CN109473686B - Catalyst taking biomass cotton as carbon base and preparation method and application thereof - Google Patents
Catalyst taking biomass cotton as carbon base and preparation method and application thereof Download PDFInfo
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- CN109473686B CN109473686B CN201811605493.6A CN201811605493A CN109473686B CN 109473686 B CN109473686 B CN 109473686B CN 201811605493 A CN201811605493 A CN 201811605493A CN 109473686 B CN109473686 B CN 109473686B
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- 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
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- 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
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Abstract
The embodiment of the invention relates to a catalyst taking biomass cotton as a carbon base, a preparation method and application thereof, wherein cotton, metal salt and a nitrogen source are used as raw materials to form an M-N-C active site, wherein the cotton is doped with the metal salt and the nitrogen source and subjected to ammonia gas etching pore-forming treatment at high temperature to obtain a micron rod structure attached with nano metal particle nano pores. The catalyst has high-efficiency and stable ORR catalytic activity and low production cost, is applied to metal air batteries, reduces the battery cost and improves the battery performance.
Description
Technical Field
The invention relates to the technical field of metal-air batteries, in particular to a catalyst taking biomass cotton as a carbon base, and a preparation method and application thereof.
Background
The metal-air battery is an electrochemical reaction device and consists of a metal anode, an air cathode and an electrolyte solution. The metal anode usually uses metal materials with negative electrode potential, such as magnesium, aluminum, zinc, cadmium, iron and the like, and the metal anode is used as fuel, so that the product is clean and pollution-free, and the price is relatively low. The electrolyte solution is alkali liquor or neutral salt water solution. The air cathode is generally composed of a hydrophobic layer, a current collecting layer and a catalytic active layer, and oxygen in air directly utilized is used as an oxidant. The price of the air cathode often determines the cost of the cell, a relatively inexpensive fuel. However, in air cathodes, the cathode Oxygen Reduction Reaction (ORR) catalyst is critical and often determines cell performance. Therefore, the preparation of the cathode ORR catalyst which is cheap, environment-friendly and excellent in performance is very important. Currently, the commercial ORR catalyst is Pt/C catalyst, but the noble metal Pt is expensive, so that it cannot be popularized. In metal-air batteries, in order to meet the requirement of being capable of being used in large quantities without being too expensive, many researchers use Mn-based catalysts, however, when the Mn-based catalysts are used, the ORR catalytic performance of the Mn-based catalysts is lower, and the Mn-based catalysts are far lower than that of commercial Pt/C catalysts, so that the battery performance is limited.
For example, CN103877972 discloses a method for increasing MnOXMethod of preparing catalyst by reaction with MnOXThe electrochemical treatment is carried out to increase the content of Mn (IV) in the catalyst so as to improve the ORR performance of the catalyst, however, the performance of the catalyst has a certain difference from the Pt/C no matter the peak potential or the half-wave potential. CN103682381 discloses a nano or micro LaNiO3Catalyst and MnO2The composite catalyst of the catalyst has low price, simple preparation and industrial amplification, and the ORR catalytic performance is as follows: the half-wave potential is about-0.3V relative to Hg/HgO, far less than commercial Pt/C. Therefore, in the research of the ORR catalyst, the cost is low, the ORR catalyst can be industrially prepared in an enlarged way, and the ORR catalyst has excellent performance, which is very important.
Although the active sites of ORR catalysts are not well known, the non-noble metal doped composite material of non-noble metal M-N-C system is considered as the most promising ORR catalyst material, and such catalysts mainly form the active sites of M-N structure and have good catalytic activity. CN105375042 discloses a biomass carbon-based catalyst, wherein biomass and metal salt are used as raw materials in a biomass carbon-based catalyst, in the process of metal improvement, the composition and reaction temperature of precursor mixed liquor are adjusted by controlling the addition of different amounts of metal salt, and the biomass carbon-based catalyst with controllable and adjustable pore structure and specific surface area is prepared at a carbonitriding treatment temperature. However, the technology of this patent does not have direct addition of nitrogen source, which is weak in forming M-N-C active site, so that there is still a certain difference in performance, whether in peak potential or half-wave potential, from Pt/C or similar to the catalytic activity of commercial Pt/C catalyst. Hard straw is used as carbon-based raw material in the patent, the pretreatment of the raw material is more complicated, the effect of soaking and absorbing solution is poor, the solution stays on the macroscopic surface more, the doping effect is poor, and the final catalytic activity is influenced. Based on the method, common cheap cotton is mainly selected as a carbon material, and the efficient and stable ORR catalyst is prepared by doping transition metal salt and nitrogen source and microwave synthesis.
Disclosure of Invention
In order to solve the problems in the prior art, the invention aims to provide a catalyst taking biomass cotton as carbon base, which has high-efficiency and stable ORR catalytic activity and low production cost, is applied to a metal air battery, reduces the battery cost and improves the battery performance.
The invention also aims to provide a preparation method of the catalyst taking biomass cotton as carbon base, which is simple to operate and suitable for industrial scale-up production.
The invention is realized by the following technical scheme:
a catalyst taking biomass cotton as a carbon base is an M-N-C active site formed by taking cotton, metal salt and a nitrogen source as raw materials, and has a micron rod structure with nanopores, and metal nanoparticles are attached to the nanopores.
Preferably, the catalyst using biomass cotton as carbon base is prepared by forming M-N-C active sites by using cotton, metal salt and nitrogen source as raw materials, wherein the cotton is doped with the metal salt and the nitrogen source and subjected to ammonia gas etching pore-forming treatment at high temperature to obtain the micron rod structure attached with nano metal particle nano pores.
In the catalyst, the mass ratio of the cotton, the metal salt and the nitrogen source is 1: (0.1-100): (0.1-100). Preferably, the mass ratio of the cotton, the metal salt and the nitrogen source is 1: (0.1-10): (0.1-10). More preferably, the mass ratio of the cotton, the metal salt and the nitrogen source is 1: (0.1-5): (0.1-5).
The cotton of the invention is in a micron rod-shaped structure, and is shown in figure 1.
The M is metal.
The metal salt is iron group salt and cobalt group salt, and is preferably one or more of ferric chloride, ferric nitrate, heme and cobalt chloride, cobalt nitrate or cobalt acetate; more preferably, the metal salt is prepared by mixing an iron group and a cobalt group according to a mass ratio of (1-3): (3-1).
The nitrogen source includes, but is not limited to, high molecular polymer, nitrogen-containing salt, nitrogen-containing gas, preferably one or more of poly (m-phenylenediamine), hydroxylamine chloride, melamine, urea and ammonia gas. Preferably, the nitrogen source is a mixture of a high molecular polymer and a nitrogen-containing salt in a mass ratio of (1-5): (5-1).
The inert gas in the present invention includes, but is not limited to, nitrogen, argon, helium. Nitrogen is preferred.
According to the invention, under the condition that cotton, metal salt and a nitrogen source are mutually added in a specific proportion, a metal source and a nitrogen source are more doped at high temperature, so that a synergistic effect is achieved, and the formation of M-N-C active sites is facilitated. The introduction of ammonia gas can increase active sites for pore-forming of the material, and has the double effect of nitrogen doping, thereby obtaining the cheap M-N-C system catalyst material.
The invention relates to a preparation method of a catalyst taking biomass cotton as a carbon base, which comprises the steps of taking cotton as a carrier and a carbon source, doping a nitrogen source, doping metal salt as a non-noble metal source, and carrying out high-temperature carbonization and ammonia pore-forming treatment in an inert atmosphere to obtain a catalyst material of an M-N-C system.
The invention relates to a preparation method of a catalyst taking biomass cotton as carbon base, which comprises the following steps:
(1) mixing cotton with solvent under stirring, heating, cooling, taking out cotton, and drying;
(2) weighing metal salt and nitrogen source to prepare a uniform mixed solution for later use;
(3) soaking the cotton dried in the step (1) into the mixed solution in the step (2), and freeze-drying;
(4) calcining the cotton freeze-dried in the step (3) in an inert atmosphere, introducing ammonia gas, and cooling after the reaction is finished;
(5) ball-milling the product obtained in the step (4), adding strong acid for pickling, drying and cooling;
(6) washing the product after acid washing in the step (5) to be neutral, and drying;
(7) and (4) taking out the product obtained in the step (6), carrying out secondary calcination in an inert atmosphere, and cooling to obtain the catalyst.
The solvent in the step (1) of the invention is one or more of deionized water, ethanol, isopropanol and glycol. Preferably, the solvent is a mixed solution of water and ethanol, and the volume ratio of the mixed solution is 1:2-2:1, preferably 1: 1. The dosage of the cotton and the solvent is 1g of cotton/5-30 ml of solvent.
In the step (1), the heating is carried out at the temperature of 80-100 ℃ for 1-36 hours. Preferably, the heating is carried out at 80-100 ℃ for 1-5 hours.
Preparing a metal salt and a nitrogen source in the step (2), wherein the metal salt is an iron group salt, a cobalt group salt and the like, and preferably one or more of ferric chloride, ferric nitrate, heme, cobalt chloride, cobalt nitrate and cobalt acetate; the nitrogen source is high molecular polymer, nitrogen-containing salt and nitrogen-containing gas, preferably one or more of poly (m-phenylenediamine), hydroxylamine chloride, melamine, urea and ammonia gas.
The step (3) of the invention is frozen and vacuum dried for 24 to 96 hours; freeze drying does not damage the material structure, keeps shape stable, can solidify more solution absorbed in the cotton on the surface, and is beneficial to full combination during carbonization. And the conventional drying method has no such advantage.
The inert atmosphere in step (4) of the present invention includes, but is not limited to, nitrogen, argon, helium, preferably nitrogen. The inert gas selected by the invention can prevent oxygen from entering and reacting the material during high-temperature carbonization.
The calcination in step (4) of the invention is preferably carried out in a microwave oven for 10-60 minutes and then the calcination is carried out at 800-1600 ℃ for 0.1-8 hours, wherein after the ammonia gas introduced at 400-600 ℃ for 5-60 minutes is reacted, the reaction is cooled. The microwave oven has the characteristic of rapid temperature rise, is beneficial to the formation of defect points and is more beneficial to the formation of catalytic active sites; the introduction of ammonia gas at high temperature can increase the active sites for the pore-forming of the material and also has the double effect of nitrogen doping, thereby obtaining the cheap M-N-C system catalyst material.
The strong acid in the step (5) of the invention is one or more of nitric acid, hydrochloric acid or sulfuric acid. Acid washing is performed to remove excess inactive metal not participating in the active site.
The calcination in the step (7) of the present invention means secondary calcination at 500-1600 ℃ for 0.1-8 hours in a tubular furnace. The secondary calcination can reform the active sites due to the active site damage during the acid wash.
The drying in the steps (1), (5) to (6) of the invention is carried out in an oven at 60-100 ℃.
Further preferably, the preparation method of the catalyst taking biomass cotton as carbon base comprises the following steps:
(1) placing cotton into a closed container filled with 5-30 times of a mixed solution of deionized water and ethanol with the volume ratio of 1:2-2:1, heating in an oven at 80-100 ℃ for 1-5 hours, cooling to room temperature, taking out the cotton, and drying in the oven;
(2) weighing more than two metal salts and a nitrogen source to prepare a uniform mixed solution;
(3) weighing the dried cotton in the step (1), soaking the cotton into the mixed solution in the step (2), and then putting the cotton into a freeze dryer for freeze vacuum drying for 36-72 hours;
(4) putting the cotton freeze-dried in the step (3) into a porcelain boat, heating the cotton in a microwave oven for 20-40 minutes in an inert atmosphere to be calcined at the temperature of 1000-1200 ℃ for 0.1-1 hour, introducing ammonia gas for 5-30 minutes at the temperature of 400-600 ℃, and then cooling to room temperature;
(5) taking the product in the step (4) out of the microwave oven, carrying out ball milling for 5-60 minutes, adding strong acid for pickling, putting the product into an oven, drying the product for 1-24 hours at the temperature of 60-100 ℃, and then cooling the product to room temperature;
(6) centrifugally cleaning the product after acid washing in the step (5) for 3-6 times by using deionized water until the product is neutral, and then drying the product in an oven at 60-100 ℃;
(7) taking out the dried product in the step (6), putting the product into a porcelain boat again, carrying out secondary calcination for 0.1-1 h at the temperature of 500-1000 ℃ in a tube furnace in an inert atmosphere, and then cooling to room temperature;
(8) and (5) taking out the product in the step (7) to obtain the catalyst of the invention.
Further preferably, the preparation method of the catalyst taking biomass cotton as carbon base comprises the following steps:
(1) taking 24 parts of cotton, and putting the cotton into a container containing the components in a volume ratio of 1:1, heating the mixture of deionized water and ethanol in a closed container at 100 ℃ for 2 hours, cooling to room temperature, taking out the cotton, and drying in an oven;
(2) weighing 5.4 parts of ferric chloride, 3.1 parts of cobalt chloride, 1.2 parts of poly-m-phenylenediamine and 3.4 parts of hydroxylamine chloride to prepare a uniform mixed solution;
(3) weighing the dried cotton in the step (1), soaking the cotton into the mixed solution in the step (2), and then putting the cotton into a freeze dryer for freeze vacuum drying for 48 hours;
(4) putting the cotton freeze-dried in the step (3) into a porcelain boat, heating the cotton in a microwave oven for 30 minutes in an inert nitrogen atmosphere to be calcined at 1200 ℃ for 0.5 hour, introducing ammonia gas for 5 minutes at 500 ℃, and then cooling the cotton to room temperature;
(5) taking the product in the step (4) out of the tube furnace, carrying out ball milling for 30 minutes, adding strong acid for pickling, putting the product into an oven, drying the product for 6 hours at the temperature of 80 ℃, and then cooling the product to room temperature;
(6) centrifugally cleaning the product after acid washing in the step (5) for 3 times by using deionized water until the product is neutral, and then drying the product in an oven at 80 ℃;
(7) taking out the dried product in the step (6), putting the dried product into a porcelain boat again, carrying out secondary calcination for 0.5 hour at 900 ℃ in a tube furnace in an inert atmosphere, and then cooling to room temperature;
(8) and (5) taking out the product in the step (7) to obtain the catalyst of the invention.
The invention also provides a cathode of a metal-air battery, which comprises the catalyst, and the metal-air battery comprises but is not limited to an aluminum-air battery, a magnesium-air battery and a zinc-air battery.
Advantageous effects
1. The invention provides a method for preparing a cheap, efficient and stable oxygen reduction catalyst by using common biomass cotton as a raw material and doping metal salt and a nitrogen source in a simple and rapid manner, aiming at overcoming the defects of high preparation cost, low catalytic activity, poor stability and the like of the cathode oxygen reduction catalyst of the existing metal-air battery, and being applied to the metal-air battery, so that the battery cost is reduced and the battery performance is improved.
2. The invention has the advantages of low price of raw materials, wide sources, simple preparation method, short reaction time and convenient operation. The raw materials are soft, the effect of soaking and absorbing the solution is good, the solution absorbed in the cotton can be more solidified on the surface, and the effect of doping metal and nitrogen source is good; the metal salt used is low in toxicity and risk and very environment-friendly; the obtained product has the characteristics of low cost, high catalytic activity, good stability and the like.
3. The structure of the raw material cotton used by the invention is a smooth micron rod-shaped structure (figure 1), and the micron rod-shaped structure with countless nanopores (figure 2) is obtained by doping multi-metal salt and a nitrogen source and then performing ammonia etching pore-forming treatment at high temperature. The nano holes provide more active sites for the catalyst, and attach nano metal particles to form more M-N active sites, countless nano-structure small holes are etched on the rod-shaped cotton and attach a plurality of metal nano particles to form M-N-C active sites, and the M-N-C structure composite material catalyst has higher ORR catalytic activity. Wherein the biomass is cotton which is cheap and easy to obtain; metal sources and nitrogen sources are doped more, so that a synergistic effect is achieved; the ammonia gas has the double effects of pore forming and nitrogen doping; the microwave oven has the characteristic of rapid temperature rise, is beneficial to the formation of defect points and is easy to form catalytic active sites; acid washing is carried out to remove redundant ineffective metals which do not participate in active sites; the secondary calcination is to reform the active sites.
4. The catalyst provided by the invention is applied to a metal-air battery, so that the power density of the battery is greatly improved. In particular, in the first test example, the oxygen reduction catalyst prepared by using cotton as a raw material has very high half-wave potential which reaches 0.893V and is 25mV higher than that of a commercial Pt/C catalyst (0.868V); the limiting current is slightly higher than Pt/C; meanwhile, through a 24000s stability i-t test, the limiting current is only attenuated by 17.4%, and is far more stable than a Pt/C catalyst (attenuated by 45.6%) under the same condition. In addition, the power density of a metal-air battery prepared by the catalyst is up to 286mW/cm under the 1V state2Is superior to the prior common MnO2Cell performance of catalyst Assembly prepared for feedstock (228 mW/cm)2). The direct utilization of the common cheap articles in the marketThe method for preparing the catalyst provides a novel idea for preparing the cathode catalyst of the battery.
Description of the drawings:
FIG. 1 is a scanning electron micrograph of the cotton structure, which shows the cotton structure in the form of a micron rod;
FIG. 2 is a scanning electron microscope image of a catalyst prepared from a cotton raw material, wherein innumerable nano-structured pores are etched on a rod-shaped cotton and a plurality of metal nano-particles are attached;
FIG. 3 is a graph comparing the electrocatalytic activity of the prepared cotton and commercial Pt/C catalysts. It can be seen that the catalytic activity of the prepared catalyst is higher than that of commercial Pt/C;
FIG. 4 is a graph of stability tests of the prepared cotton and commercial Pt/C catalysts. It can be seen that the prepared catalyst has much higher stability than Pt/C;
FIG. 5 shows the prepared cotton catalyst, and MnO2Polarization curve of catalyst after assembling aluminum-air cell. It can be seen that the power density of the prepared cotton catalyst in the 1V state is far higher than that of MnO after the prepared cotton catalyst is assembled into an aluminum-air battery2The power density of (a).
Detailed Description
In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention are clearly and completely described below, and it is obvious that the described embodiments are a part of the embodiments of the present invention, but not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention. Throughout the specification and claims, unless explicitly stated otherwise, the word "comprise", or variations such as "comprises" or "comprising", will be understood to imply the inclusion of a stated element or component but not the exclusion of any other element or component.
Example 1
(1) Taking 24g of cotton, putting the cotton into a closed container filled with a mixed solution of deionized water and ethanol (the ratio is 1: 1), heating the cotton in an oven at 100 ℃ for 2 hours, cooling the cotton to room temperature, taking out the cotton, and drying the cotton in the oven;
(2) weighing 5.4g of ferric chloride, 3.1g of cobalt chloride, 1.2g of poly-m-phenylenediamine and 3.4g of hydroxylamine chloride to prepare a uniform mixed solution;
(3) weighing the dried cotton in the step (1), soaking the cotton into the mixed solution in the step (2), and then putting the cotton into a freeze dryer for freeze vacuum drying for 48 hours;
(4) putting the cotton freeze-dried in the step (3) into a porcelain boat and adding the porcelain boat into inert N2Calcining at 1200 deg.C for 0.5 hr in a microwave oven for 30 min in gas atmosphere, introducing 5 min ammonia gas at 500 deg.C, and cooling to room temperature;
(5) taking the product in the step (4) out of the tube furnace, carrying out ball milling for 30 minutes, adding strong acid for pickling, putting the product into an oven, drying the product for 6 hours at the temperature of 80 ℃, and then cooling the product to room temperature;
(6) centrifugally cleaning the product after acid washing in the step (5) for 3 times by using deionized water until the product is neutral, and then drying the product in an oven at 80 ℃;
(7) taking out the dried product in the step (6), putting the dried product into a porcelain boat again, carrying out secondary calcination for 0.5 hour at 900 ℃ in a tube furnace in an inert atmosphere, and then cooling to room temperature;
(8) taking out the product in the step (7) to obtain the catalyst of the invention;
(9) and (3) using the catalyst in the step (8) for preparing an air cathode, assembling the air cathode into an aluminum air battery, and introducing 4M KOH solution for battery performance test.
Example 2
(1) Taking 24g of cotton, putting the cotton into a closed container (the ratio is 1: 1) filled with 10 times of deionized water and ethanol mixed solution, heating the cotton in an oven at 80 ℃ for 5 hours, taking out the cotton after cooling to room temperature, and putting the cotton into the oven for drying;
(2) weighing 5.4g of ferric chloride, 3.1g of cobalt chloride, 1.2g of poly-m-phenylenediamine and 3.4g of hydroxylamine chloride to prepare a uniform mixed solution;
(3) weighing the dried cotton in the step (1), soaking the cotton into the mixed solution in the step (2), and then putting the cotton into a freeze dryer for freeze vacuum drying for 36 hours;
(4) putting the cotton freeze-dried in the step (3) into a porcelain boat, heating the cotton in a microwave oven for 20 minutes in an inert argon atmosphere to be calcined for 1 hour at 1000 ℃, introducing 10 minutes of ammonia gas at 400 ℃, and then cooling the cotton to room temperature;
(5) taking the product in the step (4) out of the tube furnace, carrying out ball milling for 20 minutes, adding strong acid for pickling, putting the product into an oven, drying the product for 10 hours at the temperature of 60 ℃, and then cooling the product to room temperature;
(6) centrifugally cleaning the product after acid washing in the step (5) for 4 times by using deionized water until the product is neutral, and then drying the product in an oven at 60 ℃;
(7) taking out the dried product in the step (6), putting the dried product into a porcelain boat again, carrying out secondary calcination for 1 hour at 500 ℃ in a tube furnace in an inert atmosphere, and then cooling to room temperature;
(8) and (5) taking out the product in the step (7) to obtain the catalyst of the invention.
Example 3
(1) Taking 24g of cotton, putting the cotton into a 5-time (ratio is 2: 1) closed container filled with a deionized water and ethanol mixed solution, heating the cotton in an oven at 100 ℃ for 2 hours, taking out the cotton after cooling to room temperature, and putting the cotton into the oven for drying;
(2) weighing 5.4g of ferric chloride, 3.1g of cobalt chloride, 1.2g of poly-m-phenylenediamine and 3.4g of hydroxylamine chloride to prepare a uniform mixed solution;
(3) weighing the dried cotton in the step (1), soaking the cotton into the mixed solution in the step (2), and then putting the cotton into a freeze dryer for freeze vacuum drying for 72 hours;
(4) putting the cotton freeze-dried in the step (3) into a porcelain boat, heating to 1200 ℃ in a microwave oven for 40 minutes in an inert N2 gas atmosphere, calcining for 0.1 hour, introducing 5 minutes of ammonia gas at 600 ℃, and then cooling to room temperature;
(5) taking the product in the step (4) out of the tube furnace, carrying out ball milling for 40 minutes, adding strong acid for pickling, putting the product into an oven, drying the product for 1 hour at 100 ℃, and then cooling the product to room temperature;
(6) centrifugally cleaning the product after acid washing in the step (5) for 3 times by using deionized water until the product is neutral, and then drying the product in an oven at 100 ℃;
(7) taking out the dried product in the step (6), putting the dried product into a porcelain boat again, carrying out secondary calcination in a tube furnace at 1000 ℃ for 0.1 hour in an inert atmosphere, and then cooling to room temperature;
(8) and (5) taking out the product in the step (7) to obtain the catalyst of the invention.
Example 4
(1) Taking 16g of cotton, putting the cotton into a closed container filled with 30 times of deionized water and ethanol mixed solution (the ratio is 1: 1), heating the cotton in an oven at 100 ℃ for 2 hours, taking out the cotton after cooling to room temperature, and putting the cotton into the oven for drying;
(2) weighing 5g of ferric chloride, 5g of cobalt chloride, 3g of poly (m-phenylenediamine) and 3g of hydroxylamine chloride, and preparing into a uniform mixed solution;
(3) weighing the dried cotton in the step (1), soaking the cotton into the mixed solution in the step (2), and then putting the cotton into a freeze dryer for freeze vacuum drying for 48 hours;
(4) putting the cotton freeze-dried in the step (3) into a porcelain boat, heating to 1200 ℃ in a microwave oven for 30 minutes in an inert N2 gas atmosphere, calcining for 0.5 hour, introducing 5 minutes of ammonia gas at 500 ℃, and then cooling to room temperature;
(5) taking the product in the step (4) out of the tube furnace, carrying out ball milling for 30 minutes, adding strong acid for pickling, putting the product into an oven, drying the product for 6 hours at the temperature of 80 ℃, and then cooling the product to room temperature;
(6) centrifugally cleaning the product after acid washing in the step (5) for 3 times by using deionized water until the product is neutral, and then drying the product in an oven at 80 ℃;
(7) taking out the dried product in the step (6), putting the dried product into a porcelain boat again, carrying out secondary calcination for 0.5 hour at 900 ℃ in a tube furnace in an inert atmosphere, and then cooling to room temperature;
(8) and (5) taking out the product in the step (7) to obtain the catalyst of the invention.
Example 5
(1) Taking 2.8g of cotton, putting the cotton into a closed container filled with 5 times of deionized water and ethanol mixed solution (the ratio is 1: 1), heating the cotton in an oven at 100 ℃ for 2 hours, taking out the cotton after cooling to room temperature, and putting the cotton into the oven for drying;
(2) weighing 6g of ferric nitrate, 2g of cobalt nitrate, 1g of melamine and 5g of urea to prepare a uniform mixed solution; (3) weighing the dried cotton in the step (1), soaking the cotton into the mixed solution in the step (2), and then putting the cotton into a freeze dryer for freeze vacuum drying for 48 hours;
(4) putting the cotton freeze-dried in the step (3) into a porcelain boat, heating to 1200 ℃ in a microwave oven for 30 minutes in an inert N2 gas atmosphere, calcining for 0.5 hour, introducing 5 minutes of ammonia gas at 500 ℃, and then cooling to room temperature;
(5) taking the product in the step (4) out of the tube furnace, carrying out ball milling for 30 minutes, adding strong acid for pickling, putting the product into an oven, drying the product for 6 hours at the temperature of 80 ℃, and then cooling the product to room temperature;
(6) centrifugally cleaning the product after acid washing in the step (5) for 3 times by using deionized water until the product is neutral, and then drying the product in an oven at 80 ℃;
(7) taking out the dried product in the step (6), putting the dried product into a porcelain boat again, carrying out secondary calcination for 0.5 hour at 900 ℃ in a tube furnace in an inert atmosphere, and then cooling to room temperature;
(8) and (5) taking out the product in the step (7) to obtain the catalyst of the invention.
Example 6
(1) Taking 130g of cotton, putting the cotton into a closed container filled with 10 times of deionized water and ethanol mixed solution (the ratio is 1: 2), heating the cotton in an oven at 100 ℃ for 36 hours, taking out the cotton after cooling to room temperature, and putting the cotton into the oven for drying;
(2) weighing 5g of heme, 3g of cobalt acetate, 2g of poly (m-phenylenediamine) and 3g of hydroxylamine chloride to prepare a uniform mixed solution;
(3) weighing the dried cotton in the step (1), soaking the cotton into the mixed solution in the step (2), and then putting the cotton into a freeze dryer for freeze vacuum drying for 96 hours;
(4) putting the cotton freeze-dried in the step (3) into a porcelain boat, heating to 1600 ℃ in a microwave oven for 60 minutes in an inert N2 gas atmosphere, calcining for 8 hours, introducing 60 minutes of ammonia gas at 500 ℃, and then cooling to room temperature;
(5) taking the product in the step (4) out of the tube furnace, carrying out ball milling for 60 minutes, adding strong acid for pickling, putting the product into an oven, drying the product for 24 hours at the temperature of 80 ℃, and then cooling the product to room temperature;
(6) centrifugally cleaning the product after acid washing in the step (5) for 6 times by using deionized water until the product is neutral, and then drying the product in an oven at 80 ℃;
(7) taking out the dried product in the step (6), putting the dried product into a porcelain boat again, carrying out secondary calcination in a tube furnace at 1600 ℃ for 8 hours in an inert atmosphere, and then cooling to room temperature;
(8) and (5) taking out the product in the step (7) to obtain the catalyst of the invention.
Example 7
(1) Taking 1.2g of cotton, putting the cotton into a closed container filled with a mixed solution of deionized water and ethanol (the ratio is 1: 1), heating the cotton in an oven at 100 ℃ for 1 hour, cooling the cotton to room temperature, taking out the cotton, and putting the cotton into the oven for drying;
(2) weighing 5g of ferric chloride, 3g of cobalt chloride, 1g of poly (m-phenylenediamine) and 3g of hydroxylamine chloride to prepare a uniform mixed solution;
(3) weighing the dried cotton in the step (1), soaking the cotton into the mixed solution in the step (2), and then putting the cotton into a freeze dryer for freeze vacuum drying for 24 hours;
(4) putting the cotton freeze-dried in the step (3) into a porcelain boat, heating to 500 ℃ in a microwave oven for 30 minutes in an inert N2 gas atmosphere, calcining for 0.1 hour, introducing 5 minutes of ammonia gas at 400 ℃, and then cooling to room temperature;
(5) taking the product in the step (4) out of the tube furnace, carrying out ball milling for 30 minutes, adding strong acid for pickling, putting the product into an oven, drying the product for 1 hour at the temperature of 80 ℃, and then cooling the product to room temperature;
(6) centrifugally cleaning the product after acid washing in the step (5) for 3 times by using deionized water until the product is neutral, and then drying the product in an oven at 80 ℃;
(7) taking out the dried product in the step (6), putting the dried product into a porcelain boat again, carrying out secondary calcination for 0.1 hour at 500 ℃ in a tube furnace in an inert atmosphere, and then cooling to room temperature;
(8) taking out the product in the step (7) to obtain the catalyst of the invention;
example 8
(1) Taking 2.4g of cotton, putting the cotton into a closed container filled with a mixed solution of deionized water and ethanol (the ratio is 1: 1), heating the cotton in an oven at 100 ℃ for 2 hours, cooling the cotton to room temperature, taking out the cotton, and drying the cotton in the oven;
(2) weighing 5g of ferric chloride, 3g of cobalt chloride, 1g of poly (m-phenylenediamine) and 3g of hydroxylamine chloride to prepare a uniform mixed solution;
(3) weighing the dried cotton in the step (1), soaking the cotton into the mixed solution in the step (2), and then putting the cotton into a freeze dryer for freeze vacuum drying for 48 hours;
(4) putting the cotton freeze-dried in the step (3) into a porcelain boat, heating to 1200 ℃ in a microwave oven for 30 minutes in an inert N2 gas atmosphere, calcining for 0.3 hour, introducing 5 minutes of ammonia gas at 500 ℃, and then cooling to room temperature;
(5) taking the product in the step (4) out of the tube furnace, carrying out ball milling for 30 minutes, adding strong acid for pickling, putting the product into an oven, drying the product for 2 hours at the temperature of 80 ℃, and then cooling the product to room temperature;
(6) centrifugally cleaning the product after acid washing in the step (5) for 3 times by using deionized water until the product is neutral, and then drying the product in an oven at 80 ℃;
(7) taking out the dried product in the step (6), putting the dried product into a porcelain boat again, carrying out secondary calcination for 0.3 hour at 900 ℃ in a tube furnace in an inert atmosphere, and then cooling to room temperature;
(8) taking out the product in the step (7) to obtain the catalyst of the invention;
test example-catalyst Activity and stability
The oxygen reduction catalyst prepared by using cotton as a raw material (as in example 1) has very high half-wave potential which reaches 0.893V and is 25mV higher than that of a commercial Pt/C catalyst (0.868V); the limiting current is slightly higher than Pt/C; meanwhile, the limit current is only 17.4 percent through a 24000s stability i-t testThe attenuation of (a) is far more stable than that of a Pt/C catalyst (attenuation of 45.6%) under the same conditions. In addition, the power density of a metal-air battery prepared by the catalyst is up to 286mW/cm under the 1V state2Is superior to the prior common MnO2Cell performance of catalyst Assembly prepared for feedstock (228 mW/cm)2). See fig. 3-5. Test example two synergistic Effect of the polymetallic Polynitrogen Source of the invention
The invention comprises the following steps: example 1
Control group 1: weighing 8.4g of ferric chloride to prepare a uniform solution; the other steps were carried out as in example 1.
Control group 2: weighing 8.4g of ferric chloride and 4.6g of poly (m-phenylenediamine) to prepare a uniform mixed solution; the other steps were carried out as in example 1.
The method comprises the following steps: the catalysts of the invention and the catalysts of the control groups 1, 2 were subjected to ORR electrocatalytic performance tests.
As a result: as shown in Table 1, the half-wave potential of the performance of the single metal doped control group 1 is only about 0.72V, the half-wave potential of the single metal doped nitrogen source of the control group 2 can reach about 0.84V, and the ratio of the multi-metal multi-nitrogen source of the invention to the commercial Pt/C catalyst (0.868V) is as high as 0.893V. Therefore, the multi-metal multi-nitrogen source has synergistic effect on improving the activity of the catalyst.
TABLE 1 ORR electrocatalytic performance synergy of polymetallic polynitrogen sources
Claims (3)
1. A preparation method of a catalyst taking biomass cotton as carbon base is characterized by comprising the following steps:
(1) placing cotton into a closed container filled with 5-30 times of deionized water and ethanol mixed solution with the volume ratio of 1:2-2:1, heating in an oven at 80-100 ℃ for 1-5 hours, cooling to room temperature, taking out the cotton, and drying in the oven;
(2) weighing more than two metal salts and a nitrogen source to prepare a uniform mixed solution;
(3) weighing the dried cotton in the step (1), soaking the cotton into the mixed solution in the step (2), and then putting the cotton into a freeze dryer for freeze vacuum drying for 36-72 hours;
(4) putting the cotton freeze-dried in the step (3) into a porcelain boat, heating the cotton in a microwave oven for 20-40 minutes in an inert atmosphere to be calcined at the temperature of 1000-1200 ℃ for 0.1-1 hour, introducing ammonia gas for 5-30 minutes at the temperature of 400-600 ℃, and then cooling the cotton to room temperature;
(5) taking the product in the step (4) out of the microwave oven, carrying out ball milling for 5-60 minutes, adding strong acid for pickling, putting the product into an oven, drying the product for 1-24 hours at 60-100 ℃, and then cooling the product to room temperature;
(6) centrifugally cleaning the product after acid washing in the step (5) for 3-6 times by using deionized water until the product is neutral, and then drying the product in an oven at 60-100 ℃;
(7) taking out the dried product in the step (6), putting the product into a porcelain boat again, carrying out secondary calcination for 0.1-1 h at the temperature of 500 ℃ and 1000 ℃ in a tube furnace in an inert atmosphere, and then cooling to room temperature;
(8) taking out the product in the step (7) to obtain the catalyst of the invention;
the mass ratio of the cotton to the metal salt to the nitrogen source is 1: (0.1-5): (0.1-5); the metal salt is iron group salt and cobalt group salt according to the mass ratio (1-3): (3-1); the nitrogen source is prepared by mixing a high molecular polymer and a nitrogen-containing salt according to the mass ratio of (1-5): (5-1).
2. The method of claim 1, wherein the iron group salt is one or more of ferric chloride, ferric nitrate, and heme; the cobalt group salt is one or more of cobalt chloride, cobalt nitrate and cobalt acetate; the nitrogen source is poly-m-phenylenediamine and hydroxylamine chloride.
3. The method of claim 1, comprising the steps of:
(1) taking 24 parts of cotton, and putting the cotton into a container containing the components in a volume ratio of 1:1, heating the mixture in a 100 ℃ oven for 2 hours in a closed container of the deionized water and ethanol mixed solution, cooling to room temperature, taking out the cotton, and drying in the oven;
(2) weighing 5.4 parts of ferric chloride, 3.1 parts of cobalt chloride, 1.2 parts of poly-m-phenylenediamine and 3.4 parts of hydroxylamine chloride to prepare a uniform mixed solution;
(3) weighing the dried cotton in the step (1), soaking the cotton into the mixed solution in the step (2), and then putting the cotton into a freeze dryer for freeze vacuum drying for 48 hours;
(4) putting the cotton freeze-dried in the step (3) into a porcelain boat, heating the cotton in a microwave oven for 30 minutes in an inert nitrogen atmosphere to be calcined at 1200 ℃ for 0.5 hour, introducing ammonia gas for 5 minutes at 500 ℃, and then cooling the cotton to room temperature;
(5) taking the product in the step (4) out of the microwave oven, carrying out ball milling for 30 minutes, adding strong acid for pickling, putting the product into an oven, drying the product for 6 hours at 80 ℃, and then cooling the product to room temperature;
(6) centrifugally cleaning the product after acid washing in the step (5) for 3 times by using deionized water until the product is neutral, and then drying the product in an oven at 80 ℃;
(7) taking out the dried product in the step (6), putting the dried product into a porcelain boat again, calcining the product for 0.5 hour at 900 ℃ in a tube furnace in inert atmosphere, and then cooling the product to room temperature;
(8) and (5) taking out the product in the step (7) to obtain the catalyst of the invention.
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