Lafeo3 catalyst, its preparation method and application

Abstract

The application discloses a LaFeO3 catalyst and a preparation method and application thereof, the LaFeO3 catalyst is a perovskite oxide with a two-dimensional sheet structure, and contains La site defect sites and O site defect sites; the exposed crystal face of the LaFeO3 catalyst is a 100 crystal face and a 110 crystal face. The two-dimensional LaFeO3 catalyst with high crystallinity is obtained by adopting a soft template method, a structural directing agent is added to change a microatmosphere in a high-temperature calcination process, so that the structural directing agent generates gas under high-temperature conditions and plays a role of a pore-forming agent, and the method is simple and easy to implement, time consumption is short, the LaFeO3 catalyst prepared has high crystallinity and high yield.

Description

Technical Field

[0001] This application relates to a LaFeO3 catalyst, its preparation method, and its application, belonging to the field of inorganic material preparation. Background Technology

[0002] The use of fossil fuels has greatly promoted the development of human industry and provided important energy security for the formation of modern cities. At the same time, rapid industrial development and intensified human activities have also brought various problems, forcing people to consider post-treatment methods to remove polluting gases (such as H2S and CO2) and explore the establishment of a clean and sustainable energy security system. For H2S removal, in addition to commonly used H2S adsorption and absorption technologies, converting H2S into elemental sulfur is not only of significant scientific importance but also has broad application prospects. In the preparation and storage of clean energy, the use of photovoltaic cells for solar energy conversion and lithium-oxygen batteries for energy storage also have practical application value. In these application systems, perovskite catalysts have been recognized in the research field and have been partially industrialized. However, in these systems, perovskite catalysts suffer from complex reaction processes at the interface, multiple redox cycles within the catalyst, and poor thermal stability, making them unsuitable for complex operating conditions and hindering further optimization of their applications. Therefore, modifying existing perovskite catalysts to enhance their functionality and promote their development in the aforementioned application fields is particularly important.

[0003] Perovskite materials (ABO3), due to their unique structure and chemical properties, have been widely and successfully applied in various functional applications (such as catalysis, energy storage batteries, solar cells, and semiconductors). Typically, the unique structure of ABO3 is tunable, allowing the introduction of oxygen with non-stoichiometric ratios or active metals in mixed valence states, thereby altering the valence state of a constituent element and exhibiting optimized physicochemical properties, ultimately improving its application performance. Conventional ABO3 catalysts, however, exhibit only limited performance in catalysis and other applications. Therefore, extensive research has focused on improving the physicochemical properties and application performance of ABO3. This includes partially substituting A and / or B sites in ABO3 to create site defects, rationally controlling the number of oxygen vacancies to improve lattice oxygen mobility, and enhancing the redox properties of multivalent metal sites to promote application performance. However, due to the limitations of the bulk structure and surface area of ​​traditional ABO3, introducing vacancies to enhance its physicochemical properties cannot achieve sufficient optimization, hindering significant performance improvements. Summary of the Invention

[0004] To address the aforementioned issues, this application provides a simple method for preparing a functionalized two-dimensional LaFeO3 catalyst rich in defect sites. Using iron salt (active metal component) and lanthanum salt (structural metal component) as raw materials, and citric acid as a binder, a structure-directing agent is introduced to prepare the LaFeO3 catalyst rich in defect sites. Simultaneously, graphene oxide is used as a template for constructing the two-dimensional structure, thereby optimizing the defect sites and maximizing the improvement of its physicochemical properties. Based on its improved physicochemical properties, the prepared two-dimensional LaFeO3 catalyst exhibits excellent H2S catalytic conversion and energy storage performance.

[0005] According to one aspect of this application, a LaFeO3 catalyst is provided, wherein the LaFeO3 catalyst is a perovskite oxide with a two-dimensional sheet-like structure and contains La-site defect sites and O-site defect sites;

[0006] The LaFeO3 catalyst has exposed crystal planes 100 and 110.

[0007] Optionally, the crystallinity of the LaFeO3 catalyst is 85.7% to 89.4%.

[0008] According to another aspect of this application, a method for preparing a LaFeO3 catalyst is provided, the method comprising the following steps: mixing and stirring a mixed solution A containing lanthanum nitrate, ferric nitrate, citric acid and a structure directing agent with a graphene oxide solution, freeze-drying, and calcining to obtain a LaFeO3 catalyst;

[0009] The structure directing agent is urea or ammonium carbonate.

[0010] The addition of a structure-directing agent serves two purposes: firstly, it generates gas under high-temperature conditions, acting as a pore-forming agent; secondly, it improves the site defects and lattice oxygen properties on the oxide surface by creating a localized high-pressure environment. These defects are La-site defects and O-site defects. The method described in this application is simple, easy to implement, and quick. This method not only yields LaFeO3 catalysts with high crystallinity and high yield but also presents a two-dimensional plate-like structure. The high-entropy oxides prepared in this application have a crystallinity of 85.7%–89.4% and a yield of 53%–68%.

[0011] Optionally, the molar ratio of lanthanum nitrate to ferric nitrate is 1:(1-3), based on the number of moles of the metal elements in lanthanum nitrate and ferric nitrate.

[0012] Optionally, the molar ratio of lanthanum nitrate to ferric nitrate is selected from any ratio or a range between two ratios, such as 1:1, 1:1.5, 1:2, 1:2.5, and 1:3.

[0013] Optionally, the molar ratio of lanthanum nitrate, citric acid, and structure-directing agent is 1:2 to 4:4 to 8, wherein the lanthanum nitrate is expressed in molar amounts based on its metal element content.

[0014] Optionally, the mass ratio of the lanthanum nitrate to the volume ratio of the graphene oxide solution is 1 g: 20-40 mL.

[0015] Optionally, the mass ratio of the lanthanum nitrate to the volume ratio of the graphene oxide solution is selected from any ratio or a range between two ratios of 1g:20mL, 1g:25mL, 1g:30mL, 1g:35mL, and 1g:40mL.

[0016] Optionally, the concentration of the graphene oxide solution is 4.2–8.4 mg / mL.

[0017] Optionally, the concentration of the graphene oxide solution is selected from any value or a range between two values, of 4.2 mg / mL, 5.0 mg / mL, 6.0 mg / mL, 7.4 mg / mL, and 8.4 mg / mL.

[0018] Optionally, before the freeze-drying, liquid nitrogen is added during the mixing and stirring of mixed solution A and graphene oxide solution to obtain a block-shaped product, and then the product is freeze-dried; the freeze-drying conditions are: pressure 20-40 Pa, temperature -50-65℃, time 24-72 h.

[0019] Optionally, the pressure for freeze drying is selected from any value of 20 Pa, 25 Pa, 30 Pa, 35 Pa, 40 Pa, or a range between two values.

[0020] Optionally, the freeze-drying temperature is selected from any value or a range between two of -50°C, -55°C, -60°C, and -65°C.

[0021] Optionally, the freeze-drying time is selected from any value of 24h, 36h, 48h, 60h, 72h or a range between two values.

[0022] Optionally, the stirring time is 4 to 6 hours.

[0023] Optionally, the calcination temperature is 800–950°C, and the calcination time is 4–8 hours.

[0024] Optionally, the roasting temperature is selected from any value or a range between two of 800℃, 825℃, 850℃, 900℃, and 950℃.

[0025] Optionally, the roasting time is selected from any value of 4h, 5h, 6h, 7h, 8h or a range between two values.

[0026] According to another aspect of this application, a selective catalytic oxidation reaction of H2S is provided, in which a mixed gas containing H2S, O2 and an inactive equilibrium atmosphere is reacted with a catalyst to prepare elemental sulfur and water.

[0027] The catalyst is selected from the LaFeO3 catalyst prepared according to the above method.

[0028] Optionally, the space velocity of the mixed gas is 8000–16000 h⁻¹. -1 .

[0029] Optionally, the concentration ratio of H2S to O2 in the mixed gas is 1:1 to 3.

[0030] Optionally, the reaction conditions are: temperature 90–210°C, heating rate 3°C / min, and time 1–3 h.

[0031] Optionally, the inactive equilibrium atmosphere is selected from at least one of nitrogen, argon, and helium.

[0032] As a specific application, a method for the selective catalytic oxidation of H2S includes: using the prepared LaFeO3 in a catalytic reaction for the selective catalytic oxidation of H2S to elemental sulfur and water, with a catalyst dosage of 0.1 g, a reaction temperature of 90℃~210℃, and a heating rate of 3℃ / min. The feed gas is a three-component gas consisting of 5000ppm H2S, 2500ppm O2, and N2 as the equilibrium gas, with a feed gas flow rate of 20mL / min.

[0033] Optionally, the reaction temperature can be independently selected from 90℃, 120℃, 150℃, 180℃, and 210℃.

[0034] According to another aspect of this application, a lithium-oxygen battery cathode is provided, comprising carbon paper and a slurry, the slurry being coated on the surface of the carbon paper, the slurry comprising a catalyst, polyvinylidene fluoride, and N-methylpyrrolidone.

[0035] The catalyst is selected from the LaFeO3 catalyst prepared according to the above preparation method.

[0036] Optionally, the mass ratio of the catalyst, polyvinylidene fluoride, and N-methylpyrrolidone is 1:(0.1-0.25):(0.05-0.2).

[0037] As one application method, LaFeO3 catalyst and PVDF were mixed with a small amount of NMP at a mass ratio of 9:1 and ground into a slurry. This slurry was then brushed onto carbon paper with a diameter of 16 mm and dried in a vacuum drying oven at 120℃ for 12 hours to serve as the positive electrode. The lithium-oxygen battery was assembled in an Ar glove box with a positive electrode, a glass fiber separator, and a lithium metal negative electrode. The electrolyte was 1.0 M LiTFSI / TEGDME. The lithium-oxygen battery was a 2032 type button cell with a hole on one side of the positive electrode. The lithium-oxygen battery was tested in an oxygen atmosphere, with the CV curve measured at 2.0-4.5 V at a scan rate of 0.1 mV / s, and the EIS frequency range being 10. -2 ~10 5 Hz, current density and specific capacity are based on the mass of the catalyst.

[0038] The beneficial effects that this application can produce include:

[0039] 1) The method for preparing the LaFeO3 catalyst provided in this application adopts a sol-gel preprocess, uses graphene oxide as a template, and employs freeze drying and high-temperature calcination. The resulting product has a high yield, which is beneficial for large-scale preparation and application.

[0040] 2) The method for preparing the LaFeO3 catalyst provided in this application achieves the adjustment and improvement of the dual defect sites of the LaFeO3 catalyst simply by adding a structure directing agent.

[0041] 3) The LaFeO3 catalyst provided in this application has a good structure and high crystallinity, exhibiting a good lamellar structure, which is conducive to the release of oxygen from defect sites and active lattice, and can achieve simultaneous improvement in its performance in the fields of selective catalytic oxidation of H2S and energy storage. Attached Figure Description

[0042] Figure 1 The XRD patterns of LaFeO3 prepared in Examples 2 and 4 of this application are shown.

[0043] Figure 2 SEM, TEM, and HRTEM images of LaFeO3 were prepared for Example 4 of this application;

[0044] Figure 3 H2-TPR curves of LaFeO3 prepared in Comparative Examples 1 and 4 of this application;

[0045] Figure 4 The charge-discharge curves of the lithium-oxygen batteries prepared by LaFeO3 in Comparative Examples 1 and 2 and Example 4 of this application are shown.

[0046] Figure 5 The image shows the cycle stability curve of the lithium-oxygen battery prepared by LaFeO3 in Example 4 of this application. Detailed Implementation

[0047] The present application is described in detail below with reference to the embodiments, but the present application is not limited to these embodiments.

[0048] Unless otherwise specified, all raw materials used in the embodiments of this application were purchased through commercial channels.

[0049] The analysis method in the embodiments of this application is as follows:

[0050] XRD patterns of LaFeO3 were obtained using an X-ray diffractometer (XRD, Smartlab).

[0051] SEM, TEM, and HRTEM images were obtained using a field emission scanning electron microscope (SEM, JSM-7900F) and a high-resolution transmission electron microscope (JEM-F200).

[0052] The H2S conversion rate is calculated as follows in the embodiments of this application:

[0053] H2S conversion rate (%) = (H2S 入口 –H2S 出口 ) / H2S 入口 ×100%.

[0054] Example 1

[0055] 0.866 g of lanthanum nitrate hexahydrate, 0.750 g of ferric nitrate nonahydrate, 0.74 g of citric acid, and 0.48 g of urea were weighed out and transferred to a beaker containing 50 mL of deionized water. The mixture was stirred at room temperature until completely dissolved, and this solution was designated as solution A. Simultaneously, 40 mL of an 8.4 mg / mL graphene oxide solution was weighed out and stirred continuously, and this solution was designated as solution B. After both solutions were thoroughly mixed, solution A was slowly and uniformly added to solution B, with continuous stirring during the addition process. After the addition was complete, stirring was continued for 4 hours. The mixture was then slowly added to liquid nitrogen, with continuous stirring using a glass rod to prevent the product from agglomerating into large lumps. After freezing, the initial product was transferred to a freeze dryer for freeze-drying. After freeze-drying at -60°C and 40 Pa for 60 hours, the product was removed, placed in a crucible, and transferred to a muffle furnace. The mixture was then reacted at 900°C for 3 hours. After the reaction was complete and cooled to room temperature, functionalized LaFeO3 was obtained, designated as catalyst A.

[0056] Example 2

[0057] 0.866 g of lanthanum nitrate hexahydrate, 0.750 g of ferric nitrate nonahydrate, 1.48 g of citric acid, and 0.78 g of ammonium carbonate were weighed out and transferred to a beaker containing 50 mL of deionized water. The mixture was stirred at room temperature until completely dissolved, and this solution was designated as solution A. Simultaneously, 40 mL of a 4.2 mg / mL graphene oxide solution was weighed out and stirred continuously, and this solution was designated as solution B. After both solutions were thoroughly mixed, solution A was slowly and uniformly added to solution B, with continuous stirring during the addition process. After the addition was complete, stirring was continued for 4 hours. The mixture was then slowly added to liquid nitrogen, with continuous stirring using a glass rod to prevent the product from agglomerating into large lumps. After freezing, the initial product was transferred to a freeze dryer for freeze-drying. After freeze-drying at -65°C and 20 Pa for 24 hours, the product was removed, placed in a crucible, and transferred to a muffle furnace. The mixture was then reacted at 800°C for 8 hours. After the reaction was complete and cooled to room temperature, functionalized LaFeO3 was obtained, designated as catalyst B.

[0058] Example 3

[0059] 0.866 g of lanthanum nitrate hexahydrate, 0.750 g of ferric nitrate nonahydrate, 1.11 g of citric acid, and 1.17 g of ammonium carbonate were weighed out and transferred to a beaker containing 50 mL of deionized water. The mixture was stirred at room temperature until completely dissolved, and this solution was designated as solution A. Simultaneously, 40 mL of a 6.0 mg / mL graphene oxide solution was weighed out and stirred continuously, and this solution was designated as solution B. After both solutions were thoroughly mixed, solution A was slowly and uniformly added to solution B, with continuous stirring during the addition process. After the addition was complete, stirring was continued for 4 hours. The mixture was then slowly added to liquid nitrogen, with continuous stirring using a glass rod to prevent the product from agglomerating into large lumps. After freezing, the initial product was transferred to a freeze dryer for freeze-drying. After freeze-drying at -50 °C and 30 Pa for 48 hours, the product was removed, placed in a crucible, and transferred to a muffle furnace. The mixture was then reacted at 950 °C for 6 hours. After the reaction was complete and cooled to room temperature, functionalized LaFeO3 was obtained, designated as catalyst C.

[0060] Example 4

[0061] 0.866 g of lanthanum nitrate hexahydrate, 0.750 g of ferric nitrate nonahydrate, 0.74 g of citric acid, and 1.108 g of urea were weighed out and transferred to a beaker containing 50 mL of deionized water. The mixture was stirred at room temperature until completely dissolved, and this solution was designated as solution A. Simultaneously, 40 mL of a 4.2 mg / mL graphene oxide solution was weighed out and stirred continuously, and this solution was designated as solution B. After both solutions were thoroughly mixed, solution A was slowly and uniformly added to solution B, with continuous stirring during the addition process. After the addition was complete, stirring was continued for 4 hours. The mixture was then slowly added to liquid nitrogen, with continuous stirring using a glass rod to prevent the product from agglomerating into large lumps. After freezing, the initial product was transferred to a freeze dryer for freeze-drying. After freeze-drying at -55 °C and 20 Pa for 72 hours, the product was removed, placed in a crucible, and transferred to a muffle furnace. The mixture was then reacted at 900 °C for 8 hours. After the reaction was complete and cooled to room temperature, functionalized LaFeO3 was obtained, designated as catalyst D.

[0062] Comparative Example 1

[0063] 0.866 g of lanthanum nitrate hexahydrate, 0.750 g of ferric nitrate nonahydrate, and 0.74 g of citric acid were weighed out and transferred to a beaker containing 50 mL of deionized water. The mixture was stirred at room temperature until completely dissolved, and this solution was denoted as solution A. Solution A was then continuously stirred in a 90°C water bath until a gel formed. Simultaneously, the gel product was placed in a crucible and transferred to a muffle furnace, where it was reacted at 900°C for 8 hours. After the reaction was completed and cooled to room temperature, LaFeO3 was obtained, denoted as catalyst E.

[0064] Comparative Example 2

[0065] 0.866 g of lanthanum nitrate hexahydrate, 0.750 g of ferric nitrate nonahydrate, 0.74 g of citric acid, and 0.72 g of urea were weighed out separately. These reagents were then transferred to a beaker containing 50 mL of deionized water and stirred at room temperature until completely dissolved, denoted as solution A. Solution A was then continuously stirred in a 90°C water bath until a gel formed. Simultaneously, the gel product was placed in a crucible and transferred to a muffle furnace, where it was reacted at 900°C for 8 hours. After the reaction was complete and cooled to room temperature, LaFeO3 was obtained, denoted as catalyst F.

[0066] The obtained LaFeO3 was analyzed and tested accordingly:

[0067] Figure 1The XRD patterns of LaFeO3 prepared in Examples 2 and 4 are shown. As can be seen from the figures, both samples exhibit sharp diffraction peaks, indicating high crystallinity. Further analysis revealed that the prepared LaFeO3 samples all displayed diffraction peaks characteristic of perovskites, confirming the successful synthesis of perovskite-type oxides. Furthermore, changes in reaction conditions and preparation methods did not affect the crystal structure of the prepared LaFeO3, demonstrating the universality of this method.

[0068] Figure 2 These are electron micrographs of LaFeO3 prepared in Experimental Example 4, where (a) is a scanning electron microscope (SEM) image, (b) is a transmission electron microscope (TEM) image, and (c) is a high-resolution transmission electron microscope (HRTEM) image. Figure 2 It can be seen that the prepared LaFeO3 exhibits a large plate-like shape, with the exposed crystal planes mainly being the 100 and 110 crystal planes. At the same time, it can also be seen that the lattice stripes on the surface of catalyst D show certain defects.

[0069] Figure 3 The H2-TPR curves are for Comparative Example 1 and Experimental Example 4. Figure 3 As shown, catalyst E exhibits only one obvious H2 reduction peak on its surface, located around 440℃, which is attributed to Fe. 3+ The reduction of H2 occurs. Catalyst D exhibits both high-temperature and low-temperature H2 reduction peaks, located near 457℃ and 613℃ respectively, which can be attributed to Fe. 3+ To Fe 2+ and Fe 2+ The reduction of Fe was observed. This result indicates that the construction of the two-dimensional structure facilitates the reduction of surface Fe species, thereby benefiting the catalytic reaction.

[0070] The test conditions for applying the catalysts of each embodiment and comparative example to the selective oxidation of H2S were as follows: catalyst dosage was 0.1 g, reaction temperature was 150 °C, and heating rate was 3 °C / min. The feed gas was a three-component gas consisting of 5000 ppm H2S, 2500 ppm O2, and equilibrium gas N2, with a feed gas flow rate of 20 mL / min.

[0071] The stability tests of the catalysts used in the examples and comparative examples for the selective oxidation of H2S were conducted on the same apparatus under the following conditions: catalyst loading of 0.1 g, reaction temperature of 150 °C, feed gas flow rate of 40 mL / min, and long-term stability test time of 40 h. The catalyst activity and stability results in the examples are expressed as H2S conversion rate, and the H2S concentration was determined using online chromatography.

[0072] The H2S conversion rates of LaFeO3 prepared in Examples 1 to 4 and Comparative Examples 1 and 2 of this application are shown in Table 1:

[0073] Table 1

[0074]

[0075] In Examples 1-4, LaFeO3 oxide catalysts were prepared using template agents and structure-directing agents, with catalyst D exhibiting excellent H2S conversion. Although the overall H2S conversion was low in the low-temperature stage (90-150°C), it was higher than that of the catalysts prepared in other examples, especially the comparative catalyst. Further increasing the reaction temperature revealed a significant improvement in H2S conversion, reaching 82.9% at 180°C, and complete H2S conversion was achieved with further temperature increases. Furthermore, after a stability test at 210°C for 40 hours, the conversion rate remained almost unchanged. Although the overall performance of the catalysts prepared in Examples 1-3 was lower than that of catalyst A, they still exhibited good catalytic performance and thermal stability. Conventional LaFeO3 catalysts prepared without the addition of structure-directing agents and using traditional methods not only exhibit poor low-temperature performance, but also have poor high-temperature performance and catalytic stability. This is partly due to the lack of defect sites, which hinders the activation of lattice oxygen; and partly due to the traditional bulk morphology, which also prevents the exposure of defect sites and fails to maximize the activation of lattice oxygen, thus hindering the improvement of catalytic performance.

[0076] LaFeO3 catalyst and PVDF were mixed with a small amount of NMP at a mass ratio of 9:1 and ground into a slurry. This slurry was then brushed onto carbon paper with a diameter of 16 mm and dried in a vacuum drying oven at 120℃ for 12 hours to serve as the positive electrode. The lithium-oxygen battery was assembled in an Ar glove box using a positive electrode, a glass fiber separator, and a lithium metal negative electrode. The electrolyte was 1.0 M LiTFSI / TEGDME. The lithium-oxygen battery was a 2032 type button cell with a hole on one side of the positive electrode. The lithium-oxygen battery was tested in an oxygen atmosphere. The CV curve was measured at a scan rate of 0.1 mV / s from 2.0 to 4.5 V, and the EIS frequency range was 10⁻² to 10⁵ Hz. The current density and specific capacity were based on the mass of the catalyst.

[0077] from Figure 4 As can be seen from the deep charge-discharge curves of lithium-oxygen batteries assembled with catalysts D, E, and F, it can be concluded that the lithium-oxygen battery assembled with catalyst D has a lower charging overpotential, and its discharge specific capacity is as high as 24251 mAh / g at a current density of 200 mA / g, which is much higher than the discharge specific capacity of lithium-oxygen batteries assembled with catalysts E and F (catalyst E: 11773 mAh / g, catalyst D: 10495 / 5644 mAh / g). Meanwhile, from... Figure 5As can be seen, its performance did not decay after 160 charge-discharge cycles (1600 h), indicating that catalyst D exhibits excellent stability.

[0078] The above description is merely a few embodiments of this application and is not intended to limit this application in any way. Although this application discloses preferred embodiments as described above, it is not intended to limit this application. Any changes or modifications made by those skilled in the art without departing from the scope of the technical solution of this application using the disclosed technical content are equivalent to equivalent implementation cases and fall within the scope of the technical solution.

Claims

1. A LaFeO3 catalyst, characterized in that, The LaFeO3 catalyst is a perovskite oxide with a two-dimensional sheet-like structure, and contains La-site defect sites and O-site defect sites. The LaFeO3 catalyst has exposed crystal planes 100 and 110.

2. The LaFeO3 catalyst according to claim 1, characterized in that, The crystallinity of the LaFeO3 catalyst is 85.7%~89.4%.

3. A method for preparing the LaFeO3 catalyst according to claim 1 or 2, characterized in that, Includes the following steps: A mixed solution A containing lanthanum nitrate, ferric nitrate, citric acid, and a structure-directing agent was mixed and stirred with a graphene oxide solution, freeze-dried, and calcined to obtain a LaFeO3 catalyst. The structure directing agent is urea or ammonium carbonate.

4. The preparation method according to claim 3, characterized in that, The molar ratio of lanthanum nitrate to ferric nitrate is 1:(1~3), based on the number of moles of the metal elements in lanthanum nitrate and ferric nitrate.

5. The preparation method according to claim 3, characterized in that, The molar ratio of lanthanum nitrate, citric acid, and structure directing agent is 1:2~4:4~8, wherein the lanthanum nitrate is calculated based on the number of moles of the metal element it contains.

6. The preparation method according to claim 3, characterized in that, The mass ratio of lanthanum nitrate to the volume ratio of the graphene oxide solution is 1 g: 20~40 mL.

7. The preparation method according to claim 3, characterized in that, The concentration of the graphene oxide solution is 4.2~8.4 mg / mL.

8. The preparation method according to claim 3, characterized in that, The freeze-drying conditions are: pressure 20~40Pa, temperature -50~-65℃, time 24~72h.

9. The preparation method according to claim 3, characterized in that, The stirring time is 4 to 6 hours.

10. The preparation method according to claim 3, characterized in that, The roasting temperature is 800~950℃, and the roasting time is 4~8h.

11. A selective catalytic oxidation reaction of H2S, characterized in that, A mixed gas containing H2S, O2, and an inactive equilibrium atmosphere is reacted with a catalyst to produce elemental sulfur and water. The catalyst is selected from the LaFeO3 catalyst according to claim 1 or 2 or the LaFeO3 catalyst obtained by the preparation method according to any one of claims 3 to 10.

12. The selective catalytic oxidation reaction of H2S according to claim 11, characterized in that, The space velocity of the mixed gas is 8000~16000 h⁻¹ -1 .

13. The selective catalytic oxidation reaction of H2S according to claim 11, wherein the concentration ratio of H2S to O2 in the mixed gas is 1:1~3.

14. The selective catalytic oxidation reaction of H2S according to claim 11, wherein the reaction conditions are: temperature 90~210℃, heating rate 3~5℃ / min, and time 1~3h.

15. The H2S selective catalytic oxidation reaction according to claim 11, wherein the inactive equilibrium atmosphere is selected from at least one of nitrogen, argon, and helium.

16. A positive electrode for a lithium-oxygen battery, characterized in that, It includes carbon paper and a slurry, the slurry being coated on the surface of the carbon paper, the slurry comprising a catalyst, polyvinylidene fluoride, and N-methylpyrrolidone; The catalyst is selected from the LaFeO3 catalyst according to claim 1 or 2 or the LaFeO3 catalyst obtained by the preparation method according to any one of claims 3 to 10.

17. The lithium-oxygen battery positive electrode according to claim 16, characterized in that, The mass ratio of the catalyst, polyvinylidene fluoride, and N-methylpyrrolidone is 1:(0.1~0.25):(0.05~0.2).

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