Nickel-cobalt skin-core structure catalyst, and preparation method therefor and use thereof

Abstract

The present disclosure discloses a catalyst with nickel-cobalt skin-core structure and a preparation method and application thereof. By epitaxial growth, the nickel-cobalt micronano structure is obtained. The construction of the nickel-cobalt micronano structure greatly increases the reactive activity of the catalyst, and the prepared catalyst has excellent industrial application prospect.

Description

TECHNICAL FIELD

[0001] The present disclosure relates to the field of catalyst technologies and in particular to a catalyst with nickel-cobalt skin-core structure and a preparation method and application thereof.BACKGROUND

[0002] With the increasing attention of the world on the environment, various countries adopt many measures to reduce carbon emission. The industrial production and the energy production are the main sources of carbon emission while a huge amount of carbon emission from the industrial and energy productions comes from use of fossil resources. Therefore, in order to reduce the carbon emission, it is necessary to carry out adjustment to the energy structure, so as to reduce or even replace the use of the fossil resources from the angles of energy and materials. From the angle of materials, it is required to seek a renewable novel material capable of entering carbon cycle, for example, a biomass material. At present, the bio-based platform compounds have entered promotion stage and even partially replaced the use of the petrochemical products. With the bio-based platform compound 2,5-furandicarboxylic acid (FDCA) as example, its polymerization product polyethylene 2,5-furandicarboxylate (PEF) is greener and more environment-friendly, and more excellent in gas barrier property, melting temperature and mechanical property than petroleum-based polyethylene terephthalate (PET).

[0003] In the prior arts, the production of FDCA is mainly carried out by thermal catalysis, but the reaction condition for production of FDCA by thermal catalysis is relatively stringent, that is, it should be carried out in an oxygen environment of high temperature and high pressure with a precious metal catalyst. Especially in the practical large-scale production, it is usually required to maintain O 2 pressure at about 2MPa, resulting in a large safety risk. In addition to production of FDCA by thermal catalysis, conversion of 5-Hydroxymethylfurfural (HMF) into FDCA by electrocatalysis also draws much attention. Compared with thermal catalysis, the electrocatalysis has the advantages of milder and more operable reaction condition. Due to presence of aldehyde, HMF has an active chemical property and easy to spoil after long time of storage, affecting the purity of the product FDCA. Therefore, selection of 2,5-furandimethanol (BHMF) with higher chemical stability as a raw material for preparation of FDCA will help obtain FDCA with higher purity. But a catalyst with higher catalytic activity is required. The existing catalysts mainly have the following problems: due to shortage of active sites exposed on the surface of the catalysts, the activity of the catalysts is lower, failing to meet industrial production requirements; the structural stability of the catalysts is poorer and the supported catalysts usually face peeling problems, leading to sharp decrease of the catalytic activity.SUMMARY

[0004] For the shortcomings of the prior arts, the present disclosure aims to provide a method of preparing a catalyst with stable structure, rich catalysis sites and high activity.

[0005] In order to solve the above technical problems, a first aspect of the present disclosure provides a catalyst with nickel-cobalt skin-core structure, which includes a metal cobalt substrate and a micronano structure grown on the metal cobalt substrate. The micronano structure includes a core layer and a skin layer wrapping the core layer. The core layer is a cobalt micron wire or micron rod. The skin layer is a cobalt-nickel hydroxide.

[0006] The catalyst with nickel-cobalt skin-core structure in the present disclosure has stable micronano structure which exposes more specific surface area and more catalytic active sites than the metal cobalt substrate, cobalt micron wire and the cobalt micron bar, such that the catalyst has excellent activity. The cobalt substrate has high conductivity and the surface micronano cobalt component enables an electrochemical onset potential of the catalyst to be lower and with introduction of nickel component, the catalyst has a high current density.

[0007] A second aspect of the present disclosure provides a preparation method of the above catalyst with nickel-cobalt skin-core structure, which includes the following steps: at step S1, immersing a metal cobalt substrate in an oxalic acid solution, and by epitaxial growth, growing a stable cobalt oxalate micron wire or micron rod on a surface of the metal cobalt substrate to obtain a cobalt oxalate precursor; at step S2, placing the cobalt oxalate precursor into a hydrogen atmosphere for reduction to obtain a cobalt intermediate; and, at step S3, soaking the cobalt intermediate in a nickel salt solution and growing epitaxially a cobalt-nickel hydroxide on a surface of the cobalt micron wire or micron rod to obtain a catalyst with nickel-cobalt skin-core structure.

[0008] In the present disclosure, by epitaxial growth, the nickel-cobalt micronano structure is obtained. The construction of the nickel-cobalt micronano structure greatly increases the reactive activity of the catalyst, and the prepared catalyst has excellent industrial application prospect.

[0009] In a preferable or optional example, the metal cobalt substrate is selected from any one of metal cobalt foam, cobalt sheet, cobalt foil, and cobalt net. The preparation method can obtain a catalyst with high activity without using a precious metal, bringing down the production costs.

[0010] In a preferable or optional example, in the step S1, a molar ratio of the metal cobalt substrate to oxalic acid is 1:5.5 to 28.

[0011] In a preferable or optional example, in the step S1, the reaction time of the epitaxial growth is 0.25 to 4h and the reaction temperature is 20 to 80°C.

[0012] At step S1, by in-situ expitaxial growth, the cobalt oxalate precursor with stable structure can be obtained. The molar ratio of the metal cobalt substrate to the oxalic acid and the reaction time and the reaction temperature of the epitaxial growth can affect the specific surface area of the material. Within the above limitation scope, on the surface of the cobalt substrate, the cobalt oxalate micron wire or micron rod precursor with stable structure can be grown and thus sufficient specific surface area can be provided.

[0013] In a preferable or optional example, the step S2 specifically includes: placing the cobalt oxalate precursor into a tubular furnace and introducing hydrogen into the tubular furnace and holding for a period of time, and then heating to a set temperature and then holding the temperature and cooling down to room temperature to obtain the cobalt intermediate.

[0014] In the step S2, the cobalt oxalate precursor is reduced with hydrogen into metal cobalt so as to obtain the cobalt intermediate with stable structure.

[0015] In a preferable or optional example, in the step S2, a gas volume flowrate of hydrogen is 5 to 100mL / min, and held for 20 to 40min and then heated. With a given gas flowrate, a reduction product can be quickly carried away.

[0016] In a preferable or optional example, in the step S2, with a heating rate of 1 to 10°C / min, the tubular furnace is heated to 100 to 550°C and held for 1 to 5h. Under high temperature, hydrogen has high reductibility and with limited temperature and holding time, the cobalt oxalate precursor can be completely reduced into the cobalt intermediate.

[0017] In a preferable or optional example, the concentration of the nickel salt solution is 10 to 30mM, and a solute of the nickel salt solution is selected from any one or combination of nickel sulfate, nickel nitrate and nickel chloride.

[0018] In a preferable or optional example, in the step S3, the reaction temperature of the epitaxial growth is 20 to 60°C and the reaction time is 20 to 80h.

[0019] In the step S3, by corrosion, reduction and ion exchange and the like, the cobalt-nickel nano structure is epitaxially grown on the surface of the cobalt intermediate of the cobalt, and the metal activity of the metal cobalt is strong. Therefore, the nickel ions can etch the metal cobalt to produce cobalt ions and in the presence of dissolved oxygen, the cobalt-nickel hydroxide is epitaxially grown on the surface of the cobalt substrate, so as to form a stable nickel-cobalt skin-core structure. The nickel salt type, the concentration, the reaction time, and the reaction temperature are important parameters for formation of the catalyst with nickel-cobalt skin-core structure. Within the above limitation scope, the nickel-cobalt skin-core structure catalyst with rich catalytic active sites and high catalytic activity.

[0020] A third aspect of the present disclosure provides an application of the above catalyst with nickel-cobalt skin-core structure to perform electrocatalytic oxidation of furan compound.

[0021] In a preferable or optional example, the catalyst with nickel-cobalt skin-core structure is used as a working electrode, the electrolyte for catalysis is a potassium hydroxide and / or sodium hydroxide solution, and the catalysis substrate is a furan compound which includes 2,5-furandimethanol, 5-hydroxymethylfurfural, 2,5-diformylfuran, 5-hydroxymethyl-2-furancarboxylic acid, 5-formyl-2-furancarboxylic acid, furfural, and furfuryl alcohol and the like.

[0022] In conclusion, compared with the prior arts, the present disclosure has the following beneficial effects.

[0023] In the present disclosure, the metal cobalt substrate in the catalyst with nickel-cobalt skin-core structure has high conductivity and the surface micronano cobalt component enables the electrochemical onset potential of the catalyst to be lower and with introduction of nickel component, the catalyst has high current density. The construction of the nickel-cobalt micronano structure greatly increases the reactive activity of the catalyst, and the prepared catalyst has excellent industrial application prospect.

[0024] In the present disclosure, the preparation method of the catalyst with nickel-cobalt skin-core structure is simple to operate and has strong repeatability and the catalyst with high activity can be obtained without using precious metal. The catalyst with micronano structure prepared by in-situ epitaxial growth can have better structural stability and larger specific surface area and thus expose more active sites, improving the activity of the catalyst.

[0025] In the present disclosure, the catalyst with nickel-cobalt skin-core structure has stable structure, many catalytic active sites and high catalytic activity and has high catalytic activity on the furan compound and can satisfy the current density desired for the industrial production. Therefore, the high-purity FDCA can be prepared.BRIEF DESCRIPTIONS OF THE DRAWINGS

[0026] FIG. 1 is a scanning electron microscopy (SEM) image illustrating a cobalt oxalate precursor according to an example 1 of the present disclosure. FIG. 2 is a SEM image illustrating a catalyst with nickel-cobalt skin-core structure according to an example 1 of the present disclosure. FIG. 3 is a transmission electron microscopy (TEM) image and a high-angle annular dark-field image illustrating a catalyst with nickel-cobalt skin-core structure according to an example 1 of the present disclosure. FIG. 4 is an element distribution diagram illustrating a catalyst with nickel-cobalt skin-core structure according to an example 1 of the present disclosure. FIG. 5 is a linear scanning voltammogram illustrating a catalyst with nickel-cobalt skin-core structure in an electrolyte according to an example 9 of the present disclosure. FIG. 6 is a result diagram illustrating electrocatalysis of HMF into FDCA by using a catalyst with nickel-cobalt skin-core structure through oxidation according to an example 9 of the present disclosure. DETAILED DESCRIPTIONS OF EMBODIMENTS

[0027] In order to make the above objects, features and advantages of the present disclosure clearer and more intelligible, the specific examples of the present disclosure will be detailed below in combination with drawings.

[0028] It should be understood that the terms in the present disclosure are used only to describe specific examples rather than to limit the present disclosure. Furthermore, the numerical range of the present disclosure shall be understood as further specifically disclosing each medium value between an upper limit and a lower limit of the range. Any stated value, or any medium value within the stated range, and any other stated value or each smaller range between the medium values within the above range shall also be included in the present disclosure. The upper limit and lower limit of these smaller ranges can be independently included in or excluded from the ranges.

[0029] Without departing from the spirit or scope of the present disclosure, various improvements and changes can be made to the specific examples of the present disclosure, which is apparent to those skilled in the arts. It is apparent for those skilled in the arts to obtain other examples from the specification of the present disclosure. The specification and the examples of the present disclosure are only illustrative.

[0030] A specific example of the present disclosure provides a catalyst with nickel-cobalt skin-core structure, which is prepared in the following method.

[0031] At step S1, a metal cobalt substrate is immersed in an oxalic acid solution, and by epitaxial growth, a cobalt oxalate micron wire or micron rod is grown on a surface of the metal cobalt substrate to obtain a cobalt oxalate precursor.

[0032] In a specific example, the metal cobalt substrate is selected from any one of metal cobalt foam, cobalt sheet, cobalt foil and cobalt net; a typical metal cobalt substrate is a foam cobalt. The metal cobalt substrate with three-dimensional structure can expose many active sites, helping increase the stability of the electrocaltalyst.

[0033] In a specific example, the solvent in the oxalic acid solution is water with a concentration of 6 to 30mM. The typical concentration includes 6mM, 8mM, 10mM, 12mM, 15mM, 20mM, 22mM, 25mM, 28mM and 30mM and so on. The molar ratio of the metal cobalt substrate to oxalic acid is 1:5.5 to 28.

[0034] In a specific example, in the step S1, the reaction time of the epitaxial growth is 0.25 to 4h, and the typical epitaxial growth time includes 0.25h, 0.5h, 1h, 2h, 2.5h, 3h and 4h and so on. The reaction temperature of the epitaxial growth is 20 to 80°C, and the typical epitaxial growth temperature includes 25°C, 35°C, 45°C, 50°C, 60°C and 80°C and so on. The epitaxial growth is carried out under mild condition and the preparation method is simple, making it easy to realize scale production.

[0035] At step S2, the cobalt oxalate precursor is placed into a hydrogen atmosphere for reduction to obtain a cobalt intermediate. The specific steps are as follows: placing the cobalt oxalate precursor into a tubular furnace, introducing hydrogen into the tubular furnace and holding for a period of time, and then heating to a set temperature and then holding the temperature and then cooling down to room temperature so as to obtain a cobalt intermediate with stable structure.

[0036] In a specific example, the gas volume flowrate of the hydrogen is 5 to 100 mL / min and held for 20 to 40 min and then heating is performed.

[0037] In a specific example, with a heating rate of 1 to 5°C / min, the tubular furnace is heated to 100 to 550°C and held for 1 to 5h. Under high temperature, the hydrogen has high reductibility, and with limited temperature and holding time, the cobalt oxalate precursor can be completely reduced into the cobalt intermediate.

[0038] At step S3, the cobalt intermediate is soaked in a nickel salt solution and a cobalt-nickel hydroxide is epitaxially grown on a surface of the cobalt micron wire or micron rod to obtain a catalyst with nickel-cobalt skin-core structure.

[0039] In a specific example, the solvent of the nickel salt solution is water and the solute is selected from any one or combination of nickel sulfate, nickel nitrate and nickel chloride, and preferably, from nickel nitrate.

[0040] In a specific example, the concentration of the nickel salt solution is 10 to 30mM, and the typical concentration includes 10M, 12M, 15M, 20M, 22M, 25M and 30M and so on.

[0041] In a specific example, in the step S3, the reaction temperature of the epitaxial growth is 20 to 60°C, the typical reaction temperature includes 20°C, 22°C, 25°C, 28°C, 30°C, 45°C and 58°C and so on. The reaction time of the epitaxial growth is 20 to 80h and the typical reaction time includes 20h, 24h, 30h, 38h, 40h, 60h and 80h and so on.

[0042] The above preparation method is simple to operate and has strong repeatability, and the catalyst with high activity can be obtained without using precious metal. The catalyst with micronano structure obtained by in-situ epitaxial growth has better structural stability and larger specific surface area and thus can expose more active sites, improving the activity of the catalyst.

[0043] The catalyst with nickel-cobalt skin-core structure obtained by the above method includes a metal cobalt substrate and a micronano structure grown on the metal cobalt substrate. The micronano structure includes a core layer and a skin layer wrapping the core layer. The core layer is a cobalt micron wire or micron rod. The skin layer is a cobalt-nickel hydroxide. The micronano structure exposes more specific surface area and more catalytic active sites than the metal cobalt substrate, cobalt micron wire and the cobalt micron bar, such that the catalyst has excellent activity. The cobalt substrate has high conductivity and the surface micronano cobalt component enables an electrochemical onset potential of the catalyst to be lower and with introduction of nickel component, the catalyst has high current density.

[0044] The specific examples of the present disclosure further provide an application of the above catalyst with nickel-cobalt skin-core structure to electrocatalytic oxidation reaction of furan compound. The specific application method is as below: using the above electrocatalyst as a working electrode, constructing a three-electrode system in an electrolytic cell, adding a basic solution containing biomass as electrolyte into the electrolytic cell, and immersing the working electrode in the electrolyte for electrocatalytic oxidation reaction of the biomass.

[0045] In a specific example, the electrolyte is a 0.5 to 2M potassium hydroxide and / or sodium hydroxide solution containing biomass and the solvent is water; the concentration of the furan compound is 1 to 1000mM, and the typical concentration includes 10 mM, 20 mM, 50 mM, 80 mM, 100 mM, 200 mM, 400 mM and 800 mM and so on. The typical biomass includes 2,5-furandimethanol, 5-hydroxymethylfurfural, 2,5-diformylfuran, 5-hydroxymethyl-2-furancarboxylic acid, 5-formyl-2-furancarboxylic acid, furfural, and furfuryl alcohol and the like.

[0046] In a specific example, the potential of the electrocatalytic oxidation is 1.35 to 1.8V vs.RHE. The typical potential includes 1.35 V vs.RHE, 1.45 V vs.RHE, 1.5 V vs.RHE, 1.55 V vs.RHE, 1.6 V vs.RHE and 1.8V vs.RHE and so on.

[0047] The catalyst with nickel-cobalt skin-core structure has stable structure, many catalytic active sites and high catalytic activity and has high catalytic activity on the furan compound and can satisfy the current density desired for the industrial production. Therefore, the high-purity FDCA can be prepared, which has very high economic value and good industrial application prospect.

[0048] The technical effects of the present disclosure are described with the specific examples below.Example 1

[0049] (1) A cobalt foam of 0.5×3cm 2< was taken and ultrasonically cleaned with deionized water and anhydrous ethanol respectively for 10min and dried for later use. (2) The cleaned cobalt foam was immersed in 50ml of 22mM oxalic acid solution for standing and underwent constant temperature reaction for 2h at the temperature of 50°C. After the completion of the reaction, the reaction product was taken out and cleaned with deionized water and then placed into an 80°C drying oven to be dried for 2h to obtain a cobalt oxalate precursor. The cobalt oxalate precursor has a micro-morphology as shown in FIG. 1. (3) The cobalt oxalate precursor was placed into a hydrogen atmosphere tubular furnace with a flowrate of 5ml / min and held for 30min, and then heated to 500°C at the heating rate of 5°C / min and held for 2h and then cooled down to room temperature so as to obtain a cobalt intermediate. (4) The cobalt intermediate was soaked in a 10mM nickel nitrate solution for standing, and underwent constant temperature reaction for 38h at the temperature of 25°C. After the completion of the reaction, the reaction product was cleaned with deionized water and then placed into an 80°C drying oven to be dried for 2h to obtain a catalyst with nickel-cobalt skin-core structure. The scanning electron microscopy image of the catalyst with nickel-cobalt skin-core structure is as shown in FIG. 2, the transmission electron microscopy image of the catalyst with nickel-cobalt skin-core structure is as shown in FIG. 3a, the high-angle annular dark field image of the catalyst with nickel-cobalt skin-core structure is as shown in FIG. 3b, and the element distribution diagram of the catalyst with nickel-cobalt skin-core structure is as shown in FIG. 4. Example 2

[0050] (1) A cobalt foam of 0.5×3cm 2< was taken and ultrasonically cleaned with deionized water and anhydrous ethanol respectively for 10min and dried for later use. (2) The cleaned cobalt foam was immersed in 50ml of 8mM oxalic acid solution for standing and underwent constant temperature reaction for 2h at the temperature of 80°C. After the completion of the reaction, the reaction product was taken out and cleaned with deionized water and then placed into an 80°C drying oven to be dried for 2h to obtain a cobalt oxalate precursor. (3) The cobalt oxalate precursor was placed into a hydrogen atmosphere tubular furnace with a flowrate of 5ml / min and held for 30min, and then heated to 500°C at the heating rate of 5°C / min and held for 2h and then cooled down to room temperature so as to obtain a cobalt intermediate. (4) The cobalt intermediate was soaked in a 20mM nickel nitrate solution for standing, and underwent constant temperature reaction for 38h at the temperature of 25°C. After the completion of the reaction, the reaction product was cleaned with deionized water and then placed into an 80°C drying oven to be dried for 2h to obtain a catalyst with nickel-cobalt skin-core structure. Example 3

[0051] (1) A cobalt foam of 0.5×3cm 2< was taken and ultrasonically cleaned with deionized water and anhydrous ethanol respectively for 10min and dried for later use. (2) The cleaned cobalt foam was immersed in 50ml of 22mM oxalic acid solution for standing and underwent constant temperature reaction for 2h at the temperature of 80°C. After the completion of the reaction, the reaction product was taken out and cleaned with deionized water and then placed into an 80°C drying oven to be dried for 2h to obtain a cobalt oxalate precursor. (3) The cobalt oxalate precursor was placed into a hydrogen atmosphere tubular furnace with a flowrate of 5ml / min and held for 30min, and then heated to 500°C at the heating rate of 5°C / min and held for 2h and then cooled down to room temperature so as to obtain a cobalt intermediate. (4) The cobalt intermediate was soaked in a 30mM nickel nitrate solution for standing, and underwent constant temperature reaction for 38h at the temperature of 25°C. After the completion of the reaction, the reaction product was cleaned with deionized water and then placed into an 80°C drying oven to be dried for 2h to obtain a catalyst with nickel-cobalt skin-core structure. Example 4

[0052] (1) A cobalt sheet of 0.5×3cm 2< was taken and ultrasonically cleaned with deionized water and anhydrous ethanol respectively for 10min and dried for later use. (2) The cleaned cobalt sheet was immersed in 50ml of 22mM oxalic acid solution for standing and underwent constant temperature reaction for 2h at the temperature of 80°C. After the completion of the reaction, the reaction product was taken out and cleaned with deionized water and then placed into an 80°C drying oven to be dried for 2h to obtain a cobalt oxalate precursor. (3) The cobalt oxalate precursor was placed into a hydrogen atmosphere tubular furnace with a flowrate of 5ml / min and held for 30min, and then heated to 500°C at the heating rate of 5°C / min and held for 2h and then cooled down to room temperature so as to obtain a cobalt intermediate. (4) The cobalt intermediate was soaked in a 30mM nickel nitrate solution for standing, and underwent constant temperature reaction for 38h at the temperature of 25°C. After the completion of the reaction, the reaction product was cleaned with deionized water and then placed into an 80°C drying oven to be dried for 2h to obtain a catalyst with nickel-cobalt skin-core structure. Example 5

[0053] (1) A cobalt foil of 0.5×3cm 2< was taken and ultrasonically cleaned with deionized water and anhydrous ethanol respectively for 10min and dried for later use. (2) The cleaned cobalt foil was immersed in 50ml of 8mM oxalic acid solution for standing and underwent constant temperature reaction for 2h at the temperature of 20°C. After the completion of the reaction, the reaction product was taken out and cleaned with deionized water and then placed into an 80°C drying oven to be dried for 2h to obtain a cobalt oxalate precursor. (3) The cobalt oxalate precursor was placed into a hydrogen atmosphere tubular furnace with a flowrate of 5ml / min and held for 30min, and then heated to 200°C at the heating rate of 5°C / min and held for 2h and then cooled down to room temperature so as to obtain a cobalt intermediate. (4) The cobalt intermediate was soaked in a 10mM nickel sulfate solution for standing, and underwent constant temperature reaction for 38h at the temperature of 25°C. After the completion of the reaction, the reaction product was cleaned with deionized water and then placed into an 80°C drying oven to be dried for 2h to obtain a catalyst with nickel-cobalt skin-core structure. Example 6

[0054] (1) A cobalt foam of 0.5×3cm 2< was taken and ultrasonically cleaned with deionized water and anhydrous ethanol respectively for 10min and dried for later use. (2) The cleaned cobalt foam was immersed in 50ml of 8mM oxalic acid solution for standing and underwent constant temperature reaction for 2h at the temperature of 35°C. After the completion of the reaction, the reaction product was taken out and cleaned with deionized water and then placed into an 80°C drying oven to be dried for 2h to obtain a cobalt oxalate precursor. (3) The cobalt oxalate precursor was placed into a hydrogen atmosphere tubular furnace with a flowrate of 5ml / min and held for 30min, and then heated to 300°C at the heating rate of 5°C / min and held for 2h and then cooled down to room temperature so as to obtain a cobalt intermediate. (4) The cobalt intermediate was soaked in a 10mM nickel sulfate solution for standing, and underwent constant temperature reaction for 24h at the temperature of 25°C. After the completion of the reaction, the reaction product was cleaned with deionized water and then placed into an 80°C drying oven to be dried for 2h to obtain a catalyst with nickel-cobalt skin-core structure. Example 7

[0055] (1) A cobalt sheet of 0.5×3cm 2< was taken and ultrasonically cleaned with deionized water and anhydrous ethanol respectively for 10min and dried for later use. (2) The cleaned cobalt sheet was immersed in 50ml of 16mM oxalic acid solution for standing and underwent constant temperature reaction for 2h at the temperature of 20°C. After the completion of the reaction, the reaction product was taken out and cleaned with deionized water and then placed into an 80°C drying oven to be dried for 2h to obtain a cobalt oxalate precursor. (3) The cobalt oxalate precursor was placed into a hydrogen atmosphere tubular furnace with a flowrate of 5ml / min and held for 40min, and then heated to 300°C at the heating rate of 5°C / min and held for 2h and then cooled down to room temperature so as to obtain a cobalt intermediate. (4) The cobalt intermediate was soaked in a 10mM nickel chloride solution for standing, and underwent constant temperature reaction for 20h at the temperature of 25°C. After the completion of the reaction, the reaction product was cleaned with deionized water and then placed into an 80°C drying oven to be dried for 2h to obtain a catalyst with nickel-cobalt skin-core structure. Example 8

[0056] (1) A cobalt foil of 0.5×3cm 2< was taken and ultrasonically cleaned with deionized water and anhydrous ethanol respectively for 10min and dried for later use. (2) The cleaned cobalt foil was immersed in 50ml of 8mM oxalic acid solution for standing and underwent constant temperature reaction for 2h at the temperature of 80°C. After the completion of the reaction, the reaction product was taken out and cleaned with deionized water and then placed into an 80°C drying oven to be dried for 2h to obtain a cobalt oxalate precursor. (3) The cobalt oxalate precursor was placed into a hydrogen atmosphere tubular furnace with a flowrate of 5ml / min and held for 40min, and then heated to 200°C at the heating rate of 5°C / min and held for 2h and then cooled down to room temperature so as to obtain a cobalt intermediate. (4) The cobalt intermediate was soaked in a 20mM nickel nitrate solution for standing, and underwent constant temperature reaction for 24h at the temperature of 25°C. After the completion of the reaction, the reaction product was cleaned with deionized water and then placed into an 80°C drying oven to be dried for 2h to obtain a catalyst with nickel-cobalt skin-core structure. Example 9

[0057] (1) The catalyst with nickel-cobalt skin-core structure prepared in the example 1 was mounted as an anode on an electrochemical working station. (2) The electrolyte was 20ml of 1M KOH solution, a platinum sheet was used for the electrode, and a mercury mercuric oxide electrode was used for a reference electrode. An area of the catalyst immersed in the electrolyte was 1×0.5cm 2< , and stirred by magneton at a rotation speed of 600rpm. (3) By using a linear scanning method of the electrochemical working station, an LSV curve was obtained, with a scanning rate of 5mV / s. (4) HMF was added to the electrolyte to increase the concentration to 10mM and the LSV curve was obtained with the scanning rate of 5mV / s. (5) HMF was added to the electrolyte to increase the concentration to 100mM and the LSV curve was obtained with the scanning rate of 5mV / s. The LSV curves in the above steps 3), 4) and 5) are as shown in FIG. 5. The results show the catalyst in the example 1 has a very high current density with its performance far surpassing the standard of the industrial current density. (6) In 5mL of electrolyte containing 1M KOH and 10mM HMF, electrolysis was performed with potentiostatic mode, with the electrolytic potential being 1.35V vs.RHE. The electrolytic result is as shown in FIG. 6, showing the catalyst in the example 1 has a very high HMF conversion rate and FDCA yield under low potential. The HMF conversion rate reaches 95.8% and the FDCA yield reaches 91.3%. Example 10

[0058] (1) The catalyst with nickel-cobalt skin-core structure prepared in the example 1 was mounted as an anode on an electrochemical working station. (2) The electrolyte was 20ml of 1M KOH solution, a platinum sheet was used for the electrode, and a mercury mercuric oxide electrode was used for a reference electrode. An area of the catalyst immersed in the electrolyte was 1×0.5cm 2< , and stirred by magneton at a rotation speed of 600rpm. (3) By using a linear scanning method of the electrochemical working station, an LSV curve was obtained, with a scanning rate of 5mV / s. (4) BHMF was added to the electrolyte to increase the concentration to 10mM and the LSV curve was obtained with the scanning rate of 5mV / s. (5) BHMF was added to the electrolyte to increase the concentration to 100mM and the LSV curve was obtained with the scanning rate of 5mV / s. (6) In 5mL of electrolyte containing 1M KOH and 10mM BHMF, electrolysis was performed with potentiostatic mode, with the electrolytic potential being 1.35V vs.RHE. The electrolytic result shows the catalyst in the example 1 has a HMF conversion rate of 93.6% and a FDCA yield of 90.2% under low potential. Example 11

[0059] This example differs from the example 9 in that: the catalyst with nickel-cobalt skin-core structure prepared in the example 2 is used as an anode of the electrochemical working station; in 5ml of electrolyte containing 1M KOH and 20mM 2,5-diformylfuran, electrolysis is performed with potentiostatic mode, with the electrolytic potential being 1.45 V vs.RHE. The electrolytic result shows the conversion rate of 2,5-diformylfuran is 94.8% and the FDCA yield is 89.9%.Example 12

[0060] This example differs from the example 9 in that: the catalyst with nickel-cobalt skin-core structure prepared in the example 3 is used as an anode of the electrochemical working station; in 5ml of electrolyte containing 1M KOH and 50mM 5-hydroxymethyl-2-furancarboxylic acid, electrolysis is performed with potentiostatics mode, with the electrolytic potential being 1.55 V vs.RHE. The electrolytic result shows the conversion rate of 5-hydroxymethyl-2-furancarboxylic acid is 90.4% and the FDCA yield is 86.8%.Example 13

[0061] This example differs from the example 9 in that: the catalyst with nickel-cobalt skin-core structure prepared in the example 4 is used as an anode of the electrochemical working station; in 5ml of electrolyte containing 1M KOH and 80mM 5-formyl-2-furancarboxylic acid, electrolysis is performed with potentiostatic mode, with the electrolytic potential being 1.6 V vs.RHE. The electrolytic result shows the conversion rate of 5-formyl-2-furancarboxylic acid is 94.7% and the FDCA yield is 91.0%.Example 14

[0062] This example differs from the example 9 in that: the catalyst with nickel-cobalt skin-core structure prepared in the example 5 is used as an anode of the electrochemical working station; in 5ml of electrolyte containing 1M KOH and 100mM furfural, electrolysis is performed with potentiostatic mode, with the electrolytic potential being 1.8 V vs.RHE. The electrolytic result shows the conversion rate of furfural is 88.6% and the FDCA yield is 84.3%.Example 15

[0063] This example differs from the example 9 in that: the catalyst with nickel-cobalt skin-core structure prepared in the example 6 is used as an anode of the electrochemical working station; in 5ml of electrolyte containing 1M KOH and 20mM furfuryl alcohol, electrolysis is performed with potentiostatic mode, with the electrolytic potential being 1.35 V vs.RHE. The electrolytic result shows the conversion rate of furfuryl alcohol is 89.2% and the FDCA yield is 86.1%.Example 16

[0064] This example differs from the example 9 in that: the catalyst with nickel-cobalt skin-core structure prepared in the example 7 is used as an anode of the electrochemical working station; in 5ml of electrolyte containing 1M KOH and 20mM HMF, electrolysis is performed with potentiostatic mode, with the electrolytic potential being 1.35 V vs.RHE. The electrolytic result shows the conversion rate of HMF alcohol is 93.9% and the FDCA yield is 90.2%.Example 17

[0065] This example differs from the example 9 in that: the catalyst with nickel-cobalt skin-core structure prepared in the example 8 is used as an anode of the electrochemical working station; in 5ml of electrolyte containing 1M KOH and 20mM BHMF, electrolysis is performed with potentiostatic mode, with the electrolytic potential being 1.35 V vs.RHE. The electrolytic result shows the conversion rate of BHMF alcohol is 95.9% and the FDCA yield is 92.3%.

[0066] Although the descriptions of the present disclosure are made as above, the scope of protection of the present disclosure is not limited hereto. Those skilled in the arts can, without departing from the spirit and scope of the present disclosure, make various changes and modifications, and such changes and modifications shall fall within the scope of protection of the present disclosure.

Examples

example 1

[0049] (1) A cobalt foam of 0.5×3cm 2FIG. 1. (3) The cobalt oxalate precursor was placed into a hydrogen atmosphere tubular furnace with a flowrate of 5ml / min and held for 30min, and then heated to 500°C at the heating rate of 5°C / min and held for 2h and then cooled down to room temperature so as to obtain a cobalt intermediate. (4) The cobalt intermediate was soaked in a 10mM nickel nitrate solution for standing, and underwent constant temperature reaction for 38h at the temperature of 25°C. After the completion of the reaction, the reaction product was cleaned with deionized water and then placed into an 80°C drying oven to be dried for 2h to obtain a catalyst with nickel-cobalt skin-core structure. The scanning electron microscopy image of the catalyst with nickel-cobalt skin-core structure is as shown in FIG. 2, the transmission electron microscopy image of the catalyst with nickel-cobalt skin-core structure is as shown in FIG. 3a, the high-angle annular dark field image of the ...

example 2

[0050] (1) A cobalt foam of 0.5×3cm 2< was taken and ultrasonically cleaned with deionized water and anhydrous ethanol respectively for 10min and dried for later use. (2) The cleaned cobalt foam was immersed in 50ml of 8mM oxalic acid solution for standing and underwent constant temperature reaction for 2h at the temperature of 80°C. After the completion of the reaction, the reaction product was taken out and cleaned with deionized water and then placed into an 80°C drying oven to be dried for 2h to obtain a cobalt oxalate precursor. (3) The cobalt oxalate precursor was placed into a hydrogen atmosphere tubular furnace with a flowrate of 5ml / min and held for 30min, and then heated to 500°C at the heating rate of 5°C / min and held for 2h and then cooled down to room temperature so as to obtain a cobalt intermediate. (4) The cobalt intermediate was soaked in a 20mM nickel nitrate solution for standing, and underwent constant temperature reaction for 38h at the temperature of 25°C. Aft...

example 3

[0051] (1) A cobalt foam of 0.5×3cm 2< was taken and ultrasonically cleaned with deionized water and anhydrous ethanol respectively for 10min and dried for later use. (2) The cleaned cobalt foam was immersed in 50ml of 22mM oxalic acid solution for standing and underwent constant temperature reaction for 2h at the temperature of 80°C. After the completion of the reaction, the reaction product was taken out and cleaned with deionized water and then placed into an 80°C drying oven to be dried for 2h to obtain a cobalt oxalate precursor. (3) The cobalt oxalate precursor was placed into a hydrogen atmosphere tubular furnace with a flowrate of 5ml / min and held for 30min, and then heated to 500°C at the heating rate of 5°C / min and held for 2h and then cooled down to room temperature so as to obtain a cobalt intermediate. (4) The cobalt intermediate was soaked in a 30mM nickel nitrate solution for standing, and underwent constant temperature reaction for 38h at the temperature of 25°C. Af...

TECHNICAL FIELD

[0001] The present disclosure relates to the field of catalyst technologies and in particular to a catalyst with nickel-cobalt skin-core structure and a preparation method and application thereof.BACKGROUND

[0002] With the increasing attention of the world on the environment, various countries adopt many measures to reduce carbon emission. The industrial production and the energy production are the main sources of carbon emission while a huge amount of carbon emission from the industrial and energy productions comes from use of fossil resources. Therefore, in order to reduce the carbon emission, it is necessary to carry out adjustment to the energy structure, so as to reduce or even replace the use of the fossil resources from the angles of energy and materials. From the angle of materials, it is required to seek a renewable novel material capable of entering carbon cycle, for example, a biomass material. At present, the bio-based platform compounds have entered promotion stage and even partially replaced the use of the petrochemical products. With the bio-based platform compound 2,5-furandicarboxylic acid (FDCA) as example, its polymerization product polyethylene 2,5-furandicarboxylate (PEF) is greener and more environment-friendly, and more excellent in gas barrier property, melting temperature and mechanical property than petroleum-based polyethylene terephthalate (PET).

[0003] In the prior arts, the production of FDCA is mainly carried out by thermal catalysis, but the reaction condition for production of FDCA by thermal catalysis is relatively stringent, that is, it should be carried out in an oxygen environment of high temperature and high pressure with a precious metal catalyst. Especially in the practical large-scale production, it is usually required to maintain O 2 pressure at about 2MPa, resulting in a large safety risk. In addition to production of FDCA by thermal catalysis, conversion of 5-Hydroxymethylfurfural (HMF) into FDCA by electrocatalysis also draws much attention. Compared with thermal catalysis, the electrocatalysis has the advantages of milder and more operable reaction condition. Due to presence of aldehyde, HMF has an active chemical property and easy to spoil after long time of storage, affecting the purity of the product FDCA. Therefore, selection of 2,5-furandimethanol (BHMF) with higher chemical stability as a raw material for preparation of FDCA will help obtain FDCA with higher purity. But a catalyst with higher catalytic activity is required. The existing catalysts mainly have the following problems: due to shortage of active sites exposed on the surface of the catalysts, the activity of the catalysts is lower, failing to meet industrial production requirements; the structural stability of the catalysts is poorer and the supported catalysts usually face peeling problems, leading to sharp decrease of the catalytic activity.SUMMARY

[0004] For the shortcomings of the prior arts, the present disclosure aims to provide a method of preparing a catalyst with stable structure, rich catalysis sites and high activity.

[0005] In order to solve the above technical problems, a first aspect of the present disclosure provides a catalyst with nickel-cobalt skin-core structure, which includes a metal cobalt substrate and a micronano structure grown on the metal cobalt substrate. The micronano structure includes a core layer and a skin layer wrapping the core layer. The core layer is a cobalt micron wire or micron rod. The skin layer is a cobalt-nickel hydroxide.

[0006] The catalyst with nickel-cobalt skin-core structure in the present disclosure has stable micronano structure which exposes more specific surface area and more catalytic active sites than the metal cobalt substrate, cobalt micron wire and the cobalt micron bar, such that the catalyst has excellent activity. The cobalt substrate has high conductivity and the surface micronano cobalt component enables an electrochemical onset potential of the catalyst to be lower and with introduction of nickel component, the catalyst has a high current density.

[0007] A second aspect of the present disclosure provides a preparation method of the above catalyst with nickel-cobalt skin-core structure, which includes the following steps: at step S1, immersing a metal cobalt substrate in an oxalic acid solution, and by epitaxial growth, growing a stable cobalt oxalate micron wire or micron rod on a surface of the metal cobalt substrate to obtain a cobalt oxalate precursor; at step S2, placing the cobalt oxalate precursor into a hydrogen atmosphere for reduction to obtain a cobalt intermediate; and, at step S3, soaking the cobalt intermediate in a nickel salt solution and growing epitaxially a cobalt-nickel hydroxide on a surface of the cobalt micron wire or micron rod to obtain a catalyst with nickel-cobalt skin-core structure.

[0008] In the present disclosure, by epitaxial growth, the nickel-cobalt micronano structure is obtained. The construction of the nickel-cobalt micronano structure greatly increases the reactive activity of the catalyst, and the prepared catalyst has excellent industrial application prospect.

[0009] In a preferable or optional example, the metal cobalt substrate is selected from any one of metal cobalt foam, cobalt sheet, cobalt foil, and cobalt net. The preparation method can obtain a catalyst with high activity without using a precious metal, bringing down the production costs.

[0010] In a preferable or optional example, in the step S1, a molar ratio of the metal cobalt substrate to oxalic acid is 1:5.5 to 28.

[0011] In a preferable or optional example, in the step S1, the reaction time of the epitaxial growth is 0.25 to 4h and the reaction temperature is 20 to 80°C.

[0012] At step S1, by in-situ expitaxial growth, the cobalt oxalate precursor with stable structure can be obtained. The molar ratio of the metal cobalt substrate to the oxalic acid and the reaction time and the reaction temperature of the epitaxial growth can affect the specific surface area of the material. Within the above limitation scope, on the surface of the cobalt substrate, the cobalt oxalate micron wire or micron rod precursor with stable structure can be grown and thus sufficient specific surface area can be provided.

[0013] In a preferable or optional example, the step S2 specifically includes: placing the cobalt oxalate precursor into a tubular furnace and introducing hydrogen into the tubular furnace and holding for a period of time, and then heating to a set temperature and then holding the temperature and cooling down to room temperature to obtain the cobalt intermediate.

[0014] In the step S2, the cobalt oxalate precursor is reduced with hydrogen into metal cobalt so as to obtain the cobalt intermediate with stable structure.

[0015] In a preferable or optional example, in the step S2, a gas volume flowrate of hydrogen is 5 to 100mL / min, and held for 20 to 40min and then heated. With a given gas flowrate, a reduction product can be quickly carried away.

[0016] In a preferable or optional example, in the step S2, with a heating rate of 1 to 10°C / min, the tubular furnace is heated to 100 to 550°C and held for 1 to 5h. Under high temperature, hydrogen has high reductibility and with limited temperature and holding time, the cobalt oxalate precursor can be completely reduced into the cobalt intermediate.

[0017] In a preferable or optional example, the concentration of the nickel salt solution is 10 to 30mM, and a solute of the nickel salt solution is selected from any one or combination of nickel sulfate, nickel nitrate and nickel chloride.

[0018] In a preferable or optional example, in the step S3, the reaction temperature of the epitaxial growth is 20 to 60°C and the reaction time is 20 to 80h.

[0019] In the step S3, by corrosion, reduction and ion exchange and the like, the cobalt-nickel nano structure is epitaxially grown on the surface of the cobalt intermediate of the cobalt, and the metal activity of the metal cobalt is strong. Therefore, the nickel ions can etch the metal cobalt to produce cobalt ions and in the presence of dissolved oxygen, the cobalt-nickel hydroxide is epitaxially grown on the surface of the cobalt substrate, so as to form a stable nickel-cobalt skin-core structure. The nickel salt type, the concentration, the reaction time, and the reaction temperature are important parameters for formation of the catalyst with nickel-cobalt skin-core structure. Within the above limitation scope, the nickel-cobalt skin-core structure catalyst with rich catalytic active sites and high catalytic activity.

[0020] A third aspect of the present disclosure provides an application of the above catalyst with nickel-cobalt skin-core structure to perform electrocatalytic oxidation of furan compound.

[0021] In a preferable or optional example, the catalyst with nickel-cobalt skin-core structure is used as a working electrode, the electrolyte for catalysis is a potassium hydroxide and / or sodium hydroxide solution, and the catalysis substrate is a furan compound which includes 2,5-furandimethanol, 5-hydroxymethylfurfural, 2,5-diformylfuran, 5-hydroxymethyl-2-furancarboxylic acid, 5-formyl-2-furancarboxylic acid, furfural, and furfuryl alcohol and the like.

[0022] In conclusion, compared with the prior arts, the present disclosure has the following beneficial effects.

[0023] In the present disclosure, the metal cobalt substrate in the catalyst with nickel-cobalt skin-core structure has high conductivity and the surface micronano cobalt component enables the electrochemical onset potential of the catalyst to be lower and with introduction of nickel component, the catalyst has high current density. The construction of the nickel-cobalt micronano structure greatly increases the reactive activity of the catalyst, and the prepared catalyst has excellent industrial application prospect.

[0024] In the present disclosure, the preparation method of the catalyst with nickel-cobalt skin-core structure is simple to operate and has strong repeatability and the catalyst with high activity can be obtained without using precious metal. The catalyst with micronano structure prepared by in-situ epitaxial growth can have better structural stability and larger specific surface area and thus expose more active sites, improving the activity of the catalyst.

[0025] In the present disclosure, the catalyst with nickel-cobalt skin-core structure has stable structure, many catalytic active sites and high catalytic activity and has high catalytic activity on the furan compound and can satisfy the current density desired for the industrial production. Therefore, the high-purity FDCA can be prepared.BRIEF DESCRIPTIONS OF THE DRAWINGS

[0026] FIG. 1 is a scanning electron microscopy (SEM) image illustrating a cobalt oxalate precursor according to an example 1 of the present disclosure. FIG. 2 is a SEM image illustrating a catalyst with nickel-cobalt skin-core structure according to an example 1 of the present disclosure. FIG. 3 is a transmission electron microscopy (TEM) image and a high-angle annular dark-field image illustrating a catalyst with nickel-cobalt skin-core structure according to an example 1 of the present disclosure. FIG. 4 is an element distribution diagram illustrating a catalyst with nickel-cobalt skin-core structure according to an example 1 of the present disclosure. FIG. 5 is a linear scanning voltammogram illustrating a catalyst with nickel-cobalt skin-core structure in an electrolyte according to an example 9 of the present disclosure. FIG. 6 is a result diagram illustrating electrocatalysis of HMF into FDCA by using a catalyst with nickel-cobalt skin-core structure through oxidation according to an example 9 of the present disclosure. DETAILED DESCRIPTIONS OF EMBODIMENTS

[0027] In order to make the above objects, features and advantages of the present disclosure clearer and more intelligible, the specific examples of the present disclosure will be detailed below in combination with drawings.

[0028] It should be understood that the terms in the present disclosure are used only to describe specific examples rather than to limit the present disclosure. Furthermore, the numerical range of the present disclosure shall be understood as further specifically disclosing each medium value between an upper limit and a lower limit of the range. Any stated value, or any medium value within the stated range, and any other stated value or each smaller range between the medium values within the above range shall also be included in the present disclosure. The upper limit and lower limit of these smaller ranges can be independently included in or excluded from the ranges.

[0029] Without departing from the spirit or scope of the present disclosure, various improvements and changes can be made to the specific examples of the present disclosure, which is apparent to those skilled in the arts. It is apparent for those skilled in the arts to obtain other examples from the specification of the present disclosure. The specification and the examples of the present disclosure are only illustrative.

[0030] A specific example of the present disclosure provides a catalyst with nickel-cobalt skin-core structure, which is prepared in the following method.

[0031] At step S1, a metal cobalt substrate is immersed in an oxalic acid solution, and by epitaxial growth, a cobalt oxalate micron wire or micron rod is grown on a surface of the metal cobalt substrate to obtain a cobalt oxalate precursor.

[0032] In a specific example, the metal cobalt substrate is selected from any one of metal cobalt foam, cobalt sheet, cobalt foil and cobalt net; a typical metal cobalt substrate is a foam cobalt. The metal cobalt substrate with three-dimensional structure can expose many active sites, helping increase the stability of the electrocaltalyst.

[0033] In a specific example, the solvent in the oxalic acid solution is water with a concentration of 6 to 30mM. The typical concentration includes 6mM, 8mM, 10mM, 12mM, 15mM, 20mM, 22mM, 25mM, 28mM and 30mM and so on. The molar ratio of the metal cobalt substrate to oxalic acid is 1:5.5 to 28.

[0034] In a specific example, in the step S1, the reaction time of the epitaxial growth is 0.25 to 4h, and the typical epitaxial growth time includes 0.25h, 0.5h, 1h, 2h, 2.5h, 3h and 4h and so on. The reaction temperature of the epitaxial growth is 20 to 80°C, and the typical epitaxial growth temperature includes 25°C, 35°C, 45°C, 50°C, 60°C and 80°C and so on. The epitaxial growth is carried out under mild condition and the preparation method is simple, making it easy to realize scale production.

[0035] At step S2, the cobalt oxalate precursor is placed into a hydrogen atmosphere for reduction to obtain a cobalt intermediate. The specific steps are as follows: placing the cobalt oxalate precursor into a tubular furnace, introducing hydrogen into the tubular furnace and holding for a period of time, and then heating to a set temperature and then holding the temperature and then cooling down to room temperature so as to obtain a cobalt intermediate with stable structure.

[0036] In a specific example, the gas volume flowrate of the hydrogen is 5 to 100 mL / min and held for 20 to 40 min and then heating is performed.

[0037] In a specific example, with a heating rate of 1 to 5°C / min, the tubular furnace is heated to 100 to 550°C and held for 1 to 5h. Under high temperature, the hydrogen has high reductibility, and with limited temperature and holding time, the cobalt oxalate precursor can be completely reduced into the cobalt intermediate.

[0038] At step S3, the cobalt intermediate is soaked in a nickel salt solution and a cobalt-nickel hydroxide is epitaxially grown on a surface of the cobalt micron wire or micron rod to obtain a catalyst with nickel-cobalt skin-core structure.

[0039] In a specific example, the solvent of the nickel salt solution is water and the solute is selected from any one or combination of nickel sulfate, nickel nitrate and nickel chloride, and preferably, from nickel nitrate.

[0040] In a specific example, the concentration of the nickel salt solution is 10 to 30mM, and the typical concentration includes 10M, 12M, 15M, 20M, 22M, 25M and 30M and so on.

[0041] In a specific example, in the step S3, the reaction temperature of the epitaxial growth is 20 to 60°C, the typical reaction temperature includes 20°C, 22°C, 25°C, 28°C, 30°C, 45°C and 58°C and so on. The reaction time of the epitaxial growth is 20 to 80h and the typical reaction time includes 20h, 24h, 30h, 38h, 40h, 60h and 80h and so on.

[0042] The above preparation method is simple to operate and has strong repeatability, and the catalyst with high activity can be obtained without using precious metal. The catalyst with micronano structure obtained by in-situ epitaxial growth has better structural stability and larger specific surface area and thus can expose more active sites, improving the activity of the catalyst.

[0043] The catalyst with nickel-cobalt skin-core structure obtained by the above method includes a metal cobalt substrate and a micronano structure grown on the metal cobalt substrate. The micronano structure includes a core layer and a skin layer wrapping the core layer. The core layer is a cobalt micron wire or micron rod. The skin layer is a cobalt-nickel hydroxide. The micronano structure exposes more specific surface area and more catalytic active sites than the metal cobalt substrate, cobalt micron wire and the cobalt micron bar, such that the catalyst has excellent activity. The cobalt substrate has high conductivity and the surface micronano cobalt component enables an electrochemical onset potential of the catalyst to be lower and with introduction of nickel component, the catalyst has high current density.

[0044] The specific examples of the present disclosure further provide an application of the above catalyst with nickel-cobalt skin-core structure to electrocatalytic oxidation reaction of furan compound. The specific application method is as below: using the above electrocatalyst as a working electrode, constructing a three-electrode system in an electrolytic cell, adding a basic solution containing biomass as electrolyte into the electrolytic cell, and immersing the working electrode in the electrolyte for electrocatalytic oxidation reaction of the biomass.

[0045] In a specific example, the electrolyte is a 0.5 to 2M potassium hydroxide and / or sodium hydroxide solution containing biomass and the solvent is water; the concentration of the furan compound is 1 to 1000mM, and the typical concentration includes 10 mM, 20 mM, 50 mM, 80 mM, 100 mM, 200 mM, 400 mM and 800 mM and so on. The typical biomass includes 2,5-furandimethanol, 5-hydroxymethylfurfural, 2,5-diformylfuran, 5-hydroxymethyl-2-furancarboxylic acid, 5-formyl-2-furancarboxylic acid, furfural, and furfuryl alcohol and the like.

[0046] In a specific example, the potential of the electrocatalytic oxidation is 1.35 to 1.8V vs.RHE. The typical potential includes 1.35 V vs.RHE, 1.45 V vs.RHE, 1.5 V vs.RHE, 1.55 V vs.RHE, 1.6 V vs.RHE and 1.8V vs.RHE and so on.

[0047] The catalyst with nickel-cobalt skin-core structure has stable structure, many catalytic active sites and high catalytic activity and has high catalytic activity on the furan compound and can satisfy the current density desired for the industrial production. Therefore, the high-purity FDCA can be prepared, which has very high economic value and good industrial application prospect.

[0048] The technical effects of the present disclosure are described with the specific examples below.Example 1

[0049] (1) A cobalt foam of 0.5×3cm 2< was taken and ultrasonically cleaned with deionized water and anhydrous ethanol respectively for 10min and dried for later use. (2) The cleaned cobalt foam was immersed in 50ml of 22mM oxalic acid solution for standing and underwent constant temperature reaction for 2h at the temperature of 50°C. After the completion of the reaction, the reaction product was taken out and cleaned with deionized water and then placed into an 80°C drying oven to be dried for 2h to obtain a cobalt oxalate precursor. The cobalt oxalate precursor has a micro-morphology as shown in FIG. 1. (3) The cobalt oxalate precursor was placed into a hydrogen atmosphere tubular furnace with a flowrate of 5ml / min and held for 30min, and then heated to 500°C at the heating rate of 5°C / min and held for 2h and then cooled down to room temperature so as to obtain a cobalt intermediate. (4) The cobalt intermediate was soaked in a 10mM nickel nitrate solution for standing, and underwent constant temperature reaction for 38h at the temperature of 25°C. After the completion of the reaction, the reaction product was cleaned with deionized water and then placed into an 80°C drying oven to be dried for 2h to obtain a catalyst with nickel-cobalt skin-core structure. The scanning electron microscopy image of the catalyst with nickel-cobalt skin-core structure is as shown in FIG. 2, the transmission electron microscopy image of the catalyst with nickel-cobalt skin-core structure is as shown in FIG. 3a, the high-angle annular dark field image of the catalyst with nickel-cobalt skin-core structure is as shown in FIG. 3b, and the element distribution diagram of the catalyst with nickel-cobalt skin-core structure is as shown in FIG. 4. Example 2

[0050] (1) A cobalt foam of 0.5×3cm 2< was taken and ultrasonically cleaned with deionized water and anhydrous ethanol respectively for 10min and dried for later use. (2) The cleaned cobalt foam was immersed in 50ml of 8mM oxalic acid solution for standing and underwent constant temperature reaction for 2h at the temperature of 80°C. After the completion of the reaction, the reaction product was taken out and cleaned with deionized water and then placed into an 80°C drying oven to be dried for 2h to obtain a cobalt oxalate precursor. (3) The cobalt oxalate precursor was placed into a hydrogen atmosphere tubular furnace with a flowrate of 5ml / min and held for 30min, and then heated to 500°C at the heating rate of 5°C / min and held for 2h and then cooled down to room temperature so as to obtain a cobalt intermediate. (4) The cobalt intermediate was soaked in a 20mM nickel nitrate solution for standing, and underwent constant temperature reaction for 38h at the temperature of 25°C. After the completion of the reaction, the reaction product was cleaned with deionized water and then placed into an 80°C drying oven to be dried for 2h to obtain a catalyst with nickel-cobalt skin-core structure. Example 3

[0051] (1) A cobalt foam of 0.5×3cm 2< was taken and ultrasonically cleaned with deionized water and anhydrous ethanol respectively for 10min and dried for later use. (2) The cleaned cobalt foam was immersed in 50ml of 22mM oxalic acid solution for standing and underwent constant temperature reaction for 2h at the temperature of 80°C. After the completion of the reaction, the reaction product was taken out and cleaned with deionized water and then placed into an 80°C drying oven to be dried for 2h to obtain a cobalt oxalate precursor. (3) The cobalt oxalate precursor was placed into a hydrogen atmosphere tubular furnace with a flowrate of 5ml / min and held for 30min, and then heated to 500°C at the heating rate of 5°C / min and held for 2h and then cooled down to room temperature so as to obtain a cobalt intermediate. (4) The cobalt intermediate was soaked in a 30mM nickel nitrate solution for standing, and underwent constant temperature reaction for 38h at the temperature of 25°C. After the completion of the reaction, the reaction product was cleaned with deionized water and then placed into an 80°C drying oven to be dried for 2h to obtain a catalyst with nickel-cobalt skin-core structure. Example 4

[0052] (1) A cobalt sheet of 0.5×3cm 2< was taken and ultrasonically cleaned with deionized water and anhydrous ethanol respectively for 10min and dried for later use. (2) The cleaned cobalt sheet was immersed in 50ml of 22mM oxalic acid solution for standing and underwent constant temperature reaction for 2h at the temperature of 80°C. After the completion of the reaction, the reaction product was taken out and cleaned with deionized water and then placed into an 80°C drying oven to be dried for 2h to obtain a cobalt oxalate precursor. (3) The cobalt oxalate precursor was placed into a hydrogen atmosphere tubular furnace with a flowrate of 5ml / min and held for 30min, and then heated to 500°C at the heating rate of 5°C / min and held for 2h and then cooled down to room temperature so as to obtain a cobalt intermediate. (4) The cobalt intermediate was soaked in a 30mM nickel nitrate solution for standing, and underwent constant temperature reaction for 38h at the temperature of 25°C. After the completion of the reaction, the reaction product was cleaned with deionized water and then placed into an 80°C drying oven to be dried for 2h to obtain a catalyst with nickel-cobalt skin-core structure. Example 5

[0053] (1) A cobalt foil of 0.5×3cm 2< was taken and ultrasonically cleaned with deionized water and anhydrous ethanol respectively for 10min and dried for later use. (2) The cleaned cobalt foil was immersed in 50ml of 8mM oxalic acid solution for standing and underwent constant temperature reaction for 2h at the temperature of 20°C. After the completion of the reaction, the reaction product was taken out and cleaned with deionized water and then placed into an 80°C drying oven to be dried for 2h to obtain a cobalt oxalate precursor. (3) The cobalt oxalate precursor was placed into a hydrogen atmosphere tubular furnace with a flowrate of 5ml / min and held for 30min, and then heated to 200°C at the heating rate of 5°C / min and held for 2h and then cooled down to room temperature so as to obtain a cobalt intermediate. (4) The cobalt intermediate was soaked in a 10mM nickel sulfate solution for standing, and underwent constant temperature reaction for 38h at the temperature of 25°C. After the completion of the reaction, the reaction product was cleaned with deionized water and then placed into an 80°C drying oven to be dried for 2h to obtain a catalyst with nickel-cobalt skin-core structure. Example 6

[0054] (1) A cobalt foam of 0.5×3cm 2< was taken and ultrasonically cleaned with deionized water and anhydrous ethanol respectively for 10min and dried for later use. (2) The cleaned cobalt foam was immersed in 50ml of 8mM oxalic acid solution for standing and underwent constant temperature reaction for 2h at the temperature of 35°C. After the completion of the reaction, the reaction product was taken out and cleaned with deionized water and then placed into an 80°C drying oven to be dried for 2h to obtain a cobalt oxalate precursor. (3) The cobalt oxalate precursor was placed into a hydrogen atmosphere tubular furnace with a flowrate of 5ml / min and held for 30min, and then heated to 300°C at the heating rate of 5°C / min and held for 2h and then cooled down to room temperature so as to obtain a cobalt intermediate. (4) The cobalt intermediate was soaked in a 10mM nickel sulfate solution for standing, and underwent constant temperature reaction for 24h at the temperature of 25°C. After the completion of the reaction, the reaction product was cleaned with deionized water and then placed into an 80°C drying oven to be dried for 2h to obtain a catalyst with nickel-cobalt skin-core structure. Example 7

[0055] (1) A cobalt sheet of 0.5×3cm 2< was taken and ultrasonically cleaned with deionized water and anhydrous ethanol respectively for 10min and dried for later use. (2) The cleaned cobalt sheet was immersed in 50ml of 16mM oxalic acid solution for standing and underwent constant temperature reaction for 2h at the temperature of 20°C. After the completion of the reaction, the reaction product was taken out and cleaned with deionized water and then placed into an 80°C drying oven to be dried for 2h to obtain a cobalt oxalate precursor. (3) The cobalt oxalate precursor was placed into a hydrogen atmosphere tubular furnace with a flowrate of 5ml / min and held for 40min, and then heated to 300°C at the heating rate of 5°C / min and held for 2h and then cooled down to room temperature so as to obtain a cobalt intermediate. (4) The cobalt intermediate was soaked in a 10mM nickel chloride solution for standing, and underwent constant temperature reaction for 20h at the temperature of 25°C. After the completion of the reaction, the reaction product was cleaned with deionized water and then placed into an 80°C drying oven to be dried for 2h to obtain a catalyst with nickel-cobalt skin-core structure. Example 8

[0056] (1) A cobalt foil of 0.5×3cm 2< was taken and ultrasonically cleaned with deionized water and anhydrous ethanol respectively for 10min and dried for later use. (2) The cleaned cobalt foil was immersed in 50ml of 8mM oxalic acid solution for standing and underwent constant temperature reaction for 2h at the temperature of 80°C. After the completion of the reaction, the reaction product was taken out and cleaned with deionized water and then placed into an 80°C drying oven to be dried for 2h to obtain a cobalt oxalate precursor. (3) The cobalt oxalate precursor was placed into a hydrogen atmosphere tubular furnace with a flowrate of 5ml / min and held for 40min, and then heated to 200°C at the heating rate of 5°C / min and held for 2h and then cooled down to room temperature so as to obtain a cobalt intermediate. (4) The cobalt intermediate was soaked in a 20mM nickel nitrate solution for standing, and underwent constant temperature reaction for 24h at the temperature of 25°C. After the completion of the reaction, the reaction product was cleaned with deionized water and then placed into an 80°C drying oven to be dried for 2h to obtain a catalyst with nickel-cobalt skin-core structure. Example 9

[0057] (1) The catalyst with nickel-cobalt skin-core structure prepared in the example 1 was mounted as an anode on an electrochemical working station. (2) The electrolyte was 20ml of 1M KOH solution, a platinum sheet was used for the electrode, and a mercury mercuric oxide electrode was used for a reference electrode. An area of the catalyst immersed in the electrolyte was 1×0.5cm 2< , and stirred by magneton at a rotation speed of 600rpm. (3) By using a linear scanning method of the electrochemical working station, an LSV curve was obtained, with a scanning rate of 5mV / s. (4) HMF was added to the electrolyte to increase the concentration to 10mM and the LSV curve was obtained with the scanning rate of 5mV / s. (5) HMF was added to the electrolyte to increase the concentration to 100mM and the LSV curve was obtained with the scanning rate of 5mV / s. The LSV curves in the above steps 3), 4) and 5) are as shown in FIG. 5. The results show the catalyst in the example 1 has a very high current density with its performance far surpassing the standard of the industrial current density. (6) In 5mL of electrolyte containing 1M KOH and 10mM HMF, electrolysis was performed with potentiostatic mode, with the electrolytic potential being 1.35V vs.RHE. The electrolytic result is as shown in FIG. 6, showing the catalyst in the example 1 has a very high HMF conversion rate and FDCA yield under low potential. The HMF conversion rate reaches 95.8% and the FDCA yield reaches 91.3%. Example 10

[0058] (1) The catalyst with nickel-cobalt skin-core structure prepared in the example 1 was mounted as an anode on an electrochemical working station. (2) The electrolyte was 20ml of 1M KOH solution, a platinum sheet was used for the electrode, and a mercury mercuric oxide electrode was used for a reference electrode. An area of the catalyst immersed in the electrolyte was 1×0.5cm 2< , and stirred by magneton at a rotation speed of 600rpm. (3) By using a linear scanning method of the electrochemical working station, an LSV curve was obtained, with a scanning rate of 5mV / s. (4) BHMF was added to the electrolyte to increase the concentration to 10mM and the LSV curve was obtained with the scanning rate of 5mV / s. (5) BHMF was added to the electrolyte to increase the concentration to 100mM and the LSV curve was obtained with the scanning rate of 5mV / s. (6) In 5mL of electrolyte containing 1M KOH and 10mM BHMF, electrolysis was performed with potentiostatic mode, with the electrolytic potential being 1.35V vs.RHE. The electrolytic result shows the catalyst in the example 1 has a HMF conversion rate of 93.6% and a FDCA yield of 90.2% under low potential. Example 11

[0059] This example differs from the example 9 in that: the catalyst with nickel-cobalt skin-core structure prepared in the example 2 is used as an anode of the electrochemical working station; in 5ml of electrolyte containing 1M KOH and 20mM 2,5-diformylfuran, electrolysis is performed with potentiostatic mode, with the electrolytic potential being 1.45 V vs.RHE. The electrolytic result shows the conversion rate of 2,5-diformylfuran is 94.8% and the FDCA yield is 89.9%.Example 12

[0060] This example differs from the example 9 in that: the catalyst with nickel-cobalt skin-core structure prepared in the example 3 is used as an anode of the electrochemical working station; in 5ml of electrolyte containing 1M KOH and 50mM 5-hydroxymethyl-2-furancarboxylic acid, electrolysis is performed with potentiostatics mode, with the electrolytic potential being 1.55 V vs.RHE. The electrolytic result shows the conversion rate of 5-hydroxymethyl-2-furancarboxylic acid is 90.4% and the FDCA yield is 86.8%.Example 13

[0061] This example differs from the example 9 in that: the catalyst with nickel-cobalt skin-core structure prepared in the example 4 is used as an anode of the electrochemical working station; in 5ml of electrolyte containing 1M KOH and 80mM 5-formyl-2-furancarboxylic acid, electrolysis is performed with potentiostatic mode, with the electrolytic potential being 1.6 V vs.RHE. The electrolytic result shows the conversion rate of 5-formyl-2-furancarboxylic acid is 94.7% and the FDCA yield is 91.0%.Example 14

[0062] This example differs from the example 9 in that: the catalyst with nickel-cobalt skin-core structure prepared in the example 5 is used as an anode of the electrochemical working station; in 5ml of electrolyte containing 1M KOH and 100mM furfural, electrolysis is performed with potentiostatic mode, with the electrolytic potential being 1.8 V vs.RHE. The electrolytic result shows the conversion rate of furfural is 88.6% and the FDCA yield is 84.3%.Example 15

[0063] This example differs from the example 9 in that: the catalyst with nickel-cobalt skin-core structure prepared in the example 6 is used as an anode of the electrochemical working station; in 5ml of electrolyte containing 1M KOH and 20mM furfuryl alcohol, electrolysis is performed with potentiostatic mode, with the electrolytic potential being 1.35 V vs.RHE. The electrolytic result shows the conversion rate of furfuryl alcohol is 89.2% and the FDCA yield is 86.1%.Example 16

[0064] This example differs from the example 9 in that: the catalyst with nickel-cobalt skin-core structure prepared in the example 7 is used as an anode of the electrochemical working station; in 5ml of electrolyte containing 1M KOH and 20mM HMF, electrolysis is performed with potentiostatic mode, with the electrolytic potential being 1.35 V vs.RHE. The electrolytic result shows the conversion rate of HMF alcohol is 93.9% and the FDCA yield is 90.2%.Example 17

[0065] This example differs from the example 9 in that: the catalyst with nickel-cobalt skin-core structure prepared in the example 8 is used as an anode of the electrochemical working station; in 5ml of electrolyte containing 1M KOH and 20mM BHMF, electrolysis is performed with potentiostatic mode, with the electrolytic potential being 1.35 V vs.RHE. The electrolytic result shows the conversion rate of BHMF alcohol is 95.9% and the FDCA yield is 92.3%.

[0066] Although the descriptions of the present disclosure are made as above, the scope of protection of the present disclosure is not limited hereto. Those skilled in the arts can, without departing from the spirit and scope of the present disclosure, make various changes and modifications, and such changes and modifications shall fall within the scope of protection of the present disclosure.

Examples

example 1

[0049] (1) A cobalt foam of 0.5×3cm 2FIG. 1. (3) The cobalt oxalate precursor was placed into a hydrogen atmosphere tubular furnace with a flowrate of 5ml / min and held for 30min, and then heated to 500°C at the heating rate of 5°C / min and held for 2h and then cooled down to room temperature so as to obtain a cobalt intermediate. (4) The cobalt intermediate was soaked in a 10mM nickel nitrate solution for standing, and underwent constant temperature reaction for 38h at the temperature of 25°C. After the completion of the reaction, the reaction product was cleaned with deionized water and then placed into an 80°C drying oven to be dried for 2h to obtain a catalyst with nickel-cobalt skin-core structure. The scanning electron microscopy image of the catalyst with nickel-cobalt skin-core structure is as shown in FIG. 2, the transmission electron microscopy image of the catalyst with nickel-cobalt skin-core structure is as shown in FIG. 3a, the high-angle annular dark field image of the ...

example 2

[0050] (1) A cobalt foam of 0.5×3cm 2< was taken and ultrasonically cleaned with deionized water and anhydrous ethanol respectively for 10min and dried for later use. (2) The cleaned cobalt foam was immersed in 50ml of 8mM oxalic acid solution for standing and underwent constant temperature reaction for 2h at the temperature of 80°C. After the completion of the reaction, the reaction product was taken out and cleaned with deionized water and then placed into an 80°C drying oven to be dried for 2h to obtain a cobalt oxalate precursor. (3) The cobalt oxalate precursor was placed into a hydrogen atmosphere tubular furnace with a flowrate of 5ml / min and held for 30min, and then heated to 500°C at the heating rate of 5°C / min and held for 2h and then cooled down to room temperature so as to obtain a cobalt intermediate. (4) The cobalt intermediate was soaked in a 20mM nickel nitrate solution for standing, and underwent constant temperature reaction for 38h at the temperature of 25°C. Aft...

example 3

[0051] (1) A cobalt foam of 0.5×3cm 2< was taken and ultrasonically cleaned with deionized water and anhydrous ethanol respectively for 10min and dried for later use. (2) The cleaned cobalt foam was immersed in 50ml of 22mM oxalic acid solution for standing and underwent constant temperature reaction for 2h at the temperature of 80°C. After the completion of the reaction, the reaction product was taken out and cleaned with deionized water and then placed into an 80°C drying oven to be dried for 2h to obtain a cobalt oxalate precursor. (3) The cobalt oxalate precursor was placed into a hydrogen atmosphere tubular furnace with a flowrate of 5ml / min and held for 30min, and then heated to 500°C at the heating rate of 5°C / min and held for 2h and then cooled down to room temperature so as to obtain a cobalt intermediate. (4) The cobalt intermediate was soaked in a 30mM nickel nitrate solution for standing, and underwent constant temperature reaction for 38h at the temperature of 25°C. Af...

Claims

1. A catalyst with nickel-cobalt skin-core structure, wherein the catalyst includes a metal cobalt substrate and a micronano structure grown on the metal cobalt substrate; the micronano structure includes a core layer and a skin layer wrapping the core layer; the core layer is a cobalt micron wire or micron rod, and the skin layer is a cobalt-nickel hydroxide.

2. A preparation method of the catalyst with nickel-cobalt skin-core structure of claim 1, wherein the method includes the following steps: at step S1, immersing a metal cobalt substrate in an oxalic acid solution, and by epitaxial growth, growing a stable cobalt oxalate micron wire or micron rod on a surface of the metal cobalt substrate to obtain a cobalt oxalate precursor; at step S2, placing the cobalt oxalate precursor into a hydrogen atmosphere for reduction to obtain a cobalt intermediate; and, at step S3, soaking the cobalt intermediate in a nickel salt solution and growing epitaxially a cobalt-nickel hydroxide on a surface of the cobalt micron wire or micron rod to obtain a catalyst with nickel-cobalt skin-core structure.

3. The preparation method of the catalyst with nickel-cobalt skin-core structure of claim 2, wherein in the step S1, a molar ratio of the metal cobalt substrate to oxalic acid is 1:5.5 to 28.

4. The preparation method of the catalyst with nickel-cobalt skin-core structure of claim 3, in the step S1, the reaction time of the epitaxial growth is 0.25 to 4h and the reaction temperature is 20 to 80°C.

5. The preparation method of the catalyst with nickel-cobalt skin-core structure of claim 2, wherein the step S2 specifically includes: placing the cobalt oxalate precursor into a tubular furnace and introducing hydrogen into the tubular furnace and holding for a period of time, and then heating to a set temperature and then holding the temperature and cooling down to room temperature to obtain the cobalt intermediate.

6. The preparation method of the catalyst with nickel-cobalt skin-core structure of claim 5, wherein in the step S2, a gas volume flowrate of hydrogen is 5 to 100mL / min, and held for 20 to 40min and then heated.

7. The preparation method of the catalyst with nickel-cobalt skin-core structure of claim 5, wherein in the step S2, with a heating rate of 1 to 10°C / min, the tubular furnace is heated to 100 to 550°C and held for 1 to 5h.

8. The preparation method of the catalyst with nickel-cobalt skin-core structure of claim 2, wherein in the step S3, the concentration of the nickel salt solution is 10 to 30mM, and a solute of the nickel salt solution is selected from any one or combination of nickel sulfate, nickel nitrate and nickel chloride.

9. The preparation method of the catalyst with nickel-cobalt skin-core structure of claim 8, wherein in the step S3, the reaction temperature of the epitaxial growth is 20 to 60°C and the reaction time is 20 to 80h.

10. An application of a catalyst with nickel-cobalt skin-core structure, wherein the application is to perform the catalyst with nickel-cobalt skin-core structure of claim 1 on electrocatalytic oxidation of furan compound.

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