Magnetoplumbite-type oxide, and preparation method therefor and use thereof

Abstract

Disclosed in the present invention are a magnetoplumbite-type oxide, and a preparation method therefor and the use thereof. The preparation method therefor comprises the following steps: S1, dissolving a rare earth nitrate, a transition metal nitrate and Al(NO3)3 in deionized water to obtain a mixed nitrate solution; S2, adding citric acid monohydrate to the mixed nitrate solution, heating and stirring the resulting mixture, and evaporating same to obtain a transparent gel; S3, drying the gel to obtain a loose and porous xerogel; S4, performing a first high-temperature treatment on the xerogel in an air atmosphere at 650-950°C to prepare a precursor; and S5, grinding and pulverizing the precursor, grinding and mixing the precursor with a soluble salt until uniform, and then performing a second high-temperature treatment in an air atmosphere at 1500-2000°C to prepare a magnetoplumbite-type oxide. The preparation method of the present invention has low costs, is simple and feasible, and has a wide range of application, and when applied to a lithium-sulfur battery, the prepared magnetoplumbite-type oxide helps improve the performance of the battery.

Description

A magnetoplumbite-type oxide and a preparation method and application thereof TECHNICAL FIELD

[0001] The present application belongs to the technical field of electrocatalytic materials, and particularly relates to a magnetoplumbite-type oxide and a preparation method and application thereof. BACKGROUND

[0002] Suffering from the problems of poor intrinsic conductivity and low utilization of elemental sulfur, the industrialization prospect of sulfur-based energy storage batteries is greatly weakened. In order to overcome these challenges, developing advanced elemental sulfur carriers is the key to improving the performance of the battery (Nat. Nanotechnol. 2020, 15, 231).

[0003] Metal oxides with metal and oxygen vacancies have rich electronic structures, excellent mechanical properties, and strong coupling with elemental sulfur, which can be used as sulfur storage sites to improve the stability of the battery and exhibit excellent potential. However, the liquid polysulfide has high affinity, which is not conducive to subsequent electrocatalytic conversion, so it is crucial to improve the intrinsic electrocatalytic activity of the oxide. Based on this, phase engineering is an effective strategy to improve the intrinsic electrocatalytic activity of the material. On the one hand, the enriched heterogeneous phase and interface can be used as potential catalytically active sites to adjust the adsorption / desorption energy of intermediates (Chemical Reviews, 2024, 124, 1247). On the other hand, the control of vacancies and the implementation of topological ion exchange (TIE) can exhibit significant multiphase interaction and interface effect, further improving the catalytic activity of the material (Nat. Commun. 2023, 14, 5389).

[0004] In the face of the above problems existing in the multi-phase / multi-state / multi-electron reactions of sulfur-based electrodes, how to improve the comprehensive performance of oxide sulfur storage batteries through phase engineering is still a difficulty. In order to solve the above problems, the present application is thus obtained.

[0005] SUMMARY

[0006] In order to solve at least one of the above technical problems, the present application provides a magnetoplumbite-type oxide and a preparation method and application thereof. The present application first prepares a precursor by sol-gel method, and then combines with molten salt method for high-temperature treatment, to obtain a powder with finer particles and uniform particle size distribution. The magnetoplumbite-type oxide prepared by the present application exhibits excellent electrocatalytic performance in the reduction process of elemental sulfur, providing theoretical support and technical breakthrough for the practical application of magnetoplumbite-type oxide in sulfur reduction, and further accelerating the practical process of sulfur-based batteries.

[0007] The technical scheme of the present application is as follows:

[0008] The application provides a preparation method of a magnetoplumbite-type oxide, comprising the following steps:

[0009] S1, dissolving rare earth nitrate Ln(NO3)3·6H2O, transition metal nitrate Me(NO3)2 and Al(NO3)3 in deionized water to obtain a mixed nitrate solution;

[0010] S2, adding citric acid monohydrate to the mixed nitrate solution obtained in the step S1, heating and stirring, and evaporating to obtain a transparent gel;

[0011] S3, drying the gel obtained in the step S2 to obtain a loose and porous dry gel;

[0012] S4, performing first high-temperature treatment on the dry gel obtained in the step S3 in an air atmosphere at 650-950 ℃ to obtain a precursor;

[0013] S5, grinding and crushing the precursor obtained in the step S4, uniformly mixing with a salt, and performing second high-temperature treatment in an air atmosphere at 1500-2000 ℃ to obtain the magnetoplumbite-type oxide.

[0014] Preferably, in the step S1, the molar ratio of the rare earth nitrate Ln(NO3)3·6H2O, the transition metal nitrate Me(NO3)2 and Al(NO3)3 is 1:1:11; and the total concentration of the obtained mixed nitrate solution is 0.01-1 g / L, that is, the total concentration of the three kinds of nitrates.

[0015] Preferably, in the step S1, the rare earth nitrate Ln(NO3)3·6H2O is any one of Y(NO3)3·6H2O, La(NO3)3·6H2O, Pr(NO3)3·6H2O, Nd(NO3)3·6H2O, Sm(NO3)3·6H2O, Eu(NO3)3·6H2O, Gd(NO3)3·6H2O, Tm(NO3)3·6H2O, Ce(NO3)3·6H2O and Yb(NO3)3·6H2O; and the transition metal nitrate Me(NO3)2 is any one of Mg(NO3)2, Fe(NO3)2, Co(NO3)2, Ni(NO3)2, Cu(NO3)2, Zr(NO3)2 and Zn(NO3)2.

[0016] Preferably, in the step S2, the molar amount of the citric acid monohydrate is 1-10 times of the total molar amount of metal ions in the mixed nitrate solution.

[0017] The heating and stirring are performed at 65-100 ℃, and the transparent gel is obtained by evaporation.

[0018] Preferably, in step S3, the drying conditions are: placing the gel in an oven at 50–200°C for 5–12 hours.

[0019] Preferably, in step S4, the first high-temperature treatment lasts for 1 to 5 hours.

[0020] Preferably, in step S5, the second high-temperature treatment takes 1 to 10 hours.

[0021] Preferably, in step S5, the dissolved salt is a mixture of NaCl and KCl, and the total mass of the dissolved salt is 2 to 20 times the mass of the precursor.

[0022] This invention also provides a magnetoplumbite-type oxide, prepared by the above-described method, which has a magnetoplumbite structure and has the chemical formula LnMeAl. 11 O 19 Ln is any one of the rare earth elements Y, La, Pr, Nd, Sm, Eu, Gd, Tm, Ce and Yb, and Me is any one of the transition metal elements Mg, Fe, Co, Ni, Cu, Zr and Zn.

[0023] The present invention also provides the application of the above-mentioned magnetic plume oxide as a catalyst material in sulfur reduction electrocatalysis. More preferably, the above-mentioned magnetic plume oxide can be used to prepare lithium-sulfur batteries and can be used as a catalyst material for lithium-sulfur batteries.

[0024] The beneficial effects of this invention are:

[0025] This invention combines the sol-gel method and the molten salt method to synergistically prepare the magnetoplumble oxide LnMeAl. 11 O 19 Compared with oxides prepared by other single methods (such as solid-state method, sol-gel method and molten salt method), the LnMeAl prepared in this invention has better performance. 11 O 19 It exhibits stronger catalytic activity, which can significantly improve the reaction kinetics of sulfur-based batteries and is expected to fully realize the stable cycling performance of batteries at high rates. In addition, the preparation method of the present invention has the advantages of low cost, simplicity and ease of implementation, and wide applicability. Attached Figure Description

[0026] The present invention will be further described below with reference to the accompanying drawings and embodiments:

[0027] Figure 1 shows the XRD pattern of the magnetoplumble oxide material prepared in Example 1;

[0028] Figure 2 shows the SEM morphology of the magnetic lumpy oxide material prepared in Example 2;

[0029] Figure 3 is the electrocatalytic performance of the magnetoplumbite-type oxide material prepared in Example 3;

[0030] Figure 4 is the electrocatalytic performance of the magnetoplumbite-type oxide material prepared in Example 4;

[0031] Figure 5 is the electrocatalytic performance of the magnetoplumbite-type oxide material prepared in Example 5;

[0032] Figure 6 is the electrocatalytic performance of the magnetoplumbite-type oxide material prepared in Example 6;

[0033] Figure 7 is the battery cycle performance of the magnetoplumbite-type oxide material prepared in Example 7;

[0034] Figure 8 is the SEM morphology of the product prepared in Comparative Example 1;

[0035] Figure 9 is the XRD pattern of the product prepared in Comparative Example 2;

[0036] Figure 10 is the electrocatalytic performance of the product prepared in Comparative Example 2. DETAILED DESCRIPTION

[0037] In order to make the objectives, technical solutions and advantages of the present application clearer, further detailed description will be given below in conjunction with specific embodiments and with reference to the drawings. It should be understood that these descriptions are only exemplary and are not intended to limit the scope of the present application. In addition, in the following description, the description of well-known structures and techniques is omitted to avoid unnecessary confusion of the concept of the present application.

[0038] Example 1

[0039] This example provides a magnetoplumbite-type oxide prepared based on a sol-gel precursor method:

[0040] Sm(NO3)3·6H2O and Mg(NO3)2 and Al(NO3)3 were weighed according to a molar ratio of 1:1:11 and dissolved in deionized water, respectively, to obtain a mixed nitrate solution with a total concentration of 0.1 g / L. After stirring for 10 minutes, 5 times the total number of moles of metal ions of citric acid monohydrate was added to the above obtained nitrate solution, and heated and stirred at 80°C, and rotary evaporation was performed to obtain a transparent gel.

[0041] The above gel was placed in an oven at 155°C for 7h, and it was observed that a loose and porous xerogel was obtained.

[0042] The above xerogel was then loaded into an alumina crucible and placed in a muffle furnace, heated at 850°C in an air atmosphere for 2h to prepare a precursor.

[0043] The above precursor was ground and mixed with 10 times by weight of molten salt (molar ratio of NaCl:KCl = 1:1) and then loaded into an alumina crucible and placed in a muffle furnace and heated at 1550°C for 1 h in an air atmosphere to obtain SmMgAl 11 O 19 powder.

[0044] Analysis: The XRD pattern of the prepared magnetoplumbite-type oxide is shown in Figure 1. It can be seen that the prepared powder is SmMgAl 11 O 19 and no other metal compound impurities are present on the substrate.

[0045] Example 2

[0046] This example provides a method for preparing a magnetoplumbite-type oxide based on a sol-gel precursor:

[0047] Eu(NO3)3.6H2O and Co(NO3)2 and Al(NO3)3 were weighed according to a molar ratio of 1:1:11 and dissolved in deionized water to obtain a mixed nitrate solution with a total concentration of 0.3 g / L. After stirring for 10 minutes, 6 times the total molar amount of monohydrate citric acid was added to the above obtained nitrate solution, heated and stirred at 75°C, and rotary evaporated to obtain a transparent gel.

[0048] The above gel was placed in an oven at 135°C for 9 h until a loose and porous dry gel was obtained.

[0049] The above dry gel was then loaded into an alumina crucible and placed in a muffle furnace and heated at 875°C for 2.5 h in an air atmosphere to obtain a precursor.

[0050] The above precursor was ground and mixed with 12 times by weight of molten salt (molar ratio of NaCl:KCl = 1:1) and then loaded into an alumina crucible and placed in a muffle furnace and heated at 1575°C for 6 h in an air atmosphere to obtain EuCoAl 11 O 19 powder.

[0051] Analysis: The SEM pattern of the prepared magnetoplumbite-type oxide is shown in Figure 2. It can be seen that the prepared powder particles are fine and uniform under SEM observation, with a single particle size of 600-800 nm.

[0052] Example 3

[0053] This example provides a method for preparing a magnetoplumbite-type oxide based on a sol-gel precursor:

[0054] Sm(NO3)3.6H2O and Mg(NO3)2 and Al(NO3)3 were weighed according to the mole ratio of 1:1:11 and dissolved in deionized water respectively, and the total concentration of the mixed nitrate solution obtained was 0.25 g / L. After stirring for 10 minutes, 6.6 times the total number of moles of metal ions of citric acid monohydrate was added to the above obtained nitrate solution, and heated and stirred at 90°C, and a transparent gel was obtained by rotary evaporation.

[0055] The above gel was placed in an oven at 100°C for 7.5h, and a loose porous xerogel was obtained.

[0056] The above xerogel was then loaded into an alumina crucible and placed in a muffle furnace, heated at 820°C in an air atmosphere for 3h to obtain a precursor.

[0057] The above precursor was ground and crushed, and mixed uniformly with 11 times by weight of molten salt (molar ratio of NaCl:KCl = 1:1), and then loaded into an alumina crucible and placed in a muffle furnace, heated at 1610°C in an air atmosphere for 2h to obtain SmMgAl 11 O 19 powder.

[0058] To test the electrocatalytic activity of the sulfur-based battery, 80wt.% of sulfur-containing electrode material (30% of SmMgAl 11 O 19 powder, 70% of elemental sulfur), 10wt.% of Super P and 10wt.% of polyvinylidene fluoride (PVDF) were thoroughly mixed in a mortar, and an appropriate amount of N-methyl-2-pyrrolidone (NMP) (Aldrich, 99% battery grade) solvent was added, and after stirring for 8h, a uniform slurry was obtained. Then, the slurry was uniformly coated onto the positive current collector, and placed in a vacuum oven at 60°C for about 10h, and after cooling to room temperature, it was cut into standard circular electrode sheets on a punching machine, and weighed for use. The CR2016 button half-cell was assembled in an inert gas Ar-filled glove box (H2O and O2, <10 -5 %); the battery separator was a polymeric material polypropylene (PP) separator, model Celgard 2400. High-purity Li sheet was used as the negative electrode. The electrolyte contained 1M LiTFSI and 1wt.% of LiNO3 by mass fraction, and the solvent was a mixed solution of DOL and DME (volume ratio 1:1). The cyclic voltammetry test (CV, voltage range: 1.7-2.8V) was carried out using a CHI760E electrochemical workstation.

[0059] Analysis: The electrocatalytic performance of the prepared magnetoplumbite-type oxide is shown in Figure 3. Two obvious reduction peaks appear in the discharge platform of the reduction reaction, reaching the maximum peak current at 2.289 V and 1.981 V, respectively, corresponding to the stepwise lithiation reaction of the sulfur positive electrode, i.e., the conversion of elemental sulfur into long-chain lithium polysulfide: S8→ Li2S x (4≤x≤8) and the conversion of long-chain lithium polysulfide into short-chain lithium polysulfide: Li2S x (4≤x≤8)→Li2S x (1≤x≤3). It can be seen that the prepared SmMgAl 11 O 19 exhibits good performance as an electrocatalyst for sulfur-based batteries.

[0060] Example 4

[0061] This example provides a method for preparing a magnetoplumbite-type oxide based on a sol-gel precursor:

[0062] Ce(NO3)3·6H2O and Ni(NO3)2 and Al(NO3)3 in a molar ratio of 1:1:11 were weighed and dissolved in deionized water, respectively, to obtain a mixed nitrate solution with a total concentration of 0.45 g / L. After stirring for 10 minutes, 9 times the total molar amount of monohydrated citric acid was added to the above-obtained nitrate solution, which was heated and stirred at 95°C, and a transparent gel was obtained by rotary evaporation.

[0063] The above gel was placed in an oven at 175°C for 8 hours, and a loose and porous dry gel was observed.

[0064] The above dry gel was then loaded into an alumina crucible and placed in a muffle furnace, heated at 870°C in an air atmosphere for 2 hours to obtain a precursor.

[0065] The above precursor was ground and crushed, and then mixed uniformly with 12 times the weight of molten salt (molar ratio of NaCl:KCl = 1:1) to obtain a mixture, which was then loaded into an alumina crucible and placed in a muffle furnace, heated at 1600°C in an air atmosphere for 2 hours to obtain a CeNiAl 11 O 19 powder.

[0066] A sulfur-based battery was prepared according to the method in Example 3, and the magnetoplumbite-type oxide therein was replaced with the CeNiAl 11 O 19 powder of this example. Cyclic voltammetry (CV, voltage range: 1.7-2.8 V) was studied using a CHI760E electrochemical workstation.

[0067] The electrocatalytic performance of the prepared magnetoplumbite-type oxide is shown in Figure 4. Two obvious reduction peaks appear in the discharge platform of the reduction reaction, reaching the maximum peak current at 2.283 V and 1.976 V, respectively, corresponding to the stepwise lithiation reaction of the sulfur positive electrode, i.e., the conversion of elemental sulfur into long-chain lithium polysulfide: S8→ Li2S x (4≤x≤8) and the conversion of long-chain lithium polysulfide into short-chain lithium polysulfide: Li2S x (4≤x≤8)→Li2S x (1≤x≤3). It can be seen that the prepared CeNiAl 11 O 19 exhibits good performance as an electrocatalyst for sulfur-based batteries.

[0068] Example 5

[0069] This example provides a method for preparing a magnetoplumbite-type oxide based on a sol-gel precursor method:

[0070] La(NO3)3·6H2O and Mg(NO3)2 and Al(NO3)3 are weighed in a molar ratio of 1:1:11 and dissolved in deionized water, respectively, to obtain a mixed nitrate solution with a total concentration of 0.1 g / L. After stirring for 10 minutes, 3 times the total number of moles of metal ions of citric acid monohydrate is added to the above-obtained nitrate solution, and heated and stirred at 70°C. Transparent gel is obtained by rotary evaporation.

[0071] The above gel is placed in an oven at 80°C for 5 hours, and a loose and porous dry gel is observed.

[0072] The above dry gel is then loaded into an alumina crucible and placed in a muffle furnace, heated at 750°C in an air atmosphere for 2 hours to obtain a precursor.

[0073] The above precursor is ground and crushed, and then mixed uniformly with 8 times the weight of molten salt (NaCl:KCl=1:1) and loaded into an alumina crucible, which is then placed in a muffle furnace and heated at 1600°C in an air atmosphere for 3.5 hours to obtain LaMgAl 11 O 19 powder.

[0074] A sulfur-based battery is prepared according to the method in Example 3, with the magnetoplumbite-type oxide therein being replaced by the LaMgAl 11 O 19 powder of this example. Cyclic voltammetry (CV, voltage range: 1.7-2.8 V) is studied using a CHI760E electrochemical workstation.

[0075] Analysis: The electrocatalytic performance of the prepared magnetoplumbite-type oxide is shown in Figure 5. Two obvious reduction peaks appear in the discharge platform of the reduction reaction, reaching the maximum peak current at 2.213 V and 1.856 V, respectively, corresponding to the stepwise lithiation reaction of the sulfur positive electrode, i.e., the conversion of elemental sulfur into long-chain lithium polysulfides: S8→ Li2S x (4≤x≤8) and the conversion of long-chain lithium polysulfides into short-chain lithium polysulfides: Li2S x (4≤x≤8)→Li2S x (1≤x≤3). It can be seen that the prepared LaMgAl 11 O 19 exhibits good performance as an electrocatalyst for sulfur-based batteries.

[0076] Example 6

[0077] This example is directed to providing a magnetoplumbite-type oxide prepared based on a sol-gel precursor method:

[0078] Gd(NO3)3·6H2O and Zn(NO3)2 and Al(NO3)3 were weighed in a molar ratio of 1:1:11 and dissolved in deionized water, respectively, to obtain a mixed nitrate solution with a total concentration of 0.5 g / L. After stirring for 10 minutes, 5.5 times the total number of moles of metal ions of monohydrated citric acid was added to the above-obtained nitrate solution, and the mixture was heated and stirred at 80°C. A transparent gel was obtained by rotary evaporation.

[0079] The above gel was placed in an oven at 165°C for 6 hours, and a loose and porous dry gel was observed.

[0080] The above dry gel was then loaded into an alumina crucible and placed in a muffle furnace, and heated at 900°C for 2 hours in an air atmosphere to obtain a precursor.

[0081] The above precursor was ground and crushed, and then mixed with 10 times the weight of molten salt (molar ratio of NaCl:KCl = 1:1) to obtain a uniform mixture. The mixture was then loaded into an alumina crucible and placed in a muffle furnace, and heated at 1500°C for 2.5 hours in an air atmosphere to obtain a GdZnAl 11 O 19 powder.

[0082] A sulfur-based battery was prepared according to the method in Example 3, and the magnetoplumbite-type oxide therein was replaced with the GdZnAl 11 O 19 powder of this example. Cyclic voltammetry (CV, voltage range: 1.7-2.8 V) was studied using a CHI760E electrochemical workstation.

[0083] Analysis: The electrocatalytic performance of the prepared magnetoplumbite-type oxide is shown in Figure 6. Two obvious reduction peaks appear in the discharge platform of the reduction reaction, reaching the maximum peak current at 2.246 V and 1.952 V, respectively, corresponding to the stepwise lithiation reaction of the sulfur positive electrode, i.e., the conversion of elemental sulfur into long-chain lithium polysulfide: S8→ Li2S x (4≤x≤8) and the conversion of long-chain lithium polysulfide into short-chain lithium polysulfide: Li2S x (4≤x≤8)→Li2S x (1≤x≤3). It can be seen that the prepared GdZnAl 11 O 19 exhibits good performance as an electrocatalyst for sulfur-based batteries.

[0084] Example 7

[0085] This example provides a method for preparing a magnetoplumbite-type oxide based on a sol-gel precursor method:

[0086] Eu(NO3)3·6H2O and Mg(NO3)2 and Al(NO3)3 in a molar ratio of 1:1:11 were weighed and dissolved in deionized water, respectively, to obtain a mixed nitrate solution with a total concentration of 0.6 g / L. After stirring for 10 minutes, 7 times the total molar amount of monohydrated citric acid was added to the obtained nitrate solution, and the mixture was heated and stirred at 90°C. A transparent gel was obtained by rotary evaporation.

[0087] The gel was placed in an oven at 160°C for 7 hours, and a loose and porous dry gel was obtained.

[0088] The dry gel was then loaded into an alumina crucible and placed in a muffle furnace, and heated at 850°C for 2 hours in an air atmosphere to obtain a precursor.

[0089] The precursor was ground and crushed, and then mixed with 9 times the weight of molten salt (molar ratio of NaCl:KCl = 1:1) to obtain a uniform mixture. The mixture was then loaded into an alumina crucible and placed in a muffle furnace, and heated at 1550°C for 3.5 hours in an air atmosphere to obtain EuMgAl 11 O 19 powder.

[0090] Analysis: The prepared magnetoplumbite-type oxide was subjected to sulfur infiltration at 155°C to obtain a sulfur storage positive electrode material EuMgAl 11 O 19 / S. The long cycle performance of the assembled button cell is shown in Figure 7. When the current is increased and the cycle period is extended, the EuMgAl 11 O 19 / S composite electrode exhibits more stable high-rate performance, and the specific capacity is 3.7 mg / cm2 The current density of 2C at high area loading is stable for at least 560 cycles.

[0091] Comparative Example 1

[0092] Eu(NO3)3.6H2O and Co(NO3)2 and Al(NO3)3 were weighed according to a molar ratio of 1:1:11 and dissolved in deionized water respectively to obtain a mixed nitrate solution with a total concentration of 0.3 g / L. After stirring for 10 minutes, 6 times the total molar amount of citric acid monohydrate was added to the above obtained nitrate solution, and heated and stirred at 75°C. A transparent gel was obtained by rotary evaporation.

[0093] The above gel was placed in an oven at 135°C for 9h, and a loose porous xerogel was obtained.

[0094] The above xerogel was then loaded into an alumina crucible and placed in a muffle furnace, heated at 875°C for 2.5h in an air atmosphere to obtain a precursor.

[0095] The above precursor was ground and placed in a muffle furnace, heated at 1575°C for 6h in an air atmosphere to obtain EuCoAl 11 O 19 powder.

[0096] Analysis: The SEM spectrum of the prepared product is shown in Figure 8. The magnetoplumbite-type oxide sintered by the single solid phase method has a large amount of agglomeration and is not fine and uniform nanoscale particles. Compared with Example 2, when the related processing operations of uniformly mixing the molten salt grinding are not added in the synthesis conditions, the prepared powder morphology is not fine and uniform particles.

[0097] Comparative Example 2

[0098] Metal oxides Sm2O3, FeO and Al2O3 powders were weighed according to a molar ratio of 1:2:22, and the powders were mixed in a planetary ball mill. The obtained mixed powders were loaded into an alumina crucible and placed in a muffle furnace, heated at 1600°C for 4h in an air atmosphere to obtain a powder.

[0099] Analysis: The XRD spectrum of the prepared product is shown in Figure 9. It can be seen that the prepared powder cannot obtain a pure phase SmFeAl 11 O 19 , and also contains other metal compound impurities Al2O3 and FeAl2O4.

[0100] A sulfur-based battery was prepared according to the method in Example 3, replacing the magnetoplumbite-type oxide therein with the powder prepared in this comparative example. The cyclic voltammetry (CV, voltage range: 1.7-2.8 V) was studied using a CHI760E electrochemical workstation.

[0101] The electrocatalytic performance of the prepared product is shown in Figure 10. Only one reduction peak appears in the discharge plateau of the reduction reaction, reaching the maximum peak current at 2.165 V, corresponding to the lithiation reaction of the sulfur positive electrode, the conversion of elemental sulfur into lithium polysulfides: S8→ Li2S x (1≤x≤8). It can be seen that when the synthesis conditions are not strictly according to the claims (sol-gel method + molten salt), the prepared powder is not in the form of fine and uniform particles, SmFeAl 11 O 19 and does not exhibit good electrocatalytic performance.

[0102] It should be understood that the above specific embodiments of the present application are only used for illustrative or explanatory purposes of the principles of the present application, and do not constitute a limitation on the present application. Therefore, any modifications, equivalent replacements, improvements, etc. made without departing from the spirit and scope of the present application shall be included in the protection scope of the present application. In addition, the appended claims of the present application are intended to cover all variations and modifications falling within the scope and boundary of the appended claims, or the equivalent forms of such scope and boundary.

Claims

1. A method for producing a magnetoplumbite-type oxide, characterized by, The method comprises the following steps: S1, dissolving rare earth nitrate Ln(NO3)3·6H2O, transition metal nitrate Me(NO3)2 and Al(NO3)3 in deionized water to obtain a mixed nitrate solution; S2, adding citric acid monohydrate to the mixed nitrate solution obtained in step S1, heating and stirring, and evaporating to obtain a transparent gel; S3, drying the gel obtained in step S2 to obtain a loose and porous dry gel; S4, performing first high-temperature treatment on the dry gel obtained in step S3 in an air atmosphere at 650-950 ℃ to obtain a precursor; S5, grinding and crushing the precursor obtained in step S4, uniformly mixing with a salt, and performing second high-temperature treatment in an air atmosphere at 1500-2000 ℃ to obtain a magnetoplumbite-type oxide.

2. The production method according to claim 1, characterized by, In step S1, the molar ratio of the rare earth nitrate Ln(NO3)3·6H2O, the transition metal nitrate Me(NO3)2 and Al(NO3)3 is 1:1:11; and the total concentration of the obtained mixed nitrate solution is 0.01-1 g / L.

3. The preparation method according to claim 1, characterized in that, In step S1, the rare earth nitrate Ln(NO3)3·6H2O is any one of Y(NO3)3·6H2O, La(NO3)3·6H2O, Pr(NO3)3·6H2O, Nd(NO3)3·6H2O, Sm(NO3)3·6H2O, Eu(NO3)3·6H2O, Gd(NO3)3·6H2O, Tm(NO3)3·6H2O, Ce(NO3)3·6H2O and Yb(NO3)3·6H2O; and the transition metal nitrate Me(NO3)2 is any one of Mg(NO3)2, Fe(NO3)2, Co(NO3)2, Ni(NO3)2, Cu(NO3)2, Zr(NO3)2 and Zn(NO3)2.

4. The production method according to claim 1, characterized by, In step S2, the molar amount of citric acid monohydrate is 1-10 times the total molar amount of metal ions in the mixed nitrate solution; The heating and stirring are performed at 65-100 ℃, and the transparent gel is obtained by evaporation.

5. The preparation method according to claim 1, characterized in that, In step S3, the drying condition is that the gel is placed in an oven at 50-200 ℃ for 5-12 h.

6. The method of claim 1, wherein, In step S4, the time for the first high-temperature treatment is 1-5 h.

7. The preparation method according to claim 1, characterized in that, In step S5, the time for the second high-temperature treatment is 1-10 h.

8. The method of claim 1, wherein, In step S5, the salt is a mixture of NaCl and KCl, and the total mass of the salt is 2-20 times the mass of the precursor.

9. A magnetoplumbite-type oxide characterized by, The magnetoplumbite type oxide has a chemical formula of LnMeAl 11 O 19 wherein Ln is any one of rare earth elements Y, La, Pr, Nd, Sm, Eu, Gd, Tm, Ce and Yb, and Me is any one of transition metal elements Mg, Fe, Co, Ni, Cu, Zr and Zn.

10. Use of the magnetoplumbite-type oxide according to claim 9 as a catalyst material in a sulfur reduction reaction.

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