Se-doped sm monatomic catalyst for oxygen reduction electrocatalysis and preparation method and application thereof

Abstract

The application relates to a Se-doped Sm monatomic catalyst for oxygen reduction electrocatalysis and a preparation method and application thereof, the catalyst comprising a carbon nitride carrier and a monatomic metal active component dispersed thereon, and the central active atom of the metal active component being an Sm atom and a Se atom. The application dopes Se elements on the basis of a Sm / carbon nitride monatomic catalyst, and the joint action of the Se elements improves the oxygen reduction reaction kinetics and four-electron selectivity, so that the activity and durability of the monatomic catalyst in an oxygen reduction electrocatalysis reaction and a zinc-air battery are synergistically improved.

Description

Technical Field

[0001] This application relates to the field of oxygen reduction electrocatalysis technology, and in particular to a Se-doped Sm single-atom catalyst for oxygen reduction electrocatalysis, its preparation method and application. Background Technology

[0002] With the development of green energy technologies, high-efficiency energy storage and conversion devices play a crucial role in renewable energy utilization and grid stability. Zinc-air batteries, due to their advantages such as high theoretical energy density, environmental friendliness, abundant raw materials, and good safety, are considered promising new energy devices. However, the slow kinetics of the oxygen reduction reaction (ORR) in the air cathode of zinc-air batteries severely limit the energy conversion efficiency and output performance of the battery. Currently, although commercial Pt / C catalysts exhibit high ORR activity, their high cost, scarcity of resources, and insufficient long-term stability make it difficult to meet the needs of large-scale applications of zinc-air batteries. Therefore, developing low-cost, highly active, and durable non-precious metal ORR catalysts is of great significance.

[0003] Transition metal single-atom catalysts, represented by Fe, Co, and Ni, have become important candidate materials to replace Pt-based catalysts due to their high atom utilization, well-defined active centers, and excellent intrinsic activity. However, in actual ORR processes, transition metal centers readily undergo Fenton or Fenton-like reactions with the byproduct H₂O₂, generating highly oxidizing hydroxyl radicals that attack the active centers and carbon supports, leading to catalyst deactivation and limiting long-term operational stability. In contrast, rare earth single-atom catalysts are relatively inert to the Fenton reaction and have the potential to improve stability. However, rare earth elements have strong oxygen affinity, which can easily lead to excessive adsorption of key ORR intermediates, resulting in limited reaction kinetics and decreased intrinsic activity. Therefore, to improve the adsorption behavior of rare earth single-atom catalysts for ORR intermediates and achieve a synergistic improvement in activity and stability, it is crucial to regulate the coordination environment and electronic structure of the metal atoms.

[0004] CN120015857A discloses a nitrogen-doped porous carbon-supported iron-selenium transition metal composite material, its preparation method, and its application. This method introduces Se atoms into an Fe single-atom catalyst, with the components uniformly distributed on a nitrogen-doped carbon-based material. Since this system is essentially a transition metal Fe-based single-atom catalyst, it may still be affected by H2O2 byproducts and free radical attacks during long-term ORR processes, and its durability still has room for further improvement.

[0005] Nano Research, 2024, 17, 4753–4763, reported a Ce–Se diatomic catalyst that achieves remote modulation of the electronic structure of the Ce–N4 region by constructing a non-bonded heteronuclear diatomic structure between rare-earth Ce and metalloid Se, thereby improving ORR activity and zinc-air battery performance. The study indicates that the Ce–Se diatomic system can modulate the electroactivity of the Ce–N4 region through electron transfer, and the electron-rich Se sites also help promote the adsorption of key intermediates. However, this scheme belongs to the Ce–Se diatomic catalyst design, where Ce and Se atoms exist in a highly dispersed state in a nitrogen-doped carbon support, and no direct Ce–Se coordination bond was detected. The construction of the diatomic sites requires high precision in the positions of adjacent atoms, defect structures, and coordination environment, and the controllability and structural consistency of the preparation still face challenges. Furthermore, it does not modulate the Sm / NC system through Se vapor deposition doping, nor does it systematically design for the influence of surface bonding structures such as Se-C, Se-N, and Se-O in Sm single-atom catalysts on ORR performance.

[0006] Therefore, developing a rare-earth-containing single-atom catalyst that can balance excellent oxygen reduction activity and stability has become a key issue in promoting the development of this field. Summary of the Invention

[0007] To address the aforementioned technical problems, this application proposes a Se-doped Sm single-atom catalyst for oxygen reduction electrocatalysis, its preparation method, and its application. This application utilizes Se doping on a Sm / carbon nitride (NC) single-atom catalyst, which enhances the kinetics and four-electron selectivity of the oxygen reduction reaction (ORR) through a combined effect, thereby synergistically improving the activity and durability of the single-atom catalyst in the oxygen reduction electrocatalytic reaction.

[0008] To achieve this objective, the following technical solution is adopted in this application: In a first aspect, this application provides a Se-doped Sm single-atom catalyst for oxygen reduction electrocatalysis, the catalyst comprising a carbon nitride support and a single-atom metal active component dispersed thereon, wherein the central active atoms of the metal active component are Sm atoms and Se atoms.

[0009] The Se-doped Sm single-atom catalyst (Sm / SeNC) provided in this application regulates the surface chemical environment and local electronic structure of the Sm / NC system through the incorporation of Se. This regulation helps to optimize the charge distribution around the Sm sites, alleviate the problem of excessive adsorption of oxygen-containing intermediates by rare earth Sm sites, and improve the ORR reaction kinetics and the selectivity of the four-electron pathway. As a result, the Sm single-atom catalyst exhibits excellent oxygen reduction activity and stability, achieving a synergistic improvement in activity and durability.

[0010] In some embodiments, the Se is incorporated into the carbon nitride support framework to form Se-C, Se-N, and Se-O coordination structures, and to regulate the charge distribution around the Sm sites.

[0011] This application modifies the microenvironment of Sm sites by forming surface bonding structures such as Se-C, Se-N, and Se-O in Sm single-atom catalysts, reduces the electron cloud density around Sm sites, shifts the d-band center downward, optimizes the adsorption strength of active sites for oxygen-containing intermediates, and improves catalytic kinetics and catalytic efficiency.

[0012] In some embodiments, the carbon nitride support includes any one or a combination of at least two of ZIF-based carbon nitride, graphene-based carbon nitride, or carbon nanotube-based carbon nitride.

[0013] This application further enhances catalytic activity by selecting a porous carbon nitride support, which has abundant metal active sites.

[0014] Secondly, this application provides a method for preparing a Se-doped Sm single-atom catalyst as described in the first aspect, the method comprising the following steps: S1: Add carbon nitride support and Sm source to mixed molten salt system to obtain Sm / NC single-atom catalyst after reaction; S2: The Sm / NC single-atom catalyst obtained in step S1 is doped with Se powder by vapor deposition to obtain the Se-doped Sm single-atom catalyst.

[0015] In preparing the Se-doped Sm single-atom catalyst, this application employs a method combining molten salt-assisted ion exchange and Se vapor-phase deposition doping. The molten salt system provides a uniform reaction environment for ion exchange and dispersion anchoring between Sm species and the carbon nitride support, which is beneficial to the stable distribution of Sm species in the carbon nitride support. Subsequent Se vapor-phase deposition doping further modulates the surface chemical composition and electronic structure of the carbon-based framework, enabling the catalyst to possess high ORR activity, good reaction selectivity, and excellent long-term stability.

[0016] In some embodiments, the preparation method includes the following steps: (1) Grind and mix the Sm source with the carbon nitride support to obtain a mixture; (2) The mixture obtained in step (1) is wrapped with a mixed molten salt system, and after the first calcination, it is post-treated to obtain the Sm / NC single-atom catalyst; (3) Under a protective atmosphere, the Se source is introduced into the Sm / NC single-atom catalyst by vapor deposition, and after a second calcination, the Se-doped Sm single-atom catalyst is obtained.

[0017] In some embodiments, the Sm source includes any one or a combination of at least two of samarium chloride, samarium acetate hydrate, or samarium nitrate hexahydrate.

[0018] In some embodiments, the carbon nitride support is prepared by pyrolysis of ZIF-8 / 1,10-phenanthroline (Phen) precursor at 800-1100 °C under a protective atmosphere.

[0019] Among them, 800-110℃, for example, can be 850℃, 900℃, 950℃, 1000℃ or 1050℃, etc.

[0020] The protective atmosphere may be, for example, nitrogen, argon or helium, and is more preferably argon.

[0021] In some embodiments, the mass ratio of the Sm source to the carbon nitride support is (0.05-0.10):1, for example, it can be 0.06:1, 0.07:1, 0.08:1 or 0.09:1, etc.

[0022] In some embodiments, the mixed molten salt system comprises a combination of potassium chloride and lithium chloride.

[0023] In some embodiments, the mass ratio of potassium chloride to lithium chloride is (0.5-2):1, for example, it can be 0.7:1, 0.9:1, 1.1:1, 1.3:1, 1.5:1, 1.7:1 or 1.9:1, etc.

[0024] In some embodiments, the first calcination is carried out in a tube furnace.

[0025] In some embodiments, the atmosphere for the first calcination is an inert gas, preferably argon.

[0026] In some embodiments, the heating rate of the first calcination is 2-10 °C / min, for example, it can be 3 °C / min, 4 °C / min, 5 °C / min, 6 °C / min, 7 °C / min, 8 °C / min or 9 °C / min, etc.

[0027] In some embodiments, the holding temperature of the first calcination is 600-900℃, for example, it can be 620℃, 640℃, 660℃, 680℃, 700℃, 720℃, 740℃, 760℃, 780℃, 800℃, 820℃, 840℃, 860℃ or 880℃, etc.

[0028] In some embodiments, the holding time for the first calcination is 1-3 hours, for example, 1.5 hours, 2 hours, 2.5 hours, etc.

[0029] In some embodiments, the post-processing includes washing and drying.

[0030] In some embodiments, the washing solution used for washing is anhydrous ethanol and deionized water in sequence.

[0031] In some implementations, the number of washes is 2-5 times, for example, 2 times, 3 times, 4 times, or 5 times.

[0032] In some embodiments, the drying is performed by forced-air drying or vacuum drying.

[0033] In some embodiments, the drying temperature is 60-80°C, for example, it can be 65°C, 70°C or 75°C.

[0034] In some embodiments, the drying time is 6-12 hours, for example, 7 hours, 8 hours, 9 hours, 10 hours or 11 hours.

[0035] In some embodiments, the vapor deposition process includes placing Se powder at the front end of a tubular furnace and placing the Sm / NC catalyst at the rear end of the tubular furnace for a second calcination.

[0036] In some embodiments, the vapor deposition is performed under an inert atmosphere, such as helium or argon, with argon being more preferred.

[0037] In some embodiments, the heating rate of the vapor deposition is 2-10 °C / min, for example, it can be 3 °C / min, 4 °C / min, 5 °C / min, 6 °C / min, 7 °C / min, 8 °C / min or 9 °C / min, etc.

[0038] In some embodiments, the holding temperature for vapor deposition is 600-900℃, for example, it can be 620℃, 640℃, 660℃, 680℃, 700℃, 720℃, 740℃, 760℃, 780℃, 800℃, 820℃, 840℃, 860℃ or 880℃, etc.

[0039] In some embodiments, the holding time for vapor deposition is 1-3 h, for example, 1.5 h, 2 h, 2.5 h, etc.

[0040] In some embodiments, the mass ratio of the Se source to the Sm / NC single-atom catalyst is (0.03-0.10):1, for example, it can be 0.04:1, 0.05:1, 0.06:1, 0.07:1, 0.08:1 or 0.09:1, etc.

[0041] Thirdly, this application provides an application of the Se-doped Sm single-atom catalyst described in the first aspect in oxygen reduction electrocatalysis.

[0042] In some embodiments, the Se-doped Sm single-atom catalyst is used in an oxygen reduction electrode or an air cathode.

[0043] In this application, Se-doped Sm single-atom catalysts can be used in zinc-air batteries as air cathodes to carry out oxygen reduction and oxygen evolution reactions, adsorb and desorb key oxygen-containing intermediates, optimize adsorption energy, and improve oxygen reduction activity and battery cycle durability.

[0044] The above enumeration of all specific point values, including the specific point values ​​between the listed point values, is not exhaustively listed here due to space limitations and for the sake of brevity.

[0045] Compared with the prior art, this application has at least the following beneficial effects: (1) This application improves ORR kinetics and four-electron selectivity by doping Se on the basis of Sm / NC single-atom catalyst, thereby synergistically improving the activity and durability of the single-atom catalyst in oxygen reduction electrocatalytic reaction.

[0046] (2) The Se-doped Sm single-atom catalyst for oxygen reduction catalysis provided in this application, while maintaining the highly dispersed structure of Sm single atoms, introduces Se into the Sm / NC catalyst to form structures such as Se-C, Se-N, and Se-O, further breaking the original symmetrical configuration of the metal-support. The coordination structure of SmN6 is optimized into the coordination structure of SmSeN5, which regulates the local coordination environment and electronic structure of Sm single atoms, weakens the excessive adsorption of oxygen-containing intermediates by the active center of Sm atoms, balances the activation of intermediates and desorption of products, and improves the selectivity of target products.

[0047] (3) This application adopts a preparation method that combines molten salt-assisted ion exchange with Se vapor-phase deposition doping, which can synergistically improve the comprehensive performance of Sm single-atom catalysts from two aspects: catalyst structure construction and heteroatom electronic regulation. This method has clear process steps and controllable conditions, avoiding the need for complex equipment.

[0048] (4) The Se-doped Sm single-atom catalyst provided in this application exhibits good oxygen reduction activity, discharge stability and cycle life in zinc-air batteries. Its comprehensive performance is better than that of Sm single-atom catalysts and commercial Pt / C catalysts. The zinc-air battery with it as an air cathode can operate stably and continuously for at least 100 h. Attached Figure Description

[0049] Figure 1This is a schematic diagram of the preparation process of Sm / SeNC for oxygen reduction electrocatalysis in this application.

[0050] Figure 2 The images show the XRD patterns of Sm / SeNC, NC, and Sm / NC prepared in Example 1, Comparative Example 1, and Comparative Example 3.

[0051] Figure 3 The images show the Raman spectra of Sm / SeNC, NC, and Sm / NC prepared in Example 1, Comparative Example 1, and Comparative Example 3.

[0052] Figure 4 The HAADF-STEM and EDS spectra of Sm / SeNC prepared in Example 1 are shown.

[0053] Figure 5 XPS plots of Sm / SeNC and Sm / NC prepared in Example 1 and Comparative Example 3.

[0054] Figure 6 The LSV curves are for the catalysts prepared in Example 1 and Comparative Examples 1-3.

[0055] Figure 7 The constant current charge-discharge voltage of zinc-air batteries assembled with the catalysts prepared in Example 1 and Comparative Example 2 varies with time. Detailed Implementation

[0056] The technical solution of this application will be further described below with reference to the accompanying drawings and specific embodiments. Those skilled in the art should understand that the embodiments described are merely illustrative of this application and should not be construed as specific limitations thereof.

[0057] Preparation Example 1 This preparation example provides a carbon nitride (NC) support, the preparation method of which is as follows: (1) Dissolve 20.0 g of 2-methylimidazole in 200 mL of methanol, and dissolve 9.08 g of Zn(NO3)2•6H2O in 200 mL of methanol; (2) Under continuous stirring, 2-methylimidazole solution was slowly added dropwise to zinc nitrate solution. After reacting at room temperature for 6 h, the precipitate was collected by centrifugation, washed and dried to obtain ZIF-8. (3) Take 1.0 g of ZIF-8 obtained in step (2) and 0.25 g of 1,10-phenanthroline (phen) and disperse them in a mixed solvent of 45 mL ethanol and 15 mL water. Stir for 6 h, concentrate by rotary evaporation, and dry to obtain ZIF-8 / Phen precursor. (4) Place the ZIF-8 / Phen precursor from step (3) in a tube furnace, heat it to 1000°C at 10°C / min under an argon atmosphere, keep it at the temperature for 1 h, and cool it naturally to room temperature. The collected black powder is the carbon nitride carrier.

[0058] Example 1 This embodiment provides a Sm / SeNC catalyst, the preparation process of which is as follows: Figure 1 As shown, it includes the following steps: (1) Weigh 50 mg of the NC carrier from Preparation Example 1 and 3.87 mg of SmCl3 (0.015 mmol) and place them in an agate mortar. Grind for 10 min to mix evenly to obtain a SmCl3-NC mixture. (2) Weigh 1.25 g of KCl and 1.25 g of LiCl and mix them evenly. The total mass is 2.5 g and the mass ratio is 1:1 to obtain a KCl-LiCl mixed molten salt. (3) A layer of KCl-LiCl mixed molten salt obtained in step (2) is spread on the bottom of the magnetic boat, and the SmCl3-NC mixture obtained in step (1) is placed in the middle of the magnetic boat. The remaining molten salt is then spread on top to completely encapsulate the sample. The magnetic boat is then moved into a tube furnace and heated to 800℃ at 5℃ / min under an Ar atmosphere. The furnace is then kept at the temperature for 2 h and allowed to cool naturally to room temperature to obtain the Sm / NC precursor system. (4) The Sm / NC precursor system was washed three times with anhydrous ethanol and deionized water, respectively, and then centrifuged and vacuum dried to obtain the Sm / NC catalyst. (5) Weigh 3.02 mg of Se powder and place it in the front magnetic boat of the tube furnace, and place 50 mg of the Sm / NC catalyst obtained in step (5) in the rear magnetic boat of the tube furnace; heat to 800℃ at 5℃ / min under Ar atmosphere, and keep warm for 2 h to allow Se to be incorporated into the Sm / NC catalyst system by vapor deposition. (6) After the sample in step (5) is naturally cooled to room temperature by the tube furnace, the Sm / SeNC catalyst is obtained.

[0059] Example 2 This embodiment provides a Sm / SeNC catalyst, the preparation method of which includes the following steps: (1) Weigh 50 mg of the NC carrier from Preparation Example 1 and 3.10 mg of samarium acetate into an agate mortar, grind for 10 min to mix evenly, and obtain samarium acetate-NC mixture; (2) Weigh 1.25 g of KCl and 1.25 g of LiCl and mix them evenly. The total mass is 2.5 g and the mass ratio is 1:1 to obtain a KCl-LiCl mixed molten salt. (3) A layer of KCl-LiCl mixed molten salt obtained in step (2) is spread on the bottom of the magnetic boat. The samarium acetate-NC mixture obtained in step (1) is placed in the middle of the magnetic boat, and the remaining molten salt is spread on top to completely cover the sample. The magnetic boat is moved into a tube furnace and heated to 760℃ at 3℃ / min under He atmosphere. It is then kept at the temperature for 1.5 h and naturally cooled to room temperature to obtain the Sm / NC precursor system. (4) The Sm / NC precursor system was washed four times with anhydrous ethanol and deionized water, respectively, and then centrifuged and dried by blowing to obtain the Sm / NC catalyst. (5) Weigh 5.00 mg of Se powder and place it in the front magnetic boat of the tube furnace, and place 50 mg of the Sm / NC catalyst obtained in step (5) in the rear magnetic boat of the tube furnace; heat to 860℃ at 6℃ / min under He atmosphere, and keep calcined for 1.5 h to allow Se to be incorporated into the Sm / NC system by vapor deposition. (6) After the sample in step (5) is naturally cooled to room temperature by the tube furnace, the Sm / SeNC catalyst is obtained.

[0060] Example 3 This embodiment provides a Sm / SeNC catalyst, the preparation method of which includes the following steps: (1) Weigh 50 mg of the NC carrier from Preparation Example 1 and 4.05 mg of samarium nitrate hexahydrate into an agate mortar, grind for 10 min to mix evenly, and obtain samarium acetate-NC mixture; (2) Weigh 1.25 g of KCl and 1.25 g of LiCl and mix them evenly. The total mass is 2.5 g and the mass ratio is 1:1 to obtain a KCl-LiCl mixed molten salt. (3) A layer of KCl-LiCl mixed molten salt obtained in step (2) is spread on the bottom of the magnetic boat, and the samarium acetate-NC mixture obtained in step (1) is placed in the middle of the magnetic boat. The remaining molten salt is then spread on top to completely encapsulate the sample. The magnetic boat is then transferred into a tube furnace and heated to 820°C at 7 °C / min under a He atmosphere. The furnace is then kept at this temperature for 2.5 h and allowed to cool naturally to room temperature to obtain the Sm / NC precursor system. (4) The Sm / NC precursor system was washed five times with anhydrous ethanol and deionized water, respectively, and then centrifuged and dried by blowing to obtain the Sm / NC catalyst. (5) Take 1.50 mg of Se powder and place it in the front magnetic boat of the tube furnace, and place 50 mg of the Sm / NC catalyst obtained in step (5) in the rear magnetic boat of the tube furnace; heat it to 780℃ at 8℃ / min under Ar atmosphere, and keep it at the temperature for 2.5 h to allow Se to be incorporated into the Sm / NC system by vapor deposition. (6) After the sample in step (5) is naturally cooled to room temperature by the tube furnace, the Sm / SeNC catalyst is obtained.

[0061] Example 4 This embodiment provides a Sm / SeNC catalyst. The only difference between this catalyst and that of Example 1 is that the mass ratio of Se source to Sm / NC single-atom catalyst is 0.015:1. All other components, amounts added, preparation methods and parameters are the same as those of Example 1.

[0062] Example 5 This embodiment provides a Sm / SeNC catalyst. The only difference between this catalyst and that of Example 1 is that the mass ratio of Se source to Sm / NC single-atom catalyst is 0.30:1. All other components, amounts added, preparation methods and parameters are the same as those of Example 1.

[0063] Example 6 This embodiment provides a Sm / SeNC catalyst, which differs from that of Example 1 in its preparation method. The preparation method of the catalyst in this embodiment is as follows: samarium chloride, sodium selenite, and the carbon nitride support obtained in Example 1 are added to ethanol. The mixed solution is sonicated for 30 min, and then the ethanol is removed by rotary evaporation. The resulting solid is placed in a tube furnace and calcined at 300°C for 5 h under argon protection. The obtained solid is washed with water and anhydrous ethanol, dried, and then placed in a tube furnace and calcined at 600°C for 5 h under argon protection to obtain the Sm / SeNC catalyst.

[0064] Comparative Example 1 Compared with Example 1, this comparative example is only the carbon nitride support obtained in Preparation Example 1, which is not loaded with Sm and Se.

[0065] Comparative Example 2 Compared to Example 1, this comparative example uses a commercially available Pt / C catalyst.

[0066] Comparative Example 3 Compared with Example 1, this comparative example is an Sm / NC catalyst. Steps (6) to (7) in Example 1 are omitted, that is, Se doping is not performed. The rest of the preparation method is the same as that in Example 1.

[0067] Comparative Example 4 Compared with Example 1, this comparative example is a Se / NC catalyst. The samarium chloride in steps (1) to (5) of Example 1 is replaced with potassium selenite, steps (6) to (7) are omitted, and the rest of the preparation method is the same as that of Example 1 to obtain the Se / NC catalyst.

[0068] Comparative Example 5 Compared with Example 1, this comparative example is a Fe / SeNC catalyst. In Example 1, samarium chloride in steps (1) to (5) is replaced with ferrous sulfate, and the rest of the preparation method is the same as in Example 1 to obtain the Fe / SeNC catalyst.

[0069] 1. Structural Analysis Figure 2 The XRD patterns of Sm / SeNC, NC, and Sm / NC prepared in Example 1, Comparative Example 1, and Comparative Example 3 are shown. The results show that NC only exhibits broad diffraction peaks of carbon materials, and no related diffraction peaks of metals or metal oxides are observed; and Sm / NC and Sm / SeNC only have (002) and (101) diffraction peaks of graphite carbon, and no characteristic peaks of Sm metal, Sm oxide, Se element or Se oxide are observed, indicating that Sm and Se components are highly dispersed, the utilization rate of metal atoms is improved, the adsorption energy of intermediates is regulated, and the disadvantages caused by metal agglomeration into nanoparticles are avoided, such as avoiding Fenton side reactions, reducing the corrosion of carbon-based supports, and further improving the catalytic activity and stability of catalysts.

[0070] Figure 3 The Raman spectra of Sm / SeNC, NC, and Sm / NC prepared in Example 1, Comparative Example 1, and Comparative Example 3 are shown. The results indicate that Sm / SeNC and Sm / NC exhibit Ig... D / I G The value is close, at 0.92, compared to NC's I. D / I G The decrease in the I value from 0.96 indicates that Sm / SeNC and Sm / NC have a higher degree of graphitization and a more regular carbon framework, resulting in better structural stability and providing reliable structural support for electrocatalytic reactions. Furthermore, the I values ​​of Sm / SeNC and Sm / NC... D / I G The close values ​​indicate that the incorporation of Se did not disrupt the carbon skeleton structure, and the carbon skeleton structure remains relatively stable. The promoting effect of Se on ORR reaction activity does not mainly come from adjusting the number of defects in the support or increasing the Sm loading, but rather from optimizing the electronic properties of the active sites by regulating the local coordination environment and electronic structure around the Sm active sites, and thus enhancing the ORR catalytic performance through synergistic effects with the Sm active sites.

[0071] Figure 4 The HAADF-STEM and EDS spectra of the Sm / SeNC prepared in Example 1 are shown. The results show that Se, after being incorporated into the Sm single-atom catalyst, still maintains a regular carbon framework morphology. Elemental mapping analysis confirms the uniform distribution of elements such as Sm, Se, N, C, and O.

[0072] Figure 5XPS images of Sm / SeNC and Sm / NC prepared in Example 1 and Comparative Example 3 are shown. The results show that the introduction of Se shifts the N1s binding energy, and Se is successfully incorporated into the catalyst, forming Se-C, Se-N, and Se-O structures, indicating that Se can regulate the surface chemical environment and electronic structure of Sm / NC.

[0073] 2. Performance Testing: (1) Oxygen reduction performance test Oxygen reduction activity was evaluated using linear sweep voltammetry in a three-electrode system. First, the catalysts obtained in Examples 1-6 and Comparative Examples 1-5 were mixed with solvents such as water, perfluorosulfonic acid (Nafion), and ethanol, and ultrasonically dispersed to form a catalyst ink. This ink was then drop-coated onto the surface of a polished glassy carbon electrode and allowed to dry naturally to obtain the working electrode. A three-electrode system was constructed using this working electrode, a Hg / HgO reference electrode, and a platinum wire counter electrode. Oxygen was bubbled into a 0.1 M KOH alkaline electrolyte for at least 30 min to achieve oxygen saturation. Linear sweep voltammetry was performed at a scanning voltage of 0.2-1.05 V and a scanning rate of 10 mV / s to obtain the following results: Figure 6 The oxygen reduction polarization curve, The results showed that NC had the worst oxygen reduction activity, with a half-wave potential E 1 / 2 At 0.832 V, it is indicated that the oxygen reduction electrocatalytic performance of N-doped carbon supports is weak. The oxygen reduction activity of Sm / NC (0.875 V) is better than that of NC, but lower than that of Sm / SeNC (0.89 V). The incorporation of Se shifts the onset potential to the positive direction, increases the half-wave potential, and increases the limiting diffusion current density. This indicates that Se doping modulates the coordination environment of the Sm single-atom catalyst, achieves high selectivity of the four-electron pathway, and improves the oxygen reduction activity of the catalyst.

[0074] (2) Constant current charge-discharge stability test of zinc-air battery The catalysts obtained in Examples 1-6 and Comparative Examples 1-5 were used as air cathodes and assembled into zinc-air batteries with zinc sheet anodes and electrolytes. The electrolytes consisted of 6 M potassium hydroxide and 0.2 M zinc acetate, and the test current was 5 mA cm⁻¹. -2 The duration of a single charge-discharge cycle is 30 minutes, and the voltage change curve over time is recorded as follows: Figure 7 To evaluate the performance of the catalyst in practical battery devices.

[0075] The results showed that the Pt / C battery could only operate stably for 50 hours, and the polarization voltage difference increased significantly. Without the addition of Se, the stable operating time of the Sm / NC battery increased to 57 hours. After the addition of Se, the stability of the Sm / SeNC battery was significantly improved. Finally, the zinc-air battery prepared using Sm / SeNC as the air cathode could operate stably for at least 100 hours, with a stable voltage plateau and no significant change in the polarization voltage difference. This indicates that the Sm / SeNC provided in this application exhibits excellent output performance and cycle stability in zinc-air batteries.

[0076] The catalysts obtained in Examples 1-6 and Comparative Examples 1-5 were tested for oxygen reduction performance and constant current charge-discharge stability in zinc-air batteries. The starting point, half-wave potential, limiting diffusion current density, and stable operating time are shown in Table 1.

[0077] Table 1 As can be seen from Table 1: (1) As can be seen from Examples 1-6, the Se-doped Sm single-atom catalyst system of this application can balance the adsorption and desorption of oxygen-containing intermediates, improve the four-electron selectivity, reduce the occurrence of two-electron pathways, avoid oxidation of carbon nitride support and active center, and its half-wave potential, limiting diffusion current density and stable operating time are more excellent.

[0078] (2) By comparing Example 1 with Examples 4-5, it can be seen that when the mass ratio of Se source to Sm / NC single-atom catalyst is controlled at (0.03-0.10):1, the more positive the half-wave potential, the greater the limiting diffusion current density, and the longer the stable operation time of the zinc-air battery, which can further improve the oxygen reduction activity.

[0079] (3) By comparing Example 1 with Comparative Examples 1-2, it can be seen that the oxygen reduction electrocatalytic performance of the carbon nitride support alone is very poor, while the oxygen reduction activity of Sm / SeNC can almost reach the level of commercial Pt / C. By comparing with Comparative Examples 3-4, the excellent catalytic activity of Sm / SeNC is not due to the presence of Sm or Se alone, nor does it come from the carbon nitride support itself. The incorporation of Se can have the effect of shifting the d-band center of Sm downward, thereby changing the adsorption relationship of oxygen-containing intermediates. Moreover, Sm and Se are in local coordination environments, and the oxygen reduction activity of the catalyst is improved through synergistic effect.

[0080] (4) As can be seen from Example 1 and Comparative Example 5, the combination of Se and Sm has more advantages in constructing a highly stable oxygen reduction catalyst compared with the combination of Se and Fe. The rare earth Sm single-atom catalyst has a unique 4f electronic structure and strong resistance to Fenton, which can overcome the free radical attack generated by the traditional transition metal Fe single-atom catalyst in the electrochemical reaction, and avoid adverse phenomena such as active site destruction, carbon support corrosion and reduced battery device life.

[0081] In summary, this application, by incorporating Se into the Sm single-atom catalyst system, modulates the surface chemical environment and local electronic structure of the Sm single-atom catalyst system, thereby effectively regulating the electronic state of rare earth Sm atoms and the adsorption behavior of key intermediates in the oxygen reduction reaction. This improves the oxygen reduction activity, device application stability, and device output performance in alkaline electrolyte and zinc-air battery tests. The zinc-air battery provided by this application can operate stably for at least 100 hours, demonstrating excellent application potential in battery devices.

[0082] The applicant declares that the above description is only a specific implementation of this application, but the protection scope of this application is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this application fall within the protection and disclosure scope of this application.

Claims

1. A Se-doped Sm single-atom catalyst for oxygen reduction electrocatalysis, characterized in that, The catalyst comprises a carbon nitride support and a single-atom metal active component dispersed thereon; The central active atoms of the metal active component are Sm atoms and Se atoms.

2. The Se-doped Sm single-atom catalyst according to claim 1, characterized in that, The Se is incorporated into the carbon nitride support framework to form Se-C, Se-N, and Se-O coordination structures, and to regulate the charge distribution around the Sm sites; And / or, the carbon nitride support includes any one or a combination of at least two of metal-organic framework-derived carbon nitride, graphene-based carbon nitride, or carbon nanotube-based carbon nitride.

3. A method for preparing a Se-doped Sm single-atom catalyst according to claim 1 or 2, characterized in that, The preparation method includes the following steps: S1: Add carbon nitride support and Sm source to mixed molten salt system to obtain Sm / NC single-atom catalyst after reaction; S2: The Sm / NC single-atom catalyst obtained in step S1 is doped with Se powder by vapor deposition to obtain the Se-doped Sm single-atom catalyst.

4. The method for preparing the Se-doped Sm single-atom catalyst according to claim 3, characterized in that, The preparation method includes the following steps: (1) Grind and mix the Sm source with the carbon nitride support to obtain a mixture; (2) The mixture obtained in step (1) is wrapped with a mixed molten salt system, and after the first calcination, it is post-treated to obtain the Sm / NC single-atom catalyst; (3) Under a protective atmosphere, the Se source is introduced into the Sm / NC single-atom catalyst by vapor deposition, and after a second calcination, the Se-doped Sm single-atom catalyst is obtained.

5. The method for preparing the Se-doped Sm single-atom catalyst according to claim 4, characterized in that, In step (1), the Sm source includes any one or a combination of at least two of samarium chloride, samarium acetate hydrate, or samarium nitrate hexahydrate; And / or, the carbon nitride support is prepared by pyrolysis of ZIF-8 / 1,10-phenanthroline precursor at 800-1100°C under a protective atmosphere; And / or, the mass ratio of the Sm source to the carbon nitride support is (0.05-0.10):1; And / or, the mixed molten salt system described in step (2) includes a combination of potassium chloride and lithium chloride; And / or, the mass ratio of potassium chloride to lithium chloride is (0.5-2):

1.

6. The method for preparing the Se-doped Sm single-atom catalyst according to claim 4 or 5, characterized in that, In step (2), the first calcination is carried out in a tubular furnace; And / or, the atmosphere of the first calcination is an inert gas, preferably argon; And / or, the heating rate of the first calcination is 2-10 °C / min; And / or, the holding temperature for the first calcination is 600-900℃; And / or, the holding time for the first calcination is 1-3 h.

7. The method for preparing the Se-doped Sm single-atom catalyst according to any one of claims 4-6, characterized in that, The post-processing described in step (2) includes washing and drying; And / or, the washing solution used in the washing process is successively anhydrous ethanol and deionized water; And / or, the number of washes is 2-5; And / or, the drying is either forced air drying or vacuum drying; And / or, the drying temperature is 60-80℃, and the drying time is 6-12 h.

8. The method for preparing the Se-doped Sm single-atom catalyst according to any one of claims 4-7, characterized in that, The vapor deposition process described in step (3) includes placing Se powder at the front end of a tubular furnace and placing the Sm / NC catalyst at the rear end of the tubular furnace for a second calcination. And / or, the vapor deposition is carried out under an inert atmosphere, preferably argon; And / or, the heating rate of the vapor deposition is 2-10 °C / min; And / or, the holding temperature for the vapor deposition is 600-900℃; And / or, the holding time for the vapor deposition is 1-3 h.

9. The method for preparing the Se-doped Sm single-atom catalyst according to any one of claims 4-8, characterized in that, The mass ratio of the Se source to the Sm / NC single-atom catalyst in step (3) is (0.03-0.10):

1.

10. The application of a Se-doped Sm single-atom catalyst according to claim 1 or 2 in oxygen reduction electrocatalysis; And / or, the Se-doped Sm single-atom catalyst is used in the oxygen reduction electrode.

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