PrFeO3 / carbon material composite bifunctional catalyst and preparation method thereof

Abstract

The invention discloses a PrFeO3 / carbon material composite bifunctional catalyst and a preparation method thereof, and belongs to the technical field of new energy materials and electrochemical catalysis. The PrFeO3 / carbon material composite bifunctional catalyst is prepared by mixing a carbon material and PrFeO3 powder according to a mass ratio of (0.6-1.2): 1 and then carrying out ball milling. The PrFeO3 / carbon material composite bifunctional catalyst prepared by a ball milling method has excellent ORR and OER catalytic activity, and can be used as a bifunctional catalyst for fuel cells and metal-air cells.

Description

Technical Field

[0001] The invention belongs to the technical field of new energy materials and electrochemical catalysis, and in particular relates to a PrFeO3 / carbon material composite bifunctional catalyst and a preparation method thereof. Background Art

[0002] In recent years, affected by the current serious environmental problems and the growing demand for energy, the development of green and sustainable energy conversion and storage technologies has become a major issue in modern society. Air batteries have the advantages of high energy density, environmental friendliness, good safety and low cost. They are very promising new energy storage systems that can be applied to large-scale energy storage systems, electric vehicles and other electronic products. However, the kinetics of oxygen in the air electrode during the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) are slow, and general catalysts are difficult to meet the catalytic requirements. Therefore, it is necessary to develop bifunctional catalysts that meet the requirements.

[0003] Common bifunctional catalysts are roughly divided into the following four types: precious metals and their alloys, carbon materials, transition metal oxides, and composite materials. These catalysts are widely used due to their excellent physical properties and excellent catalytic activity in oxygen reduction reactions (ORR) and OER. However, the catalysts prepared by current technology face problems such as high cost, complex synthesis process, and insufficient stability in alkaline environments. For example, the existing patent CN115241476B uses MXene material as a carrier, and ball-mills it with zinc manganate doped with praseodymium and gadolinium to obtain a dual-element doped ZnMnO3@MXene bifunctional catalyst with ORR and OER catalytic properties; Patent CN109119648A first uses high-energy ball milling to prepare LaCoO with a single crystal form and large specific surface area. 3-δ Perovskite material, and then LaCoO prepared by ball milling 3-δ / CNTs composite catalyst; Patent CN112421064B is A2Mn x After O6 perovskite oxide is mixed with carbon black, nitrogen is in-situ doped and a composite catalytic material is prepared in one step. These methods have disadvantages such as poor activity, limited specific surface area and relatively low apparent catalytic activity when preparing bifunctional catalysts. Therefore, the existing technology still needs further improvement and development. Summary of the invention

[0004] In response to the above technical problems, the present invention proposes a PrFeO3 / carbon material composite bifunctional catalyst and a preparation method, aiming to solve the problems of high cost, low reserves, low activity and stability in alkaline systems of the bifunctional catalysts prepared by the prior art.

[0005] To achieve the above object, the present invention provides the following technical solutions:

[0006] One of the purposes of the present invention is to provide a PrFeO3 / carbon material composite bifunctional catalyst, which is prepared by mixing carbon material and PrFeO3 powder in a mass ratio of (0.6-1.2):1 and then ball milling.

[0007] The present invention uses carbon material as a carrier, and ball-mills it with PrFeO3 perovskite oxide powder prepared by a sol-gel method to prepare a PrFeO3 / carbon material composite catalyst with ORR and OER dual-functional activity. With the addition of carbon material, the specific surface area of ​​the material increases to varying degrees, exposing more active sites, thereby enhancing the conductivity of the perovskite material and increasing oxygen vacancies, thereby improving the electrocatalytic activity of the PrFeO3 perovskite material, and can be used as a dual-functional catalyst in fuel cells and metal-air batteries.

[0008] Furthermore, the carbon material is one or more of MXene, CNT and g-C3N4.

[0009] Furthermore, the specific preparation steps of the PrFeO3 powder include:

[0010] Adding soluble praseodymium salt and soluble iron salt into deionized water, adding a complexing agent, mixing and stirring, adjusting the pH to alkaline, heating and stirring in a water bath, and drying to obtain a mixture;

[0011] The mixture is ground into powder, and pre-sintered and calcined in sequence to obtain PrFeO3 powder with a perovskite structure.

[0012] Furthermore, the soluble praseodymium salt is one or more of praseodymium chloride, praseodymium sulfate, praseodymium phosphate and praseodymium nitrate; and / or

[0013] The soluble iron salt is one or more of ferric chloride, ferric sulfate and ferric nitrate; and / or

[0014] The molar ratio of the praseodymium element in the soluble praseodymium salt to the iron element in the soluble iron salt is 1:1; and / or

[0015] The molar ratio of the total amount of metal ions in the soluble praseodymium salt and the soluble iron salt to the complexing agent is 1:(1-5); and / or

[0016] The complexing agent is one or both of citric acid and ethylenediaminetetraacetic acid; and / or

[0017] The mixing and stirring time is 1-8h; and / or

[0018] The pH is 8-9; and / or

[0019] The conditions of water bath heating and stirring are: temperature 70-90° C., time 1-8 h; and / or

[0020] The pre-sintering treatment conditions are: temperature 200-500°C, time 1-8h; and / or

[0021] The calcination treatment conditions are: temperature 600-900° C., time 1-8 h.

[0022] The second object of the present invention is to provide a method for preparing a PrFeO3 / carbon material composite bifunctional catalyst, comprising the following steps: ball milling the carbon material and PrFeO3 powder, centrifuging, washing and drying to obtain a PrFeO3 / carbon material composite bifunctional catalyst.

[0023] Furthermore, the specific steps of the ball milling treatment include: adding the carbon material and PrFeO3 powder into a stainless steel ball milling jar, then adding anhydrous ethanol, and ball milling at a rotation speed of 100-500 rpm for 1-48 hours.

[0024] The third object of the present invention is to provide an application of the above-mentioned PrFeO3 / carbon material composite bifunctional catalyst in the preparation of air electrodes.

[0025] A fourth object of the present invention is to provide an application of the above-mentioned PrFeO3 / carbon material composite bifunctional catalyst in the fields of fuel cells and metal-air batteries.

[0026] Compared with the prior art, the present invention has the following advantages and technical effects:

[0027] The PrFeO3 / carbon material composite bifunctional catalyst prepared by the ball milling method of the present invention has excellent ORR and OER catalytic activities and can be used as a bifunctional catalyst in fuel cells and metal-air batteries. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] The accompanying drawings constituting a part of the present invention are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. In the accompanying drawings:

[0029] Figure 1 The XRD diffraction patterns of the catalysts prepared in Example 1, Example 2, Example 3 and Comparative Example 1;

[0030] Figure 2 The SEM images of the catalysts prepared in Comparative Example 1 (a) and Example 1 (b), Example 2 (c), and Example 3 (d);

[0031] Figure 3 The XPS full energy spectra of the catalysts prepared in Example 1, Example 2 and Example 3;

[0032] Figure 4 The catalysts prepared in Example 1, Example 2, Example 3 and Comparative Example 1 were saturated with O2 at 0.1 mol·L -1 ORR polarization curve in KOH electrolyte;

[0033] Figure 5 The catalysts prepared in Example 1, Example 2, Example 3 and Comparative Example 1 were saturated with O2 at 0.1 mol·L -1 OER polarization curves in KOH electrolyte. DETAILED DESCRIPTION

[0034] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as limiting the present invention, but should be understood as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0035] It should be understood that the terms described in the present invention are only for describing special embodiments and are not intended to limit the present invention. In addition, for the numerical range in the present invention, it should be understood that each intermediate value between the upper and lower limits of the scope is also specifically disclosed. Each smaller range between the intermediate value in any stated value or stated range and any other stated value or intermediate value in the described range is also included in the present invention. The upper and lower limits of these smaller ranges can be independently included or excluded in the scope.

[0036] Unless otherwise indicated, all technical and scientific terms used herein have the same meanings as those generally understood by those skilled in the art. Although the present invention describes only preferred methods and materials, any methods and materials similar or equivalent to those described herein may also be used in the implementation or testing of the present invention. All documents mentioned in this specification are incorporated by reference to disclose and describe the methods and / or materials associated with the documents. In the event of a conflict with any incorporated document, the content of this specification shall prevail.

[0037] It will be apparent to those skilled in the art that various modifications and variations may be made to the specific embodiments of the present invention description without departing from the scope or spirit of the present invention. Other embodiments derived from the present invention description will be apparent to those skilled in the art. The present invention description and examples are exemplary only.

[0038] The words “include,” “including,” “have,” “contain,” etc. used in this document are open-ended terms, meaning including but not limited to.

[0039] The present invention provides a method for preparing a PrFeO3 / carbon material composite bifunctional catalyst, comprising the following steps:

[0040] (1) Preparation of PrFeO3 powder: adding a soluble praseodymium salt and a soluble iron salt to deionized water, adding a complexing agent, mixing and stirring, adjusting the pH to alkaline with ammonia water, heating and stirring in a water bath, and drying to obtain a mixture;

[0041] Grinding the mixture into powder, and sequentially performing pre-sintering and calcining to obtain PrFeO3 powder with a perovskite structure;

[0042] (2) Preparation of PrFeO3 / carbon material composite bifunctional catalyst: The carbon material and PrFeO3 powder are ball-milled, centrifuged, washed and dried to obtain a PrFeO3 / carbon material composite bifunctional catalyst.

[0043] The present invention uses a ball milling method to compound a specific amount of carbon material, thereby exposing more active sites and obtaining a larger specific surface area, thereby enhancing the conductivity of the perovskite material and increasing oxygen vacancies, thereby improving the electrocatalytic activity of the PrFeO3 perovskite material.

[0044] In some embodiments of the present invention, the soluble praseodymium salt in step (1) is one or more of praseodymium chloride, praseodymium sulfate, praseodymium phosphate and praseodymium nitrate. For example, in the following embodiments of the present invention, the soluble praseodymium salt can be praseodymium nitrate.

[0045] In some embodiments of the present invention, the soluble iron salt in step (1) is one or more of ferric chloride, ferric sulfate and ferric nitrate. Exemplarily, in the following embodiments of the present invention, the soluble iron salt can be ferric nitrate.

[0046] In some embodiments of the present invention, the molar ratio of the praseodymium element in the soluble praseodymium salt to the iron element in the soluble iron salt in step (1) is 1:1.

[0047] In some embodiments of the present invention, the molar ratio of the total amount of metal ions in the soluble praseodymium salt and the soluble iron salt to the complexing agent in step (1) is 1:(1-5). Exemplarily, in the following embodiments of the present invention, the molar ratio of the total amount of metal ions in the soluble praseodymium salt and the soluble iron salt to the complexing agent is 1:3 or any range between the aforementioned ratios.

[0048] In some embodiments of the present invention, the complexing agent in step (1) is one or both of citric acid and ethylenediaminetetraacetic acid. Exemplarily, in the following embodiments of the present invention, the complexing agent can be selected from citric acid and ethylenediaminetetraacetic acid, and the molar ratio of citric acid to ethylenediaminetetraacetic acid is 1:2.

[0049] In some embodiments of the present invention, the mixing and stirring time in step (1) is 1-8 hours. Exemplarily, in the following embodiments of the present invention, the mixing and stirring time is 1 hour or any value between the aforementioned range values.

[0050] In some embodiments of the present invention, the pH in step (1) is 8-9. For example, in the following embodiments of the present invention, the pH=8 or any value between the aforementioned ranges.

[0051] In some embodiments of the present invention, the temperature of the water bath heating and stirring in step (1) is 70-90°C. Exemplarily, in the following embodiments of the present invention, the temperature of the water bath heating and stirring is 80°C or any value between the aforementioned ranges. The time of the water bath heating and stirring is 1-8h. Exemplarily, in the following embodiments of the present invention, the time of the water bath heating and stirring is 3h or any value between the aforementioned ranges.

[0052] In some embodiments of the present invention, the temperature of the pre-firing treatment in step (1) is 200-500°C. For example, in the following embodiments of the present invention, the temperature of the pre-firing treatment is 350°C or any value between the aforementioned ranges. The time of the pre-firing treatment is 1-8h. For example, in the following embodiments of the present invention, the time of the pre-firing treatment is 2h or any value between the aforementioned ranges.

[0053] In some embodiments of the present invention, the temperature of the calcination treatment in step (1) is 600-900°C. For example, in the following embodiments of the present invention, the temperature of the calcination treatment is 700°C or any value between the aforementioned ranges. The time of the calcination treatment is 1-8h. For example, in the following embodiments of the present invention, the time of the calcination treatment is 2h or any value between the aforementioned ranges.

[0054] In some embodiments of the present invention, the carbon material in step (1) is one or more of MXene, CNT and g-C3N4. Exemplarily, in the following embodiments of the present invention, MXene, CNT or g-C3N4 can be selected.

[0055] In some embodiments of the present invention, the mass ratio of the carbon material to the PrFeO3 powder in step (2) is (0.6-1.2):1. By way of example, in the following embodiments of the present invention, the mass ratio of the carbon material to the PrFeO3 powder can be selected to be (0.9-1.1):1 or any range between the aforementioned ratios.

[0056] In some embodiments of the present invention, the specific steps of the ball milling treatment in step (2) include: adding the carbon material and PrFeO3 powder to a stainless steel ball mill, adding anhydrous ethanol, and ball milling at a speed of 100-500 rpm for 1-48 hours. Exemplarily, in the following embodiments of the present invention, the specific steps of the ball milling treatment are: adding the carbon material and PrFeO3 powder to a stainless steel ball mill, adding 5 mL of anhydrous ethanol, and ball milling at a speed of 300 rpm for 20 hours.

[0057] The above preparation method can be used to prepare a PrFeO3 / carbon material composite bifunctional catalyst, which has the advantages of low cost, simple synthesis process, good stability in alkaline system, and significantly improved catalytic activity of the catalyst. It can be used as a bifunctional catalyst in fuel cells and metal-air batteries.

[0058] The raw materials used in the present invention are all purchased from the market.

[0059] The technical solution of the present invention is further illustrated by the following embodiments.

[0060] Example 1

[0061] A method for preparing a PrFeO3 / carbon material composite bifunctional catalyst comprises the following steps:

[0062] (1) Preparation of PrFeO3 powder: praseodymium nitrate and ferric nitrate (the molar ratio of praseodymium element to iron element is 1:3) are added to 70 mL of deionized water, and then a complexing agent (the molar ratio of the total amount of metal ions to the complexing agent is 1:3, and the complexing agent is prepared by mixing citric acid and ethylenediaminetetraacetic acid in a molar ratio of 1:2) is added, and the mixture is stirred for 1 h, and the pH is adjusted to 8 with ammonia water, heated in a water bath at 80°C and stirred for 3 h, and then placed in an oven at 80°C until completely dried to obtain a mixture;

[0063] The mixture was placed in an agate mortar and fully ground for 20 minutes, first heated to 350° C. in a muffle furnace and kept for 2 hours, and then calcined at 700° C. for 2 hours to obtain PrFeO3 powder with a perovskite structure;

[0064] (2) Preparation of PrFeO3 / carbon material composite bifunctional catalyst: The carbon material MXene and PrFeO3 powder were mixed in a mass ratio of 1:1 and added to a stainless steel ball mill. Then 5 mL of anhydrous ethanol was added and ball milled at 300 rpm for 20 h. The material was collected, centrifuged, washed, and dried to obtain a PrFeO3 / carbon material composite bifunctional catalyst.

[0065] Example 2

[0066] The same as Example 1, except that in step (2), the PrFeO3 / carbon material composite bifunctional catalyst is prepared by mixing the carbon material CNT and PrFeO3 powder in a mass ratio of 0.9:1 and adding them to a stainless steel ball mill, then adding 5 mL of anhydrous ethanol, and ball milling at 300 rpm for 20 h. The material is collected, centrifuged, washed, and dried to obtain a PrFeO3 / carbon material composite bifunctional catalyst.

[0067] Example 3

[0068] The same as Example 1, except that step (2) in step (2) is the preparation of PrFeO3 / carbon material composite bifunctional catalyst: the carbon material g-C3N4 and PrFeO3 powder are mixed in a mass ratio of 1.1:1 and added to a stainless steel ball mill, and then 5 mL of anhydrous ethanol is added, and the ball mill is carried out at a speed of 300 rpm for 20 h. The material is collected, centrifuged, washed, and dried to obtain a PrFeO3 / carbon material composite bifunctional catalyst.

[0069] Example 4

[0070] A method for preparing a PrFeO3 / carbon material composite bifunctional catalyst comprises the following steps:

[0071] (1) Preparation of PrFeO3 powder: praseodymium nitrate and ferric nitrate (the molar ratio of praseodymium element to iron element is 1:1) are added to 70 mL of deionized water, and then a complexing agent (the molar ratio of the total amount of metal ions to the complexing agent is 1:3, and the complexing agent is prepared by mixing citric acid and ethylenediaminetetraacetic acid in a molar ratio of 1:2) is added, and the mixture is stirred for 1 h, the pH is adjusted to 8 with ammonia water, heated in a water bath at 80°C and stirred for 3 h, and then placed in an oven at 80°C until completely dried to obtain a mixture;

[0072] The mixture was placed in an agate mortar and fully ground for 20 minutes, and then directly heated to 750° C. in a muffle furnace and calcined for 2 hours to obtain a PrFeO3 powder with a perovskite structure;

[0073] (2) Preparation of PrFeO3 / carbon material composite bifunctional catalyst: The carbon material MXene and PrFeO3 powder were mixed in a mass ratio of 1:1 and added to a stainless steel ball mill. Then 5 mL of anhydrous ethanol was added and ball milled at 300 rpm for 20 h. The material was collected, centrifuged, washed, and dried to obtain a PrFeO3 / carbon material composite bifunctional catalyst.

[0074] Performance test results: The composite material half-wave potential is 0.67V, the overpotential is 684mV, and the Tafel slope is 192mV·dec -1 , the ORR catalytic activity is higher than that of Comparative Example 1.

[0075] Comparative Example 1

[0076] The same as Example 1, except that step (2) is not performed, and the PrFeO3 powder prepared in step (1) is directly used as a catalyst.

[0077] Comparative Example 2

[0078] The same as Example 1, except that in step (1), the molar ratio of the total amount of metal ions in the soluble praseodymium salt and the soluble iron salt to the complexing agent is 1:7.

[0079] Performance test results: The CV curve of the sample also has an obvious oxygen reduction peak, but the current density of the OER curve within the voltage range does not reach 10 mA cm -2 , the performance is poor, and therefore it does not have bifunctional catalytic activity.

[0080] Comparative Example 3

[0081] The same as Example 1, except that in step (2), the carbon material and PrFeO3 powder are mixed in a mass ratio of 0.4:1.

[0082] Performance test results: Mxene cannot completely cover PrFeO3, the electronic conductivity is hindered, the active sites for oxygen adsorption and desorption are only in the interaction part between Mxene and PrFeO3, the overpotential of the composite material is 733mV, and the catalytic activity is low.

[0083] Comparative Example 4

[0084] The same as Example 1, except that in step (2), the carbon material and PrFeO3 powder are mixed in a mass ratio of 1.3:1.

[0085] Performance test results: The PrFeO3 that can truly provide activity is completely coated by Mxene, providing limited active sites for the reaction. The catalytic activity of the composite material is low, with an overpotential of 759mV.

[0086] Comparative Example 5

[0087] Same as Example 1, except that the mass of carbon material in step (2) is replaced by graphite powder.

[0088] Performance test results: Graphite powder loaded on PrFeO3 perovskite material with relatively large particles will affect the oxygen adsorption capacity, resulting in reduced catalytic performance of the material. The limiting current density of the composite material is high, and the Tafel slope is 283mV·dec -1 , the overpotential is also higher than that of Comparative Example 1.

[0089] Figure 1The XRD diffraction patterns of the catalysts prepared in Examples 1-3 and Comparative Example 1 are shown in FIG. As can be seen from the figure, the characteristic diffraction peaks of each material are basically consistent with the crystal plane where the main diffraction peaks of the cubic pure phase PrFeO3 (PDF#10-6418) should appear. However, other obvious characteristic diffraction peaks also appear in the catalysts of Examples 1-3. Analysis shows that these peaks correspond to the characteristic peaks of Mxene, CNT and g-C3N4, indicating that these three carbon materials are successfully doped into praseodymium ferrite.

[0090] Figure 2 The SEM images of the catalysts prepared in Comparative Example 1 (a), Example 1 (b), Example 2 (c), and Example 3 (d) show that the porous structure of PrFeO3 is destroyed into irregular particles after ball milling, the accordion structure of Mxene material has been ball milled into fragments, and PrFeO3 particles are distributed between large pieces of Mxene material; most of the CNT material wraps PrFeO3; and PrFeO3 particles are distributed between large pieces of g-C3N4 material. The specific surface area of ​​the materials increases to varying degrees, providing more active sites, which is beneficial to catalytic activity.

[0091] Figure 3 This is the XPS full energy spectrum of the catalyst prepared in Example 1-3. As can be seen from the figure, the carbon material is successfully doped into PrFeO3, and the doping of the carbon material increases the Fe 4+ The content of Fe 3+ and Fe 4+ The coexistence of can improve the conductivity of the material, thereby improving the catalytic performance, while O ads A higher content means that there are more oxygen vacancies that help improve the catalytic performance, which also indicates that the catalytic performance of the catalyst is better after the addition of carbon materials.

[0092] Figure 4 The catalysts prepared in Examples 1-3 and Comparative Example 1 were saturated with O2 at 0.1 mol·L -1 ORR polarization curve in KOH electrolyte, Figure 5 The catalysts prepared in Example 1, Example 2, Example 3 and Comparative Example 1 of the present invention were saturated with 0.1 mol·L -1 OER polarization curve in KOH electrolyte. The test results are shown in Table 1.

[0093] Table 1

[0094] project ORR half-wave potential / V Overpotential η / mV <![CDATA[OERTafel / mV·dec -1 ]]> Example 1 0.64 593 94 Example 2 0.76 591 230 Example 3 0.68 723 154 Example 4 0.67 684 192 Comparative Example 1 0.66 720 147 Comparative Example 2 0.68 - - Comparative Example 3 0.67 733 348 Comparative Example 4 0.64 759 259 Comparative Example 5 0.70 689 283

[0095] As can be seen from Table 1, the addition of carbon materials improves the ORR and OER performance of PrFeO3 materials. Compared with Comparative Example 1 (PrFeO3 without carbon materials), the addition of different carbon materials can improve the catalytic performance of the material, and the limiting current density is reduced to a certain extent, thereby improving the ORR performance, and the smaller the overpotential, the better the catalytic activity. Therefore, selecting a suitable carbon material can obtain the best ORR-OER dual-functional catalyst.

[0096] In summary, the PrFeO3 perovskite material prepared by the sol-gel method of the present invention is compounded with a specific amount of carbon material by ball milling, exposing more active sites and resulting in a larger specific surface area, thereby enhancing the conductivity of the perovskite material and increasing oxygen vacancies, thereby improving the electrocatalytic activity of the PrFeO3 perovskite material. The PrFeO3 / carbon material composite catalyst prepared by the ball milling method of the present invention has excellent ORR and OER catalytic activity, and can be used as a bifunctional catalyst in fuel cells and metal-air batteries.

[0097] The above are only preferred specific embodiments of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily thought of by a person skilled in the art within the technical scope disclosed by the present invention should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention should be based on the protection scope of the claims.

Claims

1. A PrFeO3 / carbon material composite bifunctional catalyst, characterized in that: The carbon material and PrFeO3 powder are mixed in a mass ratio of (0.6-1.2):1 and then ball-milled to obtain the mixture.

2. The PrFeO3 / carbon material composite bifunctional catalyst according to claim 1, characterized in that: The carbon material is one or more of MXene, CNT and g-C3N4.

3. The PrFeO3 / carbon material composite bifunctional catalyst according to claim 1, characterized in that: The specific preparation steps of the PrFeO3 powder include: Adding soluble praseodymium salt and soluble iron salt into deionized water, adding a complexing agent, mixing and stirring, adjusting the pH to alkaline, heating and stirring in a water bath, and drying to obtain a mixture; The mixture is ground into powder, and pre-sintered and calcined in sequence to obtain PrFeO3 powder with a perovskite structure.

4. The PrFeO3 / carbon material composite bifunctional catalyst according to claim 3, characterized in that: The soluble praseodymium salt is one or more of praseodymium chloride, praseodymium sulfate, praseodymium phosphate and praseodymium nitrate; and / or The soluble iron salt is one or more of ferric chloride, ferric sulfate and ferric nitrate; and / or The molar ratio of the praseodymium element in the soluble praseodymium salt to the iron element in the soluble iron salt is 1:

1.

5. The PrFeO3 / carbon material composite bifunctional catalyst according to claim 3, characterized in that: The molar ratio of the total amount of metal ions in the soluble praseodymium salt and the soluble iron salt to the complexing agent is 1:(1-5); and / or The complexing agent is one or two of citric acid and ethylenediaminetetraacetic acid.

6. The PrFeO3 / carbon material composite bifunctional catalyst according to claim 3, characterized in that: The mixing and stirring time is 1-8h; and / or The pH is 8-9; and / or The conditions of water bath heating and stirring are: temperature 70-90° C., time 1-8 h; and / or The pre-sintering treatment conditions are: temperature 200-500°C, time 1-8h; and / or The calcination treatment conditions are: temperature 600-900° C., time 1-8 h.

7. A method for preparing a PrFeO3 / carbon material composite bifunctional catalyst as claimed in any one of claims 1 to 6, characterized in that: The following steps are involved: The carbon material and PrFeO3 powder are ball-milled, centrifuged, washed and dried to obtain a PrFeO3 / carbon material composite bifunctional catalyst.

8. The method for preparing the PrFeO3 / carbon material composite bifunctional catalyst according to claim 7, characterized in that: The specific steps of the ball milling treatment include: adding the carbon material and PrFeO3 powder into a stainless steel ball milling jar, then adding anhydrous ethanol, and ball milling at a rotation speed of 100-500 rpm for 1-48 hours.

9. Use of the PrFeO3 / carbon material composite bifunctional catalyst as claimed in any one of claims 1 to 6 in the preparation of an air electrode.

10. Use of the PrFeO3 / carbon material composite bifunctional catalyst as claimed in any one of claims 1 to 6 in the fields of fuel cells and metal-air batteries.

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