CN115548352B - Method for improving durability of metal-nitrogen-carbon electrocatalyst and application of method in field of fuel cells - Google Patents
Method for improving durability of metal-nitrogen-carbon electrocatalyst and application of method in field of fuel cells Download PDFInfo
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- CN115548352B CN115548352B CN202211193962.4A CN202211193962A CN115548352B CN 115548352 B CN115548352 B CN 115548352B CN 202211193962 A CN202211193962 A CN 202211193962A CN 115548352 B CN115548352 B CN 115548352B
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- 239000010411 electrocatalyst Substances 0.000 title claims abstract description 68
- 229910052799 carbon Inorganic materials 0.000 title claims abstract description 52
- 238000000034 method Methods 0.000 title claims abstract description 29
- 239000000446 fuel Substances 0.000 title claims abstract description 10
- 238000001035 drying Methods 0.000 claims abstract description 33
- 229920000463 Poly(ethylene glycol)-block-poly(propylene glycol)-block-poly(ethylene glycol) Polymers 0.000 claims abstract description 30
- 239000000203 mixture Substances 0.000 claims abstract description 25
- XKRFYHLGVUSROY-UHFFFAOYSA-N Argon Chemical compound [Ar] XKRFYHLGVUSROY-UHFFFAOYSA-N 0.000 claims abstract description 24
- VTLYFUHAOXGGBS-UHFFFAOYSA-N Fe3+ Chemical compound [Fe+3] VTLYFUHAOXGGBS-UHFFFAOYSA-N 0.000 claims abstract description 20
- 239000000463 material Substances 0.000 claims abstract description 20
- KSFOVUSSGSKXFI-GAQDCDSVSA-N CC1=C/2NC(\C=C3/N=C(/C=C4\N\C(=C/C5=N/C(=C\2)/C(C=C)=C5C)C(C=C)=C4C)C(C)=C3CCC(O)=O)=C1CCC(O)=O Chemical compound CC1=C/2NC(\C=C3/N=C(/C=C4\N\C(=C/C5=N/C(=C\2)/C(C=C)=C5C)C(C=C)=C4C)C(C)=C3CCC(O)=O)=C1CCC(O)=O KSFOVUSSGSKXFI-GAQDCDSVSA-N 0.000 claims abstract description 18
- 229950003776 protoporphyrin Drugs 0.000 claims abstract description 17
- 229910052786 argon Inorganic materials 0.000 claims abstract description 12
- GVPFVAHMJGGAJG-UHFFFAOYSA-L cobalt dichloride Chemical compound [Cl-].[Cl-].[Co+2] GVPFVAHMJGGAJG-UHFFFAOYSA-L 0.000 claims abstract description 11
- ZAMOUSCENKQFHK-UHFFFAOYSA-N Chlorine atom Chemical compound [Cl] ZAMOUSCENKQFHK-UHFFFAOYSA-N 0.000 claims abstract description 6
- 239000000460 chlorine Substances 0.000 claims abstract description 6
- 229910052801 chlorine Inorganic materials 0.000 claims abstract description 6
- RVGRUAULSDPKGF-UHFFFAOYSA-N Poloxamer Chemical compound C1CO1.CC1CO1 RVGRUAULSDPKGF-UHFFFAOYSA-N 0.000 claims abstract 5
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 37
- KWYUFKZDYYNOTN-UHFFFAOYSA-M Potassium hydroxide Chemical compound [OH-].[K+] KWYUFKZDYYNOTN-UHFFFAOYSA-M 0.000 claims description 34
- OKKJLVBELUTLKV-UHFFFAOYSA-N Methanol Chemical compound OC OKKJLVBELUTLKV-UHFFFAOYSA-N 0.000 claims description 33
- 239000008367 deionised water Substances 0.000 claims description 27
- 229910021641 deionized water Inorganic materials 0.000 claims description 27
- VEXZGXHMUGYJMC-UHFFFAOYSA-N Hydrochloric acid Chemical compound Cl VEXZGXHMUGYJMC-UHFFFAOYSA-N 0.000 claims description 22
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 claims description 22
- 238000010438 heat treatment Methods 0.000 claims description 22
- 238000000227 grinding Methods 0.000 claims description 18
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 claims description 17
- 239000003054 catalyst Substances 0.000 claims description 17
- 238000003763 carbonization Methods 0.000 claims description 13
- 238000009210 therapy by ultrasound Methods 0.000 claims description 12
- 229910052742 iron Inorganic materials 0.000 claims description 11
- 230000007935 neutral effect Effects 0.000 claims description 11
- 238000010000 carbonizing Methods 0.000 claims description 10
- JIAARYAFYJHUJI-UHFFFAOYSA-L zinc dichloride Chemical compound [Cl-].[Cl-].[Zn+2] JIAARYAFYJHUJI-UHFFFAOYSA-L 0.000 claims description 10
- 239000003960 organic solvent Substances 0.000 claims description 9
- ZMXDDKWLCZADIW-UHFFFAOYSA-N N,N-Dimethylformamide Chemical compound CN(C)C=O ZMXDDKWLCZADIW-UHFFFAOYSA-N 0.000 claims description 6
- 238000005406 washing Methods 0.000 claims description 6
- 235000005074 zinc chloride Nutrition 0.000 claims description 6
- 239000011592 zinc chloride Substances 0.000 claims description 6
- 230000007547 defect Effects 0.000 claims description 5
- KFZMGEQAYNKOFK-UHFFFAOYSA-N Isopropanol Chemical compound CC(C)O KFZMGEQAYNKOFK-UHFFFAOYSA-N 0.000 claims description 4
- 239000012300 argon atmosphere Substances 0.000 claims description 4
- 239000012046 mixed solvent Substances 0.000 claims description 4
- 238000002156 mixing Methods 0.000 claims description 4
- 238000005119 centrifugation Methods 0.000 claims description 2
- SBZXBUIDTXKZTM-UHFFFAOYSA-N diglyme Chemical compound COCCOCCOC SBZXBUIDTXKZTM-UHFFFAOYSA-N 0.000 claims description 2
- 235000019441 ethanol Nutrition 0.000 claims description 2
- 230000008569 process Effects 0.000 claims description 2
- 229910002558 Fe-Nx Inorganic materials 0.000 abstract description 41
- 229910002559 Fe−Nx Inorganic materials 0.000 abstract description 41
- 229910002444 Co–Nx Inorganic materials 0.000 abstract description 35
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 abstract description 9
- 229910000510 noble metal Inorganic materials 0.000 abstract description 7
- KDLHZDBZIXYQEI-UHFFFAOYSA-N Palladium Chemical compound [Pd] KDLHZDBZIXYQEI-UHFFFAOYSA-N 0.000 abstract description 4
- 238000002360 preparation method Methods 0.000 abstract description 3
- 239000002131 composite material Substances 0.000 abstract description 2
- PCHJSUWPFVWCPO-UHFFFAOYSA-N gold Chemical compound [Au] PCHJSUWPFVWCPO-UHFFFAOYSA-N 0.000 abstract description 2
- 229910052737 gold Inorganic materials 0.000 abstract description 2
- 239000010931 gold Substances 0.000 abstract description 2
- 229910052763 palladium Inorganic materials 0.000 abstract description 2
- 238000000197 pyrolysis Methods 0.000 abstract description 2
- 238000011031 large-scale manufacturing process Methods 0.000 abstract 1
- CFQCIHVMOFOCGH-UHFFFAOYSA-N platinum ruthenium Chemical compound [Ru].[Pt] CFQCIHVMOFOCGH-UHFFFAOYSA-N 0.000 abstract 1
- 239000002994 raw material Substances 0.000 description 57
- 239000000243 solution Substances 0.000 description 38
- 230000002378 acidificating effect Effects 0.000 description 19
- 229910017052 cobalt Inorganic materials 0.000 description 19
- 239000010941 cobalt Substances 0.000 description 19
- GUTLYIVDDKVIGB-UHFFFAOYSA-N cobalt atom Chemical compound [Co] GUTLYIVDDKVIGB-UHFFFAOYSA-N 0.000 description 19
- BASFCYQUMIYNBI-UHFFFAOYSA-N platinum Chemical compound [Pt] BASFCYQUMIYNBI-UHFFFAOYSA-N 0.000 description 16
- 230000000052 comparative effect Effects 0.000 description 15
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 14
- 230000010287 polarization Effects 0.000 description 13
- AQTFKGDWFRRIHR-UHFFFAOYSA-L 3-[18-(2-carboxylatoethyl)-8,13-bis(ethenyl)-3,7,12,17-tetramethylporphyrin-21,24-diid-2-yl]propanoate;cobalt(2+);hydron Chemical compound [Co+2].[N-]1C(C=C2C(=C(C)C(C=C3C(=C(C)C(=C4)[N-]3)C=C)=N2)C=C)=C(C)C(CCC(O)=O)=C1C=C1C(CCC(O)=O)=C(C)C4=N1 AQTFKGDWFRRIHR-UHFFFAOYSA-L 0.000 description 12
- VEXZGXHMUGYJMC-UHFFFAOYSA-M Chloride anion Chemical compound [Cl-] VEXZGXHMUGYJMC-UHFFFAOYSA-M 0.000 description 11
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 9
- 238000004140 cleaning Methods 0.000 description 9
- 238000001816 cooling Methods 0.000 description 9
- 229910052757 nitrogen Inorganic materials 0.000 description 9
- 229910052760 oxygen Inorganic materials 0.000 description 9
- 239000001301 oxygen Substances 0.000 description 9
- 239000000843 powder Substances 0.000 description 9
- 238000012360 testing method Methods 0.000 description 9
- 238000007605 air drying Methods 0.000 description 8
- 229910052751 metal Inorganic materials 0.000 description 8
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- 239000002184 metal Substances 0.000 description 6
- 238000001228 spectrum Methods 0.000 description 6
- QWPPOHNGKGFGJK-UHFFFAOYSA-N hypochlorous acid Chemical compound ClO QWPPOHNGKGFGJK-UHFFFAOYSA-N 0.000 description 5
- 230000008859 change Effects 0.000 description 4
- 238000005087 graphitization Methods 0.000 description 4
- 229910052697 platinum Inorganic materials 0.000 description 4
- 238000006722 reduction reaction Methods 0.000 description 4
- 238000001237 Raman spectrum Methods 0.000 description 3
- 239000007864 aqueous solution Substances 0.000 description 3
- 230000003197 catalytic effect Effects 0.000 description 3
- 238000002484 cyclic voltammetry Methods 0.000 description 3
- 230000007423 decrease Effects 0.000 description 3
- MWUXSHHQAYIFBG-UHFFFAOYSA-N nitrogen oxide Inorganic materials O=[N] MWUXSHHQAYIFBG-UHFFFAOYSA-N 0.000 description 3
- 239000011148 porous material Substances 0.000 description 3
- 239000002244 precipitate Substances 0.000 description 3
- 230000009467 reduction Effects 0.000 description 3
- 229920006395 saturated elastomer Polymers 0.000 description 3
- 229910052723 transition metal Inorganic materials 0.000 description 3
- 150000003624 transition metals Chemical class 0.000 description 3
- CKUAXEQHGKSLHN-UHFFFAOYSA-N [C].[N] Chemical compound [C].[N] CKUAXEQHGKSLHN-UHFFFAOYSA-N 0.000 description 2
- 230000004913 activation Effects 0.000 description 2
- 230000002238 attenuated effect Effects 0.000 description 2
- 239000003795 chemical substances by application Substances 0.000 description 2
- 230000003247 decreasing effect Effects 0.000 description 2
- 238000013461 design Methods 0.000 description 2
- 238000003795 desorption Methods 0.000 description 2
- 238000009826 distribution Methods 0.000 description 2
- 230000000694 effects Effects 0.000 description 2
- 229910002804 graphite Inorganic materials 0.000 description 2
- 239000010439 graphite Substances 0.000 description 2
- 238000011068 loading method Methods 0.000 description 2
- 238000004519 manufacturing process Methods 0.000 description 2
- 239000000693 micelle Substances 0.000 description 2
- 231100000572 poisoning Toxicity 0.000 description 2
- 230000000607 poisoning effect Effects 0.000 description 2
- 238000001338 self-assembly Methods 0.000 description 2
- 238000001179 sorption measurement Methods 0.000 description 2
- 238000003860 storage Methods 0.000 description 2
- UGDAWAQEKLURQI-UHFFFAOYSA-N 2-(2-hydroxyethoxy)ethanol;hydrate Chemical compound O.OCCOCCO UGDAWAQEKLURQI-UHFFFAOYSA-N 0.000 description 1
- 241000207836 Olea <angiosperm> Species 0.000 description 1
- 238000001069 Raman spectroscopy Methods 0.000 description 1
- 230000010757 Reduction Activity Effects 0.000 description 1
- 238000002441 X-ray diffraction Methods 0.000 description 1
- SEQUALWBCFCDGP-UHFFFAOYSA-N [C].[N].[Fe] Chemical compound [C].[N].[Fe] SEQUALWBCFCDGP-UHFFFAOYSA-N 0.000 description 1
- AAMATCKFMHVIDO-UHFFFAOYSA-N azane;1h-pyrrole Chemical compound N.C=1C=CNC=1 AAMATCKFMHVIDO-UHFFFAOYSA-N 0.000 description 1
- DLGYNVMUCSTYDQ-UHFFFAOYSA-N azane;pyridine Chemical compound N.C1=CC=NC=C1 DLGYNVMUCSTYDQ-UHFFFAOYSA-N 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 239000003575 carbonaceous material Substances 0.000 description 1
- 239000000969 carrier Substances 0.000 description 1
- 238000012512 characterization method Methods 0.000 description 1
- 239000003153 chemical reaction reagent Substances 0.000 description 1
- -1 co-N Inorganic materials 0.000 description 1
- 150000001875 compounds Chemical class 0.000 description 1
- 230000007797 corrosion Effects 0.000 description 1
- 238000005260 corrosion Methods 0.000 description 1
- 238000011161 development Methods 0.000 description 1
- ZOMNIUBKTOKEHS-UHFFFAOYSA-L dimercury dichloride Chemical class Cl[Hg][Hg]Cl ZOMNIUBKTOKEHS-UHFFFAOYSA-L 0.000 description 1
- 238000000840 electrochemical analysis Methods 0.000 description 1
- 238000003487 electrochemical reaction Methods 0.000 description 1
- IXCSERBJSXMMFS-UHFFFAOYSA-N hcl hcl Chemical compound Cl.Cl IXCSERBJSXMMFS-UHFFFAOYSA-N 0.000 description 1
- 230000007774 longterm Effects 0.000 description 1
- 150000002739 metals Chemical class 0.000 description 1
- 238000001000 micrograph Methods 0.000 description 1
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- 238000011160 research Methods 0.000 description 1
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Classifications
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M4/00—Electrodes
- H01M4/86—Inert electrodes with catalytic activity, e.g. for fuel cells
- H01M4/90—Selection of catalytic material
- H01M4/9008—Organic or organo-metallic compounds
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M4/00—Electrodes
- H01M4/86—Inert electrodes with catalytic activity, e.g. for fuel cells
- H01M4/88—Processes of manufacture
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
- Y02E60/30—Hydrogen technology
- Y02E60/50—Fuel cells
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- Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Electrochemistry (AREA)
- General Chemical & Material Sciences (AREA)
- Materials Engineering (AREA)
- Manufacturing & Machinery (AREA)
- Catalysts (AREA)
Abstract
The invention relates to a method for improving durability of a metal-nitrogen-carbon electrocatalyst and application thereof in the field of fuel cells, and belongs to the field of electrocatalyst materials of fuel cells. The preparation method comprises the following steps: and (3) taking PEG-PPG-PEG as a carbon source, self-assembling with chlorine protoporphyrin IX iron (III) and cobalt chloride protoporphyrin IX, drying to obtain a composite mixture, and carrying out one-step pyrolysis on the product under the condition of argon to prepare Fe-Nx & Co-Nx/CNCs. The preparation method of the bimetallic-nitrogen-carbon electrocatalyst has the advantages of simple operation, less flow, less equipment investment, good repeatability and convenience for solving the problem of difficult large-scale production, and provides a new choice for the carrier of noble metal electrocatalysts such as noble metal platinum ruthenium palladium gold and the like.
Description
Technical Field
The invention relates to a method for improving durability of a metal-nitrogen-carbon electrocatalyst and application thereof in the field of fuel cells, and belongs to the field of electrocatalyst materials of fuel cells.
Background
With the rapid development of the industrial revolution, the crisis of shortage of fossil energy has been affecting the production and life of humans, and some renewable energy sources have been developed, such as fuel cells, metal-air batteries, flow batteries, and the like. Oxygen reduction reactions play a very important role in these new energy devices. Noble metal platinum-based catalysts are considered the best oxygen-reducing electrocatalysts, but their storage scarcity, high recovery costs and poor durability problems prevent their large-scale commercial application. Therefore, it is urgent to rationally design an oxygen reduction electrocatalyst that is inexpensive and has a high storage capacity.
Transition metal-nitrogen-carbon (M-N-C) compounds are a novel class of catalytic materials with specific chemical and physical properties. In recent years, the use of M-N-C type catalysts in electrochemical reactions has become an emerging field of research, and in particular, M-N-C type catalysts containing a transition metal nitrogen X (M-N X) structure are considered to be the most likely alternative to commercial Pt/C catalysts for use as oxygen reduction electrocatalysts. In particular, fe-N-C catalysts are considered to be the most likely to replace noble metal platinum-based electrocatalysts, and iron resources are abundant, cheap and readily available compared with other metals. However, under acidic conditions, both the transition metal and the carbon-based support are easily corroded, thereby reducing the catalytic activity.
Disclosure of Invention
In order to find an alternative non-noble metal electrocatalyst, thoroughly get rid of dependence on imported products, select mature commercial raw materials from the cost, optimize the performance and durability of the electrocatalyst by adjusting the proportion of a bimetallic-nitrogen-carbon electrocatalyst formed by self-assembly of metallic element cobalt and metallic element iron, the invention designs a bimetallic-nitrogen-carbon electrocatalyst which is formed by simple process and self-assembly and improves the durability, and a preparation method and application thereof.
It is a first object of the present invention to provide a method for improving the durability of metal-nitrogen-carbon electrocatalysts.
A method of improving durability of a metal-nitrogen-carbon electrocatalyst comprising the steps of:
(1) Placing poly (ethylene glycol) -block-poly (propylene glycol) -block-poly (ethylene glycol) (PEG-PPG-PEG) in a beaker, then adding zinc chloride (ZnCl 2), adding a mixed solvent, carrying out ultrasonic treatment for 1-30 min, clarifying the solution, and marking as A; adding water into potassium hydroxide (KOH), chlorine protoporphyrin IX iron (III) and cobalt chloride protoporphyrin IX, and after ultrasonic treatment for 1-30 min, taking the solution as dark green, and marking as B; slowly pouring the B into the A to form a dark green sticky precipitate, and then drying the precipitate in a blast drying oven at 50-100 ℃ for 1-12 h to obtain an intermediate micelle and dark green precipitate mixture;
(2) Carbonizing the micelle and dark green precipitation mixture under the argon condition, washing, drying and grinding the obtained product to obtain black bimetallic-nitrogen-carbon (Fe-Nx & Co-Nx/CNCs) electrocatalyst powder.
Wherein the mixed solvent is formed by mixing water and an organic solvent; the ratio of the poly (ethylene glycol) -block-poly (propylene glycol) -block-poly (ethylene glycol) (PEG-PPG-PEG), the organic solvent and the water is 1-1000mg: 1-100 mL: 1 to 100mL, preferably 100mg:25mL:25mL; the mass ratio of the poly (ethylene glycol) -block-poly (propylene glycol) -block-poly (ethylene glycol) (PEG-PPG-PEG), zinc chloride, potassium hydroxide, chloroprotoporphyrin IX iron (III) and cobalt chloride protoporphyrin IX is 1-1000: 1-500: 1-500: 1-500: 1 to 100; preferably 100:40:30.8:20: 5.
Further, the organic solvent is methanol, ethanol, isopropanol, dimethylformamide or diethylene glycol dimethyl ether, and water and methanol are preferable.
Further, the volume ratio of water in A to water in B is 1-100:1-100 (e.g. 1-100 mL: 1-100 mL), preferably 5:1 (e.g., 50mL:10 mL).
Further, the volume ratio of the water to the organic solvent is 1-100:1-100 (e.g., 1-100 mL: 1-100 mL), preferably 1:1 (e.g., 50mL:50 mL).
Further, the number average molecular weight Mn of the poly (ethylene glycol) -block-poly (propylene glycol) -block-poly (ethylene glycol) (PEG-PPG-PEG) is 1000-60000 g/mol.
Further, in the step (1), the carbonization conditions of the bimetallic-nitrogen-carbon (Fe-Nx & Co-Nx/CNCs) electrocatalyst are: heating to 400-1000 ℃ at a heating rate of 1-10 ℃/min under argon atmosphere, preserving heat for 1-6 h, and then cooling to room temperature in a furnace, wherein m is the mass ratio of chlorine protoporphyrin IX iron (III) to cobalt chloride protoporphyrin IX, and is marked as Fe-Nx & Co-Nx/CNCs-m. Preferably, the carbonization conditions of the present invention are: under argon atmosphere, the temperature is raised to 700-900 ℃ at a heating rate of 5 ℃/min, the temperature is kept for 2-6 h, and then the mixture is cooled to room temperature along with a furnace, and the mixture is marked as Fe-Nx & Co-Nx/CNCs-m-T (wherein T is the temperature keeping temperature). Most preferably, the carbonization conditions are: and heating to 800 ℃ at a heating rate of 5 ℃/min under argon atmosphere, and preserving heat for 2h.
Further, in the step (2), the washing is acidic washing and activation, the obtained product is soaked in 1-8 mol/L hydrochloric acid (HCl) solution for 1-12 hours, and then is centrifuged to be neutral by deionized water and then is centrifugally cleaned by absolute ethyl alcohol; the centrifugation conditions are as follows: centrifuging for 2-10 min at 5000-10000 r/min. Preferably, the acidic wash activation of the present invention is: the obtained product is soaked by using 1-8 mol/L HCl solution, centrifuged by deionized water for 5min at 8000r/min, repeatedly centrifuged to be neutral, and then centrifuged by absolute ethyl alcohol for 5min at 8000r/min for cleaning. Further, the present invention preferably uses 3mol/L HCl solution.
Further, in the step (2), the conditions of drying after washing are: drying at 50-100 deg.c for 12-36 hr with blast drier.
It is another object of the present invention to provide a bimetallic-nitrogen-carbon electrocatalyst prepared by the above method. The bimetallic-nitrogen-carbon electrocatalyst has a hollow olive-shaped structure with abundant defects, the specific surface area is 100-3000 m 2·g-1, preferably 1108m 2·g-1
The bimetallic-nitrogen-carbon electrocatalyst provided by the invention has obviously improved durability on the premise that the performance of the bimetallic-nitrogen-carbon electrocatalyst is not attenuated after being modified by cobalt element.
It is a further object of the present invention to provide the use of the bimetallic-nitrogen-carbon electrocatalyst described above as a fuel cell cathode catalyst material and catalyst support material.
The cobalt (Co) element is a material which is more corrosion-resistant than the iron element, and particularly under the acidic condition, the introduction of cobalt can well protect the iron-based active site to prevent the iron-based active site from poisoning, in addition, the cobalt has higher electrocatalytic performance, and the introduction of a small amount of cobalt can not only keep the protection of the electrocatalytic agent, but also does not influence the performance of the electrocatalytic agent.
According to the invention, PEG-PPG-PEG is used as a carbon source, self-assembled with chlorine protoporphyrin IX iron (III) and cobalt chloride protoporphyrin IX, then, the self-assembled mixture is dried to obtain a composite mixture, and the product is pyrolyzed in one step under the condition of argon to prepare Fe-Nx & Co-Nx/CNCs. The cobalt chloride protoporphyrin IX (C 34H32ClCoN4O4) is taken as a cobalt source and is carefully combined with a metal iron-nitrogen-carbon material, the original Fe-Nx active site is protected due to the introduction of Co-Nx, and under the premise of not influencing the performance, the metal-nitrogen-carbon electrocatalyst is prevented from being poisoned by the introduction of cobalt, and the constructed bimetallic-nitrogen-carbon electrocatalyst solves the problem of insufficient durability of the catalyst under the acidic condition of single transition metal.
The cobalt chloride protoporphyrin IX contains a Co-Nx structure. Cobalt can well protect the Fe-N-C active site. A bimetallic-nitrogen-carbon electrocatalyst (Fe-Nx & Co-Nx/CNCs) was creatively designed after one-step pyrolysis. The bimetallic-nitrogen-carbon electrocatalyst well protects Fe-Nx active sites by introducing cobalt, directly protects the metal-nitrogen-carbon active sites during durability test, and indirectly protects a carbon carrier from poisoning, thereby protecting the overall oxygen reduction activity of the electrocatalyst. Bimetallic-nitrogen-carbon electrocatalysts also exhibit high long-term stability without sacrificing performance as oxygen electrocatalysts for fuel cell cathodes.
The beneficial effects of the invention are as follows: the bimetallic-nitrogen-carbon electrocatalyst material prepared by the method has good electrocatalysis performance, and the introduction of cobalt does not influence the electrocatalysis activity of iron serving as an active center, and the introduction of cobalt protects an Fe-Nx active site, so that the durability of the bimetallic-nitrogen-carbon electrocatalyst material is remarkably improved by introducing another metal. In addition, the catalyst can also be used as a carrier of a commercial platinum-based electrocatalyst. The method for preparing the bimetallic-nitrogen-carbon electrocatalyst has the advantages of simple operation, less flow, less equipment investment, good repeatability, convenient solution of the problem of mass production and provides a new choice for the carriers of noble metal electrocatalysts such as noble metals such as platinum, palladium and gold.
Drawings
FIG. 1 (a) is a Scanning Electron Microscope (SEM) image (scale bar 400 nm) of Fe-Nx & Co-Nx/CNCs-4 prepared according to example 1 of the present invention. FIG. 1 (b) is a scanning electron microscope image (SEM, scale 4 μm) of Fe-Nx & Co-Nx/CNCs-4 prepared according to example 1 of the present invention.
FIG. 2 (a) shows XRD patterns of the metal-nitrogen-carbon electrocatalyst materials prepared in example 1 and comparative example 1 according to the invention; FIG. 2 (b) is a Raman spectrum of the metal-nitrogen-carbon electrocatalyst material prepared in example 1 and comparative example 1 according to the invention.
Fig. 3 (a) to (b) show the XPS total spectrum and the N1s spectrum of the bimetallic-nitrogen-carbon electrocatalyst material prepared in example 1, respectively.
FIG. 4 (a) is a graph showing the adsorption and desorption of nitrogen from the bimetallic-nitrogen-carbon electrocatalyst material prepared in example 1; fig. 4 (b) shows the pore size distribution curve of the bimetallic-nitrogen-carbon electrocatalyst material prepared in example 1.
FIG. 5 (a) is a polarization curve of 1600rpm under acidic conditions of the metal-nitrogen-carbon electrocatalyst materials prepared in examples 1 to 3 and comparative example 1 according to the invention; FIG. 5 (b) is a polarization curve at 1600rpm under acidic conditions for the metal-nitrogen-carbon electrocatalysts prepared in examples 4-6 and comparative examples 1-2 of the invention.
FIG. 6 (a) is a cyclic voltammogram (nitrogen and oxygen) of the bimetallic nitrogen-carbon electrocatalyst material prepared in example 1 of the invention under acidic conditions, and FIG. 6 (b) is a polarization curve at 1600rpm for the metal nitrogen-carbon electrocatalysts prepared in example 1, comparative example 1, and comparative example 2 of the invention and commercial 20wt% Pt/C under acidic conditions.
FIG. 7 (a) is a polarization curve change during a durability test under acidic conditions for 20wt% Pt/C; fig. 7 (b) shows the change in polarization curve during durability test under acidic conditions of the bimetallic-nitrogen-carbon electrocatalyst prepared in example 1 according to the invention.
Detailed Description
The following non-limiting examples will enable those of ordinary skill in the art to more fully understand the invention and are not intended to limit the invention in any way.
The test methods described in the following examples, unless otherwise specified, are all conventional; the reagents and materials, unless otherwise specified, are commercially available.
Example 1
1) 100Mg of poly (ethylene glycol) -block-poly (propylene glycol) -block-poly (ethylene glycol) (PEG-PPG-PEG, number average molecular weight Mn at 12600 g/mol) and 40mgZnCl 2 were placed in a 250mL beaker, 50mL of deionized water and 50mL of methanol were added, and the solution was sonicated for 5min to make the solution clear and transparent, designated A.
2) Another 30.8mg KOH, 20mg of iron (III) chloroprotoporphyrin and 5mg of cobalt protoporphyrin IX chloride were placed in a 20mL sample bottle, 10mL deionized water was added and sonicated for 5min to make the solution greenish black and designated B.
3) Slowly pouring the B into the A, carrying out ultrasonic treatment for 5min, and drying at 60 ℃ in a forced air drying oven for 12h to obtain a dark green powder and film-shaped mixture.
4) Carbonizing the mixture in a tubular furnace filled with argon, wherein the carbonization procedure is as follows: heating to 800 ℃ from room temperature at a heating rate of 5 ℃/min, preserving heat for 2 hours, cooling to room temperature along with a furnace, and taking out and grinding; firstly soaking the raw materials in 3mol/L HCl solution, centrifuging the raw materials with deionized water for 5min at 8000r/min, repeatedly centrifuging the raw materials to be neutral, centrifuging the raw materials with absolute ethyl alcohol at 8000r/min for 5min for cleaning, drying the raw materials in a blast drying box at 60 ℃ for 12h, grinding the dried raw materials, and marking the dried raw materials as Fe-Nx & Co-Nx/CNCs-4 (the mass ratio of 20mg of chlorprotoporphyrin IX iron (III) to 5mg of cobalt protoporphyrin IX chloride is 4:1).
5) Catalysts RDE (rotating disk electrode) performance tests were performed in a standard three electrode electrochemical cell under acidic (0.1M HClO 4) conditions. The catalyst was used as a working electrode, a graphite rod as a counter electrode, and saturated calomel as a reference electrode in an acidic system, and the catalyst loading on the electrode provided in example 1 was 0.6mg/cm 2. All potentials in the present invention are RHE potentials. As a control, 20wt% Pt/C electrocatalyst was used, with a loading of 10 μg Pt·cm-2. The test was performed in an aqueous solution of N 2 saturated or O 2 saturated 0.1M HClO 4 at 25 ℃. The catalyst was tested for Cyclic Voltammetry (CV) curve at a positive scan rate of 50 mV.s -1. The ORR polarization curve was tested at a spin rate of 1600rpm and a positive scan rate of 10 mV.s -1. The electrochemical test conditions for the catalysts of examples 2-6 and comparative examples 1,2 were the same as in example 1.
Example 2
1) 100Mg of poly (ethylene glycol) -block-poly (propylene glycol) -block-poly (ethylene glycol) (PEG-PPG-PEG, number average molecular weight Mn at 12600 g/mol) and 40mgZnCl 2 were placed in a 250mL beaker, 50mL of deionized water and 50mL of methanol were added, and the solution was sonicated for 5min to make the solution clear and transparent, designated A.
2) Another 30.8mg KOH, 20mg of iron (III) chloroprotoporphyrin and 10mg of cobalt protoporphyrin IX chloride were placed in a 20mL sample bottle, 10mL deionized water was added and sonicated for 5min to make the solution greenish black and designated B.
3) Slowly pouring the B into the A, carrying out ultrasonic treatment for 5min, and drying at 60 ℃ in a forced air drying oven for 12h to obtain a dark green powder and film-shaped mixture.
4) Carbonizing the mixture in a tubular furnace filled with argon, wherein the carbonization procedure is as follows: heating to 800 ℃ from room temperature at a heating rate of 5 ℃/min, preserving heat for 2 hours, cooling to room temperature along with a furnace, and taking out and grinding; firstly soaking the raw materials in 3mol/L HCl solution, centrifuging the raw materials with deionized water for 5min at 8000r/min, repeatedly centrifuging the raw materials to be neutral, centrifuging the raw materials with absolute ethyl alcohol at 8000r/min for 5min for cleaning, drying the raw materials in a blast drying box at 60 ℃ for 12h, grinding the dried raw materials, and marking the dried raw materials as Fe-Nx & Co-Nx/CNCs-2 (the mass ratio of 20mg of chlorprotoporphyrin IX iron (III) to 10mg of cobalt protoporphyrin IX chloride is 2:1).
Example 3
1) 100Mg of poly (ethylene glycol) -block-poly (propylene glycol) -block-poly (ethylene glycol) (PEG-PPG-PEG, number average molecular weight Mn at 12600 g/mol) and 40mgZnCl 2 were placed in a 250mL beaker, 50mL of deionized water and 50mL of methanol were added, and the solution was sonicated for 5min to make the solution clear and transparent, designated A.
2) Another 30.8mg KOH, 20mg of iron (III) chloroprotoporphyrin and 20mg of cobalt protoporphyrin IX chloride were placed in a 20mL sample bottle, 10mL deionized water was added and sonicated for 5min to make the solution greenish black and designated B.
3) Slowly pouring the B into the A, carrying out ultrasonic treatment for 5min, and drying at 60 ℃ in a forced air drying oven for 12h to obtain a dark green powder and film-shaped mixture.
4) Carbonizing the mixture in a tubular furnace filled with argon, wherein the carbonization procedure is as follows: heating to 800 ℃ from room temperature at a heating rate of 5 ℃/min, preserving heat for 2 hours, cooling to room temperature along with a furnace, and taking out and grinding; firstly soaking the raw materials in 3mol/L HCl solution, centrifuging the raw materials with deionized water for 5min at 8000r/min, repeatedly centrifuging the raw materials to be neutral, centrifuging the raw materials with absolute ethyl alcohol at 8000r/min for 5min for cleaning, drying the raw materials in a blast drying box at 60 ℃ for 12h, grinding the dried raw materials, and marking the dried raw materials as Fe-Nx & Co-Nx/CNCs-1 (the mass ratio of 20mg of chlorprotoporphyrin IX iron (III) to 20mg of cobalt protoporphyrin IX chloride is 1:1).
Example 4
1) 100Mg of poly (ethylene glycol) -block-poly (propylene glycol) -block-poly (ethylene glycol) (PEG-PPG-PEG, number average molecular weight Mn at 12600 g/mol) and 40mgZnCl 2 were placed in a 250mL beaker, 50mL of deionized water and 50mL of methanol were added, and the solution was sonicated for 5min to make the solution clear and transparent, designated A.
2) Another 30.8mg KOH, 15mg of iron (III) chloroprotoporphyrin and 5mg of cobalt protoporphyrin IX chloride were placed in a 20mL sample bottle, 10mL deionized water was added and sonicated for 5min to make the solution greenish black and designated B.
3) Slowly pouring the B into the A, carrying out ultrasonic treatment for 5min, and drying at 60 ℃ in a forced air drying oven for 12h to obtain a dark green powder and film-shaped mixture.
4) Carbonizing the mixture in a tubular furnace filled with argon, wherein the carbonization procedure is as follows: heating to 800 ℃ from room temperature at a heating rate of 5 ℃/min, preserving heat for 2 hours, cooling to room temperature along with a furnace, and taking out and grinding; firstly soaking the raw materials in 3mol/L HCl solution, centrifuging the raw materials with deionized water for 5min at 8000r/min, repeatedly centrifuging the raw materials to be neutral, centrifuging the raw materials with absolute ethyl alcohol at 8000r/min for 5min for cleaning, drying the raw materials in a blast drying box at 60 ℃ for 12h, grinding the dried raw materials, and marking the dried raw materials as Fe-Nx & Co-Nx/CNCs-3 (the mass ratio of 15mg of chlorprotoporphyrin IX iron (III) to 5mg of cobalt protoporphyrin IX chloride is 3:1).
Example 5
1) 100Mg of poly (ethylene glycol) -block-poly (propylene glycol) -block-poly (ethylene glycol) (PEG-PPG-PEG, number average molecular weight Mn at 12600 g/mol) and 40mgZnCl 2 were placed in a 250mL beaker, 50mL of deionized water and 50mL of methanol were added, and the solution was sonicated for 5min to make the solution clear and transparent, designated A.
2) Another 30.8mg KOH, 10mg of iron (III) chloroprotoporphyrin and 10mg of cobalt protoporphyrin IX chloride were placed in a 20mL sample bottle, 10mL deionized water was added and sonicated for 5min to make the solution greenish black and designated B.
3) Slowly pouring the B into the A, carrying out ultrasonic treatment for 5min, and drying at 60 ℃ in a forced air drying oven for 12h to obtain a dark green powder and film-shaped mixture.
4) Carbonizing the mixture in a tubular furnace filled with argon, wherein the carbonization procedure is as follows: heating to 800 ℃ from room temperature at a heating rate of 5 ℃/min, preserving heat for 2 hours, cooling to room temperature along with a furnace, and taking out and grinding; firstly soaking the raw materials in 3mol/L HCl solution, centrifuging the raw materials with deionized water for 5min at 8000r/min, repeatedly centrifuging the raw materials to be neutral, centrifuging the raw materials with absolute ethyl alcohol at 8000r/min for 5min for cleaning, drying the raw materials in a blast drying box at 60 ℃ for 12h, grinding the dried raw materials, and marking the dried raw materials as Fe-Nx & Co-Nx/CNCs-1 (2) (the mass ratio of 10mg of chlorprotoporphyrin IX iron (III) to 10mg of cobalt protoporphyrin IX chloride is 1:1).
Example 6
1) 100Mg of poly (ethylene glycol) -block-poly (propylene glycol) -block-poly (ethylene glycol) (PEG-PPG-PEG, number average molecular weight Mn at 12600 g/mol) and 40mgZnCl 2 were placed in a 250mL beaker, 50mL of deionized water and 50mL of methanol were added, and the solution was sonicated for 5min to make the solution clear and transparent, designated A.
2) Another 30.8mg KOH, 5mg of iron (III) chloroprotoporphyrin and 15mg of cobalt protoporphyrin IX chloride were placed in a 20mL sample bottle, 10mL deionized water was added and sonicated for 5min to make the solution greenish black and designated B.
3) Slowly pouring the B into the A, carrying out ultrasonic treatment for 5min, and drying at 60 ℃ in a forced air drying oven for 12h to obtain a dark green powder and film-shaped mixture.
4) Carbonizing the mixture in a tubular furnace filled with argon, wherein the carbonization procedure is as follows: heating to 800 ℃ from room temperature at a heating rate of 5 ℃/min, preserving heat for 2 hours, cooling to room temperature along with a furnace, and taking out and grinding; firstly soaking the raw materials in 3mol/L HCl solution, centrifuging the raw materials with deionized water for 5min at 8000r/min, repeatedly centrifuging the raw materials to be neutral, centrifuging the raw materials with absolute ethyl alcohol at 8000r/min for 5min for cleaning, drying the raw materials in a blast drying box at 60 ℃ for 12h, grinding the dried raw materials, and marking the dried raw materials as Fe-Nx & Co-Nx/CNCs-1/3 (the mass ratio of 5mg of chlorprotoporphyrin IX iron (III) to 15 mg of cobalt protoporphyrin IX is 1:3).
Comparative example 1
1) 100Mg of poly (ethylene glycol) -block-poly (propylene glycol) -block-poly (ethylene glycol) (PEG-PPG-PEG, number average molecular weight Mn at 12600 g/mol) and 40mg of ZnCl2 were placed in a 250mL beaker, 50mL of deionized water and 50mL of methanol were added, and the solution was sonicated for 5min to make the solution clear and transparent, designated A.
2) Another 30.8mg KOH, chloroprotoporphyrin IX iron (III) 20mg in a 20mL sample bottle was added with 10mL deionized water and sonicated for 5min to make the solution greenish black, designated B.
3) Slowly pouring the B into the A, carrying out ultrasonic treatment for 5min, and drying at 60 ℃ in a forced air drying oven for 12h to obtain a dark green powder and film-shaped mixture.
4) Carbonizing the mixture in a tubular furnace filled with argon, wherein the carbonization procedure is as follows: heating to 800 ℃ from room temperature at a heating rate of 5 ℃/min, preserving heat for 2 hours, cooling to room temperature along with a furnace, and taking out and grinding; firstly soaking the raw materials in 3mol/L HCl solution, centrifuging the raw materials with deionized water for 5min at 8000r/min, repeatedly centrifuging the raw materials to be neutral, then centrifuging the raw materials with absolute ethyl alcohol for 5min at 8000r/min for cleaning, drying the raw materials in a blast drying box at 60 ℃ for 12h, grinding the dried raw materials, and marking the dried raw materials as Fe-Nx/CNCs (chloroprotoporphyrin IX iron (III) 20 mg).
Comparative example 2
1) 100Mg of poly (ethylene glycol) -block-poly (propylene glycol) -block-poly (ethylene glycol) (PEG-PPG-PEG, number average molecular weight Mn at 12600 g/mol) and 40mg of ZnCl2 were placed in a 250mL beaker, 50mL of deionized water and 50mL of methanol were added, and the solution was sonicated for 5min to make the solution clear and transparent, designated A.
2) Another 30.8mg KOH, cobalt chloride protoporphyrin IX (III) 20mg in a 20mL sample bottle was added with 10mL deionized water and sonicated for 5min to make the solution greenish black, designated B.
3) Slowly pouring the B into the A, carrying out ultrasonic treatment for 5min, and drying at 60 ℃ in a forced air drying oven for 12h to obtain a dark green powder and film-shaped mixture.
4) Carbonizing the mixture in a tubular furnace filled with argon, wherein the carbonization procedure is as follows: heating to 800 ℃ from room temperature at a heating rate of 5 ℃/min, preserving heat for 2 hours, cooling to room temperature along with a furnace, and taking out and grinding; firstly soaking the raw materials in 3mol/L HCl solution, centrifuging the raw materials with deionized water for 5min at 8000r/min, repeatedly centrifuging the raw materials to be neutral, then centrifuging the raw materials with absolute ethyl alcohol for 5min at 8000r/min for cleaning, drying the raw materials in a blast drying box at 60 ℃ for 12h, grinding the dried raw materials, and marking the dried raw materials as Co-Nx/CNCs (cobalt chloride protoporphyrin IX20 mg).
Effect example: in order to explore the morphological characteristics and electrochemical performances of the prepared bimetallic-nitrogen-carbon electrocatalyst, SEM, XRD, XPS, raman and other means are used for carrying out physical characterization on the prepared product, and the product is prepared into an electrode to test the corresponding electrochemical performances.
In FIG. 1 (a), SEM photograph (scale is 400 nm) of the Fe-Nx & Co-Nx/CNCs-4 catalyst prepared in example 1, and as can be seen from the SEM photograph in FIG. 1 (a), the Fe-Nx & Co-Nx/CNCs-4 has a hollow olive-shaped morphology with more defects; in FIG. 1 (b), SEM photograph (scale is 4 μm) of the Fe-Nx & Co-Nx/CNCs-4 catalyst prepared in example 1, and in FIG. 1 (b), it can be seen that the Fe-Nx & Co-Nx/CNCs-4 morphology is formed by stacking hollow olives having more defects.
FIG. 2 (a) is an XRD spectrum of the electrocatalyst of Fe-Nx & Co-Nx/CNCs-4 prepared in example 1 and Fe-Nx/CNCs prepared in comparative example 1, wherein the peak positions of example 1 and comparative example 1 are the same, and after carbonization treatment at 800 ℃, there is no metal diffraction peak, and the morphology is changed only, which indicates that the metal may be embedded into the carbon support or dispersed in the carbon support in an atomic scale. FIG. 2 (b) is a Raman spectrum of an electrocatalyst of Fe-Nx & Co-Nx/CNCs-4 prepared in example 1 and Fe-Nx/CNCs prepared in comparative example 1. The D peak appears at 1350cm -1 and the G peak appears at 1580cm -1. The defect degree and graphitization degree of the sample can be judged from the D peak and the G peak. The Raman spectra of Fe-Nx & Co-Nx/CNCs-4 and Fe-Nx/CNCs are shown in the figures, the ratio of I D to I G is 0.99 and 1.02 respectively, the graphitization degree of Fe-Nx & Co-Nx/CNCs-4 is better than that of Fe-Nx/CNCs, and the introduction of metallic cobalt can drive the metallic cobalt to convert to graphitization transformation catalytic part carbon cages to graphitization degree.
FIG. 3 (a) to (b) show XPS full spectrum and N1s spectrum of the Fe-Nx & Co-Nx/CNCs-4 electrocatalyst prepared in example 1. From FIG. 3 (a), the presence of Fe, co and N elements is clearly observed, and FIG. 3 (b) shows a high resolution N1s spectrum from which it is possible to obtain the presence of nitrogen in the form of Fe-N, co-N, graphite nitrogen, pyrrole nitrogen, pyridine nitrogen and small amounts of nitrogen oxides, respectively.
FIG. 4 (a) is a graph showing the adsorption and desorption curves of nitrogen for the electrocatalyst Fe-Nx & Co-Nx/CNCs-4 prepared in example 1. The total specific surface area of Fe-Nx & Co-Nx/CNCs-4 is 1108m 2·g-1. Wherein (b) in FIG. 4 is the pore size distribution curve of the Fe-Nx & Co-Nx/CNCs-4 electrocatalyst prepared in example 1. The pore diameters of the samples are concentrated at 20-100nm and are mesoporous.
FIG. 5 (a) is a polarization curve of 1600rpm under acidic conditions for the bimetallic-nitrogen-carbon electrocatalysts prepared in examples 1-3 and the monometal-nitrogen-carbon electrocatalyst prepared in comparative example 1 of the present invention; as can be seen from fig. 5 (a), in the polarization curve of 1600rpm of the electrocatalyst material for which the mass ratio of cobalt is adjusted when the mass ratio of iron is 20wt% in the 0.1M HClO 4 aqueous solution, as the mass ratio of cobalt increases, the electrochemical properties increase and decrease, and Fe-Nx & Co-Nx/CNCs-4 shows the optimal properties: very good starting potential and half-wave potential. FIG. 5 (b) is a polarization curve of 1600rpm under acidic conditions for the bimetallic-nitrogen-carbon electrocatalysts prepared in examples 4-6 of the invention and the monometal-nitrogen-carbon electrocatalysts prepared in comparative examples 1-2; as can be seen from fig. 5 (b), in the polarization curve of 1600rpm of the electrocatalyst material, which adjusts the mass ratio of iron to cobalt when the total mass ratio of iron to cobalt is guaranteed to be 20wt%, in the 0.1M HClO 4 aqueous solution, the electrochemical performance monotonically decreases as the mass ratio of iron to cobalt decreases, and the Fe-Nx/CNCs exhibits the optimal performance: very good starting potential and half-wave potential.
FIG. 6 (a) is a cyclic voltammogram (nitrogen and oxygen) of the Fe-Nx & Co-Nx/CNCs-4 electrocatalyst prepared according to example 1 of the invention under acidic conditions, wherein example 1 has a distinct oxygen reduction peak in an oxygen saturated aqueous 0.1M HClO 4, example 1 is between 0.6 and 0.8V; FIG. 6 (b) is a polarization curve of 1600rpm under acidic conditions for the single metal-nitrogen-carbon electrocatalysts prepared in example 1, comparative example 2 and commercial 20wt% Pt/C according to the invention, where Fe-Nx & Co-Nx/CNCs-4 is most preferred, and half-wave potential can reach 0.823V.
FIG. 7 (a) is a polarization curve change during a durability test under acidic conditions of 20wt% Pt/C, the half-wave potential and the initial potential of which show decreasing trend, and after 3000 cycles of durability test, the half-wave potential of 20wt% Pt/C decays by 40mV; FIG. 7 (b) shows the polarization curve change during the durability test of the Fe-Nx & Co-Nx/CNCs-4 prepared in example 1 of the present invention under acidic conditions, the half-wave potential and the initial potential thereof show decreasing trend, and after 3000 circles of durability test, the half-wave potential of the Fe-Nx & Co-Nx/CNCs-4 is attenuated by 21mV.
Claims (10)
1. A method for improving durability of a metal-nitrogen-carbon electrocatalyst, comprising: the method comprises the following steps:
(1) Mixing PEG-PPG-PEG and zinc chloride, adding a mixed solvent, and after ultrasonic treatment for 1-30 min, marking as A; adding water into potassium hydroxide, chlorine protoporphyrin IX iron (III) and cobalt chloride protoporphyrin IX, and performing ultrasonic treatment for 1-30 min to obtain B; pouring the B into the A, and drying in a blast drying box at 50-100 ℃ for 1-12 h to obtain a mixture;
(2) Carbonizing the mixture under the argon condition, and washing, drying and grinding the obtained product to obtain the bimetallic-nitrogen-carbon electrocatalyst;
Wherein the mixed solvent is formed by mixing water and an organic solvent; the ratio of the PEG-PPG-PEG to the organic solvent to the water is 1-1000mg: 1-100 mL: 1-100 mL; PEG-PPG-PEG, zinc chloride, potassium hydroxide, chlorine protoporphyrin IX iron (III), cobalt chloride protoporphyrin IX 1-1000mg: 1-500 mg: 1-500 mg: 1-500 mg: 1-500 mg.
2. The method according to claim 1, characterized in that: the organic solvent is formed by mixing two of methanol, ethanol, isopropanol, dimethylformamide or diethylene glycol dimethyl ether.
3. The method according to claim 1, characterized in that: the volume ratio of the organic solvent to the organic solvent is 1:1.
4. The method according to claim 1, characterized in that: the number average molecular weight Mn of the PEG-PPG-PEG is 1000-60000 g/mol.
5. The method according to claim 1, characterized in that: in the step (2), the carbonization conditions are as follows: under argon atmosphere, the temperature is raised to 400-1000 ℃ at a heating rate of 1-10 ℃/min, the temperature is kept for 1-6 h, and then the furnace is cooled to room temperature.
6. The method according to claim 1, characterized in that: in step (2), the washing is: the obtained product is soaked in 1-8 mol/L hydrochloric acid solution for 1-12 h, and then is centrifuged to be neutral by deionized water and then is centrifuged by absolute ethyl alcohol.
7. The method according to claim 6, wherein: the centrifugation conditions are as follows: centrifuging for 2-10 min at 5000-10000 r/min.
8. A bimetallic-nitrogen-carbon electrocatalyst prepared by the process of any one of claims 1 to 7.
9. The bimetallic-nitrogen-carbon electrocatalyst according to claim 8, wherein: the hollow olive-shaped structure with defects has a specific surface area of 100-3000 m 2·g-1.
10. Use of the bimetallic-nitrogen-carbon electrocatalyst according to claim 8 or 9 as a fuel cell cathode electrocatalyst material and catalyst support material.
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