Carbon-based monatomic catalyst doped with five non-metallic elements as well as preparation method and application of carbon-based monatomic catalyst

Abstract

The invention relates to the technical field of catalytic materials, in particular to a carbon-based monatomic catalyst doped with five non-metallic elements and a preparation method and application of the carbon-based monatomic catalyst doped with the five non-metallic elements. An organic precursor (MOF-coated POSFN-CTP) rich in five non-metallic element heteroatoms is prepared through a simple coprecipitation method at the room temperature; and annealing to obtain the carbon material (POSFNC) doped with five non-metallic elements. On the basis, the POSFNC is further impregnated with a transition metal precursor, annealing is carried out again, and the carbon-based monatomic catalyst doped with five non-metallic elements is successfully synthesized. The carbon-based monatomic catalyst with a hollow porous structure and five non-metallic element heteroatoms uniformly distributed can be constructed through the method, the synthesis process has the advantages of simplicity, convenience, economy and environmental protection, and the ORR activity and stability of the prepared catalyst exceed those of a commercial Pt / C catalyst.

Description

Technical Field

[0001] The present invention relates to the technical field of catalytic materials, and in particular to a carbon-based single-atom catalyst doped with five non-metallic elements, a preparation method thereof, and an application thereof. Background Art

[0002] As a new type of energy storage device, zinc-air batteries (ZABs) rely on the reversible redox reaction between the zinc negative electrode and the air positive electrode to achieve the storage and release of electrochemical energy. Due to its advantages such as high energy density (1086 Wh kg -1 ), relatively high energy conversion efficiency, and environmental friendliness, ZABs have received extensive attention in the field of energy storage. The oxygen reduction reaction (ORR) is a key reaction during the discharge process of ZABs. Its reaction mechanism is complex and the kinetic rate is slow, significantly limiting the energy conversion efficiency of ZABs. Currently, the most widely used and high-performance ORR electrode material is the platinum-based catalyst (Pt / C). However, platinum has limited reserves on the earth, high costs, and cannot simultaneously possess characteristics such as portability, efficiency, and low cost, making it difficult to achieve large-scale commercial applications.

[0003] In recent years, metal-nitrogen-carbon (M-N-C) catalysts, especially iron-based Fe-N-C catalysts, have become one of the research hotspots in this field due to their low cost, rich resources, and ORR activity comparable to that of Pt / C catalysts and good stability in alkaline environments. To further improve the ORR performance, researchers have optimized the catalyst performance by regulating the types, configurations, and concentrations of doped elements.

[0004] However, it is still a huge challenge to synthesize a catalyst doped with multiple non-metallic elements with controllable composition and uniform atomic distribution. Currently, the related technologies mainly focus on the doping of single or dual non-metallic elements, and the activity and stability of the catalysts are poor.

[0005] Therefore, the existing technologies still need to be improved and developed. Summary of the Invention

[0006] In view of the above deficiencies of the prior art, the purpose of the present invention is to provide a carbon-based single-atom catalyst doped with five non-metallic elements, a preparation method thereof, and an application thereof, aiming to solve the problem of poor activity and stability of existing catalysts.

[0007] The technical solution of the present invention is as follows:

[0008] A preparation method of a carbon-based single-atom catalyst doped with five non-metallic elements, comprising the steps:

[0009] Mix the MOF material with a solvent to obtain a first solution;

[0010] Mix hexachlorocyclotriphosphazene, 4,4'-dihydroxydiphenyl sulfone, and tetrafluoroquinone with a solvent to obtain a second solution;

[0011] Mix the first solution, the second solution, and an organic base to obtain MOF@POSFN-CTP;

[0012] Perform a first annealing treatment on the MOF@POSFN-CTP to obtain POSFNC;

[0013] Mix the POSFNC with a transition metal precursor and a solvent to obtain POSFNC with the transition metal precursor adsorbed on its surface;

[0014] Perform a second annealing treatment on the POSFNC with the transition metal precursor adsorbed on its surface to obtain a carbon-based single-atom catalyst doped with five non-metal elements.

[0015] The preparation method of the carbon-based single-atom catalyst doped with five non-metal elements, wherein the MOF material includes one or more of ZIF-8, ZIF-67, MOF-74, and UiO-66-NH2.

[0016] The preparation method of the carbon-based single-atom catalyst doped with five non-metal elements, wherein the mass ratio of the hexachlorocyclotriphosphazene, the 4,4'-dihydroxydiphenyl sulfone, and the tetrafluoroquinone is (3 - 5):(4 - 6):(3 - 5).

[0017] The preparation method of the carbon-based single-atom catalyst doped with five non-metal elements, wherein the concentration of the first solution is 10 g / L - 20 g / L; the volume ratio of the first solution to the second solution is (1 - 2):(4 - 6); the volume ratio of the second solution to the organic base is (50 - 100):1.

[0018] The preparation method of the carbon-based single-atom catalyst doped with five non-metal elements, wherein the organic base includes one or more of triethylamine, pyridine, and 4-dimethylaminopyridine; and / or, the transition metal precursor includes one of an iron precursor, a nickel precursor, a cobalt precursor, and a manganese precursor.

[0019] The preparation method of the carbon-based single-atom catalyst doped with five non-metal elements, wherein the mass ratio of the POSFNC to the transition metal precursor is (30 - 50):(2 - 5).

[0020] The preparation method of the carbon-based single-atom catalyst doped with five non-metal elements, wherein the temperature of the first annealing treatment is 900°C - 1100°C, the time of the first annealing treatment is 1h - 3h, and the heating rate of the first annealing treatment is 2°C / min - 5°C / min;

[0021] and / or, the temperature of the second annealing treatment is 900°C - 1100°C, the time of the second annealing treatment is 1h - 3h, and the heating rate of the second annealing treatment is 2°C / min - 5°C / min;

[0022] and / or, the first annealing treatment and the second annealing treatment are carried out in an inert atmosphere.

[0023] A carbon-based single-atom catalyst doped with five non-metal elements, which is prepared by using the preparation method of the carbon-based single-atom catalyst doped with five non-metal elements.

[0024] The carbon-based single-atom catalyst doped with five non-metal elements, wherein the carbon-based single-atom catalyst doped with five non-metal elements includes a hollow porous carbon substrate, transition metals distributed on the surface of the hollow porous carbon substrate in the form of single atoms, and P element, O element, S element, F element, and N element distributed on the surface of the hollow porous carbon substrate.

[0025] An application of a carbon-based single-atom catalyst doped with five non-metal elements in a zinc-air battery.

[0026] Beneficial effects: The present invention provides a carbon-based single-atom catalyst doped with five non-metal elements, a preparation method thereof, and an application thereof. The preparation method includes the steps of: mixing a MOF material with a solvent to obtain a first solution; mixing hexachlorocyclotriphosphazene, 4,4'-dihydroxydiphenyl sulfone, tetrafluorohydroquinone with a solvent to obtain a second solution; mixing the first solution, the second solution and an organic base to obtain MOF@POSFN-CTP; performing a first annealing treatment on the MOF@POSFN-CTP to obtain POSFNC; mixing the POSFNC with a transition metal precursor and a solvent to obtain POSFNC with the transition metal precursor adsorbed on the surface; performing a second annealing treatment on the POSFNC with the transition metal precursor adsorbed on the surface to obtain a carbon-based single-atom catalyst doped with five non-metal elements. The present invention prepares an organic precursor (MOF@POSFN-CTP) rich in five non-metal heteroatoms by a simple co-precipitation method at room temperature, and obtains a carbon material (POSFNC) doped with five non-metal elements after annealing; on this basis, the POSFNC is further impregnated with a transition metal precursor and annealed again to successfully synthesize a carbon-based single-atom catalyst doped with five non-metal elements. Through the above approach, a carbon-based single-atom catalyst with a hollow porous structure and uniform distribution of five non-metal heteroatoms can be constructed. The synthesis process has the advantages of simplicity, economy, and environmental protection, and the ORR activity and stability of the prepared catalyst exceed those of commercial Pt / C catalysts. Description of the Drawings

[0027] Figure 1 It is a schematic process flow diagram for the preparation of a carbon-based single-atom catalyst doped with five non-metal elements according to the present invention;

[0028] Figure 2 It is a scanning electron microscope image of ZIF-8@POSFN-CTP in Example 1;

[0029] Figure 3 It is a transmission electron microscope image of ZIF-8@POSFN-CTP in Example 1;

[0030] Figure 4 It is a crystal phase structure diagram of ZIF-8@POSFN-CTP in Example 1;

[0031] Figure 5 It is a transmission electron microscope image of POSFNC in Example 1;

[0032] Figure 6 It is a scanning transmission electron microscope image of Fe / POSFNC in Example 1;

[0033] Figure 7 It is an EDS energy spectrum element distribution diagram of Fe / POSFNC in Example 1;

[0034] Figure 8 It is a linear sweep polarization curve test diagram with the Fe / POSFNC catalyst as the working electrode in Example 1;

[0035] Figure 9 It is a stability test diagram with the Fe / POSFNC catalyst as the working electrode in Example 1. Detailed implementation manners

[0036] The present invention provides a carbon-based single-atom catalyst doped with five non-metallic elements, its preparation method and application. To make the purpose, technical solution and effects of the present invention clearer and more definite, the present invention is further described in detail below. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0037] Those skilled in the art of the present technology can understand that, unless otherwise defined, all terms (including technical terms and scientific terms) used here have the same meaning as the general understanding of those of ordinary skill in the art to which the present invention belongs. It should also be understood that terms such as those defined in a general dictionary should be understood to have a meaning consistent with the meaning in the context of the prior art, and will not be interpreted with an idealized or overly formal meaning unless specifically defined as here.

[0038] Zhang and his team used the liquid-phase exfoliation method to layer multi-layered biocarbon to form a graphene-like structure co-doped with multiple heteroatoms (Fe, N, S), and found that the ORR performance of this catalyst is better than that of commercial Pt / C catalysts, indicating that the introduction of sulfur elements effectively regulates the electronic structure and improves the catalyst performance. The Gibaek team developed carbon nanofibers (CNFs) with a unique three-dimensional structure through electrospinning technology, loaded bimetals (Fe and Co) in them, and doped non-metallic elements (N and S) at the same time. Compared with the metal CNFs catalysts doped only with N and S, the FeCo-N,S@CNFs catalyst shows excellent activity (E onset = 0.89V, E 1 / 2 = 0.85V) and stability (about 14 hours), its performance is close to that of commercial Pt / C catalysts, and it shows strong methanol tolerance under alkaline conditions. Luo et al. synthesized a series of multi-stage MOF composite-derived FeCo alloy-functionalized mesoporous carbon materials by a two-step method, which included the synthesis of MOF composites by coordination-induced self-assembly and a high-temperature carbonization process. This catalyst has a large specific surface area, uniformly distributed alloy nanoparticles, and excellent oxygen binding energy, showing good ORR electrocatalytic performance. However, existing methods cannot synthesize catalysts doped with multiple non-metallic elements with controllable components and uniform atomic distribution, and the activity and stability of the catalysts also need to be further improved.

[0039] Based on this, as Figure 1 shown, the present invention provides a method for preparing a carbon-based single-atom catalyst doped with five non-metal elements, comprising the steps of:

[0040] Step S10: Mix the MOF material with a solvent to obtain a first solution;

[0041] Step S20: Mix hexachlorocyclotriphosphazene, 4,4'-dihydroxydiphenyl sulfone, tetrafluoroquinol with a solvent to obtain a second solution;

[0042] Step S30: Mix the first solution, the second solution and an organic base to obtain MOF@POSFN-CTP;

[0043] Step S40: Perform a first annealing treatment on the MOF@POSFN-CTP to obtain POSFNC;

[0044] Step S50: Mix the POSFNC with a transition metal precursor and a solvent to obtain POSFNC with the transition metal precursor adsorbed on the surface;

[0045] Step S60: Perform a second annealing treatment on the POSFNC with the transition metal precursor adsorbed on the surface to obtain a carbon-based single-atom catalyst doped with five non-metal elements.

[0046] In this embodiment, an organic precursor (MOF@POSFN-CTP) rich in five non-metal heteroatoms is prepared by a simple co-precipitation method at room temperature, and a carbon material (POSFNC) doped with five non-metal elements is obtained after annealing; on this basis, the POSFNC is further impregnated with a transition metal precursor and annealed again to successfully synthesize a carbon-based single-atom catalyst doped with five non-metal elements. Through the above approach, a carbon-based single-atom catalyst with a hollow porous structure and uniform distribution of five non-metal heteroatoms can be constructed. The synthesis process has the advantages of simplicity, economy and environmental protection, and the ORR activity and stability of the prepared catalyst exceed those of commercial Pt / C catalysts.

[0047] Specifically, the present invention grows a covalent triazine polymer rich in five non-metallic elements, namely P, O, S, F, and N, on the surface of MOF by a simple co-precipitation method, and successfully introduces five heteroatoms of P, O, S, F, and N through annealing treatment. The adopted synthesis method has simple processes, is economical, environmentally friendly, and can be prepared on a large scale; due to the typical core-shell structure of MOF@POSFN-CTP, a catalyst with a hollow porous carbon structure can be constructed under the action of the Kirkenda11 effect during annealing, which is beneficial to mass transfer during the reaction, and the morphology of the catalyst can be regulated by changing the components, solvents, synthesis conditions, etc. of MOF; the carbon-based single-atom catalyst doped with five non-metallic elements prepared by this method has five non-metallic element heteroatoms uniformly distributed on the carbon substrate, and the electronic structure of the metal active center is modulated through the remote electron induction effect, making it have high ORR activity, and the metal is dispersed in the form of single atoms with high atomic utilization rate. Moreover, the electrocatalyst prepared by this method is derived from MOF, has a high degree of graphitization, good conductivity, a large specific surface area, and shows excellent catalytic activity and stability in ORR in alkaline electrolyte that exceed those of commercial Pt / C.

[0048] In some embodiments, the MOF material includes one or more of ZIF-8, ZIF-67, MOF-74, and UiO-66-NH2. Using the above MOF materials to provide metal-organic frameworks, the catalysts prepared from them have a high degree of graphitization, good conductivity, and a large specific surface area.

[0049] In some embodiments, the preparation method of the MOF material includes the steps:

[0050] Step S100: Dissolve the transition metal salt in a solvent and stir to obtain solution A;

[0051] Step S200: Dissolve the organic ligand in a solvent and stir to obtain solution B;

[0052] Step S300: Slowly add solution B to solution A and perform purification treatment to obtain the MOF material.

[0053] In some embodiments, the transition metal salt includes but is not limited to zinc nitrate, zinc chloride, zinc acetate, etc.; the concentration of solution A is 0.1 mol / L - 0.2 mol / L, the concentration of solution B is 0.4 mol / L - 0.8 mol / L, and the volume ratio of solution A to solution B is (1 - 2):(1 - 2).

[0054] In a preferred embodiment, the concentration of solution A is 0.1 mol / L, the concentration of solution B is 0.4 mol / L, and the volume ratio of solution A to solution B is 1:1.

[0055] In some embodiments, the time for the purification treatment is 12 h - 24 h.

[0056] In some embodiments, the solvent used in the preparation method may be, but is not limited to, one or more of methanol, ethanol, water, and DMF.

[0057] In some embodiments, the mass ratio of the hexachlorocyclotriphosphazene, the 4,4'-dihydroxydiphenyl sulfone, and the tetrafluorohydroquinone is (3 - 5):(4 - 6):(3 - 5). At this ratio, the modulation effect of the five non-metal element heteroatoms on the electronic structure of the metal active center is optimal, and the ORR activity and stability of the catalyst are the highest.

[0058] In some embodiments, in step S20, the mass of the hexachlorocyclotriphosphazene is 30 - 50 mg, the mass of the 4,4'-dihydroxydiphenyl sulfone is 40 - 60 mg, the mass of the tetrafluorohydroquinone is 30 - 50 mg, and the volume of the solvent is 20 - 40 mL. Using the hexachlorocyclotriphosphazene, the 4,4'-dihydroxydiphenyl sulfone, and the tetrafluorohydroquinone to provide five non-metal elements, namely P, O, S, F, and N, and controlling them within the above mass ratio range can grow a layer of covalent triazine polymer rich in five non-metal elements, namely P, O, S, F, and N, on the surface of the MOF. And by regulating the mass ratio, the doping amounts of the five non-metal elements can be controlled to obtain catalysts with different doping amounts of the five non-metal elements.

[0059] In a preferred embodiment, the mass ratio of the hexachlorocyclotriphosphazene, the 4,4'-dihydroxydiphenyl sulfone, and the tetrafluorohydroquinone is 3:4:3. At this time, the solvent only needs to be 1 / 4 of the total mass of the hexachlorocyclotriphosphazene, the 4,4'-dihydroxydiphenyl sulfone, and the tetrafluorohydroquinone.

[0060] In some embodiments, the concentration of the first solution is 10 g / L - 20 g / L; the volume ratio of the first solution to the second solution is (1 - 2):(4 - 6); controlled at the concentration and volume ratio, a covalent triazine compound rich in five non-metal element heteroatoms, namely MOF@POSFN-CTP, can be formed on the surface of the MOF.

[0061] In some embodiments, the volume ratio of the second solution to the organic base is (50 - 100):1. Using the organic base as a catalyst enables the hexachlorocyclotriphosphazene, 4,4'-dihydroxydiphenyl sulfone, and tetrafluorohydroquinone to form a covalent triazine polymer rich in five non-metal element heteroatoms on the surface of the MOF; and controlling the addition amount of the organic base within the above range can improve the reaction efficiency and does not waste raw materials.

[0062] In a preferred embodiment, the volume ratio of the second solution to the organic base is 100:1.

[0063] In some embodiments, the organic base includes one or more of triethylamine, pyridine, and 4-dimethylaminopyridine.

[0064] In some embodiments, the transition metal precursor includes, but is not limited to, one of an iron precursor, a nickel precursor, a cobalt precursor, and a manganese precursor. The transition metal precursor provides metal atoms for the catalyst to form a carbon-based single-atom catalyst.

[0065] In some embodiments, the iron precursor includes, but is not limited to, one or more of iron nitrate, iron chloride, iron phthalocyanine, and iron acetylacetonate; the nickel precursor includes, but is not limited to, one or more of nickel nitrate, nickel acetate, nickel chloride, and nickel sulfate; the cobalt precursor includes, but is not limited to, one or more of cobalt nitrate, cobalt acetate, cobalt chloride, and cobalt sulfate; the manganese precursor includes, but is not limited to, one or more of manganese nitrate, manganese acetate, manganese chloride, and manganese sulfate.

[0066] In some embodiments, the mass ratio of the POSFNC to the transition metal precursor is (30 - 50):(2 - 5). At this ratio, Fe is loaded on the carbon support in the form of single atoms.

[0067] Specifically, in step S50, the mass of the POSFNC is 30 - 50 mg, the mass of the transition metal precursor is 2 - 5 mg, and the volume of the solvent is 30 - 50 mL.

[0068] In a preferred embodiment, the mass of the POSFNC is 30 mg, the mass of the transition metal precursor is 3 mg, and the volume of the solvent is 50 mL.

[0069] In some embodiments, the temperature of the first annealing treatment is 900°C - 1100°C, the time of the first annealing treatment is 1 h - 3 h, and the heating rate of the first annealing treatment is 2°C / min - 5°C / min; and / or, the temperature of the second annealing treatment is 900°C - 1100°C, the time of the second annealing treatment is 1 h - 3 h, and the heating rate of the second annealing treatment is 2°C / min - 5°C / min; and / or, the first annealing treatment and the second annealing treatment are carried out in an inert atmosphere. Under these annealing conditions, the degree of graphitization of the catalyst is high and the conductivity is good.

[0070] In some embodiments, the inert atmosphere includes, but is not limited to, one or more of argon, helium, and neon.

[0071] In a preferred embodiment, the parameters of the first annealing treatment and the second annealing treatment are as follows: the temperature is 900 °C, the time is 3 h, the heating rate is 5 °C / min, and it is carried out in an argon atmosphere.

[0072] In addition, the present invention also provides a carbon-based single-atom catalyst doped with five non-metallic elements, which is prepared by using the preparation method of the carbon-based single-atom catalyst doped with five non-metallic elements.

[0073] In this embodiment, the carbon-based single-atom catalyst doped with five non-metallic elements prepared by this method has five non-metallic element heteroatoms uniformly distributed on the hollow porous carbon substrate, and modulates the electronic structure of the metal active center through the remote electron induction effect, so that it has high ORR activity, and the metal is dispersed in the form of single atoms, with high atomic utilization rate. Moreover, the electrocatalyst prepared by this method is derived from MOF, has a high degree of graphitization, good conductivity, a large specific surface area, and shows excellent catalytic activity and stability in the ORR in alkaline electrolyte that exceed those of commercial Pt / C.

[0074] In some embodiments, the carbon-based single-atom catalyst doped with five non-metallic elements includes a hollow porous carbon substrate, a transition metal distributed on the surface of the hollow porous carbon substrate in the form of single atoms, and P element, O element, S element, F element, and N element distributed on the surface of the hollow porous carbon substrate.

[0075] In addition, the present invention also provides an application of the carbon-based single-atom catalyst doped with five non-metallic elements in a zinc-air battery.

[0076] The following further gives examples to illustrate the present invention in detail. It should also be understood that the following examples are only used to further illustrate the present invention and cannot be construed as limiting the protection scope of the present invention. Some non-essential improvements and adjustments made by those skilled in the art based on the above content of the present invention all fall within the protection scope of the present invention.

[0077] Example 1

[0078] This example provides a carbon-based Fe single-atom catalyst doped with five non-metallic elements, and the preparation steps are as follows:

[0079] 1) Add 3 mmol of zinc nitrate to 30 mL of methanol, and stir for 10 min to obtain solution A. At the same time, add 12 mmol of 2-methylimidazole to 30 mL of methanol, and stir for 10 min to obtain solution B. Slowly add solution B to solution A under stirring, and centrifuge after stirring for 12 h to obtain ZIF-8.

[0080] 100 mg of dried ZIF-8 was added to 10 mL of methanol, and after stirring for 10 min, solution C was obtained. Meanwhile, 30 mg of hexachlorocyclotriphosphazene, 40 mg of 4,4'-dihydroxydiphenyl sulfone, and 30 mg of tetrafluorohydroquinone were mixed and dissolved in 25 mL of methanol, and after stirring for 10 min, solution D was obtained.

[0081] At room temperature, solution D was slowly added to solution C and 0.25 mL of triethylamine was added, and after stirring for 15 h, ZIF-8@POSFN-CTP was obtained. The scanning electron microscope image and transmission electron microscope image of the sample are shown in Figure 2 and Figure 3 respectively. It can be seen that the surface of the dodecahedral ZIF-8 is obviously covered with a layer of polymer, and the thickness is about 20 nm. The crystal phase structure diagram is shown in Figure 4 respectively. It can be seen that introducing a heteroatom-rich covalent triazine polymer on the surface of ZIF-8 does not affect the crystal phase structure of ZIF-8.

[0082] 2) ZIF-8@POSFN-CTP was placed in a tube furnace for annealing. The annealing temperature was 900 °C; the annealing time was 3 h; the annealing atmosphere was argon; the heating rate was 5 °C min -1 , and after annealing treatment, POSFNC was obtained. The transmission electron microscope image of the sample is shown in Figure 5 respectively, and it is a hollow porous carbon structure.

[0083] 30 mg of POSFNC and 3 mg of iron nitrate were added to 50 mL of ethanol, and after ultrasonic impregnation, ethanol was removed by rotary evaporation, and then placed in a tube furnace for annealing. The annealing temperature was 900 °C; the annealing time was 3 h; the annealing atmosphere was argon; the heating rate was 5 °C min -1 , and after annealing treatment, Fe / POSFNC was obtained. The scanning transmission electron microscope image with double spherical aberration correction and the EDS energy spectrum element distribution map of the sample are shown in Figure 6 and Figure 7 respectively. Fe is dispersed in the form of single atoms, and the five non-metal element heteroatoms are uniformly distributed on the carbon substrate.

[0084] 3) Electrochemical tests were all carried out on a CHI 760E electrochemical workstation.

[0085] The prepared Fe / POSFNC catalyst was selected as the working electrode, the graphite rod as the counter electrode, and the silver / silver chloride electrode as the reference electrode to form a three-electrode system. Electrochemical tests were carried out in a 0.1 mol L -1 KOH solution, and linear sweep polarization curve tests were carried out on it at a sweep rate of 10 mV s -1 . The test results are shown in Figure 8As shown, the half-wave potential of the Fe / POSFNC catalyst reaches 0.93 V, far exceeding that of the commercial Pt / C catalyst (0.86 V), indicating that the activity of Fe / POSFNC for catalyzing ORR in alkaline electrolyte is much higher than that of the commercial Pt / C. The stability test is as Figure 9 shown. After continuous electrolysis of the Fe / POSFNC catalyst for 25 h, the current density only decays by about 5%, and its stability is also better than that of the commercial Pt / C catalyst.

[0086] In summary, the present invention provides a carbon-based single-atom catalyst doped with five non-metal elements, its preparation method and application. The preparation method includes the steps of: mixing a MOF material with a solvent to obtain a first solution; mixing hexachlorocyclotriphosphazene, 4,4'-dihydroxydiphenyl sulfone, tetrafluorohydroquinone with a solvent to obtain a second solution; mixing the first solution, the second solution and an organic base to obtain MOF@POSFN-CTP; performing a first annealing treatment on the MOF@POSFN-CTP to obtain POSFNC; mixing the POSFNC with a transition metal precursor and a solvent to obtain POSFNC with a surface-adsorbed transition metal precursor; performing a second annealing treatment on the POSFNC with a surface-adsorbed transition metal precursor to obtain a carbon-based single-atom catalyst doped with five non-metal elements. The present invention prepares an organic precursor (MOF@POSFN-CTP) rich in five non-metal heteroatoms by a simple co-precipitation method at room temperature, and obtains a carbon material (POSFNC) doped with five non-metal elements after annealing; on this basis, the POSFNC is further impregnated with a transition metal precursor and annealed again to successfully synthesize a carbon-based single-atom catalyst doped with five non-metal elements. Through the above approach, a carbon-based single-atom catalyst with a hollow porous structure and uniform distribution of five non-metal heteroatoms can be constructed. The synthesis process has the advantages of simplicity, economy and environmental protection, and the ORR activity and stability of the prepared catalyst exceed those of the commercial Pt / C catalyst.

[0087] It should be understood that the application of the present invention is not limited to the above examples. For those of ordinary skill in the art, improvements or transformations can be made according to the above description, and all such improvements and transformations should fall within the protection scope of the appended claims of the present invention.

Claims

1. A preparation method of a carbon-based single-atom catalyst doped with five non-metal elements, characterized in that Including the steps: Mix the MOF material with a solvent to obtain a first solution; Mix hexachlorocyclotriphosphazene, 4,4'-dihydroxydiphenyl sulfone, tetrafluorohydroquinone with a solvent to obtain a second solution; Mix the first solution, the second solution and an organic base to obtain MOF@POSFN-CTP; Perform a first annealing treatment on the MOF@POSFN-CTP to obtain POSFNC; Mix the POSFNC with a transition metal precursor and a solvent to obtain POSFNC with the transition metal precursor adsorbed on the surface; Perform a second annealing treatment on the POSFNC with the transition metal precursor adsorbed on the surface to obtain a carbon-based single-atom catalyst doped with five non-metal elements.

2. The preparation method of the carbon-based single-atom catalyst doped with five non-metal elements according to claim 1, characterized in that, The MOF material includes one or more of ZIF-8, ZIF-67, MOF-74, UiO-66-NH2.

3. The preparation method of the carbon-based single-atom catalyst doped with five non-metallic elements according to claim 1, characterized in that, The mass ratio of the hexachlorocyclotriphosphazene, the 4,4'-dihydroxydiphenyl sulfone and the tetrafluorohydroquinone is (3-5):(4-6):(3-5).

4. The preparation method of the carbon-based single-atom catalyst doped with five non-metal elements according to claim 1, characterized in that, The concentration of the first solution is 10g / L - 20gL; the volume ratio of the first solution to the second solution is (1-2):(4-6); the volume ratio of the second solution to the organic base is (50-100):

1.

5. The preparation method of the carbon-based single-atom catalyst doped with five non-metal elements according to claim 1, characterized in that, The organic base includes one or more of triethylamine, pyridine, 4-dimethylaminopyridine; and / or, the transition metal precursor includes one of an iron precursor, a nickel precursor, a cobalt precursor, a manganese precursor.

6. The preparation method of the carbon-based single-atom catalyst doped with five non-metal elements according to claim 1, characterized in that, The mass ratio of the POSFNC to the transition metal precursor is (30-50):(2-5).

7. The preparation method of the carbon-based single-atom catalyst doped with five non-metal elements according to claim 1, wherein The temperature of the first annealing treatment is 900°C - 1100°C, the time of the first annealing treatment is 1h - 3h, and the heating rate of the first annealing treatment is 2°C / min - 5°C / min; and / or, the temperature of the second annealing treatment is 900°C - 1100°C, the time of the second annealing treatment is 1h - 3h, and the heating rate of the second annealing treatment is 2°C / min - 5°C / min; and / or, the first annealing treatment and the second annealing treatment are carried out in an inert atmosphere.

8. A carbon-based single-atom catalyst doped with five non-metallic elements, characterized in that, Prepared by the preparation method of the carbon-based single-atom catalyst doped with five non-metal elements according to any one of claims 1-7.

9. The carbon-based single-atom catalyst doped with five non-metallic elements according to claim 8, wherein The carbon-based single-atom catalyst doped with five non-metal elements includes a hollow porous carbon substrate, a transition metal distributed in the form of single atoms on the surface of the hollow porous carbon substrate, and P element, O element, S element, F element, N element distributed on the surface of the hollow porous carbon substrate.

10. Application of the carbon-based single-atom catalyst doped with five non-metal elements according to any one of claims 8-9 in a zinc-air battery.

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