A perovskite-based composite catalyst, a preparation method and application thereof

Abstract

The application discloses a perovskite-based composite catalyst and a preparation method and application thereof, and relates to the technical field of catalysts. The preparation method uses a plasma-enhanced chemical vapor deposition technology to deposit nitrogen-doped vertical graphene arrays on the surface of perovskite oxide nanofibers to obtain the perovskite-based composite catalyst; the perovskite oxide nanofiber has a chemical formula of La x Sr 1‑x MO 3‑δ , x = 0-0.5, and M is a B-site transition metal. The bifunctional electrocatalyst can significantly improve the ORR / OER catalytic activity of raw materials under alkaline conditions, is applied to the assembly and test of a zinc-air battery, can significantly reduce the overpotential on an air electrode, improves the energy density and power efficiency, and significantly enhances the long-term stability of charging and discharging.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of catalysts, in particular to a perovskite-based composite catalyst and a preparation method and application thereof. BACKGROUND

[0002] With the consumption of traditional fossil energy and the further aggravation of environmental pollution, the realization of sustainable green clean energy conversion technology has become the focus of current social concern. Zinc-air batteries have become a research hotspot in the field of new energy due to their high energy density, low cost, green environmental protection and other advantages. However, the kinetics of oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) of the air electrode of the zinc-air battery is slow during the charging and discharging process, therefore, designing a high-efficiency and stable dual-function oxygen electrocatalyst is one of the key factors to improve the performance of the air electrode of the zinc-air battery. Traditional noble metal catalysts such as Pt / C and IrO2 have excellent ORR and OER catalytic performance, but due to their high price, scarcity, poor stability and inability to consider dual-function catalytic activity, their commercial application is limited. Therefore, it is crucial to develop a low-cost, high-efficiency and stable non-noble metal-based catalyst. In recent years, perovskite oxides, as a member of non-metallic oxides, have attracted widespread attention due to their abundant reserves, stable chemical structure and easy control of physical and chemical properties, and are considered to be a dual-function oxygen electrocatalyst with application prospects. At present, perovskite oxide materials are designed and regulated in terms of electronic structure, electronic and ionic conductivity and microstructure by means of element doping and catalyst compounding.

[0003] The compounding of perovskite materials and nitrogen-doped graphene materials is an effective way to improve the conductivity, catalytic activity and stability of the materials. This is mainly due to the high chemical stability, high electronic conductivity and large specific surface area of graphene. The contact area between the electrode and the electrolyte can be increased, which is conducive to electron transmission. Secondly, literature reports that nitrogen doping can generate a large number of oxygen vacancies, which can more effectively drive the chemical kinetics process of ORR / OER. In addition, the vertical graphene array plays a role in structural support, so that the material structure remains stable during the electrochemical charging and discharging process, thereby obtaining better rate and cycle performance. It is reported that nitrogen-doped vertical graphene is generally prepared by plasma chemical vapor deposition method, which has a complex general method process. The graphene needs to be grown first and then doped with nitrogen, which leads to a long growth time. Moreover, the nitrogen-doped vertical graphene cannot be uniformly distributed. Long-time processing not only makes the process complicated and the growth effect poor, but also causes damage to the perovskite material. Therefore, it is particularly important to find a more gentle and efficient method for growing nitrogen-doped graphene. SUMMARY

[0004] The present application aims at the above-mentioned deficiencies of the prior art, and provides a perovskite-based composite catalyst and a preparation method and application thereof.

[0005] The preparation method of the perovskite-based composite catalyst of the application utilizes the plasma enhanced chemical vapor deposition technology to deposit nitrogen-doped vertical graphene arrays on the surface of perovskite oxide nanofibers to obtain the perovskite-based composite catalyst. x Sr 1-x MO 3-δ , x = 0 ~ 0.5, and M is a B-site transition metal.

[0006] Further, the x is 0.1, 0.2, 0.3, 0.4 or 0.5.

[0007] Further, the method specifically comprises the following steps:

[0008] S1: according to the chemical formula La x Sr 1-x MO 3-δ , the La source, the Sr source and the metal M source are respectively weighed in stoichiometric ratio and dissolved in an organic solvent, polyvinylpyrrolidone (PVP) is added after stirring until completely dissolved, and the solution is continuously stirred until it is in a viscous state;

[0009] S2: the solution is spun by using the electrospinning technology, and the spinning is dried after completion;

[0010] S3: the dried spinning is heat-treated after pre-oxidation to form a phase, and a perovskite oxide nanofiber La x Sr 1-x MO 3-δ , denoted as LSM, is obtained;

[0011] S4: the nanofiber LSM is placed in the cavity of a plasma enhanced chemical vapor deposition (PECVD) system, vacuum heating is performed, a certain flow of argon is introduced to blow liquid acetonitrile into the cavity after reaching a preset temperature, a plasma excitation device is turned on and the power is set, nitrogen-doped vertical graphene is rapidly grown on the perovskite surface at high temperature, the excitation device is turned off after the growth is completed, argon backflow is used, the heating device is turned off, the sample is taken out after the instrument is naturally cooled, and the perovskite-based composite catalyst is obtained.

[0012] Further, the La source in step S1 is La(NO3)3·6H2O, the Sr source is Sr(NO3)3, the M source is a nitrate or chloride salt of a corresponding metal, for example, the organic solvent is N,N-dimethylformamide (DMF), and / or the M source is one or more of Fe(NO3)3·9H2O, Co(NO3)2·6H2O, Ni(NO3)2·6H2O and Mn(NO3)2·4H2O.

[0013] Further, the electrostatic spinning technology in step S2 adopts a negative pressure of-3 to-3.5 kV, a positive pressure of 15 to 18 kV, a receiving distance of 15 to 20 cm, and a push injection speed of 0.015 to 0.025 mL / min. -1 .

[0014] Further, in step S3, pre-oxidation is performed at a temperature rising rate of 0.5 ℃ / min -1 to 220 ℃ for 2 hours, and finally phase formation is performed at a temperature rising rate of 0.5 ℃ / min -1 to 900 to 1000 ℃ for 5 hours to obtain the nanofiber LSM.

[0015] Further, in step S4, the PECVD cavity is pre-set to a temperature of 450 to 600 ℃, nitrogen-doped vertical graphene is rapidly grown at a high temperature, argon gas is used at a flow rate of 10 to 20 sccm, the bubbling speed of acetonitrile is maintained at 2 to 4 bubbles per second, the power of the plasma excitation device is 400 to 700 W, and the growth time is 1 to 3 min.

[0016] Further, in step S4, the specific operation of growing the nitrogen-doped vertical graphene array on the nanofiber LSM is as follows: the PECVD cavity is rapidly heated to 500 ℃ under vacuum, the vacuum degree is within 10 Pa, argon gas is introduced into the container containing acetonitrile at a flow rate of 10 sccm, the bubbling speed of acetonitrile is maintained at 2 bubbles per second, the plasma power is set to 500 W, growth is performed for 1 to 3 min, the plasma is turned off, and 10 sccm of argon gas is used for backflow, the heating is stopped, and the instrument is naturally cooled, and the growth time is determined according to the actual growth requirement.

[0017] A perovskite-based composite catalyst prepared by the preparation method.

[0018] The application of the perovskite-based composite catalyst as described above, which is coated on the carbon paper of the positive current collector of the liquid zinc-air battery or the nickel mesh of the flexible zinc-air battery positive current collector as a catalyst.

[0019] The bifunctional electrocatalyst can significantly improve the ORR / OER catalytic activity of raw materials under alkaline conditions, and when applied to the assembly and testing of zinc-air batteries, can significantly reduce the overpotential on the air electrode, improve the energy density and power efficiency, and significantly enhance the long-term stability of charging and discharging.

[0020] The preparation method of the present application can efficiently and quickly realize the growth of the nitrogen-doped vertical graphene array on the surface of the perovskite oxide nanofiber by the plasma gas phase chemical deposition technology, and the growth thickness can be accurately controlled. The perovskite-based composite material with the grown graphene array is applied to the flexible zinc-air battery cathode catalyst, and the commercial application approach of the flexible zinc-air battery can be expanded.

[0021] The preparation method of the present application can efficiently and quickly realize the growth of the nitrogen-doped vertical graphene array on the surface of the perovskite oxide nanofiber by the plasma gas phase chemical deposition technology, and the growth thickness can be accurately controlled. The perovskite-based composite material with the grown graphene array is applied to the flexible zinc-air battery cathode catalyst, and the commercial application approach of the flexible zinc-air battery can be expanded. BRIEF DESCRIPTION OF DRAWINGS

[0022] Figure 1 A flowchart of LSC and LSC@NVG-1 / 2 / 3min prepared in Example 1;

[0023] Figure 2 a-d are scanning electron microscope (SEM) images of LSC and LSC@NVG-1 / 2 / 3min prepared in Example 1;

[0024] Figure 3 X-ray powder diffraction (XRD) patterns of LSC and LSC@NVG-3min prepared in this example 1;

[0025] Figure 4a X-ray photoelectron spectroscopy (XPS) of Co / O / N elements of LSC and LSC@NVG-3min prepared in this example 1;

[0026] Figure 5a LSV curves of ORR performance of LSC and LSC@NVG-1 / 2 / 3min and commercial Pt / C catalyst prepared in this example 1 in 0.1 mol / L KOH solution; - 1 LSV curves of ORR performance of LSC and LSC@NVG-1 / 2 / 3min and commercial Pt / C catalyst prepared in this example 1 in 0.1 mol / L KOH solution;

[0027] Figure 5b LSV curves of OER performance of LSC and LSC@NVG-1 / 2 / 3min and commercial iridium oxide catalyst prepared in this example 1 in 1 mol / L KOH solution; -1LSV curves of OER performance in KOH solution;

[0028] Figure 6a Physical diagram and open circuit voltage of sandwich type zinc-air battery assembled by LSC@NVG-3min prepared in this embodiment 1;

[0029] Figure 6b Polarization performance test curve of sandwich type flexible zinc-air battery assembled by LSC and LSC@NVG-3min prepared in this embodiment 1;

[0030] Figure 6c Rate performance test curve of flexible zinc-air battery assembled by LSC and LSC@NVG-3min prepared in this embodiment 1;

[0031] Figure 6d Discharge capacity test curve of flexible zinc-air battery assembled by LSC and LSC@NVG-3min prepared in this embodiment 1 under the condition of current density of 5mA cm -2

[0032] Figure 6e Charge-discharge cycle performance test curve of flexible zinc-air battery assembled by LSC and LSC@NVG-3min prepared in this embodiment 1 under the condition of 5mA cm -2 DETAILED DESCRIPTION

[0033] The following are specific embodiments of the present application and further describe the technical solutions of the present application in conjunction with the accompanying drawings, but the present application is not limited to these embodiments.

[0034] Embodiment 1:

[0035] According to the chemical formula La 0.5 Sr 0.5 CoO 3-δ , La(NO3)3·6H2O, Sr(NO3)3, Co(NO3)2·6H2O were weighed according to the stoichiometric ratio and dissolved in 10 mL N,N-dimethylformamide (DMF) in turn, 1.4g polyvinylpyrrolidone (PVP) was added after stirring to completely dissolve, continue to stir for 12 hours until the solution is viscous, then use electrospinning technology for spinning, the spinning machine parameters are set as follows: negative pressure is-3kV, positive pressure is 16kV, humidity is 20%, receiving distance is 15cm, push injection speed is 0.015mL min -1 . After spinning, it is placed in a 60℃ blast drying oven for drying for 12 hours, then heated to 220℃ at a heating rate of 0.5℃ min -1 for 2 hours for pre-oxidation, then heated to 800℃ at a heating rate of 0.5℃ min​​-1 Raising temperature to 900℃ for 5 hours to form phase, obtaining LSC nanofiber.

[0036] The LSC nanofiber is placed in the PECVD cavity and vacuumed to 500℃, the vacuum degree is 10 Pa, then argon is introduced to blow liquid acetonitrile into the cavity at a speed of two bubbles per second, the amount of acetonitrile is 50 mL, the argon flow rate is 10 sccm, then the plasma device is turned on, the power is set to 500 W, the mixed gas of acetonitrile and argon is excited into plasma by radio frequency excitation, nitrogen-doped vertical graphene is rapidly grown on the surface of the perovskite oxide nanofiber at high temperature, the growth time is 1-3 min, and the vacuum degree of the cavity during the whole process needs to be less than 20 Pa. After deposition, LSC@NVG-1min, LSC@NVG-2min and LSC@VG-3min are obtained.

[0037] Referring to the accompanying drawings Figure 2 a-d are scanning electron microscope (SEM) images of LSC and LSC@NVG-1 / 2 / 3min prepared according to the technical solution of the embodiment, reflecting that the thickness of the nitrogen-doped vertical graphene growth increases with the increase of the deposition time.

[0038] Referring to the accompanying drawings Figure 3 Fig. 4 is an X-ray powder diffraction (XRD) spectrum of LSC@NVG-3min prepared according to the technical solution of the embodiment, and the results of the material before and after deposition show that it corresponds to the peaks of LSC, and a characteristic peak of the (00 2) crystal plane of N-doped graphene appears at about 22°.

[0039] Referring to the accompanying drawings Figure 4a a-c are X-ray photoelectron (XPS) energy spectra of Co 2p, O 1s and N 1s of LSC@NVG-3min prepared according to the technical solution of the embodiment. The results of the material before and after deposition show that N is successfully doped, and the characteristic peak of the Co element at the B site of the perovskite does not change significantly, and the analysis of the characteristic peak of the O element shows that the introduction of N significantly improves the concentration of oxygen vacancy in the perovskite lattice, greatly promoting the reaction kinetics process of oxygen evolution and oxygen reduction.

[0040] In order to verify the electrocatalytic performance of the catalyst, oxygen evolution (OER) and oxygen reduction (ORR) performance tests are carried out, and 0.1 mol L -1 KOH solution is completed in a three-electrode test system, the rotating disc electrode rotates at a speed of 1600 rpm, the reference electrode is a saturated calomel electrode, the counter electrode is a platinum electrode, and the working electrode is a platinum-carbon electrode coated with 2 μL of catalyst slurry. The catalyst slurry is prepared by mixing 16 mg of catalyst, 4 mg of Ketjen black, 3.9 mL of ethanol and 200 μL of Nafion solution for three hours.

[0041] See appendix Figure 5a The LSC@NVG-1~3min prepared according to the technical solution of this embodiment was reacted with LSC and a commercial Pt / C catalyst in 0.1 mol L... -1 LSV curves of ORR performance in KOH solution. LSC@NVG-3min exhibited excellent ORR catalytic activity. Compared with LSC (0.65V), LSC@NVG-1 (0.68V), and LSC@NVG-2 (0.71V), LSC@NVG-3 (0.80V) had a higher half-wave potential, second only to commercial Pt / C (0.89V), indicating that it has the best ORR catalytic activity.

[0042] See appendix Figure 5b The LSC@NVG-1~3min prepared according to the technical solution of this embodiment was reacted with LSC and a commercial iridium oxide catalyst in 0.1 mol L... -1 LSV curves of OER performance in KOH solution. At 10 mA / cm². -2 At the given current density, LSC@NVG-3 exhibits a potential of 1.65 V, significantly lower than the 1.69 V of the commercial catalyst iridium oxide, indicating its faster oxygen exchange kinetics.

[0043] The flexible zinc-air battery of this invention uses zinc foil as the negative electrode and a nickel mesh coated with catalyst material as the positive electrode. It uses PAM gel electrolyte. 4g of acrylamide, 21mg of N,N-methylenebisacrylamide, and 32mg of ammonium persulfate are dissolved sequentially in 30mL of deionized water, stirred at room temperature for 5 minutes, then poured into a mold and placed in a 60℃ oven for 3 hours. After solidification, 6mol L⁻¹ is added dropwise. -1 KOH and 0.2 mol L -1 A zinc acetate mixture solution was used. A flexible zinc-air battery was assembled from the positive electrode, negative electrode, and gel electrolyte for testing.

[0044] See appendix Figure 6a The image shows a flexible zinc-air battery assembled from LSC@NVG-3 and LSC materials, along with its open-circuit voltage. It can be seen that its open-circuit voltage is relatively high, at 1.46V.

[0045] See appendix Figure 6b The figure shows the polarization performance test curves of a flexible zinc-air battery assembled with LSC@NVG-3 and LSC materials. As can be seen from the figure, the zinc-air battery assembled with the LSC@NVG-3 catalyst can achieve a maximum power density of 142 mW / cm². -2 It is significantly higher than the 82mW cm of LSC. -2 .

[0046] See appendix Figure 6cThe rate performance test curves of the flexible zinc-air batteries assembled by LSC@NVG-3 and LSC materials. As can be seen from the figure, the flexible zinc-air batteries assembled by LSC@NVG-3 materials show a relatively stable discharge platform at each current density, and when the current density returns to 1 mA cm -2 , the voltage also returns to 1.35 V, indicating the excellent reversibility of the zinc-air battery.

[0047] Referring to the accompanying Figure 6d The discharge performance test curves of the flexible zinc-air batteries assembled by LSC@NVG-3 and LSC materials under the condition of 5 mA cm -2 . The figure shows that the discharge capacity of LSC@NVG-3 under the condition of 5 mA cm -2 is 840 mA h g -1 , which is better than 760 mA h g -1 of LSC, and the discharge voltage is stable without obvious decrease.

[0048] Referring to the accompanying Figure 6e The charge-discharge cycle performance test curves of the flexible zinc-air batteries assembled by LSC@NVG-3 and LSC materials under the condition of 5 mA cm -2 . The flexible zinc-air battery of LSC@NVG-3 catalyst continuously charges and discharges for 25 hours without obvious attenuation, proving that it has better cycle stability than LSC.

[0049] Example 2:

[0050] According to the chemical formula La 0.5 Sr 0.5 FeO 3-δ , La (NO3) 3·6H2O, Sr (NO3) 3, Fe (NO3) 3·6H2O are weighed according to the stoichiometric ratio and dissolved in 10 mL N, N-dimethylformamide (DMF) in turn, 1.4 g of polyvinylpyrrolidone (PVP) is added after stirring to complete dissolution, and the solution is continuously stirred for 12 hours until it becomes viscous. The spinning machine parameters are set as follows: negative pressure is -3 kV, positive pressure is 16 kV, humidity is 20%, receiving distance is 15 cm, and injection speed is 0.018 mL min -1 . After spinning, it is placed in a 60°C air drying oven for 12 hours, then heated to 220°C at a heating rate of 0.5°C min -1 for 2 hours for pre-oxidation, and then heated to 950°C at a heating rate of 0.5°C min -1 for 5 hours for phase formation, to obtain LSF nanofibers.

[0051] LSF nanofiber was placed in the PECVD cavity and vacuum heated to 500℃, then argon was introduced to blow liquid acetonitrile into the cavity at a rate of two bubbles per second, the amount of acetonitrile was 50mL, the argon flow rate was 10sccm, then the plasma device was turned on, the power was set to 450W, the mixed gas of acetonitrile and argon was excited into plasma by radio frequency excitation, nitrogen-doped vertical graphene was rapidly grown on the surface of the perovskite oxide nanofiber at high temperature, the growth time was 1-3min, and the cavity vacuum degree needed to be less than 20Pa during the whole process. After deposition, LSF@NVG-1min, LSF@NVG-2min and LSF@VG-3min were obtained.

[0052] Its main XRD structure and SEM morphology are similar to those of Example 1, and its electrocatalytic performance and zinc-air battery performance are better than those of the un-deposited LSF single-phase catalyst.

[0053] In the ORR test of LSF@NVG-3, the half-wave potential was 0.76V, and the OER curve corresponded to a potential of 1.67V at a current density of 10mAcm -2 .

[0054] Example 3:

[0055] According to the chemical formula La 0.5 Sr 0.5 NiO 3-δ , La(NO3)3·6H2O, Sr(NO3)3 and Ni(NO3)2·6H2O were weighed according to the stoichiometric ratio, and then dissolved in 10mL N,N-dimethylformamide (DMF) in sequence. After stirring until completely dissolved, 1.5g of polyvinylpyrrolidone (PVP) was added, and the solution was continuously stirred for 12 hours until it became viscous. Then, electrospinning was performed using the electrospinning technology, with the spinning machine parameters set as follows: negative pressure -3kV, positive pressure 17kV, humidity 20%, receiving distance 15cm, and injection speed 0.02mL min -1 . After spinning, it was placed in a 60℃ blast drying oven for drying for 12 hours, then heated to 220℃ at a rate of 0.5℃ min -1 for 2 hours for pre-oxidation, and then heated to 900℃ at a rate of 0.5℃ min -1 for 5 hours for phase formation, to obtain LSN nanofiber.

[0056] LSN nanofiber was placed in the PECVD cavity and vacuum heated to 500℃, then argon was introduced to blow liquid acetonitrile into the cavity at a rate of two bubbles per second, the amount of acetonitrile was 50mL, the argon flow rate was 10sccm, then the plasma device was turned on, the power was set to 600W, the mixed gas of acetonitrile and argon was excited into plasma by radio frequency excitation, nitrogen-doped vertical graphene was rapidly grown on the surface of perovskite oxide nanofiber at high temperature, the growth time was 1-3min, and the cavity vacuum degree needed to be less than 20Pa during the whole process. After deposition, LSN@NVG-1min, LSN@NVG-2min and LSN@NVG-3min were obtained.

[0057] Its main XRD structure and SEM morphology are similar to those of Example 1, and its electrocatalytic performance and zinc-air battery performance are better than those of LSN without deposited NVG.

[0058] In the ORR test of LSN@NVG-3, the half-wave potential was 0.78V, and the OER curve had a potential of 1.68V at a current density of 10mA cm -2 .

[0059] Example 4:

[0060] According to the chemical formula La 0.5 Sr 0.5 MnO 3-δ , La(NO3)3·6H2O, Sr(NO3)3 and Mn(NO3)2·4H2O were weighed according to the stoichiometric ratio, and then dissolved in 10mL N,N-dimethylformamide (DMF) in sequence. After stirring until completely dissolved, 1.5g of polyvinylpyrrolidone (PVP) was added, and the solution was continuously stirred for 12 hours until it became viscous. Then, electrospinning was performed using the electrospinning technology, with the spinning machine parameters set as follows: negative pressure -3kV, positive pressure 17kV, humidity 20%, receiving distance 15cm, and injection speed 0.02mL min -1 . After spinning, it was placed in a 60℃ blast drying oven for drying for 12 hours, then heated to 220℃ at a rate of 0.5℃ min -1 for 2 hours for pre-oxidation, and then heated to 1000℃ at a rate of 0.5℃ min -1 for 5 hours for phase formation, to obtain LSMn nanofiber.

[0061] LSMn nanofibers were placed in a PECVD chamber and heated to 500℃ in vacuum, then argon was introduced to bubble liquid acetonitrile into the chamber at a rate of two bubbles per second, the amount of acetonitrile was 50 mL, the argon flow rate was 20 sccm, then the plasma device was turned on, the power was set to 600 W, the mixed gas of acetonitrile and argon was excited into plasma by radio frequency excitation, nitrogen-doped vertical graphene was rapidly grown on the surface of the perovskite oxide nanofibers at high temperature, the growth time was 1-3 min, and the chamber vacuum degree needed to be less than 20 Pa during the whole process. After deposition, LSMn@NVG-1min, LSMn@NVG-2min and LSMn@NVG-3min were obtained.

[0062] Its main XRD structure and SEM morphology are similar to those of Example 1, and its electrocatalytic performance and zinc-air battery performance are better than those of LSM without deposited NVG.

[0063] In the ORR test of LSMn@NVG-3, the half-wave potential was 0.79 V, and the OER curve at a current density of 10 mA cm -2 corresponded to a potential of 1.69 V.

[0064] The above not involved, applicable to the prior art.

[0065] Although some specific embodiments of the present application have been described in detail by examples, those skilled in the art should understand that the above examples are only for illustration, not for limiting the scope of the present application, and those skilled in the art can make various modifications or supplements to the described specific embodiments or use similar ways to replace, but not deviate from the direction of the present application or beyond the scope defined by the appended claims. Those skilled in the art should understand that any modification, equivalent replacement, improvement, etc. made according to the technical essence of the present application to the above embodiments shall be included in the protection scope of the present application.

Claims

1. Use of a perovskite-based composite catalyst, characterized in that, The perovskite-based composite catalyst is coated on a liquid zinc-air battery positive electrode current collector carbon paper or a flexible zinc-air battery positive electrode current collector nickel mesh as a catalyst; A perovskite-based composite catalyst is prepared by depositing nitrogen-doped vertical graphene arrays on the surface of perovskite oxide nanofibers using a plasma-enhanced chemical vapor deposition technique; the perovskite oxide nanofibers have a chemical formula of La x Sr 1-x MO 3-δ , x = 0 ~ 0.5, and M is a B-site transition metal The preparation method of the perovskite-based composite catalyst specifically comprises the following steps: S1: according to the chemical formula La x Sr 1-x MO 3-δ , the La source, the Sr source and the metal M source are weighed according to the stoichiometric ratio respectively, and are sequentially dissolved in an organic solvent, stirring until completely dissolved, then adding polyvinylpyrrolidone, continuing to stir until the solution is in a viscous state; S2: The solution is spun by using an electrostatic spinning technology, and after spinning is completed, drying is performed; S3: after drying the spinning, pre-oxidation treatment, heat preservation phase, get perovskite oxide nanofiber La x Sr 1- x MO 3-δ , recorded as nanofiber LSM; S4: The nanofiber LSM is placed in a cavity of a plasma enhanced chemical vapor deposition (PECVD) system, vacuum heating is performed, after a preset temperature is reached, a certain flow of argon is introduced to bubble liquid acetonitrile into the cavity, a plasma excitation device is turned on and a power is set, nitrogen-doped vertical graphene is rapidly grown on the perovskite surface at high temperature, after growth is completed, the excitation device is turned off and argon backflow is used, after a heating device is turned off and the instrument is naturally cooled, the sample is taken out, and the perovskite-based composite catalyst is obtained. The M source is one or more of Fe(NO3)3·9H2O, Co(NO3)2·6H2O, Ni(NO3)2·6H2O and Mn(NO3)2·4H2O.

2. Use according to claim 1, characterized in that: The x is 0.1, 0.2, 0.3, 0.4 or 0.

5.

3. The use according to claim 1, characterized in that: The La source in step S1 is La(NO3)3·6H2O, and the Sr source is Sr(NO3)3; the organic solvent is N,N-dimethylformamide.

4. The use according to claim 1, characterized in that: The electrospinning technique in step S2 adopts a negative pressure of -3~ -3.5 kV, a positive pressure of 15~18 kV, a receiving distance of 15~20 cm, and a push injection speed of 0.015~0.025 mL min -1 .

5. The use according to claim 1, characterized in that: In step S3, the temperature was raised to 220 °C at a rate of 0.5 °C min -1 for 2 hours for pre-oxidation, and finally raised to 900-1000 °C at a rate of 0.5 °C min -1 for 5 hours for phase formation to obtain nanofiber LSM.

6. The use according to claim 1, characterized in that: In step S4, the PECVD cavity is preset to a temperature of 450-600 °C, nitrogen-doped vertical graphene is rapidly grown at high temperature, the argon flow used is 10-20 sccm, the acetonitrile bubbling speed is maintained at 2-4 bubbles per second, the power of the plasma excitation device is 400-700 W, and the growth time is 1-3 min.

Images