CN114243036B - Porous aza-carbon nanofiber oxygen reduction catalyst and preparation method thereof - Google Patents
Porous aza-carbon nanofiber oxygen reduction catalyst and preparation method thereof Download PDFInfo
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- 239000003054 catalyst Substances 0.000 title claims abstract description 26
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 title claims abstract description 24
- 239000001301 oxygen Substances 0.000 title claims abstract description 24
- 229910052760 oxygen Inorganic materials 0.000 title claims abstract description 24
- 238000002360 preparation method Methods 0.000 title claims abstract description 23
- 230000009467 reduction Effects 0.000 title claims abstract description 12
- 239000002134 carbon nanofiber Substances 0.000 title claims abstract description 11
- 238000000034 method Methods 0.000 claims abstract description 53
- 239000002121 nanofiber Substances 0.000 claims abstract description 48
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 claims abstract description 32
- 239000013078 crystal Substances 0.000 claims abstract description 24
- 238000009987 spinning Methods 0.000 claims abstract description 23
- 239000002904 solvent Substances 0.000 claims abstract description 21
- 238000010438 heat treatment Methods 0.000 claims abstract description 20
- 230000008569 process Effects 0.000 claims abstract description 20
- 238000003763 carbonization Methods 0.000 claims abstract description 19
- 229910052757 nitrogen Inorganic materials 0.000 claims abstract description 17
- 238000005229 chemical vapour deposition Methods 0.000 claims abstract description 16
- 238000010041 electrostatic spinning Methods 0.000 claims abstract description 14
- 239000012452 mother liquor Substances 0.000 claims abstract description 13
- 239000011943 nanocatalyst Substances 0.000 claims abstract description 13
- 238000011065 in-situ storage Methods 0.000 claims abstract description 12
- 238000006243 chemical reaction Methods 0.000 claims abstract description 11
- 239000012528 membrane Substances 0.000 claims abstract description 11
- ZMXDDKWLCZADIW-UHFFFAOYSA-N N,N-dimethylformamide Substances CN(C)C=O ZMXDDKWLCZADIW-UHFFFAOYSA-N 0.000 claims description 46
- 238000004321 preservation Methods 0.000 claims description 27
- CSCPPACGZOOCGX-UHFFFAOYSA-N Acetone Chemical compound CC(C)=O CSCPPACGZOOCGX-UHFFFAOYSA-N 0.000 claims description 14
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 claims description 14
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Chemical group O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 13
- LXBGSDVWAMZHDD-UHFFFAOYSA-N 2-methyl-1h-imidazole Chemical compound CC1=NC=CN1 LXBGSDVWAMZHDD-UHFFFAOYSA-N 0.000 claims description 11
- 229940011182 cobalt acetate Drugs 0.000 claims description 11
- QAHREYKOYSIQPH-UHFFFAOYSA-L cobalt(II) acetate Chemical compound [Co+2].CC([O-])=O.CC([O-])=O QAHREYKOYSIQPH-UHFFFAOYSA-L 0.000 claims description 11
- 239000000523 sample Substances 0.000 claims description 9
- 239000008367 deionised water Substances 0.000 claims description 7
- 229910021641 deionized water Inorganic materials 0.000 claims description 7
- 229910001868 water Inorganic materials 0.000 claims description 6
- 150000001868 cobalt Chemical class 0.000 claims description 2
- 238000010000 carbonizing Methods 0.000 claims 1
- 238000004519 manufacturing process Methods 0.000 claims 1
- 239000000463 material Substances 0.000 abstract description 6
- 230000003197 catalytic effect Effects 0.000 abstract description 4
- 239000002245 particle Substances 0.000 abstract description 3
- 239000002086 nanomaterial Substances 0.000 abstract description 2
- 238000005580 one pot reaction Methods 0.000 abstract 1
- 229920002239 polyacrylonitrile Polymers 0.000 description 65
- 239000000835 fiber Substances 0.000 description 18
- OKKJLVBELUTLKV-UHFFFAOYSA-N Methanol Chemical compound OC OKKJLVBELUTLKV-UHFFFAOYSA-N 0.000 description 12
- 238000006722 reduction reaction Methods 0.000 description 8
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 6
- 229910052799 carbon Inorganic materials 0.000 description 6
- 238000003756 stirring Methods 0.000 description 6
- 230000002194 synthesizing effect Effects 0.000 description 6
- 239000003575 carbonaceous material Substances 0.000 description 5
- 239000011521 glass Substances 0.000 description 5
- 239000012621 metal-organic framework Substances 0.000 description 5
- 239000000203 mixture Substances 0.000 description 5
- 239000000446 fuel Substances 0.000 description 4
- 239000012535 impurity Substances 0.000 description 4
- 229910052751 metal Inorganic materials 0.000 description 4
- 239000002184 metal Substances 0.000 description 4
- 229910000510 noble metal Inorganic materials 0.000 description 4
- 239000011148 porous material Substances 0.000 description 4
- 230000009286 beneficial effect Effects 0.000 description 3
- 239000001257 hydrogen Substances 0.000 description 3
- 229910052739 hydrogen Inorganic materials 0.000 description 3
- 239000007788 liquid Substances 0.000 description 3
- 238000010907 mechanical stirring Methods 0.000 description 3
- 239000013110 organic ligand Substances 0.000 description 3
- 239000003960 organic solvent Substances 0.000 description 3
- 239000002243 precursor Substances 0.000 description 3
- 238000001878 scanning electron micrograph Methods 0.000 description 3
- 238000001308 synthesis method Methods 0.000 description 3
- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 description 2
- 238000001354 calcination Methods 0.000 description 2
- 238000002425 crystallisation Methods 0.000 description 2
- 230000005684 electric field Effects 0.000 description 2
- 239000003446 ligand Substances 0.000 description 2
- 230000035484 reaction time Effects 0.000 description 2
- 238000011084 recovery Methods 0.000 description 2
- 238000001179 sorption measurement Methods 0.000 description 2
- 229910052723 transition metal Inorganic materials 0.000 description 2
- -1 transition metal salt Chemical class 0.000 description 2
- 239000013153 zeolitic imidazolate framework Substances 0.000 description 2
- 229910021536 Zeolite Inorganic materials 0.000 description 1
- 230000009471 action Effects 0.000 description 1
- 230000004888 barrier function Effects 0.000 description 1
- 239000011324 bead Substances 0.000 description 1
- 230000005540 biological transmission Effects 0.000 description 1
- 239000006227 byproduct Substances 0.000 description 1
- 238000003776 cleavage reaction Methods 0.000 description 1
- 239000003245 coal Substances 0.000 description 1
- UFMZWBIQTDUYBN-UHFFFAOYSA-N cobalt dinitrate Chemical compound [Co+2].[O-][N+]([O-])=O.[O-][N+]([O-])=O UFMZWBIQTDUYBN-UHFFFAOYSA-N 0.000 description 1
- 229910001981 cobalt nitrate Inorganic materials 0.000 description 1
- 239000002131 composite material Substances 0.000 description 1
- 238000005260 corrosion Methods 0.000 description 1
- 230000007797 corrosion Effects 0.000 description 1
- 230000008025 crystallization Effects 0.000 description 1
- 238000003795 desorption Methods 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- 238000009792 diffusion process Methods 0.000 description 1
- HNPSIPDUKPIQMN-UHFFFAOYSA-N dioxosilane;oxo(oxoalumanyloxy)alumane Chemical compound O=[Si]=O.O=[Al]O[Al]=O HNPSIPDUKPIQMN-UHFFFAOYSA-N 0.000 description 1
- 239000006185 dispersion Substances 0.000 description 1
- 238000009826 distribution Methods 0.000 description 1
- 238000005868 electrolysis reaction Methods 0.000 description 1
- 230000007613 environmental effect Effects 0.000 description 1
- 238000003912 environmental pollution Methods 0.000 description 1
- 239000002803 fossil fuel Substances 0.000 description 1
- 150000002431 hydrogen Chemical class 0.000 description 1
- JBFYUZGYRGXSFL-UHFFFAOYSA-N imidazolide Chemical compound C1=C[N-]C=N1 JBFYUZGYRGXSFL-UHFFFAOYSA-N 0.000 description 1
- 150000002500 ions Chemical class 0.000 description 1
- 239000007791 liquid phase Substances 0.000 description 1
- 239000002082 metal nanoparticle Substances 0.000 description 1
- 150000002739 metals Chemical class 0.000 description 1
- VNWKTOKETHGBQD-UHFFFAOYSA-N methane Chemical compound C VNWKTOKETHGBQD-UHFFFAOYSA-N 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 239000000178 monomer Substances 0.000 description 1
- 229910052763 palladium Inorganic materials 0.000 description 1
- 230000000737 periodic effect Effects 0.000 description 1
- 239000003208 petroleum Substances 0.000 description 1
- 239000010970 precious metal Substances 0.000 description 1
- 238000001556 precipitation Methods 0.000 description 1
- 239000000047 product Substances 0.000 description 1
- 230000000630 rising effect Effects 0.000 description 1
- 150000003839 salts Chemical class 0.000 description 1
- 230000007017 scission Effects 0.000 description 1
- 238000002791 soaking Methods 0.000 description 1
- 238000007711 solidification Methods 0.000 description 1
- 230000008023 solidification Effects 0.000 description 1
- 238000004729 solvothermal method Methods 0.000 description 1
- 239000000758 substrate Substances 0.000 description 1
- 239000010457 zeolite Substances 0.000 description 1
- 239000013154 zeolitic imidazolate framework-8 Substances 0.000 description 1
- MFLKDEMTKSVIBK-UHFFFAOYSA-N zinc;2-methylimidazol-3-ide Chemical compound [Zn+2].CC1=NC=C[N-]1.CC1=NC=C[N-]1 MFLKDEMTKSVIBK-UHFFFAOYSA-N 0.000 description 1
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- H01M4/00—Electrodes
- H01M4/86—Inert electrodes with catalytic activity, e.g. for fuel cells
- H01M4/90—Selection of catalytic material
- H01M4/9041—Metals or alloys
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- B22—CASTING; POWDER METALLURGY
- B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
- B22F9/00—Making metallic powder or suspensions thereof
- B22F9/16—Making metallic powder or suspensions thereof using chemical processes
- B22F9/18—Making metallic powder or suspensions thereof using chemical processes with reduction of metal compounds
- B22F9/20—Making metallic powder or suspensions thereof using chemical processes with reduction of metal compounds starting from solid metal compounds
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B82—NANOTECHNOLOGY
- B82Y—SPECIFIC USES OR APPLICATIONS OF NANOSTRUCTURES; MEASUREMENT OR ANALYSIS OF NANOSTRUCTURES; MANUFACTURE OR TREATMENT OF NANOSTRUCTURES
- B82Y30/00—Nanotechnology for materials or surface science, e.g. nanocomposites
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- B82Y40/00—Manufacture or treatment of nanostructures
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- D—TEXTILES; PAPER
- D04—BRAIDING; LACE-MAKING; KNITTING; TRIMMINGS; NON-WOVEN FABRICS
- D04H—MAKING TEXTILE FABRICS, e.g. FROM FIBRES OR FILAMENTARY MATERIAL; FABRICS MADE BY SUCH PROCESSES OR APPARATUS, e.g. FELTS, NON-WOVEN FABRICS; COTTON-WOOL; WADDING ; NON-WOVEN FABRICS FROM STAPLE FIBRES, FILAMENTS OR YARNS, BONDED WITH AT LEAST ONE WEB-LIKE MATERIAL DURING THEIR CONSOLIDATION
- D04H1/00—Non-woven fabrics formed wholly or mainly of staple fibres or like relatively short fibres
- D04H1/70—Non-woven fabrics formed wholly or mainly of staple fibres or like relatively short fibres characterised by the method of forming fleeces or layers, e.g. reorientation of fibres
- D04H1/72—Non-woven fabrics formed wholly or mainly of staple fibres or like relatively short fibres characterised by the method of forming fleeces or layers, e.g. reorientation of fibres the fibres being randomly arranged
- D04H1/728—Non-woven fabrics formed wholly or mainly of staple fibres or like relatively short fibres characterised by the method of forming fleeces or layers, e.g. reorientation of fibres the fibres being randomly arranged by electro-spinning
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- H01M4/00—Electrodes
- H01M4/86—Inert electrodes with catalytic activity, e.g. for fuel cells
- H01M4/90—Selection of catalytic material
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- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
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Abstract
The invention relates to the technical field of catalytic material and nano material preparation, and discloses a porous aza-carbon nanofiber oxygen reduction catalyst and a preparation method thereof, wherein ZIF-67 is prepared by adopting a chemical vapor deposition method, and then a Co-NC nano catalyst is obtained after high-temperature carbonization; the method mainly comprises the following steps: 1) Preparing PAN/DMF mother liquor; 2) Preparing Co 2+/PAN spinning solution; 3) Preparing Co 2+/PAN nanofiber by adopting an electrostatic spinning method; 4) In-situ growing ZIF-67 crystals on the surface of the Co 2+/PAN nanofiber by adopting a Chemical Vapor Deposition (CVD) method; 5) And (3) placing the ZIF-67/PAN nanofiber membrane in a tube furnace, introducing nitrogen for protection in the whole process, heating for carbonization, and preserving heat for a certain time to obtain the Co-NC nano catalyst. The method has mild reaction conditions, does not need solvents in the crystal growth process, is environment-friendly, can be synthesized in one pot from crystal growth to subsequent carbonization, and has uniform prepared Co-NC nano catalyst particles.
Description
Technical Field
The invention relates to the technical field of catalytic material and nano material preparation, in particular to a porous aza carbon nanofiber oxygen reduction catalyst and a preparation method thereof.
Background
Currently, excessive exploitation and consumption of fossil fuels such as coal and petroleum have raised serious energy crisis and environmental pollution problems, and thus efforts have been made to explore various clean energy sources such as wind energy, tidal energy, hydrogen energy, etc. In recent years, fuel cells have received increasing attention from researchers due to their extremely high energy conversion efficiency and power density; in addition, the fuel and the product of the energy conversion equipment are hydrogen, oxygen and water, and the water can prepare the hydrogen and the oxygen through electrolysis, so that the whole process has cycle reversibility and has no pollution to the environment. However, since the cathode Oxygen Reduction Reaction (ORR) process of the fuel cell is complicated, and involves adsorption and transmission of oxygen, cleavage of o=o bond, desorption and output of byproducts, etc., the kinetic process is slow, and a large energy barrier needs to be overcome. At present, precious metals such as Pd, pt and the like and composite catalysts thereof are mainly applied to ORR reaction, but the large-scale application of the catalyst is limited due to high cost, lack of earth reserves, poor stability and the like. Therefore, it is significant to explore non-noble metal catalysts to reduce the amount of noble metal used and even replace noble metal catalysts; at the same time, it is also important to design and study a highly efficient ORR catalyst with a specific structure.
The porous carbon material has good conductivity, high specific surface area and strong corrosion resistance, and is certainly an excellent carrier of a non-noble metal catalyst. Among the numerous porous carbon materials, metal Organic Frameworks (MOFs) have attracted considerable attention from researchers as a precursor derivative of porous carbon materials. MOFs are crystalline porous materials with periodic structures coordinated by metals or metal clusters and organic ligands. As a precursor of a porous carbon material applied to an electrocatalytic ORR reaction, MOFs can be designed and synthesized into precursors with different structures and pore sizes by changing metal types or adjusting organic ligands, so that a variety of porous materials are obtained.
The Zeolite Imidazolate Frameworks (ZIFs) are a subfamily of MOF materials consisting of N-rich organic ligands, and are ideal substrates for preparing N-doped porous carbon materials, and currently common framework structures are ZIF-67 and ZIF-8. The main synthesis methods of ZIF-67 include solvothermal method, mechanical stirring method, liquid phase diffusion method, crystallization method, ultrasonic assisted synthesis method and the like, and each synthesis method has advantages and disadvantages, but the use of organic solvents such as methanol and the like is involved, so that the environment is polluted, and the recovery treatment of the solvents is complex. Relatively speaking, the mechanical stirring method is the most common method for synthesizing ZIF-67, the operation is simple, and the ligand and the transition metal salt are only required to be placed in the same solvent and continuously stirred until crystals are generated; however, the reaction process requires the use of a large amount of organic solvents, and the yield is low, which limits the application of the method.
Disclosure of Invention
Aiming at the problems in the prior art, the invention aims to provide the preparation method of the Co-NC nano catalyst, which has the advantages of simple operation, no pollution solvent such as methanol in the preparation process, mild reaction condition, one-step in-place crystallization and calcination process and low equipment requirement.
In order to achieve the above purpose, the invention adopts the following technical scheme.
A preparation method of a porous aza-carbon nanofiber oxygen reduction catalyst is characterized in that an electrostatic spinning method is adopted to prepare Co 2+/PAN nanofiber, ZIF-67 crystals are grown on the surface of the Co 2+/PAN nanofiber in situ by a chemical vapor deposition method, and finally high-temperature carbonization is carried out to prepare the Co-NC nanofiber catalyst.
More preferably, the preparation method mainly comprises the following steps: 1) Preparing PAN/DMF mother liquor; 2) Adding cobalt salt into PAN/DMF mother liquor to prepare Co 2+/PAN spinning solution; 3) Preparing Co 2+/PAN nanofiber by adopting an electrostatic spinning method; 4) Placing Co 2+/PAN nanofiber at a temperature control probe of a tube furnace, placing a certain amount of 2-methylimidazole and a solvent at an inlet of a heat preservation layer of the tube furnace, setting heating rate, carbonization temperature and heat preservation time, and introducing nitrogen for protection in the whole process; 5) And (3) keeping the ZIF-67/PAN nanofiber membrane generated by the reaction in the step (4) in a tube furnace, resetting the heating rate, the carbonization temperature and the heat preservation time, and introducing nitrogen for protection in the whole process.
More preferably, in the PAN/DMF mother liquor, the mass fraction of PAN is 8% -12%, DMF is subjected to water removal treatment, and the mixed liquor needs to be stirred for more than 48 hours until the solution is yellow-brown transparent.
More preferably, co 2+ in the Co 2+/PAN spinning solution is derived from cobalt acetate crystals Co (CH 3COO)2•4H2 O, and the mass ratio of the cobalt acetate crystals to the PAN/DMF in the spinning solution is 1:4-2.5:1.
More preferably, in step 3), the spinning voltage is set to 15-18 KV, the needle size is 22+ -1 gause, and the distance between the needle and the receiving plate is 18+ -0.5 cm.
More preferably, in the step 4), the mass of the 2-methylimidazole is 5+/-0.5 g, the solvent is deionized water, ethanol or acetone, and the solvent taking amount is 2+/-0.1 mL.
More preferably, in the step 4), the furnace temperature is set to 220-260 ℃, the heating rate is 3-5 ℃/min, and the heat preservation time is set to 1-5 h.
More preferably, in the step 5), the carbonization temperature is 800-850 ℃, the heating rate is 1-2 ℃/min, and the heat preservation time is 0.5-2 h.
The porous aza-carbon nanofiber oxygen reduction catalyst is characterized by being the Co-NC nano catalyst prepared by the method.
The beneficial effects of the invention are as follows: preparing Co 2+/PAN-containing nano fibers by using an electrostatic spinning and chemical vapor deposition method, growing ZIF-67 on the surfaces of the PAN nano fibers in situ by using the chemical vapor deposition method, and obtaining the CO-NC nano catalyst with uniform particles by using a one-step calcination method; solves the problems of long reaction time, organic solvent methanol in the reaction process, environmental protection inadequately, low yield, high impurity content and the like of the traditional mechanical stirring method.
The invention adopts electrostatic spinning and chemical vapor deposition method, does not need methanol solvent, is economical and environment-friendly, and meanwhile ZIF-67 can grow in situ on the surface of PAN nanofiber, has short reaction time and simple operation, and simultaneously crystals can be uniformly dispersed on the surface of the nanofiber; in addition, the invention can avoid the problems of nonuniform crystal size and more impurities of ZIF-67 existing in a water/solvent heating method or a stirring method, and the prepared sample is relatively pure and has less impurities; the catalyst prepared by the subsequent carbonization treatment takes ZIF-67 as a template, a carbon-containing electrocatalytic material is synthesized in a ZIF-67 pore canal, the particle size is uniform, and the catalytic performances of oxygen reduction and oxygen precipitation are obviously improved; has high catalytic activity in the electrocatalytic Oxygen Reduction Reaction (ORR) and the Oxygen Evolution Reaction (OER), and has wide application prospect in the fields of fuel cells, metal-air batteries and the like.
Drawings
FIG. 1 is a schematic diagram of the present invention for growing ZIF-67 on the surface of nanofibers by chemical vapor deposition.
FIG. 2 is a SEM image of ZIF-67/PAN produced in the present invention.
Reference numerals are used.
1: Tube furnace, 2: temperature control probe, 3: inlet of heat preservation layer of tube furnace, 4: co 2+/PAN nanofiber, 5: 2-methylimidazole, 6: and (3) a solvent.
Detailed Description
The following describes the specific embodiments of the present invention further, so that the technical scheme and the beneficial effects of the present invention are clearer and more definite. The following description of the embodiments is illustrative and is intended to be illustrative of the invention and is not to be construed as limiting the invention.
Additional aspects and advantages of the invention will be set forth in part in the description which follows, or may be learned by practice of the invention.
The preparation method of the porous aza-carbon nanofiber oxygen reduction catalyst comprises the steps of firstly adopting an electrostatic spinning method to prepare Co 2+/PAN nanofiber, then adopting a chemical vapor deposition method to grow ZIF-67 crystals on the surface of the Co 2+/PAN nanofiber in situ, and finally preparing the Co-NC nano catalyst through high-temperature carbonization.
The invention grows ZIF-67 on the surface of the nanofiber by utilizing a chemical vapor deposition method, and the ligand 2-methylimidazole volatilizes and diffuses at high temperature to reach the surface of the fiber and is coordinated with Co 2+ ions to generate ZIF-67. Compared with the traditional solution soaking method for growing ZIF-67 on the surface of the fiber, the method can avoid the use of a large amount of solvents, and meanwhile, the method does not involve the problem of solvent recovery treatment, and the fiber membrane also does not involve the subsequent impurity removal procedure; the traditional solution method for growing ZIF-67 on the surface of the fiber mainly depends on the adsorption of the fiber to ZIF-67 crystals in the solution, but is not in-situ growth process on the surface of the fiber. In addition, the ZIF-67/PAN nanofiber membrane has a large number of porous structures on the surface after high-temperature carbonization, and is very beneficial to improving the specific surface area and the electrocatalytic performance of the material; the fiber membrane can also maintain certain flexibility and mechanical properties and can serve as a flexible self-supporting electrode.
Example 1.
The preparation process of porous aza carbon nanometer fiber oxygen reducing catalyst includes the following steps.
1) Preparing PAN/DMF mother liquor with the mass fraction of 10%. Weigh 1gPAN in a capped glass bottle and add anhydrous DMF dropwise to 10g, then stir the mixture for 48h until the solution appears yellowish brown transparent.
It should be noted that in the PAN/DMF mother liquor, the mass fraction of PAN should be between 8% -12%, the proportion is too high, PAN is difficult to dissolve in anhydrous DMF, and meanwhile, the spinning solution is difficult to extrude in the subsequent electrostatic spinning process; the proportion is too low, the consumption of anhydrous DMF for dispersing transition metal salt in the spinning solution prepared in the step 2) can be reduced, so that the problem of nonuniform dispersion of metal salt exists, and finally the fiber morphology and the uniformity of the subsequent distribution of ZIF-67 crystals on the surface of PAN nanofibers can be affected.
2) Preparation of Co 2+/PAN spinning solution. Cobalt acetate crystal Co (CH 3COO)2·4H2 O and PAN in the step 1) are weighed for standby according to the mass ratio of 1:2.
The monomer is cobalt acetate crystal Co (CH 3COO)2·4H2 O is because cobalt acetate crystal contains less crystal water than cobalt nitrate crystal, the fiber solidification process is faster in the spinning process, and the obtained fiber morphology meets the design requirement.
3) And preparing the Co 2+/PAN nanofiber by electrostatic spinning. The spinning voltage was set to 15-18 KV, the needle size was 22.+ -.1 gause, and the distance between the needle and the receiving plate was 18.+ -. 0.5cm.
The spinning voltage can influence the appearance of the fiber, the voltage is too low, and the electric field force applied to the liquid drops extruded from the needle head is insufficient to overcome the intermolecular acting force, so that smaller liquid drops cannot be formed separately and stretched into filaments under the action of the electric field, and most of liquid drops or bead structures are finally obtained on the receiving plate; the needle size and the distance between the needle and the receiving plate also affect the fiber morphology, and the size of the spun yarn with the needle size being too large is in the micron level; when the distance between the needle and the receiving plate is too large, the fibers solidify too early before reaching the receiving plate, and when the distance is too small, the solvent does not volatilize.
4) The CVD method grows ZIF-67 on the surface of Co 2+/PAN nanofiber in situ. Referring to FIG. 1, co 2+/PAN nanofiber 4 is placed at a temperature control probe 2 of a tube furnace 1, 5+ -0.5 g of 2-methylimidazole 5 and 2+ -0.1 mL of solvent 6 (deionized water, ethanol or acetone) are placed at an inlet 3 of a heat preservation layer of the tube furnace, the furnace temperature is set to 220 ℃, the heating rate is set to 5 ℃/min, the heat preservation time is set to 1h, and nitrogen protection is performed in the whole process.
5) And (3) synthesizing the Co-NC nano catalyst. And (3) placing the ZIF-67/PAN nanofiber membrane obtained by growth in the step (4) in a tube furnace, wherein the carbonization temperature is 850 ℃, the heating rate is 2 ℃/min, the heat preservation time is 0.5h, and the whole process is protected by nitrogen.
The carbonization temperature is too high, the nitrogen content of the finally obtained catalyst is reduced, the frame structure of the ZIF-67 is collapsed, the temperature rising speed is too high, the heat preservation time is too long, the frame structure of the ZIF-67 is difficult to maintain, and meanwhile, metal nano particles are easy to agglomerate.
Example 2.
The preparation process of porous aza carbon nanometer fiber oxygen reducing catalyst includes the following steps.
1) Preparing PAN/DMF mother liquor with the mass fraction of 10%. Weigh 1.2gPAN in a capped glass bottle and add anhydrous DMF dropwise to 10g, then stir the mixture for 48h until the solution appears yellowish brown transparent.
2) Preparation of Co 2+/PAN spinning solution. Cobalt acetate crystal Co (CH 3COO)2·4H2 O and PAN in the step 1) are weighed for standby according to the mass ratio of 1:4.
3) And preparing the Co 2+/PAN nanofiber by electrostatic spinning. The spinning voltage was set to 15-18 KV, the needle size was 22.+ -.1 gause, and the distance between the needle and the receiving plate was 18.+ -. 0.5cm.
4) The CVD method grows ZIF-67 on the surface of Co 2+/PAN nanofiber in situ. Co 2+/PAN nanofiber 4 is placed at a temperature control probe 2 of a tube furnace 1, 5+/-0.5 g of 2-methylimidazole 5 and 2+/-0.1 mL of solvent 6 (deionized water, ethanol or acetone) are placed at an inlet 3 of a heat preservation layer of the tube furnace, the furnace temperature is set to be 260 ℃, the heating rate is set to be 5 ℃/min, the heat preservation time is set to be 2 hours, and nitrogen protection is carried out in the whole process.
5) And (3) synthesizing the Co-NC nano catalyst. Placing the ZIF-67/PAN nanofiber membrane obtained by growth in the step 4) into a tube furnace, wherein the carbonization temperature is 830 ℃, the heating rate is 2 ℃/min, the heat preservation time is 0.8h, and the whole process is protected by nitrogen.
Example 3.
The preparation process of porous aza carbon nanometer fiber oxygen reducing catalyst includes the following steps.
1) Preparing PAN/DMF mother liquor with the mass fraction of 10%. Weigh 0.8gPAN in a capped glass bottle and drop dry DMF to 10g, then stir the mixture for 48h until the solution appears yellowish brown transparent.
2) Preparation of Co 2+/PAN spinning solution. Cobalt acetate crystal Co (CH 3COO)2·4H2 O and PAN in the step 1) are weighed for standby according to the mass ratio of 2.5:1.
3) And preparing the Co 2+/PAN nanofiber by electrostatic spinning. The spinning voltage was set to 15-18 KV, the needle size was 22.+ -.1 gause, and the distance between the needle and the receiving plate was 18.+ -. 0.5cm.
4) The CVD method grows ZIF-67 on the surface of Co 2+/PAN nanofiber in situ. Co 2+/PAN nanofiber 4 is placed at a temperature control probe 2 of a tube furnace 1, 5+/-0.5 g of 2-methylimidazole 5 and 2+/-0.1 mL of solvent 6 (deionized water, ethanol or acetone) are placed at an inlet 3 of a heat preservation layer of the tube furnace, the furnace temperature is set to 240 ℃, the heating rate is set to 4 ℃/min, the heat preservation time is set to 3 hours, and nitrogen is fully introduced for protection.
5) And (3) synthesizing the Co-NC nano catalyst. And (3) placing the ZIF-67/PAN nanofiber membrane obtained by growth in the step (4) in a tube furnace, wherein the carbonization temperature is 800 ℃, the heating rate is1 ℃/min, the heat preservation time is 2.0h, and the whole process is protected by nitrogen.
Example 4.
The preparation process of porous aza carbon nanometer fiber oxygen reducing catalyst includes the following steps.
1) Preparing PAN/DMF mother liquor with the mass fraction of 10%. 1.0gPAN was weighed into a capped glass bottle and anhydrous DMF was added dropwise to 10g, followed by stirring the mixture for 48h until the solution appeared yellowish brown in color and transparent.
2) Preparation of Co 2+/PAN spinning solution. Cobalt acetate crystal Co (CH 3COO)2·4H2 O and PAN in the step 1) are weighed for standby according to the mass ratio of 1:1.
3) And preparing the Co 2+/PAN nanofiber by electrostatic spinning. The spinning voltage was set to 15-18 KV, the needle size was 22.+ -.1 gause, and the distance between the needle and the receiving plate was 18.+ -. 0.5cm.
4) The CVD method grows ZIF-67 on the surface of Co 2+/PAN nanofiber in situ. Co 2+/PAN nanofiber 4 is placed at a temperature control probe 2 of a tube furnace 1, 5+/-0.5 g of 2-methylimidazole 5 and 2+/-0.1 mL of solvent 6 (deionized water, ethanol or acetone) are placed at an inlet 3 of a heat preservation layer of the tube furnace, the furnace temperature is set to 240 ℃, the heating rate is set to 3 ℃/min, the heat preservation time is set to 5h, and nitrogen is fully introduced for protection.
5) And (3) synthesizing the Co-NC nano catalyst. And (3) placing the ZIF-67/PAN nanofiber membrane obtained by growth in the step (4) in a tube furnace, wherein the carbonization temperature is 820 ℃, the heating rate is 2 ℃/min, the heat preservation time is 1h, and the whole process is protected by nitrogen.
In the present invention, SEM image of ZIF-67/PAN obtained by growth is shown in FIG. 2. From this figure, it can be seen that uniform, dense ZIF-67 growth was obtained on the surface of the PAN nanofibers.
Example 5.
The preparation process of porous aza carbon nanometer fiber oxygen reducing catalyst includes the following steps.
1) Preparing PAN/DMF mother liquor with the mass fraction of 10%. 1.0gPAN was weighed into a capped glass bottle and anhydrous DMF was added dropwise to 10g, followed by stirring the mixture for 48h until the solution appeared yellowish brown in color and transparent.
2) Preparation of Co 2+/PAN spinning solution. Cobalt acetate crystal Co (CH 3COO)2·4H2 O and PAN in the step 1) are weighed for standby according to the mass ratio of 1.5:1.
3) And preparing the Co 2+/PAN nanofiber by electrostatic spinning. The spinning voltage was set to 15-18 KV, the needle size was 22.+ -.1 gause, and the distance between the needle and the receiving plate was 18.+ -. 0.5cm.
4) The CVD method grows ZIF-67 on the surface of Co 2+/PAN nanofiber in situ. Co 2+/PAN nanofiber 4 is placed at a temperature control probe 2 of a tube furnace 1, 5+/-0.5 g of 2-methylimidazole 5 and 2+/-0.1 mL of solvent 6 (deionized water, ethanol or acetone) are placed at an inlet 3 of a heat preservation layer of the tube furnace, the furnace temperature is set to 240 ℃, the heating rate is set to 4 ℃/min, the heat preservation time is set to 3 hours, and nitrogen is fully introduced for protection.
5) And (3) synthesizing the Co-NC nano catalyst. And (3) placing the ZIF-67/PAN nanofiber membrane obtained by growth in the step (4) in a tube furnace, wherein the carbonization temperature is 820 ℃, the heating rate is 1 ℃/min, the heat preservation time is 1h, and the whole process is protected by nitrogen.
In the present invention, SEM image of ZIF-67/PAN obtained by growth is shown in FIG. 2. From this figure, it can be seen that uniform, dense ZIF-67 growth was obtained on the surface of the PAN nanofibers.
It will be understood by those skilled in the art from the foregoing description of the structure and principles that the present invention is not limited to the specific embodiments described above, but is intended to cover modifications and alternatives falling within the spirit and scope of the invention as defined by the appended claims and their equivalents. The portions of the detailed description that are not presented are all prior art or common general knowledge.
Noun interpretation.
PAN, acronym for english for polyacrylonitrile.
DMF, english abbreviation for dimethylformamide.
ZIF, english abbreviation for zeolitic imidazolate framework materials.
Claims (4)
1. The preparation method of the porous aza-carbon nanofiber oxygen reduction catalyst is characterized by comprising the steps of firstly preparing Co 2+/PAN nanofiber by adopting an electrostatic spinning method, then growing ZIF-67 crystals on the surface of the Co 2+/PAN nanofiber in situ by adopting a chemical vapor deposition method, and finally carbonizing at a high temperature to prepare the Co-NC nanofiber catalyst;
The method mainly comprises the following steps:
1) Preparing PAN/DMF mother liquor;
2) Adding cobalt salt into PAN/DMF mother liquor to prepare Co 2+/PAN spinning solution;
3) Preparing Co 2+/PAN nanofiber by adopting an electrostatic spinning method;
4) Placing Co 2+/PAN nanofiber at a temperature control probe of a tube furnace, placing a certain amount of 2-methylimidazole and a solvent at an inlet of a heat preservation layer of the tube furnace, setting heating rate, carbonization temperature and heat preservation time, and introducing nitrogen for protection in the whole process; the solvent is deionized water, ethanol or acetone;
5) Keeping the ZIF-67/PAN nanofiber membrane generated by the reaction in the step 4) in a tube furnace, resetting the heating rate, the carbonization temperature and the heat preservation time, and introducing nitrogen for protection in the whole process;
Co 2+ in the Co 2+/PAN spinning solution is derived from cobalt acetate crystals Co (CH 3COO)2•4H2 O, and the mass ratio of the cobalt acetate crystals to PAN/DMF in the spinning solution is 1:4-2.5:1;
In the step 4), the mass of the 2-methylimidazole is 5+/-0.5 g, and the solvent taking amount is 2+/-0.1 mL; setting the furnace temperature to 220-260 ℃, the heating rate to 3-5 ℃/min, and the heat preservation time to 1-5 h;
In the step 5), the carbonization temperature is 800-850 ℃, the heating rate is 1-2 ℃/min, and the heat preservation time is 0.5-2 h.
2. The preparation method of the porous aza-carbon nanofiber oxygen reduction catalyst according to claim 1, wherein the mass fraction of PAN in the PAN/DMF mother liquor is 8% -12%, DMF is subjected to water removal treatment, and the mixed liquor needs to be stirred for more than 48 hours until the solution is yellow brown transparent.
3. The method for preparing a porous aza-carbon nanofiber oxygen reduction catalyst according to claim 1, wherein in step 3), the spinning voltage is set to 15-18 KV, the needle size is 22±1gause, and the distance between the needle and the receiving plate is 18±0.5cm.
4. A porous aza-carbon nanofiber oxygen reduction catalyst characterized by being a Co-NC nanocatalyst produced by the production method according to any one of claims 1 to 3.
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