CN110911697B - Transition metal/nitrogen-doped porous carbon nanosphere electrocatalyst and preparation method thereof - Google Patents
Transition metal/nitrogen-doped porous carbon nanosphere electrocatalyst and preparation method thereof Download PDFInfo
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Abstract
The invention discloses a transition metal/nitrogen doped porous carbon nanosphere electrocatalyst and a preparation method thereof, wherein the method comprises the following steps: putting a precursor solution consisting of a template agent, a carbon source and a nitrogen source into a reaction kettle, and heating to obtain nitrogen-doped carbon nanosphere powder; carrying out ultrasonic treatment on the nitrogen-doped carbon nanospheres and a transition metal salt solution, and then carrying out vacuum drying to obtain transition metal/nitrogen-doped carbon nanosphere powder; and carbonizing the transition metal/nitrogen-doped carbon nanosphere powder in inert gas to obtain the transition metal/nitrogen-doped porous carbon nanosphere electrocatalyst. The preparation method can adjust the content of the transition metal adsorbed by the nitrogen-doped carbon nanospheres by adjusting the content of the nitrogen source, thereby effectively improving the catalytic activity of the electrocatalyst. The template agent is decomposed at high temperature, acid and alkali etching is not needed to remove the template, and the prepared electrocatalyst has a large specific surface area, so that adsorption and catalytic reactions can be carried out conveniently, and the catalytic efficiency is greatly improved.
Description
Technical Field
The invention relates to the technical field of chemical energy materials, in particular to a transition metal/nitrogen doped porous carbon nanosphere electrocatalyst and a preparation method thereof.
Background
With the exhaustion of traditional fossil fuels and the damage of burning fossil fuels and chemical industries to the environment, energy crisis and environmental pollution become the biggest challenges facing human beings today, and research and development of novel clean energy and devices are urgently needed. Among many new energy conversion and storage devices, fuel cells, metal-air cells, and the like have been widely studied with advantages of high conversion efficiency, low emission, and the like. However, since the cathode oxygen reduction reaction is a major factor limiting the power of the battery due to slow kinetics, it is usually required to improve the reaction efficiency in the presence of an electrocatalyst, which is currently commercialized as Pt/C, but since the precious metal Pt is scarce in resources, expensive, and the Pt-based electrocatalyst has poor stability and methanol tolerance, it has been prevented from being widely used in fuel cells and metal-air batteries.
In recent years, researchers have studied and designed a number of non-noble metal electrocatalysts that can replace Pt-based electrocatalysts, such as transition metal oxides/nitrides/sulfides; non-metal hetero-atom doped carbon materials such as nitrogen, phosphorus, sulfur, boron, and the like; transition metal/nonmetal heterogeneous atom doped carbon nano-materials, such as iron/nitrogen co-doped carbon nanospheres, cobalt/nitrogen co-doped graphene, iron/nitrogen, sulfur co-doped carbon nanotubes and the like. The transition metal/nitrogen co-doping can change the electronic structure of the carbon nano material and provide a large number of active sites, so that the catalytic oxygen reduction reaction is facilitated, and the carbon nano material is stable in structure and is beneficial to the stability of an electrocatalyst, so that the advantages become research hotspots. In order to further improve the catalytic efficiency of the electrocatalyst and reduce the cost of the electrocatalyst, the transition metal/nitrogen-doped porous carbon nano material is produced at the same time, the metal monoatomic can maximize the metal utilization rate, and a large number of defect sites of the porous carbon nano material are doped with nitrogen atoms to promote the formation of transition metal-nitrogen bonds and further improve the catalytic activity of the electrocatalyst. However, the existing preparation method of the transition metal/nitrogen-doped porous carbon nanomaterial needs acid-base etching to remove the template, the nitrogen doping process is complex, the nitrogen content is not adjustable, the preparation process is complex, the cost is high, and the commercial popularization is difficult.
Accordingly, the prior art is yet to be improved and developed.
Disclosure of Invention
The technical problem to be solved by the invention is to provide a preparation method of a transition metal/nitrogen-doped porous carbon nanosphere electrocatalyst aiming at overcoming the defects in the prior art, and aiming at solving the problems that the existing preparation method needs acid-base etching to remove a template, the nitrogen doping process is complex, the nitrogen content is not adjustable, the preparation process is complex, the cost is high, and the commercialization popularization is difficult.
The technical scheme adopted by the invention for solving the technical problem is as follows: a preparation method of a transition metal/nitrogen doped porous carbon nanosphere electrocatalyst comprises the following specific steps:
sequentially adding a template agent, a carbon source and a nitrogen source into deionized water to obtain a precursor solution;
putting the precursor solution into a reaction kettle, and heating to obtain nitrogen-doped carbon nanosphere powder;
dissolving the nitrogen-doped carbon nanosphere powder and a transition metal salt in deionized water, performing ultrasonic treatment, and performing vacuum drying to obtain transition metal/nitrogen-doped carbon nanosphere powder;
and carbonizing the transition metal/nitrogen-doped carbon nanosphere powder in inert gas to obtain the transition metal/nitrogen-doped porous carbon nanosphere electrocatalyst.
The preparation method of the transition metal/nitrogen doped porous carbon nanosphere electrocatalyst comprises the steps of preparing a template agent from a triblock copolymer F127, preparing a carbon source from gamma-cyclodextrin, and preparing a nitrogen source from p-phenylenediamine.
The preparation method of the transition metal/nitrogen-doped porous carbon nanosphere electrocatalyst is characterized in that the mass ratio of the carbon source to the template agent is 2: 1-8: 1.
The preparation method of the transition metal/nitrogen-doped porous carbon nanosphere electrocatalyst is characterized in that the molar ratio of the carbon source to the nitrogen source is 1: 1-4: 1.
The preparation method of the transition metal/nitrogen-doped porous carbon nanosphere electrocatalyst is characterized in that the mass ratio of the nitrogen-doped carbon nanosphere powder to the transition metal salt is 1: 1-1: 3.
The preparation method of the transition metal/nitrogen doped porous carbon nanosphere electrocatalyst is characterized in that the transition metal salt is CuCl2·H2O、FeCl3·6H2O and CoCl2·6H2And O is one of the compounds.
The preparation method of the transition metal/nitrogen-doped porous carbon nanosphere electrocatalyst comprises the following steps of putting the precursor solution into a reaction kettle, and heating to obtain nitrogen-doped carbon nanosphere powder:
and placing the precursor solution into a reaction kettle, placing the reaction kettle into a constant-temperature oven at 180-220 ℃, placing for 2-8 h, washing for 3-5 times by using deionized water, and drying for 5-12 h at 50-80 ℃ to obtain the nitrogen-doped carbon nanosphere powder.
The preparation method of the transition metal/nitrogen doped porous carbon nanosphere electrocatalyst is characterized in that the carbonization temperature is 650-1000 ℃; and the temperature rise rate during carbonization is 2-8 ℃/min.
A transition metal/nitrogen-doped porous carbon nanosphere electrocatalyst is prepared by the preparation method of the transition metal/nitrogen-doped porous carbon nanosphere electrocatalyst.
Has the advantages that: the preparation method can regulate the yield, the size and the nitrogen content of the nitrogen-doped carbon nanospheres by regulating the content of the nitrogen source so as to regulate the content of the transition metal adsorbed by the nitrogen-doped carbon nanospheres, thereby effectively improving the catalytic activity of the electrocatalyst. The template agent is decomposed at high temperature, acid and alkali etching is not needed to remove the template, and the prepared electrocatalyst has a large specific surface area, so that adsorption and catalytic reactions can be carried out conveniently, and the catalytic efficiency is greatly improved.
Drawings
Fig. 1 is a scanning electron microscope image of nitrogen-doped carbon nanoball prepared in example 2;
fig. 2 is a scanning electron microscope image of the nitrogen-doped carbon nanoball prepared in example 3;
fig. 3 is a scanning electron micrograph of the nitrogen-doped carbon nanoball prepared in example 5;
FIG. 4 is a transmission electron micrograph of the electrocatalyst prepared in example 4;
FIG. 5 is an X-ray absorption near-edge structure spectrum of the electrocatalyst prepared in example 4;
FIG. 6 is a cyclic voltammogram of the electrocatalyst modified electrodes prepared in example 1, example 3 and example 4;
FIG. 7 is a linear sweep voltammogram of the electrocatalyst modified electrodes prepared in example 1, example 3 and example 4;
FIG. 8 cyclic voltammograms of the electrocatalyst prepared in example 4 and commercial Pt/C electrocatalyst modified electrodes;
figure 9 half-wave potential diagrams of electrocatalysts prepared in example 4 versus commercial Pt/C electrocatalyst-modified electrodes.
Detailed Description
The present invention provides a transition metal/nitrogen doped porous carbon nanosphere electrocatalyst and a preparation method thereof, and the present invention is further described in detail below in order to make the objects, technical schemes and advantages of the present invention clearer. It should be understood that the specific embodiments described herein are merely illustrative of the invention and do not limit the invention.
Specifically, the preparation method of the transition metal/nitrogen doped porous carbon nanosphere electrocatalyst provided by the invention comprises the following steps:
and S1, sequentially adding the template agent, the carbon source and the nitrogen source into deionized water to obtain a precursor solution.
Because the prior preparation method of the transition metal/nitrogen-doped porous carbon nanosphere electrocatalyst needs acid-base etching to remove the template, the nitrogen doping process is complex and the nitrogen content is not adjustable, the preparation process is complex, the cost is high, and the commercial popularization is difficult. In order to solve the above problems, in this embodiment, a template is first added into deionized water, the mixture is magnetically stirred at room temperature until the template is completely dissolved, a carbon source is then added into the solution, the mixture is continuously magnetically stirred at room temperature for 0.5 to 1 hour until the carbon source is completely dissolved, a nitrogen source is then added into the solution, and the mixture is continuously magnetically stirred at room temperature until the nitrogen source is completely dissolved, so that a precursor solution containing the template, the carbon source, and the nitrogen source is obtained for preparing nitrogen-doped carbon nanospheres in subsequent steps. In a specific embodiment, the stirring speed of the template, the carbon source and the nitrogen source is 100-400 rpm, and the stirring time is 3-4 h.
And S2, placing the precursor solution in a reaction kettle, carrying out constant-temperature hydrothermal treatment, and drying to obtain nitrogen-doped carbon nanosphere powder.
In one embodiment, the templating agent is a triblock copolymer ethylene oxide-propylene oxide-ethylene oxide (F127), the carbon source is γ -cyclodextrin, and the nitrogen source is p-phenylenediamine. Due to the action of the host and the guest, the triblock copolymer F127 passes through the inner cavity of the gamma-cyclodextrin to form an inclusion compound, and then forms a spherical micelle through the action of hydrogen bonds. And (3) carrying out high-temperature hydrothermal treatment, and further polymerizing and carbonizing the gamma-cyclodextrin on the surface of the spherical micelle to obtain the nitrogen-doped carbon sphere nanosphere solution. And drying the nitrogen-doped carbon nanosphere solution to obtain nitrogen-doped carbon nanosphere powder.
In a specific embodiment, the step S2 specifically includes:
s21, placing the precursor solution in a reaction kettle, placing the reaction kettle in a constant-temperature oven at 180-220 ℃ for 2-8 h, washing with deionized water for 3-5 times, and drying at 50-80 ℃ for 5-12 h to obtain nitrogen-doped carbon nanosphere powder.
In a specific embodiment, in this embodiment, the temperature of the oven is raised to 180 to 220 ℃ in advance, and then the reaction kettle filled with the precursor solution is placed in a constant-temperature oven to be heated for 2 to 8 hours, and the triblock copolymer F127, the gamma-cyclodextrin and the p-phenylenediamine are subjected to host-guest action, molecular self-assembly action, polymerization and carbonization under a high-temperature condition to form the nitrogen-doped carbon nanosphere solution. Because the nitrogen-doped carbon nanosphere solution contains the reacted by-product and the redundant reactant, after the nitrogen-doped carbon nanosphere solution is obtained, the nitrogen-doped carbon nanosphere solution is continuously centrifuged or filtered to remove the solvent, and then the nitrogen-doped carbon nanospheres after the solvent is removed are washed by deionized water for 3-5 times to remove the impurities attached to the surfaces of the nanospheres. And drying the washed nitrogen-doped carbon nanosphere solution at 50-80 ℃ for 5-12 h to obtain nitrogen-doped carbon nanosphere powder.
In a specific embodiment, the amount of gamma-cyclodextrin is too high, the triblock copolymer F127, gamma-cyclodextrin and p-phenylenediamine can be excessively crosslinked under high-temperature hydrothermal conditions, and a porous carbon structure cannot be formed in subsequent steps; the amount of gamma-cyclodextrin is too small, and the formed porous carbon has a weak structure. In a specific embodiment, when the mass ratio of the gamma-cyclodextrin to the triblock copolymer F127 is 8:1, the transition metal/nitrogen doped porous carbon nanosphere electrocatalyst with stable structure and excellent performance can be obtained in the subsequent steps.
In one embodiment, the nitrogen element and the carbon element are in adjacent positions in the periodic table, and the atomic radius of the nitrogen element and the carbon atom are close to each other, so that the doping of the nitrogen element has small influence on the lattice distortion of the carbon material. A certain amount of nitrogen is added into the porous carbon material, so that on one hand, the surface charge density of the porous carbon material is increased, and the defect sites of the porous carbon material can be increased, thereby enhancing the activity in electrochemical or electrocatalytic reactions. On the other hand, the porous carbon material nitrogen functional group enables the porous carbon material to be more easily combined with heavy metal ions, so that the metal ions can be more uniformly dispersed on the surface of the carbon material in the subsequent step. However, excessive nitrogen source disturbs the assembly process of gamma-cyclodextrin and triblock copolymer F127, resulting in self-polymerization or polycondensation of the precursor solution. In a specific embodiment, when the molar ratio of the gamma-cyclodextrin to the p-phenylenediamine is 1: 1-4: 1, the transition metal/nitrogen doped porous carbon nanosphere electrocatalyst with excellent performance can be obtained.
And S3, dissolving the nitrogen-doped carbon nanosphere powder and the transition metal salt in deionized water, performing ultrasonic treatment, and performing vacuum drying to obtain the transition metal/nitrogen-doped carbon nanosphere powder.
In a specific embodiment, after obtaining the nitrogen-doped carbon nanosphere powder, a certain amount of the nitrogen-doped carbon nanosphere powder and the transition metal salt are weighed and simultaneously dissolved in deionized water to obtain a mixed solution, the mixed solution is subjected to ultrasonic treatment, and transition metal ions are fully coordinated with nitrogen-containing functional groups on the surface of the nitrogen-doped carbon nanosphere under the ultrasonic action to obtain a transition metal/nitrogen-doped carbon nanosphere solution. And drying the transition metal/nitrogen-doped carbon nanosphere solution to remove the solvent, thereby obtaining transition metal/nitrogen-doped carbon nanosphere powder.
In one embodiment, the transition metal saltIs CuCl2·H2O、FeCl3·6H2O and CoCl2·6H2O, the ultrasonic time is more than or equal to 2 h. An appropriate amount of transition metal can increase the initial oxygen reduction potential and the limiting current density of the electrocatalyst, but too high a content of transition metal leads to a decline in the activity of the electrocatalyst. In one embodiment, the mass ratio of the nitrogen-doped carbon nanoball powder to the transition metal salt is 1: 1.
S4, carbonizing the transition metal/nitrogen-doped carbon nanosphere powder in inert gas to obtain the transition metal/nitrogen-doped porous carbon nanosphere electrocatalyst.
In a specific embodiment, after obtaining the transition metal/nitrogen-doped carbon nanosphere powder, the transition metal/nitrogen-doped carbon nanosphere powder is placed in a covered porcelain boat, and the porcelain boat is placed in a tube furnace and subjected to high-temperature carbonization under the protection of inert gas. The template agent in the transition metal/nitrogen-doped carbon nanosphere powder is decomposed at high temperature to obtain the transition metal/nitrogen-doped porous carbon nanosphere electrocatalyst.
In one embodiment, the inert gas comprises nitrogen, argon, and the like. The higher the carbonization temperature is, the higher the graphitization degree of the carbon material is, and the lower the content of nitrogen element doped on the surface is; the lower the carbonization temperature, the lower the degree of graphitization of the carbon material and poor removal of the templating agent. In one embodiment, the carbonization temperature is 2-8 ℃/min; the temperature rise rate during carbonization is 650-1000 ℃.
In a specific embodiment, after the step S4, the method further includes:
s5, soaking the transition metal/nitrogen-doped porous carbon nanosphere electrocatalyst in hydrochloric acid solution with the concentration of 0.5-2M for 1-3 hours, and drying the acid-washed transition metal/nitrogen-doped porous carbon nanosphere electrocatalyst at the temperature of 60-80 ℃ for 4-12 hours.
In one embodiment, the transition metal/nitrogen doped porous carbon nanosphere electrocatalyst obtained in the previous step has large particles of metal residues adsorbed on the surface, which can affect the catalytic performance of the electrocatalyst. Therefore, in the embodiment, after the transition metal/nitrogen-doped porous carbon nanosphere electrocatalyst is obtained, the electrocatalyst is further soaked in a hydrochloric acid solution with the concentration of 0.5-2M for 1-3 hours, and large metal particles on the surface of the electrocatalyst are removed. And then drying the acid-washed electrocatalyst for 4-12 h at the temperature of 60-80 ℃ to further obtain the monoatomic transition metal/nitrogen-doped porous carbon nanosphere electrocatalyst.
The invention also provides a transition metal/nitrogen doped porous carbon nanosphere electrocatalyst which is prepared by the preparation method.
The preparation method can adjust the content of the transition metal adsorbed by the nitrogen-doped carbon nanospheres by adjusting the content of the nitrogen source, thereby effectively improving the catalytic activity of the electrocatalyst. The template agent is decomposed at high temperature, acid and alkali etching is not needed to remove the template, and the prepared electrocatalyst has a large specific surface area, so that adsorption and catalytic reactions can be carried out conveniently, and the catalytic efficiency is greatly improved. The invention is further illustrated by the following specific examples.
Example 1
(1) Dissolving 0.125g F127 in 120ml deionized water, and magnetically stirring for 4h at room temperature until the solution is completely dissolved; dissolving 1g of gamma-cyclodextrin in the solution, stirring for 0.5h until the gamma-cyclodextrin is completely dissolved, and continuously stirring overnight to form a uniform and stable precursor solution;
(2) putting the precursor solution into a 200ml reaction kettle, carrying out hydrothermal treatment at a constant temperature of 220 ℃ for 6h, cooling, carrying out suction filtration/centrifugation on a product, repeatedly washing the obtained product with deionized water for 3 times, and drying the product at 60 ℃ for 12h to obtain 0.2g of brown carbon nanosphere powder;
(3) and (3) placing the brown carbon nanosphere powder into a tubular furnace, heating to 900 ℃ at the heating rate of 5 ℃/min in Ar atmosphere, preserving heat for 2h, and cooling along with the furnace to obtain the porous carbon nanospheres.
Example 2
(1) Dissolving 0.125g F127 in 120ml deionized water, and magnetically stirring for 4h at room temperature until the solution is completely dissolved; dissolving 1g of gamma-cyclodextrin in the solution, stirring for 0.5h until the gamma-cyclodextrin is completely dissolved, adding 0.0833g of p-phenylenediamine, and continuously stirring overnight to form uniform and stable precursor solution;
(2) putting the precursor solution into a 200ml reaction kettle, carrying out hydrothermal treatment at a constant temperature of 220 ℃ for 6h, cooling, carrying out suction filtration/centrifugation on a product, repeatedly washing the obtained product with deionized water for 3 times, and drying the product at 60 ℃ for 12h to obtain 0.33g of brown nitrogen-doped carbon nanosphere powder;
(3) and (3) placing the brown nitrogen-doped carbon nanosphere powder into a tubular furnace, heating to 900 ℃ at the heating rate of 5 ℃/min in Ar atmosphere, preserving the temperature for 2h, and cooling along with the furnace to obtain the nitrogen-doped porous carbon nanospheres.
Example 3
(1) Dissolving 0.125g F127 in 120ml deionized water, and magnetically stirring for 4h at room temperature until the solution is completely dissolved; dissolving 1g of gamma-cyclodextrin in the solution, stirring for 0.5h until the gamma-cyclodextrin is completely dissolved, adding 0.1667g of p-phenylenediamine, and continuously stirring overnight to form a uniform and stable precursor solution;
(2) putting the precursor solution into a 200ml reaction kettle, carrying out hydrothermal treatment at a constant temperature of 220 ℃ for 6h, cooling, carrying out suction filtration/centrifugation on a product, repeatedly washing the obtained product with deionized water for 3 times, and drying the product at 60 ℃ for 12h to obtain 0.45g of brown nitrogen-doped carbon nanosphere powder;
(3) and (3) placing the brown nitrogen-doped carbon nanosphere powder into a tubular furnace, heating to 900 ℃ at the heating rate of 5 ℃/min in the argon atmosphere, preserving the temperature for 2 hours, and cooling along with the furnace to obtain the nitrogen-doped porous carbon nanospheres.
Example 4
(1) Dissolving 0.125g F127 in 120ml deionized water, and magnetically stirring at room temperature for 4h until complete dissolution; dissolving 1g of gamma-cyclodextrin in the solution, stirring for 0.5h to completely dissolve the gamma-cyclodextrin, adding 0.1667g of p-phenylenediamine, and continuously stirring overnight to form a uniform and stable precursor solution;
(2) putting the precursor solution into a 200ml reaction kettle, carrying out hydrothermal treatment at a constant temperature of 220 ℃ for 6h, cooling, carrying out suction filtration/centrifugation on a product, repeatedly washing the obtained product with deionized water for 3 times, and drying the product at 60 ℃ for 12h to obtain 0.45g of brown nitrogen-doped carbon nanosphere powder;
(3) 0.3g of brown nitrogen-doped carbon nanosphere powder was mixed with 0.3g of CoCl2·6H2Dissolving O in 20ml of deionized water, ultrasonically dispersing for 2 hours, and then carrying out vacuum drying on the mixed solution at 80 ℃ to obtain transition metal/nitrogen-doped carbon nanosphere powder;
(4) putting the transition metal/nitrogen-doped carbon nanosphere powder into a tubular furnace, heating to 900 ℃ at the heating rate of 5 ℃/min in the Ar atmosphere, keeping the temperature for 2 hours, and then cooling along with the furnace to obtain the transition metal/nitrogen-doped porous carbon nanosphere electrocatalyst;
(5) the transition metal/nitrogen-doped porous carbon nanosphere electrocatalyst is soaked in hydrochloric acid with the concentration of 1M, and is subjected to suction filtration and drying after being magnetically stirred for 1 hour to obtain the monoatomic transition metal/nitrogen-doped porous carbon nanosphere electrocatalyst.
Example 5
The process of this example is essentially the same as example 2 except that the molar ratio of p-phenylenediamine to gamma-cyclodextrin is 3:1
Example 6
The process of this example is essentially the same as example 4 except that the calcination temperature is 800 ℃.
Example 7
The process of this example is essentially the same as example 4 except that the calcination temperature is 1000 ℃.
Application example 1
Ultrasonically dispersing the prepared electrocatalyst in a mixed solution of ethanol and Nafion, wherein the volume ratio of the ethanol to the Nafion is 25:1 to obtain electrocatalyst ink, uniformly dripping the electrocatalyst ink on a glassy carbon electrode, and naturally drying to obtain an electrocatalyst modified electrode. And taking a Pt wire as a counter electrode and Ag/AgCl as a reference electrode, and performing electrochemical test in KOH electrolyte with the concentration of 0.1M by adopting a standard three-electrode system.
Fig. 1 to 3 are SEM images of nitrogen-doped carbon nanoball prepared in example 2, example 3 and example 5, respectively, and the size of the nanoball increases and then decreases as the content of p-phenylenediamine increases; in addition, it is found from the research that the yield of the nitrogen-doped carbon nanosphere is increased with the increase of the p-phenylenediamine content, and the nitrogen content is increased, which is of great significance to the research of the nitrogen-doped carbon nanosphere.
Fig. 4 is a TEM image of the electrocatalyst prepared in example 4, and it can be seen that there are many bright spots evident on the surface of the grey carbon material.
Fig. 5 is an X-ray absorption near-edge structure spectrum of the electrocatalyst prepared in example 4, and it can be seen from fig. 2 and 3 that the transition metal in the electrocatalyst is in a monoatomic state, which effectively improves the atom utilization rate of the transition metal, thereby facilitating the catalytic reaction.
Fig. 6 is a cyclic voltammogram of the electrocatalyst-modified electrodes prepared in example 1, example 3 and example 4, from which it can be seen that all electrocatalysts have no significant reduction peak signal in nitrogen-saturated 0.1M KOH solution, while significant reduction peak signal occurs in oxygen-saturated 0.1M KOH solution, indicating that the electrocatalysts we prepared do have oxygen reduction catalytic activity. And the peak potential of the electrocatalyst obtained in example 4 is optimal.
Fig. 7 is a linear sweep voltammogram of the electrocatalyst modified electrodes obtained in example 1, example 3, and example 4, and the electrocatalyst obtained in example 4 has the optimal oxygen reduction catalytic activity with an initial potential of 0.93V (vs. rhe) and a half-wave potential of 0.86V (vs. rhe) compared to example 1 and example 3.
Fig. 8 and 9 are a linear sweep voltammogram and a half-wave potential diagram of the modified electrode of the electrocatalyst prepared in example 4 and a commercial Pt/C electrocatalyst, respectively, and it can be seen from fig. 8 and 9 that the catalytic activity of the electrocatalyst obtained in example 4 can be compared with that of the commercial Pt/C, the limiting current density and the half-wave potential of the electrocatalyst are both better than that of the commercial Pt/C, the cycling stability is more obviously better than that of the commercial Pt/C, the electrocatalyst is expected to be a non-noble metal electrocatalyst replacing the commercial Pt/C, and the electrocatalyst has important significance for promoting the development of fuel cells and metal-air cells. In addition, the research shows that the transition metal/nitrogen-doped porous carbon nanosphere electrocatalyst prepared by the method has good methanol tolerance.
In summary, the invention discloses a transition metal/nitrogen doped porous carbon nanosphere electrocatalyst and a preparation method thereof, wherein the method comprises the following steps: putting a precursor solution consisting of a template agent, a carbon source and a nitrogen source into a reaction kettle, and heating to obtain nitrogen-doped carbon nanosphere powder; carrying out ultrasonic treatment on the nitrogen-doped carbon nanospheres and a transition metal salt solution, and then carrying out vacuum drying to obtain transition metal/nitrogen-doped carbon nanosphere powder; and carbonizing the transition metal/nitrogen-doped carbon nanosphere powder in inert gas to obtain the transition metal/nitrogen-doped porous carbon nanosphere electrocatalyst. The preparation method can adjust the content of the transition metal adsorbed by the nitrogen-doped carbon nanospheres by adjusting the content of the nitrogen source, thereby effectively improving the catalytic activity of the electrocatalyst. The template agent is decomposed at high temperature, acid and alkali etching is not needed to remove the template, and the prepared electrocatalyst has a large specific surface area, so that adsorption and catalytic reactions can be carried out conveniently, and the catalytic efficiency is greatly improved.
It will be understood that the invention is not limited to the examples described above, but that modifications and variations will occur to those skilled in the art in light of the above teachings, and that all such modifications and variations are considered to be within the scope of the invention as defined by the appended claims.
Claims (4)
1. A preparation method of a transition metal/nitrogen doped porous carbon nanosphere electrocatalyst is characterized by comprising the following steps:
sequentially adding a template agent, a carbon source and a nitrogen source into deionized water to obtain a precursor solution, wherein the template agent is a triblock copolymer F127, the carbon source is gamma-cyclodextrin, and the nitrogen source is p-phenylenediamine;
placing the precursor solution in a reaction kettle, placing the reaction kettle in a constant-temperature oven at 180-220 ℃ for 2-8 h, washing with deionized water for 3-5 times, and drying at 50-80 ℃ for 5-12 h to obtain nitrogen-doped carbon nanosphere powder;
dissolving the nitrogen-doped carbon nanosphere powder and a transition metal salt in deionized water, performing ultrasonic treatment, and performing vacuum drying to obtain transition metal/nitrogen-doped carbon nanosphere powder;
carbonizing the transition metal/nitrogen-doped carbon nanosphere powder in inert gas to obtain a transition metal/nitrogen-doped porous carbon nanosphere electrocatalyst;
the mass ratio of the carbon source to the template is 2: 1-8: 1, the molar ratio of the carbon source to the nitrogen source is 1: 1-4: 1, the mass ratio of the nitrogen-doped carbon nanosphere powder to the transition metal salt is 1: 1-1: 3, and the transition metal salt is CuCl2·H2O、FeCl3·6H2O and CoCl2·6H2And O is one of the compounds.
2. The preparation method of the transition metal/nitrogen-doped porous carbon nanosphere electrocatalyst according to claim 1, wherein the carbonization temperature is 650-1000 ℃, and the temperature rise rate during carbonization is 2-8 ℃/min.
3. The method for preparing a transition metal/nitrogen-doped porous carbon nanosphere electrocatalyst according to claim 1, wherein the step of carbonizing the transition metal/nitrogen-doped carbon nanosphere powder in an inert gas to obtain the transition metal/nitrogen-doped porous carbon nanosphere electrocatalyst further comprises:
soaking the transition metal/nitrogen-doped carbon nanosphere electrocatalyst in a hydrochloric acid solution with the concentration of 0.5-2M for 1-3 h, and drying the acid-washed transition metal/nitrogen-doped porous carbon nanosphere electrocatalyst at 60-80 ℃ for 4-12 h.
4. A transition metal/nitrogen doped porous carbon nanosphere electrocatalyst, characterized in that it is prepared by the method of any one of claims 1 to 3.
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| CN114367295B (en) * | 2020-10-15 | 2023-04-18 | 中国科学院大连化学物理研究所 | Application of monodisperse carbon-supported non-noble metal material as ethylbenzene anaerobic dehydrogenation catalyst |
| CN112349920A (en) * | 2020-10-30 | 2021-02-09 | 天津工业大学 | Preparation of iron-nitrogen co-doped porous carbon sphere electrocatalyst |
| CN112615014A (en) * | 2020-12-17 | 2021-04-06 | 中国科学技术大学 | Catalyst and preparation method and application thereof |
| CN112864402B (en) * | 2021-01-11 | 2022-10-28 | 无棣正海化工有限公司 | Preparation and application of oxygen reduction catalyst of Fe-N co-doped mesoporous carbon |
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| CN113333008A (en) * | 2021-05-20 | 2021-09-03 | 济南大学 | Method for preparing nitrogen-doped nickel-based catalyst by using cyclodextrin and nickel acetate and application of nitrogen-doped nickel-based catalyst |
| CN113351236A (en) * | 2021-06-08 | 2021-09-07 | 哈尔滨工业大学（深圳） | Porous nitrogen-doped carbon-based transition metal monatomic catalyst, and preparation method and application thereof |
| CN113362662A (en) * | 2021-06-30 | 2021-09-07 | 重庆五洲世纪文化传媒有限公司 | AR-based preschool education system |
| CN113611881B (en) * | 2021-07-09 | 2022-08-16 | 中国海洋大学 | Atomic-level dispersed Fe/nitrogen-doped mesoporous carbon spheres and preparation method and application thereof |
| CN113909072B (en) * | 2021-08-27 | 2023-05-02 | 青岛科技大学 | Preparation method of metal doped porous carbon microsphere/CNTs composite material |
| CN113699554B (en) * | 2021-09-17 | 2022-11-15 | 中国矿业大学 | Preparation method and application of rare earth metal and transition metal co-doped carbon-based material |
| CN114959779B (en) * | 2022-04-13 | 2023-11-21 | 同济大学 | CoNiSe 2 Nano-rod modified porous nitrogen-doped carbon sphere composite material and preparation method thereof |
| CN115414912B (en) * | 2022-08-31 | 2023-11-03 | 河北工业大学 | Preparation method of nitrogen-doped hierarchical pore carbon adsorption material |
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