FeCoNiCuCr high-entropy alloy / carbon nanotube catalyst as well as preparation method and application thereof

Abstract

The invention discloses a FeCoNiCuCr high-entropy alloy / carbon nanotube catalyst and a preparation method and application thereof, the catalyst comprises a carbon nanotube carrier and a FeCoNiCuCr high-entropy alloy growing on the carbon nanotube carrier in situ, and the molar ratio of Fe to Co to Ni to Cu to Cr is (1-3): (1-2): 1: 1: 2. According to the technical scheme, the low-cost FeCoNiCuCr high-entropy alloy / carbon nanotube catalyst is adopted, the raw materials are cheap, the preparation process is simple, in OER, the initial potential can reach 1.5178 Vvs RHE, in ORR, the half-wave potential can reach 0.8471 Vvs RHE, the catalyst has the bifunctional oxygen electro-catalysis performance, the performance of the catalyst can be close to that of a precious metal-based catalyst, and the catalyst is suitable for large-scale industrial application.

Description

Technical Field

[0001] The present invention relates to the technical field of electrocatalysis, and particularly to an FeCoNiCuCr high-entropy alloy / carbon nanotube catalyst, a preparation method thereof, and an application thereof. Background Art

[0002] With the development of human society, the demand for energy has increased sharply. However, the excessive consumption of energy has sounded the alarm for mankind. People have made great efforts in developing green and sustainable energy, which has greatly promoted the progress of electrochemical energy storage and conversion technologies. Currently, lithium-ion batteries are leading in the energy storage field, but the cost of metallic lithium is relatively high, and lithium resources only exist in rare natural deposits and salt lakes. These disadvantages have hindered the future commercialization process and large-scale application of lithium-air batteries.

[0003] As a green energy conversion technology, zinc-air batteries are one of the best choices so far. Their unique features include relatively high specific energy (1370 Wh kg -1 ), safety, low cost, environmental friendliness, etc. However, due to their poor chargeability and low efficiency, their practical application is still a challenge. The main obstacle of zinc-air batteries is the inherently slow reaction kinetics of the air cathode, including the oxygen reduction reaction (ORR) during discharge and the oxygen evolution reaction (OER) during recharge.

[0004] Currently, the commonly used ORR and OER electrocatalysts are noble metal-based materials. However, the disadvantages of noble metal-based materials, such as high cost, low reserves, and low durability, have greatly hindered their large-scale application. In addition, noble metal-based materials usually only have a single catalytic function for ORR or OER, which will result in poor charging ability of zinc-air batteries prepared from noble metal-based materials.

[0005] High-entropy alloys are usually composed of a mixture of five or more metals. The metal elements in high-entropy alloys are composed of equal or nearly equal atomic ratios, and the content of each metal element is between 5% and 35%. Due to the high-entropy effect in thermodynamics, the lattice distortion effect in structure, the retarded diffusion effect in kinetics, and the cocktail effect in performance, high-entropy alloys are very easy to obtain a solid solution phase with high thermal stability and nanostructures or even amorphous structures. These structures and characteristics endow high-entropy alloys with features such as high strength, high wear resistance, and excellent corrosion resistance. At the same time, due to the lattice distortion effect of high-entropy alloys, more microdefects are formed, and the more stable solid solution structure formed by the high-entropy effect endows the material with superior catalytic performance and stability. In addition, the inherent surface complexity of HEAs also improves the performance of the catalyst, which may provide a nearly continuous adsorption energy distribution at the surface sites and can increase the proportion of the optimal active sites. In summary, HEAs can be considered as promising candidates for OER catalysts.

[0006] The patent application with the publication number CN114703459A discloses a noble-metal-free ultra-high-efficiency oxygen evolution high-entropy alloy nanoparticle electrocatalyst, its preparation method and application. By casting a high-entropy pre-alloy ingot FeCoNiMX into a high-entropy alloy target, and then using an ultra-high vacuum nanocluster deposition system, high-entropy alloy nanoparticles are generated on carbon cloth through magnetron sputtering; heat treatment is carried out at 500-900 °C to obtain a noble-metal-free ultra-high-efficiency oxygen evolution high-entropy alloy nanoparticle electrocatalyst Fe a Co b Ni c M d X e ; however, the catalyst provided by this scheme only has the OER function and does not have the ORR function. The patent application with the publication number CN115395031A discloses a high-entropy alloy ORR and OER catalytic material and its preparation method. The material is Mn a Co b Ru c Fe d Ni e -NC, where a∶b∶c∶d∶e = 1∶1∶1-2∶1∶1. Its preparation method includes the following steps: (1) Dissolve zinc acetate, cobalt salt, iron salt, nickel salt, ruthenium salt and manganese salt in water to form a homogeneous solution; (2) Dissolve 2-methylimidazole in water, add it to the solution in step (1), stir and react, and obtain a multi-metal organic framework material ZIF-(MnCoRuFeNi) after centrifugation, washing and drying; (3) Calcinate ZIF-(MnCoRuFeNi) in an inert atmosphere to obtain a MnCoRuFeNi-NC high-entropy alloy catalytic material. This catalytic material has excellent oxygen evolution and oxygen reduction functions by introducing a high-entropy alloy and nitrogen doping. However, ruthenium is contained in the catalytic material provided by this scheme. Ruthenium is expensive and scarce in output, which is not conducive to the industrialization of the catalyst.

[0007] Therefore, there is an urgent need to develop efficient and inexpensive ORR and OER bifunctional electrocatalysts. Summary of the Invention

[0008] In order to solve the above technical problems, the purpose of the present invention is to provide a FeCoNiCuCr high-entropy alloy / carbon nanotube catalyst, its preparation method and application. The FeCoNiCuCr high-entropy alloy / carbon nanotube catalyst has low cost and high catalytic activity, and has ORR and OER bifunctions.

[0009] In order to achieve the above purpose, the present invention adopts the following technical solutions:

[0010] A FeCoNiCuCr high-entropy alloy / carbon nanotube catalyst, comprising a carbon nanotube support and a FeCoNiCuCr high-entropy alloy in-situ grown on the carbon nanotube support, wherein the molar ratio of Fe:Co:Ni:Cu:Cr is 1-3:1-2:1:1:2.

[0011] A preparation method of the FeCoNiCuCr high-entropy alloy / carbon nanotube catalyst as described above, comprising the following steps:

[0012] (1) Dissolve ferric salt, nickel salt, cobalt salt, copper salt, chromium salt, 2,5-dihydroxyterephthalic acid (DHTA), and polyvinylpyrrolidone (PVP) in a mixed solution composed of ethanol (EtOH), N,N-dimethylformamide (DMF), and deionized water (DIW), ultrasonically dissolve, and then transfer to a reaction kettle for hydrothermal reaction to obtain FeCoNiCuCr@-MOF;

[0013] (2) Add carbon nanotubes to the reaction kettle solvent in step (1), and continue the hydrothermal reaction to obtain FeCoNiCuCr@CNTs-MOF;

[0014] (3) Centrifuge the FeCoNiCuCr@CNTs-MOF in step (2) with deionized water and ethanol for multiple times until the supernatant is clear. Vacuum dry the centrifuged FeCoNiCuCr@CNTs-MOF, add dicyandiamide, and perform heat treatment under an inert atmosphere to obtain the FeCoNiCuCr high-entropy alloy / carbon nanotube catalyst, denoted as FeCoNiCuCr@CNTs-HEA.

[0015] Preferably, in step (1), the ultrasonic dissolution time is 55-65 min, the temperature of the hydrothermal reaction is 110-130 °C, and the time is 12 h.

[0016] Preferably, in step (1), the ferric salt is Fe(NO3)3·9H2O, the nickel salt is Ni(NO3)2·6H2O, the cobalt salt is Co(NO3)2·6H2O, the copper salt is Cu(NO3)2·5H2O, and the chromium salt is Cr2(SO4)3.

[0017] Preferably, in step (1), the volume ratio of ethanol, N,N-dimethylformamide, and deionized water is 1.35:22.5:1.35; the ratio of nickel salt to ethanol is 0.2:1.35 mmol / mL, and the ratio of polyvinylpyrrolidone to ethanol is 0.5-1.0:

[0018] 1.35 g / mL.

[0019] Preferably, the molar ratio of iron salt, nickel salt, cobalt salt, copper salt, chromium salt and 2,5-dihydroxyterephthalic acid is 1-3:1-2:1:1:1:1.

[0020] Preferably, in step (2), the ratio of nickel salt to carbon nanotubes is 0.2:5-10 mol / g; the hydrothermal reaction is carried out at 110-130 °C for 12 h to obtain FeCoNiCuCr@CNTs-MOF.

[0021] Preferably, in step (3), the centrifuged FeCoNiCuCr@CNTs-MOF is dried in a vacuum oven at 80 °C for 12 h.

[0022] Preferably, in step (3), after the FeCoNiCuCr@CNTs-MOF is vacuum dried and dicyandiamide is added, it is placed in a nitrogen-filled tubular furnace and pretreated at 400 °C for 1 h, and then annealed at 800 °C for 2 h, and the heating rate is 5 °C·min -1 to obtain the FeCoNiCuCr high-entropy alloy / carbon nanotube catalyst.

[0023] Preferably, the mass ratio of FeCoNiCuCr@CNTs-MOF to dicyandiamide is 1:8.

[0024] Application of a FeCoNiCuCr high-entropy alloy / carbon nanotube catalyst as described above in OER / ORR of metal-air batteries.

[0025] Due to the adoption of the above technical solutions, the present invention has the following beneficial effects:

[0026] 1. Compared with catalysts containing noble metals (such as platinum, palladium, iridium, ruthenium, etc.), the low-cost FeCoNiCuCr high-entropy alloy / carbon nanotube catalyst is adopted in the present invention. The raw materials are cheap and the preparation process is simple. In OER, the initial potential can reach 1.5178 V vs RHE, and in ORR, the half-wave potential can reach 0.8471 V vs RHE. It has bifunctional oxygen electrocatalytic performance and can be close to the performance of noble metal-based catalysts, which is suitable for large-scale industrial applications;

[0027] 2. In the present invention, the FeCoNiCuCr high-entropy material is composed of multiple transition metals, and the ratio between Fe, Co, Ni, Cu and Cr is limited, so that the synergy of each metal in the high-entropy material improves the catalytic activity, enhances its structural stability, can maintain high activity for a long time in electrochemical reactions, extends the battery life, enhances its corrosion resistance in alkaline environments, and the transition metal elements in this material have good electrical conductivity, which is beneficial to electron transport, reduces the battery internal resistance, improves the energy conversion efficiency, and performs excellently in ORR and OER, which helps to improve the battery performance;

[0028] 3. In the present invention, through a two-step solvothermal method, the reactants are first dissolved in a small amount of solvent, and PVP is additionally added for a preliminary reaction to form an amorphous material. Then, carbon nanotubes are added to enable the high-entropy alloy to grow uniformly on the carbon nanotubes, increasing the specific surface area of the catalyst, thereby improving the OER and ORR performance of the metal-air battery. Description of the Drawings

[0029] Figure 1 is the scanning electron microscope image of the FeCoNiCuCr@CNTs-HEA sample prepared in Example 3;

[0030] Figure 2 is the CV curve of the catalyst samples prepared in Examples 1 to 6;

[0031] Figure 3 is the LSV (OER) curve of the catalyst samples prepared in Examples 1 to 6 and IrO2 provided in Comparative Example 1;

[0032] Figure 4 is the LSV (ORR) curve of the catalyst samples prepared in Examples 1 to 6 and Pt / C provided in Comparative Example 2;

[0033] Figure 5 is the CV curve of the catalyst samples prepared in Example 6 and Comparative Example 3;

[0034] Figure 6 is the LSV (OER) curve of the catalyst samples prepared in Example 6 and Comparative Example 3;

[0035] Figure 7 is the LSV (ORR) curve of the catalyst samples prepared in Example 6 and Comparative Example 3;

[0036] Figure 8 is the CV curve of the catalyst samples prepared in Comparative Example 4 and Comparative Example 5;

[0037] Figure 9 is the LSV (OER) curve of the catalyst samples prepared in Comparative Example 4 and Comparative Example 5 and IrO2 provided in Comparative Example 1;

[0038] Figure 10 is the LSV (ORR) curve of the catalyst samples prepared in Comparative Example 4 and Comparative Example 5 and Pt / C provided in Comparative Example 2. Detailed Embodiments

[0039] The invention will be further described in detail below in conjunction with specific embodiments. The embodiments can enable professionals in this field to understand the invention more comprehensively. It is intended to explain the invention and should not be construed as a limitation to the invention.

[0040] Hereinafter, a detailed description will be given in conjunction with the examples and comparative examples.

[0041] Example 1:

[0042] A preparation method of a FeCoNiCuCr high-entropy alloy / carbon nanotube catalyst, comprising the following steps:

[0043] (1) Dissolve 0.2 mmol of Ni(NO3)2·6H2O, 0.2 mmol of Fe(NO3)3·9H2O, 0.2 mmol of Co(NO3)2·6H2O, 0.2 mmol of Cu(NO3)2·5H2O, 0.2 mmol of Cr2(SO4)3, 0.3 mmol of DHTA and 1.0 g of PVP in a mixed solution of 1.35 mL of EtOH, 22.5 mL of DMF, and 1.35 mL of DIW. After ultrasonic dissolution for 60 min, transfer it to a Teflon autoclave and perform a hydrothermal reaction at 120 °C for 12 h to obtain FeCoNiCuCr@-MOF;

[0044] (2) Add 10 mg of carbon nanotubes to the reaction kettle solvent in step (1) and perform a hydrothermal reaction at 120 °C for 12 h to obtain FeCoNiCuCr@CNTs-MOF;

[0045] (3) Centrifuge the FeCoNiCuCr@CNTs-MOF in step (2) several times with deionized water and ethanol at a rotation speed of 8000 rmp / min until the supernatant is clear. Dry the centrifuged FeCoNiCuCr@CNTs-MOF powder in a vacuum oven at 80 °C for 12 h. Add dicyandiamide to the dried FeCoNiCuCr@CNTs-MOF powder at a ratio of 1:8, and then place it in a tube furnace filled with N2 and pretreat it at 400 °C for 1 h, and then anneal it at 800 °C for 2 h, with a heating rate of 5 °C·min -1 , to obtain a FeCoNiCuCr@CNTs-HEA sample.

[0046] In this example, the pretreatment method of the carbon nanotubes in step (2) is as follows:

[0047] Weigh 1.0 g of carbon nanotubes and add them to 30 mL of concentrated sulfuric acid, then stir for 1 h. Then slowly add 0.416 g of KNO3 and 1 g of KMnO4, stir at 45 °C for 30 min, then slowly add 40 mL of H2O, and continue stirring at 40 °C. After 15 min, add 140 mL of double distilled water and 10 mL of 30% H2O2 to terminate the oxidation reaction. Collect the oxidized CNTs and wash them several times with double distilled water and ethanol.

[0048] Example 2:

[0049] The difference between this example and Example 1 lies in the ratio of Fe and Co in the material. Specifically, in step (1) of this example, dissolve 0.2 mmol of Ni(NO3)2·6H2O, 0.2 mmol of Fe(NO3)3·9H2O, 0.4 mmol of Co(NO3)2·6H2O, 0.2 mmol of Cu(NO3)2·5H2O, 0.2 mmol of Cr2(SO4)3, 0.3 mmol of DHTA and 1.0 g of PVP in a mixed solution of 1.35 mL of EtOH, 22.5 mL of DMF, and 1.35 mL of DIW. After ultrasonic dissolution for 60 min, transfer it to a Teflon autoclave and carry out hydrothermal reaction at 120 °C for 12 h to obtain FeCoNiCuCr@-MOF; other processes are the same as those in Example 1, and finally obtain the FeCoNiCuCr@CNTs-HEA sample.

[0050] Example 3:

[0051] The difference between this example and Example 1 lies in the ratio of Fe and Co in the material. Specifically, in step (1) of this example, dissolve 0.2 mmol of Ni(NO3)2·6H2O, 0.4 mmol of Fe(NO3)3·9H2O, 0.2 mmol of Co(NO3)2·6H2O, 0.2 mmol of Cu(NO3)2·5H2O, 0.2 mmol of Cr2(SO4)3, 0.3 mmol of DHTA and 1.0 g of PVP in a mixed solution of 1.35 mL of EtOH, 22.5 mL of DMF, and 1.35 mL of DIW. After ultrasonic dissolution for 60 min, transfer it to a Teflon autoclave and carry out hydrothermal reaction at 120 °C for 12 h to obtain FeCoNiCuCr@-MOF; other processes are the same as those in Example 1, and finally obtain the FeCoNiCuCr@CNTs-HEA sample.

[0052] Example 4:

[0053] The difference between this example and Example 1 lies in the ratio of Fe and Co in the material. Specifically, in step (1) of this example, 0.2 mmol of Ni(NO3)2·6H2O, 0.6 mmol of Fe(NO3)3·9H2O, 0.2 mmol of Co(NO3)2·6H2O, 0.2 mmol of Cu(NO3)2·5H2O, 0.2 mmol of Cr2(SO4)3, 0.3 mmol of DHTA and 1.0 g of PVP are dissolved in a mixed solution of 1.35 mL of EtOH, 22.5 mL of DMF and 1.35 mL of DIW. After ultrasonic dissolution for 60 min, it is transferred to a Teflon autoclave and hydrothermally reacted at 120 °C for 12 h to obtain FeCoNiCuCr@-MOF; other processes are the same as those in Example 1, and finally the FeCoNiCuCr@CNTs-HEA sample is obtained.

[0054] Example 5:

[0055] The difference between this example and Example 1 lies in the ratio of Fe and Co in the material. Specifically, in step (1) of this example, 0.2 mmol of Ni(NO3)2·6H2O, 0.5 mmol of Fe(NO3)3·9H2O, 0.2 mmol of Co(NO3)2·6H2O, 0.2 mmol of Cu(NO3)2·5H2O, 0.2 mmol of Cr2(SO4)3, 0.3 mmol of DHTA and 1.0 g of PVP are dissolved in a mixed solution of 1.35 mL of EtOH, 22.5 mL of DMF and 1.35 mL of DIW. After ultrasonic dissolution for 60 min, it is transferred to a Teflon autoclave and hydrothermally reacted at 120 °C for 12 h to obtain FeCoNiCuCr@-MOF; other processes are the same as those in Example 1, and finally the FeCoNiCuCr@CNTs-HEA sample is obtained.

[0056] Example 6:

[0057] The difference between this example and Example 1 lies in the ratio of Fe and Co in the material. Specifically, in this example, in step (1), 0.2 mmol of Ni(NO3)2·6H2O, 0.3 mmol of Fe(NO3)3·9H2O, 0.2 mmol of Co(NO3)2·6H2O, 0.2 mmol of Cu(NO3)2·5H2O, 0.2 mmol of Cr2(SO4)3, 0.3 mmol of DHTA and 1.0 g of PVP are dissolved in a mixed solution of 1.35 mL of EtOH, 22.5 mL of DMF and 1.35 mL of DIW. After ultrasonic dissolution for 60 min, it is transferred to a Teflon autoclave and hydrothermally reacted at 120 °C for 12 h to obtain FeCoNiCuCr@-MOF; other processes are the same as those in Example 1, and finally the FeCoNiCuCr@CNTs-HEA sample is obtained.

[0058] Comparative Example 1:

[0059] Commercially available noble metal oxygen catalyst IrO2.

[0060] Comparative Example 2:

[0061] Commercially available noble metal oxygen catalyst Pt / C.

[0062] Comparative Example 3:

[0063] The difference between Comparative Example 3 and Example 6 is that PVP is not added. Specifically, in step (1) of this comparative example, 0.2 mmol of Ni(NO3)2·6H2O, 0.3 mmol of Fe(NO3)3·9H2O, 0.2 mmol of Co(NO3)2·6H2O, 0.2 mmol of Cu(NO3)2·5H2O, 0.2 mmol of Cr2(SO4)3 and 0.3 mmol of DHTA are dissolved in a mixed solution of 1.35 mL of EtOH, 22.5 mL of DMF and 1.35 mL of DIW. After ultrasonic dissolution for 60 min, it is transferred to a Teflon autoclave and hydrothermally reacted at 120 °C for 6 h to obtain FeCoNiCuCr@-MOF; other processes are the same as those in Example 6, and finally the FeCoNiCuCr@CNTs-HEA sample is obtained.

[0064] Comparative Example 4:

[0065] The difference between Comparative Example 4 and Comparative Example 3 lies in the preparation steps. In this comparative example, a preparation method of a FeCoNiCuCr high-entropy alloy / carbon nanotube catalyst includes the following steps:

[0066] (1) Dissolve 0.2 mmol of Ni(NO3)2·6H2O, 0.2 mmol of Fe(NO3)3·9H2O, 0.2 mmol of Co(NO3)2·6H2O, 0.2 mmol of Cu(NO3)2·5H2O, 0.2 mmol of Cr2(SO4)3, 0.3 mmol of DHTA and 10 mg of carbon nanotubes in a mixed solution of 1.35 mL of EtOH, 22.5 mL of DMF and 1.35 mL of DIW. After ultrasonic dissolution for 60 min, transfer it to a Teflon autoclave and carry out hydrothermal reaction at 120 °C for 24 h to obtain FeCoNiCuCr@CNTs-MOF;

[0067] (2) Centrifuge the FeCoNiCuCr@CNTs-MOF in step (1) several times with deionized water and ethanol at a rotation speed of 8000 rmp / min until the supernatant is clear. Dry the centrifuged FeCoNiCuCr@CNTs-MOF powder in a vacuum oven at 80 °C for 12 h. Add dicyandiamide to the dried FeCoNiCuCr@CNTs-MOF powder at a ratio of 1:8, and then place it in a tube furnace filled with N2 for pretreatment at 400 °C for 1 h, and then anneal it at 800 °C for 2 h with a heating rate of 5 °C·min -1 to obtain the FeCoNiCuCr@CNTs-HEA sample.

[0068] Comparative Example 5:

[0069] The difference between Comparative Example 5 and Comparative Example 4 lies in the ratio of Fe and Co in the material. Specifically, in step (1) of this comparative example, 0.2 mmol of Ni(NO3)2·6H2O, 0.2 mmol of Fe(NO3)3·9H2O, 0.4 mmol of Co(NO3)2·6H2O, 0.2 mmol of Cu(NO3)2·5H2O, 0.2 mmol of Cr2(SO4)3, 0.3 mmol of DHTA and 10 mg of carbon nanotubes are dissolved in a mixed solution of 1.35 mL of EtOH, 22.5 mL of DMF and 1.35 mL of DIW. After ultrasonic dissolution for 60 min, transfer it to a Teflon autoclave and carry out hydrothermal reaction at 120 °C for 24 h to obtain FeCoNiCuCr@CNTs-MOF. Other processes are the same as those in Comparative Example 4, and finally the FeCoNiCuCr@CNTs-HEA sample is obtained.

[0070] Characterize and analyze the catalyst samples prepared in Example 1. As Figure 1As shown, a scanning electron microscope (SEM, SU8100, Hitachi, Japan) was used to analyze the surface morphology and microstructure of the catalyst samples prepared in Example 3. It can be seen that the high-entropy nanoparticles are uniformly distributed on the carbon nanotubes.

[0071] Electrochemical experiments were carried out on the catalyst samples prepared in each example and comparative example. In the present invention, all electrochemical performance tests were carried out using a three-electrode system. Hg / HgO was used as the reference electrode, the graphite electrode was used as the counter electrode, and the rotating disk electrode (GC) was used as the working electrode. The electrolyte was 0.1 M KOH. All potentials were relative to RHE, and the following formula was used for accurate conversion: E(RHE) = E(Hg / HgO) + 0.0591pH + 0.098. By dispersing 6 mg of the catalyst sample in 50 μL of 5 wt% Nafion solution and 2 mL of absolute ethanol, and then ultrasonically treating for 2 hours to obtain a uniformly dispersed catalyst slurry, 25 μL of the prepared catalyst slurry was dropped on a GC with a diameter of 5 mm and naturally dried at room temperature to obtain a GC electrode with a loading amount of 373.32 μg·cm -2 -2.

[0072] 1. Cyclic voltammetry curve test:

[0073] Test conditions: three-electrode system, the electrolyte was 0.1 M KOH solution saturated with oxygen and argon, the potential range was 0.1 - 1.1 V, and the scanning rate was 50 mV·s -1 -1.

[0074] The cyclic voltammetry curves (CV curves) of the catalyst samples prepared in Examples 1 to 6 are as Figure 2 shown, and the O2 reduction peak positions are shown in Table 1 below. The CV curves of the catalyst samples prepared in Example 6 and Comparative Example 3 are as Figure 5 shown, and the CV curves of the catalyst samples prepared in Comparative Example 4 and Comparative Example 5 are as Figure 8 shown.

[0075] Table 1: O2 reduction peak positions in the CV curves of the catalyst samples prepared in Examples 1 to 6

[0076] Group <![CDATA[Oxygen reduction peak (V)]]> Example 1 0.7576 Example 2 0.7776 Example 3 0.7526 Example 4 0.5726 Example 5 0.7376 Example 6 0.7426

[0077] 2. OER performance test:

[0078] Test conditions: three-electrode system, the rotation speed was 2500 rpm, the electrolyte was 0.1 M KOH saturated with oxygen, the potential range was 0.86 - 1.86 V, and the scanning rate was 10 mV·s -1 -1.

[0079] The catalyst samples prepared in Examples 1 to 6 and IrO2 provided in Comparative Example 1 were subjected to OER performance tests. The LSV diagrams in the OER tests are as shown in Figure 3 and the initial potentials are as shown in Table 2 below. The LSV diagrams in the OER tests of the catalyst samples prepared in Example 6 and Comparative Example 3 are as shown in Figure 6 and the LSV diagrams in the OER tests of the catalyst samples prepared in Example 4 and Example 5 and IrO2 provided in the comparative example are as shown in Figure 9 .

[0080] Table 2: Initial potential positions in the LSV diagrams (OER) of the catalyst samples prepared in Examples 1 to 6 and IrO2 in Comparative Example 1

[0081] Group Initial potential (V vs RHE) Example 1 1.5528 Example 2 1.5178 Example 3 1.5409 Example 4 1.5859 Example 5 1.5538 Example 6 1.5518 Comparative Example 1 1.4437

[0082] 3. ORR performance test:

[0083] Test conditions: Three-electrode system, rotation speed of 2500 rpm, electrolyte of 0.1 M KOH saturated with oxygen, potential range of 0.86 - 1.86 V, scan rate of 10 mV·s -1 .

[0084] The catalyst samples prepared in Examples 1 to 6 and Pt / C provided in Comparative Example 2 were subjected to ORR performance tests. The LSV diagrams in the ORR tests are as shown in Figure 4 and the initial potentials are as shown in Table 3 below. The LSV diagrams in the ORR tests of the catalyst samples prepared in Example 1 and Comparative Example 3 are as shown in Figure 7 and the LSV diagrams in the ORR tests of the catalyst samples prepared in Example 4 and Example 5 and Pt / C provided in Comparative Example 2 are as shown in Figure 10 .

[0085] Table 3: Initial potential positions in the LSV diagrams (ORR) of the catalyst samples prepared in Examples 1 to 6 and Pt / C in Comparative Example 2

[0086] Group Initial potential (V vs RHE) Example 1 0.8382 Example 2 0.8471 Example 3 0.8282 Example 4 0.8022 Example 5 0.8322 Example 6 0.8322 Comparative Example 2 0.9408

[0087] Result analysis: In the LSV curves and CV curves at different ratios, it can be comprehensively seen that when the ratio of Fe to Co is 1.5:1, the performance of the FeCoNiCuCr high-entropy alloy / carbon nanotube catalyst is the best. During the preparation process, increasing PVP can increase the O2 reduction peak, and the starting potential of the ORR curve increases, while the starting potential of the OER curve at 10 mA is smaller. Therefore, increasing PVP during the preparation process can effectively improve the OER and ORR activities of the FeCoNiCuCr high-entropy alloy / carbon nanotube catalyst; moreover, during the preparation process, the OER and ORR activities of the FeCoNiCuCr high-entropy alloy / carbon nanotube catalyst are effectively improved by adopting the two-step solvent method. The main reason is that the two-step solvent method can make the high-entropy alloy grow uniformly on the carbon nanotubes, thereby increasing the specific surface area of the catalyst.

[0088] The present invention also discloses an application of the FeCoNiCuCr high-entropy alloy / carbon nanotube catalyst as described above in OER / ORR of metal-air batteries. More specifically, the FeCoNiCuCr high-entropy alloy / carbon nanotube catalyst as described above is applied in OER / ORR of zinc-air batteries.

[0089] All the features described in the specification, the appended claims and the drawings, whether alone or in any combination thereof, are important features of the present invention.

[0090] In the description of this specification, the description with reference to terms such as "one embodiment", "some embodiments", "one implementation manner", "specific implementation manner", "other implementation manners", "examples", "specific examples", or "some examples", etc. means that the specific features, structures, materials or characteristics described in connection with the embodiment or example are included in at least one embodiment, implementation manner or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described above can also be combined in a suitable manner in any one or more embodiments, implementation manners or examples. The technical solutions described in the present invention also include the technical solutions formed by any one or more of the above-described specific features, structures, materials or characteristics alone or in combination.

[0091] Although the embodiments of the present invention have been shown and described above, it can be understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Without departing from the principles and purposes of the present invention, those of ordinary skill in the art can make changes, modifications, substitutions, variations, delete some features, add features or re-combine features to the above embodiments within the scope of the present invention. Any simple modification, equivalent change and modification made to the above embodiments based on the innovative principles of the present invention still fall within the scope of the technical solutions of the present invention.

Claims

1. A FeCoNiCuCr high-entropy alloy / carbon nanotube catalyst, characterized in that, It includes a carbon nanotube support and an FeCoNiCuCr high-entropy alloy grown in-situ on the carbon nanotube support, where the molar ratio of Fe:Co:Ni:Cu:Cr is 1-3:1-2:1:1:

2.

2. A preparation method of the FeCoNiCuCr high-entropy alloy / carbon nanotube catalyst as described in claim 1, characterized in that, It includes the following steps: (1) Dissolve ferric salt, nickel salt, cobalt salt, copper salt, chromium salt, 2,5-dihydroxyterephthalic acid, and polyvinylpyrrolidone in a mixed solution composed of ethanol, N,N-dimethylformamide, and deionized water, ultrasonically dissolve, and then transfer it to a reaction kettle for hydrothermal reaction to obtain FeCoNiCuCr@-MOF; (2) Add carbon nanotubes to the reaction kettle solvent in step (1), and continue the hydrothermal reaction to obtain FeCoNiCuCr@CNTs-MOF; (3) Centrifuge the FeCoNiCuCr@CNTs-MOF in step (2) multiple times with deionized water and ethanol until the supernatant is clear. Vacuum dry the centrifuged FeCoNiCuCr@CNTs-MOF, add dicyandiamide, and heat-treat it in an inert atmosphere to obtain an FeCoNiCuCr high-entropy alloy / carbon nanotube catalyst, denoted as FeCoNiCuCr@CNTs-HEA.

3. The preparation method of a FeCoNiCuCr high-entropy alloy / carbon nanotube catalyst according to claim 2, characterized in that, In step (1), the ultrasonic dissolution time is 55-65 min, the temperature of the hydrothermal reaction is 110-130 °C, and the time is 12 h.

4. The preparation method of a FeCoNiCuCr high-entropy alloy / carbon nanotube catalyst according to claim 2, characterized in that, In step (1), the ferric salt is Fe(NO3)3·9H2O, the nickel salt is Ni(NO3)2·6H2O, the cobalt salt is Co(NO3)2·6H2O, the copper salt is Cu(NO3)2·5H2O, and the chromium salt is Cr2(SO4)3.

5. The preparation method of a FeCoNiCuCr high-entropy alloy / carbon nanotube catalyst according to claim 2, characterized in that, In step (1), the volume ratio of ethanol, N,N-dimethylformamide, and deionized water is 1.35:22.5:1.35; the ratio of nickel salt to ethanol is 0.2:1.35 mmol / mL, and the ratio of polyvinylpyrrolidone to ethanol is 0.5-1.0:1.35 g / mL.

6. The preparation method of a FeCoNiCuCr high-entropy alloy / carbon nanotube catalyst according to claim 2, characterized in that, The molar ratio of ferric salt, nickel salt, cobalt salt, copper salt, chromium salt, and 2,5-dihydroxyterephthalic acid is 1-3:1-2:1:1:1:

1.

7. The preparation method of a FeCoNiCuCr high-entropy alloy / carbon nanotube catalyst according to claim 2, wherein, In step (2), the ratio of nickel salt to carbon nanotubes is 0.2:5-10 mol / g; perform hydrothermal reaction at 110-130 °C for 12 h to obtain FeCoNiCuCr@CNTs-MOF.

8. The preparation method of a FeCoNiCuCr high-entropy alloy / carbon nanotube catalyst according to claim 2, characterized in that, In step (3), the centrifuged FeCoNiCuCr@CNTs-MOF is dried in a vacuum oven at 80 °C for 12 h.

9. The preparation method of a FeCoNiCuCr high-entropy alloy / carbon nanotube catalyst according to claim 2, characterized in that, In step (3), after vacuum drying FeCoNiCuCr@CNTs-MOF and adding dicyandiamide, it is placed in a nitrogen-filled tube furnace for pretreatment at 400 °C for 1 h, and then annealed at 800 °C for 2 h with a heating rate of 5 °C·min -1 , to obtain the FeCoNiCuCr high-entropy alloy / carbon nanotube catalyst.

10. The preparation method of a FeCoNiCuCr high-entropy alloy / carbon nanotube catalyst according to claim 9, characterized in that, The mass ratio of FeCoNiCuCr@CNTs-MOF to dicyandiamide is 1:

8.

11. Application of the FeCoNiCuCr high-entropy alloy / carbon nanotube catalyst as described in claim 1 in OER / ORR of a metal-air battery.

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