A method for crystal phase regulation of electrocatalytic performance of transition metal-doped molybdenum-based carbides

Abstract

The present invention provides a method for regulating the electrocatalytic performance of a transition metal-doped molybdenum-based carbide by crystal phase, comprising the following steps: (1) subjecting a reaction solution containing transition metal ions, molybdenum ions, and a ligand to a hydrothermal reaction to produce a transition metal-doped molybdenum-based MOF material; and (2) mixing the transition metal-doped molybdenum-based MOF material with dicyandiamide, and then subjecting the mixture to a high-temperature calcination carbonization reaction under a protective atmosphere to produce a transition metal-doped molybdenum-based carbide. The present invention regulates the crystal phase of the transition metal-doped molybdenum-based carbide by varying the mixing ratio of the transition metal-doped molybdenum-based MOF material and dicyandiamide, thereby regulating the electrocatalytic performance of the transition metal-doped molybdenum-based carbide. The electrocatalyst of the transition metal-doped molybdenum-based carbide prepared by this method has a stable structure, controllable and uniformly distributed components, and exhibits excellent electrocatalytic ORR performance.

Description

Technical Field

[0001] The present invention relates to the field of electrocatalysis technology, and in particular to a method for regulating the electrocatalytic performance of transition metal-doped molybdenum-based carbides through crystal phase. Background Art

[0002] Transition metal carbides (TMCs) exhibit excellent catalytic potential due to their high electrical conductivity, wide pH range, good corrosion resistance, high mechanical strength, and excellent stability. Among them, molybdenum carbide (MoC) has been widely studied in the field of electrocatalytic hydrogen production due to its platinum-like electronic structure, low electrical resistance, and good chemical stability.

[0003] As early as 2014, Wan et al. prepared β-Mo2C, γ-MoC, and α-MoC by regulating pyrolysis conditions. 1-x The research team studied four crystalline phases of molybdenum carbide materials, namely β-Mo2C and γ-MoC, and found through XPS characterization that both β-Mo2C and γ-MoC have Pt-like electronic structures and good hydrogen evolution reaction (HER) performance, but their application in oxygen reduction reaction (ORR) has not been mentioned. β-Mo2C, γ-MoC, and η-MoC all belong to the hexagonal crystal system, with space groups of P63 / mmc

[194] , P-6m2

[187] , and P63 / mmc

[194] , respectively. Their stacking orders are different, namely AB, AA, and ABCABC, which also gives them different electron capture abilities and lattice defects.

[0004] Currently, existing processes for preparing multiphase molybdenum carbide are unable to regulate the crystal phase of molybdenum carbide, and most require higher pyrolysis temperatures and longer pyrolysis times, resulting in high energy consumption and a lengthy and complex preparation process, which is not conducive to industrial production and practical applications. Summary of the Invention

[0005] In view of the shortcomings of the prior art described above, the object of the present invention is to provide a method for regulating the electrocatalytic performance of transition metal-doped molybdenum-based carbides by crystal phase, which is used to solve the problems that the existing phase molybdenum carbide preparation process cannot regulate the crystal phase of molybdenum carbide, has high energy consumption, complex process, and is not conducive to industrial production.

[0006] To achieve the above-mentioned and other related purposes, the present invention provides a method for regulating the electrocatalytic performance of transition metal-doped molybdenum-based carbides by crystal phase.

[0007] The method comprises the following steps:

[0008] 1) subjecting a reaction solution containing transition metal ions, molybdenum ions and ligands to a hydrothermal reaction to prepare a transition metal-doped molybdenum-based MOF material;

[0009] 2) After mixing the transition metal-doped molybdenum-based MOF material with dicyandiamide, the mixture is subjected to a high-temperature calcination carbonization reaction under a protective atmosphere to produce a transition metal-doped molybdenum-based carbide; in this step, the transition metal-doped molybdenum-based MOF material itself is carbonized, and the dicyandiamide is pyrolyzed to load carbon into the MOF material in the form of a carbon-containing gas;

[0010] By changing the mixing ratio of transition metal-doped molybdenum-based MOF material and dicyandiamide, the crystal phase of transition metal-doped molybdenum-based carbide is regulated, thereby regulating the electrocatalytic performance of transition metal-doped molybdenum-based carbide; the crystal phase of the transition metal-doped molybdenum-based carbide includes β-Mo2C phase, γ-MoC and η-MoC phase.

[0011] By regulating the carbon content in molybdenum-based carbides, the present invention can obtain molybdenum carbides with various phase components such as β-Mo2C / γ-MoC / η-MoC phases. The transition metal-doped molybdenum-based carbide electrocatalyst prepared by this method has a stable structure, controllable and uniformly distributed components, and exhibits excellent electrocatalytic ORR performance. The entire regulation method is simple, low-cost, and easy to operate, which is conducive to scale-up and effectively promotes the application of molybdenum carbide materials in multiple fields such as photoelectrocatalysis, and has broad industrial application prospects.

[0012] Preferably, in step (1), the solvent of the reaction solution is water.

[0013] Preferably, in step (1), the ligand is selected from one of imidazole and 2-methylimidazole.

[0014] Preferably, in step (1), the transition metal ion is selected from Cu 2+ , Fe 3+ , Mg 2+ , Al 3+ , Mn 2+ 、Co 2+ and Ni + More preferably, the transition metal ion is added to the system in the form of a water-soluble salt, such as Co(NO3)2·6H2O and Ni(NO3)2·6H2O and other nitrates.

[0015] Preferably, in step (1), based on the total volume of the reaction solution, the concentration of the ligand is 0.1-0.2 mol / L, the concentration of the transition metal ion is 0.01-0.02 mol / L; and the concentration of the molybdenum ion is 0.05-0.1 mol / L.

[0016] Preferably, the molar ratio of the transition metal ion to the platinum ion is (0.2-0.5):1, such as (0.2-0.3):1, (0.3-0.4):

[0017] 1, (0.4~0.5):1.

[0018] Preferably, in step (1), the temperature of the hydrothermal reaction is 80-180°C, such as 80-100°C, 100-120°C, 120-140°C, 140-160°C, 160-180°C, and the time of the hydrothermal reaction is 4-24h.

[0019] Preferably, in step (2), the high-temperature calcination carbonization reaction adopts staged calcination: the calcination temperature of the first stage is 300-500°C, and the calcination time is 0.5-1h; the calcination temperature of the second stage is 700-1000°C, and the calcination time is 1-2h.

[0020] In the above technical solution, low-temperature calcination is used in the first stage. At this time, the transition metal-doped molybdenum-based MOF material itself will undergo carbonization, which is conducive to maintaining the uniform distribution of transition metal particles; after the dicyandiamide is melted, it generates intense heat to generate melamine, melamine and other substances; in the second stage, the decomposition products of dicyandiamide further decompose at high temperature to form high-concentration carbon-containing gas, which enters the gaps in the MOF after preliminary carbonization.

[0021] Preferably, the heating rates of the first stage and the second stage are 10-20°C / min, such as 10-15°C / min, 15-20°C / min.

[0022] The high-temperature calcination and carbonization reactions in the two stages of the present application both adopt a relatively fast heating rate and rapid carbonization, which is conducive to the rapid formation of high-concentration carbon-containing gas to achieve the carbonization goal.

[0023] Preferably, in step (2), the mass ratio of the transition metal-doped molybdenum-based MOF material to dicyandiamide is 1:(0-25).

[0024] Preferably, when the mass ratio of transition metal-doped molybdenum-based MOF material to dicyandiamide is 1:(0-5), the crystal phase of the transition metal-doped molybdenum-based carbide is β-Mo2C phase; when the mass ratio of transition metal-doped molybdenum-based MOF material to dicyandiamide is 1:(15-25), the crystal phase of the transition metal-doped molybdenum-based carbide is γ-MoC phase; when the mass ratio of transition metal-doped molybdenum-based MOF material to dicyandiamide is 1:

[0025] (6-14), the crystalline phase of the transition metal-doped molybdenum-based carbide is an η-MoC phase.

[0026] Preferably, in step (1), washing, filtering and drying steps are further performed after the hydrothermal reaction.

[0027] Preferably, the drying is performed by vacuum drying, the vacuum drying temperature is 60 to 80° C., and the vacuum degree is -3000 to -2000 kPa.

[0028] As described above, the method of the present invention for regulating the electrocatalytic performance of transition metal-doped molybdenum-based carbides by crystal phase has the following beneficial effects: by regulating the carbon content in the molybdenum-based carbide, molybdenum carbide with a variety of different phase components such as β-Mo2C / γ-MoC / η-MoC phases can be obtained, and the electrocatalyst of transition metal-doped molybdenum-based carbides prepared by this method has a stable structure, controllable and uniform distribution of components, and exhibits excellent electrocatalytic ORR performance; the entire regulation method is simple, low-cost, and easy to operate, which is conducive to scale-up, effectively promoting the application of molybdenum carbide materials in multiple fields such as photoelectrocatalysis, and has broad industrial application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 is a SEM image of the Co / Mo MOF prepared in Example 1.

[0030] Figure 2 is the XRD spectrum of the Co / Mo MOF prepared in Example 1.

[0031] Figure 3 It is an XRD comparison diagram of the molybdenum carbide nanomaterial (a) with β-Mo2C phase, the molybdenum carbide nanomaterial (b) with β-Mo2C / η-MoC phase, the molybdenum carbide nanomaterial (c) with η-MoC phase and the molybdenum carbide nanomaterial (d) with γ-MoC / η-MoC phase prepared in Examples 1-4, respectively.

[0032] Figure 4 The Co / Mo prepared in Example 1-4 x Electrocatalytic ORR performance of C. DETAILED DESCRIPTION

[0033] The following describes the embodiments of the present invention through specific examples. Those skilled in the art will readily understand the other advantages and benefits of the present invention from the disclosure herein. The present invention may also be implemented or applied through various other specific embodiments, and the details in this specification may be modified or altered based on different viewpoints and applications without departing from the spirit of the present invention.

[0034] It should be noted that the process equipment or devices not specifically specified in the following embodiments are all conventional equipment or devices in the art.

[0035] Furthermore, it should be understood that the one or more method steps mentioned in the present invention do not exclude the presence of other method steps before or after the combination step, or the insertion of other method steps between these explicitly mentioned steps, unless otherwise specified. It should also be understood that the combination connection relationship between one or more devices / apparatuses mentioned in the present invention does not exclude the presence of other devices / apparatuses before or after the combination device / apparatus, or the insertion of other devices / apparatuses between two explicitly mentioned devices / apparatuses, unless otherwise specified. Furthermore, unless otherwise specified, the numbering of each method step is merely a convenient tool for identifying each method step, and is not intended to limit the order of arrangement of each method step or to define the scope of the present invention. Changes or adjustments to their relative relationships, without substantially changing the technical content, should also be considered within the scope of the present invention.

[0036] Example 1

[0037] (1) Weigh 0.465g MoO3 and 0.553g imidazole and pour them into 25ml deionized water, which is called solution a. Weigh 0.233g cobalt nitrate hexahydrate and pour it into 25ml deionized water, which is called solution b. After ultrasonic homogenization, solutions a and b are poured into a hydrothermal reactor and reacted at 120℃ for 8h. After the reaction stops, the temperature is naturally cooled to room temperature. The obtained product is centrifuged and washed with deionized water three times; and vacuum dried at 60℃ for 12h with a vacuum degree of -3000kPa to obtain Co / Mo MOF crystal powder.

[0038] (2) Take an appropriate amount of Co / Mo MOF and place it in a boat-shaped crucible. Take a certain amount of dicyandiamide and MOF powder and stir them evenly. The mass ratio of MOF powder to dicyandiamide is 1:1. Place the crucible in the middle of a quartz tube and react at 500℃ for 1h in a tube furnace under nitrogen atmosphere. Then heat it to 700℃ and carbonize it for 2h at a heating rate of 10℃ / min to obtain Co / Mo x C powder;

[0039] The SEM and XRD patterns of the Co / Mo MOF prepared in this example are shown in Figure 2. Figure 1 and Figure 2 The XRD diffraction pattern of the obtained transition metal doped molybdenum-based carbide material is shown as Figure 3 As shown in a, the diffraction peaks at 2θ angles of 34.354°, 37.978°, 39.392°, 52.122°, 61.527°, 69.565°, 72.384°, 74.645°, and 75.513° correspond to the (100), (002), (101), (102), (110), (103), (200), (112), and (201) crystal planes of β-Mo2C, respectively, indicating that the method of the present invention can synthesize β-Mo2C. Its ORR performance is shown in FIG. Figure 4As shown, the starting potential is 0.86V and the half-wave potential is 0.74V, which is the worst performance compared with other phases.

[0040] Example 2

[0041] (1) Weigh 0.465g MoO3 and 0.553g imidazole and pour them into 25ml deionized water, which is called solution a. Weigh 0.233g cobalt nitrate hexahydrate and pour it into 25ml deionized water, which is called solution b. After ultrasonic homogenization, solutions a and b are poured into a hydrothermal reactor and reacted at 120℃ for 8h. After the reaction stops, the temperature is naturally cooled to room temperature. The obtained product is centrifuged and washed with deionized water three times; and vacuum dried at 60℃ for 12h with a vacuum degree of -3000kPa to obtain Co / Mo MOF crystal powder.

[0042] (2) Take an appropriate amount of Co / Mo MOF and place it in a boat-shaped crucible. Take a certain amount of dicyandiamide and MOF powder and stir them evenly. The mass ratio of MOF powder to dicyandiamide is 1:5. Place the crucible in the middle of a quartz tube and react at 500℃ for 1h in a tube furnace under nitrogen atmosphere. Then heat it to 700℃ and carbonize it for 2h at a heating rate of 10℃ / min to obtain Co / Mo x C powder;

[0043] The XRD diffraction pattern of the transition metal doped molybdenum-based carbide material prepared in this embodiment is as follows: Figure 3 As shown in b, the spectrum shows diffraction peaks at 2θ angles of 34.354°, 37.978°, 39.392°, 52.122°, 61.527°, 69.565°, 72.384°, 74.645°, and 75.513°, which correspond to the (100), (002), (101), (102), (110), (103), (200), (112), and (201) crystal planes of β-Mo2C, and diffraction peaks at 2θ angles of 36.774°, 39.276°, 42.569°, and 61.524°, which correspond to the (006), (103), (104), and (110) crystal planes of η-MoC. This shows that the method of the present invention can synthesize mixed-phase molybdenum carbide of β-Mo2C / η-MoC. Its ORR performance is shown in FIG. Figure 4 As shown, the starting potential is 0.9V and the half-wave potential is 0.82V, which means the performance is good.

[0044] Example 3

[0045] (1) Weigh 0.465g MoO3 and 0.553g imidazole and pour them into 25ml deionized water, which is called solution a. Weigh 0.233g cobalt nitrate hexahydrate and pour it into 25ml deionized water, which is called solution b. After ultrasonic homogenization, solutions a and b are poured into a hydrothermal reactor and reacted at 120℃ for 8h. After the reaction stops, the temperature is naturally cooled to room temperature. The obtained product is centrifuged and washed with deionized water three times; and vacuum dried at 60℃ for 12h with a vacuum degree of -3000kPa to obtain Co / Mo MOF crystal powder.

[0046] (2) Take an appropriate amount of Co / Mo MOF and place it in a boat-shaped crucible. Take a certain amount of dicyandiamide and MOF powder and stir them evenly. The mass ratio of MOF powder to dicyandiamide is 1:10. Place the crucible in the middle of a quartz tube and react at 500℃ for 1h in a tube furnace under nitrogen atmosphere. Then heat it to 700℃ and carbonize it for 2h at a heating rate of 10℃ / min to obtain Co / Mo x C powder;

[0047] The XRD diffraction pattern of the transition metal doped molybdenum-based carbide material prepared in this embodiment is as follows: Figure 3 As shown in b, the diffraction peaks at 2θ angles of 36.774°, 39.276°, 42.569°, and 61.524° correspond to the (006), (103), (104), and (110) crystal planes of η-MoC, respectively. This shows that the method of the present invention can synthesize η-MoC. Its ORR performance is as follows Figure 4 As shown, the starting potential is 0.93V, the half-wave potential is 0.84V, and the performance is the best.

[0048] Example 4

[0049] (1) Weigh 0.465g MoO3 and 0.553g imidazole and pour them into 25ml deionized water, which is called solution a. Weigh 0.233g cobalt nitrate hexahydrate and pour it into 25ml deionized water, which is called solution b. After ultrasonic homogenization, solutions a and b are poured into a hydrothermal reactor and reacted at 120℃ for 8h. After the reaction stops, the temperature is naturally cooled to room temperature. The obtained product is centrifuged and washed with deionized water three times; and vacuum dried at 60℃ for 12h with a vacuum degree of -3000kPa to obtain Co / Mo MOF crystal powder.

[0050] (2) Take an appropriate amount of Co / Mo MOF and place it in a boat-shaped crucible. Take a certain amount of dicyandiamide and MOF powder and stir them evenly. The mass ratio of MOF powder to dicyandiamide is 1:25. Place the crucible in the middle of a quartz tube and react at 500℃ for 1h in a tube furnace under nitrogen atmosphere. Then heat it to 700℃ and carbonize it for 2h at a heating rate of 10℃ / min to obtain Co / Mo x C powder;

[0051] The XRD diffraction pattern of the transition metal doped molybdenum-based carbide material prepared in this embodiment is as follows: Figure 3 As shown in b, the diffraction peaks at 2θ angles of 36.774°, 39.276°, 42.569°, and 61.524° correspond to the (006), (103), (104), and (110) crystal planes of η-MoC, respectively. The diffraction peaks at 2θ angles of 32.113, 35.743, 48.789, and 64.177 correspond to the (001), (100), (101), and (110) crystal planes of γ-MoC, respectively. This shows that the method of the present invention can synthesize mixed phase molybdenum carbide of η-MoC / γ-MoC. Its ORR performance is shown in FIG. Figure 4 As shown, the starting potential is 0.9V and the half-wave potential is 0.82V, which means the performance is good.

[0052] Example 5

[0053] The difference between Example 5 and Example 1 is that the type of transition metal ions doped is different, Cu 2+ , the specific steps are as follows:

[0054] (1) Weigh 0.72g MoO3 and 0.68g imidazole and pour them into 25ml deionized water, which is called solution a; weigh 0.241g copper nitrate pentahydrate and pour it into 25ml deionized water, which is called solution b. After ultrasonic homogenization, solutions a and b are poured into a hydrothermal reactor and reacted at 140℃ for 6h. After the reaction stops, the temperature is naturally cooled to room temperature. The obtained product is centrifuged and washed with deionized water, and the process is repeated three times. The product is then vacuum dried at 60℃ for 12h with a vacuum degree of -2000kPa to obtain Cu / Mo MOF crystal powder.

[0055] (2) Take an appropriate amount of Cu / Mo MOF and place it in a boat-shaped crucible. Take a certain amount of dicyandiamide and MOF powder and stir them evenly. The mass ratio of MOF powder to dicyandiamide is 1:20. Place the crucible in the middle of a quartz tube and react at 350℃ for 1h in a tube furnace under nitrogen atmosphere. Then heat it to 900℃ and carbonize it for 2h at a heating rate of 15℃ / min to obtain Cu / Mo. x C powder.

[0056] The ORR performance results of the transition metal-doped molybdenum-based carbide material prepared in this embodiment are: an onset potential of 0.89V and a half-wave potential of 0.81V.

[0057] Example 6

[0058] The difference between Example 6 and Example 1 is that the doped transition metal ions are different in type, namely Mn 2+ , the specific steps are as follows:

[0059] (1) Weigh 0.36g MoO3 and 0.34g imidazole and pour them into 25ml deionized water, which is called solution a; weigh 0.314g manganese nitrate tetrahydrate and pour it into 25ml deionized water, which is called solution b. After ultrasonic homogenization, solutions a and b are poured into a hydrothermal reactor and reacted at 160℃ for 4h. After the reaction stops, the temperature is naturally cooled to room temperature. The obtained product is centrifuged and washed with deionized water three times; and vacuum dried at 60℃ for 12h with a vacuum degree of -2500kPa to obtain Mn / Mo MOF crystal powder;

[0060] (2) Take an appropriate amount of Mn / Mo MOF and place it in a boat-shaped crucible. Take a certain amount of dicyandiamide and MOF powder and stir them evenly. The mass ratio of MOF powder to dicyandiamide is 1:2. Place the crucible in the middle of a quartz tube and react at 350℃ for 0.5h in a tube furnace under nitrogen atmosphere. Then heat it to 800℃ and carbonize it for 1h. The heating rate is 20℃ / min. Mn / Mo is obtained. x C powder.

[0061] The ORR performance results of the transition metal-doped molybdenum-based carbide material prepared in this embodiment are: an onset potential of 0.84V and a half-wave potential of 0.71V.

[0062] Example 7

[0063] The difference between Example 7 and Example 1 is that in step (2), dicyandiamide is not added, and the rest of the processes are exactly the same.

[0064] The ORR performance results of the transition metal doped molybdenum-based carbide material prepared in this embodiment are as follows: the onset potential is 0.82V, the half-wave potential is 0.68V, and the Mo 3+ Often seen as Mo x C material ORR active sites, and the test shows that Mo in M / β-Mo2C 3+ The proportion of samples is lower than that of other crystal phases, which directly leads to poor sample performance.

[0065] The above description is only a preferred embodiment of the present invention and does not limit the present invention in any form or substance. It should be pointed out that ordinary technicians in this technical field can make several improvements and supplements without departing from the method of the present invention. These improvements and supplements should also be regarded as the scope of protection of the present invention. Any equivalent changes, modifications and evolutions made by technicians familiar with this profession without departing from the spirit and scope of the present invention by using the technical content disclosed above are all equivalent embodiments of the present invention; at the same time, any equivalent changes, modifications and evolutions made to the above embodiments based on the essential technology of the present invention are still within the scope of the technical solution of the present invention.

Claims

1. A method for regulating the electrocatalytic performance of transition metal-doped molybdenum-based carbides by crystal phase, characterized in that: The following steps are involved: (1) subjecting a reaction solution containing transition metal ions, molybdenum ions and ligands to a hydrothermal reaction to prepare a transition metal-doped molybdenum-based MOF material; (2) After the transition metal-doped molybdenum-based MOF material is mixed with dicyandiamide, a high-temperature calcination carbonization reaction is carried out under a protective atmosphere to obtain a transition metal-doped molybdenum-based carbide; the high-temperature calcination carbonization reaction adopts a staged calcination: the calcination temperature of the first stage is 300~500℃, and the calcination time is 0.5~1h; the calcination temperature of the second stage is 700~1000℃, and the calcination time is 1~2h; the heating rate of the first and second stages is 10~20℃ / min; By changing the mixing ratio of transition metal-doped molybdenum-based MOF material and dicyandiamide, the crystal phase of transition metal-doped molybdenum-based carbide is regulated, thereby regulating the electrocatalytic performance of transition metal-doped molybdenum-based carbide; the crystal phase of the transition metal-doped molybdenum-based carbide includes β-Mo2C phase, γ-MoC and η-MoC phase.

2. The method according to claim 1, wherein: In step (1), the solvent of the reaction solution is water, and the transition metal ion is selected from Cu 2+ , Fe 3+ , Mg 2+ , Al 3+ , Mn 2+ 、Co 2+ and Ni + The ligand is selected from one of imidazole and 2-methylimidazole.

3. The method according to claim 2, wherein: In step (1), based on the total volume of the reaction solution, the concentration of the ligand is 0.1-0.2 mol / L, the concentration of the transition metal ion is 0.01-0.02 mol / L; the concentration of the molybdenum ion is 0.05-0.1 mol / L; and the molar ratio of the transition metal ion to the molybdenum ion is (0.2-0.5):

1.

4. The method according to claim 1, wherein: In step (1), the temperature of the hydrothermal reaction is 80-180° C., and the time of the hydrothermal reaction is 4-24 h.

5. The method according to claim 1, wherein: In step (2), the mass ratio of the transition metal-doped molybdenum-based MOF material to dicyandiamide is 1:(1-25).

6. The method according to claim 1, wherein: When the mass ratio of transition metal-doped molybdenum-based MOF material to dicyandiamide is 1:(1-5), the crystal phase of the transition metal-doped molybdenum-based carbide is β-Mo2C phase; When the mass ratio of transition metal-doped molybdenum-based MOF material to dicyandiamide is 1:(15-25), the crystal phase of the transition metal-doped molybdenum-based carbide is γ-MoC phase; When the mass ratio of transition metal-doped molybdenum-based MOF material to dicyandiamide is 1:(6~14), the crystal phase of the transition metal-doped molybdenum-based carbide is η-MoC phase.

7. The method according to claim 1, wherein: In step (1), the hydrothermal reaction is followed by washing, filtering, and drying steps.

8. The method according to claim 6, wherein: The drying is carried out by vacuum drying, the vacuum drying temperature is 60~80℃, and the vacuum degree is -3000~-2000kPa.

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