Antimony monatomic catalyst, preparation method thereof and application of antimony monatomic catalyst in oxygen reduction reaction

Abstract

The invention is suitable for the technical field of oxygen reduction reaction catalysts, and provides an antimony monatomic catalyst, a preparation method thereof and application of the antimony monatomic catalyst in oxygen reduction reaction. The coordination environment of the Sb-based monatomic catalyst is precisely customized by combining high-energy ball milling and NH4Cl gas phase etching methods. It is proved that the Sb component is distributed on the nitrogen-doped carbon carrier in the form of single atoms, and the numbers of coordinated nitrogen atoms in the first shell layer are 3, 4 and 5 respectively. The SbAC-NC-5 catalyst with the SbN5 spatial configuration is excellent in electro-catalytic performance under the alkaline condition, and the half-wave potential reaches 0.908 V. The invention further discloses a preparation method of the SbAC-NC-5 catalyst. After a 15W cycle durability test, the voltage is only reduced by 11mV. The steric effect of * OH is remarkably relieved through the SbN5 spatial configuration, and rapid formation of * OOH and activation of the * OH state are promoted. The design of the three-dimensional configuration provides more orbits for bonding electrons, and provides a new solution for balancing activity and stability of SACs.

Description

Technical Field

[0001] The invention belongs to the technical field of oxygen reduction reaction catalysts, and in particular relates to an antimony single atom catalyst and a preparation method thereof and an application thereof in oxygen reduction reactions. Background Art

[0002] The oxygen reduction reaction (ORR), as the cathode reaction in fuel cells and zinc-air batteries, exhibits slow kinetic characteristics because it involves multiple electron reaction steps. The introduction of ORR catalysts can significantly reduce the reaction energy barrier and accelerate the electron transfer efficiency of intermediate species at active sites. The research and development of ORR catalysts has gone through many years, from the earliest precious metal catalysts (such as platinum, palladium, etc.) to the widely studied non-precious metal catalysts (such as iron, cobalt, nickel, etc.) today. With the advancement of science and technology, researchers are constantly exploring new ORR catalysts to seek higher activity, stability, anti-toxicity and lower cost.

[0003] In recent years, single atom catalysts (SACs) have become the most promising choice to replace precious metal catalysts due to their excellent catalytic activity and clear coordination structure. Their fine structure consists of four parts: metal center atom, coordination atom, environmental atom and guest group. In terms of the type of metal center, 3d transition metals (such as Fe) are favored because of their unfilled 3d valence layer electronic configuration. This configuration enables the active center to reach a suitable interaction strength with oxygen-containing species and realizes a rapid adsorption and desorption process. However, SACs still face some difficulties in practical applications, such as Fenton reaction, steric effect and demetallation, which to some extent limit the balance between the catalytic activity and stability of SACs. Therefore, the development of new metal centers is particularly critical for the application of SACs in practical energy storage devices. For p-block main group metals, their closed d shell configuration (d 10 ) and delocalized s / p valence bands were once thought to exhibit inert catalytic behavior in ORR. However, the narrow valence band width makes it easier for them to form high valence states during the reaction, thereby accelerating the charge transfer process and the adsorption of intermediates, reducing the reaction barrier, and is expected to show rich potential in ORR. In addition, the main group metal antimony (Sb) has a flexible electronic state and better anti-poisoning ability, which has certain advantages in optimizing stability and other aspects.

[0004] In order to activate the inert electronic configuration of the main-group metal center, coordination engineering has become an important research method. Coordination engineering plays a vital role in activating or enhancing the operating state of metal catalysts by fine-tuning the electronic configuration (oxidation state and spin state) of the metal center. Among them, the number and type of coordinating atoms serve as regulating variables to achieve the regulation of the electronic configuration of the metal center through short-range (low shell) and medium / long-range interactions (high shell). For main-group metals, the preparation of antimony (Sb) single-atom catalysts mainly focuses on the development of precursors containing rich Sb sources through high-temperature pyrolysis, in which the coordination structure of Sb atoms is mainly SbNx planar configuration, such as SbN 3 , SbN 4 This type of catalyst dominated by planar configuration exhibits good catalytic activity in ORR, but its stability is relatively average, which is mainly due to the insufficient adsorption capacity of the intermediates due to the large Sb-N bond amplitude, as well as the weak Sb-N bond and strong * OH steric hindrance cannot guarantee long-term cycle stability. Therefore, the present invention proposes an antimony single atom catalyst and a preparation method thereof and an application thereof in oxygen reduction reaction. Summary of the invention

[0005] The purpose of the present invention is to provide an antimony single atom catalyst and a preparation method thereof and application in an oxygen reduction reaction, aiming to solve the problems raised in the above-mentioned background technology.

[0006] The purpose of the present invention is achieved through the following technical solutions:

[0007] The method for preparing an antimony single-atom catalyst is characterized by comprising the following steps:

[0008] Step 1: Prepare the precursor mixture: Add antimony trioxide (Sb 2 O 3 )、zinc oxide (ZnO), ammonium nitrate (NH 4 NO 3 ), 2-methylimidazole and dimethylformamide (DMF), operate at a speed of 500 rpm for 30 min and then stop for 10 min, repeat the above steps 4 times to obtain a precursor mixture;

[0009] Step 2, preparing a carbon-based material modified with Sb nanoparticles: under the protection of a nitrogen atmosphere, using the precursor mixture as a raw material, calcining at 950° C. for 2 h to obtain a carbon-based material modified with Sb nanoparticles;

[0010] Step 3: Preparation of antimony single atom catalyst: The sample obtained in step 2 was mixed with NH 4 The ground mixture was calcined at 1000°C for 2h to finally obtain an antimony single atom catalyst.

[0011] Further, in step 3, the sample obtained in step 2 is mixed with NH 4 The mass ratio of Cl is 1:5 to 1:15.

[0012] Furthermore, in step 2, the temperature is increased to 950° C. at a heating rate of 5° C. / min.

[0013] Furthermore, in step 3, the temperature is increased to 1000° C. at a heating rate of 10° C. / min.

[0014] Furthermore, the antimony trioxide is replaced by antimony trioxide (SbCl 3 ) or antimony acetylacetonate.

[0015] The antimony single atom catalyst is prepared according to the preparation method of the antimony single atom catalyst described above.

[0016] According to the application of the antimony single atom catalyst in the electrocatalytic oxygen reduction reaction.

[0017] Compared with the prior art, the present invention has the following beneficial effects:

[0018] The present invention combines high energy ball milling and NH 4 Cl vapor phase etching method was used to achieve precise customization of the coordination environment of Sb-based single-atom catalysts. It was confirmed that the Sb component was distributed on the nitrogen-doped carbon support in the form of single atoms, and the number of coordinated nitrogen atoms in the first shell was 3, 4, and 5, respectively. 5 Stereo configuration of Sb AC -NC-5 catalyst exhibits excellent electrocatalytic performance under alkaline conditions, and its half-wave potential (E 1 / 2 ) is as high as 0.908V. After a 15W cycle durability test, its half-wave potential only dropped by 11mV, showing good stability. 5 The stereo configuration significantly alleviates the steric hindrance of *OH, thereby promoting the rapid formation of *OOH and the activation of *OH states. The design of the stereo configuration provides more orbitals for bonding electrons, providing a new solution to the challenge of how to balance activity and stability in single atom catalysts (SACs). BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 Transmission electron microscopy (TEM) characterization of the materials prepared in Examples 1 to 3; wherein (a) is Sb AC -NC-3 microstructure, (b) Sb AC -NC-4 microstructure, (c) Sb AC -NC-5 microstructure, (d) Sb AC-High-resolution image of NC-3, (e) Sb AC -High-resolution image of NC-4, (f) is Sb AC -High-resolution image of NC-5, (g) is Sb AC -Element distribution diagram of NC-3, (h) is Sb AC -Element distribution diagram of NC-4, (i) is Sb AC -Element distribution map of NC-5.

[0020] Figure 2 X-ray diffraction (XRD) characterization of the materials prepared in Examples 1 to 3.

[0021] Figure 3 X-ray diffraction (XRD) characterization of the materials prepared in Examples 1 to 3.

[0022] Figure 4 X-ray absorption fine structure (XAFS) characterization of the materials prepared in Examples 1 to 3; wherein (a) is the near-edge absorption structure spectrum, (b) is the valence state fitting curve, (c) is the extended edge structure spectrum, and (d) is the extended edge structure fitting curve.

[0023] Figure 5 The electrochemical performance tests of the materials prepared in Examples 1 to 3 are as follows; wherein (a) is the half-wave potential, (b) is the rotating ring disk electrode test (RRDE), (c) is the kinetic current density, and (d) is the cycle accelerated durability test.

[0024] Figure 6 The Gibbs free energy change diagram of the materials prepared in Examples 1 to 3. DETAILED DESCRIPTION

[0025] In order to have a clearer understanding of the technical features, purposes and beneficial effects of the present invention, the technical solution of the present invention is now described in detail below, but it should not be understood as limiting the scope of the present invention. The experimental methods described in the following examples are conventional methods unless otherwise specified; the reagents and materials can be obtained from commercial sources unless otherwise specified.

[0026] The specific implementation of the present invention is described in detail below in conjunction with specific embodiments.

[0027] Example 1. Antimony single atom catalyst (Sb AC -NC-3) preparation;

[0028] 488 mg of zinc oxide, 55 mg of antimony trioxide, 1970 mg of 2-methylimidazole, 50 mg of ammonium nitrate and 450 μl of dimethylformamide were fully ground, and the obtained mixture was put into a ball mill, and the high-energy ball mill was operated at a speed of 500 rpm for 30 min, and then stopped for 15 min. This step was repeated 4 times to obtain a precursor mixture; under the protection of a nitrogen atmosphere, the precursor mixture was used as a raw material, and the temperature was increased to 950°C at a heating rate of 5°C / min, and calcined at 950°C for 2 h to obtain a Sb nanoparticle-modified carbon-based material; the sample obtained in the above steps was mixed with NH 4 The mixture was fully ground and the mass ratio of the two was controlled to be 1:5. The temperature was raised to 1000°C at a heating rate of 10°C / min, and the ground mixture was calcined at 1000°C for 2h to finally obtain an antimony single atom catalyst (Sb AC -NC-3).

[0029] Example 2, preparation of antimony single atom catalyst (SbAC-NC-4);

[0030] 488 mg of zinc oxide, 55 mg of antimony trioxide, 1970 mg of 2-methylimidazole, 50 mg of ammonium nitrate and 450 μl of dimethylformamide were fully ground, and the obtained mixture was put into a ball mill, and the high-energy ball mill was operated at a speed of 500 rpm for 30 min, and then stopped for 15 min. This step was repeated 4 times to obtain a precursor mixture; under the protection of a nitrogen atmosphere, the precursor mixture was used as a raw material, and the temperature was increased to 950°C at a heating rate of 5°C / min, and calcined at 950°C for 2 h to obtain a Sb nanoparticle-modified carbon-based material; the sample obtained in the above steps was mixed with NH 4 Cl was fully ground and the mass ratio of the two was controlled to be 1: 10. The temperature was raised to 1000°C at a heating rate of 10°C / min, and the ground mixture was calcined at 1000°C for 2h to finally obtain an antimony single atom catalyst (SbAC-NC-4).

[0031] Example 3, Antimony single atom catalyst (Sb AC -NC-5) preparation;

[0032] 488 mg of zinc oxide, 55 mg of antimony trioxide, 1970 mg of 2-methylimidazole, 50 mg of ammonium nitrate and 450 μl of dimethylformamide were fully ground, and the obtained mixture was put into a ball mill, and the high-energy ball mill was operated at a speed of 500 rpm for 30 min, and then stopped for 15 min. This step was repeated 4 times to obtain a precursor mixture; under the protection of a nitrogen atmosphere, the precursor mixture was used as a raw material, and the temperature was increased to 950°C at a heating rate of 5°C / min, and calcined at 950°C for 2 h to obtain a Sb nanoparticle-modified carbon-based material; the sample obtained in the above steps was mixed with NH4 The mixture was fully ground and the mass ratio of the two was controlled to be 1:15. The temperature was raised to 1000°C at a heating rate of 10°C / min, and the ground mixture was calcined at 1000°C for 2h to finally obtain an antimony single atom catalyst (Sb AC -NC-5).

[0033] As described in Examples 1 to 3, during the high-energy ball milling process, the synergistic effect of the transverse shear force and the longitudinal compression force between the ball milling beads destroyed the ZnO and Sb 2 O 3 The Zn-O and Sb-O bonds in the molten Zn 2+ and Sb 3+ and assemble with 2-methylimidazole to form Sb-doped zeolite imidazolate framework (SbZn@ZIFs-x). 3+ The carbon was reduced to Sb nanoparticles and supported on nitrogen-doped carbon. In the second high-temperature pyrolysis, NH 4 The thermal decomposition of Cl produces HCl and NH 3 was used to exfoliate Sb nanoparticles into single-atom form, which was subsequently recaptured by the carbon support. 4 The precise control of Cl vapor etching successfully achieved the precise customization of the first shell coordination environment of Sb atoms, and finally prepared the antimony single atom catalyst Sb with excellent performance. AC -NC-x(x=3,4,5).

[0034] Example 4. Characterization and testing of materials prepared in Examples 1 to 3;

[0035] Transmission electron microscopy (TEM) characterization: Results are shown in Figure 1 The microscopic morphology of the materials prepared in Examples 1 to 3 is a rhombic dodecahedron ( Figure 1 In the high-resolution image, the carbon support exhibits an amorphous structure as a whole, and no metal nanoparticles are found ( Figure 1 d, e, f). The element distribution diagram shows that carbon, nitrogen, oxygen, antimony and other elements are evenly distributed ( Figure 1 (g, h, i).

[0036] High-angle annular dark field scanning transmission electron microscopy (HAADF-STEM) images: Results are shown in Figure 2 The dense bright spots in the figure are Sb single atoms, which intuitively show that the Sb component is distributed in the form of single atoms on the amorphous carbon support.

[0037] X-ray diffraction (XRD) characterization: Results are shown in Figure 3The XRD diffraction peaks of the prepared material only have two carbon peaks (002) and (101), and no characteristic diffraction peaks of Sb, indicating that the Sb component is distributed in the carbon support in the form of single atoms.

[0038] X-ray absorption fine structure (XAFS) characterization: Results are shown in Figure 4 In (a), Sb AC -NC-x (x = 3, 4, 5) white line peak intensity is higher than Sb 2 O 3 , indicating that the valence state of the Sb components is greater than trivalent. Figure 4 The valence state fitting results of (b) show that Sb AC -The valence state of Sb in NC-5 is +3.73. Figure 4 EXAFS and Figure 4 The fitting data in (d) confirms that SbN 3 , SbN 4 and SbN 5 The existence of the configuration, that is, the Sb atom is coordinated with 3, 4 and 5 N atoms in the first shell respectively. 5 It belongs to the stereo coordination configuration.

[0039] Electrochemical performance test: Results are shown in Figure 5 ,Depend on Figure 5 From a and c, we can see that Sb AC -NC-5 has the highest half-wave potential (E 1 / 2 =0.908V) and kinetic current density (J K =69.73 mA cm -2 ). The rotating ring disk electrode test (RRDE) showed that Sb AC -NC-5 has a transferred electron number close to 4 and the lowest hydrogen peroxide yield ( Figure 5 b), its reaction path is close to the ideal four-electron reaction process. Cyclic accelerated durability test shows that Sb AC - After the 15W cycle test, the half-wave potential of NC-5 only lost 11mA ( Figure 5 In d), prove that SbN 5 The stereo configuration has good cycle durability.

[0040] Gibbs free energy change diagram: Results are shown in Figure 6 For SbN 3 and SbN 4 Configuration, * OH to OH - The conversion of is the rate-determining step (RDS), and the energy rising barriers are 1.19 and 0.76 eV respectively. * OH is strongly adsorbed in both cases, with strong* The OH effect greatly limits the catalytic activity of ORR. 5 The orbital stabilization effect of the stereo configuration significantly weakens the * OH steric hindrance effect leads to different RDS (O 2 +H 2 O+e - → * OOH), the energy rising barrier is 0.63eV.

[0041] The above are only preferred embodiments of the present invention. It should be pointed out that, for those skilled in the art, several modifications and improvements can be made without departing from the concept of the present invention. These should also be regarded as the protection scope of the present invention. These will not affect the effect of the implementation of the present invention and the practicality of the patent.

Claims

1. A method for preparing an antimony single atom catalyst, characterized in that: The following steps are involved: Step 1, preparing a precursor mixture: adding antimony trioxide, zinc oxide, ammonium nitrate, 2-methylimidazole and dimethylformamide into a ball mill, operating at a speed of 500 rpm for 30 minutes and then stopping for 10 minutes, repeating 4 times to obtain a precursor mixture; Step 2, preparing a carbon-based material modified with Sb nanoparticles: under the protection of a nitrogen atmosphere, using the precursor mixture as a raw material, calcining at 950° C. for 2 h to obtain a carbon-based material modified with Sb nanoparticles; Step 3, preparing antimony single atom catalyst: fully grind the sample obtained in step 2 with NH4Cl; calcine the ground mixture at 1000°C for 2h to finally obtain antimony single atom catalyst.

2. The method for preparing the antimony single atom catalyst according to claim 1, characterized in that: In step 3, the mass ratio of the sample obtained in step 2 to NH4Cl is 1:5 to 1:

15.

3. The method for preparing the antimony single atom catalyst according to claim 1, characterized in that: In the step 2, the temperature is increased to 950° C. at a heating rate of 5° C. / min.

4. The method for preparing the antimony single atom catalyst according to claim 1, characterized in that: In the step 3, the temperature is increased to 1000° C. at a heating rate of 10° C. / min.

5. The method for preparing the antimony single atom catalyst according to claim 1, characterized in that: The antimony trioxide is replaced by antimony trioxide or antimony acetylacetonate.

6. An antimony single-atom catalyst prepared according to the method for preparing an antimony single-atom catalyst according to any one of claims 1 to 5.

7. Use of the antimony single atom catalyst according to claim 6 in an electrocatalytic oxygen reduction reaction.

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