Fe3C and MnO composite FeNC composite material prepared by self-sacrifice template method and application of Fe3C and MnO composite FeNC composite material

Abstract

The invention belongs to the field of nano material preparation, and discloses a Fe3C and MnO composite FeNC composite material as well as a preparation method and application thereof. The bimetallic composite Fe3C and MnO composite FeNC catalyst with a large specific surface area is prepared through simple one-step pyrolysis by a self-sacrifice template method. The optimized Fe3C and MnO composite FeNC shows excellent bifunctional activity and long-term cycle stability in an alkaline electrolyte, the E1 / 2 value of ORR is 0.84 V, the Ej = 10 value of OER is 1.62 V, and the corresponding delta E value is 0.78 V. The invention further discloses a preparation method of the composite FeNC. The Fe3C and MnO composite FeNC composite material prepared by a self-sacrifice template method has a large specific surface area, the doping of MnO can adjust the electronic structure of the catalyst, and the Fe3C and MnO composite FeNC as an electrocatalyst of an air cathode in rechargeable ZABs shows excellent battery performance in a liquid form, and can be stably charged and discharged for 800 hours under 10mA cm <-2 >.

Description

Technical Field

[0001] The invention belongs to the field of nano material preparation, and specifically relates to a Fe3C and MnO composite FeNC composite material prepared by a self-sacrificial template method and application thereof. Background Art

[0002] As the energy crisis intensifies, renewable energy plays an extremely important role in the energy economic transformation, including hydrogen energy. For hydrogen, the electrolysis of water to produce hydrogen is currently a relatively mature and efficient preparation method. In the energy economic transformation, batteries, as energy storage media, are also of paramount importance. Among them, zinc-air batteries (ZABs) have the advantages of high energy density, green safety, and low cost. However, the complex multi-electron and multi-phase transfer processes on the air cathode lead to slow kinetics of the cathode oxygen reduction reaction (ORR) and the anode oxygen evolution reaction (OER), which limits the production and use of zinc-air batteries. Therefore, the development of suitable bifunctional catalysts is a necessary condition for the development of zinc-air batteries. At present, the most advanced ORR catalyst is a precious metal platinum (Pt)-based nanomaterial, and the OER catalyst is ruthenium (Ru) / iridium (Ir), but its high cost hinders the commercial preparation and use of the catalyst. Therefore, researchers are also committed to the development of low-cost and efficient non-precious metal bifunctional catalysts.

[0003] Compared with precious metal catalysts, iron-based catalysts have also attracted more attention from researchers, with advantages such as excellent catalytic activity, abundant natural reserves, multiple electron valence states and adjustable electronic structure. The template synthesis process is simple, and the microscopic shape, size, properties and structure of the catalyst can be precisely controlled to meet the required performance requirements. As an electrocatalytic material, it has great application prospects in zinc-air batteries, water electrolysis and other fields. Summary of the invention

[0004] In order to overcome the above-mentioned shortcomings and deficiencies of the prior art, the primary purpose of the present invention is to provide a method for preparing a Fe3C and MnO composite FeNC composite material prepared by a self-sacrificial template method as a bifunctional catalyst.

[0005] Another object of the present invention is to provide a Fe3C and MnO composite FeNC composite material prepared by the above method.

[0006] Another object of the present invention is to provide the application of the Fe3C and MnO composite FeNC composite material prepared by the above method in zinc-air batteries.

[0007] The purpose of the present invention is achieved through the following solutions: A method for preparing a Fe3C and MnO composite FeNC composite material prepared by a self-sacrificial template method, characterized by comprising the following steps: (1) Mix melamine and cyanuric acid evenly and dissolve them in DMSO solution, stir vigorously and filter and dry to obtain product 1; (2) Grind the product 1 and add deionized water. After vigorous stirring, add dopamine hydrochloride, concentrated ammonia, Fe(NO3)3·9H2O and MnCl2, stir and polymerize, filter, wash and dry to obtain the product 2; (3) After grinding the product 2, the product was calcined at a high temperature in a N2 atmosphere to obtain the final product Fe3C and MnO composite FeNC composite material; In step (1), the amount of melamine and cyanuric acid added is 1-4 mol, the concentration of DMSO is 99%, the amount added is 10-15 mL, the treatment time is 8-12 minutes, the drying temperature is 60-80°C, and the drying time is 1-6 hours; In step (2), the amount of deionized water added is 150-200 mL, the amount of dopamine hydrochloride added is 0.3-0.4 g, the amount of concentrated ammonia water added is 0.25-0.3 mL, the amount of Fe(NO3)3·9H2O added is 30-60 mg, the amount of MnCl2 added is 10-30 mg, and the polymerization time is 20-25 hours.

[0008] In step (3), the calcination temperature is 800-900°C, and the calcination time is 1.5-3 hours.

[0009] A Fe3C and MnO composite FeNC composite material prepared by the method.

[0010] The Fe3C and MnO composite FeNC composite material prepared by the above method is used as a bifunctional catalyst in zinc-air batteries.

[0011] Compared with the prior art, the present invention has the following advantages and beneficial effects: 1. The raw materials of the present invention are abundant in source, low in cost, simple in preparation process, short in experimental cycle and high in repeatability.

[0012] 2. The Fe3C and MnO composite FeNC composite prepared by the present invention has excellent bifunctional catalytic performance. In an O2-saturated 0.1 M KOH solution, the E of ORR is 1 / 2 The value is 0.84 V, the Ej=10 value of OER is 1.62 V, and the corresponding ΔE value is 0.78 V at 10 mA cm -2Under the conditions of 1.7 V, the charge and discharge cycle can be as long as 800 h. The Fe3C and MnO composite FeNC maintained 97.42% of the initial current density within 12 hours. After testing at a voltage of 1.7 V for 12 hours, the current density of the Fe3C and MnO composite FeNC only decreased by 11.82%, indicating that the Fe3C and MnO composite FeNC has good durability and stability.

[0013] 3. Fe3C and MnO composite FeNC as electrocatalysts for the air cathode in rechargeable ZABs exhibit excellent battery performance in liquid form. The ZAB based on Fe3C and MnO composite FeNC exhibits a high open circuit voltage of 1.55 V and a peak power density of 164.7 mW cm -2 , indicating that Fe3C and MnO composite FeNC has excellent energy conversion efficiency in ZABs. The discharge current density is from 1 mA cm -2 Up to 10 mA cm -2 When the current density is restored to 1, the ZAB based on Fe3C and MnO composite FeNC can operate stably for 800 h, showing long-term cycle stability.

[0014] 4. The active center is Fe3C, and the active centers such as Fe-Nx, pyridine N and graphite N are evenly distributed. It presents a flower-like appearance. It is a microsphere structure composed of many nanoplates. Its structure is uniform, and the metal nanoparticles are evenly dispersed on the nanosheets. MnO doping increases the degree of defects in the carbon matrix. The high degree of defects can increase the abundance of oxygen reaction sites and electron migration rate during the battery charge and discharge process, thereby improving the electrocatalytic activity. The hierarchical porous structure facilitates the diffusion of gases and the flow of electrolytes. This enhances the contact between the active sites and the electrolyte, thereby improving the catalytic activity of the catalyst.

[0015] 5. The present invention also discloses the application of Fe3C and MnO composite FeNC as an electrocatalyst of the air cathode in rechargeable ZABs in flexible zinc-air batteries, and can also be applied in the field of water electrolysis. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 This is a synthesis flow chart of the Fe3C and MnO composite FeNC composite material prepared in Example 1.

[0017] Figure 2X-ray diffraction patterns and Raman spectra of Fe3C and MnO composite FeNC prepared in Examples 1, 2 and 3 and Fe3C@FeNC prepared in Comparative Example 1, wherein: (a) XRD pattern of Fe3C and MnO composite FeNC prepared in Example 1 and Fe3C@FeNC prepared in Comparative Example 1, (b) XRD pattern of Fe3C and MnO composite FeNC prepared in Examples 1, 2 and 3, (c) Raman spectrum of Fe3C and MnO composite FeNC prepared in Example 1 and Fe3C@FeNC prepared in Comparative Example 1, (d) Raman spectrum of Fe3C and MnO composite FeNC prepared in Examples 1, 2 and 3.

[0018] Figure 3 N2 adsorption-desorption curves and pore size distribution diagrams of the Fe3C and MnO composite FeNC prepared in Example 1 and the Fe3C@FeNC prepared in Comparative Example 1, wherein (a) is the N2 adsorption-desorption curve diagram, and (b) is the pore size distribution diagram.

[0019] Figure 4 These are X-ray photoelectron spectra of the Fe3C and MnO composite FeNC prepared in Example 1 and the Fe3C@FeNC prepared in Comparative Example 1, where (a) corresponds to C 1s, (b) corresponds to N 1s, (c) corresponds to Fe 2p, and (d) corresponds to Mn 2p.

[0020] Figure 5 The transmission electron microscope (TEM), high-resolution transmission electron microscope (HRTEM), scanning electron microscope (SEM) and EDS element mapping images of MCA prepared before polymerization in Example 1 and Fe3C and MnO composite FeNC prepared in Example 1. Among them, (a) is the SEM image of MCA, (b) is the SEM image of Fe3C and MnO composite FeNC, (c) is the TEM image of Fe3C and MnO composite FeNC, (d), (e) and (f) are HRTEM images of Fe3C and MnO composite FeNC, and (g) is the EDS element mapping image of Fe3C and MnO composite FeNC.

[0021] Figure 6The ORR electrochemical performance of Fe3C and MnO composite FeNC prepared in Examples 1, 2 and 3 and Fe3C@FeNC prepared in Comparative Example 1 is characterized, wherein (a) is the cyclic voltammetry (CV) curve of Fe3C and MnO composite FeNC and Fe3C@FeNC under O2 saturated conditions, (b) is the linear sweep cyclic voltammetry (LSV) curve of Fe3C and MnO composite FeNC, Fe3C@FeNC and 20% Pt / C; (c) is the Tafel plot; (d) is the linear sweep cyclic voltammetry (LSV) curve of Fe3C and MnO composite FeNC prepared in Examples 1, 2 and 3.

[0022] Figure 7 The OER electrochemical performance of Fe3C and MnO composite FeNC prepared in Example 1 and Fe3C@FeNC prepared in Comparative Example 1 is characterized, wherein (a) is the OER electrochemical performance of Fe3C@FeNC prepared in an oxygen-saturated 1.0 M Linear sweep cyclic voltammetry (LSV) curves in KOH electrolyte; (b) is the Tafel plot. (c) is the linear sweep cyclic voltammetry (LSV) curves of Fe3C and MnO composite FeNC prepared in Examples 1, 2, and 3.

[0023] Figure 8 The electrochemical performance of Fe3C and MnO composite FeNC prepared in the example as a bifunctional electrocatalyst is characterized. Figure (a) is the chronoamperometric curve at 0.5 V, and (b) is the chronoamperometric curve at 1.7 V.

[0024] Fig. 9 This is a constant current charge and discharge test of the zinc-air battery based on Fe3C and MnO composite FeNC prepared in Example 1. DETAILED DESCRIPTION

[0025] The present invention is further described in detail below in conjunction with the examples and drawings, but the embodiments of the present invention are not limited thereto. If no specific conditions are specified in the examples, the conditions are carried out according to conventional conditions or conditions recommended by the manufacturer. If the manufacturer of the reagents or instruments used is not specified, they are all conventional products that can be purchased commercially. Example 1

[0026] A Fe3C and MnO composite FeNC composite material prepared by a self-sacrificial template method comprises the following steps: (1) Mix 2 mmol of melamine and 2 mmol of cyanuric acid evenly and dissolve them in 15 mL of DMSO solution. Stir vigorously for 10 min, filter and dry to obtain melamine cyanuric acid complex (MCA).

[0027] (2) Grind the product filtered and dried in step (1) into fine powder, add 200 mL of deionized water, add 0.30 g of dopamine hydrochloride (DA), 0.25 mL of concentrated ammonia, 50 mg of Fe(NO3)3·9H2O and 15 mg of MnCl2 under vigorous stirring, stir at room temperature, and polymerize for 24 h to obtain MCA coated with metal salt composite polydopamine (PDA), which is then filtered, washed and dried.

[0028] (3) After grinding the product obtained in (2), the temperature was raised to 800 °C in a N2 atmosphere and calcined for two hours. The obtained product was recorded as Fe3C and MnO composite FeNC-2 Example 2

[0029] A method for preparing a Fe3C and MnO composite FeNC composite material prepared by a self-sacrificial template method comprises the following steps: (1) Mix 2 mmol of melamine and 2 mmol of cyanuric acid evenly and dissolve them in 15 mL of DMSO solution. Stir vigorously for 10 min, filter and dry to obtain melamine cyanuric acid complex (MCA).

[0030] (2) Grind the product filtered and dried in step (1) into fine powder, add 200 mL of deionized water, add 0.30 g of dopamine hydrochloride (DA), 0.25 mL of concentrated ammonia water, 50 mg of Fe(NO3)3·9H2O and 5 mg of MnCl2 under vigorous stirring, stir at room temperature, and polymerize for 24 h to obtain MCA coated with metal salt composite polydopamine (PDA), which is then filtered, washed and dried.

[0031] (3) The product obtained in (2) was ground, heated to 800 °C in a N2 atmosphere, and calcined for two hours to obtain Fe3C and MnO composite FeNC-1. Example 3

[0032] A method for preparing a Fe3C and MnO composite FeNC composite material prepared by a self-sacrificial template method comprises the following steps: 1) Mix 2 mmol melamine and 2 mmol cyanuric acid evenly and dissolve them in 15 mL DMSO solution. Stir vigorously for 10 min, filter and dry to obtain melamine cyanuric acid complex (MCA).

[0033] (2) Grind the product filtered and dried in step (1) into fine powder, add 200 mL of deionized water, add 0.30 g of dopamine hydrochloride (DA), 0.25 mL of concentrated ammonia, 50 mg of Fe(NO3)3·9H2O and 25 mg of MnCl2 under vigorous stirring, stir at room temperature, and polymerize for 24 h to obtain MCA coated with metal salt composite polydopamine (PDA), which is then filtered, washed and dried.

[0034] (3) After grinding the product obtained in (2), the temperature was raised to 800 °C in a N2 atmosphere and calcined for two hours to obtain Fe3C and MnO composite FeNC-3.

[0035] Comparative Example 1 The preparation of Fe3C@FeNC refers to the preparation method of Example 1, and no MnCl2 needs to be added during the synthesis process.

[0036] Preparation of RuO2 and 20% Pt / C First, 5 mg RuO2 and 20% Pt / C were added to 0.5 mL of the mixed solution (V 蒸馏水 :V 乙醇 = 3:7) and 20 μL 5% Nafion solution, ultrasonic dispersion for more than 30 min to obtain a uniformly dispersed suspension. Finally, 10 μL of the suspension was evenly dropped on the surface of the rotating disk electrode and dried at room temperature to obtain RuO2 and 20% Pt / C.

[0037] The materials studied in this invention were tested for oxygen reduction performance on a Shanghai Chenhua electrochemical workstation (CHI 660D). During the test, a catalyst-coated rotating disk electrode (RDE) was used as the working electrode, a platinum sheet (1 cm× 1 cm) was used as the counter electrode, and Ag / AgCl was used as the reference electrode. During the experiment, an O2-saturated 0.1 M KOH solution was selected as the electrolyte. All data obtained were expressed in terms of relative reversible hydrogen electrode (RHE). Cyclic voltammetry (CV) was used to evaluate the oxygen reduction ability of the material, while linear sweep voltammetry (LSV) was used to obtain the polarization curves of the catalyst at different rotation speeds (400 ~ 2025 rpm). The oxygen evolution performance of the materials was tested on a CHI 660D. The working electrode was a catalyst-coated glassy carbon electrode, the reference electrode was Hg / HgO, and the counter electrode was a graphite rod. 0.1 M KOH filled with O2 was used as the electrolyte for the test. LSV test was used to determine the polarization curve of the catalyst. dl) is obtained by performing CV scan tests on the non-Faraday region under different scan rate conditions. All test data are converted into potential relative to the reversible hydrogen electrode (RHE). Therefore, the potential conversion formula is: E RHE = ( E SCE + 0.2415 V +0.059pH) V. The electrochemical stability of the samples was measured by chronoamperometry, which evaluates the durability and corrosion resistance of the catalyst by recording the change in current over a period of time, usually several hours.

[0038] 1. About Example 1 and Comparative Example 1 Figure 1 This is a synthesis flow chart of the Fe3C and MnO composite FeNC composite material prepared in Example 1.

[0039] Figure 2 X-ray diffraction patterns and Raman spectra of the Fe3C and MnO composite FeNC prepared in Example 1 and the Fe3C@FeNC prepared in Comparative Example 1. From Figure (a), characteristic peaks of amorphous carbon, Fe3C, and MnO can be seen, indicating that amorphous carbon, Fe3C, and MnO phases exist in the Fe3C and MnO composite FeNC.

[0040] Figure 3 The N2 adsorption-desorption curves and pore size distribution of Fe3C and MnO composite FeNC prepared in Example 1 and Fe3C@FeNC prepared in Comparative Example 1. The N2 adsorption-desorption isotherms of Fe3C and MnO composite FeNC indicate the existence of its mesoporous structure. The widely dispersed MnO nanoparticles hinder the close packing of the carbon layer and form more porous structures. In the electrocatalytic process, the hierarchical porous structure facilitates the diffusion of gas and the flow of electrolyte, which enhances the contact between the active sites and the electrolyte, thereby improving the catalytic activity of the catalyst. Figure 4 for Figure 4 The X-ray photoelectron energy spectra of the Fe3C and MnO composite FeNC prepared in Example 1 and the Fe3C@FeNC prepared in Comparative Example 1. (b) shows that the total content of pyridinic nitrogen, graphitic nitrogen and Fe-N in the Fe3C and MnO composite FeNC sample is significantly higher than that in Fe3C@FeNC. Pyridinic nitrogen is an active substance for ORR, and Fe-N provides an effective metal active center in electrocatalysis, thereby improving the ORR activity. The presence of graphitic nitrogen indicates the successful generation of nitrogen-doped carbon materials. The doping of nitrogen can affect the electronic structure of the carbon skeleton, thereby enhancing the conductivity of the sample.

[0041] Figure 5Transmission electron microscope (TEM), high-resolution transmission electron microscope (HRTEM), scanning electron microscope (SEM), and EDS element mapping images of the Fe3C and MnO composite FeNC prepared in Example 1. Figure (b) shows a flower-like structure with a diameter of 2~2.5μm. Figures (c) and (d) show that each microsphere is a hollow structure constructed by nanosheets, and the metal nanoparticles are evenly distributed on the nanosheets. Figures (e) and (f) show that the carbon layer covers the metal nanoparticles. Figure (g) shows that the elements in the Fe3C and MnO composite FeNC are evenly distributed.

[0042] Figure 6 The ORR electrochemical performance of Fe3C and MnO composite FeNC prepared in Examples 1, 2, and 3 and Fe3C@FeNC prepared in Comparative Example 1 is characterized. Figure (a) shows that Fe3C and MnO composite FeNC has a more positive starting potential, indicating that its ORR catalytic activity is better. Figure (b) shows that Fe3C and MnO composite FeNC has a better half-wave potential and a larger limiting current density. Figure (c) shows that the Tafel slope of Fe3C and MnO composite FeNC (88.80 mV dec -1 ) is better than Fe3C@FeNC (116.01mV dec -1 ), and the ORR reaction kinetics of Fe3C and MnO composite FeNC is close to that of precious metals.

[0043] Figure 7 The ORR electrochemical performance of Fe3C and MnO composite FeNC prepared in Example 1 and Fe3C@FeNC prepared in Comparative Example 1 is shown in Figure (a). It can be seen that Fe3C and MnO composite FeNC drives 10 mA cm -2 The current only requires an overpotential of 390 mV. Figure (b) shows that the Tafel slope of Fe3C and MnO composite FeNC (103.84 mV dec -1 ) is lower than Fe3C@FeNC (368.29 mV dec -1 ), indicating that it has good OER reaction kinetics.

[0044] II. About Examples 1, 2, and 3 In order to explore the effect of MnCl2 addition on the ORR performance of the material, Figure 6 Fe3C and MnO composite FeNC-2, Fe3C and MnO composite FeNC-1, and Fe3C and MnO composite FeNC-3 prepared in Examples 1, 2, and 3. As can be seen in Figure (d), when the addition amount of MnCl2 is 15 mg, the sample exhibits the best performance.

[0045] At the same time, in order to explore the effect of MnCl2 addition on the OER performance of the material, Figure 7 The LSV curves for measuring the OER with different manganese addition amounts show that the sample exhibits the best performance when the MnCl2 addition amount is 15 mg.

Claims

1. A method for preparing a Fe3C and MnO composite FeNC composite material prepared by a self-sacrificial template method, characterized in that The following steps are involved: (1) Mix melamine and cyanuric acid evenly and dissolve them in DMSO solution, stir vigorously and filter and dry to obtain product 1; (2) Grind the product 1 and add deionized water. After vigorous stirring, add dopamine hydrochloride, concentrated ammonia, Fe(NO3)3·9H2O and MnCl2, stir and polymerize, filter, wash and dry to obtain the product 2; (3) After grinding the product 2, the product was calcined at a high temperature in a N2 atmosphere to obtain the final product, Fe3C and MnO composite FeNC composite material.

2. The method for preparing the Fe3C and MnO composite FeNC composite material according to claim 1, characterized in that: In step (1), the volume fraction of the DMSO solution is 99%, the treatment time is 10 to 15 minutes, the drying temperature is 60 to 80°C, and the drying time is 1 to 6 hours.

3. The method for preparing the Fe3C and MnO composite FeNC composite material according to claim 1, characterized in that: In step (2), the amount of deionized water added is 150-200 ml, the amount of dopamine hydrochloride added is 0.3-0.4 g, the amount of concentrated ammonia water added is 0.25-0.3 ml, the amount of Fe(NO3)3·9H2O added is 30-60 mg, the amount of MnCl2 added is 10-30 mg, and the polymerization time is 20-25 hours.

4. The method for preparing the Fe3C and MnO composite FeNC composite material according to claim 1, characterized in that: In step (3), the calcination temperature is 800-900°C, and the calcination time is 1.5-3 hours.

5. The Fe3C and MnO composite FeNC composite material according to claim 1 can be used as a bifunctional catalyst in zinc-air batteries and can also be used in the field of water electrolysis.

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