CN107803207B

CN107803207B - Carbon-based bimetallic composite material, preparation and application thereof

Info

Publication number: CN107803207B
Application number: CN201710973860.7A
Authority: CN
Inventors: 方静; 甘浪; 覃富荣; 王梦然; 赖延清; 李劼
Original assignee: Central South University
Current assignee: Central South University
Priority date: 2017-10-18
Filing date: 2017-10-18
Publication date: 2020-06-12
Anticipated expiration: 2037-10-18
Also published as: CN107803207A

Abstract

The invention discloses a carbon-based bimetal composite material, which comprises a carbon-based shell, wherein the inner surface of the carbon-based shell is compounded with a sulfide of a transition metal A, and the outer surface of the carbon-based shell is compounded with an oxide of a transition metal B; the transition metals A and B are selected from different metals. The invention also discloses a preparation method of the carbon-based bimetallic composite material, which comprises the steps of carrying out hydrothermal reaction on a mixed solution containing a salt of a transition metal A, a salt of a transition metal B, an organic ligand and alcohol at the temperature of 60-180 ℃ to obtain bimetallic MOF; and mixing the obtained bimetallic MOF with sublimed sulfur, and roasting at 300-800 ℃ in a protective atmosphere to obtain the carbon-based bimetallic composite material. In addition, the invention also comprises the application of the composite material as an OER electrocatalyst. The invention provides an electrocatalyst with a brand-new structure; the material has excellent OER catalytic performance. At a current density of 10mA/cm²The oxygen evolution potential can approach 0.55V; at an overpotential of 320mV, TOF can be as high as 34.7s^‑1。

Description

Carbon-based bimetallic composite material, preparation and application thereof

Technical Field

The invention relates to a novel carbon-based bimetallic composite double-shell hollow structure electrocatalyst, belonging to the field of energy sources and catalytic materials.

Background

In recent years, the problems of energy crisis and environmental pollution are increasingly prominent, and the development of renewable energy and clean energy is imminent. The electrochemical decomposition water has attracted extensive attention because of its environmental protection, high product purity and no greenhouse gas emission. Effective water electrolysis catalysts require low overpotentials for both anodic Oxygen Evolution (OER) and cathodic Hydrogen Evolution (HER) reactions, but the efficiency of the electrocatalyst is driven by slow OER kineticsMechanical and high overpotential limitations, therefore improving the electrocatalyst efficiency of OER is critical for water splitting. Generally considered as RuO₂And IrO₂Considered the best OER electrocatalysts, unfortunately their large-scale commercial use is hampered by high cost, poor durability and scarce supply. Therefore, designing a catalyst with simple preparation method, low cost, low overpotential and high stability becomes a research hotspot of the current research team.

The Metal Organic Frameworks (MOFs) are a new nano porous material, and have huge application potential in the fields of catalysis, energy storage, solar energy collection and the like due to the high specific surface area, uniform and adjustable pore channels, easy functionalization and adjustment and good chemical and thermal stability. In recent years, metal oxides, phosphides, sulfides, selenides, nitrides, and the like derived from transition metals MOFs (such as Fe, Co, Ni, and the like) have attracted a high degree of attention from most research teams due to their excellent catalytic properties.

Zhou et al with 4- [ (phosphonoethylamino) -methyl]Benzoic acid is taken as a ligand material, a Co-MOF precursor is prepared by a hydrothermal method, and a cobalt phosphorus carbon compound (Co-PC) with a layered structure is synthesized by high-temperature calcination, and the catalyst has the advantages of low overpotential, high limiting current density and the like, and has a good application prospect in the field of metal-air batteries (ACSCatalysis,2017,7: 6000-. Chinese patent CN104056630A discloses a method for preparing carbon-coated cobalt simple substance by mixing a carbon source and cobalt salt according to a certain proportion and calcining at high temperature, the catalyst has the advantages of uniform particle diameter, good conductivity, high electrocatalytic performance and the like, and has good application prospect in the fields of metal-air batteries, electrocatalytic water oxygen generation and the like. Chinese patent CN104659357A discloses a method for preparing a supported nickel-iron composite hydroxide oxygen evolution electrode by simply physically mixing and rolling a nickel-iron salt solution, a conductive carrier and an adhesive to obtain a metal salt/carbon film, and then carrying out low-temperature heat treatment, in-situ precipitation and pressing on a metal current collector. Chinese patent CN105176528A discloses a method for preparing cobalt nitrate hexahydrate, urea and ammonium fluorideThe method comprises the following steps of growing basic cobalt carbonate nanowires on carbon fiber paper through a solvothermal reaction, adding sulfur powder as a raw material, preparing a carbon fiber paper loaded cobalt sulfide nanowire composite structure through a low-temperature vulcanization reaction, and finally electroplating a cobalt hydroxide nanosheet on the surface of the carbon fiber paper loaded cobalt sulfide nanowire composite structure by using an electrochemical deposition method to obtain the cobalt-based multistage nano composite structure electrolyzed water oxygen-generating electrocatalyst, wherein the catalyst has the advantages of low oxygen evolution overpotential, high electrocatalytic performance and the like, and is relatively noble metal, low in cost and good in industrial application prospect. Chinese patent CN105176528A discloses a method for preparing Ni by using nickel acetate, ferric chloride, citric acid and sulfur as raw materials, uniformly mixing the raw materials according to a certain mole percentage, and then calcining the mixture at high temperature_0.9Fe_0.1@CN_xThe catalyst has the advantages of nano-tube shape, porosity, large specific surface area and the like, and promotes the oxygen evolution electrode material to be used for large-scale production of electrolyzed water.

Most of the electrocatalysts prepared by the method are not applied to the anodic oxygen evolution reaction of the electrolyzed water, and the preparation methods of part of the catalysts are complex, and the preparation process conditions are not easy to control, so that the multi-shell hollow carbon spheres which are low in development cost, free of precious metals and high in electrocatalytic activity and stability are used as OER electrocatalysts, and have great significance for promoting the commercialization process of oxygen preparation by electrolyzing water.

Disclosure of Invention

In order to solve the technical problems in the prior art, the invention provides a carbon-based bimetallic composite material with a brand new structure; the material is used as an OER electrocatalyst and has good catalytic performance.

The second purpose of the invention is to provide a preparation method of the carbon-based bimetallic composite material.

The third purpose of the invention is to provide the application of the carbon-based bimetallic composite material.

A carbon-based bimetal composite material comprises a carbon-based shell, wherein the inner surface of the carbon-based shell is compounded with a sulfide of a transition metal A, and the outer surface of the carbon-based shell is compounded with an oxide of a transition metal B; the transition metals A and B are selected from different metals.

Preferably, the transition metal A is at least one selected from Co and Zn; more preferably, Co is used. When the transition metal A is preferably Co, the prepared hollow structure is more uniform, and the catalytic oxygen evolution performance is more excellent.

Preferably, the transition metal B is at least one selected from Fe, Ni, Cu, Zn and Mn; further preferably Fe. When the transition metal B is preferably Fe, the catalytic oxygen evolution performance is better.

Preferably, the carbon-based shell is doped with a hetero element, and the hetero atom is at least one of N, S.

Preferably, the end of the carbon-based shell close to the inner surface is infiltrated with sulfide of the transition metal A; the oxide of the transition metal B is infiltrated near the outer surface end. That is, the sulfide part of the transition metal A permeates into the interior of the carbon-based shell; the oxide of the transition metal B also partially permeates into the interior of the carbon-based shell.

Preferably, the carbon-based bimetallic composite material is spherical or spheroidal. For example, the composite material is a sphere; or materials with the shapes of ellipsoid and the like. The research shows that the OER catalytic performance is better due to the preferable morphology and the structural material.

Preferably, the composite material comprises a spherical or sphere-like carbon-based shell; the inner surface of the carbon-based shell is compounded with a cobalt sulfide layer, and the outer surface of the carbon-based shell is compounded with iron oxide.

In the composite material, the content of sulfide of the transition metal A is 5-25%; the content of the oxide of the transition metal B is 1-15%; the content of the carbon-based shell is 60-94%.

The invention also discloses a preparation method of the carbon-based bimetallic composite material, which comprises the steps of carrying out hydrothermal reaction on a mixed solution containing a salt of a transition metal A, a salt of a transition metal B, an organic ligand and alcohol at the temperature of 60-180 ℃ to obtain bimetallic MOF; and mixing the obtained bimetallic MOF with sublimed sulfur, and roasting at 300-800 ℃ in a protective atmosphere to obtain the carbon-based bimetallic composite material.

According to the preparation method, the two transition metals are subjected to hydrothermal reaction in an alcohol solvent atmosphere at the temperature, so that the bimetallic MOF with a special hollow appearance can be prepared; then the bimetallic MOF with the morphology is mixed with sublimed sulfur creatively, and roasting is carried out at the temperature; the composite material with the unique morphology can be prepared; the whole material is of a carbon shell structure, the outer surface of the material is compounded with transition metal oxide, and the inner surface of the material is compounded with transition metal sulfide; the material with the morphology is proved to have excellent OER catalytic performance.

The key point of the preparation method is that double transition metals and hydrothermal conditions (such as hydrothermal temperature and hydrothermal alcohol solvent atmosphere) are adopted; and roasting the obtained MOF and sulfur together at the temperature.

Preferably, the alcohol is C1-4 monoalcohol or polyalcohol. The alcohol is preferably an anhydrous solvent. Such as methanol, ethanol, propanol, etc.

More preferably, the alcohol is methanol.

In the invention, the organic ligand is at least one of dimethyl imidazole, terephthalic acid and pyridine.

More preferably, the organic ligand is dimethyl imidazole. Researches show that the ligand is matched with the hydrothermal reaction condition to finally prepare the composite material with spherical and hollow morphology, and the OER catalytic performance of the material with the structure is more excellent.

Preferably, the salt of transition metal A may be Co²⁺、Zn²⁺Examples of the water-soluble salt of (2) include chloride, nitrate, and sulfate.

Preferably, the salt of the transition metal B is Fe³⁺、Ni²⁺、Cu²⁺、Zn²⁺、Mn²⁺Examples of the water-soluble salt of (2) include chloride, nitrate, and sulfate.

Preferably, the molar ratio between the transition metals a and B is 5: 1-1: 2.

further preferably, the molar ratio of the transition metals A and B is 3: 1-4: 1.

the sum of the molar amount of organic ligand and the molar amount of transition metal A, B is greater than or equal to 2.

Preferably, the ratio of the molar amount of the organic ligand to the sum of the molar amount of the transition metal A, B is 2 to 8 times; more preferably 2 to 4.

Preferably, the salt of the transition metal A, the salt of the transition metal B and the organic ligand in the proportion are respectively dispersed and/or dissolved by the alcohol in an ultrasonic mode; respectively obtaining a transition metal A solution, a transition metal B solution and an organic ligand solution; then dropwise adding the transition metal A solution into the organic ligand solution, and dropwise adding the transition metal B solution after ultrasonic dispersion; continuing to perform ultrasonic dispersion, and then performing subsequent hydrothermal reaction.

The time of ultrasonic treatment at each stage is not particularly required, so that the solution forms uniformly dispersed suspension; the preferable ultrasonic time is 0.1-0.5 h.

The concentration of the solute in the transition metal A solution is not particularly required, and is preferably 1 to 30 mg/mL.

The concentration of the solute in the transition metal B solution is not particularly required, and is preferably 1 to 30 mg/mL.

The dropping speed of the transition metal A solution and the transition metal B solution is 2-10 mL/min.

In the invention, the preferable hydrothermal reaction temperature is 80-160 ℃, and preferably, the shape of the product is kept more complete and uniform at the temperature.

Further preferably, the hydrothermal reaction temperature is 120 to 140 ℃. Under the preferable range, the prepared bimetallic MOF has better appearance, and the OER catalytic performance of the composite material obtained by subsequent roasting is more excellent.

Carrying out hydrothermal reaction in a closed container; under the hydrothermal reaction condition, the preferable hydrothermal reaction time is 1-12 h.

And carrying out solid-liquid separation after the hydrothermal reaction, and then washing and drying to obtain the bimetallic MOF. The washing process comprises the following steps: and (3) alternately cleaning with water and ethanol, centrifuging for several times until the supernatant is clear, and then drying for 6-8 hours in vacuum at 50-80 ℃ to obtain the precursor of the bimetallic MOF.

The obtained bimetallic MOF is mixed with sublimed sulfur and then is roasted, and the mixing mode can adopt the existing method, such as ball milling.

The preferable mass ratio of the bimetallic MOF to the sublimed sulfur is 1-4; further preferably 1: 1.

The roasting process is carried out in a protective atmosphere; the protective atmosphere is nitrogen or inert gas.

The temperature rise rate in the roasting process is 1-10 ℃/min; preferably 2 to 8 ℃/min.

The preferable roasting temperature is 300-800 ℃. Within this preferred range, the catalytic oxygen evolution performance is further improved.

More preferably, the baking temperature is 500 to 600 ℃.

Under the roasting condition, the preferable roasting time is 1-12 h; more preferably 3 to 6 hours.

Ultrasonically washing the roasted product for 0.5-2 hours by using the alcohol, alternately cleaning the product by using water and ethanol, centrifuging the product for several times until the supernatant is clear, and then drying the product for 6-8 hours in vacuum at the temperature of 50-80 ℃ to obtain the composite material.

The invention also discloses application of the carbon-based bimetallic composite material as a catalyst for catalyzing alkaline electrolysis water oxygen generation reaction.

The invention uses transition metal salt and imidazole compound as raw materials, and obtains the novel carbon-based bimetallic composite double-shell hollow structure electrocatalyst by an ultrasonic-assisted method and high-temperature heat treatment. The catalyst is applied to oxygen production by electrolyzing water, and shows commercial RuO under alkaline condition₂Comparable OER electrocatalytic activity.

The invention discloses a preferable preparation method, which comprises the following steps:

a. weighing 120 parts by weight of transition metal salt, dispersing in 30 parts by weight of alcoholic solution, and carrying out ultrasonic treatment in an ultrasonic device for 0.2-0.5 hour to completely disperse the transition metal salt in the alcoholic solution;

b. adding 400 parts by weight of imidazole compound into the mixture, continuing to perform ultrasonic treatment for 0.2-0.5 hour to uniformly mix the imidazole compound and the transition metal salt in the solution, continuing to add 40 parts by weight of another transition metal salt, and continuing to perform ultrasonic treatment for 0.2-0.5 hour;

c. then transferring the mixture into a high-pressure reaction kettle for treatment for 1-6 hours at the temperature of 80-160 ℃, naturally cooling, alternately cleaning with water and ethanol, centrifuging for several times until the supernatant is clear, and then carrying out vacuum drying for 6-8 hours at the temperature of 50-80 ℃ to obtain a bimetallic MOF precursor;

d. uniformly grinding 100 parts by weight of bimetallic MOF and 100 parts by weight of sublimed sulfur to obtain a bimetallic MOF/sulfur compound;

e. processing the bimetal MOF/sulfur compound in a tube furnace at the temperature of 300-800 ℃ for 2 hours in the argon atmosphere, carrying out alcohol solvent ultrasonic washing on the sample for 0.5-2 hours, then alternately cleaning with water and ethanol, centrifuging for several times until the supernatant is clear, and then carrying out vacuum drying at the temperature of 50-80 ℃ for 6-8 hours to obtain the novel carbon-based bimetal compound double-shell hollow structure electrocatalyst.

The preparation method of the invention is to obtain the novel oxygen evolution electrocatalyst with a carbon-based double-metal composite double-shell hollow structure by simply mixing alcoholic solutions of two transition metal salts and imidazole compounds with the assistance of ultrasound, then adding sublimed sulfur, and carrying out low-temperature heat treatment. The size of the novel carbon-based bimetallic composite double-shell hollow structure catalyst is controlled by regulating the proportion of metal salt pre-adsorbed in the carrier, and the active sites are improved; secondly, as heteroatom sulfur is introduced for doping, sulfide is generated in the heat treatment process, and the oxygen evolution activity of the electrode is further regulated and controlled; moreover, the hollow structure is beneficial to reducing volume expansion in the oxygen evolution reaction process and promoting charge transfer. The preparation method of the electrode material has the advantages of simple process, mild conditions and high utilization rate of raw materials, and shows good application prospect and economic value of oxygen production by electrolyzing water.

The calcination according to the invention is also referred to as calcination or heat treatment.

Advantageous effects

The invention provides an electrocatalyst with a brand-new structure; the material has excellent OER catalytic performance. At a current density of 10mA/cm²The oxygen evolution potential can approach 0.55V, and (5); at an overpotential of 320mV, TOF can be as high as 34.7s^-1。

The preparation method is simple, and the prepared material has stable performance.

Drawings

FIG. 1 is a SEM image of a solid composite prepared in comparative example 1; b is a TEM image of the solid composite prepared in comparative example 1; c is an SEM image of the hollow Co/Fe bimetallic MOF prepared in example 1; e is a TEM image thereof; d is an SEM image and f is a TEM image of the carbon-based bimetal composite double-shell hollow structure prepared in example 1; g is a HAADF-STEM diagram of the carbon-based bimetallic composite double-shell hollow structure prepared in example 1; h is the corresponding element mapping graph. (As can be seen in FIG. 1h, Co and S are mainly concentrated on the inner shell, Fe and O are mainly concentrated on the outer shell, which well illustrates the successful preparation of the carbon-based bimetallic composite double-shell hollow structure).

Fig. 2 is an SEM image of a carbon-based bimetallic composite double-shell hollow structure prepared using terephthalic acid of example 12.

Fig. 3 is an XRD pattern of the carbon-based bimetal composite double-shell hollow structure prepared in example 1.

FIG. 4 is a graph comparing the electrochemical performance of oxygen evolution for catalysts prepared in examples 1, 2, 3, 4, RuO 2.

These results indicate that the morphology of the carbon-based bimetallic composite double-shell hollow structure is a hollow sphere with a particle size of about 500nm, and that the carbon-based bimetallic composite double-shell hollow structure catalyst is similar to commercial RuO₂Comparable oxygen evolution performance under alkaline conditions.

Detailed Description

The following examples are intended to illustrate the invention without limiting it. In the examples

The current density is 10mA/cm²As a uniform reference point, the oxygen evolution potential was read directly from the LSV plot of the catalyst, and the reference electrode was an Ag/AgCl electrode. The TOF of a catalyst at an overpotential of 320mV can be calculated according to the following equation:

TOF＝(J×A)/(4×F×n)

j represents a given overpotential, A represents the electrode area, 4 represents O per mole₂4 mol of electrons are transferred to the reaction chamber,f represents the faraday constant and n represents the molar amount of metal ions on the electrode.

Example 1

Respectively dissolving 3mol of cobalt salt (cobalt nitrate), 8mol of dimethyl imidazole and 1mol of ferric salt (ferric trichloride) in 40mL of methanol, performing ultrasonic treatment for 10min to form a uniform solution, adding the methanol solution of the cobalt salt into the methanol solution of the dimethyl imidazole at the dropping rate of 5mL/min, continuing the ultrasonic treatment for 10min, adding the methanol solution of the ferric salt into the solution at the dropping rate of 5mL/min, continuing the ultrasonic treatment for 30min, transferring the solution into a high-pressure reaction kettle, heating to 120 ℃, treating for 4h, cooling to room temperature, alternately washing and centrifuging with water and absolute ethyl alcohol for three times, and performing vacuum drying at 60 ℃ for 10h to obtain the hollow Co₃/Fe₁Bimetallic MOFs (SEM and TEM figures see c and e of fig. 1); taking 10g of hollow Co₃/Fe₁Grinding bimetallic MOF and 10g of sublimed sulfur uniformly, carrying out heat treatment for 3 hours at a heating rate of 5 ℃/min to 500 ℃ (calcination temperature) in an argon atmosphere, cooling to room temperature, dissolving in 40mL of methanol, carrying out ultrasonic treatment for 30min, centrifuging at 10000rpm for 5min, and drying at 60 ℃ for 10 hours; obtaining the composite material; SEM and TEM drawings of this material are shown in figures d and f of FIG. 1. Comprises a carbon shell, wherein the inner surface of the carbon shell is compounded with cobalt sulfide, and the outer surface of the carbon shell is compounded with iron oxide. The particle size of the composite material is 500nm, wherein the content of cobalt sulfide is 15%, the content of ferroferric oxide is 10%, and the content of carbon is 68%.

The oxygen evolution performance results are as follows: at a current density of 10mA/cm²The oxygen evolution potential is 0.55V; at an overpotential of 320mV, TOF is 34.7s^-1。

Example 2:

compared with example 1, the difference is only that the molar ratio of the metallic cobalt salt to the iron salt is 4: 1; the values of other materials and parameters are not changed. A composite material with a similar structural morphology as in example 1 was obtained. The oxygen evolution performance results are as follows: at a current density of 10mA/cm²The oxygen evolution potential is 0.63V; at an overpotential of 320mV, TOF is 11.3s^-1。

Example 3:

compared with example 1, the difference is only that the molar ratio of the metallic cobalt salt to the iron salt is 2: 1;the values of other materials and parameters are not changed. A composite material with a similar structural morphology as in example 1 was obtained. The oxygen evolution performance results are as follows: at a current density of 10mA/cm²The oxygen evolution potential is 0.67V; at an overpotential of 320mV, TOF is 8.6s^-1。

Example 4:

compared with example 1, the difference is only that the molar ratio of the metallic cobalt salt to the iron salt is 1: 1; the values of other materials and parameters are not changed. A composite material with a similar structural morphology as in example 1 was obtained. The oxygen evolution performance results are as follows: at a current density of 10mA/cm²The oxygen evolution potential is 0.72V; at an overpotential of 320mV, TOF is 4.2s^-1。

Example 5: compared with example 1, the difference is only that the calcination temperature is 800 ℃; the values of other materials and parameters are not changed. A composite material with a similar structural morphology as in example 1 was obtained. The oxygen evolution performance results are as follows: at a current density of 10mA/cm²The oxygen evolution potential is 0.64V; at an overpotential of 320mV, TOF is 14.6s^-1。

Example 6:

compared with example 1, the difference is only that the calcination temperature is 300 ℃; the values of other materials and parameters are not changed. A composite material with a similar structural morphology as in example 1 was obtained. The oxygen evolution performance results are as follows: at a current density of 10mA/cm²The oxygen evolution potential is 0.72V; at an overpotential of 320mV, TOF is 8.4s^-1。

Example 7:

compared with the example 1, the difference is only that the temperature rising rate of the calcining process is 8 ℃/min; the values of other materials and parameters are not changed. A composite material with a similar structural morphology as in example 1 was obtained. The oxygen evolution performance results are as follows: at a current density of 10mA/cm²The oxygen evolution potential is 0.57V; at an overpotential of 320mV, TOF is 21.5s^-1。

Example 8:

compared with the example 1, the difference is only that the temperature rising rate of the calcining process is 2 ℃/min; the values of other materials and parameters are not changed. To obtainA composite material with a similar structural morphology as in example 1. The oxygen evolution performance results are as follows: at a current density of 10mA/cm²The oxygen evolution potential is 0.61V; at an overpotential of 320mV, TOF is 18.7s^-1。

Example 9

Respectively dissolving 3mol of cobalt salt (cobalt nitrate), 8mol (616mg) of dimethyl imidazole and 1mol of nickel salt (nickel nitrate) in 40mL of methanol, performing ultrasonic treatment for 10min to form a uniform solution, adding the methanol solution of the cobalt salt into the methanol solution of the dimethyl imidazole at the dropping rate of 5mL/min, continuing the ultrasonic treatment for 10min, adding the methanol solution of the nickel salt into the solution at the dropping rate of 5mL/min, continuing the ultrasonic treatment for 30min, transferring the solution into a high-pressure reaction kettle, heating to 120 ℃, treating for 4h, cooling to room temperature, alternately washing and centrifuging with water and absolute ethyl alcohol for three times, and performing vacuum drying at 60 ℃ for 10h to obtain hollow Co/Ni bimetallic MOF; uniformly grinding 10g of hollow Co/Ni bimetallic MOF and 10g of sublimed sulfur, carrying out heat treatment for 3 hours at the heating rate of 4-6 ℃/min to 500 ℃ in an argon atmosphere, cooling to room temperature, dissolving in 40mL of methanol, carrying out ultrasonic treatment for 30 minutes, centrifuging at 10000rpm for 5 minutes, and drying at 60 ℃ for 10 hours; a composite material with a similar structural morphology as in example 1 was obtained. The oxygen evolution performance results are as follows: at a current density of 10mA/cm²The oxygen evolution potential is 0.58V; at an overpotential of 320mV, TOF was 17.3s^-1。

Example 10

Respectively dissolving 3mol of cobalt salt (cobalt nitrate), 8mol of dimethyl imidazole and 1mol of copper salt (copper nitrate) in 40mL of methanol, performing ultrasonic treatment for 10min to form a uniform solution, adding the methanol solution of the cobalt salt into the methanol solution of the dimethyl imidazole at a dropping rate of 5mL/min, continuing the ultrasonic treatment for 10min, adding the methanol solution of the copper salt into the solution at a dropping rate of 5mL/min, continuing the ultrasonic treatment for 30min, then transferring the solution into a high-pressure reaction kettle, heating to 120 ℃, treating for 4h, cooling to room temperature, alternately washing and centrifuging with water and absolute ethyl alcohol for three times, and performing vacuum drying at 60 ℃ for 10h to obtain hollow Co/Cu MOF; uniformly grinding 10g of hollow Co/Cu bimetallic MOF and 10g of sublimed sulfur, carrying out heat treatment for 3 hours at the temperature rising rate of 4-6 ℃/min to 500 ℃ in the argon atmosphere, cooling to room temperature, dissolving in 40mL of methanol, carrying out ultrasonic treatment for 30min, centrifuging at 10000rpm for 5And (3) min, drying at 60 ℃ for 10h to obtain the composite material with the structure and the appearance similar to those of the example 1. The oxygen evolution performance results are as follows: at a current density of 10mA/cm²The oxygen evolution potential is 0.61V; at an overpotential of 320mV, TOF is 12.8s^-1。

Example 11

Respectively dissolving 3mol of cobalt salt (cobalt nitrate), 8mol of dimethyl imidazole and 1mol of zinc salt (zinc nitrate) in 40mL of methanol, performing ultrasonic treatment for 10min to form a uniform solution, adding the methanol solution of the cobalt salt into the methanol solution of the dimethyl imidazole at the dropping rate of 5mL/min, continuing the ultrasonic treatment for 10min, adding the methanol solution of the zinc salt into the solution at the dropping rate of 5mL/min, continuing the ultrasonic treatment for 30min, transferring the solution into a high-pressure reaction kettle, heating to 120 ℃, treating for 4h, cooling to room temperature, alternately washing and centrifuging with water and absolute ethyl alcohol for three times, and performing vacuum drying at 60 ℃ for 10h to obtain hollow Co/Zn MOF; and (3) uniformly grinding 10g of hollow Co/Zn bimetallic MOF and 10g of sublimed sulfur, heating to 500 ℃ at a heating rate of 4-6 ℃/min for 3 hours in an argon atmosphere, cooling to room temperature, dissolving in 40mL of methanol, performing ultrasonic treatment for 30 minutes, centrifuging at 10000rpm for 5 minutes, and drying at 60 ℃ for 10 hours to obtain the composite material with the structure and the appearance similar to those of the embodiment 1. The oxygen evolution performance results are as follows: at a current density of 10mA/cm²The oxygen evolution potential is 0.64V; at an overpotential of 320mV, TOF is 14.8s^-1。

Example 12

Respectively dissolving 3mol of cobalt salt (cobalt nitrate), 8mol of dimethyl imidazole and manganese salt (manganese nitrate) in 40mL of methanol, performing ultrasonic treatment for 10min to form a uniform solution, adding the methanol solution of the cobalt salt into the methanol solution of the dimethyl imidazole at a dropping rate of 5mL/min, continuing the ultrasonic treatment for 10min, adding the methanol solution of the manganese salt into the solution at a dropping rate of 5mL/min, continuing the ultrasonic treatment for 30min, then transferring the solution into a high-pressure reaction kettle, heating to 120 ℃, treating for 4h, cooling to room temperature, alternately washing and centrifuging with water and absolute ethyl alcohol for three times, and performing vacuum drying at 60 ℃ for 10h to obtain hollow Co/Mn MOF; uniformly grinding 10g of hollow Co/Mn bimetallic MOF and 10g of sublimed sulfur, treating for 3 hours at the temperature of 500 ℃ at the heating rate of 4-6 ℃/min under the argon atmosphere, cooling to room temperature, dissolving in 40mL of methanol, performing ultrasonic treatment for 30 minutes,centrifuging at 10000rpm for 5min, and drying at 60 ℃ for 10h to obtain the composite material with the structure and the appearance similar to those of the example 1. The oxygen evolution performance results are as follows: at a current density of 10mA/cm²The oxygen evolution potential is 0.66V; at an overpotential of 320mV, TOF is 8.8s^-1。

Example 13:

the difference compared to example 1 is only that the hydrothermal reaction temperature is 60 ℃. A composite material with a similar structural morphology as in example 1 was obtained. The oxygen evolution performance results are as follows: at a current density of 10mA/cm²The oxygen evolution potential is 0.70V; at an overpotential of 320mV, TOF is 5.4s^-1。

Example 14:

the difference compared to example 1 is only that the hydrothermal reaction temperature is 180 ℃. A composite material with a similar structural morphology as in example 1 was obtained. The oxygen evolution performance results are as follows: at a current density of 10mA/cm²The oxygen evolution potential is 0.67V; at an overpotential of 320mV, TOF is 13.5s^-1。

Example 15:

the difference compared to example 1 is only that the hydrothermal reaction temperature is 140 ℃. A composite material with a similar structural morphology as in example 1 was obtained. The oxygen evolution performance results are as follows: at a current density of 10mA/cm²The oxygen evolution potential is 0.59V; at an overpotential of 320mV, TOF is 15.2s^-1。

Example 16

The only difference compared to example 1 is that the mass ratio of bimetallic MOF to sublimed sulphur was 4: 1. A composite material with a similar structural morphology as in example 1 was obtained. The oxygen evolution performance results are as follows: at a current density of 10mA/cm²The oxygen evolution potential is 0.64V; at an overpotential of 320mV, TOF is 9.1s^-1。

Example 17

Compared to example 1, the only difference is that the ligand material used is terephthalic acid, resulting in a cubic morphology of the composite. The oxygen evolution performance results are as follows: at a current density of 10mA/cm²The oxygen evolution potential is 0.68V; at an overpotential of 320mV, TOF is 11.5s^-1。

Comparative example 1

Compared with the example 1, the difference is only that the hydrothermal reaction process is omitted; after being subjected to ultrasonic treatment, cobalt salt, dimethyl imidazole and ferric salt are subjected to solid-liquid separation, dried and directly mixed with sulfur, and subsequent calcination is carried out to obtain the solid material. The oxygen evolution performance results are as follows: at a current density of 10mA/cm²The oxygen evolution potential is 0.75V; at an overpotential of 320mV, TOF is 0.7s^-1。

Comparative example 2:

compared to example 1, the only difference is that the boosted sulfur milling process is eliminated; that is, the obtained bimetallic MOF is directly subjected to the subsequent calcination treatment. The oxygen evolution performance results are as follows: at a current density of 10mA/cm²The oxygen evolution potential is 0.88V; at an overpotential of 320mV, TOF is 0.1s^-1。

Comparative example 3:

the only difference compared to example 1 is that the calcination temperature was 200 ℃. The oxygen evolution performance results are as follows: at a current density of 10mA/cm²The oxygen evolution potential is 0.84V; at an overpotential of 320mV, TOF is 0.5s^-1。

Comparative example 4

The only difference compared to example 1 is that the calcination temperature was 900 ℃. The oxygen evolution performance results are as follows: at a current density of 10mA/cm²The oxygen evolution potential is 0.59V; at an overpotential of 320mV, TOF is 3.3s^-1。

Comparative example 5

Dissolving dimethylimidazole and ferric salt in 40mL of methanol respectively, performing ultrasonic treatment for 10min to form a uniform solution, adding the methanol solution of ferric salt into the methanol solution of dimethylimidazole at a dropping rate of 5mL/min, performing ultrasonic treatment for 30min, transferring the solution into a high-pressure reaction kettle, heating to 80-160 ℃, treating for 4-8 h, cooling to room temperature, alternately washing and centrifuging with water and absolute ethyl alcohol for three times, and performing vacuum drying at 60 ℃ for 10h to obtain hollow Fe-MOF; uniformly grinding 10g of hollow Fe-MOF and 10g of sublimed sulfur, carrying out heat treatment on the mixture for 3 hours at the temperature rising rate of 4-6 ℃/min to 500 ℃ in an argon atmosphere, and cooling the mixture to room temperatureDissolving in 40mL methanol, ultrasonic treating for 30min, centrifuging at 10000rpm for 5min, and drying at 60 deg.C for 10 h. The oxygen evolution performance results are as follows: at a current density of 10mA/cm²The oxygen evolution potential is 0.74V; at an overpotential of 320mV, TOF is 0.5s^-1. Compared with the embodiment 1, the bimetallic hollow composite material similar to the invention cannot be obtained by adopting single metal, and the OER catalytic performance is obviously inferior to the technical scheme of the invention.

Claims

1. The carbon-based bimetal composite material is characterized by comprising a carbon-based shell, wherein the inner surface of the carbon-based shell is compounded with a sulfide of a transition metal A, and the outer surface of the carbon-based shell is compounded with an oxide of a transition metal B; the transition metals A and B are selected from different metals;

wherein, the transition metal A is selected from at least one of Co and Zn; the transition metal B is selected from at least one of Fe, Ni, Cu, Zn and Mn.

2. The carbon-based bimetallic composite of claim 1, wherein said carbon-based shell is doped with a heteroatom of at least one of N, S.

3. The carbon-based bimetallic composite of claim 1, wherein the end of said carbon-based shell adjacent the inner surface is infiltrated with a sulfide of transition metal a; the oxide of the transition metal B is infiltrated near the outer surface end.

4. The carbon-based bimetallic composite of claim 1, wherein the carbon-based bimetallic composite is spherical or spheroidal.

5. The carbon-based bimetallic composite material as in any one of claims 1 to 4, wherein the transition metal A has a sulfide content of 5 to 25%; the content of the oxide of the transition metal B is 1-15%; the content of the carbon-based shell is 60-94%.

6. The preparation method of the carbon-based bimetallic composite material as in any one of claims 1 to 5, wherein a mixed solution containing a salt of a transition metal A, a salt of a transition metal B, an organic ligand and an alcohol is subjected to a hydrothermal reaction at 60-180 ℃ to obtain bimetallic MOF; and mixing the obtained bimetallic MOF with sublimed sulfur, and roasting at 300-800 ℃ in a protective atmosphere to obtain the carbon-based bimetallic composite material.

7. The method for preparing the carbon-based bimetallic composite material as in claim 6, wherein the alcohol is C1-4 monoalcohol or polyol.

8. The method of claim 7, wherein the alcohol is methanol.

9. The method of claim 6, wherein the organic ligand is at least one of dimethylimidazole, terephthalic acid, and pyridine.

10. The method of claim 6, wherein the ratio of the molar amount of the organic ligand to the sum of the molar amount of the transition metal A, B is 2 to 8 times.

11. The method of preparing a carbon-based bimetallic composite as in claim 6, wherein the molar ratio between transition metals A and B is 5: 1-1: 2.

12. the preparation method of the carbon-based bimetallic composite material as in claim 6, wherein the mass ratio of the bimetallic MOF to the sublimed sulfur is 1-4.

13. The preparation method of the carbon-based bimetallic composite material as in claim 6, wherein the hydrothermal reaction time is 1-12 h; the roasting time is 1-12 h.

14. The application of the carbon-based bimetallic composite material as in any one of claims 1-5, wherein the carbon-based bimetallic composite material is used as an OER electrocatalyst for catalyzing alkaline electrolysis water oxygen generation reaction.