completed, the catalyst is dried to obtain the medium entropy boride electrocatalyst FeNiSnMnAl-Bs / CC.

[0006] Furthermore, in step (1), the size of the carbon cloth is 2 cm×3 cm×0.36 μm, and the amount of concentrated nitric acid used is 40 mL.

[0007] Furthermore, in step (1), the reaction temperature is 120° C. and the reaction time is 2 h.

[0008] Furthermore, in step (2), the boron source is sodium tetraborate decahydrate; the iron source is ferrous chloride tetrahydrate; the nickel source is nickel chloride hexahydrate; the manganese source is manganese chloride tetrahydrate; the tin source is stannous chloride dihydrate; and the aluminum source is aluminum chloride.

[0009] Furthermore, in step (2), the molar ratio of citric acid, sodium tetraborate decahydrate, ferrous chloride tetrahydrate, nickel chloride hexahydrate, manganese chloride tetrahydrate, stannous chloride dihydrate and aluminum chloride is 6:8:1:1:1:1:1; and the dosage ratio of each raw material to ultrapure water is (6 mmol:8 mmol:1 mmol:1 mmol:1 mmol:1 mmol:1 mmol): 50 mL.

[0010] Furthermore, the stirring time in step (2) is 1 h.

[0011] All raw materials of the present invention are commercially available.

[0012] Beneficial Effects (1) In the electrocatalyst preparation method of the present invention, iron-nickel-tin-manganese-aluminum boride is in situ grown on the surface of carbon cloth by constant potential method to obtain an electrocatalyst with a special nanoflower-like morphology. Compared with the control material and the carbon cloth substrate, it has good alkaline hydrogen evolution and oxygen evolution catalytic activity. When the current density reaches 100 mA‧cm -2 When used as the cathode and anode of an electrolytic cell, an electrolysis voltage of only 1.59 V was required to obtain 20 mA‧cm -2 The current density is better than that of most catalysts reported so far.

[0013] (2) Compared with the prior art, the preparation method of the present invention is mild and easy to operate. By combining the high stability of boride with the synergistic effect between the metal elements, the electronic configuration is adjusted so that the catalyst has a higher conductivity and a lower overpotential for hydrogen and oxygen evolution under alkaline conditions, and can be used as an efficient alkaline water splitting bifunctional electrocatalyst material. The obtained catalyst has high overall activity, stable current output, long service life, low cost and high efficiency, and is suitable for practical application and promotion. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 Characterization diagram of the medium entropy boride FeNiSnMnAl-Bs / CC obtained in Example 1 of the present invention, wherein (a) is a scanning electron microscope image of FeNiSnMnAl-Bs / CC, (b) is a transmission electron microscope image of FeNiSnMnAl-Bs, (c) is the molar fraction ratio of five metal elements in FeNiSnMnAl-Bs, and (d) is an element distribution diagram of FeNiSnMnAl-Bs; Figure 2 The electrocatalytic activity diagrams of the embodiments of the present invention, the comparative examples, the substrate carbon cloth (CC), and the precious metal catalyst Pt-based (HER), and Ru-based catalyst (OER) in 1 M KOH alkaline electrolyte, wherein (a) is the HER polarization curve of the electrode, and (b) is the OER polarization curve of the electrode; Figure 3 Comparison of polarization curves of the medium-entropy boride electrocatalyst FeNiSnMnAl-Bs / CC obtained in Example 1 of the present invention before and after 500 (HER, a) and 1000 (OER, b) cyclic voltammetry in 1 M KOH electrolyte; Figure 4 The figures are scanning electron microscope images of the catalysts obtained in the comparative examples, wherein (a) is the morphology image of the catalyst FeNiSn-Bs / CC obtained in comparative example 1, (b) is the morphology image of the catalyst FeNiSnMn-Bs / CC obtained in comparative example 2, and (c) is the morphology image of the catalyst FeNiSnAl-Bs / CC obtained in comparative example 3.

[0015] Figure 5 The graphs are the performance test diagrams of the complete water splitting of the medium entropy boride FeNiSnMnAl-Bs / CC obtained in Example 1 of the present invention, wherein (a) is a schematic diagram of the assembled two-electrode electrolytic cell, (b) is the polarization curves in different electrolytes, and (c) is a 25-hour durability test in 1 M KOH. DETAILED DESCRIPTION

[0016] The technical solution of the present invention is further described below in conjunction with specific embodiments, but is not limited thereto.

[0017] Example 1 A method for preparing a medium-entropy boride electrocatalyst FeNiSnMnAl-Bs / CC comprises the following steps: (1) Carbon cloth treatment: Place carbon cloth (2 cm × 3 cm × 0.36 μm) in a reactor, add 40 mL of concentrated nitric acid, heat at 120 °C for 2 h, then take it out, rinse it with ultrapure water, and dry it for later use; (2) preparing an electroplating solution: 6 mmol of citric acid, 8 mmol of sodium tetraborate decahydrate, 1 mmol of ferrous chloride tetrahydrate, 1 mmol of nickel chloride hexahydrate, 1 mmol of manganese chloride tetrahydrate, 1 mmol of stannous chloride dihydrate and 1 mmol of aluminum chloride were dissolved in 50 mL of ultrapure water and stirred for 1 h to obtain an electroplating solution; (3) Electrodeposition: A saturated calomel electrode is used as a reference electrode, a platinum wire is used as a counter electrode, and the carbon cloth treated in step (1) is used as a working electrode. Constant potential deposition is carried out in the electroplating solution prepared in step (2). The deposition potential is -1.5 V and the deposition time is 2 h. After the deposition is completed, drying is performed to prepare the medium-entropy boride electrocatalyst FeNiSnMnAl-Bs / CC.

[0018] The reaction kettle in step (1) is a reaction kettle with a polytetrafluoroethylene lining; the amount of concentrated nitric acid used is 40 mL.

[0019] Morphological characterization The morphology of the FeNiSnMnAl-Bs / CC material obtained in Example 1 was characterized. The FeNiSnMnAl-Bs / CC medium entropy boride catalytic material was characterized using a scanning electron microscope. Figure 1 (a) is the scanning electron microscope image of FeNiSnMnAl-Bs / CC. Figure 1 It can be seen that FeNiSnMnAl-Bs boride nanomaterials grow evenly on the surface of carbon cloth (CC), forming a unique nanoflower-like structure. This microstructure makes the catalyst surface rough and provides a larger active surface area.

[0020] Figure 1 (b) is the transmission electron microscopy image of FeNiSnMnAl-Bs, which further confirms the size and rough surface of FeNiSnMnAl-Bs, which is consistent with the SEM results.

[0021] Figure 1 (c) is a ratio diagram of the five elements in FeNiSnMnAl-Bs, the element ratios of which are measured by inductively coupled plasma emission spectroscopy. Among them, Fe, Ni, and Sn are the main elements, and their molar fraction ratios meet the standards of medium entropy materials.

[0022] Figure 1(d) is the element distribution diagram of FeNiSnMnAl-Bs, showing that Fe, Ni, Sn, Mn, Al, B, and O elements are evenly distributed on the surface of the carbon cloth.

[0023] Electrochemical performance test The electrochemical performance test was carried out in a 1 M KOH solution with a standard three-electrode system. The FeNiSnMnAl-Bs / CC nanomaterial prepared in Example 1 was used as the working electrode, the Hg / HgO electrode was used as the reference electrode, and the graphite sheet was used as the counter electrode in a common electrolytic cell. The test was carried out using a Chenhua CHI760E electrochemical workstation. The test temperature was room temperature. The linear sweep voltammetry test was performed at 2 mV‧s −1 The scan rate is performed.

[0024] Figure 2 The electrocatalytic activity of FeNiSnMnAl-Bs / CC in 1 M KOH alkaline electrolyte was demonstrated. Figure 2 (a) is the HER polarization curve of the FeNiSnMnAl-Bs / CC electrode. It can be seen from the figure that the FeNiSnMnAl-Bs / CC electrode requires an overpotential of 83 and 147 mV to reach 10 and 100 mA‧cm -2 of current density. Figure 2 (b) is the OER polarization curve of FeNiSnMnAl-Bs / CC electrode. It can be seen from the figure that the FeNiSnMnAl-Bs electrode requires an overpotential of 195 and 262 mV to achieve 10 and 100 mA‧cm -2 of current density.

[0025] Figure 3 The polarization curves of the catalyst obtained in Example 1 of the present invention before and after 500 (HER, a) and 1000 (OER, b) cyclic voltammetry scans in 1 M KOH electrolyte are compared. As can be seen from the figure, after the cyclic voltammetry scan, the LSV curve of the catalyst is basically unchanged compared with that before the cyclic voltammetry scan, which proves that the prepared electrode can generate a stable current output and has a long service life.

[0026] Comparative Example 1 Compared with Example 1, the amount of elements is changed, that is, Mn and Al are not doped.

[0027] Preparation of medium-entropy boride electrocatalyst FeNiSn-Bs / CC: (1) Carbon cloth treatment: the same as in Example 1; (2) Dissolve 6 mmol of citric acid, 8 mmol of sodium tetraborate decahydrate, 1.67 mmol of ferrous chloride tetrahydrate, 1.67 mmol of nickel chloride hexahydrate, and 1.67 mmol of stannous chloride dihydrate in ultrapure water (50 mL) and stir for 1 h to obtain an electroplating solution; (3) Electrodeposition: Same as in Example 1, a saturated calomel electrode was used as a reference electrode and a platinum wire was used as a counter electrode to prepare a medium-entropy boride catalytic material, denoted as FeNiSn-Bs / CC.

[0028] Electrochemical performance test: The electrocatalytic test method is the same as that in Example 1. Figure 2 As shown, in the hydrogen evolution reaction, when the current reaches 10 and 100 mA‧cm -2 At current densities of 10 and 100 mA‧cm, FeNiSn-Bs / CC requires overpotentials of 162 and 251 mV, respectively; in the oxygen evolution reaction, the overpotentials of 10 and 100 mA‧cm -2 When the current density is 1.577 W / mV, FeNiSn-Bs / CC needs an overpotential of 199 and 292 mV. Compared with Example 1, the lack of Mn and Al doping has a greater impact on the hydrogen and oxygen evolution performance of the material.

[0029] Comparative Example 2 Compared with Example 1, the number of elements is changed, that is, only Mn is doped.

[0030] Preparation of medium-entropy boride electrocatalyst FeNiSnMn-Bs / CC: (1) Same as step (1) in Example 1 (2) Dissolve 6 mmol of citric acid, 8 mmol of sodium tetraborate decahydrate, 1.25 mmol of ferrous chloride tetrahydrate, 1.25 mmol of nickel chloride hexahydrate, 1.25 mmol of stannous chloride dihydrate, and 1.25 mmol of manganese chloride tetrahydrate in ultrapure water (50 mL) and stir for 1 h to obtain an electroplating solution.

[0031] (3) The same as step (3) in Example 1, a FeNiSnMn-Bs / CC catalytic material was obtained.

[0032] Electrochemical performance test: The electrocatalytic test method is the same as that in Example 1. Figure 2 As shown, in the hydrogen evolution reaction, the peak values ​​reached 10 and 100 mA‧cm -2 At current densities of 108 and 189 mV, FeNiSnMn-Bs / CC requires overpotentials of 10 and 100 mA‧cm for oxygen evolution reaction. -2When the current density is 2.5, FeNiSnMn-Bs / CC requires an overpotential of 207 and 293 mV. Compared with Example 1, it is shown that Mn doping can significantly improve the hydrogen and oxygen evolution performance of the material.

[0033] Comparative Example 3 Compared with Example 1, the number of elements is changed, that is, only Al doping is performed.

[0034] Preparation of medium-entropy boride electrocatalyst FeNiSnAl-Bs / CC: (1) Same as step (1) in Example 1 (2) Dissolve 6 mmol of citric acid, 8 mmol of sodium tetraborate decahydrate, 1.25 mmol of ferrous chloride tetrahydrate, 1.25 mmol of nickel chloride hexahydrate, 1.25 mmol of stannous chloride dihydrate, and 1.25 mmol of aluminum chloride in ultrapure water (50 mL) and stir for 1 h to obtain an electroplating solution.

[0035] (3) The same as step (3) in Example 1, a FeNiSnAl-Bs / CC catalytic material was obtained.

[0036] Electrochemical performance test: The electrocatalytic test method is the same as that in Example 1. Figure 2 As shown, in the hydrogen evolution reaction, the peak values ​​reached 10 and 100 mA‧cm -2 At current densities of 113 and 188 mV, FeNiSnAl-Bs / CC requires overpotentials of 10 and 100 mA‧cm for oxygen evolution reaction. -2 At current density, FeNiSnAl-Bs / CC requires overpotentials of 221 and 274 mV. Compared with Example 1, it is shown that Al doping can significantly improve the hydrogen and oxygen evolution performance of the material.

[0037] It can be seen from the electrochemical performance test results of Comparative Examples 1-3 that the simultaneous doping of Mn and Al elements has a synergistic effect on improving the electrochemical performance of the material, and can effectively enhance its HER and OER performance.

[0038] From the comparison of appearance Figure 4 It can be seen that the doping of Mn and Al elements not only significantly affects the electrochemical performance of the catalyst, but also has a substantial impact on the overall morphology of the catalyst. Figure 4 (a) is the morphology of the catalyst FeNiSn-Bs / CC obtained in Comparative Example 1, Figure 4 (b) is the morphology of the catalyst FeNiSnMn-Bs / CC obtained in Comparative Example 2, Figure 4(c) is a morphology picture of the catalyst FeNiSnAl-Bs / CC obtained in Comparative Example 3. The catalyst obtained in the comparative example did not form the same regular flower-like morphology as that in Example 1. The change in morphology is also one of the key factors affecting the performance of the catalyst.

[0039] In view of the excellent HER and OER electrocatalytic activity and stability of FeNiSnMnAl-Bs / CC, it was used as both anode and cathode of alkaline electrolyzer for overall water splitting. The experimental setup is as follows Figure 5 As shown in (a). In 1 M KOH solution, FeNiSnMnAl-Bs / CC‖FeNiSnMnAl-Bs / CC only needs 1.59 V electrolysis voltage to achieve 20 mA‧cm -2 To further evaluate the practical application potential of FeNiSnMnAl-Bs / CC, it was applied to simulated seawater (1 M KOH + 0.5 M NaCl) and alkaline natural seawater (1 M KOH + Seawater) for water electrolysis tests. The test results showed that in simulated seawater, FeNiSnMnAl-Bs / CC also showed good full water splitting performance, with an electrolysis voltage of only 1.61 V to achieve 20 mA cm -2 Although the potential in 1 M KOH + seawater increases due to the presence of impurities in natural seawater, FeNiSnMnAl-Bs / CC still exhibits excellent performance, achieving 20 mA cm at only 1.77 V. -2 The current density is 2.34 W / cm3. In addition, the electrochemical stability of FeNiSnMnAl-Bs / CC in 1 M KOH solution was studied by chronopotentiometry. After 25 hours of full water decomposition test, the potential hardly increased, indicating that FeNiSnMnAl-Bs / CC has good mechanical durability and electrochemical stability. These experimental results fully prove that FeNiSnMnAl-Bs / CC has potential application value in the actual process of hydrogen production by water electrolysis, especially in the field of hydrogen production by seawater electrolysis.

[0040] It should be noted that the above embodiments are only partial embodiments of the preferred methods of implementing the present invention, rather than all embodiments. Obviously, based on the above embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of the present invention.

Claims

1. A method for preparing a medium entropy boride electrocatalyst FeNiSnMnAl-Bs / CC, characterized in that: The method comprises the following steps: (1) Carbon cloth treatment: Place the carbon cloth in a reactor, add concentrated nitric acid and heat to react, then take it out, rinse it with ultrapure water, and dry it for later use; (2) preparing an electroplating solution: dissolving citric acid, a boron source, an iron source, a nickel source, a manganese source, a tin source and an aluminum source in ultrapure water, stirring and mixing to obtain an electroplating solution; (3) Electrodeposition: A saturated calomel electrode is used as a reference electrode, a platinum wire is used as a counter electrode, and the carbon cloth treated in step (1) is used as a working electrode. Constant potential deposition is carried out in the electroplating solution prepared in step (2). The deposition potential is -1.5 V and the deposition time is 2 h. After the deposition is completed, drying is performed to obtain the medium-entropy boride electrocatalyst FeNiSnMnAl-Bs / CC.

2. The method for preparing the medium entropy boride electrocatalyst FeNiSnMnAl-Bs / CC according to claim 1, characterized in that: In step (1), the reaction temperature is 120° C. and the reaction time is 2 h.

3. The method for preparing the medium entropy boride electrocatalyst FeNiSnMnAl-Bs / CC according to claim 1, characterized in that: In step (2), the boron source is sodium tetraborate decahydrate; the iron source is ferrous chloride tetrahydrate; the nickel source is nickel chloride hexahydrate; the manganese source is manganese chloride tetrahydrate; the tin source is stannous chloride dihydrate; and the aluminum source is aluminum chloride.

4. The method for preparing the medium entropy boride electrocatalyst FeNiSnMnAl-Bs / CC according to claim 3, characterized in that: Step (2) The molar ratio of citric acid, sodium tetraborate decahydrate, ferrous chloride tetrahydrate, nickel chloride hexahydrate, manganese chloride tetrahydrate, stannous chloride dihydrate and aluminum chloride is 6:8:1:1:1:1:1; the usage ratio of each raw material and ultrapure water is (6 mmol:8 mmol:1 mmol:1 mmol:1 mmol:1 mmol:1 mmol): 50 mL.

5. An electrocatalyst obtained by the preparation method according to any one of claims 1 to 4.

6. Use of an electrocatalyst obtained by the preparation method according to any one of claims 1 to 4 in electrolysis of water.

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