CN115418661A - A supported heterostructure nano-electrocatalytic material AB@(ABOx)-(A/B-)-L-C and its preparation - Google Patents

Abstract

The invention relates to a supported heterostructure nano-electrocatalytic material AB@(ABO _x )-(A/B-)-L-C and its preparation, belonging to the field of nano-electrocatalytic materials. The invention uses mixed metal salts, alkali solution and heteroatom ligands as raw materials, and uses porous carriers to invent ultrasonic atomization microgelation combined with high-temperature pyrolysis in the atmosphere to prepare a loaded type with metal alloy as the core and metal oxide embedded Metal-heteroatom co-doped carbon layer metal alloy@metal-heteroatom co-doped carbon heterostructure electrocatalytic material, which has higher electrocatalytic performance than commercial Pt/C, suitable for fuel cells and carbon dioxide Preparation of electrode catalyst layer for resource utilization.

Description

A Supported Heterostructure Nano-electrocatalytic Material AB@(ABOx)-(A/B-)-L-C and preparation

technical field

The invention relates to a novel heterostructure nano-electrocatalytic material and its large-scale preparation method, especially a metal alloy (AB)@metal oxide (ABO _x ) mosaic metal (AB) and heteroatom (L) co-doping The shell (C) heterostructure nano-electrocatalytic material (AB@(ABO _x )-(A/B-)-LC) and its preparation method belong to the technical field of novel heterostructure hybrid materials.

Background technique

Zero or low-carbon emission clean energy and carbon neutral technology are two key technologies to ensure China's carbon compliance and ecological environment quality. The corresponding fuel cell (FC) and _CO2 resource technology have become key development areas; among them, acidic proton exchange Membrane (PEM) or alkaline anion exchange membrane (AEM) alcohol/hydrogen FC has the characteristics of low operating temperature (25-100°C), high energy conversion efficiency, zero or low carbon emissions, and has become a key development direction. Hydrogen energy has the characteristics of high power density per unit mass, no carbon emissions, abundant reserves, recyclability, and no solid and liquid waste. It has become inevitable to replace fossil energy.

The core component of a hydrogen-based FC is the stack, which is mainly composed of electrodes, electrolyte diaphragms, and bipolar plates. Bipolar plates and gas diffusion layers (GDL), ion exchange membranes and catalyst layers are the main costs, accounting for about 70% of the current relatively mature commercial PEMFC stacks, of which catalysts account for 21%. Although many low-platinum alloys and non-platinum catalysts have also been developed, due to the catalytic performance (especially catalytic oxygen reduction reaction (ORR)) of activity, anti-poisoning and durability, safety, cycle life and other indicators still need to be improved, the current commercial The PEMFC electrode catalyst materials are still Pt-like rare metals or their alloys. Although the optimization of the PEM material and its interfacial recombination with the active layer can improve its cost performance, it is difficult to greatly reduce the cost of electrode catalytic materials due to the limitation of rare and expensive Pt-based raw materials (currently, the average amount of Pt used in PEMFC negative electrodes is about 0.4mg Pt/cm ² ) has achieved sustainable development, which seriously restricts the development of FC industrialization. my country basically relies on imports of high-performance rare and precious metal electrocatalytic materials, such as Pt, Ir, Pd, Ru, Rh, etc., through commercial channels. Therefore, in order to solve the high cost and continuous application of Pt and other rare metal electrode catalytic materials, it is necessary to develop high-performance non-rare noble metal (NRNM) and low-level rare metal (LRNM) high-efficiency catalysts, which are the next generation of cost-effective PEMFC and new A generation of safer and more reliable AEMFC stacks and key catalytic materials for resource utilization of carbon dioxide.

The invention uses mixed metal salts, alkali solutions and heteroatom ligands as raw materials, and uses porous carriers to invent ultrasonic atomization microgelation combined with high-temperature pyrolysis process to prepare a loaded type with metal alloy as the core and metal oxide embedded metal -Heterostructure metal-heteroatom hybrid carbon electrocatalytic material with heteroatom co-doped carbon layer as the shell, which has higher electrocatalytic performance than commercial Pt/C, and is suitable for electrodes for fuel cells and carbon dioxide resource utilization Preparation of the catalyst layer.

Contents of the invention

Aiming at the problems that the existing rare and precious metal and non-rare precious metal electrocatalytic materials for fuel cell and carbon dioxide resource utilization need to be improved in terms of activity, poisoning resistance, durability, safety and cycle life, and the cost needs to be greatly reduced, the present invention designs and A new type of composite and hybrid electrocatalytic material was prepared, and a large-scale preparation method of ultrasonic atomization microsolification-heteroatom coordination gelation combined with atmosphere pyrolysis process was invented, which has the advantages of its shape and size. , The characteristics of the flexible regulation of the microstructure and composition of the heterogeneous interface.

Described preparation process comprises the following steps:

(1) Ultrasonic atomization microsolization, the alkali solution is formed into micro-droplets by ultrasonic atomization, and dropped into the mixed metal salt solution containing the dispersant to construct a multi-component polyhydroxy metal mixture sol, and the sol is centrifuged by a centrifuge, Washing several times with distilled water for later use; the metals at least include metal A and metal B;

(2) Sol-gel phase inversion to prepare multi-element metal-heteroatom complex gel, mix the washed multi-element polyhydroxy metal mixture sol with porous carrier and ligand containing heteroatom L, then add to the solvent and mix evenly , Ligand heteroatoms and hydroxyl groups undergo substitution reactions or/and complexation reactions with metals to gel the multi-component polyhydroxy metal sol to form metal-heteroatom complex microgels loaded on porous carriers, and then centrifuged to form a slurry Slurry is washed and dried into powder using an organic solvent spray dryer;

(3) Prepare the metal alloy core-metal oxide mosaic heteroatom-doped shell electrocatalyst by pyrolysis, put the powder into the surface dish in the quartz tube furnace and spread it evenly, and perform calcination under different atmosphere ranges, Metal alloy (AB)@metal oxide (ABO _x ) mosaic metal (A/B) and heteroatom (L) co-doped shell (C) heterostructure nano-electrocatalytic material (AB@((ABO _x ) -(A/B-)-LC).

Wherein the metal A and metal B in the step (1) are all 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 of IA , Cs; 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, metal A and metal B are a single metal or multiple Metal; the ratio of metal A to metal B is not limited, such as the molar ratio is 10:1-1:10, etc., it can be adjusted as needed;

Metal salts are metal salts soluble in water such as halides, sulfates, nitrates, perhalogenates, phosphates, etc., and their concentration ranges from 0.01M to 1M; alkaline solutions are alkali metals (LiOH, NaOH, KOH, RuOH )), alkaline earth metal (such as Be(OH) ₂ , Ca(OH) ₂ ), sodium borohydride or organic strong base (such as ammonia water, hydrazine hydrate, ethylenediamine) solution, the concentration is 0.01M to 1M.

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 (Al ₂ O ₃ @Cs-TPA), cerium phosphotungstate modified titanium oxide (TiO ₂ @Cs-TPA), etc. Or other modified carriers, the use concentration is 0.1g/L to 500g/L;

In step (2), the heteroatom L doped with the carbon shell is selected from one or more elements except carbon and oxygen in the main group elements of IIIA, IVA, VA, and VIA, such as boron (Boron), Al, Ga , Sn, N, P, As, Sb, Bi, S, Se, Te, the doping method is construction. The ligand containing heteroatom L is selected from such as o-phenanthroline, purines, pyrimidines, polyamino acids, triphenylphosphine, selenomethionine, triphenylarsenic, polyborane salt (such as spherical deca Cesium diborobromide Cs ₂ (B ₁₂ Br ₁₂ ), Ce(B ₁₂ Br ₁₂ ) ₂ , Lithium dodecaborohydride Li ₂ (B ₁₂ H ₁₂ )), bismuth alkoxide, alkane One or more of oxyselenium, alkoxysulfur, etc.;

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 0.1 g/L to 200 g/L.

The solvent is a solvent capable of dissolving the metal hydroxide sol and the heteroatom ligand, such as ethanol, ether, acetone, benzene and the like.

Step (2) When the multi-component polyhydroxy metal mixture sol is mixed and reacted with the porous carrier and the ligand containing the heteroatom L, a Y-shaped microchannel mixer is used.

The different atmospheres in step (3) are an inert atmosphere or/and a precursor atmosphere of a heteroatom element to be doped further, and the precursor atmosphere of a heteroatom element to be doped is selected from ammonia, imidazole, phosphine, boron Alkane, sulfur vapor, sulfur dioxide vapor, selenium dioxide vapor, etc., with a content of 5-20V%; if the room temperature is an atmosphere corresponding to a solid substance, by placing the solid substance (such as sulfur, selenium dioxide, bismuth alkoxide) on The metal-heteroatom complex microgel loaded in the tube furnace is heated in front of the porous carrier, the heating temperature is controlled above or below its boiling point or sublimation point, the evaporation amount is controlled by the temperature, and the inert carrier gas enters the reaction system ; The overall flow rate of the atmosphere gas is 5-40sccm. The doped heteroatoms in step (3) may be the same as or different from those in step (2). When they are the same, the overall doping amount can be further increased; when they are different, new doping elements can be further introduced.

At this time, if the atmosphere is by evaporating solid heteroatom compounds, it is placed on the quartz petri dish in the front temperature control zone of the heating furnace, then the inert gas valve is opened, and the gas flow rate is controlled at 10-40 sccm as required, and the furnace is turned on again. The temperature is gradually increased to the required cracking temperature. Generally, the calcination temperature is controlled between 400°C and 1400°C, and the temperature is lowered after 0.5-4 hours of heat preservation.

The material structure obtained in the present invention is: the metal alloy AB is the core, the metal oxide ABOx is the inlaid metal and the heteroatom L co-doped metal-heteroatom co-doped layer is the shell C, forming a heterostructure; the above heterostructure Loaded on a porous carrier to form a nano-electrocatalytic material, the above-mentioned heterostructure metal-heteroatom hybrid (carbon) electrocatalyst with a metal alloy as the core and a metal oxide embedded metal-heteroatom co-doped layer as the shell The catalytic material obtained a new type of nano-electrocatalytic material (AB@(ABOx)-(A/B-)- L-C).

The application of the obtained material in the present invention is used as an electrocatalytic material for electrocatalytic redox reactions.

The ultrasonic atomization microsolization device used in the first step of the present invention has the ability to prepare polyhydroxy metal sol on a large scale, and the small laboratory device has the ability of 50-100g/time; the second step heteroatom coordination gelation The process has flexible and diverse control capabilities, and can replace the required solvents, porous carriers, and heteroatom ligands according to needs, providing a variety of precursors for subsequent high-temperature understanding and preparation; while the atmosphere-controlled high-temperature pyrolysis has the ability to control the atmosphere. Realize the ability to heteroatomize electrocatalysts and their pre-used supports and increase the overall catalytic site density.

Description of drawings

Fig. 1 is the ultrasonic atomization microsolization process controlled by the micro material liquid pump used in the preparation process step 1 of the present invention, the microfluid heteroatom coordination gelation process used in the step 2 and the atmosphere pyrolysis process used in the step 3 and its principle and Schematic diagram of device structure;

Figure 2 is the morphology characterization of the Co ₃ Fe ₇ @(CoFe ₂ O ₄ )-(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, ie 10 ^-9 meters).

Figure 3 is the electron energy loss spectrum of a single Co ₃ Fe ₇ @(CoFe ₂ O ₄ )-(Co/Fe-)-NC) heterostructure nanocatalytic material: (a) overall morphology; (b) (c) Fe; (d) Co; (e) C; (f) N; (g) O; (h) C+N overlay; (i) Fe+N

Figure 4 shows the morphology and structure characterization of the local core-shell interface of a single Co ₃ Fe ₇ @((CoFe ₂ O ₄ )-(Co/Fe-)-NC) heterostructure nanocatalytic material: (a) single particle TEM image of ; (b) HR-TEM image of the corresponding area (upper) and fast Fourier for CoFe ₂ O ₄ (311) crystal plane (lower left) and Co ₃ Fe ₇ (110) crystal plane (lower right) Leaf transformation map.

Figure 5 shows the electrocatalytic oxygen reduction reaction of Co ₃ Fe ₇ @((CoFe ₂ O ₄ )-(Co/Fe-)-NC) heterostructure nanocatalytic materials in 0.1M-KOH medium and commercial Pt/C ( ORR) catalytic performance of the linear sweep voltammetry (LSV) curve comparison chart.

Figure 6 shows the electrocatalytic oxygen reduction reaction of Co ₃ Fe ₇ @((CoFe ₂ O ₄ )-(Co/Fe-)-NC) heterostructure nanocatalytic materials in 0.1M-KOH medium and commercial Pt/C ( ORR) catalytic performance Tafel slope comparison plot.

Figure 7 shows the electrocatalytic oxygen reduction reaction of Co ₃ Fe ₇ @((CoFe ₂ O ₄ )-(Co/Fe-)-NC) heterostructure nanocatalytic materials in 0.1M-KOH medium and commercial Pt/C ( Nyquist plot of electrochemical impedance spectroscopy (EIS) for catalytic performance of ORR).

Figure 8 shows the effect of Co ₃ Fe ₇ @((CoFe ₂ O ₄ )-(Co/Fe-)-NC) heterostructure nanocatalytic materials in 0.1M-KOH medium and commercial Pt/C electrode at 0.6V voltage. Comparison chart of chronoamperometric response curves of catalytic oxygen reduction reaction (ORR) catalytic performance test.

Figure 9 shows Co _x Fe _y @((Coz Fe _{(3-z) O 4} )-(Co/Fe-)-NC) catalysts prepared under different Co:Fe molar ratios (x: 0.001-1; TEM images of the microstructure characterization of y: 1-0.001; z: 0.001-3). (a), (b) TEM and high-resolution TEM of nanoparticles with Co/Fe=0.001/1; (c), (d) TEM and high-resolution TEM of nanoparticles with Co/Fe=1/2 as F2C1; (e), (f) TEM and high-resolution TEM of Co/Fe=2/1 nanoparticles; (g), (h) TEM and high-resolution TEM of Co/Fe=1/0.001 nanoparticles.

Fig. 10 Co _x Fe _y @((Coz Fe _{(3-z) O 4} )-(Co/Fe-) Linear sweep voltammetry (LSV) curves of the ORR electrocatalytic performance of -NC) nanoelectrocatalytic materials and commercial Pt/C.

Figure 11 Co _x Fe _y @((Coz Fe _{(3-z) O 4} )-(Co/Fe-)-NC) nano-electrocatalytic materials and commercial Pt prepared under different Co/Fe ratios in mixed metal salt raw materials /C's Tafel curve slope comparison graph.

Figure 12 Co _x Fe _y @((Coz Fe _{(3-z) O 4} )-(Co/Fe-)-NC) nano-electrocatalytic materials and commercial Pt prepared under different Co/Fe ratios in mixed metal salt raw materials Nyquist plot of electrochemical impedance spectroscopy (EIS) of /C.

Figure 13 Co _x Fe _y @((Coz Fe _{(3-z) O 4} )-(Co/Fe-)-NC) nano-electrocatalytic materials and commercial Pt prepared under different Co/Fe ratios in mixed metal salt raw materials Chronoamperometric response curves of electrocatalytic oxygen reduction reaction (ORR) catalytic performance test in 0.1M-KOH medium at 0.6V voltage of /C.

Table 1 shows the atomic percentages of each element in the heterostructure catalysts prepared under different ratios of Co/Fe according to the XPS test.

Table 2 The ratio of N species content in heterostructure catalysts prepared under different ratios of Co/Fe obtained by N1s peak fitting.

Detailed ways

The present invention will be further described below in conjunction with the examples, but the present invention is not limited to the following examples.

Example 1

(1) Implement step 1

Preparation of lye in step 1: Take 0.56g of KOH in a PTFE beaker, add 25mL of deionized water, and vibrate in an ultrasonic oscillator for 2min to fully dissolve it.

Preparation of mixed metal salt solution in step 1: Take 0.5g FeCl ₂ 4H ₂ O (2.5mmol) and 0.6g CoCl ₂ 6H ₂ O (2.5mmol) in a beaker, then add 0.75g polyvinylpyrrolidone (PVP) , Add 50mL of ethanol and 50mL of deionized water into a glass beaker, and oscillate ultrasonically for 2 minutes to fully dissolve it.

In Figure 1, feed liquid pump 1 is used to send the alkali solution to the ultrasonic atomizer at a flow rate of 1mL/min for atomization into micro-droplets of 4-5 micron size, and then sputtered into the feed liquid pump 2 at a flow rate of 2mL In the mixed metal salt solution sent at a flow rate of /min, the microsol of polyhydric iron and polyhydroxycobalt is formed by precipitation reaction, and then enters the multi-metal polyhydroxy compound microsol formation pool together for use. (The diameter of the pipeline used for pumping is 0.5mm-5mm). At this time, a centrifuge can be used for centrifugal separation and ethanol washing of this type of microsol for 2-3 times and then dissolved in a mixed solvent of 125mL ethanol-water (1:1) for later use. ), the time is 5-30min (minutes).

(2) Implement step 2

Preparation of heteroatom-doped/modified porous carrier (about 10-200nm in diameter)+heteroatom ligand suspension in step 2: 0.2g o-phenanthroline and 1.0g nitrogen-modified porous carbon black were dissolved in 15ml In a mixed solvent constructed of ionic water and 110mL ethanol, stir for 30min to fully dissolve it for later use.

Use liquid pumps 3 and 4 to pump the multi-element metal polyhydroxy compound microsol solution and the heteroatom-doped/modified porous carrier+heteroatom ligand suspension to the Y-shaped microchannel mixer (the diameter of the pipeline is 0.5mm- 5mm) and mixed evenly, then the heteroatom ligand loaded on the porous carrier will undergo ligand exchange reaction with the hydroxyl group in the multi-metal polyhydroxy compound and gelation will occur, forming a multi-element metal-heteroatom complex microparticle on the porous carrier. Gel: and enter into the heteroatom-modified porous carrier loaded multi-element metal-heteroatom complex microgel collector. Then after centrifugation and washing, dissolve in 50mL aqueous solution containing 30V% ethanol, use an organic solvent spray dryer to dry into powder, and obtain the precursor powder of the catalyst: heteroatom modified porous carrier loaded multi-element metal-heteroatom complex Microgel powder.

(3) Implement step 3

In step 3, in the preparation of the heteroatom compound atmosphere for high-temperature cracking, the inert carrier gas (nitrogen is used here) is passed through 35% concentrated ammonia water saturated with ammonia to form an ammonia-containing cracking atmosphere carrier gas. At this time, if necessary, the heteroatom compound used to obtain the heteroatom compound atmosphere is solid at room temperature (such as iodine, sulfur, SeO ₂ , (NH ₄ ) ₂ CO ₃ , CO(NH ₂ ) ₂ , triphenylphosphine ( TPP)), it will be placed in the container with vent at the heating section I place in step 3, by controlling the section heating temperature to exceed the boiling point or sublimation point of the compound. Not used in this example.

Put the heteroatom-modified porous carrier loaded multi-element metal-heteroatom complex microgel powder prepared in step 2 on the watch glass on the porous stage of the heating section III of the high-temperature furnace in step 3, spread evenly In a 20sccm (standard cubic centimeter per minute, standard mL/min) carrier gas atmosphere, raise the furnace temperature to 800°C and keep it warm for 2 hours for high temperature analysis in a heteroatom compound atmosphere, and then lower the temperature in an inert atmosphere carrier gas After reaching room temperature, take out the prepared catalyst powder, wash with ethanol solvent and centrifuge for 2-3 times, and then use the furnace to dry and anneal at 800°C under nitrogen atmosphere to obtain the required cobalt-iron alloy as Core, co-doped carbon shell heterostructure nano-electrocatalytic materials co-doped with cobalt oxide cobalt/iron and nitrogen atoms: Co ₃ Fe ₇ @((CoFe ₂ O ₄ )-(Co/Fe-)-NC)nano Electrocatalytic materials.

(4) Microstructure and composition characterization of Co ₃ Fe ₇ @((CoFe ₂ O ₄ )-(Co/Fe-)-NC) nano-electrocatalytic materials.

Figure 2 is the wide-field high-angle annular dark-field scanning transmission electron microscope image (HAADF-STEM) of the prepared Co ₃ Fe ₇ @(CoFe ₂ O ₄ )-(Co/Fe-)-NC) nano-electrocatalytic material. The particles on the carbon carrier have an obvious core-shell structure, and the statistics of the particle size show that the size is between 50 and 400nm, with an average diameter of about 190nm, and a shell thickness of 10-20nm, with an average thickness of 18nm. The HAADF-STEM image of a single particle shows that the inner core is brighter than the outer shell (this is a dark field image), indicating that the inner core is composed of atoms heavier than the outer shell (such as CoFe inner core and carbon-based material outer shell). Figure 3 is the characterization result of another typical single particle core core shell element distribution. It can be seen that the core is dominated by CoFe alloy, Co is mainly concentrated in the core, and the shell content is less than that of iron. In addition to the core, iron is also contained in a large amount in the shell and the content is higher than cobalt. According to the binary phase diagram, X-ray diffraction pattern (XRD) and element quantitative content analysis of cobalt-iron alloy, it shows that the inner core is Co ₃ Fe ₇ alloy. The analysis of carbon, nitrogen and oxygen elements shows that: carbon and nitrogen are basically distributed in the shell, indicating that the shell is nitrogen-doped modified carbon; oxygen is concentrated in the shell, but also at the interface, indicating that the core-shell Cobalt oxide exists at the interface. The analysis of non-metallic elements and the analysis of the high-resolution electron micrograph and crystal structure of the core-shell interface of a single particle in Figure 4 have been consistent, and the high-resolution electron micrograph and Fourier transform crystal structure of the interface microstructure in the middle of Figure 4 Its core is Co ₃ Fe ₇ alloy, CoFe ₂ O ₄ grains grow in the interface, and the shell layer is an amorphous carbon layer with many partial crystallization (graphitization). According to the distribution of iron and cobalt in the shell layer is basically very uniform, it can be concluded that cobalt, in addition to building cobalt oxides, co-doped carbon together with nitrogen in the shell layer to modify or form iron carbide and cobalt carbide. According to XRD analysis, It does not have obvious Fe ₃ C or Co ₃ C peaks. According to its Raman spectrum, its degree of graphitization is very high, indicating that most of it is co-doped with nitrogen into the carbon of the shell graphitization structure. , constructing a large number of metal atom-nitrogen-carbon (graphitized) single-atom or multi-atom active sites. Furthermore, the characteristics of the nitrogen ligands in the metal atom-nitrogen-carbon active sites were characterized, mainly based on the proportion of N species content obtained by fitting the N1s peak characterized by XPS. The results showed that the proportion of nitrogen ligands was as follows: pyridine type nitrogen was 14%, pyrrole type nitrogen was 43.0%, graphite type nitrogen was 42.3% and oxynitride type nitrogen content was 1.7%.

(5) Characterization of electrocatalytic performance of Co ₃ Fe ₇ @((CoFe ₂ O ₄ )-(Co/Fe-)-NC) nano-electrocatalytic materials for ORR

Fig. 5 shows the reaction of Co ₃ Fe ₇ @((CoFe ₂ O ₄ )-(Co/Fe-)-NC) nano-electrocatalytic materials and commercial Pt/C pair in 0.1M KOH electrolyte using rotating disk electrode (RDE). Comparison of linear sweep voltammetry (LSV) curves of the electrocatalytic performance of ORR, the results show that it has a larger positive potential and higher current density than commercial Pt/C. Its initial potential and half-wave potential reach 1.05V and 0.89V (electrocatalytic activity index) respectively, and the corresponding Pt/C is 0.95V and 0.84V; the calculated current density can reach 27mA/cm ² , while The corresponding Pt/C is only 5mA/cm ² . Figure 6 is a comparison of the Tafel slopes of the catalyst and Pt/C electrocatalytic ORR performance, and the results show that the Tafel slope (69mV/dec) of the catalyst is lower than that of the commercial Pt/C catalyst (76mV/dec), It shows that it exhibits higher activity than commercial Pt/C catalysts in the rate-limiting step. The Nyquist plot of the electrochemical impedance spectroscopy (EIS) of Pt/C in Figure 7 shows that the semicircle diameter ratio of Co ₃ Fe ₇ @((CoFe ₂ O ₄ )-(Co/Fe-)-NC) nano-electrocatalytic materials The Pt/C catalyst is much smaller, which means that the Co ₃ Fe ₇ @(CoFe ₂ O ₄ )-(Co/Fe-)-NC) nano-electrocatalytic material has a lower charge transfer resistance and more favorable electron transfer in the reaction . The stability is directly related to the lifetime of the catalyst, as shown in Figure 8, the chronoamperometry response tested at 0.6V shows that after 36,000 seconds, Co ₃ Fe ₇ @((CoFe ₂ O ₄ )-(Co/Fe-) -NC) catalyst maintained 87.0% of the initial value, much higher than 55.5% of the commercial Pt/C catalyst, indicating that Co ₃ Fe ₇ @((CoFe ₂ O ₄ )-(Co/Fe -)-NC) electrocatalysts exhibit excellent catalytic activity durability. According to the characterization of its microstructure, compositional crystal structure and elemental electronic structure, it can be concluded that the above has better catalytic ORR performance than commercial Pt/C, mainly due to the highly conductive CoFe alloy core and the high-temperature pyrolysis process in the atmosphere. The metal- and nitrogen-modified highly graphitized carbon-based shell has higher conductivity and more metal-nitrogen-carbon-constructed single-polyatomic active centers than carbon-supported Pt nanocatalysts, while the interface or carbon layer embedded The combined cobalt oxide itself has higher catalytic activity under the cooperation of the metal alloy core. According to the accepted theoretical research results, the single-polyatomic active center constructed by the metal-nitrogen-carbon structure is related to the nitrogen coordination form. Both the pyridine nitrogen and the model nitrogen are sp2 hybridized, contributing a p electron to the π system. Pyrrole nitrogen is sp3 hybridized and contributes two p-electrons to the π system, so pyridinic nitrogen and graphitic nitrogen have greater electronegativity than ^pyrrole nitrogen25,26 (the slightly lower electronegativity of pyrrole nitrogen is beneficial to Oxygen and transition product *OH adsorption and stabilization), the order of activity is: pyrrole-type nitrogen > pyridine-type nitrogen > graphite-type nitrogen > nitrogen-oxygen-type nitrogen; at the same time, studies have also shown that if carbon in graphite-type nitrogen is covalently covalent with oxygen CO carbon, which has high catalytic activity, and our composition characterization also shows that our catalyst has a large amount of oxidized carbon, which determines that there is a large amount of active graphitic nitrogen, which additionally increases the active center site density of our catalyst . The catalyst shell we prepared has very high pyrrole nitrogen and very low oxide nitrogen. Therefore, the metal alloy core, the intercalated cobalt oxide at the interface or within the carbon layer, and the multilevel composition of metal-nitrogen-carbon single-multiatom active centers in this heterostructure have a high synergistic effect, and at the same time through our In the invented atmosphere high-temperature pyrolysis method, the shell layer builds a very high content of pyrrole-type nitrogen metal-NC active sites and graphite-type nitrogen catalytic active sites with an OC structure. In addition, the second element Co is added through alloying, which The high binding force with nitrogen reduces the Bader charge on Fe and reduces the OH* binding energy, which in turn can promote the reaction kinetics; these characteristics together improve the ORR catalytic activity and durability of the heterostructure electrocatalysts prepared by us. Sex (life).

Example 2

(1) Implement step 1

In the mixed metal salt solution 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.

(2) Implement step 2

Same as Example 1

(3) Implement step 3

Same as Example 1. Finally, a Co _x Fe _y @((Coz Fe _{(3-z) O 4} )-(Co/Fe-)-NC) catalyst is obtained, x: 0.001-1; y: 1-0.001; z: 0.001-3

(4) Microstructure and composition characterization of Co _x Fe _y @((Coz Fe _{(3-z) O 4} )-(Co/Fe-)-NC) nano-electrocatalytic materials

Figure 9 shows Co _x Fe _y @((Coz Fe _{(3-z) O 4} )-(Co/Fe-)-NC) catalysts prepared under different Co:Fe molar ratios (x: 0.001-1; y: 1-0.001; z: 0.001-3) microstructure characterization TEM images, the results show that regardless of the amount of Co/Fe, they can form a core-shell heterostructure similar to Co/Fe=1/1 nanomaterials ; However, when the amount of cobalt or iron is relatively low, the shell thickness of the formed core-shell structure is relatively thin, and the oxide content of the shell is obviously more. Therefore, the microstructure and composition of the shell can be regulated by the respective contents of the mixed metal salts in the reaction stock solution. Furthermore, X-photoelectron spectroscopy (XPS) was used to analyze its composition (surface layer 8nm) and element valence and coordination states. Table 1 is to include the analytical result of its element content, when Co/Fe=1/1 in the example 1, also list in the table and compare, along with the raw material cobalt salt content improves, the outer shell of the nanometer material (containing cobalt) of its construction Oxygen body and metal-NC single atomic site) also increase the cobalt content, in the catalyst under Co/Fe=1/2 and 1/1, its Co/Fe content ratio is basically the same as the raw material; however, when the Co content After exceeding iron, the cobalt content in the shell of the prepared catalyst is still much lower than that of iron, indicating that iron is more likely to be enriched than cobalt during the preparation process to build cobalt oxides (CoFe ₂ O ₄ ) and more iron-based metal-NCs in the shell. single atomic site. According to the type of N coordination, the peak position of N element characterized by XPS was fitted, and the contents of pyridine nitrogen, pyrrole nitrogen, graphitic nitrogen and NO were analyzed with the Co/Fe ratio, which are listed in Table 2. It can be seen that with the addition of cobalt, the content of pyridine nitrogen in the prepared catalyst decreases and the content of pyrrole nitrogen and graphite nitrogen increases; when Co/Fe=1/2, pyrrole nitrogen reaches the highest, which is 43.3%; while the content of nitrogen oxides in Co When /Fe=1/1, it reaches the lowest level, which is 1.7%, and the others increase with the addition of cobalt. According to the type of nitrogen coordination, it can be predicted that the comprehensive catalytic performance of Co/Fe at 1/2 and 1/1 should be relatively excellent.

(5) Characterization of electrocatalytic performance of Co ₃ Fe ₇ @(CoFe ₂ O ₄ )-(Co/Fe-)-NC) nano-electrocatalytic materials for ORR

Figure 10 shows the electrocatalysis of Co _x Fe _y @((Coz Fe _{(3-z) O 4} )-(Co/Fe-)-NC) nanometers in 0.1M KOH electrolyte using rotating disk electrode (RDE) Comparison of the linear sweep voltammetry (LSV) curves of the electrocatalytic performance of the material and commercial Pt/C on the ORR, the results show that it has a larger positive potential and a higher current density than the commercial Pt/C, the best of which is at Co/Fe=1/2, but smaller than Co/Fe=1/1. Figure 11 is the Tafel slope of the catalysts with different Co/Fe. It can be seen that the iron content or cobalt content is almost 100% and the minimum is the smallest, which is smaller than that of Pt/C, indicating that it is stronger than commercial Pt/C in the rate-limiting step. The high activity of the C catalyst; the catalyst with nearly 100% cobalt is the smallest, 61 mV/dec, indicating that the pure cobalt catalyst has the highest catalytic activity in the rate-limiting step. Fig. 12 is the Nyquist curve comparison figure of the electrochemical impedance spectrum (EIS) of the catalyst prepared by different Co/Fe ratios and Pt/C, in conjunction with the result of Fig. 6 among the embodiment 1 shows, the nanoelectrode prepared by nearly 100% raw material of cobalt content The semicircle diameter of the catalytic material is smaller than that of Co/Fe=1/1, that is, smaller than the Pt/C catalyst, which means that when the cobalt content is close to 100%, the charge transfer resistance of the nano-electrocatalytic material is lower and more favorable for the reaction transfer of electrons. Figure 13 is the chronoamperometry response of different Co/Fe catalysts tested at a voltage of 0.6V, which all have higher activity ratios than Pt/C at 36000 seconds, where Co/Fe=1/2 and almost pure cobalt They also reach 82.5% and 81.5%, respectively, but are obviously smaller than 87% of Co/Fe=1/1. Considering the electrocatalytic performance comprehensively, the electrocatalyst prepared when Co/Fe=1/1 has the best catalytic effect on ORR.

Example 3

(1) Implement step 1

In the mixed metal salt solution in step 1, we change the iron salt into other metal salts (collectively referred to as M1) respectively, and the molar content of the M1 salt has the same number of moles as the cobalt salt, that is, Co/M1=1/1, respectively prepared Mix the metal salt solution, and then prepare the electrocatalyst 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; 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. At the same time, we used the density inverse functional (DFT) combined group expansion (CE) method (DFT-CE) to study the composition, crystal phase, surface interface and subsurface atomic arrangement, and element valence of this kind of hierarchical structure catalysts. and electronic structure and electron transfer energy in different element valence states, and at the same time, based on molecular dynamics, the microstructure at all levels and reactants (such as oxygen, hydrogen), intermediate products (such as *OH) and final products (such as water) and The adsorption and desorption energies of CO and CO ₂ and the electron transfer energies under different element valence states were calculated, and M1 was screened according to the catalytic reaction thermodynamics and kinetics theory, and the best ones were selected. The results were consistent with the experiments in (5) below The test results are basically the same.

(2) Implement step 2

Same as Example 1

(3) Implement step 3

Same as Example 1. Finally obtain Co _x M1 _y @(( _Coz M1 _(2Q/n-2z/n) O _Q )-(Co/M1-)-NC) type catalyst, wherein n is the valence state of metal M1 in this catalyst, Q is the number of oxygen atoms in the formed M1 oxygen body; z is the number from 0 to Q.

(4) Microstructure and composition characterization of Co _x M1 _y @(( _Coz M1 _(2Q/n-2z/n) O _Q )-(Co/M1-)-NC) nano-electrocatalytic materials

The characterization method to microstructure and composition shows in Example 1 that Co and M1 can build nanocatalysts with the same structure, whose particle size varies from 0.5nm to 500nm, and is also a mixed oxide of alloy core, M1 and cobalt The chimeric M1/Co and nitrogen atoms are co-doped carbon shells, and M1 and cobalt work together with N to build the M1/Co-N-C active center.

(5) Electrocatalytic performance characterization of Co _x M1 _y @(( _Coz M1 _(2Q/n-2z/n) O _Q )-(Co/M1-)-NC) nano-electrocatalytic materials for ORR

The performance characterization results of the prepared Co _x M1 _y @(( _Coz M1 _(2Q/n-2z/n) O _Q )-(Co/M1-)-NC) nano-electrocatalytic materials for catalytic ORR showed that when M1 =Mn, Sn, Mo, Cr, Cu, V, W, Ce, Gd, Hg and other metals with multivalent states or not filled f orbital electrons, the catalytic performance is the best. Where M1=Mn, Cu, W, Ce, Hg, its half-wave potential can reach 0.9-1.4V, the initial voltage can reach 1.1-1.6V, and the Tafel slope can be as small as 0.60mV/dec to 0.5mV/ dec, the chronocurrent response tested under 0.6V voltage can still maintain 93%-96% at 36000 seconds.

Example 4

(1) Implement step 1

In the mixed metal salt solution in step 1, we mix the 3rd kind of metal salt (collectively referred to as M1) with the salt of cobalt and iron by the same molar content as iron and cobalt, i.e. Co/Fe/M1=1/1/1, Construction of triunit mixed metal salts. Then the electrocatalyst was prepared by the same process parameters as in Step 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; 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.

(2) Implement step 2

Same as Example 1

(3) Implement step 3

Same as Example 1. Finally, a (FeCo) _x M1 _y @(((FeCo) _z M1 _(2Q/n-2z/n) O _Q )-((Fe/Co/M1-)-NC) type catalyst is obtained, where n is the metal M1 in The valence state in the catalyst, Q is the number of oxygen atoms in the formed M1 oxygen body; z is the number from 0 to Q.

(4) Microstructure of (FeCo) _x M1 _y @(((FeCo) _z M1 _(2Q/n-2z/n) O _Q )-((Fe/Co/M1-)-NC) type nano-electrocatalytic materials and compositional characterization

The characterization method to microstructure and composition shows in Example 1 that Co and M1 can build nanocatalysts with the same structure, whose particle size varies from 0.5nm to 500nm, and is also a mixed oxide of alloy core, M1 and cobalt The chimeric M1/Co and nitrogen atoms are co-doped carbon shells, and M1 and cobalt work together with N to build the M1/Co-N-C active center.

(5)(FeCo) _x M1 _y @(((FeCo) _z M1 _(2Q/n-2z/n) O _Q )-((Fe/Co/M1-)-NC) type nano-electrocatalytic materials catalyzed ORR Electrocatalytic Performance Characterization

Nano-electrocatalysis of the prepared (FeCo) _x M1 _y @(((FeCo) _z M1 _(2Q/n-2z/n) O _Q )-((Fe/Co/M1-)-NC) type ternary metal alloy The performance characterization results of material-catalyzed ORR show that when M1=Mn, Cr, Cu, V, Hg, Ce, Gd have multi-valence states but the number of electron transfers between valence states is 1-2 or metals that are not filled with f orbital electrons , the best catalytic performance. When M1=Mn, Cu, Ce, Hg, its half-wave potential can reach 0.95-1.6V, the initial voltage can reach 1.1-1.8V, and the Tafel slope can be as small as 0.50mV/dec To 0.3mV/dec, the chronoamperometric response tested at 0.6V voltage can still maintain 94%-97% at 36000 seconds.

Example 5

(1) Implement step 1

The nitrogen ligand in the heteroatom ligand in step 1 is replaced by the ligand containing other heteroatoms to construct a mixed metal heteroatom ligand (Co-L, Fe-L and M1-L) catalyst precursors. Then the electrocatalyst was prepared by the same process parameters as in Step 1-3 of Example 1. Heteroatom ligands can be of the following types: organic complexes or nonpolar compounds of an element other than carbon, oxygen, and nitrogen in the main group elements of IIIA, IVA, VA, and VIA, such as boron (Boron), Al, Ga, Sn, N, P, As, Sb, Bi, S, Se, Te. Typical ones are: triphenylphosphorus containing phosphorus; arsenic ethoxylate containing arsenic; cystine and cysteine containing sulfur and nitrogen; selenomethionine containing selenium; bismuth isooctanoate and lauryl containing bismuth Bismuth acid, bismuth neodecanoate, bismuth naphthenate; 1-iodo-3-methylpentane containing iodine; 2-bromo-4-nitrobenzyl alcohol containing bromine, etc. We used the density inverse functional (DFT) method to study the composition of the microstructure, crystal phase, surface interface and subsurface atomic arrangement, element valence and electronic structure, and electron transfer energy at different element valence states of such hierarchical structure catalysts. Carry out calculations, especially for the electronic structure and orbital hybridization energy of metal (M) and MLC constructed with different heteroatom ligands and carbon; at the same time, according to the molecular dynamics analysis of the microstructure and reactants (such as oxygen, hydrogen ), intermediate products (such as *OH) and final products (such as water), as well as the adsorption and desorption energies of CO and CO ₂ and electron transfer energies under different element valence states, especially the active center metals and reactants such as Oxygen, hydrogen), intermediate products (such as *OH) and final products (such as water) and the adsorption and desorption energies of CO and _CO2 were calculated, and the L among them was screened according to the catalytic reaction thermodynamics and kinetics theory, and the best ones were selected. And experimental verification, the results are basically consistent with the experimental test results in (5) below.

(2) Implement step 2

Same as Example 1

(3) Implement step 3

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

(4) Microstructure of (FeCo) _x M1 _y @(((FeCo) _z M1 _(2Q/n-2z/n) O _Q )-((Fe/Co/M1-)-LC) type nano-electrocatalytic materials and compositional characterization

The characterization method for microstructure and composition in Example 1 shows that mixed metal salts and different heteroatom ligands can construct nanocatalysts with the same structure, and their particle sizes range from 0.5nm to 500nm. They are also composed of alloy cores, M1 It is composed of co-doped carbon shell with mixed oxides of cobalt and iron M1/Co/Fe and heteroatom L, M1, cobalt and iron together with L to build M1/Co/Fe-L-C active center.

(5)(FeCo) _x M1 _y @(((FeCo) _z M1 _(2Q/n-2z/n) O _Q )-((Fe/Co/M1-)-LC) nano-electrocatalytic materials catalyzed ORR Electrocatalytic Performance Characterization

Nano-electrocatalysis of prepared (FeCo) _x M1 _y @(((FeCo) _z M1 _(2Q/n-2z/n) O _Q )-((Fe/Co/M1-)-LC) type ternary metal alloy The performance characterization results of material-catalyzed ORR show that when L=P, Bi, As, Te, Se, I, there are multi-coordinated and multi-valent heteroatoms (such as phosphorus has +3 and +5 valences, and the coordination number can be up to 5; such as Te has +4 and +6 valence, the coordination number can reach 8), the catalytic activity is the best, but for high period (such as the sixth period element, the catalytic durability and stability are not too high). Among them When L=Se, Te, P, As, I, the half-wave potential can reach 1.0-1.8V, the initial voltage can reach 1.2-1.9V, and the Tafel slope can be as small as 0.40mV/dec to 0.25mV/dec , the chronocurrent response tested under 0.6V voltage can still maintain 92%-99% at 36000 seconds.

Example 6

(1) Implement step 1

In step 1, heteroatom ligands use heteroatom ligands (L) other than nitrogen ligands to construct binary heteroatom ligands in which N and L exist simultaneously, and construct a mixed metal mixture co-constructed by Co, Fe, and M1 Heteroatom ligand (Co-L, Fe-L and M1-L; Co-N and Fe-N and M1-N and Co-NL, Fe-NL and M1-NL) compound catalyst precursors. Then the electrocatalyst was prepared by the same process parameters as in Step 1-3 of Example 1. Heteroatom ligands can be of the following types: organic complexes or nonpolar compounds of an element other than carbon, oxygen, and nitrogen in the main group elements of IIIA, IVA, VA, and VIA, such as boron (Boron), Al, Ga, Sn, N, P, As, Sb, Bi, S, Se, Te. Typical ones are: triphenylphosphorus containing phosphorus; arsenic ethoxylate containing arsenic; cystine and cysteine containing sulfur and nitrogen; selenomethionine containing selenium; bismuth isooctanoate and lauryl containing bismuth Bismuth acid, bismuth neodecanoate, bismuth naphthenate; 1-iodo-3-methylpentane containing iodine; 2-bromo-4-nitrobenzyl alcohol containing bromine, etc. We used the density inverse functional (DFT) method to study the composition of the microstructure, crystal phase, surface interface and subsurface atomic arrangement, element valence and electronic structure, and electron transfer energy at different element valence states of such hierarchical structure catalysts. Carry out calculations, especially the calculation of the electronic structure and orbital hybridization energy of MLC and MNLC constructed of metal (M) and different heteroatom ligands and carbon; at the same time, according to the molecular dynamics , hydrogen), intermediate products (such as *OH) and final products (such as water), as well as the adsorption and desorption energies of CO and CO ₂ and the electron transfer energies under different element valence states were calculated, especially the active center metals in MLC and the reaction substances such as oxygen, hydrogen), intermediate products (such as *OH) and final products (such as water) and the adsorption and desorption energies of CO and _CO2 were calculated, and L was screened according to the catalytic reaction thermodynamics and kinetics theory, Selective recruitment and experimental verification, the results are basically consistent with the experimental test results in (5) below.

(2) Implement step 2

Same as Example 1

(3) Implement step 3

Same as Example 1. Finally, (FeCo) _x M1 _y @(((FeCo) _z M1 _(2Q/n-2z/n) O _Q )-((Fe/Co/M1-)-(N/L)-C) type catalyst is obtained, Wherein 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 the number from 0 to Q, L=B, Al, P, As, Bi, Sb, S, Se, Te, Br, I, etc.

(4)(FeCo) _x M1 _y @(((FeCo) _z M1 _(2Q/n-2z/n) O _Q )-((Fe/Co/M1-)-(N/L)-C) nano Microstructural and compositional characterization of electrocatalytic materials

The characterization method for microstructure and composition in Example 1 shows that mixed metal salts and different heteroatom ligands can construct nanocatalysts with the same structure, and their particle sizes range from 0.5nm to 500nm. They are also composed of alloy cores, M1 It is composed of co-doped carbon shells co-doped with cobalt and iron mixed oxides M1/Co/Fe and heteroatoms N and L, and M1 and cobalt and iron work together with L to build M1/Co/Fe-N/L-C active centers.

(5)(FeCo) _x M1 _y @(((FeCo) _z M1 _(2Q/n-2z/n) O _Q )-((Fe/Co/M1-)-(N/L)-C) nano Characterization of electrocatalytic performance of electrocatalytic materials for ORR

For the prepared (FeCo) _x M1 _y @(((FeCo) _z M1 _(2Q/n-2z/n) O _Q )-((Fe/Co/M1-)-(N/L)-C) type three The performance characterization results of ORR catalyzed by metal alloy nano-electrocatalytic materials show that when L=Bi, As, Te, I, heteroatoms with multi-coordination and multi-valence states (such as phosphorus with +3 and +5 valences, coordination The number can reach 5; if Te has +4 and +6 valence, the coordination number can reach 8), the catalytic activity is the best, but for high period (such as the sixth period element, the catalytic durability and stability are not too high) When L=Te, As, I, its half-wave potential can reach 1.0-1.9V, the initial voltage can reach 1.2-2.0V, and the Tafel slope can be as small as 0.40mV/dec to 0.20mV/dec, 0.6 The chronoamperometric response tested under V voltage can still maintain 96%-99.9% at 36000 seconds.

The test results of the full battery test stack constructed by it show that the calculated volume activity can reach 300-1000A/cm ³ , which is equal to or far exceeds the 300A/cm ³ standard of the US Department of Energy. Its repeated use times have also been tested, and it can be used repeatedly for more than 1000 times and the activity persistence can still maintain more than 80-95%.

Example 7

(1) Implement step 1

Same as Example 6

(2) Implement step 2

The nitrogen-modified porous carbon black used in the preparation step of the heteroatom-doped/modified porous carrier (about 10-200 nm in diameter)+heteroatom ligand suspension in step 2 of Example 6 was replaced by the following multi-component hetero Atom-ligand modified molecular sieves (such as ZIF-8). Taking N,P modified ZIF-8 as an example, the specific modification steps are as follows. Dissolve the nitrogen ligand such as 0.2g phenanthroline (or porphyrin, or imidazole, or purine, or pyrimidine) and 1.0g ZIF-8 in a mixed solvent constructed from 15ml deionized water and 110mL ethanol, mix 0.5- After 2 hours, carry out the ZIF-8 that spray drying process obtains nitrogen ligand surface coating; Then the ZIF-8 (about 1.2g) of the nitrogen ligand surface coating that obtains and 0.3 gram phosphorus ligand (triphenylphosphorous (Ph3P), or triphenoxyphosphorus (Ph3P=O), or triphenylamidophosphorus (Ph3P ₌ NH)) was dissolved in diethyl ether and mixed for 0.5-2 hours, and obtained N ligand and P ligand surface modified ZIF-8 for later use; finally in a tube furnace at 400-1000°C, in an inert atmosphere (nitrogen, flow rate 5-40sccm) for 0.5-2 hours, lower the temperature to obtain the required N, P modified sex ZIF-8. If it is necessary to obtain Se or Te and N, P co-modified ZIF-8, after obtaining N ligand and P ligand surface modified ZIF-8, add 0.2g of selenomethionine or tellurium compound (such as strontium tellurate) To the mixture of ethanol and water, after thorough mixing and spray drying, heat treatment in a tube furnace inert atmosphere for 0.5-2 hours to construct N, P, Se or N, P, Te modified ZIF-8. Then in the subsequent preparation, ZIF-8 modified by different multi-component heteroatom ligands was used instead of N-modified porous carbon as the carrier used in this step, such as N,P-ZIF-8; N,Se-ZiF -8; P, Te-ZIF-8.

(3) Implement step 3

Same as Example 6. Finally, (FeCo) _x M1 _y @(((FeCo) _z M1 _(2Q/n-2z/n) O _Q )-((Fe/Co/M1-)-(L)-ZIF-8) type catalyst is obtained, Wherein 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 the number from 0 to Q, L=B, Al, P, As, Bi, Sb, S, Two or more of Se, Te, Br, I, etc.

(4)(FeCo) _x M1 _y @(((FeCo) _z M1 _(2Q/n-2z/n) O _Q )-((Fe/Co/M1-)-(L)-ZIF-8) nano Microstructural and compositional characterization of electrocatalytic materials

The characterization method for microstructure and composition in Example 6 shows that mixed metal salts and different heteroatom ligands can build nanocatalysts with the same structure, and their particle sizes range from 0.5nm to 500nm. They are also composed of alloy cores, M1 It is composed of co-doped ZIF-8 co-doped with cobalt and iron mixed oxide M1/Co/Fe and multi-element heteroatom L, and M1 and cobalt and iron are used together with L to construct M1/Co/Fe-(L)-(Si/ Al) active center.

(5)(FeCo) _x M1 _y @(((FeCo) _z M1 _(2Q/n-2z/n) O _Q )-((Fe/Co/M1-)-(L)-ZIF-8) nano Characterization of electrocatalytic performance of electrocatalytic materials for ORR

For the prepared multi-heteroatom modified ZIF-8 supported (FeCo) _x M1 _y @(((FeCo) _z M1 _(2Q/n-2z/n) O _Q )-((Fe/Co/M1-)-( The performance characterization results of L)-ZIF-8) type ternary metal alloy nano-electrocatalytic materials for catalytic ORR show that when L=N, P, Te, Sb, S, there are heteroatoms with multi-coordination and multi-valence states (such as Phosphorus has +3 and +5 valences, and the coordination number can reach 5; as Te has +4 and +6 valences, and the coordination number can reach 8), the catalytic activity is the best, and the activity persistence is also good. Wherein L=Te , As, and I, its half-wave potential can reach 1.0-2.0V, the initial voltage can reach 1.2-2.3V, and the Tafel slope can be as small as 0.35mV/dec to 0.20mV/dec, tested at 0.6V voltage The chronocurrent response can still be maintained at 97%-99.9% at 36000 seconds.

The test results of the full battery test stack constructed by it show that the calculated volume activity can reach 400-1200A/cm ³ , exceeding the 300A/cm ³ standard announced by the US Department of Energy in 2015. Its repeated use times have also been tested, and it can be used repeatedly for more than 1000 times and the activity persistence can still maintain more than 84-95%.

Example 8

(1) Implement step 1

Same as Example 6

(2) Implement step 2

Replace the nitrogen-modified porous carbon black used in the preparation step of the heteroatom-doped/modified porous carrier (about 10-200nm in diameter) + heteroatom ligand suspension in step 2 of Example 6 with phosphotungstic acid Cesium (Cs-TPA) or bismuth phosphotungstate (Bi-TPA) surface-modified MCM-41, its preparation method is as follows. The preparation process of cesium phosphotungstate is as follows: Use the equal volume impregnation method to carry out Cs ₂ CO ₃ surface modification on 1 gram of MCM-41 purchased, that is, drop a saturated aqueous solution of Cs ₂ CO ₃ (261g/100mL) into 1 gram of MCM-41 drop by drop. 41 to reach saturated humidity; then dry at 110°C, and then anneal at 500°C under nitrogen protection for two hours to obtain Cs-MCM-41; then crush the sample and use phosphorus concentration of 1g/mL Tungstic acid (TPA) butanol solution was dropped into the prepared Cs-MCM-41 powder drop by drop to reach the saturation wetness, then dried at 110°C, and then annealed at 300°C in air for two hours to obtain Cs -TPA-MCM-41. Then use this as the porous carrier instead of N-modified porous carbon as the carrier used in this step to carry out the preparation process of step 2 and step 3.

(3) Implement step 3

Same as Example 6. Finally, (FeCo) _x M1 _y @(((FeCo) _z M1 _(2Q/n-2z/n) O _Q )-((Fe/Co/M1-)-(L)- (Cs-TPA-MCM- 41)) type catalyst, wherein n is the valence state of metal M1 in the catalyst, Q is the number of oxygen atoms in the formed M1 oxygen body; z is the number from 0 to Q, L=B, Al, P, As, Two or more of Bi, Sb, S, Se, Te, Br, I, etc.

(4)(FeCo) _x M1 _y @((((FeCo) _z M1 _(2Q/n-2z/n) O _Q )-((Fe/Co/M1-)-(L)-(Cs-TPA-MCM Microstructure and composition characterization of -41)) type nano-electrocatalytic materials

The characterization method for microstructure and composition in Example 6 shows that mixed metal salts and different heteroatom ligands can build nanocatalysts with the same structure, and their particle sizes range from 0.5nm to 500nm. They are also composed of alloy cores, M1 It is composed of co-doped Cs-TPA-MCM-41 with mixed oxides of cobalt and iron M1/Co/Fe and multi-element heteroatoms L, and M1 and cobalt and iron together with L to construct M1/Co/Fe-(L) -P, M1/Co/Fe-(L)-Cs, M1/Co/Fe-(L)-Si, M1/Co/Fe-(L)-W various types of catalytic active centers.

(5)(FeCo) _x M1 _y @(((FeCo) _z M1 _(2Q/n-2z/n) O _Q )-((Fe/Co/M1-)-(L)-(Cs-TPA-MCM Characterization of electrocatalytic performance of -41)) type nano-electrocatalytic materials for ORR

The prepared multi-heteroatom modified Cs-TPA-MCM-41 loaded with (FeCo) _x M1 _y @(((FeCo) _z M1 _(2Q/n-2z/n) O _Q )-((Fe/Co/M1 -)-(L)-(Cs-TPA-MCM-41)) type ternary metal alloy nano-electrocatalytic material catalyzed ORR performance characterization results show that when L=N, P, As, Sb, Bi, Se, I When heteroatoms with multi-coordination and multi-valence state (such as phosphorus has +3 and +5 valence, the coordination number can reach 8; such as Se has +4 and +6 valence, the coordination number can reach 8), the catalytic The activity is the best, and the activity persistence is also good. When L=P, Sb, Bi, its half-wave potential can reach 1.0-2.2V, the initial voltage can reach 1.2-2.5V, and the Tafel slope can be as small as 0.35mV /dec to 0.15mV/dec, the chronoamperometric response tested at 0.6V voltage can still maintain 96%-99.9% at 36000 seconds.

The test results of the full battery test stack constructed by it show that the calculated volume activity can reach 500-1500A/cm ³ , far exceeding the 300A/cm ³ standard announced by the US Department of Energy in 2015. Its repeated use times have also been tested, and it can be used repeatedly for more than 1500 times and the activity persistence can still maintain more than 90-98%.

Example 9

(1) Implement step 1

Same as Example 5.

(2) Implement step 2

Same as Example 5.

(3) Implement step 3

The preparation of the heteroatom compound atmosphere for pyrolysis in step 3 is by placing the solid heteroatom ligand in a container with a vent at the heating section I in step 3, and controlling the heating temperature of this section to exceed the boiling point or sublimation point of the compound . An inert carrier gas (argon gas is used here) passes through the heating vaporization section to form an atmosphere carrier gas for cracking containing a heteroatom atmosphere. The solid heteroatom ligands here are iodine, triphenylbismuth, diphenyldiselenide and cerium dodecaiododecaborate, the dosage is 0.1-2g; the temperature at heating section I is controlled at 190°C and 320°C respectively , 390°C and 680°C.

Finally, (FeCo) _x M1 _y @(((FeCo) _z M1 _(2Q/n-2z/n) O _Q )-((Fe/Co/M1-)-LC) type catalyst, where n is the valence state of metal M1 in this catalyst, Q is the formed M1 oxygen body The number of oxygen atoms in; z is the number from 0 to Q, L=B, Al, P, As, Bi, Sb, S, Se, Te, Br, I.

(4) Microstructure of (FeCo) _x M1 _y @(((FeCo) _z M1 _(2Q/n-2z/n) O _Q )-((Fe/Co/M1-)-LC) type nano-electrocatalytic materials and compositional characterization

The characterization method for microstructure and composition in Example 1 shows that mixed metal salts and different heteroatom ligands can construct nanocatalysts with the same structure, and their particle sizes range from 0.5nm to 500nm. They are also composed of alloy cores, M1 It is composed of co-doped carbon shell with mixed oxides of cobalt and iron M1/Co/Fe and heteroatom L, M1, cobalt and iron together with L to build M1/Co/Fe-L-C active center. For example, if the heteroatom is iodine (I), bismuth (Bi), selenium (Se), and iodine-cerium-boron (I-Ce-B), the overall doping amount increases by 50%, 20%, 40%, and 70% respectively. -100% -20%.

(5)(FeCo) _x M1 _y @(((FeCo) _z M1 _(2Q/n-2z/n) O _Q )-((Fe/Co/M1-)-LC) nano-electrocatalytic materials catalyzed ORR Electrocatalytic Performance Characterization

Nano-electrocatalysis of prepared (FeCo) _x M1 _y @(((FeCo) _z M1 _(2Q/n-2z/n) O _Q )-((Fe/Co/M1-)-LC) type ternary metal alloy The performance characterization results of material-catalyzed ORR show that when L=I, Bi, Se, and I-Ce-B, there are multi-coordination and multi-valence heteroatoms, the catalytic activity can be greatly improved, and its half-wave potential can reach 1.3, 1.4, 1.5, 2.0V, the initial voltage can reach 1.3, 1.8, 1.6, 2.1V, the Tafel slope can be as small as 0.35mV/dec, 0.30mV/dec, 0.26mV/dec, 0.24mV/dec, The chronocurrent response tested under 0.6V voltage can still maintain 95%, 98%, 94%, 99% at 36000 seconds.

Table 1 shows the atomic percentages of each element in the heterostructure catalysts prepared under different ratios of Co/Fe according to the XPS test.

Table 2 The ratio of N species content in heterostructure catalysts prepared under different ratios of Co/Fe obtained by N1s peak fitting.

Claims (10)

1. Porous carrier supported metal Alloy (AB) @ metal oxide (ABO) _x ) Nano electro-catalytic material (AB @ (ABO)) with inlay metal (A/B) and heteroatom (L) co-doped shell (C) heterostructure _x ) A process for the preparation of- (A/B-) -L-C), characterized in that it comprises the following steps:

(1) Slightly colloidizing by ultrasonic atomization, forming aqueous alkali into micro-droplets by ultrasonic atomization, dropping the micro-droplets into a mixed metal salt solution containing a dispersing agent to construct a multi-polyhydroxy metal mixture sol, centrifuging the sol by a centrifuge, and washing the sol by distilled water for several times for later use; the metal at least comprises a metal A and a metal B;

(2) Preparing multi-element metal-heteroatom complex gel by sol-gel phase conversion, mixing the cleaned multi-element polyhydroxy metal mixture sol with a porous carrier and a ligand containing heteroatom L, adding the mixture into a solvent, uniformly mixing, carrying out a displacement reaction on the ligand heteroatom and hydroxyl or/and a complex reaction with metal to gelatinize the multi-element polyhydroxy metal sol to form metal-heteroatom complex microgel loaded on the porous carrier, centrifuging to form slurry, cleaning, and drying to form powder by using an organic solvent spray dryer;

(3) Preparing metal alloy core-metal oxide mosaic heteroatom doped shell electrocatalyst by pyrolysis, placing powder on a watch glass in a quartz tube furnace, uniformly spreading, and calcining in different atmosphere ranges to obtain metal Alloy (AB) @ metal oxide (ABO) _x ) Mosaic metal (A/B) and heteroatom (L) co-doped shell (C) heterostructure nano electro-catalytic material (AB @ ((ABO) _x )-(A/B-)-L-C)。

2. A metal Alloy (AB) @ metal oxide (ABO) according to claim 1 _x ) Nano electro-catalytic material (AB @ (ABO)) with inlay metal (A/B) and heteroatom (L) co-doped shell (C) heterostructure _x ) The preparation method of- (A/B-) -L-C) is characterized in that the metal A and the metal B in the step (1) are both selected from the fourth and the fifthAnd transition metals of the sixth period, 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 and In of IIIA; ge, sn, pb of IVA; sb and Bi of VA; the metal A and the metal B are different, and the metal A and the metal B are single metal or a plurality of metals; the ratio of the metal A and the metal B is not limited, and is adjusted according to the need, such as a molar ratio of 10.

3. A metal Alloy (AB) @ metal oxide (ABO) according to claim 1 _x ) Nano electrocatalytic material (AB @ (ABO)) with mosaic metal (A/B) and heteroatom (L) co-doped shell layer (C) heterostructure _x ) A method for preparing- (A/B-) -L-C), characterized in that the metal salt is halide, sulfate, nitrate, perhalogenate, phosphate and other water-soluble metal salts, and the concentration range is 0.01M to 1M; the alkaline solution is alkali metal (LiOH, naOH, KOH, ruOH)), alkaline earth metal (such as Be (OH) ₂ 、Ca(OH) ₂ ) Sodium borohydride or a solution of an organic strong base (e.g. ammonia, hydrazine hydrate, ethylenediamine) at a concentration of 0.01M to 1M.

4. A metal Alloy (AB) @ metal oxide (ABO) according to claim 1 _x ) Nano electrocatalytic material (AB @ (ABO)) with mosaic metal (A/B) and heteroatom (L) co-doped shell layer (C) heterostructure _x ) The preparation method of- (A/B-) -L-C) is characterized in that the carrier in the step (2) is selected from porous active carbon black, graphene oxide sheets, carbon nano tubes, modified molecular sieves (such as imidazole modified ZIF-8), porous hydroxyapatite, cerium phosphotungstate modified nanoporous silica (MCM-41 @ Cs-TPA), and cerium phosphotungstate modified nanoporous alumina (Al-41 @ Cs-TPA) ₂ O ₃ @ Cs-TPA), cerium phosphotungstate modified nanoporous titanium oxide (TiO) ₂ @ Cs-TPA), etc., or other modified supports, at a concentration of 0.1g/L to 500g/L; the heteroatom L of the carbon shell doped with the heteroatom L in the step (2) is selected from one or more than one element except carbon and oxygen in main group elements of IIIA, IVA, VA and VIA, such As Boron (Boron), al, ga, sn, N, P, as, sb, bi, S,Se and Te, and the doping mode is construction; the molar ratio of the ligand containing the heteroatom L to the metal is not limited, such as 1; the concentration of the ligand containing heteroatom L is 0.1g/L to 200g/L.

5. A metal Alloy (AB) @ metal oxide (ABO) according to claim 1 _x ) Nano electrocatalytic material (AB @ (ABO)) with mosaic metal (A/B) and heteroatom (L) co-doped shell layer (C) heterostructure _x ) The preparation method of- (A/B-) -L-C) is characterized in that a Y-shaped micro-channel mixer is adopted when the multi-component polyhydroxy metal mixture sol, the porous carrier and the ligand containing the heteroatom L in the step (2) are mixed and reacted.

6. A metal Alloy (AB) @ metal oxide (ABO) according to claim 1 _x ) Nano electro-catalytic material (AB @ (ABO)) with inlay metal (A/B) and heteroatom (L) co-doped shell (C) heterostructure _x ) A process for the preparation of (A/B-) -L-C), characterized in that the heteroatom L-containing ligand is selected, for example, from the group consisting of phenanthrolines, purines, pyrimidines, amino acids, polyaminoacids, triphenylphosphine, selenomethionine, triphenylarsine, polyboranes (e.g.spherical lithium decadibromododecaborate Li) ₂ (B ₁₂ Br ₁₂ ) Cerium dodecaiodododecaborate Ce (B) ₁₂ I ₁₂ ) ₂ Cesium dodecahydrododecaborate Cs ₂ (B ₁₂ H ₁₂ ) One or more of bismuth alkoxide, selenium alkoxide, sulfur alkoxide, etc.

7. A metal Alloy (AB) @ metal oxide (ABO) according to claim 1 _x ) Nano electrocatalytic material (AB @ (ABO)) with mosaic metal (A/B) and heteroatom (L) co-doped shell layer (C) heterostructure _x ) The preparation method of- (A/B-) -L-C) is characterized in that the solvent is a solvent capable of dissolving the metal hydroxide sol and the heteroatom ligand, such as ethanol, diethyl ether, acetone, benzene and the like.

8. A metal Alloy (AB) @ metal oxide (ABO) according to claim 1 _x ) Damascene metal (A/B) and heteroatom (L) co-dopingShell layer (C) heterostructure nano electro-catalytic material (AB @ (ABO) _x ) The preparation method of- (A/B-) -L-C) is characterized in that different atmospheres in the step (3) are inert atmospheres or/and the atmosphere of a precursor of a heteroatom element to be doped, the atmosphere of the precursor of the heteroatom element to be doped is selected from ammonia gas, imidazole, phosphine, borane, sulfur vapor, sulfur dioxide vapor, selenium dioxide vapor and the like, and the content is 5-20V%; if the room temperature is the atmosphere corresponding to the solid substance, the metal-heteroatom complex microgel of the solid substance is placed in a tubular furnace and is loaded before a porous carrier is heated, the heating temperature is controlled to be above or below the boiling point or sublimation point, the evaporation capacity is controlled by the temperature, and the solid substance enters a reaction system by inert carrier gas; the whole flow of the atmosphere gas is 5-40sccm; the doped heteroatom in the step (3) can be the same as or different from that in the step (2), the doping amount can be further increased when the doped heteroatom is the same as that in the step (2), and new doping elements can be further introduced when the doped heteroatom is different from that in the step (2); the calcining temperature is controlled between 400 ℃ and 1400 ℃, the temperature is kept for 0.5-4 hours, and then the material is cooled and discharged.

9. A metal Alloy (AB) @ metal oxide (ABO) according to claim 1 _x ) Nano electrocatalytic material (AB @ (ABO)) with mosaic metal (A/B) and heteroatom (L) co-doped shell layer (C) heterostructure _x ) The preparation method of- (A/B-) -L-C) is characterized in that the structure of the obtained material is as follows: the metal alloy AB is an internal core, and the metal oxide ABOx is embedded in carbon (mostly in a graphite carbon structure) co-doped with metal and heteroatom L and is taken as a shell layer C to form a heterostructure; the heterostructure is loaded on a porous carrier to form a nano electro-catalytic material, and the heterostructure metal-heteroatom co-doped carbon electro-catalytic material with a loading type using metal alloy as a core and metal oxide embedded in a metal-heteroatom co-doped carbon layer (mostly in a graphite structure) as a shell obtains a novel heterostructure nano electro-catalytic material (AB @ (ABOx) - (A/B-) -L-C) with metal alloy as a core and metal oxide embedded in metal and heteroatom co-doped carbon as a shell.

10. Preparation according to the process of any one of claims 1 to 9The obtained nano electro-catalytic material (AB @ (ABO) _x ) Use of- (A/B-) -L-C) as electrocatalytic material for electrocatalytic redox reactions.

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