Iron Selenide-Carbon-Based Material Bifunctional Catalyst and Preparation Method Thereof

Abstract

The present invention discloses a bifunctional catalyst of iron selenide / carbon-based material and a preparation method thereof. In the method, ferric chloride and 2-aminoterephthalic acid are ultrasonically dissolved in DMF, and after a mixing reaction, a sodium hydroxide solution is added, and a hydrothermal reaction is carried out to obtain a dispersion liquid of NH2-MIL-88B(Fe) precursor, and then a selenious acid solution is added, and a stirring reaction is carried out to obtain NH2-MIL-88B(Fe)-SeO3 2‑ polymer precursor. Finally, under a protective atmosphere, the polymer precursor is calcined to obtain an FeSe x / Fe2O3@C bifunctional catalyst. The bifunctional catalyst of the present invention is composed of iron oxide wrapped by carbon and a heterostructure of iron triselenide / iron selenide formed by carbonization, and can be used as an efficient oxygen reduction functional catalyst, having excellent catalytic performance and electrochemical durability, with a starting potential of 0.928 V, a half-wave potential of 0.770 V and a limiting current density of 5.30 mA cm ‑2 The limiting current density is better than that of commercial Pt / C in performance.

Description

Technical Field

[0001] The present invention belongs to the field of catalyst materials, and relates to a bifunctional catalyst of iron selenide carbon-based material and a preparation method thereof. Background Art

[0002] As an electrochemical energy conversion system, fuel cells have become one of the most promising technologies in sustainable energy conversion systems. Among them, the oxygen reduction reaction (ORR) on the cathode plays a key role in the performance of fuel cells. The most commonly used ORR electrocatalyst is still platinum particles supported on porous carbon materials (Pt / C), but its poor long-term durability, such as dissolution, methanol crossover and high cost, has hindered its large-scale commercial application. Therefore, the rational design of non-noble metal catalysts with unique structures to significantly improve the catalytic activity of catalysts has attracted much attention.

[0003] Metal-organic framework materials (MOFs) are a new type of porous material with an adjustable framework structure formed by bridging metal ions or metal clusters with organic ligands. Their characteristics such as high specific surface area and rich porosity make them a hard template for porous carbon materials or catalyst precursors and highly competitive in serving as ORR catalysts (Advanced Materials, 2012, 24: 1399-1404). For example, NH2-MIL88B(Fe) in Fe-MOF has been widely used in the catalytic field (Advanced Materials, 2015, 27: 2521-2527). Fe-MOF is a member of a subset of larger porous frameworks connected by trivalent metals, and these frameworks are generally more robust compared to most MOFs containing divalent metal cations (Science, 2007, 315: 1828-1831). MOF materials include pristine metal oxides, metal oxide composites, and their derivatives. Due to their ordered crystal structure and coordination form, metal ions are evenly distributed in the materials, effectively solving the problems of uneven distribution of metal ions on the surface of carbon materials and insufficient catalytic efficiency. MOF-derived carbon-based ORR electrocatalysts can be further divided into two categories: defective pure carbon materials and heteroatom-doped carbon materials. Doping heteroatoms is an attractive strategy as it not only generates defects but also easily causes changes in the electronic structure of the surrounding carbon materials, thus introducing more active sites. Adding heteroatoms such as N, P, S, Se, etc. to the catalyst will also improve the performance of the catalyst. The main reason is that the introduction of these heteroatoms can change the electronic energy state of the catalyst itself, forming more surface defects, thereby promoting the catalytic reduction process. Therefore, for heteroatom-doped transition metal carbons, such as M-N-C catalysts obtained from the pyrolysis of metal macrocycles, metal or metal carbide particles are encapsulated in the carbon material (Advanced Function Mater. 2021, 31, 2009645). Although these particles do not come into contact with oxygen molecules, the charge transfer between the encapsulated metal / metal carbide and the carbon surface promotes oxygen adsorption. At the same time, due to the protection of the outer carbon layer, the encapsulated particles are more stable in acidic media.

[0004] Transition metal compounds, including metal oxides, sulfides, phosphides, and selenides, can easily form stable coordination compounds with ligands due to the lone pair d electrons in transition metal atoms or ions, available empty d orbitals for bonding, and high charge / radius. This makes it easy to form electron defects, so it exhibits strong activity in many fields and is an ideal catalytic component. As emerging functional materials, transition metal dichalcogenides (TMDSs) exhibit excellent electrochemical properties due to their unique graphene-like two-dimensional layered structure, high conductivity, excellent activity, and low reaction energy barrier, and have broad application prospects in fields such as photocatalysis, hydrogen evolution supercapacitors, and fuel cells. In fact, compared with oxygen (3.5) and sulfur (2.5), the lower electronegativity of selenium (2.4) results in relatively weaker chemical bonds between selenium atoms and their bonding electrons. Therefore, metal selenides usually exhibit higher activity in electrochemical reactions. Currently, the relatively traditional way to prepare TMDSs is mainly to mix selenium powder and iron powder. For example, by mixing iron and selenium elements in this way and carbonizing them for 2 hours under N2 flow conditions at 800, 850, 900, and 950 °C, Fe3Se4 / FeSe / NPGC-x is formed. After testing, this material has excellent ORR performance, but the catalyst prepared by this method requires a corn cob reaction to provide a carbon source, and the preparation process is complex (Applied Catalysis B: Environmental 244 (2019) 465–474). Some studies have shown that MOF derivatives of transition metal selenides can be produced by direct high-temperature calcination of MOF precursors and selenium powder. For example, Zhao et al. used ZIF-67 and selenious acid-assisted etching to form transition metal selenides, which improved the conductivity, made the OER electrocatalyst have excellent activity and good durability, and reflected the influence of selenium on the electrochemical activity of the catalyst (Advanced Energy Materials, 2016, 6: 1600458). Based on this, metal-organic frameworks (MOFs) have become the focus of research due to their high porosity and specific surface area, and their hard-template porous carbon materials or precursor metal-nitrogen-carbon catalysts exhibit excellent enhanced catalytic activity. In recent years, transition metal selenides derived from MOFs have been considered a promising electrocatalyst due to their large exposed surface area, abundant active sites, and the inherent high conductivity of transition metal selenides. Summary of the Invention

[0005] The purpose of the present invention is to provide a bifunctional catalyst of iron selenide carbon-based material and its preparation method. The bifunctional catalyst of the iron selenide carbon-based material is carbon-coated iron oxide and iron triselenide / iron selenide (FeSe) with well-dispersed active sites xA bifunctional catalyst of FeSe / Fe2O3@C for oxygen reduction and dye degradation has a good limiting current density during the oxygen reduction process, can generate electro-Fenton to achieve the effect of degrading methylene blue dye, and has good stability.

[0006] The technical solution for achieving the purpose of the present invention is as follows:

[0007] A preparation method of a seleniumized iron-based carbon material bifunctional catalyst, the specific steps are as follows:

[0008] Step 1: Ultrasonically dissolve ferric chloride (FeCl3) and 2-aminoterephthalic acid (H2BDC) in N,N-dimethylformamide (DMF) respectively, then add the 2-aminoterephthalic acid solution to the ferric chloride solution, and react under ultrasonic waves;

[0009] Step 2: Add a sodium hydroxide solution to the solution obtained in Step 1, perform a hydrothermal reaction at 100 °C for 12 ± 2 hours, naturally cool to room temperature, perform centrifugal separation, wash with DMF and ethanol more than 3 times in sequence, and perform vacuum drying to obtain an NH2-MIL-88B(Fe) precursor, and ultrasonically disperse it in water to form an NH2-MIL-88B(Fe) precursor dispersion;

[0010] Step 3: Add a selenious acid solution to the NH2-MIL-88B(Fe) precursor dispersion, stir at room temperature for 10 ± 2 h, after the reaction is completed, wash with DMF and deionized water more than 3 times in sequence, and perform vacuum drying to obtain an NH2-MIL-88B(Fe)-SeO3 2- polymer precursor;

[0011] Step 4: Under a protective gas atmosphere, calcine the NH2-MIL-88B(Fe)-SeO3 2- polymer precursor at 900 ± 100 °C for 3 - 6 h to obtain an FeSe x / Fe2O3@C bifunctional catalyst.

[0012] Preferably, in Step 1, the molar ratio of ferric chloride to 2-aminoterephthalic acid is 0.33:0.20, the concentration of the ferric chloride solution is 6.6 mol / mL, and the concentration of the 2-aminoterephthalic acid solution is 4 mol / mL..

[0013] Preferably, in Step 2, the concentration of the sodium hydroxide solution is 1.0 mol / L, and the molar ratio of sodium hydroxide to ferric chloride is 0.33:0.16.

[0014] Preferably, in Step 2 or 3, the vacuum drying temperature is 60 ± 5 °C, and the drying time is more than 12 h.

[0015] Preferably, in step 3, the concentration of the selenious acid solution is 0.003 M.

[0016] Preferably, in step 3, the concentration of the NH2-MIL-88B(Fe) precursor dispersion is 5 mg / ml. -1 .

[0017] Preferably, in step 4, the protective gas is nitrogen, argon or a nitrogen-argon mixture.

[0018] The present invention provides a bifunctional catalyst of an iron selenide carbon-based material prepared by the above preparation method.

[0019] Furthermore, the present invention provides the application of the above bifunctional catalyst of the iron selenide carbon-based material in oxygen reduction and electro-Fenton degradation of dyes.

[0020] Compared with the prior art, the present invention has the following advantages:

[0021] (1) The NH2-MIL-88B(Fe) synthesized from low-cost ferric chloride and 2-aminoterephthalic acid in the present invention has a simple method and cheap and easily available raw materials.

[0022] (2) The metal selenization strategy of high-temperature selenite coordination MOF carbonization with the formation of heterojunctions, and the high-porosity spindle-shaped NH2-MIL-88B(Fe) provides free ligand sites for capturing selenite through Fe-O-Se.

[0023] (3) The electrocatalyst prepared in the present invention has a porous heterostructure with highly dispersed metal sites, which is beneficial to the electrocatalysis of O2 and improves the stability and durability of the material. Description of the Drawings

[0024] Figure 1 It is a transmission electron microscope image of the precursor and intermediate of Example 1.

[0025] Figure 2 It is an X-ray diffraction pattern of the product obtained in Example 1.

[0026] Figure 3 It is a transmission electron microscope photograph of the product obtained in Example 1.

[0027] Figure 4 It is a high-resolution image of the product obtained in Example 1.

[0028] Figure 5 It is a linear sweep voltammetry curve of the product obtained in Example 1 in 0.1 mol / L KOH solution, where the scan rate is 10 mV / s -1 , and the rotation speed is 225 - 2500 rpm.

[0029] Figure 6The product obtained in Example 1, linear voltammograms of the product of Comparative Example 1 and a commercial platinum-carbon electrode in 0.1 mol / L KOH solution, where the scanning rate is 10 mV s -1 , and the rotation speed is 1600 rpm.

[0030] Figure 7 UV-visible spectral changes of the product obtained in Example 1 during the electrochemical degradation of MB in 0.1 mol / L KOH solution within 0 - 14 h.

[0031] Figure 8 Diagram of the stability and methanol resistance of the product obtained in Example 1. Detailed implementation manners

[0032] To further understand the content of the present invention, the present invention will now be described in detail with reference to the accompanying drawings and examples.

[0033] Example 1

[0034] (1) Accurately weigh 5.4 g of ferric chloride and dissolve it in 50 mL of N,N-dimethylformamide solution. After ultrasonic treatment, a uniformly dispersed ferric chloride N,N-dimethylformamide solution is obtained;

[0035] (2) Accurately weigh 3.6 g of 2-aminoterephthalic acid and dissolve it in 50 mL of N,N-dimethylformamide solution. After ultrasonic dispersion, it is slowly added dropwise to the ferric chloride N,N-dimethylformamide solution to obtain a 100 mL mixed solution, which is then ultrasonicated for 10 minutes;

[0036] (3) Accurately weigh 8 mL of sodium hydroxide solution and slowly add it dropwise to the mixed solution in step (2). Then, it is heated in a Teflon-lined autoclave at 100 °C for 12 hours, and then naturally cooled to room temperature. The obtained product is separated by centrifugation and washed 3 times with DMF and ethanol respectively. The yellowish-brown powder is collected and dried overnight in a vacuum oven at 60 °C to obtain the NH2-MIL-88B(Fe) precursor;

[0037] (4) Use the above-prepared NH2-MIL-88B(Fe) to capture SeO3 2- . Add the selenous acid solution to the dispersed solution of NH2-MIL-88B(Fe) and stir at room temperature for 10 h. The obtained yellowish-brown powder is NH2-MIL-88B(Fe)-SeO3 2- , which is carefully washed 3 times with DMF and deionized water and dried in a vacuum oven at 60 °C.

[0038] (5) Place the NH2-MIL-88B(Fe)-SeO3 formed in step (4) 2- in a tube furnace and calcine it at 900 °C for 3 h in a nitrogen atmosphere to obtain FeSex / Fe2O3@C bifunctional catalyst for oxygen reduction and dye degradation.

[0039] Figure 1 Scanning electron microscopy and transmission electron microscopy images of the precursors and intermediates of Example 1. It is obvious that NH2-MIL-88B(Fe) shows spindle-shaped with high dispersibility and uniform length. After selenite treatment, dark particles or filaments with a size of 5-10 nm can be noticed both inside and outside the crystal of NH2-MIL-88B(Fe) adsorbed with SeO3 2- The NH2-MIL-88B(Fe) crystal adsorbed with SeO3 Figure 2 X-ray diffraction pattern of the product FeSe x / Fe2O3@C obtained in Example 1. It is obvious that the X-ray powder diffraction peaks can be attributed to FeSe, Fe3Se4 and Fe2O3. Figure 3 Transmission electron microscopy image of the product obtained in Example 1. It can be seen that FeSe x / Fe2O3@C shows a heterojunction state, with many small particles appearing on the surface, and FeSe and Fe3Se4 are uniformly dispersed in the nitrogen-doped carbon film. Figure 4 High-resolution transmission electron microscopy image of the product obtained in Example 1. It can be seen that Fe2O3 is coated with a thin layer of amorphous carbon, and FeSe and Fe3Se4 show a heterojunction structure. The measured lattice spacings of 0.322 nm and 0.270 nm correspond to the C(104) and Fe2O3(104) planes, reflecting the Fe2O3 crystal encapsulated by the carbon layer. The lattice spacings of 0.258 nm and 0.268 nm correspond to the (013) and (202) crystal planes of Fe3Se4. The lattice spacings of 0.189 nm and 0.267 nm correspond to the (200) and (110) crystal planes of FeSe. Figure 5 Linear sweep voltammetry curves on a rotating disk electrode (RDE) of the product obtained in Example 1. The current density increases with the increase of the rotation speed from 400 rpm to 2500 rpm. Figure 6 Linear voltammetry scans of the product obtained in Example 1, NH2-MIL-88B(Fe) and 20% commercial Pt / C in 0.1 mol / L KOH solution. The product shows excellent catalytic performance, with a starting potential of 0.928 V, a half-wave potential of 0.770 V, and a limiting current density of 5.30 V, which is better than that of commercial Pt / C (5 V), while the sample without selenous acid adsorption experiment shows poorer performance (4.09 V). Figure 7 UV-visible spectral changes of the product obtained in Example 1 during the electrochemical degradation of methylene blue (MB) in 0.1 mol / L KOH solution. The product has a certain degradation effect on methylene blue. Figure 8 (A) The product FeSe obtained in Example 1 xChronoamperometry of the / Fe2O3@C and commercial Pt / C modified electrodes in O2-saturated 0.1 M KOH at a voltage of 0.4 V showed that, compared with Pt / C, the product exhibited excellent electrochemical durability, and its ORR activity was basically retained after 5000 cycles of cyclic voltammetry at 1600 rpm. Figure 8 (B) is FeSe x Chronoamperometric responses of the / Fe2O3@C and commercial Pt / C modified electrodes in O2-saturated 0.1 M KOH solution with the addition of 3 M methanol at Eapp = 0.4 V showed that, compared with Pt / C, the product exhibited excellent anti-methanol activity.

[0040] Comparative Example 1

[0041] This comparative example was basically the same as Example 1, except that in Step 4, selenious acid was not added, and the NH2-MIL-88B(Fe) precursor was directly calcined to obtain the Fe@C oxygen reduction catalyst.

[0042] The Fe@C oxygen reduction catalyst showed poor catalytic performance. In the linear voltammetric scan in 0.1 mol / L KOH solution, the limiting current density in its oxygen reduction performance was 4.09 V, the onset potential was 0.894 V, the half-wave potential was 0.783 V, the limiting current density was smaller than that of Example 1, and the half-wave potential was inferior to that of Example 1.

[0043] Comparative Example 2

[0044] This comparative example was basically the same as Example 1, except that in Step 4, it was stirred at room temperature for 5 h to obtain FeSe x / Fe2O3@C(5h) oxygen reduction catalyst. The catalyst material showed poor catalytic performance. In the linear voltammetric scan in 0.1 mol / L KOH solution, the limiting current density in its oxygen reduction performance was 4.54 V, the onset potential was 0.950 V, the half-wave potential was 0.837 V, the limiting current density was smaller than that of Example 1, and the onset potential and half-wave potential were inferior to those of Example 1.

[0045] Comparative Example 3

[0046] This comparative example was basically the same as Example 1, except that in Step 4, it was stirred at room temperature for 20 h to obtain FeSe x / Fe2O3@C(20h) oxygen reduction catalyst. The catalyst material showed poor catalytic performance. In the linear voltammetric scan in 0.1 mol / L KOH solution, the limiting current density in its oxygen reduction performance was 4.53 V, the onset potential was 0.931 V, the half-wave potential was 0.806 V, the limiting current density was smaller than that of Example 1, and the onset potential and half-wave potential were inferior to those of Example 1.

[0047] Comparative Example 4

[0048] This comparative example is basically the same as Example 1, and the only difference is that the concentration of selenious acid in step 3 is 0.002 M to obtain FeSe x / Fe2O3@C(0.002M) catalyst for oxygen reduction. The catalyst material shows poor catalytic performance. In the linear voltammetric scan in 0.1 mol / L KOH solution, the limiting current density in its oxygen reduction performance is 4.15 V, the onset potential is 0.911 V, the half-wave potential is 0.814 V. The limiting current density is smaller than that of Example 1, and the onset potential and half-wave potential are worse than those of Example 1.

[0049] Comparative Example 5

[0050] This comparative example is basically the same as Example 1, and the only difference is that the concentration of selenious acid in step 3 is 0.03 M to obtain FeSe x / Fe2O3@C(0.03M) catalyst for oxygen reduction. The catalyst material shows very poor catalytic performance. In the linear voltammetric scan in 0.1 mol / L KOH solution, the limiting current density in its oxygen reduction performance is 3.12 V, the onset site is 1.738 V, the half-wave potential is 1.598 V. The limiting current density is much smaller than that of Example 1, and the onset potential and half-wave potential are extremely worse than those of Example 1. The concentration of this implementation scheme is too high, and the precursor structure collapses, which is not suitable for further exploration.

Claims

1. Preparation method of iron selenide-carbon-based material bifunctional catalyst, characterized in that, The specific steps are as follows: Step 1: Ultrasonically dissolve ferric chloride and 2-aminoterephthalic acid in N,N-dimethylformamide respectively, then add the 2-aminoterephthalic acid solution to the ferric chloride solution, and react under ultrasonic condition. The molar ratio of ferric chloride to 2-aminoterephthalic acid is 0.33:0.

20. Step 2: Add the sodium hydroxide solution to the solution obtained after the reaction in Step 1, carry out hydrothermal reaction at 100 °C for 12 ± 2 hours, naturally cool to room temperature, carry out centrifugal separation, wash with DMF and ethanol for more than 3 times in sequence, and dry in vacuum to obtain the NH2-MIL-88B(Fe) precursor. Ultrasonically disperse it in water to form an NH2-MIL-88B(Fe) precursor dispersion. The concentration of the sodium hydroxide solution is 1.0 mol / L, and the molar ratio of sodium hydroxide to ferric chloride is 0.33:0.

16. Step 3: Add the selenous acid solution to the NH2-MIL-88B(Fe) precursor dispersion, stir at room temperature for 10 ± 2 h. After the reaction is completed, wash it with DMF and deionized water more than 3 times successively, and dry it under vacuum to obtain NH2-MIL-88B(Fe)-SeO3 2- The polymer precursor, and the concentration of the selenous acid solution is 0.003 M; Step 4, under a protective gas atmosphere, calcine NH2-MIL-88B(Fe)-SeO3 2- polymer precursor at 900 ± 100 °C for 3 - 6 h to obtain the FeSe x / Fe2O3@C bifunctional catalyst.

2. The preparation method according to claim 1, characterized in that, In Step 2 or 3, the vacuum drying temperature is 60 ± 5 °C, and the drying time is more than 12 h.

3. The preparation method according to claim 1, wherein, In Step 3, the concentration of the NH2-MIL-88B(Fe) precursor dispersion is 5 mg ml -1 .

4. The preparation method according to claim 1, characterized in that, In Step 4, the protective gas is nitrogen, argon or a nitrogen-argon mixed gas.

5. The iron selenide carbon-based material bifunctional catalyst prepared by the preparation method according to any one of Claims 1 to 4.

6. The application of the iron selenide carbon-based material bifunctional catalyst according to Claim 5 in oxygen reduction and electro-Fenton degradation of dyes.

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