CN109023417B - Preparation method and application of iron carbide-cobalt/nitrogen-doped carbon nanocomposite - Google Patents

Abstract

The invention relates to a preparation method and application of an iron carbide-cobalt/nitrogen doped carbon nano composite material, which specifically comprises the following steps: a. constructing a mesoporous ordered KIT-6 silicon template; b. mixing Co (NO)₃)₂·6H₂O and Fe (NO)₃)₃·9H₂Injecting O, melamine and P123 into the pores of the KIT-6 template; c. the above mixture is in N₂Annealing under ambient conditions to make Co (NO)₃)₂·6H₂O and Fe (NO)₃)₃·9H₂O is decomposed and chemically reacted with carbon obtained by pyrolysis of P123 and melamine; d. corroding the product after the heat treatment by using a NaOH solution; obtained Fe₃The C-Co/NC composite material has larger specific surface area and excellent conductivity, shows excellent catalytic performance for oxygen reduction and electrolytic water reaction of the cathode of the alkaline fuel cell, and provides a new idea for reasonably designing and constructing the multifunctional electrocatalyst.

Description

Preparation method and application of iron carbide-cobalt/nitrogen-doped carbon nanocomposite

The technical field is as follows:

the invention relates to a preparation method of an iron carbide-cobalt/nitrogen doped carbon nano composite material, an oxygen reduction reaction for a fuel cell cathode and application in an electrolytic water reaction.

Background art:

the increasing energy crisis and environmental pollution have prompted people to find and develop inexpensive, efficient, clean energy storage and conversion technologies to meet the enormous demands on energy from transportation vehicles, power generation equipment, and the like. Electrocatalytic reactions, such as Oxygen Reduction Reaction (ORR), Oxygen Evolution Reaction (OER), Hydrogen Evolution Reaction (HER), and the like, play a crucial role in energy systems such as fuel cells, rechargeable metal-air batteries, and the like. Therefore, how to develop efficient and cheap ORR, OER and HER catalysts is a hot issue in the field of catalytic materials. In order to make the above reaction proceed efficiently, it is necessary to use an electrocatalyst to reduce the overpotential of the reaction process and thus to accelerate the reaction rate. Although platinum (Pt) and platinum-based noble metal catalysts have high catalytic activity for HER and ORR reactions, their catalytic activity for OER reactions is relatively poor, which limits their large-scale applications such as full-water splitting, rechargeable metal-air batteries, and renewable fuel cells. Furthermore, the scarcity and high cost of precious metals has further hindered the large-scale commercial application of clean and efficient electrochemical energy technologies. In view of the above problems, research and development of a high-efficiency, stable, and inexpensive multifunctional catalyst as a substitute for noble metal-based catalysts is imperative.

Recent studies have shown that the integration of one-dimensional and two-dimensional carbon-based materials can further increase the electrocatalytic activity thereof, because the interface of the one-dimensional and two-dimensional carbon nanomaterials can significantly improve the electron transport efficiency and improve the electrical conductivity thereof. Although there are reports in the literature that the catalytic activity can be increased by complexing transition metals (such as Fe and Co) with nitrogen-doped carbon materials, there are few reports that the catalytic activity is limited to a single or two reactions, and that the catalytic activity is highly effective for multiple reactions.

In order to solve the problems, a small number of F are constructed by a template sacrificing strategy₃Composite material (Fe) with C and Co nanoparticles highly dispersed in hierarchical structure of porous one-dimensional carbon nanotube and two-dimensional carbon nanosheet₃C-Co/NC). In this composite, nitrogen-doped carbon not only improves the electrical conductivity and corrosion resistance of the composite, but also introduces more defects to provide catalytically active sites. The hierarchical structure of the porous carbon nanotube and the nano-sheet with high specific surface area and porous characteristic accelerates the transmission of electrons and substances. Fe encapsulated in hierarchical carbon nanomaterials₃The C and Co nanoparticles can effectively regulate and control the electronic structure around carbon, and the carbon structure in turn improves Fe₃The dispersity and the utilization efficiency of C and Co form a synergistic effect, and the catalytic reaction is further accelerated. The composite material is used as a catalyst for oxygen reduction reaction and water decomposition reaction, and shows excellent catalytic performance. The invention provides a new idea for reasonably designing and constructing the multifunctional electrocatalyst.

The invention content is as follows:

the invention aims to provide a preparation method and application of an iron carbide-cobalt/nitrogen doped carbon nano composite material. Through synergistic effect, catalytic reaction is further accelerated, and a new thought is provided for reasonable design and construction of the multifunctional electrocatalyst.

The above purpose of the invention is realized by the following technical scheme:

iron carbide-cobalt/nitrogen doped carbon nanocomposite (Fe)₃C-Co/NC) preparation method, comprising the following steps:

a. constructing a KIT-6 silicon template: adding 5-7 g of P123, namely polyethylene oxide-propylene oxide-ethylene oxide and 14-15 ml of 37% hydrochloric acid solution into 210-220 ml of deionized water, adding 7-8 ml of n-butyl alcohol, stirring at 30-40 ℃ for 1-2 h, then dropwise adding 13-14 ml of ethyl orthosilicate, and continuously stirring at 30-40 ℃ for 24 h; then transferring the mixture into a polytetrafluoroethylene reaction kettle, and reacting for 20-24 hours at the temperature of 100-120 ℃; centrifuging and washing the reacted solution by using water and ethanol, and drying the solution in vacuum at the temperature of 60-80 ℃ for 20-24 hours; finally, annealing the obtained white powder in air at 500-800 ℃ for 3-5 h, and naturally cooling to room temperature;

b. 0.1-0.2 g of Co (NO)₃)₂·6H₂O、0.3～0.4g Fe(NO₃)₃·9H₂Adding O, 5-6 g of melamine, 1-1.5 g of prepared mesoporous KIT-6 silicon template and 2-3 g of P123 into 20-30 ml of mixed solution of water and ethanol, respectively stirring for 2-3 h and carrying out ultrasonic treatment for 2-3 h, and then continuously stirring the mixed solution strongly in a constant-temperature oil bath at the temperature of 60-80 ℃ until the mixed solution is completely evaporated to obtain solid powder;

c. adding the solid powder of step b in N₂Preserving heat for 2-3 h at 400-500 ℃ in the environment, and then preserving heat for 4-5 h at 800-900 ℃;

d. corroding the heat-treated sample with 2-3M NaOH solution to remove the mesoporous KIT-6 template, centrifuging and washing with water and ethanol, and vacuum-drying at 60-80 ℃ for 10-12 h to obtain Fe₃C-Co/And (3) NC composite material.

In the step a, in the process of preparing the ordered mesoporous KIT-6 silicon template, the shape of the KIT-6 template is controlled by adjusting the temperature of hydrothermal reaction.

And (c) performing heat treatment at 800-900 ℃ in the step c, so that the graphitization degree of the carbon material is improved, and the conductivity of the composite material is increased.

And d, placing the mixture in NaOH solution in order to remove the silicon template, generate porous carbon nano sheets and nano tubes, increase the specific surface area of the carbon nano sheets and the nano tubes, and facilitate the transmission of substances in the carbon nano sheets and the acceleration of the reaction rate.

The iron carbide-cobalt/nitrogen-doped carbon nanocomposite obtained by the preparation method is used as a catalyst for electrochemical test, and comprises the following steps:

a. preparation of catalyst ink: respectively adding Fe₃C-Co/NC, commercial Pt/C and RuO₂Adding the catalyst into 1ml of naphthol/isopropanol aqueous solution, and carrying out ultrasonic treatment for 30-90 min to obtain catalyst ink;

b. preparation of a working electrode: taking out 10-40 mul of catalyst ink, dripping the catalyst ink on a glassy carbon electrode, and drying at room temperature to prepare a working electrode loaded with a catalyst;

c. the electrochemical test was carried out in a standard three-electrode test system, in which the electrode prepared in step b was used as the working electrode, the carbon rod as the counter electrode, the Ag/AgCl as the reference electrode, 0.1M KOH, 1M KOH or 0.5M H₂SO₄The solution is used as electrolyte tested in different solution environments;

d. with said Fe₃Testing the C-Co/NC composite material serving as a working electrode on an Ivium-n-Stat electrochemical workstation, converting all electrode potentials into reversible hydrogen electrode potentials, and normalizing the obtained current density to the geometric area of the working electrode; oxygen reduction reaction test in N₂Or O₂Saturated 0.1M KOH solution, and the intermediate product and the number of transferred electrons of the reaction are detected by a rotating disc ring electrode; for the oxygen evolution reaction, the catalyst loading was 0.4mg cm^-2(ii) a Electrocatalytic activity test of hydrogen evolution reaction at N₂Saturation of1M KOH or 0.5M H₂SO₄Is carried out in solution; the stability of the catalyst was tested using chronoamperometry, i.e. current-time or chronopotentiometry.

The invention has the technical effects that:

fe prepared by the invention₃The C-Co/NC nano composite material has larger specific surface area and excellent conductivity, and shows excellent catalytic performance for oxygen reduction reaction and electrolytic water reaction of the cathode of the alkaline fuel cell. The invention provides a new idea for reasonably designing and constructing the multifunctional electrocatalyst.

The composite material has excellent catalytic performance on the oxygen reduction reaction of the cathode of the alkaline fuel cell: the positive half-wave potential reaches 0.885V; the limiting diffusion current density is-5.5 mA cm^-2(ii) a The number of electrons transferred by the oxygen reduction reaction is 3.9, which is close to a theoretical value of 4; after 10000 circles of accelerated attenuation test, the half-wave potential is almost unchanged; the current density decayed only 8% after the 60000s continuous chronoamperometric test. The composite material also has excellent catalytic performance on the water electrolysis reaction: the initial potentials for the hydrogen evolution reactions in the alkaline and acidic solutions were-0.083V and-0.186V, respectively; the current density is 10mAcm^-2Overpotential of time is 238mV and 298mV respectively; at a current density of 10mA cm^-2The overpotential for the oxygen evolution reaction was only 340 mV.

Description of the drawings:

FIG. 1 example of Fe₃ORR electrocatalytic properties of C-Co/NC nanocomposites.

FIG. 2, Transmission Electron Microscope (TEM) photograph of KIT-6 template prepared in the example of the present invention.

FIG. 3 Fe in the examples of the present invention₃TEM photographs of C-Co/NC nanocomposites.

FIG. 4 Fe in the examples of the present invention₃TEM photographs of C-Co/NC nanocomposites.

FIG. 5 Fe in the examples of the present invention₃HRTEM photograph of C-Co/NC nanocomposite.

FIG. 6 Fe in the examples of the present invention₃XRD pattern of C-Co/NC nanocomposite.

FIG. 7 Fe in the examples of the present invention₃Thermogravimetric mapping of C-Co/NC nanocomposites.

FIG. 8 example of Fe₃N of C-Co/NC nanocomposites₂Adsorption/desorption profiles, wherein the inset is the pore size distribution curve of the sample obtained according to the adsorption curve by the Barrett-Joyer-halenda (bjh) method.

FIG. 9 example of Fe₃XPS survey of C-Co/NC nanocomposites, where the table is the content of surface elements.

FIG. 10, Fe in the examples of the present invention₃XPS high resolution of Co in C-Co/NC nanocomposites.

FIG. 11, Fe in the examples of the present invention₃XPS high resolution of Fe in C-Co/NC nanocomposites.

FIG. 12 is a XPS high resolution plot of N in examples of the present invention, wherein the plot is a graph of the structure of different types of nitrogen atoms, tabulated as the relative amounts of the different types of nitrogen atoms.

FIG. 13 Fe in the example of the present invention₃Raman spectrum of C-Co/NC nano composite material.

FIG. 14, Fe₃C-Co/NC nanocomposites and Pt/C in N₂Or O₂CV curve in saturated 0.1M KOH.

FIG. 15 example of Fe₃The intermediate product content of the electrocatalytic ORR of C-Co/NC nanocomposites, inset is the number of transferred electrons.

FIG. 16, Fe in the example of the present invention₃Stability of ORR of C-Co/NC nanocomposites tested by the accelerated decay method.

FIG. 17 example of Fe₃Stability of ORR of C-Co/NC nanocomposites by chronoamperometry.

FIG. 18, Fe₃And (3) testing the methanol cross resistance of the C-Co/NC nano composite material and Pt/C.

FIG. 19 example of Fe₃Polarization curves for ORR and OER performance of C-Co/NC in 0.1M KOH solution.

FIG. 20, Fe₃C-Co/NC nanocompositeComposite material and RuO₂OER electrocatalytic performance of (a).

FIG. 21 example of Fe₃OER stability of the C-Co/NC nanocomposite material tested by chronopotentiometry.

FIG. 22, Fe₃HER electrocatalytic performance of C-Co/NC nanocomposites and Pt/C in 1M KOH solution.

FIG. 23 example of Fe₃Current-time plot of C-Co/NC nanocomposite in 1M KOH solution.

FIG. 24, Fe₃C-Co/NC nanocomposites and Pt/C at 0.5M H₂SO₄HER electrocatalytic performance in solution.

FIG. 25 example of Fe₃H of C-Co/NC nano composite material at 0.5M₂SO₄Current-time plot in solution.

The specific implementation mode is as follows:

the following will further describe specific contents and embodiments of the present invention with reference to examples, which are only examples for implementing the present invention and should not be construed as limiting the technical scope of the present invention.

Examples

The preparation process and steps in this example are as follows:

(1) adding 6g of P123, namely polyethylene oxide-propylene oxide-ethylene oxide and 14.5ml of concentrated hydrochloric acid with the concentration of 37 percent into 217ml of deionized water, adding 7.4ml of n-butyl alcohol, stirring at 35 ℃ for 1h, then dropwise adding 13.8ml of ethyl orthosilicate, and continuously stirring at 35 ℃ for 24 h; then transferring the mixture into a polytetrafluoroethylene reaction kettle, and reacting for 24 hours at the temperature of 100 ℃; centrifuging and washing the reacted solution by using water and ethanol, and performing vacuum drying for 24 hours at the temperature of 60 ℃; finally, annealing the obtained white powder in the air at 500 ℃ for 3h, and naturally cooling to room temperature;

(2) 0.118g of Co (NO)₃)₂·6H₂O、0.382g Fe(NO₃)₃·9H₂O, 5.44g of melamine, 1g of prepared mesoporous KIT-6 silicon template and 2.8g of P123 were added to 28ml of water and ethanolStirring for 3h and ultrasonic processing for 3h, respectively, then placing the mixed solution in a constant-temperature oil bath at 80 ℃, and continuously stirring strongly until the solution is completely evaporated to form solid powder;

(3) mixing the above powders with N₂Keeping the temperature at 500 ℃ for 2h under the environment, and then keeping the temperature at 850 ℃ for 5 h;

(4) corroding the heat-treated sample with 2M NaOH solution to remove the mesoporous KIT-6 template, centrifuging and washing with water and ethanol, and drying in a vacuum drying oven for 12h to obtain Fe₃C-Co/NC composite material.

(5) Iron carbide-cobalt/nitrogen doped carbon (Fe) obtained by the above preparation method₃C-Co/NC) nanocomposite material as an electrode material for electrochemical performance testing, comprising the following steps:

a. preparation of catalyst ink: respectively adding Fe₃C-Co/NC, commercial Pt/C and RuO₂Adding into 1ml naphthol/isopropanol water solution, and performing ultrasonic treatment for 30min to obtain catalyst ink;

b. preparation of a working electrode: taking out catalyst ink, dripping the catalyst ink on a glassy carbon electrode, and drying at room temperature to prepare a working electrode loaded with a catalyst;

c. the electrochemical test was carried out in a standard three-electrode test system, in which the electrode prepared in step b was used as the working electrode, the carbon rod as the counter electrode, the Ag/AgCl as the reference electrode, 0.1M KOH, 1M KOH or 0.5M H₂SO₄The solution is used as electrolyte tested in different solution environments;

d. with said Fe₃Testing the C-Co/NC composite material serving as a working electrode on an Ivium-n-Stat electrochemical workstation, converting all electrode potentials into reversible hydrogen electrode potentials, and normalizing the obtained current density to the geometric area of the working electrode; oxygen reduction reaction test in N₂Or O₂Saturated 0.1M KOH solution, and the intermediate product and the number of transferred electrons of the reaction are detected by a rotating disc ring electrode; for the oxygen evolution reaction, the catalyst loading was 0.4mg cm^-2(ii) a Electrocatalytic activity test of hydrogen evolution reaction at N₂Saturated 1M KOH or 0.5M H₂SO₄Is carried out in solution; the stability of the catalyst was tested using chronoamperometry or chronopotentiometry.

Fe₃The morphology and the structure of the C-Co/NC nano composite material are characterized in that:

the prepared KIT-6 template is shown in figure 2, shows the appearance characteristic of ordered porous, and the aperture is about 6-8 nm. Characterization of Fe by Transmission Electron microscopy₃Morphology of C-Co/NC. As shown in fig. 3, it can be seen that a large number of carbon nanotubes with diameters of several tens of nanometers are grown on the carbon nanosheets, and this unique structure integrating the one-dimensional carbon nanotubes and the two-dimensional carbon nanosheets helps to accelerate the transport of substances and electrons. FIG. 4 shows a broken carbon nanotube, and the nano-particles are present at the node junction of the bamboo joint. FIG. 5 is a high resolution photograph of black oval shaped areas inside carbon nanotubes, where the interplanar spacings of 0.213nm and 0.205nm correspond to Fe, respectively₃The (201) and (111) crystallographic planes of C and Co. FIG. 6 is Fe₃The XRD diffraction pattern of C-Co/NC, wherein the peak around 26 degrees is the diffraction peak position of typical graphite carbon. A series of peaks at 37.8 °, 43.9 °, 45.0 °, 46.0 ° and 49.2 ° correspond to orthorhombic Fe₃C. The weaker diffraction peaks at 44.1 ° and 51.6 ° are XRD peak positions of cubic Co, and the weaker peak intensity is due to the metal cobalt being coated with the carbon material. According to thermogravimetric analysis of fig. 7, the carbon content in the composite was about 75% by mass. N of FIG. 8₂The adsorption and desorption isotherms show that they are type IV (typical mesoporous type) isotherms. These mesopores are formed as a result of the KIT-6 template being removed. Fe₃BET specific surface area of C-Co/NC was 184.7m²g^-1The mesoporous aperture is mainly concentrated at about 3.9nm, and the total pore volume is 0.37cm³g^-1。Fe₃The C-Co/NC nanocomposite has a mesoporous structure and a higher specific surface area, which can not only increase the electrochemical active area by increasing the surface roughness, but also the existence of mesopores is beneficial to H generated on the electrode in HER and OER operations₂And O₂The elimination of bubbles, in turn, reduces ohmic drop. The electronic state and chemical composition of the catalyst surface are critical to understanding the catalytic performance. To this end, we are right toComposite material Fe₃XPS analysis was performed for C-Co/NC as shown in FIGS. 9 to 12. The full spectrum of FIG. 9 contains peaks for C, Co, Fe, N, O and Si. Based on XPS data analysis, the surface atomic percentages of the composite material were: c (82.7 at%), Co (0.2 at%), Fe (0.4 at%), N (3.5 at%), O (10.8 at%) and Si (2.4 at%). The elements Si and O contained in the sample come from residual SiO in KIT-6₂. It can be seen from the XPS spectrum that the characteristic peak intensities of Fe and Co are very weak and their contents are almost negligible compared to other elements. This indicates that Fe₃C and Co are almost completely encapsulated in the carbon material. Fig. 10 and 11 are high resolution XPS spectra of Co 2p and Fe 2p, respectively, due to the surface oxidation of the composite material when exposed to air. The high resolution spectrum of N1 s in FIG. 12 can be divided into two peaks, pyridine nitrogen (. about. 398.5eV) and pyrrole nitrogen (. about.400.6 eV), corresponding to nitrogen contents of 56.9% and 43.1%, respectively. The inset in figure 12 is a schematic representation of two different types of nitrogen. FIG. 13 is a Raman spectrum at 1350cm^-1And 1594cm^-1The two peak positions are the D band and the G band of carbon respectively. I is_D:I_GThe graphite powder is 0.94, which shows that the composite material has higher graphitization and shows better conductivity.

At room temperature, Fe₃The electrochemical performance of the C-Co/NC composite material is characterized in that:

as shown in FIG. 14, at 50mV s^-1In the process of sweeping in the cathode direction at a sweeping speed of Fe₃CV curves for C-Co/NC and commercial Pt/C at N₂Almost no significant peak appears in the saturated electrolyte, but in O₂A very pronounced reduction peak in the saturated electrolyte appeared, indicating that the catalytic activity of both catalysts is due to the oxygen reduction reaction. Fe₃The oxygen reduction electrocatalytic performance of C-Co/NC and commercial Pt/C (20%) was characterized by loading them on a glassy carbon electrode in 0.1M KOH solution saturated with oxygen. The polarization curve is O₂In a saturated 0.1M KOH solution, at 1600rpm, the potential is from 1.1V to 0.2V with 10mV s^-1The sweep rate of (2) is measured. As shown in FIG. 1, Fe₃The half-wave potential of the C-Co/NC catalyst was 0.885V, ratio commercial Pt/C (half-wave potential)Wave potential of 0.812V) half-wave potential correction of the catalyst by 73 mV. And Fe under the same conditions₃C-Co/NC has larger limit diffusion current density of 5.5mAcm^-2And commercial Pt/C of 4.8mA cm^-2. To obtain the conversion efficiency of the oxygen reduction reaction and to explore its mechanism, we performed a rotating disk ring electrode test, in which the intermediate product HO was produced₂ ^-The content of (A) is less than 10% in the range of 0.2V-0.8V. The inset in FIG. 15 shows that the electron transfer number is 3.9, close to theoretical 4, demonstrating Fe₃The C-Co/NC catalyst has better 4 electron selectivity. To further detect Fe₃Stability of C-Co/NC As shown in FIG. 16, 10000 cycles of current-voltage cycling were performed between 0.4V and 1.1V using an accelerated decay method. The half-wave potential of the electrode has attenuation of only 3mV, and the limit diffusion current density has attenuation of only 7.2%. Fe₃The stability of C-Co/NC was again checked by chronoamperometry, as shown in FIG. 17. Fe after 60000s duration of the test with the electrode potential held at 0.7V₃The current retention of C-Co/NC was 92%, further illustrating its excellent stability. To study Fe₃The methanol crossover resistance of the C-Co/NC catalyst, which was tested by chronoamperometry in a 10% volume methanol solution, is shown in FIG. 18. The current density of commercial Pt/C showed at least a 31.5 percent loss when methanol was added to the electrolyte, indicating that methanol was oxidized at the electrode. And Fe₃C-Co/NC showed a relative current loss of up to 1.8% in the presence of methanol, indicating that the catalyst has better methanol crossover resistance than Pt/C.

We further tested Fe in 1M KOH solution saturated with oxygen₃OER electrocatalytic performance of C-Co/NC. As shown in FIG. 19, Fe₃C-Co/NC at a current density of 10mA cm^-2The overpotential at this time was only 340 mV. Commercial RuO at the same catalyst loading₂The overpotential of (2) is 360 mV. Thus, Fe₃The C-Co/NC has lower over potential, and the excellent electrocatalytic activity of the C-Co/NC is mainly derived from Fe₃The C-Co/NC hierarchical structure can introduce more available active sites toAnd can accelerate the transport of the substance. FIG. 20 is Fe₃The stability test result of OER of C-Co/NC, through the timing potential test of lasting 60000s, the potential after the test has only 18mV increase compared with the initial potential, which shows that the OER has better stability. In view of Fe₃C-Co/NC has excellent oxygen electrode catalytic activity, and we further tested the catalytic activity on hydrogen evolution reaction in different pH environments. FIG. 21 shows the use of a rotating disk electrode under alkaline conditions at N₂Polarization profile of the test in saturated 1M KOH solution from which Fe can be derived₃The initial potential of C-Co/NC was 83mV, which is relatively close to that of commercial Pt/C (0 mV). In addition, Fe₃C-Co/NC at a current density of 10mA cm^-2The overpotential at this time was 238 mV. Fe₃The stability of C-Co/NC was measured by chronoamperometry while maintaining the electrode potential at 238mV, as shown in FIG. 22. Fe₃The current density decayed 17.7% compared to the initial value when tested by C-Co/NC at 60000s duration of current-time. Similar to under alkaline conditions, fig. 23 is a polarization curve measured under acidic conditions. Fe can be obtained₃The initial potential of C-Co/NC was 186mV and the current density was 10mA cm^-2The overpotential at time was 298 mV. Fe in FIG. 24₃The current density of C-Co/NC decays by only 5.4% compared to the initial value after the current-time test of 60000s duration, which indicates that it has excellent stability also in an acidic environment. Fe₃The OER and ORR dual-functional catalytic activity of C-Co/NC can be measured by the oxygen electrode activity parameter Delta E (Delta E ═ E)_j＝10,OER-E_1/2,ORR) To characterize. The delta E value of the catalyst is only 0.72V (figure 25), which shows that the catalyst has excellent bifunctional catalytic activity and has good application prospect in rechargeable zinc-air batteries.

The invention provides a method for preparing Fe by a sacrificial template method₃A method for preparing C nano particle-Co nano particle/nitrogen doped carbon nano composite material. In this composite, nitrogen-doped carbon not only improves the electrical conductivity and corrosion resistance of the composite, but also introduces more defects to provide catalytically active sites. The hierarchical structure of the porous carbon nanotube and the nanosheet improves the electron content in the carbon structureA migration rate; and on the other hand, the transmission of substances among the porous unstacked nano-sheets is accelerated. Fe encapsulated in hierarchical carbon nanomaterials₃The C and Co nanoparticles can effectively regulate and control the electronic structure around carbon, and the carbon structure in turn improves Fe₃The dispersity and the utilization efficiency of C and Co form a synergistic effect, and the catalytic reaction is further accelerated. The composite material is used as a catalyst for oxygen reduction reaction and water decomposition reaction, and shows excellent catalytic performance. The invention provides a new idea for reasonably designing and constructing the multifunctional electrocatalyst.

Claims (1)

1. A preparation method of an iron carbide-cobalt/nitrogen doped carbon nano composite material comprises the following steps:

a. constructing a KIT-6 silicon template: adding 5-7 g of P123, namely polyethylene oxide-propylene oxide-ethylene oxide and 14-15 ml of 37% hydrochloric acid solution into 210-220 ml of deionized water, adding 7-8 ml of n-butyl alcohol, stirring at 30-40 ℃ for 1-2 h, then dropwise adding 13-14 ml of ethyl orthosilicate, and continuously stirring at 30-40 ℃ for 24 h; then transferring the mixture into a polytetrafluoroethylene reaction kettle, and reacting for 20-24 hours at the temperature of 100-120 ℃; centrifuging and washing the reacted solution by using water and ethanol, and drying the solution in vacuum at the temperature of 60-80 ℃ for 20-24 hours; finally, annealing the obtained white powder in air at 500-800 ℃ for 3-5 h, and naturally cooling to room temperature;

b. 0.1-0.2 g of Co (NO)₃)₂·6H₂O、0.3～0.4g Fe(NO₃)₃·9H₂Adding O, 5-6 g of melamine, 1-1.5 g of prepared mesoporous KIT-6 silicon template and 2-3 g of P123 into 20-30 ml of mixed solution of water and ethanol, respectively stirring for 2-3 h and carrying out ultrasonic treatment for 2-3 h, and then continuously stirring the mixed solution strongly in a constant-temperature oil bath at the temperature of 60-80 ℃ until the mixed solution is completely evaporated to obtain solid powder;

c. adding the solid powder of step b in N₂Preserving heat for 2-3 h at 400-500 ℃ in the environment, and then preserving heat for 4-5 h at 800-900 ℃;

d. 2-3M of the heat-treated sampleCorroding with NaOH solution to remove the mesoporous KIT-6 template, centrifuging and washing with water and ethanol, and vacuum-drying at 60-80 ℃ for 10-12 h to obtain Fe₃C-Co/NC composite material.

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