A supported heterogeneous nano-electrocatalytic material AB@(ABOx)-(A / B-)-L-C and preparation thereof

Abstract

A supported heterogeneous nano-electrocatalytic material AB@(ABO x )‑(A / B‑)‑L‑C and preparation, belong to the field of nano-electrocatalytic material.The present application uses mixed metal salt, alkali solution and heteroatom ligand as raw material, uses porous carrier, and prepares metal alloy@metal-heteroatom co-doped carbon heterogeneous structure electrocatalytic material with supported type with metal alloy as core and metal oxide inlaid into metal-heteroatom co-doped carbon layer as shell by ultrasonic atomization microgelation combined atmosphere high-temperature pyrolysis process, which has higher electrocatalytic performance than commercial Pt / C, and is suitable for the preparation of electrode catalyst layer for fuel cell and carbon dioxide resource utilization.

Description

Technical Field

[0001] This invention relates to a novel heterostructured nano-electrocatalytic material and its large-scale preparation method, particularly a metal alloy (AB)@metal oxide (ABO) x ) Heterogeneous nano-electrocatalytic material with embedded metal (AB) and heteroatom (L) co-doped shell (C) (AB@(ABO) x The invention relates to (A / B-)-LC and its preparation method, and belongs to the field of novel heterostructure hybrid materials technology. Background Technology

[0002] Hydrogen energy has the advantages of high power density per unit mass, no carbon emissions, abundant reserves, recyclability, and no solid or liquid waste, making it inevitable to replace fossil energy.

[0003] The core component of hydrogen-based fuel cells (FCs) is the fuel cell stack, mainly composed of electrodes, an electrolyte membrane, and bipolar plates. The bipolar plates and gas diffusion layer (GDL), ion exchange membrane, and catalyst layer constitute the main cost, accounting for approximately 70% of the cost in currently mature commercial PEMFC stacks, with the catalyst accounting for 21%. Although many low-platinum alloy and non-platinum catalysts have been developed, the catalytic performance (especially in the oxygen reduction reaction (ORR)), resistance to poisoning and persistence, safety, and cycle life still need improvement. Currently, commercially available PEMFC electrode catalysts are still based on rare and precious metals such as Pt or their alloys. While optimizing the PEM material and its interface with the active layer can improve its cost-effectiveness, the scarcity of Pt-based raw materials makes it difficult to significantly reduce the cost of electrode catalysts (currently, the average Pt content in the PEMFC anode is approximately 0.4 mg Pt / cm³). 2 The high cost and sustainable application of rare and precious metal electrode catalytic materials such as Pt have severely hampered the industrialization of fuel cells. Therefore, to address the issues of high cost and sustainable application of rare and precious metal electrode catalytic materials, it is necessary to develop high-performance non-rare and precious metal (NRNM) and low-content rare and precious metal (LRNM) high-efficiency catalysts. These are key catalytic materials for the next generation of cost-effective PEMFCs, the next generation of safer and more reliable AEMFC stacks, and the resource utilization of carbon dioxide.

[0004] This invention utilizes a mixed metal salt, alkaline solution, and heteroatom ligands as raw materials and a porous carrier to prepare a heterostructured metal-heteroatom hybrid carbon electrocatalytic material with a supported structure consisting of a metal alloy core and a metal oxide-embedded metal-heteroatom co-doped carbon layer as a shell. This material exhibits higher electrocatalytic performance than commercial Pt / C and is suitable for the preparation of electrode catalyst layers for fuel cells and carbon dioxide resource utilization. Summary of the Invention

[0005] To address the challenges of improving the activity, resistance to poisoning, durability, safety, and cycle life of existing rare and precious metal and non-rare and precious metal electrocatalytic materials for fuel cells and carbon dioxide resource utilization, while significantly reducing costs, this invention designs and prepares a novel composite and hybrid electrocatalytic material. It also proposes a large-scale preparation method using a combined ultrasonic atomization microsol-gelation-heteroatom coordination gelation process with high-temperature atmospheric pyrolysis, which allows for flexible control over its morphology, size, heterostructure, and composition.

[0006] The preparation process includes the following steps:

[0007] (1) Ultrasonic atomization microsol formation: the alkaline solution is formed into microdroplets by ultrasonic atomization and dropped into a mixed metal salt solution containing a dispersant to construct a multi-component polyhydroxy metal mixture sol. The sol is centrifuged and washed several times with distilled water for later use. The metals mentioned include at least metal A and metal B.

[0008] (2) Sol-gel phase transformation to prepare multi-metal-heteroatom complex gel: After washing the multi-metal polyhydroxy metal mixture sol, the porous carrier and the ligand containing heteroatom L are mixed and added to the solvent and mixed evenly. The heteroatom of the ligand and the hydroxyl group undergo a substitution reaction and / or a complexation reaction with the metal, so that the multi-metal polyhydroxy metal sol gels and form metal-heteroatom complex microgels loaded on the porous carrier. Then, the mixture is centrifuged into a slurry and washed clean, and then dried into powder using an organic solvent spray dryer.

[0009] (3) High-temperature pyrolysis preparation of metal alloy core-metal oxide embedded heteroatom doped shell electrocatalyst: The powder is placed on a petri dish in a quartz tube furnace and spread evenly. It is then calcined under different atmospheres to obtain metal alloy (AB)@metal oxide (ABO). x ) Heterogeneous nano-electrocatalytic material with embedded metal (A / B) and heteroatom (L) co-doped shell (C) (AB@((ABO) x )-(A / B-)-LC).

[0010] In step (1), metal A and metal B are selected from transition metals of the fourth, fifth and sixth periods, such as Sc, Ti, V, Cr, Fe, Co, Ni, Mn, Zn, Cu, Cr, Ti, Mo, Y, Ag, Nb, Au, Pt, Pd, Ir, Ru, Rh, Oe; lanthanide and actinide rare earth metals, such as La, Ce, Gd, Nd, Ho; and K, Rb, Cs of IA; Be, Mg, Ca of IIA; Ga, In of IIIA; Ge, Sn, Pb of IVA; Sb, Bi of VA; metal A and metal B are different, and metal A and metal B are a single metal or multiple metals; the ratio of metal A and metal B is not limited, such as a molar ratio of 10:1-1:10, etc., which can be adjusted as needed;

[0011] Metal salts are water-soluble metal salts such as halides, sulfates, nitrates, perhalates, and phosphates, with a concentration range of 0.01M to 1M; alkaline solutions are alkali metal (LiOH, NaOH, KOH, RuOH), alkaline earth metal (such as Be(OH)2, Ca(OH)2), sodium borohydride, or strong organic bases (such as ammonia, hydrazine hydrate, ethylenediamine) solutions, with a concentration range of 0.01M to 1M.

[0012] Step (2) The carrier is selected from porous activated carbon black, graphene oxide sheets, carbon nanotubes, modified molecular sieves (such as imidazole modified ZIF-8), porous hydroxyapatite, cerium phosphotungstate modified nanoporous silica (MCM-41@Cs-TPA), cerium phosphotungstate modified nanoporous alumina (Al2O3@Cs-TPA), cerium phosphotungstate modified nanoporous titanium dioxide (TiO2@Cs-TPA), or other modified carriers, with a concentration of 0.1 g / L to 500 g / L;

[0013] In step (2), the heteroatom L doped in the carbon shell is selected from one or more elements other than carbon and oxygen in Group IIIA, IVA, VA, and VIA elements, such as boron, Al, Ga, Sn, N, P, As, Sb, Bi, S, Se, and Te. The doping method is construction. The ligand containing the heteroatom L is selected from, for example, phenanthrene, purines, pyrimidines, polyamino acids, triphenylphosphine, selenomethionine, triphenylarsine, and polyborane salts (such as spherical cesium dodecoborobromate Cs2 (B 12 Br 12 ), Cerium dodecoboroiodate Ce (B 12 Br 12 2. Lithium dodecyl borohydride (Li2) (B 12 H 12 One or more of the following: alkoxybismuth, alkoxyselenium, alkoxysulfur, etc.

[0014] The molar ratio of the ligand containing the heteroatom L to the metal is not limited, such as 1:10-10:1; the concentration of the ligand containing the heteroatom L is from 0.1 g / L to 200 g / L.

[0015] The solvent is a solvent capable of dissolving metal hydroxide sols and heteroatom ligands, such as ethanol, diethyl ether, acetone, benzene, etc.

[0016] In step (2), when the multi-component polyhydroxy metal mixture sol, porous carrier, and ligand containing heteroatoms L are mixed and reacted, a Y-type microchannel mixer is used.

[0017] The different atmospheres in step (3) are an inert atmosphere and / or a precursor atmosphere for the heteroatom element to be further doped. The precursor atmosphere for the heteroatom element to be doped is selected from ammonia, imidazole, phosphine, borane, sulfur vapor, sulfur dioxide vapor, selenium dioxide vapor, etc., with a content of 5-20V. If the atmosphere is for a solid substance at room temperature, the solid substance (such as sulfur, selenium dioxide, alkoxybismuth) is placed in a tube furnace and heated before being loaded onto a porous support for the metal-heteroatom complex microgel. The heating temperature is controlled above or below its boiling point or sublimation point, and the evaporation rate is controlled by the temperature. The solid substance enters the reaction system through an inert carrier gas. The overall flow rate of the atmosphere gas is 5-40 sccm. The heteroatoms in step (3) can be the same as or different from those in step (2). If they are the same, the overall doping amount can be further increased; if they are different, new doping elements can be introduced.

[0018] If the atmosphere is obtained by evaporating solid heteroatom compounds, place them in a quartz petri dish in the front temperature control zone of the heating furnace, then open the inert gas valve and control the gas flow rate at 10-40 sccm as needed. Gradually increase the furnace temperature to the required pyrolysis temperature. Generally, the calcination temperature is controlled between 400℃ and 1400℃. After holding at this temperature for 0.5-4 hours, cool down and discharge the material.

[0019] The material structure obtained by this invention is as follows: a metal alloy AB is the core, a metal oxide ABOx is the embedded metal and a metal-heteroatom co-doped layer L is the shell C, forming a heterostructure; the above heterostructure is loaded on a porous support to form a nano-electrocatalytic material. The above-mentioned supported heterostructure metal-heteroatom hybrid (carbon) electrocatalytic material with a metal alloy as the core and a metal oxide embedded metal-heteroatom co-doped layer as the shell has obtained a novel carbon-based heterostructure nano-electrocatalytic material with a metal alloy as the core and a metal oxide embedded metal and heteroatom co-doped layer (AB@(ABOx)-(A / B-)-LC).

[0020] The material obtained in this invention is used as an electrocatalytic material for electrocatalytic redox reactions.

[0021] The ultrasonic atomizing microsol-gel device used in the first step of this invention has the capability to prepare polyhydroxy metallosols on a large scale, with a small laboratory device capable of producing 50-100g per batch. The heteroatom coordination gelation process in the second step has flexible and diverse control capabilities, allowing for the replacement of solvents, porous supports, and heteroatom ligands as needed, providing a variety of precursors for subsequent high-temperature pyrolysis. Furthermore, the atmosphere-controlled high-temperature pyrolysis process has the capability to regulate the atmosphere, enabling the heteroatomization of electrocatalysts and their pre-supports, thereby increasing the overall catalytic site density. Attached Figure Description

[0022] Figure 1 The diagram shows the ultrasonic atomization microsol-gel process controlled by a micro-particle pump used in step 1 of the preparation process of this invention, the microfluidic heteroatom coordination gelation process used in step 2, and the high-temperature atmosphere pyrolysis process used in step 3, as well as the schematic diagram of their principles and device structure.

[0023] Figure 2 To characterize the morphology of the Co3Fe7@(CoFe2O4)-(Co / Fe-)-NC heterostructure nanocatalytic material prepared in Example 1: (1) High-angle annular dark-field STEM (HAADF-STEM) image; (2) HAADF-STEM image of a single particle (nm: nanometer, i.e., 10 nm). -9 rice).

[0024] Figure 3 The electron energy loss spectra of a single Co3Fe7@(CoFe2O4)-(Co / Fe-)-NC heterostructure nanocatalytic material are as follows: (a) Overall morphology; (b) Elemental distribution obtained in the green box; (c) Fe; (d) Co; (e) C; (f) N; (g) O; (h) C+N overlay; (i) Fe+N

[0025] Figure 4 For the morphology and structural characterization of the local core-shell interface of a single Co3Fe7@((CoFe2O4)-(Co / Fe-)-NC) heterostructure nanocatalyst: (a) TEM image of a single particle; (b) HR-TEM image of the corresponding region (top) and fast Fourier transform diagrams of the CoFe2O4 (311) crystal plane (bottom left) and the Co3Fe7 (110) crystal plane (bottom right).

[0026] Figure 5 This is a comparison of linear sweep voltammetry (LSV) curves of the heterostructured nanocatalytic material Co3Fe7@((CoFe2O4)-(Co / Fe-)-NC) in 0.1M-KOH medium and the catalytic performance of commercial Pt / C electrocatalyst for oxygen reduction reaction (ORR).

[0027] Figure 6 This is a Tafel slope comparison of the catalytic performance of the Co3Fe7@((CoFe2O4)-(Co / Fe-)-NC) heterostructure nanocatalyst in 0.1M-KOH medium and the commercial Pt / C electrocatalytic oxygen reduction reaction (ORR).

[0028] Figure 7 This is a Nyquist plot of the electrochemical impedance spectroscopy (EIS) of the Co3Fe7@((CoFe2O4)-(Co / Fe-)-NC) heterostructure nanocatalyst in 0.1M-KOH medium and in the commercial Pt / C electrocatalytic oxygen reduction reaction (ORR).

[0029] Figure 8 This is a comparison of the chronocurrent response curves of the Co3Fe7@((CoFe2O4)-(Co / Fe-)-NC) heterostructure nanocatalytic material at 0.6 V in 0.1 M-KOH medium and the catalytic performance of commercial Pt / C electrocatalytic oxygen reduction reaction (ORR).

[0030] Figure 9 Co prepared at different Co:Fe molar ratios x Fe y @((Co z Fe (3-z) TEM images characterizing the microstructure of O4-(Co / Fe-)-NC type catalysts (x: 0.001-1; y: 1-0.001; z: 0.001-3). (a), (b) TEM and high-resolution TEM images of nanoparticles with Co / Fe = 0.001 / 1; (c), (d) TEM and high-resolution TEM images of F2Cl nanoparticles with Co / Fe = 1 / 2; (e), (f) TEM and high-resolution TEM images of nanoparticles with Co / Fe = 2 / 1; (g), (h) TEM and high-resolution TEM images of nanoparticles with Co / Fe = 1 / 0.001.

[0031] Figure 10 Co prepared at different Co / Fe ratios using a rotating disk electrode (RDE) in 0.1 M KOH electrolyte. x Fe y @((Co z Fe (3-z) Linear sweep voltammetry (LSV) curves of ORR electrocatalytic performance of O4)-(Co / Fe-)-NC) nano-electrocatalytic materials and commercial Pt / C.

[0032] Figure 11 Co prepared from mixed metal salt raw materials with different Co / Fe ratios x Fe y@((Co z Fe (3-z) Comparison of Tafel curve slopes between O4)-(Co / Fe-)-NC) nano-electrocatalyst materials and commercial Pt / C.

[0033] Figure 12 Co prepared from mixed metal salt raw materials with different Co / Fe ratios x Fe y @((Co z Fe (3-z) Nyquist plots of electrochemical impedance spectroscopy (EIS) of O4)-(Co / Fe-)-NC) nano-electrocatalytic materials and commercial Pt / C.

[0034] Figure 13 Co prepared from mixed metal salt raw materials with different Co / Fe ratios x Fe y @((Co z Fe (3-z) Chronocurrent response curves of O4)-(Co / Fe-)-NC) nano-electrocatalytic materials and commercial Pt / C for electrocatalytic oxygen reduction reaction (ORR) catalytic performance testing at 0.6 V in 0.1 M-KOH medium.

[0035] Table 1 shows the atomic percentages of each element in heterostructure catalysts prepared with different Co / Fe ratios based on XPS measurements.

[0036] Table 2 shows the proportions of different types of nitrogen in heterostructure catalysts prepared under different Co / Fe ratios, obtained by fitting the N 1s peak. Detailed Implementation

[0037] The present invention will be further described below with reference to the embodiments, but the present invention is not limited to the following embodiments.

[0038] Example 1

[0039] (1) Implementation Step 1

[0040] Preparation of alkaline solution in step 1: Take 0.56g KOH into a PTFE beaker, add 25 mL of deionized water, and oscillate in an ultrasonic oscillator for 2 min to fully dissolve it.

[0041] Preparation of the mixed metal salt solution in step 1: Take 0.5 g FeCl2•4H2O (2.5 mmol) and 0.6 g CoCl2•6H2O (2.5 mmol) in a beaker, add 0.75 g polyvinylpyrrolidone (PVP), add 50 mL ethanol and 50 mL deionized water to the glass beaker, and sonicate for 2 min to dissolve it completely.

[0042] exist Figure 1 In the process, feed pump 1 delivers an alkaline solution at a flow rate of 1 mL / min to an ultrasonic nebulizer, where it is atomized into microdroplets of 4-5 micrometers in size. This atomized droplet is then sputtered into a mixed metal salt solution delivered by feed pump 2 at a flow rate of 2 mL / min. Through a precipitation reaction, polyhydroxy iron and polyhydroxy cobalt microsols are formed, which are then transferred together into a multi-metal polyhydroxy compound microsol forming tank for later use. (The diameter of the pumping pipe is 0.5 mm-5 mm). At this point, the microsols can be centrifuged and washed with ethanol 2-3 times before being dissolved in 125 mL of an ethanol-water (1:1) mixture for 5-30 minutes.

[0043] (2) Implementation Step 2

[0044] In step 2, the preparation of the heteroatom-doped / modified porous support (diameter approximately 10-200 nm) + heteroatom ligand suspension is as follows: 0.2 g of o-phenanthroline and 1.0 g of nitrogen-modified porous carbon black are dissolved in a mixed solvent consisting of 15 ml of deionized water and 110 mL of ethanol, and stirred for 30 min to ensure complete dissolution for later use.

[0045] Pumps 3 and 4 were used to pump the multi-metal polyhydroxy compound microsol solution and the heteroatom-doped / modified porous support + heteroatom ligand suspension to a Y-type microchannel mixer (pipe diameter 0.5mm-5mm) for homogeneous mixing. During this process, the heteroatom ligands loaded on the porous support undergo ligand exchange reactions with the hydroxyl groups in the multi-metal polyhydroxy compound, resulting in gelation and the formation of multi-metal-heteroatom complex microgels on the porous support. These microgels then enter a collector for multi-metal-heteroatom complex microgels supported on a heteroatom-modified porous support. After centrifugation and washing, the microgels are dissolved in 50mL of an aqueous solution containing 30% ethanol and dried into powder using an organic solvent spray dryer, yielding the catalyst precursor powder: multi-metal-heteroatom complex microgel powder supported on a heteroatom-modified porous support.

[0046] (3) Implementation Step 3

[0047] In step 3, the preparation of the heteroatom compound atmosphere for high-temperature pyrolysis involves saturating an inert carrier gas (nitrogen in this case) with 35% concentrated ammonia water to create a pyrolysis atmosphere containing ammonia. If the desired heteroatom compound for the atmosphere is a solid at room temperature (e.g., iodine, sulfur, SeO2, (NH4)2CO3, CO(NH2)2, triphenylphosphine (TPP)), it is placed in a container with a vent at heating section I in step 3, and the heating temperature in this section is controlled to exceed the boiling point or sublimation point of the compound. This step is not used in this embodiment.

[0048] The heteroatom-modified porous support-loaded multi-metal-heteroatom complex microgel powder prepared in step 2 was placed on a petri dish on the porous stage of heating section III of the high-temperature furnace in step 3, and evenly dispersed. Under a carrier gas atmosphere of 20 sccm (standard cubic centimeters / min, standard mL / min), the furnace temperature was raised to 800℃ and held for 2 hours for high-temperature annealing under a heteroatom compound atmosphere. Then, the temperature was lowered to room temperature under an inert carrier gas atmosphere. After the prepared catalyst powder was taken out, it was washed 2-3 times with ethanol solvent and centrifuge. Then, it was dried, annealed and activated in the furnace at 800℃ under a nitrogen atmosphere to obtain the desired heterostructure nano-electrocatalytic material with a cobalt-iron alloy core and cobalt oxidase intercalated with cobalt / iron and nitrogen atoms co-doped carbon shell: Co3Fe7@((CoFe2O4)-(Co / Fe-)-NC) nano-electrocatalytic material.

[0049] (4) Microstructure and composition characterization of Co3Fe7@((CoFe2O4)-(Co / Fe-)-NC) nanoelectrocatalytic materials.

[0050] Figure 2 These are high-angle annular dark-field scanning transmission electron microscope (HAADF-STEM) images of the prepared Co3Fe7@(CoFe2O4)-(Co / Fe-)-NC nanoelectrocatalyst materials. The particles supported on the carbon support exhibit a distinct core-shell structure. Statistical analysis shows that the particle size ranges from 50 to 400 nm, with an average diameter of approximately 190 nm. The shell thickness is 10-20 nm, with an average thickness of 18 nm. HAADF-STEM images of individual particles show that the core is brighter than the outer shell (this is a dark-field image), indicating that the core is constructed from heavier atoms than the shell (e.g., the core is CoFe, and the shell is a carbon-based material). Figure 3This is a characterization result of the elemental distribution of the core and shell of another typical single particle. It can be seen that its core is mainly composed of a CoFe alloy, with Co concentrated primarily in the core and present in less quantity than iron in the shell. Iron, besides being present in the core, is also abundant in the shell, with a higher content than cobalt. Based on the binary phase diagram of the cobalt-iron alloy, X-ray diffraction (XRD) pattern, and quantitative elemental analysis, it is indicated that its core is a Co3Fe7 alloy. Analysis of carbon, nitrogen, and oxygen elements shows that carbon and nitrogen are mainly distributed in the shell, indicating that the shell is nitrogen-doped modified carbon; oxygen is concentrated in the shell, but also present at the interface, indicating the presence of cobalt ferrite at the core-shell interface. Analysis of non-metallic elements and... Figure 4 High-resolution electron microscopy images of the core-shell interface and analysis of the crystal structure of individual particles have been consistently performed. Figure 4 The high-resolution electron microscope (HEM) image and Fourier transform crystal structure of the interface in the right-hand image confirm that the core is a Co3Fe7 alloy, with CoFe2O4 grains growing within the interface, and the shell is an amorphous carbon layer with many partially crystalline (graphitized) layers. Based on the relatively uniform distribution of iron and cobalt in the shell, it can be concluded that cobalt, in addition to forming cobalt oxide, co-doped and modified carbon in the shell along with nitrogen, or formed iron carbide or cobalt carbide. XRD analysis showed no obvious Fe3C or Co3C peaks. Raman spectroscopy characterization revealed a high degree of graphitization, indicating that most of it was co-doped into the graphitized carbon structure of the shell along with nitrogen, constructing numerous metal atom-nitrogen-carbon (graphitized) single-atom or multi-atom active sites. Furthermore, the nitrogen ligand characteristics in the metal atom-nitrogen-carbon active sites were characterized, mainly based on the proportion of different nitrogen types obtained by fitting the N 1s peak from XPS characterization. The results showed that the proportions of nitrogen ligands were as follows: pyridine nitrogen accounted for 14%; pyrrole nitrogen accounted for 43.0%; graphitic nitrogen accounted for 42.3%; and nitrogen-oxygen nitrogen accounted for 1.7%.

[0051] (5) Characterization of the electrocatalytic performance of Co3Fe7@((CoFe2O4)-(Co / Fe-)-NC) nano-electrocatalytic material for ORR

[0052] Figure 5 This study compares the ORR electrocatalytic performance of Co3Fe7@((CoFe2O4)-(Co / Fe-)-NC) nanocatalysts and commercial Pt / C using a rotating disk electrode (RDE) in 0.1 M KOH electrolyte using linear sweep voltammetry (LSV). The results show that Co3Fe7@((CoFe2O4)-(Co / Fe-)-NC) nanocatalysts and commercial Pt / C exhibit a larger positive potential and a higher current density than commercial Pt / C. Its onset potential and half-wave potential reach 1.05 V and 0.89 V (electrocatalytic activity indicators), respectively, while the corresponding values ​​for Pt / C are 0.95 V and 0.84 V. The calculated current density reaches 27 mA / cm². 2 The corresponding Pt / C ratio is only 5 mA / cm². 2 . Figure 6 The image shows a comparison of the Tafel slope of the electrocatalytic ORR performance of this catalyst and Pt / C. The results indicate that the Tafel slope of this catalyst (69 mV / dec) is lower than that of the commercial Pt / C catalyst (76 mV / dec), suggesting that it exhibits higher activity than the commercial Pt / C catalyst in the rate-limiting step. Figure 7 The Nyquist plot of electrochemical impedance spectroscopy (EIS) for neutralized Pt / C shows that the semi-circular diameter of the Co3Fe7@((CoFe2O4)-(Co / Fe-)-NC) nanocatalyst is much smaller than that of the Pt / C catalyst. This indicates that the Co3Fe7@(CoFe2O4)-(Co / Fe-)-NC) nanocatalyst has a lower charge transfer resistance, which is more favorable for electron transfer in the reaction. Stability is directly related to the catalyst lifetime, such as... Figure 8As shown, the chronocurrent response tested at 0.6 V indicates that after 36,000 seconds, the limiting current density of the Co3Fe7@((CoFe2O4)-(Co / Fe-)-NC) catalyst remains at 87.0% of its initial value, significantly higher than the 55.5% of the commercial Pt / C catalyst. This demonstrates that the Co3Fe7@((CoFe2O4)-(Co / Fe-)-NC) electrocatalyst exhibits excellent catalytic activity durability in alkaline media. Characterization of its microstructure, constituent crystal structure, and elemental electronic structure reveals that the superior ORR performance compared to commercial Pt / C is primarily due to the highly conductive CoFe alloy core and the metal and nitrogen-modified highly graphitized carbon-based shell obtained through high-temperature atmospheric pyrolysis. This shell possesses higher conductivity and more single- and multi-atom active centers constructed from metal-nitrogen-carbon compared to carbon-supported Pt nanocatalysts. Furthermore, the cobalt oxygen at the interface or within the carbon layer exhibits higher catalytic activity in synergy with the metal alloy core. Based on generally accepted theoretical research, the single-to-multi-atom active centers constructed from metal-nitrogen-carbon are related to the nitrogen coordination form. Pyridine nitrogen and model nitrogen are both sp2 hybridized, contributing one p electron to the π system, while pyrrole nitrogen is sp3 hybridized, contributing two p electrons to the π system. Therefore, pyridine nitrogen and graphitic nitrogen have greater electronegativity than pyrrole nitrogen (the slightly lower electronegativity of pyrrole nitrogen is beneficial for the adsorption and stabilization of oxygen and transition products *OH). The activity order is: pyrrole nitrogen > pyridine nitrogen > graphitic nitrogen > nitrogen-oxygen nitrogen. Simultaneously, studies have shown that if the carbon in graphitic nitrogen has covalently bonded to oxygen (CO carbon), it exhibits high catalytic activity. Our compositional characterization also indicates that our catalyst has a large amount of oxidized carbon, which determines the presence of a large amount of active graphitic nitrogen, further increasing the active center site density of our catalyst. The catalyst shell we prepared has a very high pyrrole nitrogen content and a very low oxidized nitrogen content. Therefore, the multi-level components of the metal alloy core, the cobalt oxygen intercalated at the interface or within the carbon layer, and the metal-nitrogen-carbon single- to multi-atom active centers in this heterostructure exhibit a high synergistic effect. Furthermore, through our invented high-temperature thermal decomposition method, the shell layer is constructed with a very high content of pyrrole-type nitrogen metal-NC active sites and graphite-type nitrogen catalytic active sites with OC structures. In addition, the addition of the second element Co through alloying results in a high binding force with nitrogen, reducing the Bader charge on Fe and lowering the OH* binding energy, thereby promoting reaction kinetics. These characteristics collectively improve the ORR catalytic activity and durability (lifetime) of this type of heterostructure electrocatalyst.

[0053] Example 2

[0054] (1) Implementation Step 1

[0055] In step 1 of Example 1, we changed the molar ratio of Co:Fe to 0.001:1, 2:1, 1:2 and 1:0.001 to prepare metal salt solutions respectively.

[0056] (2) Implementation Step 2

[0057] Same as Example 1

[0058] (3) Implementation Step 3

[0059] Same as in Example 1. Finally, Co was obtained. x Fe y @((Co z Fe (3-z) O4)-(Co / Fe-)-NC type catalyst, x: 0.001-1; y: 1-0.001; z: 0.001-3

[0060] (4) Co x Fe y @((Co z Fe (3-z) Microstructure and composition characterization of O4)-(Co / Fe-)-NC) nano-electrocatalytic materials

[0061] Figure 9 Co prepared at different Co:Fe molar ratios x Fe y @((Co z Fe (3-z)TEM images characterizing the microstructure of the O4-(Co / Fe-)-NC type catalyst (x: 0.001-1; y: 1-0.001; z: 0.001-3) show that regardless of the Co / Fe ratio, they can form a core-shell heterostructure similar to Co / Fe=1 / 1 nanomaterials. However, when the cobalt or iron content is relatively low, the shell thickness of the formed core-shell structure is relatively thin, and the oxide content of the shell is significantly higher. Therefore, the microstructure and composition of the shell can be controlled by the content of the mixed metal salts in the reaction solution. Furthermore, X-ray photoelectron spectroscopy (XPS) was used to analyze its composition (surface 8 nm), elemental valence states, and coordination states. Table 1 presents the analytical results, including the elemental content. The Co / Fe ratio in Example 1 (1 / 1) is also included for comparison. As the cobalt salt content of the raw material increases, the cobalt content in the shell of the constructed nanomaterial (containing cobalt oxidase and metal-NC single-atom sites) also increases. In catalysts with Co / Fe ratios of 1 / 2 and 1 / 1, the Co / Fe ratio remains essentially the same as the raw material. However, when the Co content exceeds that of iron, the cobalt content in the catalyst shell is still much lower than the iron content, indicating that iron is more easily enriched in the shell during preparation to construct cobalt oxidase (CoFe2O4) and more iron-based metal-NC single-atom sites. Based on the N coordination type, the peak positions of the N element characterized by XPS were fitted, and the contents of pyridine nitrogen, pyrrole nitrogen, graphitic nitrogen, and NO were analyzed with respect to the Co / Fe ratio, as shown in Table 2. It is evident that with the addition of cobalt, the pyridine nitrogen content in the prepared catalyst decreases while the pyrrole nitrogen and graphitic nitrogen contents increase. Pyrrole nitrogen reaches its highest level (43.3%) when Co / Fe = 1 / 2, while the nitrogen oxide content reaches its lowest level (1.7%) when Co / Fe = 1 / 1, with the remaining contents increasing with the addition of cobalt. Based on the nitrogen coordination type, it can be predicted that the overall catalytic performance should be relatively excellent at Co / Fe ratios of 1 / 2 and 1 / 1.

[0062] (5) Characterization of the electrocatalytic performance of Co3Fe7@(CoFe2O4)-(Co / Fe-)-NC nano-electrocatalytic material for ORR

[0063] Figure 10 This refers to the use of a rotating disk electrode (RDE) in 0.1 M KOH electrolyte to study the effects of Co. x Fe y @((Co z Fe (3-z) A comparison of the linear sweep voltammetry (LSV) curves of the O4)-(Co / Fe-)-NC) nano-electrocatalytic material and commercial Pt / C on the ORR electrocatalytic performance showed that it had a larger positive potential and a larger current density than commercial Pt / C, with the best value at Co / Fe=1 / 2, but smaller than Co / Fe=1 / 1. Figure 11The Tafel slopes are for different Co / Fe catalysts. It can be seen that the slope is smallest when the iron or cobalt content is almost 100%, which is smaller than that of Pt / C, indicating that it exhibits higher activity than commercial Pt / C catalysts in the rate-limiting step. Among them, the near 100% cobalt catalyst has the smallest slope at 61 mV / dec, indicating that the pure cobalt catalyst has the highest catalytic activity in the rate-limiting step. Figure 12 This is a comparison of Nyquist curves of electrochemical impedance spectroscopy (EIS) for catalysts prepared with different Co / Fe ratios and Pt / C ratios, in conjunction with the data from Example 1. Figure 6 The results show that the semi-circular diameter of the nano-electrocatalyst material prepared from raw materials with a cobalt content of nearly 100% is smaller than that of the Co / Fe=1 / 1 catalyst, which is smaller than that of the Pt / C catalyst. This indicates that when the cobalt content is nearly 100%, the charge transfer resistance of the nano-electrocatalyst material is lower, which is more conducive to the transfer of electrons in the reaction. Figure 13 The chronocurrent response of catalysts with different Co / Fe ratios was tested at 0.6 V. All catalysts exhibited higher activity ratios than Pt / C at 36,000 seconds, with Co / Fe=1 / 2 and almost pure cobalt reaching 82.5% and 81.5% respectively, though significantly lower than the 87% of Co / Fe=1 / 1. Considering all electrocatalytic performance factors, the electrocatalyst prepared at Co / Fe=1 / 1 showed the best ORR catalytic effect.

[0064] Example 3

[0065] (1) Implementation Step 1

[0066] In step 1, the iron salt in the mixed metal salt solution was replaced with other metal salts (collectively referred to as M1). The molar content of M1 salt was the same as that of cobalt salt, i.e., Co / M1 = 1 / 1. Mixed metal salt solutions were prepared separately, and then the electrocatalyst was prepared according to the same process parameters as in steps 1-3 of Example 1. M1 can be transition metals of the fourth, fifth, and sixth periods, such as Sc, Ti, V, Cr, Ni, Mn, Zn, Cu, Cr, Ti, Mo, Y, Ag, Nb, Au, Pt, Pd, Ir, Ru, Rh, Oe; lanthanides and actinides rare earth metals, such as La, Ce, Gd, Nd, Ho; and K, Rb, Cs of period IA; Be, Mg, Ca of period IIA; Ga, In of period IIIA; Ge, Sn, Pb of period IVA; and Sb, Bi of period VA. Meanwhile, we used the density inverse generalization function (DFT) combined with group expansion (CE) method (DFT-CE) to calculate the composition, crystal phase, surface and subsurface atomic arrangement, element valence state and electronic structure, and electron transfer energy under different element valence states of this type of multi-level structure catalyst. At the same time, we calculated the adsorption and desorption energies of each level of microstructure with reactants (such as oxygen and hydrogen), intermediate products (such as *OH) and final products (such as water), as well as the electron transfer energies of CO and CO2 under different element valence states based on molecular dynamics. Based on the thermodynamics and kinetics of catalytic reaction, we screened M1 and selected the best one. The results are basically consistent with the experimental test results in (5) below.

[0067] (2) Implementation Step 2

[0068] Same as Example 1

[0069] (3) Implementation Step 3

[0070] Same as in Example 1. Finally, Co was obtained. x M1 y @((Co z M1 (2Q / n-2z / n) O Q The catalyst is of the type (Co / M1-)-NC), where n is the valence state of metal M1 in this catalyst, Q is the number of oxygen atoms in the M1 oxygen body formed, and z is a number from 0 to Q.

[0071] (4) Co x M1 y @((Co z M1 (2Q / n-2z / n) O Q Microstructure and composition characterization of )-(Co / M1-)-NC type nano-electrocatalytic materials

[0072] The characterization methods used in Example 1 for microstructure and composition show that Co and M1 can construct nanocatalysts with the same structure, ranging in size from 0.5 nm to 500 nm. These nanocatalysts are composed of an alloy core, a mixed oxide of M1 and cobalt, an M1 / Co shell, and a nitrogen-doped carbon shell. M1 and cobalt together with N form the M1 / Co-NC active center.

[0073] (5) Co x M1 y @((Co z M1 (2Q / n-2z / n) O Q Electrocatalytic performance characterization of ORR catalyzed by )-(Co / M1-)-NC type nano-electrocatalytic materials

[0074] For the prepared Co x M1 y @((Co z M1 (2Q / n-2z / n) O Q The performance characterization results of the (Co / M1-)-NC) type nano-electrocatalyst material for ORR catalysis show that the catalytic performance is best when M1 is a metal with multiple valence states or unfilled f orbitals, such as Mn, Sn, Mo, Cr, Cu, V, W, Ce, Gd, or Hg. Among them, when M1 is Mn, Cu, W, Ce, or Hg, the half-wave potential can reach 0.9-1.4V, the onset voltage can reach 1.1-1.6V, the Tafel slope can be as small as 0.60mV / dec to 0.5mV / dec, and the chronocurrent response tested at 0.6V still remains at 93%-96% after 36000 seconds.

[0075] Example 4

[0076] (1) Implementation Step 1

[0077] In step 1, a third metal salt (collectively referred to as M1) is mixed with the cobalt and iron salts at the same molar concentration as iron and cobalt, i.e., Co / Fe / M1 = 1 / 1 / 1, to construct a three-unit mixed metal salt. Then, an electrocatalyst is prepared using the same process parameters as in steps 1-3 of Example 1. M1 can be a transition metal from the fourth, fifth, and sixth periods, such as Sc, Ti, V, Cr, Ni, Mn, Zn, Cu, Cr, Ti, Mo, Y, Ag, Nb, Au, Pt, Pd, Ir, Ru, Rh, Oe; lanthanides and actinides rare earth metals, such as La, Ce, Gd, Nd, Ho; and K, Rb, Cs of period IA; Be, Mg, Ca of period IIA; Ga, In of period IIIA; Ge, Sn, Pb of period IVA; and Sb, Bi of period VA.

[0078] (2) Implementation Step 2

[0079] Same as Example 1

[0080] (3) Implementation Step 3

[0081] Same as in Example 1. Finally, (FeCo) was obtained. x M1 y @(((FeCo) z M1 (2Q / n-2z / n) O Q The catalyst is of the type )-((Fe / Co / M1-)-NC), where n is the valence state of metal M1 in this catalyst, Q is the number of oxygen atoms in the M1 oxygen body formed, and z is a number from 0 to Q.

[0082] (4) (FeCo) x M1 y @(((FeCo) z M1 (2Q / n-2z / n) O Q Microstructure and composition characterization of )-((Fe / Co / M1-)-NC) type nano-electrocatalytic materials

[0083] The characterization methods used in Example 1 for microstructure and composition show that Co and M1 can construct nanocatalysts with the same structure, ranging in size from 0.5 nm to 500 nm. These nanocatalysts are composed of an alloy core, a mixed oxide of M1 and cobalt, an M1 / Co shell, and a nitrogen-doped carbon shell. M1 and cobalt together with N form the M1 / Co-NC active center.

[0084] (5) (FeCo) x M1 y @(((FeCo) z M1 (2Q / n-2z / n) O Q Electrocatalytic performance characterization of ORR catalyzed by )-((Fe / Co / M1-)-NC) type nano-electrocatalytic materials

[0085] For the prepared (FeCo) x M1 y @(((FeCo) z M1 (2Q / n-2z / n) O QThe performance characterization results of the ORR catalysis of the ternary metal alloy nano-electrocatalyst material of type )-((Fe / Co / M1-)-NC) showed that the catalytic performance was best when M1 = Mn, Cr, Cu, V, Hg, Ce, Gd metals with multiple valence states but with 1-2 electron transfers between valence states or unfilled f orbitals. Among them, when M1 = Mn, Cu, Ce, Hg, its half-wave potential can reach 0.95-1.6V, the onset voltage can reach 1.1-1.8V, the Tafel slope can be as small as 0.50mV / dec to 0.3mV / dec, and the chronocurrent response tested at 0.6V voltage can still maintain 94%-97% after 36000 seconds.

[0086] Example 5

[0087] (1) Implementation Step 1

[0088] In step 1, the nitrogen ligand in the heteroatom ligand is replaced with ligands containing other heteroatoms to construct a catalyst precursor consisting of mixed metal heteroatom ligands (Co-L, Fe-L, and M1-L) composed of Co, Fe, and M1. Then, the electrocatalyst is prepared using the same process parameters as in steps 1-3 of Example 1. The heteroatom ligands can be of the following types: organic complexes or polar compounds of one element other than carbon, oxygen, and nitrogen from Group IIIA, IVA, VA, and VIA main elements, such as boron, Al, Ga, Sn, N, P, As, Sb, Bi, S, Se, and Te. Typical examples include: triphenylphosphine (containing phosphorus); ethoxyarsenic (containing arsenic); cystine and cysteine ​​(containing sulfur and nitrogen); selenomethionine (containing selenium); bismuth (bismuth isooctanoate, bismuth laurate, bismuth neodecanoate, and bismuth naphthenate); 1-iodo-3-methylpentane (containing iodine); and 2-bromo-4-nitrobenzyl alcohol (containing bromine), etc. We used the density inverse functional theory (DFT) method to calculate the composition, crystal phase, surface and subsurface atomic arrangement, elemental valence states and electronic structures, and electron transfer energies under different elemental valence states of the multi-level structure catalyst. In particular, we calculated the electronic structure and orbital hybridization energies of the metal (M) and MLCs constructed with different heteroatom ligands and carbon. At the same time, we calculated the adsorption and desorption energies of each level of microstructure with reactants (such as oxygen and hydrogen), intermediate products (such as *OH) and final products (such as water), as well as the electron transfer energies under different elemental valence states. In particular, we calculated the adsorption and desorption energies of the active center metal in MLC with reactants (such as oxygen and hydrogen), intermediate products (such as *OH) and final products (such as water), as well as the adsorption and desorption energies of CO and CO2. Based on the thermodynamics and kinetics of catalytic reaction, we screened L, selected the best and verified it experimentally. The results are basically consistent with the experimental test results in (5) below.

[0089] (2) Implementation Step 2

[0090] Same as Example 1

[0091] (3) Implementation Step 3

[0092] Same as in Example 1. Finally, (FeCo) was obtained. x M1 y @(((FeCo) z M1 (2Q / n-2z / n) O Q The catalyst is of the type )-((Fe / Co / M1-)-LC), where n is the valence state of metal M1 in this catalyst, Q is the number of oxygen atoms in the M1 oxygen body formed, z is a number from 0 to Q, and L = B, Al, P, As, Bi, Sb, S, Se, Te, Br, I.

[0093] (4) (FeCo) x M1 y @(((FeCo) z M1 (2Q / n-2z / n) O Q Microstructure and composition characterization of )-((Fe / Co / M1-)-LC) type nano-electrocatalytic materials

[0094] The characterization methods used in Example 1 for microstructure and composition show that mixed metal salts and different heteroatom ligands can construct nanocatalysts with the same structure, ranging in size from 0.5 nm to 500 nm. These nanocatalysts are composed of an alloy core, a mixed oxide of M1 and cobalt and iron, and a co-doped carbon shell of M1 / Co / Fe and heteroatom L. M1, cobalt and iron together with L form the M1 / Co / Fe-LC active center.

[0095] (5) (FeCo) x M1 y @(((FeCo) z M1 (2Q / n-2z / n) O Q Electrocatalytic performance characterization of ORR catalyzed by )-((Fe / Co / M1-)-LC) type nano-electrocatalytic materials

[0096] For the prepared (FeCo) x M1 y @(((FeCo) z M1 (2Q / n-2z / n) O QThe performance characterization results of the ternary metal alloy nano-electrocatalyst material of type )-((Fe / Co / M1-)-LC) showed that when L=P, Bi, As, Te, Se, I, the catalytic activity was best when it had heteroatoms with multiple coordination and multiple valence states (e.g., phosphorus with +3 and +5 valences, coordination number up to 5; Te with +4 and +6 valences, coordination number up to 8). However, for higher periods (e.g., sixth-period elements), the catalytic persistence and stability were not very high. Among them, when L=Se, Te, P, As, I, the half-wave potential can reach 1.0-1.8V, the onset voltage can reach 1.2-1.9V, the Tafel slope can be as small as 0.40mV / dec to 0.25mV / dec, and the chronocurrent response tested at 0.6V can still maintain 92%-99% at 36000 seconds.

[0097] Example 6

[0098] (1) Implementation Step 1

[0099] In step 1, heteroatom ligands (L) other than nitrogen ligands are used to construct binary heteroatom ligands where N and L coexist, thus constructing mixed metal heteroatom ligands (Co-L, Fe-L, and M1-L; Co-N, Fe-N, and M1-N; and Co-NL, Fe-NL, and M1-NL) compound catalyst precursors. Then, the electrocatalyst is prepared according to the same process parameters as in steps 1-3 of Example 1. The heteroatom ligands can be of the following types: organic complexes or inorganic compounds of one element other than carbon, oxygen, and nitrogen from Group IIIA, IVA, VA, and VIA main elements, such as boron, Al, Ga, Sn, N, P, As, Sb, Bi, S, Se, and Te. Typical examples include: triphenylphosphine containing phosphorus; ethoxyarsenic containing arsenic; cystine and cysteine ​​containing sulfur and nitrogen; selenomethionine containing selenium; bismuth containing bismuth isooctanoate, bismuth laurate, bismuth neodecanoate, and bismuth naphthenate; 1-iodo-3-methylpentane containing iodine; and 2-bromo-4-nitrobenzyl alcohol containing bromine. We used the density inverse functional theory (DFT) method to calculate the composition, crystal phase, surface and subsurface atomic arrangement, elemental valence states and electronic structures, and electron transfer energies under different elemental valence states of the multi-level structure catalysts. In particular, we calculated the electronic structure and orbital hybridization energies of MLCs and MNLCs constructed with metal (M) and different heteroatom ligands and carbon. At the same time, we calculated the adsorption and desorption energies of each level of microstructure with reactants (such as oxygen and hydrogen), intermediate products (such as *OH) and final products (such as water), as well as the electron transfer energies under different elemental valence states. In particular, we calculated the adsorption and desorption energies of the active center metal in MLC with reactants (such as oxygen and hydrogen), intermediate products (such as *OH) and final products (such as water), as well as the adsorption and desorption energies of CO and CO2. Based on the thermodynamics and kinetics of catalytic reaction, we screened L, selected the best and verified it experimentally. The results are basically consistent with the experimental test results in (5) below.

[0100] (2) Implementation Step 2

[0101] Same as Example 1

[0102] (3) Implementation Step 3

[0103] Same as in Example 1. Finally, (FeCo) was obtained. x M1 y @(((FeCo) z M1 (2Q / n-2z / n) O QThe catalyst is of the type )-((Fe / Co / M1-)-(N / L)-C, where n is the valence state of metal M1 in this catalyst, Q is the number of oxygen atoms in the M1 oxygen body formed, z is a number from 0 to Q, and L = B, Al, P, As, Bi, Sb, S, Se, Te, Br, I, etc.

[0104] (4) (FeCo) x M1 y @(((FeCo) z M1 (2Q / n-2z / n) O Q Microstructure and composition characterization of )-((Fe / Co / M1-)-(N / L)-C type nano-electrocatalytic materials

[0105] The characterization methods used in Example 1 for microstructure and composition show that mixed metal salts and different heteroatom ligands can construct nanocatalysts with the same structure, ranging in size from 0.5 nm to 500 nm. These nanocatalysts are composed of an alloy core, a mixed oxide of M1 and cobalt and iron, M1 / Co / Fe, and a carbon shell co-doped with heteroatoms N and L. M1, cobalt, and iron together with L form the M1 / Co / Fe-N / LC active center.

[0106] (5) (FeCo) x M1 y @(((FeCo) z M1 (2Q / n-2z / n) O Q Electrocatalytic performance characterization of ORR catalyzed by )-((Fe / Co / M1-)-(N / L)-C type nano-electrocatalytic materials

[0107] For the prepared (FeCo) x M1 y @(((FeCo) z M1 (2Q / n-2z / n) O Q The performance characterization results of the ORR catalytic material of the ternary metal alloy nano-electrocatalyst (Fe / Co / M1-)-(N / L)-C type showed that when L = Bi, As, Te, I, the catalytic activity was best when it had heteroatoms with multiple coordination and multiple valence states (e.g., phosphorus with +3 and +5 valences, coordination number up to 5; Te with +4 and +6 valences, coordination number up to 8). However, for higher periods (e.g., sixth-period elements), the catalytic persistence and stability were not very high. Among them, when L = Te, As, I, the half-wave potential could reach 1.0-1.9V, the onset voltage could reach 1.2-2.0V, the Tafel slope could be as small as 0.40mV / dec to 0.20mV / dec, and the chronocurrent response tested at 0.6V could still maintain 96%-99.9% at 36000 seconds.

[0108] The test results of the constructed full-cell test stack show that the calculated volumetric activity can reach 300-1000 A / cm. 3 Compared with the US Department of Energy's 300 A / cm 3 The standard is met or far exceeds the standard. The number of times it can be reused has also been tested, and it can be used repeatedly for more than 1,000 times while maintaining 80-95% or more of its activity.

[0109] Example 7

[0110] (1) Implementation Step 1

[0111] Same as in Example 6

[0112] (2) Implementation Step 2

[0113] In Example 6, the nitrogen-modified porous carbon black used in step 2 of the preparation process of the heteroatom-doped / modified porous support (approximately 10-200 nm in diameter) + heteroatom ligand suspension is replaced with a multi-component heteroatom ligand-modified molecular sieve (such as ZIF-8). Taking N,P-modified ZIF-8 as an example, the specific modification steps are as follows. Nitrogen ligands such as 0.2 g of o-phenanthroline (or porphyrin, or imidazole, or purine, or pyrimidine) and 1.0 g of ZIF-8 are dissolved in a mixed solvent composed of 15 mL of deionized water and 110 mL of ethanol. After mixing for 0.5-2 hours, spray drying is performed to obtain ZIF-8 with a nitrogen ligand surface coating. Then, the obtained nitrogen ligand surface-coated ZIF-8 (about 1.2 g) and 0.3 g of phosphorus ligands (triphenylphosphine (Ph3P), or triphenoxyphosphine (Ph3P=O), or triphenylaminophosphine (Ph3P=NH)) are dissolved in diethyl ether and mixed for 0.5-2 hours. After rotary drying, N-ligand and P-ligand surface-modified ZIF-8 is obtained for later use. Finally, the ZIF-8 is treated in a tube furnace at 400-1000 °C under an inert atmosphere (nitrogen, flow rate 5-40 sccm) for 0.5-2 hours, and then cooled to obtain the desired N, P-modified ZIF-8. To obtain Se or Te co-modified ZIF-8 with N and P, after obtaining the N and P ligands for surface modification of ZIF-8, 0.2 g of selenomethionine or a tellurium compound (such as strontium tellurate) is added to a mixture of ethanol and water. After thorough mixing and spray drying, the mixture is heat-treated in an inert atmosphere in a tube furnace for 0.5-2 hours to construct N,P,Se or N,P,Te modified ZIF-8. In subsequent preparations, ZIF-8 modified with different multi-heteroatom ligands is used instead of N-modified porous carbon as the support in this step, such as N,P-ZIF-8; N,Se-ZiF-8; P,Te-ZIF-8.

[0114] (3) Implementation Step 3

[0115] Same as in Example 6. Finally, (FeCo) was obtained. x M1 y @(((FeCo) z M1 (2Q / n-2z / n) O Q The catalyst is of the type )-((Fe / Co / M1-)-(L)-ZIF-8), where n is the valence state of metal M1 in this catalyst, Q is the number of oxygen atoms in the M1 oxygen body formed, z is a number from 0 to Q, and L = two or more of B, Al, P, As, Bi, Sb, S, Se, Te, Br, I, etc.

[0116] (4) (FeCo) x M1 y @(((FeCo) z M1 (2Q / n-2z / n) O Q Microstructure and composition characterization of )-((Fe / Co / M1-)-(L)-ZIF-8 type nano-electrocatalytic materials

[0117] The characterization methods used in Example 6 for microstructure and composition show that mixed metal salts and different heteroatom ligands can construct nanocatalysts with the same structure, ranging in size from 0.5 nm to 500 nm. These nanocatalysts are composed of an alloy core, M1 and a mixed oxide of cobalt and iron, M1 / Co / Fe, and multi-component heteroatom L co-doped ZIF-8. M1, cobalt, and iron together with L form the M1 / Co / Fe-(L)-(Si / Al) active center.

[0118] (5) (FeCo) x M1 y @(((FeCo) z M1 (2Q / n-2z / n) O Q Electrocatalytic performance characterization of ORR catalyzed by )-((Fe / Co / M1-)-(L)-ZIF-8 type nano-electrocatalytic materials

[0119] The prepared multi-heteroatom modified ZIF-8 supported (FeCo) x M1 y @(((FeCo) z M1 (2Q / n-2z / n) O QThe performance characterization results of the ORR catalysis of the ternary metal alloy nano-electrocatalyst material of type 1-((Fe / Co / M1-)-(L)-ZIF-8) showed that when L=N, P, Te, Sb, and S, the catalytic activity was the best and the activity persistence was also good when it had heteroatoms with multiple coordination and multiple valence states (e.g., phosphorus has +3 and +5 valences, with a coordination number of up to 5; Te has +4 and +6 valences, with a coordination number of up to 8). Among them, when L=Te, As, and I, the half-wave potential can reach 1.0-2.0V, the onset voltage can reach 1.2-2.3V, the Tafel slope can be as small as 0.35mV / dec to 0.20mV / dec, and the chronocurrent response tested at 0.6V can still maintain 97%-99.9% after 36000 seconds.

[0120] The test results of the constructed full-cell test stack show that the calculated volumetric activity can reach 400-1200 A / cm. 3 This exceeds the 300 A / cm² figure published by the U.S. Department of Energy in 2015. 3 The standard was also tested for the number of times it could be reused, and it could be used more than 1,000 times while maintaining an activity level of 84-95% or higher.

[0121] Example 8

[0122] (1) Implementation Step 1

[0123] Same as in Example 6

[0124] (2) Implementation Step 2

[0125] In the preparation step of heteroatom-doped / modified porous support (diameter approximately 10-200 nm) + heteroatom ligand suspension in step 2 of Example 6, the nitrogen-modified porous carbon black used is replaced with cesium phosphotungstenate (Cs-TPA) or bismuth phosphotungstenate (Bi-TPA) surface-modified MCM-41, and the preparation method is as follows. The preparation process of cesium phosphotungstenate is as follows: One gram of purchased MCM-41 was surface-modified with Cs₂CO₃ using an equal-volume impregnation method. Specifically, a saturated aqueous solution of Cs₂CO₃ (261 g / 100 mL) was dropwise added to one gram of MCM-41 until saturation was achieved. The sample was then dried at 110°C and annealed at 500°C for two hours under nitrogen protection to obtain Cs-MCM-41. The sample was then pulverized, and a 1 g / mL phosphotungsten acid (TPA) butanol solution was dropwise added to the prepared Cs-MCM-41 powder until saturation was achieved. The powder was then dried at 110°C and annealed at 300°C for two hours in air to obtain Cs-TPA-MCM-41. This Cs-TPA was then used as a porous support instead of N-modified porous carbon in steps 2 and 3.

[0126] (3) Implementation Step 3

[0127] Same as in Example 6. Finally, (FeCo) was obtained. x M1 y @(((FeCo) z M1 (2Q / n-2z / n) O Q The catalyst is of the type )-((Fe / Co / M1-)-(L)-(Cs-TPA-MCM-41)), where n is the valence state of metal M1 in this catalyst, Q is the number of oxygen atoms in the M1 oxygen body formed, z is a number from 0 to Q, and L = two or more of B, Al, P, As, Bi, Sb, S, Se, Te, Br, I, etc.

[0128] (4) (FeCo) x M1 y @(((FeCo) z M1 (2Q / n-2z / n) O Q Microstructure and composition characterization of )-((Fe / Co / M1-)-(L)-(Cs-TPA-MCM-41)) type nano-electrocatalytic materials

[0129] The characterization methods used in Example 6 for microstructure and composition show that mixed metal salts and different heteroatom ligands can construct nanocatalysts with the same structure, ranging in size from 0.5 nm to 500 nm. These nanocatalysts are composed of an alloy core, M1 and a mixed oxide of cobalt and iron, M1 / Co / Fe, and L-doped Cs-TPA-MCM-41. M1, cobalt, and iron together with L construct various types of catalytic active centers, such as M1 / Co / Fe-(L)-P, M1 / Co / Fe-(L)-Cs, M1 / Co / Fe-(L)-Si, and M1 / Co / Fe-(L)-W.

[0130] (5) (FeCo) x M1 y @(((FeCo) z M1 (2Q / n-2z / n) O Q Electrocatalytic performance characterization of ORR catalyzed by )-((Fe / Co / M1-)-(L)-(Cs-TPA-MCM-41)-type nano-electrocatalytic materials

[0131] The prepared multi-heteroatom modified Cs-TPA-MCM-41 supported on (FeCo) x M1 y @(((FeCo) z M1 (2Q / n-2z / n) O QThe performance characterization results of the ORR catalytic material of the ternary metal alloy nano-electrocatalyst )-((Fe / Co / M1-)-(L)-(Cs-TPA-MCM-41)) type showed that when L=N, P, As, Sb, Bi, Se, I, the catalytic activity was the best and the activity persistence was also good when it had heteroatoms with multiple coordination and multiple valence states (such as phosphorus with +3 and +5 valences, and coordination number up to 8; and Se with +4 and +6 valences, and coordination number up to 8). Among them, when L=P, Sb, Bi, its half-wave potential can reach 1.0-2.2V, the onset voltage can reach 1.2-2.5V, the Tafel slope can be as small as 0.35mV / dec to 0.15mV / dec, and the chronocurrent response tested at 0.6V can still maintain 96%-99.9% after 36000 seconds.

[0132] The test results of the constructed full-cell test stack show that the calculated volumetric activity can reach 500-1500 A / cm. 3 This far exceeds the 300 A / cm² figure published by the U.S. Department of Energy in 2015. 3 The standard was also tested for the number of times it could be reused, and it could be used repeatedly for more than 1,500 times while maintaining an activity level of over 90-98%.

[0133] Example 9

[0134] (1) Implementation Step 1

[0135] Same as in Example 5.

[0136] (2) Implementation Step 2

[0137] Same as in Example 5.

[0138] (3) Implementation Step 3

[0139] In step 3, the preparation of the heteroatom compound atmosphere for high-temperature pyrolysis is achieved by placing a solid heteroatom ligand in a container with a vent at heating section I in step 3, controlling the heating temperature of this section to exceed the boiling point or sublimation point of the compound. An inert carrier gas (argon is used here) is passed through this heating vaporization section to construct a pyrolysis atmosphere containing heteroatoms. The solid heteroatom ligands used here are iodine, triphenylbismuth, diphenyldiselenoether, and cerium dodecanoate dodecoborate, with an amount of 0.1-2 g; the temperatures at heating section I are controlled at 190℃, 320℃, 390℃, and 680℃, respectively.

[0140] Finally, FeCo was obtained with improved overall doping levels of heteroatoms iodine (I), bismuth (Bi), selenium (Se), and iodine-cerium-boron (I-Ce-B). x M1 y @(((FeCo) z M1(2Q / n-2z / n) O Q The catalyst is of the type )-((Fe / Co / M1-)-LC), where n is the valence state of metal M1 in this catalyst, Q is the number of oxygen atoms in the M1 oxygen body formed, z is a number from 0 to Q, and L = B, Al, P, As, Bi, Sb, S, Se, Te, Br, I.

[0141] (4) (FeCo) x M1 y @(((FeCo) z M1 (2Q / n-2z / n) O Q Microstructure and composition characterization of )-((Fe / Co / M1-)-LC) type nano-electrocatalytic materials

[0142] The characterization methods used in Example 1 for microstructure and composition show that mixed metal salts and different heteroatom ligands can construct nanocatalysts with the same structure, ranging in particle size from 0.5 nm to 500 nm. These nanocatalysts are composed of an alloy core, a mixed oxide of M1 and cobalt and iron, and a co-doped carbon shell of M1 / Co / Fe and heteroatom L. M1, cobalt, and iron together with L form the M1 / Co / Fe-LC active center. For heteroatoms such as iodine (I), bismuth (Bi), selenium (Se), and iodine-cerium-boron (I-Ce-B), the overall doping levels are increased by 50%, 20%, 40%, and 70%-100%-20%, respectively.

[0143] (5) (FeCo) x M1 y @(((FeCo) z M1 (2Q / n-2z / n) O Q Electrocatalytic performance characterization of ORR catalyzed by )-((Fe / Co / M1-)-LC) type nano-electrocatalytic materials

[0144] For the prepared (FeCo) x M1 y @(((FeCo) z M1 (2Q / n-2z / n) O QThe performance characterization results of the ternary metal alloy nano-electrocatalyst material of type 1-((Fe / Co / M1-)-LC) catalyzing ORR show that when L = I, Bi, Se, and I-Ce-B, it has heteroatoms with multiple coordination and multiple valence states, which can significantly improve the catalytic activity. Its half-wave potential can reach 1.3, 1.4, 1.5, and 2.0 V, its onset voltage can reach 1.3, 1.8, 1.6, and 2.1 V, and its Tafel slope can be as small as 0.35 mV / dec, 0.30 mV / dec, 0.26 mV / dec, and 0.24 mV / dec. The chronocurrent response tested at 0.6 V can still maintain 95%, 98%, 94%, and 99% after 36,000 seconds.

[0145] Table 1 shows the atomic percentages of each element in heterostructure catalysts prepared with different Co / Fe ratios based on XPS measurements.

[0146] Samples with different Co / Fe ratios Pyridine N (%) Pyrrole N (%) Graphite N (%) NO (%) Co / Fe = 0.001 / 1 38.2 22.5 36.0 3.3 Co / Fe = 1 / 2 12.3 43.3 38.9 5.4 Co / Fe = 1 / 1 14.1 43.0 41.3 1.7 Co / Fe = 2 / 1 9.8 39.3 42.1 8.8 Co / Fe = 1 / 0.001 12.4 37.6 41.6 8.4

[0147] Table 2 shows the proportions of different types of nitrogen in heterostructure catalysts prepared under different Co / Fe ratios, obtained by fitting the N 1s peak.

[0148] Samples with different Co / Fe ratios C 1s (%) O 1s (%) N 1s (%) Fe 2p (%) Co 2p (%) Co / Fe = 0.001 / 1 95.21 3.88 0.58 0.23 - Co / Fe = 1 / 2 95.71 3.04 0.85 0.26 0.14 Co / Fe = 1 / 1 93.16 4.83 1.32 0.31 0.38 Co / Fe = 2 / 1 95.99 3.02 0.59 0.21 0.18 Co / Fe = 1 / 0.001 96.83 2.17 0.59 - 0.23

Claims

1. A method for preparing a porous carrier-supported metal alloy@metal oxide embedded metal and heteroatom L co-doped carbon shell C heterostructure nano-electrocatalytic material, characterized in that, Includes the following steps: (1) Ultrasonic atomization microsol formation: the alkaline solution is formed into microdroplets by ultrasonic atomization and dropped into a mixed metal salt solution containing a dispersant to construct a multi-component polyhydroxy metal mixture sol. The sol is centrifuged and washed several times with distilled water for later use. The metals mentioned include at least metal A and metal B. (2) Sol-gel phase transformation to prepare multi-metal-heteroatom complex gel: After washing the multi-metal polyhydroxy metal mixture sol, the porous carrier and the ligand containing heteroatom L are mixed and added to the solvent and mixed evenly. The heteroatom of the ligand and the hydroxyl group undergo a substitution reaction and / or a complexation reaction with the metal, so that the multi-metal polyhydroxy metal sol gels and forms metal-heteroatom complex microgels loaded on the porous carrier. Then, the mixture is centrifuged into a slurry and washed clean, and then dried into powder using an organic solvent spray dryer. (3) High-temperature pyrolysis preparation of metal alloy core-metal oxide embedded metal and heteroatom L co-doped carbon shell electrocatalyst. The powder is placed on a petri dish in a quartz tube furnace and spread evenly. It is calcined under different atmosphere ranges to obtain metal alloy@metal oxide embedded metal and heteroatom L co-doped carbon shell C heterostructure nano-electrocatalyst material. In step (1), metal A and metal B are Fe and Co, or metal A and metal B are Co and M1, or metal A and metal B are Fe and Co, and the metal also includes M1, which is selected from Sc, Ti, V, Cr, Ni, Mn, Zn, Cu, Cr, Ti, Mo, Y, Ag, Nb, Au, Pt, Pd, Ir, Ru, Rh, Oe, La, Ce, Gd, Nd, Ho, K, Rb, Cs, Be, Mg, Ca, Ga, In, Ge, Sn, Pb, Sb, Bi; In step (2), the heteroatom L is selected from boron, N, P, As, Sb, Bi, S, Se, and Te.

2. The method for preparing the porous carrier-supported metal alloy@metal oxide embedded metal and heteroatom L co-doped carbon shell C heterostructure nano-electrocatalytic material according to claim 1, characterized in that, The metal salts are water-soluble metal salts of halides, sulfates, nitrates, perhalates, and phosphates, with a concentration range of 0.01M to 1M; the alkaline solutions are selected from LiOH, NaOH, KOH, RuOH, Be(OH)2, Ca(OH)2, sodium borohydride, ammonia, hydrazine hydrate, and ethylenediamine, with a concentration range of 0.01M to 1M.

3. The method for preparing the porous carrier-supported metal alloy@metal oxide embedded metal and heteroatom L co-doped carbon shell C heterostructure nano-electrocatalytic material according to claim 1, characterized in that, Step (2) The carrier is selected from porous activated carbon black, graphene oxide sheets, carbon nanotubes, modified molecular sieves, porous hydroxyapatite, cerium phosphotungstate modified nanoporous silica, cerium phosphotungstate modified nanoporous alumina, and cerium phosphotungstate modified nanoporous titanium dioxide, with a concentration of 0.1 g / L to 500 g / L; the concentration of ligands containing heteroatoms L is 0.1 g / L to 200 g / L.

4. The method for preparing the porous carrier-supported metal alloy@metal oxide embedded metal and heteroatom L co-doped carbon shell C heterostructure nano-electrocatalytic material according to claim 3, characterized in that, The modified molecular sieve is imidazole-modified ZIF-8.

5. The method for preparing the porous carrier-supported metal alloy@metal oxide embedded metal and heteroatom L co-doped carbon shell C heterostructure nano-electrocatalytic material according to claim 3, characterized in that, The molar ratio of the ligand containing the heteroatom L to the metal is 1:10-10:1; the doping method is construction.

6. The method for preparing the porous carrier-supported metal alloy@metal oxide embedded metal and heteroatom L co-doped carbon shell C heterostructure nano-electrocatalytic material according to claim 1, characterized in that, In step (2), when the multi-component polyhydroxy metal mixture sol, porous carrier, and ligand containing heteroatoms L are mixed and reacted, a Y-type microchannel mixer is used.

7. The method for preparing the porous carrier-supported metal alloy@metal oxide embedded metal and heteroatom L co-doped carbon shell C heterostructure nano-electrocatalytic material according to claim 1, characterized in that, The ligand containing the heteroatom L is selected from one or more of the following: phenanthrene, purines, pyrimidines, amino acids, polyamino acids, triphenylphosphine, selenomethionine, triphenylarsine, polyborane salts, alkoxybismuth, alkoxyselenium, and alkoxysulfur.

8. The method for preparing the porous carrier-supported metal alloy@metal oxide embedded metal and heteroatom L co-doped carbon shell C heterostructure nano-electrocatalytic material according to claim 7, characterized in that, Polyhedral boranes are spherical Li2(B 12 Br 12 ), Ce(B 12 I 12 )2, or Cs2(B 12 H 12 ).

9. The method for preparing the porous carrier-supported metal alloy@metal oxide embedded metal and heteroatom L co-doped carbon shell C heterostructure nano-electrocatalytic material according to claim 1, characterized in that, The solvent is a solvent capable of dissolving metal hydroxide sols and heteroatom ligands, selected from ethanol, diethyl ether, acetone, and benzene.

10. The method for preparing the porous carrier-supported metal alloy@metal oxide embedded metal and heteroatom L co-doped carbon shell C heterostructure nano-electrocatalytic material according to claim 1, characterized in that, In step (3), the different atmospheres are an inert atmosphere and / or a precursor atmosphere for the heteroatom element to be doped. The precursor atmosphere for the heteroatom element to be doped is selected from ammonia, imidazole, phosphine, borane, sulfur vapor, sulfur dioxide vapor, and selenium dioxide vapor, with a content of 5-20V. If the atmosphere is the solid substance at room temperature, the solid substance is heated in front of the metal-heteroatom complex microgel loaded in the tube furnace and heated. The heating temperature is controlled above or below its boiling point or sublimation point. The evaporation rate is controlled by the temperature and the solid substance enters the reaction system through an inert carrier gas. The overall flow rate of the atmosphere gas is 5-40 sccm. The heteroatoms in step (3) are the same as or different from those in step (2). If they are the same, the doping amount can be further increased. If they are different, new doping elements can be introduced. The calcination temperature is controlled between 400℃ and 1400℃, and the material is cooled down and discharged after holding the temperature for 0.5-4 hours.

11. The method for preparing the porous carrier-supported metal alloy@metal oxide embedded metal and heteroatom L co-doped carbon shell C heterostructure nano-electrocatalytic material according to claim 1, characterized in that, The resulting material has the following structure: a metal alloy as the inner core, and a metal oxide embedded in a carbon shell co-doped with metal and heteroatom L, forming a heterostructure; the above heterostructure is loaded on a porous support to form a nano-electrocatalytic material.

12. The application of the porous carrier-supported metal alloy@metal oxide embedded metal and heteroatom L co-doped shell C heterostructure nano-electrocatalytic material prepared according to any one of claims 1-11, as an electrocatalytic material for electrocatalytic redox reactions.

Images