A high-entropy single atom / cluster carbon nanofiber oxygen catalyst and its preparation method

Abstract

The present invention belongs to the technical field of oxygen electrocatalytic materials, and specifically relates to a high-entropy single atom / cluster carbon nanofiber oxygen catalyst and a preparation method thereof. S1: preparing ZIF-8 nanoparticles; S2: preparing a composite MOFs material based on the ZIF-8 nanoparticles; S3: dispersing the composite MOFs material in a dimethylformamide solvent, adding Ni(NO3)2·6H2O and CuSO4·5H2O and stirring to obtain a mixed solution C, dissolving a polyacrylonitrile polymer in the mixed solution C to prepare a spinning solution, and obtaining a micro-nano fiber membrane by electrospinning technology; S4: pre-oxidizing and high-temperature carbonizing the micro-nano fiber membrane to obtain a micro-nano carbon fiber membrane; S5: anchoring Fe metal on the micro-nano carbon fiber membrane by chemical vapor deposition technology to obtain a high-entropy single atom / cluster carbon nanofiber oxygen catalyst.

Description

Technical Field

[0001] The present invention belongs to the technical field of oxygen electrocatalytic materials, and particularly relates to a high-entropy single atom / cluster carbon nanofiber oxygen catalyst and a preparation method thereof. Background Art

[0002] Against the backdrop of the growing global climate change problem, the development of zinc-air batteries with high energy density, long lifespan, and excellent flexibility is of great significance for promoting the practical application of flexible wearable electronics and achieving the goals of "carbon peak and carbon neutrality." Currently, the slow reaction kinetics and poor cycling stability of the ORR and OER reactions in zinc-air battery cathodes limit their large-scale application. Platinum-based catalysts (such as Pt / C) and iridium / ruthenium-based catalysts (such as Ir / C and RuO2) are currently the most effective commercial ORR and OER catalysts, respectively. However, these precious metals are expensive and scarce. Therefore, there is an urgent need to develop a low-cost, efficient and stable bifunctional oxygen catalyst to replace precious metal catalysts.

[0003] Single-atom catalysts (SACs) have become a research hotspot in areas such as ORR, OER, carbon dioxide reduction (CO2RR), nitrogen reduction (N2RR), hydrogen evolution (HER), and energy storage due to their unique atomic configuration and high atomic utilization. However, existing single-atom catalysts have a single structure, limited controllability of their structural composition, and lack of synergistic cooperation between metal atoms, making it difficult to achieve high catalytic activity and stability for both ORR and OER. At the same time, as one of the most core components of zinc-air batteries, flexible air cathodes should not only have good bifunctional oxygen catalytic performance but also good flexibility. However, current air cathodes are mostly composed of powdered active materials coated on a conductive substrate, which has poor flexibility and structural stability. Summary of the Invention

[0004] In response to the shortcomings of the existing technology, the present invention prepared high-entropy single-atom / cluster carbon nanofiber oxygen catalysts through electrospinning, high-temperature carbonization and chemical vapor deposition strategies, and developed a carbon fiber catalytic material with high ORR / OER catalytic activity and stability and good flexibility, which is of great significance for promoting its practical application in high-efficiency energy storage devices such as flexible zinc-air batteries.

[0005] The purpose of the present invention can be achieved through the following technical solutions:

[0006] A method for preparing a high-entropy single atom / cluster carbon nanofiber oxygen catalyst, the preparation method comprising the following steps:

[0007] S1. Adding a methanol solution containing 2-methylimidazole to a methanol solution containing Zn(NO3)2·6H2O and magnetically stirring the solution at room temperature for 24 hours; then washing the solution with methanol three times, centrifuging the solution, and vacuum drying the solution to obtain ZIF-8 nanoparticles;

[0008] S2. ZIF-8 nanoparticles were added to a methanol solution and subjected to ultrasonic and magnetic stirring to obtain a homogeneous mixed solution A. A methanol solution containing 2-methylimidazole was added to the mixed solution A and magnetically stirred to form a homogeneous mixed solution B. A methanol solution containing Zn(NO3)2·6H2O and Co(NO3)2·6H2O was then added to the mixed solution B and magnetically stirred for 12 hours. The solution was then washed with methanol three times and then centrifuged and vacuum dried to obtain composite MOFs.

[0009] S3, the composite MOFs were dispersed in dimethylformamide solvent, and then Ni(NO3)2·6H2O and CuSO4·5H2O were added. After magnetic stirring, a homogeneous mixed solution C was obtained. Then, polyacrylonitrile polymer was dissolved in the mixed solution C to prepare a spinning solution, and then a porous micro-nanofiber membrane was obtained by electrospinning technology;

[0010] S4, subjecting the micro-nano fiber membrane to pre-oxidation and high-temperature carbonization treatment in sequence to obtain a micro-nano carbon fiber membrane loaded with Zn, Co, Ni, and Cu metals;

[0011] S5. Using chemical vapor deposition technology, Fe metal is anchored on the micro-nano carbon fiber membrane loaded with Zn, Co, Ni, and Cu metals to obtain high-entropy single-atom / cluster carbon nanofiber oxygen catalyst;

[0012] In step S5, the Fe metal is anhydrous ferric chloride, and the mass ratio of the micro-nano carbon fiber membrane loaded with Zn, Co, Ni, and Cu metals to the anhydrous ferric chloride is 1:1.

[0013] Furthermore, in step S1, the mass ratio of 2-methylimidazole to Zn(NO3)2·6H2O is 1~3:1.

[0014] Furthermore, in step S2, the mass ratio of ZIF-8 nanoparticles, 2-methylimidazole, Zn(NO3)2·6H2O and Co(NO3)2·6H2O is (2~5):(16~48):(1~20):1.

[0015] Furthermore, the centrifugal treatment conditions in steps S1 and S2 are both: a rotation speed of 6000 rpm, a temperature of 15°C, and a time of 6 min; and the drying treatment conditions in steps S1 and S2 are both: a temperature of 70°C and a time of 12 h.

[0016] Furthermore, in step S3, the mass ratio of the composite MOFs material, Ni(NO3)2·6H2O, CuSO4·5H2O and polyacrylonitrile polymer is (100~250):(1~5):1:(60~150).

[0017] Furthermore, the conditions of the electrospinning technology in step S3 are: voltage of 18 KV; solution flow rate of 1 mL / h; distance from the needle to the receiving device of 12 cm; and ambient humidity of 45±5%.

[0018] Furthermore, the specific steps of pre-oxidation and high-temperature carbonization treatment in step S4 are as follows: placing the micro-nano fiber membrane in a tubular furnace, heating it to 280 ° C at a rate of 2 ° C / min and keeping it warm for 2 h for pre-oxidation; then heating it to 920 ° C at a rate of 5 ° C / min in an argon environment and keeping it warm for 3 h for high-temperature carbonization treatment, and after natural cooling, a micro-nano carbon fiber membrane loaded with Zn, Co, Ni, and Cu metals is obtained.

[0019] Furthermore, in step S5, the Fe metal is anhydrous ferric chloride, and the mass ratio of the micro-nano carbon fiber membrane loaded with Zn, Co, Ni, and Cu metals to anhydrous ferric chloride is 1:0.5-2.

[0020] A high-entropy single-atom / cluster carbon nanofiber oxygen catalyst is prepared by the above-mentioned preparation method of the high-entropy single-atom / cluster carbon nanofiber oxygen catalyst.

[0021] The application of the above-mentioned high-entropy single-atom / cluster carbon nanofiber oxygen catalyst in electrocatalytic oxygen reduction reaction and electrocatalytic oxygen evolution reaction.

[0022] The beneficial effects of the present invention are as follows: The method for preparing high-entropy single-atom / cluster carbon nanofiber oxygen catalysts proposed in the present invention utilizes electrospinning technology to prepare micro-nanofibers with a multi-level pore structure and a large specific surface area. This method utilizes high-temperature carbonization and chemical vapor deposition strategies to achieve uniform anchoring of transition metal single atoms / clusters such as Zn, Co, Ni, Cu, and Fe on flexible micro-nanocarbon fibers. The inexpensive high-entropy transition metal single-atom / cluster carbon nanofiber oxygen catalysts prepared by this method have high catalytic activity and stability for both ORR and OER, resulting in good economic benefits. Therefore, its application as a flexible self-supporting material in zinc-air batteries is of great significance for promoting the development of high-performance flexible energy storage devices and achieving my country's "dual carbon" goals. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] In order to more clearly illustrate the embodiments of the present disclosure or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, for ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.

[0024] Figure 1 These are scanning electron microscope (SEM) images of high-entropy single atom / cluster carbon nanofiber oxygen catalysts prepared in Examples 1 to 3 of the present invention, including a) Example 1; b) Example 2; and c) Example 3.

[0025] Figure 2 This is a transmission electron microscope (TEM) image of the high-entropy single atom / cluster carbon nanofiber oxygen catalyst prepared in Example 1 of the present invention and an element distribution (EDS-mapping) image of the corresponding area.

[0026] Figure 3 This is a photo of the actual sample of the high-entropy single atom / cluster carbon nanofiber oxygen catalyst prepared in Example 1 of the present invention.

[0027] Figure 4 This is a curved display diagram of the high-entropy single atom / cluster carbon nanofiber oxygen catalyst prepared in Example 1 of the present invention.

[0028] Figure 5 These are X-ray diffraction (XRD) patterns of high-entropy single atom / cluster carbon nanofiber oxygen catalysts prepared in Examples 1 to 3 of the present invention, including a. Example 1; b. Example 2; and c. Example 3.

[0029] Figure 6 These are cyclic voltammetry (CV) curves of ORR of high-entropy single-atom / cluster carbon nanofiber oxygen catalysts prepared in Examples 1 to 3 of the present invention in 0.1 MKOH electrolyte, including (a) Example 1; (b) Example 2; and (c) Example 3.

[0030] Figure 7 Linear sweep voltammetry (LSV) curves of the ORR of high-entropy single-atom / cluster carbon nanofiber oxygen catalysts prepared in Examples 1-3 of the present invention in 0.1 M KOH electrolyte at different rotation speeds. The inset is the corresponding KL curve of the ORR. These include (a) Example 1; (b) Example 2; and (c) Example 3.

[0031] Figure 8 LSV curves of the high-entropy single-atom / cluster carbon nanofiber oxygen catalysts prepared in Examples 1 to 3 of the present invention for OER at 1600 rpm in 0.1 MKOH electrolyte, including (a) Example 1; (b) Example 2; and (c) Example 3.

[0032] Figure 9 These are Tafel slope diagrams corresponding to the ORR of the high-entropy single-atom / cluster carbon nanofiber oxygen catalysts prepared in Examples 1 to 3 of the present invention in 0.1 MKOH electrolyte, including a, Example 1; b, Example 2; c, Example 3.

[0033] Figure 10 These are Tafel slope diagrams corresponding to the OER of the high-entropy single-atom / cluster carbon nanofiber oxygen catalysts prepared in Examples 1 to 3 of the present invention in 0.1 MKOH electrolyte, including a, Example 1; b, Example 2; c, Example 3.

[0034] Figure 11 This is a stability test chart of ORR of the high-entropy single atom / cluster carbon nanofiber oxygen catalyst prepared in Example 1 of the present invention and the commercial Pt / C catalyst in 0.1 M KOH electrolyte.

[0035] Figure 12 These are SEM images of low / medium / high entropy single atom / cluster carbon nanofiber oxygen catalysts prepared in Comparative Examples 1 to 4 of the present invention, including a, Comparative Example 1; b, Comparative Example 2; c, Comparative Example 3; d, Comparative Example 4.

[0036] Figure 13 These are the XRD patterns of the low / medium / high entropy single atom / cluster carbon nanofiber oxygen catalysts prepared in Comparative Examples 1 to 4 of the present invention, including a, Comparative Example 1; b, Comparative Example 2; c, Comparative Example 3; and d, Comparative Example 4.

[0037] Figure 14 LSV curves of the ORR at 1600 rpm for the low / medium / high entropy single atom / cluster carbon nanofiber oxygen catalysts and commercial Pt / C catalysts prepared in Comparative Examples 1 to 4 of the present invention in 0.1 M KOH electrolyte, including a, Comparative Example 1; b, Comparative Example 2; c, Comparative Example 3; d, Comparative Example 4; the illustration corresponds to the commercial Pt / C catalyst.

[0038] Figure 15 These are the Tafel slope plots corresponding to the ORR of the low / medium / high entropy single atom / cluster carbon nanofiber oxygen catalysts and commercial Pt / C catalysts prepared in Comparative Examples 1 to 4 of the present invention in 0.1 M KOH electrolyte, including a, Comparative Example 1; b, Comparative Example 2; c, Comparative Example 3; d, Comparative Example 4; e, commercial Pt / C catalyst.

[0039] Figure 16LSV curves of the low / medium / high entropy single atom / cluster carbon nanofiber oxygen catalysts and commercial RuO2 catalysts prepared in Comparative Examples 1 to 4 of the present invention for OER at 1600 rpm in 0.1 M KOH electrolyte, including a, Comparative Example 1; b, Comparative Example 2; c, Comparative Example 3; d, Comparative Example 4; the illustration corresponds to the commercial RuO2 catalyst.

[0040] Figure 17 These are the Tafel slope plots corresponding to the OER of the low / medium / high entropy single atom / cluster carbon nanofiber oxygen catalysts and commercial RuO2 catalysts prepared in Comparative Examples 1 to 4 of the present invention in 0.1 M KOH electrolyte, including a, Comparative Example 1; b, Comparative Example 2; c, Comparative Example 3; d, Comparative Example 4; e, commercial RuO2 catalyst. DETAILED DESCRIPTION

[0041] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts shall fall within the scope of protection of the present invention.

[0042] Commercial sources of commercial precious metal RuO2 catalysts and Pt / C catalysts are as follows:

[0043] 1. Commercial precious metal Pt / C catalyst:

[0044] Purchased from: Beijing Innochem Technology Co., Ltd. - Innochem;

[0045] Product model: CAS number: 7440-06-4;

[0046] Specification: 1g;

[0047] Molecular weight: 195.08;

[0048] No.:A07498;

[0049] Batch number: KYGKQ03.

[0050] 2. Commercial precious metal RuO2 catalyst:

[0051] Purchased by: Anhui Zesheng Technology Co., Ltd. - Anaiji Chemical;

[0052] Product model: CAS number: 12036-10-1;

[0053] Specification: 1g;

[0054] Molecular weight: 133.07;

[0055] No.:E060248;

[0056] Batch number: 03INROMO.

[0057] Example 1

[0058] 1. This example demonstrates a high entropy single atom / cluster carbon nanofiber oxygen catalyst (ZnCo-Ni 1.5 The preparation method of Cu-Fe@PCF comprises the following steps:

[0059] S1. Synthesis of metal-organic framework (ZIF-8): 200 mL of methanol solution containing 20 g of 2-methylimidazole was added to 200 mL of methanol solution containing 10 g of Zn(NO3)2·6H2O and magnetically stirred at room temperature for 24 h. The mixture was then washed three times with methanol and centrifuged (centrifugation parameters: 6000 rpm, 15°C, 6 min). The collected precipitate was dried in a vacuum oven at 70°C for 12 h to obtain ZIF-8 nanoparticles (NPs).

[0060] S2. Synthesis of composite metal-organic frameworks (MOFs): 0.9 g ZIF-8 NPs were dispersed in 100 mL methanol solution, ultrasonicated for 10 min, and then magnetically stirred; then 8 g 2-methylimidazole was dissolved in 100 mL methanol solution, and the above solution was added and magnetically stirred for 10 min to form a homogeneous mixed solution; then 4 g Zn(NO3)2·6H2O and Co(NO3)2·6H2O were dissolved in 100 mL methanol solution at a mass ratio of 15:1, and the above mixed solution was added and magnetically stirred for 3 h; then washed three times with methanol and centrifuged (centrifugation parameters: 6000 rpm, 15 ℃, 6 min); the collected precipitate was dried in a vacuum oven at 70 ℃ for 12 h to obtain ZIF-8+ZIF-67@ZIF-8 composite MOFs.

[0061] S3. Preparation of micro-nanofiber membrane: 0.8 g of the composite MOFs NPs synthesized in step (2) was dispersed in 4 g of DMF solvent, ultrasonicated for 30 min, and then magnetically stirred for 24 h. Then, 9.75 mg of Ni(NO3)2·6H2O and 4.875 mg of CuSO4·5H2O were dissolved in 1 g of DMF, added to the above solution, and magnetically stirred for 1 h. Then, 0.5 g of PAN was added to the above mixed solution and magnetically stirred for 12 h to obtain a homogeneous spinning solution. The obtained spinning solution was prepared into a micro-nanofiber membrane using electrospinning technology. The following steps were taken: the mass ratio of composite MOFs to PAN was 1.6:1; the amount of Ni salt added was 1.5% of the residual carbon content; the electrospinning voltage was 18 KV; the solution flow rate was 1 mL / h; the distance from the needle to the receiving device was 12 cm; and the ambient humidity was 45±5%.

[0062] S4, micro-nano carbon fiber catalytic materials loaded with Zn, Co, Ni, and Cu metals (ZnCo-Ni 1.5 Preparation of Cu@PCF): The micro-nano fiber membrane prepared in step (3) was placed in a tubular furnace, heated to 280 °C at a rate of 2 °C / min and kept warm for 2 h for pre-oxidation; then heated to 920 °C at a rate of 5 °C / min in an argon (Ar) environment and kept warm for 3 h, and then cooled naturally to obtain ZnCo-Ni 1.5 Cu@PCF.

[0063] S5, Zn, Co, Ni, Cu, Fe high entropy single atom / cluster carbon nanofiber oxygen catalyst (ZnCo-Ni 1.5 Preparation of Cu-Fe@PCF): ZnCo-Ni prepared in step (4) 1.5 A Cu@PCF micro-nano carbon fiber membrane and an equal mass of anhydrous ferric chloride (FeCl3) were placed in a tubular furnace, with the FeCl3 in the upstream and the fiber membrane in the downstream. Using CVD technology, the temperature was raised to 750°C in an Ar atmosphere at a rate of 10°C / min and then held for 3 hours for vapor deposition. This yielded a high-entropy single-atom / cluster carbon nanofiber oxygen catalyst.

[0064] The mass ratio of the micro-nano carbon fiber membrane loaded with Zn, Co, Ni, and Cu metals to anhydrous ferric chloride is 1:1.

[0065] 2. ZnCo-Ni obtained by the above preparation method and process parameters 1.5 The structural performance test results of Cu-Fe@PCF are as follows:

[0066] (a) Morphological structure: through Figure 1The SEM image in (a) shows that the composite MOFs-derived carbon nanocages are evenly distributed on the carbon fibers, where the carbon fibers have a diameter of about 2 µm, the MOFs-derived carbon nanocages have a size of about 300-400 nm, and the carbon fibers have a multi-level micro-nanostructure. Figure 2 The TEM image and EDS-mapping image of the corresponding area show that the metal species coexist as single atoms and nanoclusters, where the size of the nanoclusters / small nanoparticles is about 10 nm. Figure 3 ZnCo-Ni 1.5 Photo of the physical sample of Cu-Fe@PCF. Figure 4 ZnCo-Ni 1.5 The bending display of Cu-Fe@PCF sample shows that the sample can maintain good integrity after being folded and bent for many times, indicating that ZnCo-Ni 1.5 Cu-Fe@PCF has good flexibility. Figure 5 The XRD pattern of a can be observed that ZnCo-Ni 1.5 The peak of Cu-Fe@PCF at about 26° corresponds to the (002) crystal plane of graphitic carbon, the peak at about 35° corresponds to the (311) crystal plane of Fe3O4, and the peak at about 45° corresponds to the (200) crystal plane of FeO, indicating the formation of some iron species metal oxide clusters.

[0067] (b) Catalytic performance: 5 mg ZnCo-Ni 1.5 Cu-Fe@PCF catalyst powder was dispersed in 1.025 mL of a mixed solution containing 1 mL of ethanol / water (1:1, v / v) and 25 µL of Nafion (5 wt.%). The mixture was ultrasonicated at low temperature for 30 min to form a homogeneous catalyst ink. 20 µL of the ink was dropped onto the surface of a glassy carbon electrode and dried to obtain a working electrode. The working electrode was tested in a 0.1 M KOH solution using a standard three-electrode system with a millstone as the counter electrode and Ag / AgCl as the reference electrode. A rotating disk electrode (RDE) was used at 50 mV s -1 The CV curves were obtained at a scan rate of 5 mV s -1 The ORR-LSV curves were obtained at a scan rate of 400, 625, 900, 1225 and 1600 rpm. The OER-LSV curves were measured at a scan rate of 1600 rpm in 0.1 M KOH solution. Figure 6 As shown in (a), ZnCo-Ni 1.5 The CV curve of Cu-Fe@PCF has an obvious oxygen reduction peak at 0.808 V. Figure 7 As shown in (a), in alkaline medium, ZnCo-Ni 1.5The ORR half-wave potential (E1 / 2) of Cu-Fe@PCF is 0.864 V, which is higher than that of commercial precious metal Pt / C (0.850 V). The KL equation corresponding to the inset shows that it performs ORR via a 4-electron transfer pathway. Figure 8 As shown in (a), at 10 mA cm -2 ZnCo-Ni 1.5 The OER overpotential of Cu-Fe@PCF is 1.550 V, which is better than that of commercial noble metal RuO2 (1.602 V). Figure 9 As shown in a, ZnCo-Ni 1.5 The ORR Tafel slope of Cu-Fe@PCF is 86 mV dec. -1 , which is smaller than that of Pt / C catalyst (107 mV dec -1 ), indicating faster ORR reaction kinetics. Figure 10 As shown in a, ZnCo-Ni 1.5 The OER Tafel slope of Cu-Fe@PCF is 83 mV dec. -1 , which is smaller than that of RuO2 catalyst (91 mV dec -1 ), indicating that the catalyst has a faster OER kinetic reaction rate. Figure 11 As shown in the figure, after 12 h of stability test at 0.7 V potential, ZnCo-Ni 1.5 The current retention rate of Cu-Fe@PCF is 92.3%, which is higher than that of Pt / C catalyst (86.6%).

[0068] From the above test results, it can be seen that the high entropy single atom / cluster carbon nanofiber oxygen catalyst (ZnCo-Ni 1.5 Cu-Fe@PCF) has excellent ORR and OER catalytic activity and stability, which are better than commercial precious metal Pt / C and RuO2 catalysts, respectively. In addition, the fiber catalyst has good flexibility and can be used in the air positive electrode of flexible zinc-air batteries.

[0069] Example 2

[0070] 1. This example demonstrates a high entropy single atom / cluster carbon nanofiber oxygen catalyst (ZnCo-Ni 2.0 The preparation method of Cu-Fe@PCF is basically the same as that of Example 1, except that 9.75 mg of Ni(NO3)2·6H2O in step (3) is replaced by 13 mg of Ni(NO3)2·6H2O, so that the amount of Ni salt added is 2.0% of the remaining carbon content.

[0071] 2. ZnCo-Ni obtained by the above preparation method and process parameters 2.0 The structural performance test results of Cu-Fe@PCF are as follows:

[0072] (a) Morphological structure: through Figure 1 The SEM image in middle b shows that the composite MOFs-derived carbon nanocages are evenly distributed on the carbon fiber, where the carbon fiber diameter is about 1.5 µm, the MOFs-derived carbon nanocage size is about 400 nm, and the carbon fiber has a multi-level micro-nano structure. Through the TEM image and the EDS-mapping image of the corresponding area, it can be observed that the metal species coexist as single atoms and nanoclusters, where the size of the nanoclusters / small nanoparticles is about 10 nm. The sample was folded and bent several times, and it was able to maintain good integrity, indicating that the ZnCo-Ni 2.0 Cu-Fe@PCF has good flexibility. Figure 5 The XRD pattern of ZnCo-Ni can be observed in b 2.0 The peak of Cu-Fe@PCF at about 26° corresponds to the (002) crystal plane of graphitic carbon, the peaks at about 35° and 63° correspond to the (311) and (511) crystal planes of Fe3O4, respectively, the peak at about 45° corresponds to the (200) crystal plane of FeO, and the peak at about 55° corresponds to the (220) crystal plane of Ni, indicating the formation of some iron species metal oxide clusters.

[0073] (b) Catalytic performance: The test method of this embodiment is basically the same as that of embodiment 1, except that ZnCo-Ni 2.0 Cu-Fe@PCF was used as the working electrode for catalytic testing. Figure 6 As shown in (b), ZnCo-Ni 2.0 The CV curve of Cu-Fe@PCF has an obvious oxygen reduction peak at 0.803 V. Figure 7 As shown in (b), in alkaline medium, ZnCo-Ni 2.0 The ORR half-wave potential (E 1 / 2 ) is 0.839 V, and the KL equation corresponding to the illustration shows that the ORR occurs via a 4-electron transfer pathway. Figure 8 As shown in (b), at 10 mA cm -2 ZnCo-Ni 2.0 The OER overpotential of Cu-Fe@PCF is 1.630 V. Figure 9 As shown in b, ZnCo-Ni 2.0 The ORR Tafel slope of Cu-Fe@PCF is 74 mV dec. -1 , which is less than that of Pt / C catalyst (107 mVdec -1), indicating faster ORR reaction kinetics. Figure 10 As shown in b, ZnCo-Ni 2.0 The OER Tafel slope of Cu-Fe@PCF is 118 mV dec. -1 , which is at a relatively low level. After a 12 h continuous stability test at a potential of 0.7 V, ZnCo-Ni 2.0 The current retention of Cu-Fe@PCF is close to 100%.

[0074] Example 3

[0075] 1. This example demonstrates a high entropy single atom / cluster carbon nanofiber oxygen catalyst (ZnCo-Ni 2.5 The preparation method of Cu-Fe@PCF is basically the same as that of Example 1, except that 9.75 mg of Ni(NO3)2·6H2O in step (3) is replaced by 16.25 mg of Ni(NO3)2·6H2O, so that the amount of Ni salt added is 2.5% of the remaining carbon content.

[0076] 2. ZnCo-Ni obtained by the above preparation method and process parameters 2.5 The structural performance test results of Cu-Fe@PCF are as follows:

[0077] (a) Morphological structure: through Figure 1 The SEM image in c shows that the composite MOFs-derived carbon nanocages are evenly distributed on the carbon fibers, where the carbon fibers have a diameter of about 2 µm, the MOFs-derived carbon nanocages are about 400 nm in size, and the carbon fibers have a multi-level micro-nanostructure. The TEM image and the EDS-mapping image of the corresponding area show that the metal species coexist as single atoms and nanoclusters, where the size of the nanoclusters / small nanoparticles is about 10 nm. The sample was folded and bent several times, and it was able to maintain good integrity, indicating that the ZnCo-Ni 2.5 Cu-Fe@PCF has good flexibility. Figure 5 The XRD pattern of c can be observed that ZnCo-Ni 2.5 The peak of Cu-Fe@PCF at about 26° corresponds to the (002) crystal plane of graphitic carbon, the peak at about 45° corresponds to the (200) crystal plane of FeO, the peak at about 55° corresponds to the (220) crystal plane of Ni, and the peak at about 63° corresponds to the (511) crystal plane of Fe3O4, indicating the formation of some iron species metal oxide clusters.

[0078] (b) Catalytic performance: The test method of this embodiment is basically the same as that of embodiment 1, except that ZnCo-Ni 2.5Cu-Fe@PCF was used as the working electrode for catalytic testing. Figure 6 As shown in (c), ZnCo-Ni 2.5 The CV curve of Cu-Fe@PCF has an obvious oxygen reduction peak at 0.787 V. Figure 7 As shown in (c), in alkaline medium, ZnCo-Ni 2.5 The ORR half-wave potential (E 1 / 2 ) is 0.834 V, and the KL equation corresponding to the illustration shows that the ORR occurs via a 4-electron transfer pathway. Figure 8 As shown in (c), at 10 mA cm -2 ZnCo-Ni 2.5 The OER overpotential of Cu-Fe@PCF is 1.635 V. Figure 9 As shown in c, ZnCo-Ni 2.5 The ORR Tafel slope of Cu-Fe@PCF is 71 mV dec. -1 , which is less than that of Pt / C catalyst (107 mVdec -1 ), indicating faster ORR reaction kinetics. Figure 10 As shown in c, ZnCo-Ni 2.5 The OER Tafel slope of Cu-Fe@PCF is 121 mV dec. -1 , which is at a relatively low level. After a 12 h continuous stability test at a potential of 0.7 V, ZnCo-Ni 2.5 The current retention of Cu-Fe@PCF is close to 100%.

[0079] Comparative Example 1

[0080] 1. This comparative example provides a preparation method of an iron-loaded single-atom carbon nanofiber oxygen catalyst (ZIF-8, Fe@PCF), which is basically the same as Example 1, except that: 0.8 g of the ZIF-8 synthesized in step (1) is dispersed in 5 g of DMF solvent, ultrasonicated for 30 min, and then magnetically stirred for 24 h; then 0.5 g of PAN is added, and magnetically stirred for 12 h to obtain a homogeneous spinning solution; the obtained spinning solution is made into a micro-nano fiber membrane by using electrospinning technology; and the micro-nano fiber membrane is subjected to high-temperature carbonization in step (4) to obtain PCF; and then chemical vapor deposition is carried out in step (5) to convert the ZnCo-Ni in step (5) into a molten iron solution. 1.5 By replacing Cu@PCF with PCF, ZIF-8,Fe@PCF can be obtained.

[0081] 2. The structural performance test results of ZIF-8, Fe@PCF obtained by the above preparation method and process parameters are as follows: Figure 12The SEM image shown in a shows that the ZIF-8 derived carbon nanocages are evenly distributed on the carbon fibers, where the carbon fibers have a diameter of about 1.5 µm and the ZIF-8 derived carbon nanocages are about 200-300 nm in size. The carbon fibers have a multi-level micro-nano structure, and the loaded ZIF-8 derived carbon nanocages collapse after CVD and high-temperature carbonization. Figure 13 From the XRD pattern of Figure a, we can see that the peak of ZIF-8,Fe@PCF at about 26° corresponds to the (002) crystal plane of graphite carbon, and the peak at about 45° corresponds to the (200) crystal plane of FeO. Figure 14 As shown in (a), the ORR half-wave potential (E 1 / 2 ) is 0.843 V. Figure 15 As shown in (a), the ORR Tafel slope of ZIF-8,Fe@PCF is 77 mV dec. -1 , which is less than that of Pt / C catalyst (107 mVdec -1 ), indicating faster ORR reaction kinetics. Figure 16 As shown in Figure a, the OER overpotential of ZIF-8,Fe@PCF is 1.682 V at 10 mA cm-2. Figure 17 As shown in (a), the OER Tafel slope of ZIF-8,Fe@PCF is 111 mV dec. -1 , which is at a lower level.

[0082] Comparative Example 2

[0083] 1. This comparative example provides a carbon nanofiber oxygen catalyst (ZnCo-Ni 1.5 The preparation method of Cu@PCF is basically the same as that of Example 1, except that: ZnCo-Ni is directly obtained by adopting step (4) 1.5 Cu@PCF does not require step (5).

[0084] 2. ZnCo-Ni obtained by the above preparation method and process parameters 1.5 The structural performance test results of Cu@PCF are as follows: Figure 12 The SEM image shown in b shows that the carbon nanocages derived from the composite MOFs are evenly distributed on the carbon fibers, where the diameter of the carbon fibers is about 1.5 μm, the size of the carbon nanocages derived from the composite MOFs is about 200-300 nm, and the carbon fibers have a multi-level micro-nano structure. Figure 13 The XRD pattern of ZnCo-Ni can be observed in b 1.5The peak of Cu@PCF at about 26° corresponds to the (002) crystal plane of graphitic carbon, and the peak at about 45° corresponds to the (200) crystal plane of FeO. Figure 14 As shown in b, in alkaline medium, ZnCo-Ni 1.5 The ORR half-wave potential (E 1 / 2 ) is 0.811 V. Figure 15 As shown in b, ZnCo-Ni 1.5 The ORRTafel slope of Cu@PCF is 58 mV dec -1 , which is smaller than that of Pt / C catalyst (107 mV dec -1 ), indicating faster ORR reaction kinetics. Figure 16 As shown in b, at 10 mA cm -2 ZnCo-Ni 1.5 The OER overpotential of Cu@PCF is 1.749 V. Figure 17 As shown in b, ZnCo-Ni 1.5 The OER Tafel slope of Cu@PCF is 151 mV dec. -1 .

[0085] Comparative Example 3

[0086] 1. This comparative example provides a high entropy single atom / cluster carbon nanofiber oxygen catalyst (ZnCo-Ni 1.5 Cu-Fe 0.5 The preparation method of @PCF is basically the same as that of Example 1, except that the medium-quality anhydrous ferric chloride (FeCl3) in step (5) is replaced with 0.5 times the amount of FeCl3.

[0087] 2. ZnCo-Ni obtained by the above preparation method and process parameters 1.5 Cu-Fe 0.5 The structural performance test results of @PCF are as follows: Figure 12 The SEM image shown in c shows that the carbon nanocages derived from the composite MOFs are evenly distributed on the carbon fibers, where the diameter of the carbon fibers is about 1.5 μm, the size of the carbon nanocages derived from the composite MOFs is about 300 nm, and the carbon fibers have a multi-level micro-nano structure. Figure 13 The XRD pattern of c can be observed that ZnCo-Ni 1.5 Cu-Fe 0.5 The peak of @PCF at about 26° corresponds to the (002) crystal plane of graphite carbon, the peak at about 35° corresponds to the (311) crystal plane of Fe3O4, and the peak at about 45° corresponds to the (200) crystal plane of FeO. Figure 14 As shown in c, in alkaline medium, ZnCo-Ni1.5 Cu-Fe 0.5 @PCF ORR half-wave potential (E 1 / 2 ) is 0.832 V. Figure 15 As shown in c, ZnCo-Ni 1.5 Cu-Fe 0.5 The ORR Tafel slope of @PCF is 67 mV dec -1 , which is smaller than that of Pt / C catalyst (107 mV dec -1 ), indicating faster ORR reaction kinetics. Figure 16 As shown in c, at 10 mA cm -2 ZnCo-Ni 1.5 Cu-Fe 0.5 The OER overpotential of @PCF is 1.673 V. Figure 17 As shown in c, ZnCo-Ni 1.5 Cu-Fe 0.5 The OER Tafel slope of @PCF is 104 mV dec -1 , which is at a lower level.

[0088] Comparative Example 4

[0089] 1. This comparative example provides a high entropy single atom / cluster carbon nanofiber oxygen catalyst (ZnCo-Ni 1.5 Cu-Fe 2.0 The preparation method of @PCF is basically the same as that of Example 1, except that the medium-quality anhydrous ferric chloride (FeCl3) in step (5) is replaced with 2.0 times the amount of FeCl3.

[0090] 2. ZnCo-Ni obtained by the above preparation method and process parameters 1.5 Cu-Fe 2.0 The structural performance test results of @PCF are as follows: Figure 12 The SEM image shown in (d) shows that the composite MOFs-derived carbon nanocages are evenly distributed on the carbon fibers, where the carbon fibers have a diameter of about 1 µm and the composite MOFs-derived carbon nanocages are about 300 nm in size. The carbon fibers have a multi-level micro-nano structure, and the composite MOFs-derived carbon nanocages loaded thereon collapse after CVD and high-temperature carbonization. Figure 13 The XRD pattern of ZnCo-Ni can be observed in the middle d 1.5 Cu-Fe 2.0 The peak of @PCF at about 26° corresponds to the (002) crystal plane of graphite carbon, the peak at about 35° corresponds to the (311) crystal plane of Fe3O4, and the peak at about 45° corresponds to the (200) crystal plane of FeO. Figure 14As shown in Figure d, in alkaline medium, ZnCo-Ni 1.5 Cu-Fe 2.0 @PCF ORR half-wave potential (E 1 / 2 ) is 0.850 V. Figure 15 As shown in (d), ZnCo-Ni 1.5 Cu-Fe 2.0 The ORR Tafel slope of @PCF is 81 mV dec -1 , which is smaller than that of Pt / C catalyst (107 mV dec -1 ), indicating faster ORR reaction kinetics. Figure 16 As shown in middle d, at 10 mA cm -2 ZnCo-Ni 1.5 Cu-Fe 2.0 The OER overpotential of @PCF is 1.590 V. Figure 17 As shown in (d), ZnCo-Ni 1.5 Cu-Fe 2.0 @PCF’s OER Tafel slope is 84 mVdec -1 , which is at a lower level.

[0091] Throughout this specification, references to "one embodiment," "a comparative example," "a specific example," and the like indicate that the specific features, structures, materials, or characteristics described in conjunction with that embodiment or comparative example are included in at least one embodiment or comparative example of the present invention. In this specification, schematic representations of the above terms do not necessarily refer to the same embodiment or comparative example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or comparative examples.

[0092] The basic principles, main features, and advantages of the present invention are shown and described above. It should be understood by those skilled in the art that the present invention is not limited by the above embodiments and comparative examples. The above embodiments and descriptions are merely illustrative of the principles of the present invention. Various changes and modifications may be made to the present invention without departing from the spirit and scope of the present invention, and such changes and modifications fall within the scope of the invention as claimed.

Claims

1. A method for preparing a high entropy single atom / cluster carbon nanofiber oxygen catalyst, characterized in that: The preparation method comprises the following steps: S1. Adding a methanol solution containing 2-methylimidazole to a methanol solution containing Zn(NO3)2·6H2O and magnetically stirring the solution at room temperature for 24 hours; then washing the solution with methanol three times, centrifuging the solution, and vacuum drying the solution to obtain ZIF-8 nanoparticles; S2. ZIF-8 nanoparticles were added to a methanol solution and subjected to ultrasonic and magnetic stirring to obtain a homogeneous mixed solution A. A methanol solution containing 2-methylimidazole was added to the mixed solution A and magnetically stirred to form a homogeneous mixed solution B. A methanol solution containing Zn(NO3)2·6H2O and Co(NO3)2·6H2O was then added to the mixed solution B and magnetically stirred for 12 hours. The solution was then washed with methanol three times and then centrifuged and vacuum dried to obtain composite MOFs. S3, the composite MOFs were dispersed in dimethylformamide solvent, and then Ni(NO3)2·6H2O and CuSO4·5H2O were added. After magnetic stirring, a homogeneous mixed solution C was obtained. Then, polyacrylonitrile polymer was dissolved in the mixed solution C to prepare a spinning solution, and then a porous micro-nanofiber membrane was obtained by electrospinning technology; S4, pre-oxidizing and carbonizing the micro-nano fiber membrane in sequence to obtain a micro-nano carbon fiber membrane loaded with Zn, Co, Ni, and Cu metals; S5. Using chemical vapor deposition technology, Fe metal is anchored on the micro-nano carbon fiber membrane loaded with Zn, Co, Ni, and Cu metals to obtain high-entropy single-atom / cluster carbon nanofiber oxygen catalyst; In step S5, the Fe metal is anhydrous ferric chloride, and the mass ratio of the micro-nano carbon fiber membrane loaded with Zn, Co, Ni, and Cu metals to the anhydrous ferric chloride is 1:

1.

2. The method for preparing a high entropy single atom / cluster carbon nanofiber oxygen catalyst according to claim 1, characterized in that: In step S1, the mass ratio of 2-methylimidazole to Zn(NO3)2·6H2O is 1~3:

1.

3. The method for preparing a high entropy single atom / cluster carbon nanofiber oxygen catalyst according to claim 1, characterized in that: In step S2, the mass ratio of ZIF-8 nanoparticles, 2-methylimidazole, Zn(NO3)2·6H2O and Co(NO3)2·6H2O is (2~5):(16~48):(1~20):

1.

4. The method for preparing a high entropy single atom / cluster carbon nanofiber oxygen catalyst according to claim 1, characterized in that: The centrifugal treatment conditions in steps S1 and S2 are both: a rotation speed of 6000 rpm, a temperature of 15°C, and a time of 6 min; the drying treatment conditions in steps S1 and S2 are both: a temperature of 70°C and a time of 12 h.

5. The method for preparing high entropy single atom / cluster carbon nanofiber oxygen catalyst according to claim 1, characterized in that: In step S3, the mass ratio of the composite MOFs, Ni(NO3)2·6H2O, CuSO4·5H2O and polyacrylonitrile polymer is (100~250):(1~5):1:(60~150).

6. The method for preparing high entropy single atom / cluster carbon nanofiber oxygen catalyst according to claim 1, characterized in that: The conditions of the electrospinning technology in step S3 are: voltage of 18 KV; solution flow rate of 1 mL / h; distance from the needle to the receiving device of 12 cm; and ambient humidity of 45±5%.

7. The method for preparing a high entropy single atom / cluster carbon nanofiber oxygen catalyst according to claim 1, characterized in that: The specific steps of pre-oxidation and carbonization treatment in step S4 are as follows: placing the micro-nano fiber membrane in a tubular furnace, heating it to 280 ° C at a rate of 2 ° C / min and keeping it warm for 2 h for pre-oxidation; then heating it to 920 ° C at a rate of 5 ° C / min in an argon environment and keeping it warm for 3 h for high-temperature carbonization treatment, and after natural cooling, a micro-nano carbon fiber membrane loaded with Zn, Co, Ni, and Cu metals is obtained.

8. A high entropy single atom / cluster carbon nanofiber oxygen catalyst, characterized in that: The catalyst is prepared by the method for preparing the high-entropy single atom / cluster carbon nanofiber oxygen catalyst according to any one of claims 1 to 7.

9. Use of the high-entropy single-atom / cluster carbon nanofiber oxygen catalyst according to claim 8 in electrocatalytic oxygen reduction reaction and electrocatalytic oxygen evolution reaction.

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