Mesoporous carbon supported sulfur praseodymium oxide catalyst and preparation method thereof

Abstract

The invention discloses a preparation method of a mesoporous carbon-supported sulfur praseodymium oxide catalyst, which comprises the following steps: by taking a triblock copolymer as a template agent, ethanol as a solvent, low-molecular-weight phenolic resin generated by prepolymerization of phenol and formaldehyde as an organic precursor to provide a carbon source, and praseodymium salt hydrate as a metal source, preparing the mesoporous carbon-supported sulfur praseodymium oxide catalyst. Uniformly stirring at a certain temperature to obtain a mixed solution; ethyl alcohol in the mixed solution is volatilized, the carbon source and the metal source are co-assembled with the segmented copolymer through hydrogen bond interaction in the solvent ethyl alcohol volatilization process, a mesostructure containing a metal polymer is formed, and then thermal polymerization is conducted at the high temperature; according to the mesoporous carbon-supported rare earth praseodymium oxide catalyst and the preparation method thereof provided by the invention, the prepared catalyst particles are uniform in dispersion and consistent in particle size, and have good catalytic activity, and the performance of a lithium-sulfur battery can be improved.

Description

Technical Field

[0001] The invention relates to the field of rare earth catalyst synthesis, and in particular to a mesoporous carbon-supported praseodymium oxysulfide catalyst and a preparation method thereof. Background Art

[0002] The development of rare earth functional materials is the key to promoting the development of my country's rare earth industry. Rare earth metal sulfide has important commercial applications in many cutting-edge fields. For example, it is a commonly used radiation enhancement screen, fluorescent display tube luminescent agent, and also has important application value in specific fields such as X-ray computed tomography and local jet impact heat transfer measurement. Since rare earth oxide sulfide is one of the few materials that contain both oxygen-metal bonds and sulfur-metal bonds in its structure, it has thermodynamic stability, oxidation resistance and high sulfur resistance at room temperature, and it is also one of the effective catalysts for hydrodesulfurization reaction. In addition, rare earth sulfide still retains the characteristics of rare earth oxides, and there are a large number of oxygen vacancies in the crystal structure. It has strong oxygen binding ability and catalytic effect, and is widely used as an oxygen adsorption component. At the same time, rare earth oxygen / sulfide also has certain electrochemical activity and has been used as anode materials for lithium-ion batteries and catalysts for the positive electrode of lithium-air batteries. Therefore, the controllable synthesis and structural regulation of rare earth sulfide are of great significance to optoelectronic functional materials, medical diagnosis, precision measurement, energy storage and other fields.

[0003] However, most of the synthetic routes of rare earth oxysulfides are traditional high-temperature solid-phase reactions, and the material structure and particle size are difficult to control, resulting in their application in many fields, especially in the field of catalysis, which has not been widely promoted. Considering the intrinsic properties of the materials, on the one hand, rare earth elements have a strong affinity for oxygen, but a weak affinity for sulfur, and the preparation of rare earth oxysulfides requires a higher reaction temperature; on the other hand, the reaction between rare earth elements and sulfur-containing species is an exothermic process, and the crystallization and unit cell growth process are difficult to precisely control, making it difficult to obtain small-sized and uniformly dispersed rare earth sulfides. Summary of the invention

[0004] In view of the above-mentioned defects of the prior art, the technical problem to be solved by the present invention is that the existing rare earth sulfur oxides are usually high-temperature solid-phase reactions, and the material structure and particle size are difficult to control, which leads to the inability to widely promote them in the field of catalysis, and it is difficult to obtain small-sized and uniformly dispersed rare earth sulfides. The present invention provides a mesoporous carbon-supported praseodymium sulfur oxide catalyst and a preparation method thereof. The prepared catalyst particles are uniformly dispersed, have a consistent particle size, have good catalytic activity, and can improve the performance of lithium-sulfur batteries.

[0005] To achieve the above object, the present invention provides a method for preparing a mesoporous carbon-supported praseodymium oxysulfide catalyst, comprising the following steps:

[0006] The triblock copolymer is used as a template, ethanol is used as a solvent, a low molecular weight phenolic resin produced by prepolymerization of phenol and formaldehyde is used as an organic precursor to provide a carbon source, and praseodymium salt hydrate is used as a metal source, and a mixed solution is obtained by stirring uniformly at a certain temperature;

[0007] The ethanol in the mixed solution is volatilized at a low temperature, and the carbon source and the metal source are co-assembled with the block copolymer through hydrogen bonding during the volatilization of the solvent ethanol to form a mesoscopic structure of the metal polymer, and then thermal polymerization occurs at a high temperature to stabilize the ordered mesoscopic phase of the metal polymer;

[0008] The block copolymer is calcined at low temperature and then carbonized at high temperature to obtain stable mesoporous carbon-supported rare earth praseodymium oxide.

[0009] Under a reducing atmosphere, a sulfur source is added and secondary calcination is performed to obtain a mesoporous carbon-supported rare earth praseodymium oxysulfide catalyst, in which nanoparticles are uniformly dispersed in the mesopore walls;

[0010] Among them, the mesoporous carbon-supported praseodymium oxysulfide catalyst has a highly ordered two-dimensional hexagonal mesostructure.

[0011] Furthermore, the triblock copolymer is F127, and F127 is (HO·(C 2 H 4 O) m ·(C 3 H 6 O) n ·H), the amount of F127 added is 0.8-1.5 g, the amount of ethanol added is 10-50 mL, the amount of PF added is 5-8 g, and the praseodymium salt hydrate is Pr(NO 3 ) 3 6H 2 O, the added amount is 324g.

[0012] Furthermore, the carbon source and the metal source co-assemble with the block copolymer through hydrogen bonding during the evaporation of the solvent ethanol. Specifically, under the induction of ethanol, the carbon source and the metal source assemble into an ordered mesoscopic structure, and then thermal polymerization occurs to stabilize the obtained mesophase. The temperature is raised to 1-5 °C min -1 The ethanol volatilization temperature is controlled at 30-50°C, the ethanol volatilization time is controlled at 8-24h, the thermal polymerization temperature is 80-100°C, and the thermal polymerization time is controlled at 24-48h.

[0013] Furthermore, the block copolymer is calcined at low temperature and then carbonized at high temperature to obtain stable mesoporous carbon-supported rare earth praseodymium oxide, wherein the calcination atmosphere is N 2 , the temperature program is 1~5℃min -1The temperature for removing the block copolymer is 200-400°C and maintained for 2-5 hours, and the temperature for high-temperature carbonization is 600-800°C and maintained for 1-3 hours.

[0014] Further, under a reducing atmosphere, a sulfur source is added and a secondary calcination is performed to obtain a mesoporous carbon-supported rare earth praseodymium oxysulfide catalyst, wherein the nanoparticles are uniformly dispersed in the mesoporous pore walls. Specifically, the reducing atmosphere of the secondary calcination is (5% H 2 )H 2 -Ar mixed gas, the added sulfur source is sulfur powder, the program temperature is 1~5℃min -1 , the temperature is 900-1200℃, and the calcination time is 2-4h.

[0015] Furthermore, F127 is first mixed with ethanol and stirred for 0.5 to 2 hours, and then an ethanol solution containing praseodymium salt is added. After the above liquids are evenly mixed, PF is added dropwise, followed by stirring for 0.5 to 1 hour. The reaction temperature of the above solution is controlled at 30 to 50°C.

[0016] Furthermore, a praseodymium salt precursor solution is prepared, and 324 g of praseodymium salt / 5-10 mL of ethanol solution is prepared, and ultrasonication is performed for 5-30 minutes to mix the solution uniformly.

[0017] Furthermore, the obtained mesoporous-supported mesoporous carbon-supported rare earth praseodymium oxide is mixed with sulfur powder in a mass ratio of 1:1, ground in a mortar for 0.5 to 1 h, and mixed evenly.

[0018] Another preferred embodiment of the present invention provides a mesoporous carbon-supported praseodymium oxysulfide catalyst. The above method can be used to control the particle size of the catalyst to be within 20 nm and the catalyst is evenly dispersed on the mesoporous carbon.

[0019] Another preferred embodiment of the present invention provides a method for preparing a mesoporous carbon-supported praseodymium oxysulfide catalyst, which is suitable for synthesizing other mesoporous carbon-supported rare earth oxysulfides, including mesoporous carbon-supported lanthanum oxysulfide.

[0020] Technical Effects

[0021] The present invention uses mesoporous carbon as a carrier, Pr(NO 3 ) 3 6H 2 O is a praseodymium source to prepare a nano-scale praseodymium oxysulfide catalyst. The metal content of the mesoporous carbon-supported praseodymium oxysulfide catalyst is 15-30wt.%. The mesoporous carbon-supported praseodymium oxysulfide prepared by the present invention has uniformly dispersed particles and uniform particle sizes. The synthesized mesoporous carbon-supported praseodymium oxysulfide catalyst can significantly improve the cycle performance of the battery in the sulfur reduction reaction of the lithium-sulfur battery.

[0022] The present invention discloses a mesoporous carbon-supported praseodymium oxysulfide (Pr 2 O 2S / OMC) catalyst and its preparation method, Pr 2 O 2 The S / OMC catalyst has a praseodymium oxide sulfur content of 10 to 30 wt.% and a particle size of 3 to 10 nm. The present invention utilizes coordination-assisted block copolymer self-assembly technology to synthesize, restricts the growth of praseodymium oxide nanoparticles in the mesoporous structure, synthesizes a stable mesoporous carbon-supported praseodymium oxide catalyst, and then performs secondary high-temperature calcination under the condition of adding a sulfur source to obtain Pr 2 O 2 S / OMC. The catalyst has a highly ordered two-dimensional hexagonal mesoscopic structure, and the nanoparticles are small in size, evenly distributed and have good stability. The preparation method of the invention is simple, the cost is low, the material has high activity, and it has considerable development prospects in the field of functional rare earth material development and industrial catalysis.

[0023] The concept, specific structure and technical effects of the present invention will be further described below in conjunction with the accompanying drawings to fully understand the purpose, characteristics and effects of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 is the XRD pattern of the mesoporous carbon-supported praseodymium oxysulfide catalyst of Example 1 of the present invention;

[0025] Figure 2 is a TEM image of the mesoporous carbon-supported praseodymium oxysulfide catalyst of Example 1 of the present invention;

[0026] Figure 3 This is the XRD diagram of the mesoporous praseodymium oxide catalyst of the sample of Comparative Example 1 of the present invention;

[0027] Figure 4 This is the XRD diagram of the mesoporous praseodymium sulfide catalyst of Comparative Example 2 of the present invention. DETAILED DESCRIPTION

[0028] In order to make the technical problems, technical solutions and beneficial effects to be solved by the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0029] In the following description, specific details such as specific internal procedures and techniques are provided for the purpose of illustration rather than limitation, so as to provide a thorough understanding of the embodiments of the present invention. However, it should be clear to those skilled in the art that the present invention may be implemented in other embodiments without these specific details. In other cases, detailed descriptions of well-known systems, devices, circuits, and methods are omitted to prevent unnecessary details from obstructing the description of the present invention.

[0030] Example 1

[0031] This embodiment provides a method for preparing a mesoporous carbon-supported praseodymium oxysulfide catalyst, the steps of which are as follows:

[0032] (1) Preparation of mesoporous carbon-supported praseodymium oxide: 1.5 g of F127 and 30 mL of ethanol were stirred in a heating mantle at 40 °C for 1 h to obtain solution A. 324 g of Pr(NO 3 ) 3 .6H 2 O and 10 ml ethanol were ultrasonically heated for 15 min to obtain solution B, then solution B was added to solution A and stirred for 30 min, and then 5 g PF was slowly added to the mixed solution, stirred for another 30 min, and then a film was laid on the culture dish. The culture dish was placed in an oven at 1 °C min -1 Raise the temperature to 40°C and maintain for 24 h to evaporate the ethanol, then -1 Heat to 80℃ and keep for 24h for thermal polymerization, then cool to room temperature, scrape the film and put it into quartz boat for calcination. -1 The temperature was raised to 350 °C and maintained for 3 h to remove the block copolymer, and then the temperature was increased at 1 °C min -1 The temperature was raised to 600°C and maintained for 2 hours for carbonization treatment. After cooling to room temperature, the mixture was ground evenly to obtain mesoporous carbon-supported praseodymium oxysulfide.

[0033] (2) Preparation of mesoporous carbon-supported praseodymium oxysulfide catalyst: The obtained mesoporous carbon-supported praseodymium oxysulfide and sulfur powder were ground into a quartz boat at a mass ratio of 1:1, and then heated in a tube furnace at 1°C min -1 The temperature was raised to 900° C. and maintained for 2 h for secondary calcination. After cooling to room temperature, the mesoporous carbon-supported praseodymium oxysulfide catalyst was obtained.

[0034] Figure 1 and Figure 2 They are respectively the XRD pattern and TEM picture of the mesoporous carbon-supported praseodymium oxysulfide sample of Example 1. XRD shows that the mesoporous carbon-supported praseodymium oxysulfide is successfully synthesized, and TEM shows that the praseodymium oxysulfide nanoparticles are evenly distributed, and the particle size of the nanoparticles is 10-20 nm.

[0035] Catalytic performance test: The mesoporous carbon-supported praseodymium sulfur oxide catalyst was used in lithium-sulfur batteries. The prepared button battery had a single-cycle capacity decay rate of only 0.043% after 1000 cycles at a current density of 3C.

[0036] Implementation case 2-6 and comparison sample 1-2:

[0037] The operation of Examples 2-6 is similar to that of Example 1, except that, as shown in Table 1, the factors such as the amount of the drug added, the temperature and time of ethanol volatilization, the temperature and time of thermal polymerization, the temperature of carbonization and the temperature of secondary calcination are changed; the operation of Comparative Samples 1-2 is similar to that of Example 1, except that the conditions of secondary calcination are not added to Comparative Sample 1. 2 The comparative sample 2 is a mesoporous carbon-supported rare earth praseodymium oxide mixed with sulfur powder in a ratio of 1:3 in N 2 The experimental conditions of Examples 2-6 and Comparative Samples 1-2 are shown in Table 1.

[0038] Table 1 Experimental conditions of Examples 1-7

[0039]

[0040]

[0041] As can be seen from the above embodiments, the mesoporous carbon-supported praseodymium oxysulfide catalyst prepared by the preparation method of the mesoporous carbon-supported praseodymium oxysulfide catalyst provided by the present invention has uniform particle distribution and a nanoparticle size of 10 to 20 nm. It has good catalytic performance: the mesoporous carbon-supported praseodymium oxysulfide catalyst is used in lithium-sulfur batteries, and the prepared button battery has a single-cycle attenuation rate of only 0.043% after 1000 cycles at a current density of 3C.

[0042] The preferred specific embodiments of the present invention are described in detail above. It should be understood that a person skilled in the art can make many modifications and changes based on the concept of the present invention without creative work. Therefore, any technical solution that can be obtained by a person skilled in the art through logical analysis, reasoning or limited experiments based on the concept of the present invention on the basis of the prior art should be within the scope of protection determined by the claims.

Claims

1. A method for preparing a mesoporous carbon-supported praseodymium oxysulfide catalyst, characterized in that: The following steps are involved: The triblock copolymer is used as a template, ethanol is used as a solvent, a low molecular weight phenolic resin produced by prepolymerization of phenol and formaldehyde is used as an organic precursor to provide a carbon source, and praseodymium salt hydrate is used as a metal source, and a mixed solution is obtained by stirring uniformly at a certain temperature; The ethanol in the mixed solution is volatilized at a low temperature, and the carbon source and the metal source are co-assembled with the block copolymer through hydrogen bonding during the volatilization of the solvent ethanol to form a mesoscopic structure of the metal polymer, and then thermal polymerization occurs at a high temperature to stabilize the ordered mesoscopic phase of the metal polymer; The block copolymer is calcined at low temperature and then carbonized at high temperature to obtain stable mesoporous carbon-supported rare earth praseodymium oxide. Under a reducing atmosphere, a sulfur source is added and secondary calcination is performed to obtain a mesoporous carbon-supported rare earth praseodymium oxysulfide catalyst, in which nanoparticles are uniformly dispersed in the mesopore walls; The mesoporous carbon-supported praseodymium oxysulfide catalyst has a highly ordered two-dimensional hexagonal mesoscopic structure.

2. The method for preparing a mesoporous carbon-supported praseodymium oxysulfide catalyst according to claim 1, characterized in that: The triblock copolymer is F127, and F127 is (HO·(C2H4O) m ·(C3H6O) n ·H), the added amount of F127 is 0.8-1.5g, the added amount of ethanol is 10-50mL, the added amount of PF is 5-8g, and the praseodymium salt hydrate is Pr(NO3)3·6H2O, and the added amount is 324g.

3. The method for preparing a mesoporous carbon-supported praseodymium oxysulfide catalyst according to claim 1, characterized in that: The carbon source and the metal source co-assemble with the block copolymer through hydrogen bonding during the evaporation of the solvent ethanol. Specifically, under the induction of ethanol, the carbon source and the metal source assemble into an ordered mesoscopic structure, and then thermal polymerization occurs to stabilize the obtained mesophase. The temperature rise program is 1-5℃min -1 The ethanol volatilization temperature is controlled at 30-50°C, the ethanol volatilization time is controlled at 8-24h, the thermal polymerization temperature is 80-100°C, and the thermal polymerization time is controlled at 24-48h.

4. The method for preparing a mesoporous carbon-supported sulfur oxide catalyst according to claim 1, characterized in that: The block copolymer is calcined at low temperature and then carbonized at high temperature to obtain stable mesoporous carbon-supported rare earth praseodymium oxide. The calcination atmosphere is N2 and the temperature is programmed at 1-5 °C min -1 The temperature for removing the block copolymer is 200-400°C and maintained for 2-5 hours, and the temperature for high-temperature carbonization is 600-800°C and maintained for 1-3 hours.

5. The method for preparing a mesoporous carbon-supported praseodymium oxysulfide catalyst according to claim 1, characterized in that: In a reducing atmosphere, a sulfur source is added and secondary calcination is performed to obtain rare earth praseodymium oxysulfide, and the nanoparticles are uniformly dispersed in the mesoporous pore walls. Specifically, the reducing atmosphere of the secondary calcination is a (5% H2) H2-Ar mixed gas, the added sulfur source is sulfur powder, and the program temperature is 1-5°C min -1 , the temperature is 900-1200℃, and the calcination time is 2-4h.

6. The method for preparing a mesoporous carbon-supported praseodymium oxysulfide catalyst according to claim 2, characterized in that: F127 is first mixed with ethanol and stirred for 0.5 to 2 hours, and then an ethanol solution containing praseodymium salt is added. After the above liquids are evenly mixed, PF is added dropwise and then stirred for 0.5 to 1 hour. The reaction temperature of the above solution is controlled at 30 to 50°C.

7. The method for preparing a mesoporous carbon-supported praseodymium oxysulfide catalyst according to claim 6, characterized in that: Prepare a praseodymium salt precursor solution, prepare 324 g praseodymium salt / 5-10 mL ethanol solution, and ultrasonicate for 5-30 minutes to mix the solution evenly.

8. The method for preparing a mesoporous carbon-supported praseodymium oxysulfide catalyst according to claim 5, characterized in that: The obtained mesoporous supported rare earth praseodymium oxide and sulfur powder are mixed in a mass ratio of 1:1, ground in a mortar for 0.5 to 1 hour, and mixed evenly.

9. A mesoporous carbon-supported praseodymium oxysulfide catalyst, characterized in that: The method described in any one of claims 1 to 8 can control the particle size of the catalyst to be within 20 nm and evenly dispersed on the mesoporous carbon.

10. A method for preparing the mesoporous carbon-supported praseodymium oxysulfide catalyst as claimed in any one of claims 1 to 8, which is suitable for synthesizing other mesoporous carbon-supported rare earth oxysulfides, including mesoporous carbon-supported lanthanum oxysulfide.

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