CN117026274A

CN117026274A - Self-supporting anode catalyst, preparation thereof and application thereof in electrocatalytic preparation of adipic acid

Info

Publication number: CN117026274A
Application number: CN202310855256.XA
Authority: CN
Inventors: 陈勇; 刘福来; 石睿
Original assignee: Technical Institute of Physics and Chemistry of CAS
Current assignee: Technical Institute of Physics and Chemistry of CAS
Priority date: 2023-07-12
Filing date: 2023-07-12
Publication date: 2023-11-10

Abstract

The invention provides a self-supporting anode catalyst, a preparation method thereof and an application thereof in preparing adipic acid by electrocatalytic reaction. The anode catalyst comprises foamed metal as a conductive base material; hydrophobic graphite alkyne growing on the foam metal in situ, which is used for enriching and adsorbing hydrophobic reaction substrates; and a metal oxide grown in situ on the hydrophobic graphite alkyne as a catalytically active species. The anode catalyst is used for assembling a double-electrode flowing electrolytic cell, so that the KA oil can be efficiently catalyzed to oxidize to prepare adipic acid, and in addition, the co-production of high-purity hydrogen by a cathode is realized, so that the anode catalyst has high economic value and application value.

Description

Self-supporting anode catalyst, preparation thereof and application thereof in electrocatalytic preparation of adipic acid

Technical Field

The invention belongs to the field of electrochemical catalysis, and particularly relates to a self-supporting anode catalyst, a preparation method thereof and an application thereof in preparing adipic acid through electrocatalytic reaction.

Background

Adipic acid is the aliphatic dicarboxylic acid of greatest industrial application. It is the basic chemical raw material of various nylon polymers, medicines, lubricants, plasticizers and food additives, especially for preparing nylon-66 and polyurethane as monomer. The current industrial production of adipic acid mainly relies on a process of thermocatalytically oxidizing KA oil (a mixture of cyclohexanone and cyclohexanol) with copper/vanadium as a catalyst and 50-60% nitric acid as an oxidant. However, this method not only consumes a large amount of corrosive nitric acid, generates a large amount of acid-containing waste liquid, and simultaneously discharges Nitrogen Oxides (NO) _x And N ₂ O), wherein NO and NO ₂ Can be recovered to produce nitric acid, but N ₂ O can not be effectively recycled, becomes greenhouse gas which damages the ozone layer, and seriously affects the ecological environment. In order to achieve green and sustainable chemical production, it is therefore of great importance to develop an environmentally friendly adipic acid synthesis strategy that is free of oxidants, nitrogen oxide emissions.

The electrocatalytic technology has the advantages of high selectivity, easy reaction regulation, cleanness, economy and the like, and has shown remarkable application prospect in a plurality of fields. In the electrocatalytic reaction, the reaction meets the application requirements by adjusting the type of the reaction electrode, the relative size of the potential, the electrolyte system and other parameters, so that unnecessary side reactions are reduced, the utilization rate of raw materials is improved, the purity and the yield of products are increased, and the separation difficulty of the products is reduced. In particular, when the KA oil is selectively oxidized to adipic acid, water with rich sources and low cost is taken as a green solution and an oxygen source, active oxygen species (such as OH, O and OOH) generated in situ in the anodic oxidation process of the water are utilized to oxidize the KA oil to adipic acid selectively, so that the cost and environmental problems caused by using a strong oxidant can be avoided, and hydrogen is generated near the cathode. However, KA oil (especially cyclohexanone) is poorly soluble and slowly diffuses in aqueous solutions, making it difficult to enrich and adsorb on the catalyst surface to perform electrocatalytic oxidation reactions, resulting in poor catalytic activity. In addition, oxygen evolution reactions, which are competing reactions, will dominate at high current densities due to mass transfer limitations, thus inevitably reducing faraday efficiency and increasing reaction energy consumption.

Based on the above, development of an electrocatalyst capable of enriching and adsorbing hydrophobic reaction substrates and having high catalytic activity and selectivity is highly important for the development of preparing adipic acid by electrocatalytic KA oil.

Disclosure of Invention

In view of the above problems of the prior art, a first object of the present invention is to provide an anode catalyst that can be used for electrocatalytic reactions. The anode catalyst sequentially grows a double-layer structure of hydrophobic graphite alkyne and metal oxide on the surface of the conductive substrate material through twice in-situ growth, can more efficiently enrich and adsorb hydrophobic reaction substrates under the action of the hydrophobic graphite alkyne, and shows higher activity, selectivity and stability in the process of preparing adipic acid by electrocatalytic KA oil.

A second object of the present invention is to provide a method for preparing the anode catalyst as described above. The preparation method has mild conditions, can effectively grow the conductive hydrophobic graphite alkyne on the surface of the conductive substrate material, and is beneficial to improving the electrocatalytic activity.

A third object of the present invention is to provide the use of an anode catalyst as described above in the electrocatalytic production of adipic acid.

A fourth object of the present invention is to provide an electrocatalytic system for the production of adipic acid from KA oil comprising an anode catalyst as described above.

The fifth object of the invention is to provide a method for preparing adipic acid by electrocatalytic KA oil. The method has the advantages of high catalytic efficiency, good selectivity, little pollution, simple process and mild reaction conditions, can realize the effects of producing adipic acid at the anode and co-producing high-purity hydrogen at the cathode, and has high economic value and application value.

In order to achieve the first object, the present invention adopts the technical scheme that:

the invention discloses a self-supporting anode catalyst, which comprises

Foam metal as a conductive base material;

hydrophobic graphite alkyne growing on the foam metal in situ, which is used for enriching and adsorbing hydrophobic reaction substrates; and

metal oxides grown in situ on the hydrophobic graphite alkyne act as catalytically active species.

Aiming at the problems that the catalytic activity of the catalyst is low or a catalyst electrode is required to be constructed by using a binder (such as naphthol) in the prior art to oxidize KA oil to prepare adipic acid, the invention develops a self-supporting anode catalyst which can be used for preparing adipic acid by electrocatalytic KA oil. Secondly, the uneven charge distribution on the surface of the graphite alkyne endows a plurality of active sites and high intrinsic catalytic activity, so that the graphite alkyne has stronger capability of enriching and adsorbing KA oil. Therefore, KA oil can be enriched in the electrolyte more, which is beneficial to the improvement of catalytic efficiency.

Further, the metal foam includes, but is not limited to, one or more of iron foam, nickel foam, cobalt foam, copper foam, nickel iron foam, nickel copper foam, cobalt nickel foam, nickel molybdenum foam, nickel chromium aluminum foam, nickel iron chromium aluminum foam, copper tin foam, nickel aluminum foam.

Further, the metal foam is cut into (1-5) cm× (1-5) cm, and its thickness is 0.5-2mm.

Further, the metal oxide includes, but is not limited to, one or more of cobalt oxide, nickel oxide, iron oxide.

In order to achieve the second object, the present invention adopts the technical scheme that:

the invention discloses a preparation method for preparing an anode catalyst, which comprises the following steps:

1) Immersing the cleaned foam metal and copper foil in an acetone solution containing pyridine and tetramethyl ethylenediamine;

2) Adding hexaethynyl benzene into the acetone solution under inert atmosphere, and carrying out light-shielding reaction for 12-48 hours at 40-60 ℃ to obtain hydrophobic graphite alkyne growing on the foam metal in situ, wherein the hydrophobic graphite alkyne is marked as graphite alkyne/foam metal;

3) Dipping graphite alkyne/foam metal into alcohol solution, then dropwise adding transition metal salt solution and ammonia water into the alcohol solution in sequence, firstly reacting for 8-16h at 50-100 ℃, then transferring into a high-pressure reaction kettle, and continuously reacting for 1-12h at 100-200 ℃ to obtain metal oxide growing on the hydrophobic graphite alkyne in situ, namely the metal oxide/graphite alkyne/foam metal.

Further, the transition metal in the transition metal salt solution comprises one or more of cobalt nitrate, cobalt chloride, cobalt acetate, cobalt sulfate, nickel nitrate, nickel chloride, nickel acetate, nickel sulfate, ferric nitrate, ferric chloride, and ferrous sulfate.

Further, the cleaned foam metal can be performed with reference to the following steps:

firstly, ultrasonic treatment is carried out on foam metal in 1-3.0mol/L hydrochloric acid for 30min, then ultrasonic cleaning is carried out on the foam metal in deionized water and ethanol for multiple times in sequence, and finally, a blower is used for blow-drying for standby.

Further, the concentration of hexaethynylbenzene in the acetone solution in step 2 is 0.5-2mg/mL.

Further, after the completion of the light-shielding reaction in step 2, a washing step of the metal foam is further included, and illustratively, the metal foam may be washed by soaking in acetone, hot N, N-dimethylformamide (80 ℃) and acetone in order to remove the surface organic solvent and the oligomer.

Further, the graphite alkyne/foam metal includes, but is not limited to, one or more of graphite alkyne/foam iron, graphite alkyne/foam nickel, graphite alkyne/foam cobalt, graphite alkyne/foam copper, graphite alkyne/foam nickel iron, graphite alkyne/foam nickel copper, graphite alkyne/foam cobalt nickel, graphite alkyne/foam nickel molybdenum, graphite alkyne/foam nickel chromium aluminum, graphite alkyne/foam nickel iron chromium aluminum, graphite alkyne/foam copper tin, graphite alkyne/foam nickel aluminum.

In order to achieve the third object, the present invention adopts the technical scheme that:

the invention discloses an application of an anode catalyst prepared by the anode catalyst or the preparation method in preparing adipic acid by electrocatalytic reaction.

In order to achieve the fourth object, the present invention adopts the technical scheme that:

the invention discloses an electrocatalytic system for preparing adipic acid from KA oil, which comprises an anode catalyst, a cathode catalyst and electrolyte containing KA oil.

In the invention, the electrocatalytic system is a double-electrode flow electrolytic system, and the electrocatalytic system adopts a double-electrode flow electrolytic cell to carry out catalytic oxidation, wherein the anolyte is alkaline electrolyte containing KA oil, and the catholyte is alkaline electrolyte not containing KA oil.

Further, the anolyte contains 0.5-5mol/L of potassium hydroxide or sodium hydroxide plus 0.1-0.5mol/L of KA oil.

Further, the molar ratio of cyclohexanone to cyclohexanol in the KA oil may be one or more of 1:3, 1:2, 1:1, 2:1 and 3:1, with the anode catalyst having little difference in catalytic ability for KA oil of different ratios.

Further, the anolyte contains 1mol/L potassium hydroxide and 0.4mol/L KA oil (the molar ratio of cyclohexanone to cyclohexanol in KA oil is 1:1).

Further, the catholyte contains 1-5mol/L potassium hydroxide/sodium hydroxide, preferably 1mol/L potassium hydroxide.

Further, the cathode catalyst comprises one or more of nickel phosphide/metal foam, cobalt phosphide/metal foam, iron phosphide/metal foam, copper phosphide/metal foam.

Further, the cathode catalyst can be prepared by adopting the following steps, and the cathode catalyst obtained by other methods has little influence on the catalytic performance of the whole electrocatalytic system, and comprises the following specific steps:

placing the cleaned foam metal into an aqueous solution containing 1mmol/L metal nitrate hydrate or metal chloride hydrate and 5-20mmol/L urea, loading into a reaction kettle, treating for 8-15h at 100-140 ℃ in an oven, taking out the foam metal after cooling to room temperature, sequentially cleaning for multiple times by deionized water and ethanol, and drying in a vacuum drying oven;

weighing 500-1000mg of sodium hypophosphite, placing the sodium hypophosphite at one end of a porcelain boat, placing the treated foam metal at the other end of the porcelain boat, transferring the porcelain boat to the middle part in a quartz tube, finally installing the quartz tube on a tube furnace, placing the sodium hypophosphite at an air inlet position, opening an argon valve after the device is built, continuously introducing argon for protection by small airflow, and setting a heating program of the tube furnace: firstly, raising the temperature to 2 ℃ per minute, keeping the temperature for 1-4 hours after the isothermal temperature reaches 300-500 ℃, cooling to room temperature, taking out the porcelain boat, washing with deionized water for multiple times, and finally, putting the porcelain boat into a vacuum drying oven for drying to obtain the metal phosphide/foam metal.

Further, the metal in the metal nitrate hydrate or the metal chloride hydrate comprises one or more of iron, cobalt, nickel and copper.

In order to achieve the fifth object, the present invention adopts the technical scheme that:

the invention discloses a method for preparing adipic acid by electrocatalytic KA oil, which comprises the steps of assembling the electrocatalytic system into a double-electrode flowing electrolytic cell, and applying voltage to perform electrocatalytic reaction;

wherein KA oil is oxidized at the anode to generate adipic acid, and water is reduced at the cathode to generate hydrogen.

Further, the applied voltage is 1-3V and the reaction temperature is 25-80 ℃.

In a specific embodiment, after the electrocatalytic reaction, the method further comprises the steps of separating and purifying adipic acid, wherein the specific steps are as follows:

neutralizing the electrolyzed reaction solution with hydrochloric acid to pH=4-6, decolorizing with activated carbon, performing reduced pressure distillation to remove partial water, cooling the concentrated solution, recrystallizing at 0-5deg.C for 12-24 hr to completely precipitate adipic acid crystal, and vacuum drying to obtain adipic acid crystal.

The invention has the beneficial effects that:

the anode catalyst prepared by the invention, namely the metal oxide/graphite alkyne/foam metal, shows higher performance of preparing adipic acid by electrocatalytic KA oil oxidation, particularly when the anode catalyst is cobaltosic oxide/graphite alkyne/foam nickel, the current reaches 1A, the cell pressure is only 2.0V, and the yield of the adipic acid is more than 80%.

The invention provides an electrocatalytic system for preparing high-purity adipic acid by KA oil selective oxidation, which realizes the preparation of adipic acid by the electrocatalytic KA oil oxidation with high activity, high selectivity and high stability by a one-step method, and has the advantages of simple process, easily obtained raw materials, mild reaction conditions and simple separation and purification operation; in addition, the cathode co-production of high-purity hydrogen is realized, so that the invention has high economic value and application value.

Drawings

The following describes the embodiments of the present invention in further detail with reference to the drawings.

Fig. 1 shows a raman spectrum of the cobaltosic oxide/graphite alkyne/foam nickel anode catalyst prepared in example 1.

Figure 2 shows the XRD spectrum of the cobaltosic oxide/graphite alkyne/nickel foam anode catalyst prepared in example 1.

Fig. 3 shows an SEM image of the tricobalt tetraoxide/graphite alkyne/foam nickel anode catalyst prepared in example 1.

Fig. 4 shows a TEM image of the tricobalt tetraoxide/graphite alkyne/foam nickel anode catalyst prepared in example 1.

Fig. 5 shows EDS spectra of the cobaltosic oxide/graphite alkyne/nickel foam anode catalyst prepared in example 1.

Fig. 6 shows a physical and structural schematic diagram of the assembled two-electrode flow cell of the present invention.

FIG. 7 shows LSV curves for electrolyzed water and electrolyzed KA oil in example 1.

FIG. 8 shows the electrolyte before and after electrolysis in example 1 ¹ H NMR spectrum.

Fig. 9 shows hydrogen production rate and faraday efficiency of the cathode at different current densities in example 1.

FIG. 10 shows the stability profile of the electrolysis in example 1.

FIG. 11 shows the adipic acid product of example 1 ¹ H NMR spectrum.

FIG. 12 shows the adipic acid product of example 1 ¹³ C NMR spectrum.

Fig. 13 shows a Raman spectrum of the nickel oxide/graphite alkyne/cobalt foam anode catalyst prepared in example 2.

Fig. 14 shows an SEM image of the nickel oxide/graphite alkyne/foamed cobalt anode catalyst prepared in example 2.

Fig. 15 shows a TEM image of the nickel oxide/graphite alkyne/foamed cobalt anode catalyst prepared in example 2.

FIG. 16 shows LSV curves of the anode catalyst prepared in example 1 and example 2 for electrolysis of KA oil.

Fig. 17 shows Raman spectra of the graphite alkyne/nickel foam anode catalyst prepared in comparative example 1.

Fig. 18 shows an XRD spectrum of the tricobalt tetraoxide/nickel foam anode catalyst prepared in comparative example 1.

Fig. 19 shows LSV curves of the anode catalyst electrolytic KA oil prepared in example 1 and comparative example 1.

Fig. 20 shows open-circuit voltage decay curves of the anode catalysts prepared in example 1 and comparative example 1.

Figure 21 shows the differential capacitance curve of the tricobalt tetraoxide/graphite alkyne/foam nickel anode catalyst of example 1.

Fig. 22 shows the differential capacitance curve of the tricobalt tetraoxide/nickel foam anode catalyst of comparative example 1.

Fig. 23 shows LSV curves of the anode catalyst electrolytic KA oil prepared in example 1 and comparative example 2.

Detailed Description

In order to more clearly illustrate the present invention, the present invention will be further described with reference to preferred embodiments and the accompanying drawings. It should be understood that the described embodiments are merely some, but not all, embodiments of the invention. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.

Example 1

(1) Preparation of cobaltosic oxide/graphite alkyne/foam nickel anode catalyst

Firstly cutting foam nickel into 3cm multiplied by 3cm, performing ultrasonic treatment in 1.0mol/L hydrochloric acid for 30min, then sequentially performing ultrasonic cleaning in deionized water and ethanol for 3 times, and finally drying by a blower for later use; the cleaned foam nickel and 3 pieces of 3cm×3cm copper foil were placed in a three-necked flask, and 90mL of acetone, 5mL of pyridine and 1mL of tetramethyl ethylenediamine were added, respectively, to impregnate the foam metal and the copper foil therein. 100mg of hexaethynyl benzene was added to the above mixed solution under nitrogen protection, and reacted at 50℃for 24 hours in the absence of light. And cooling the reaction liquid, taking out the foam metal, soaking and washing the foam metal with acetone, hot N, N-dimethylformamide (80 ℃) and acetone in sequence to remove the surface organic solvent and the oligomer, and naturally airing the foam metal to obtain the graphite alkyne/foam nickel.

Graphite alkyne/nickel foam was added to a eggplant-shaped bottle containing 24mL of ethanol and 1.2mL of deionized water, the graphite alkyne/nickel foam was immersed therein, followed by dropwise addition of 1.2mL of 0.2mol/L cobalt acetate, and then dropwise addition of 0.5mL of aqueous ammonia. Heating at 80 ℃ for 12 hours, transferring to a reaction kettle, reacting at 150 ℃ for 3 hours, cooling to room temperature, washing with ethanol, and naturally airing to obtain the cobaltosic oxide/graphite alkyne/foam nickel.

FIG. 1 shows a Raman spectrum that the prepared material contains both tricobalt tetraoxide and graphite alkyne, indicating successful preparation of tricobalt tetraoxide and graphite alkyne; XRD of fig. 2 shows that tricobalt tetroxide in the prepared material is spinel structure; the SEM images of fig. 3 show the vertical growth of graphite alkyne nanoplatelets on nickel foam. The TEM image of fig. 4 shows that the cobaltosic oxide nanoparticles are uniformly distributed on the graphite alkyne nanoplatelets. The EDS energy spectrum of FIG. 5 shows that the prepared material mainly contains three elements of cobalt, carbon and oxygen.

(2) Preparation of cobalt phosphide/foam nickel cathode

Ultrasonic treating foamed nickel with the thickness of 1.5mm in 1mol/L hydrochloric acid for 30min, sequentially ultrasonic cleaning in deionized water and ethanol for multiple times, and finally drying by a blower for later use; placing the cleaned foam nickel into an aqueous solution containing 1mmol/L cobalt nitrate hydrate and 10mmol/L urea, loading into a reaction kettle, treating for 12 hours at 120 ℃ in an oven, taking out the foam nickel after cooling to room temperature, sequentially cleaning for a plurality of times by deionized water and ethanol, and drying in a vacuum drying oven;

800mg of sodium hypophosphite is weighed and placed at one end of a porcelain boat, the treated foam nickel is placed at the other end of the porcelain boat, then the porcelain boat is transferred to the middle part in a quartz tube, the quartz tube is mounted on a tube furnace, and the sodium hypophosphite is positioned at an air inlet position. After the device is built, an argon valve is opened, and argon is continuously introduced into the device for protection by small airflow. Finally, a heating program of the tube furnace is set up: first, the temperature is raised by 2 ℃ per minute, and the temperature is maintained for 2 hours after reaching 350 ℃ and the mixture is cooled to room temperature. And (5) taking out, washing for multiple times by using deionized water, and finally putting into a vacuum drying oven for drying to obtain cobalt phosphide/foam nickel.

(3) Preparation of adipic acid coupling hydrogen production by electrolysis of KA oil in double-electrode flow electrolytic cell

The two-electrode flow cell is used for electrolysis (namely, cobaltosic oxide/graphite alkyne/foam nickel is used as an anode, the working area of the electrode is 3cm multiplied by 3cm, a cobalt phosphide/foam nickel sheet is used as a cathode, and the working area of the electrode is 3cm multiplied by 3 cm). The anolyte is 1mol/L potassium hydroxide+0.4mol/L KA oil (the molar ratio of cyclohexanone to cyclohexanol in KA oil is 1:1), and flows into the anolyte tank at a flow rate of 3 mL/min; the catholyte was 1mol/L potassium hydroxide and flowed into the anolyte at a flow rate of 3 mL/min. The anolyte and catholyte tanks were connected by a 3.5cm x 3.5cm proton exchange membrane (Nafion 117), and the electrolyzer was as shown in figure 6.

FIG. 7 is a LSV plot of electrolyzed water and electrolyzed KA oil, as can be seenWhen the current reaches 1A, the voltage required for electrolyzing KA oil is only 2.0V and is far lower than 2.5V of electrolyzed water. FIG. 8 shows the electrolyte before and after electrolysis ¹ HNMR spectra, in which it is seen that the KA oil is substantially completely converted after completion of electrolysis (100% conversion of KA oil and 80% yield of adipic acid). FIG. 9 is a graph showing the hydrogen production rate and Faraday efficiency of the cathode at various current densities, wherein the Faraday efficiency of the cathode for hydrogen production is greater than 90%; fig. 10 is a stability curve of long-term electrolysis, and it can be seen from the figure that the catalyst can realize stable electrolysis for 100 hours, indicating that the catalyst has good stability.

(4) Separation and purification of adipic acid product

Neutralizing the electrolyzed reaction solution with hydrochloric acid until weak acidity appears (pH=5), and then decoloring with activated carbon to obtain adipic acid mixed solution; vacuum distilling (pressure of minus 0.1MPa; temperature of 50deg.C), removing part of water, and concentrating adipic acid content to 65-85wt%; cooling the concentrated solution to 0-5 ℃ at a speed of 1 ℃/min, and keeping for 12 hours to completely separate adipic acid crystals. Drying in vacuo gave adipic acid crystals, the product being determined by means of FIGS. 11 and 12.

Example 2

(1) Preparation of nickel oxide/graphite alkyne/foam cobalt anode catalyst

Firstly cutting foamed cobalt into 3cm multiplied by 3cm, performing ultrasonic treatment in 1.0mol/L hydrochloric acid for 30min, then sequentially performing ultrasonic cleaning in deionized water and ethanol for 3 times, and finally drying by a blower for later use; the cleaned cobalt foam and 3 pieces of 3cm x 3cm copper foil were placed in a three-necked flask, and 90mL of acetone, 5mL of pyridine and 1mL of tetramethyl ethylenediamine were added, respectively, to impregnate the metal foam and the copper foil. 100mg of hexaethynyl benzene was added to the above mixed solution under nitrogen protection, and reacted at 50℃for 24 hours in the absence of light. And cooling the reaction liquid, taking out the foam metal, soaking and washing the foam metal with acetone, hot N, N-dimethylformamide (80 ℃) and acetone in sequence to remove the surface organic solvent and the oligomer, and naturally airing the foam metal to obtain the graphite alkyne/foam cobalt.

Graphite alkyne/cobalt foam was added to an eggplant-shaped bottle containing 24mL of ethanol and 1.2mL of deionized water, the graphite alkyne/cobalt foam was immersed therein, followed by dropwise addition of 1.2mL of 0.2mol/L nickel acetate, and then dropwise addition of 0.5mL of aqueous ammonia. Heating at 80 ℃ for 12h, transferring to a reaction kettle, reacting at 150 ℃ for 3h, cooling to room temperature, washing with ethanol, and naturally airing to obtain nickel oxide/graphite alkyne/cobalt foam.

The preparation of cobalt phosphide/nickel foam cathode and the construction of the double electrode flow cell were consistent with example 1.

FIG. 13 Raman spectrum shows that the prepared material contains both nickel oxide and graphite alkyne, indicating successful preparation of nickel oxide and graphite alkyne; the SEM images of fig. 14 show the vertical growth of graphite alkyne nanoplatelets on cobalt foam. The TEM image of fig. 15 shows that nickel oxide nanoparticles are uniformly distributed on the graphite alkyne nanoplatelets.

FIG. 16 is a LSV graph of the electrolyzed KA oil, which shows that when the current reaches 1A, the voltage required to electrolyze KA oil is only 2.05V, slightly higher than the voltage value tested in example 1.

Comparative example 1

The comparative example preparation process is referred to in example 1, except that no metal oxide or no graphite alkyne is grown in situ.

(1) The preparation method of the graphite alkyne/foam nickel anode catalyst comprises the following steps:

firstly cutting foam nickel into 3cm multiplied by 3cm, performing ultrasonic treatment in 1.0mol/L hydrochloric acid for 30min, then sequentially performing ultrasonic cleaning in deionized water and ethanol for 3 times, and finally drying by a blower for later use; the cleaned foam nickel and 3 pieces of 1cm×3cm copper foil were placed in a three-necked flask, and 90mL of acetone, 5mL of pyridine and 1mL of tetramethyl ethylenediamine were added, respectively, to impregnate the foam metal and the copper foil therein. 100mg of hexaethynyl benzene was added to the above mixed solution under nitrogen protection, and reacted at 50℃for 24 hours in the absence of light. And cooling the reaction liquid, taking out the foam metal, soaking and washing the foam metal with acetone, hot N, N-dimethylformamide (80 ℃) and acetone in sequence to remove the surface organic solvent and the oligomer, and naturally airing the foam metal to obtain the graphite alkyne/foam nickel.

The raman spectrum of fig. 17 shows that the prepared material contains both graphite alkyne, indicating that graphite alkyne was successfully prepared.

(2) The preparation method of the cobaltosic oxide/foam nickel anode catalyst comprises the following steps:

firstly cutting foam nickel into 3cm multiplied by 3cm, performing ultrasonic treatment in 1.0mol/L hydrochloric acid for 30min, then sequentially performing ultrasonic cleaning in deionized water and ethanol for 3 times, and finally drying by a blower for later use; the washed nickel foam was added to an eggplant-shaped bottle containing 24mL of ethanol and 1.2mL of deionized water, the nickel foam was immersed therein, then 1.2mL of 0.2mol/L cobalt acetate was added dropwise, and then 0.5mL of aqueous ammonia was added dropwise. Heating at 80 ℃ for 12 hours, transferring to a reaction kettle, reacting at 150 ℃ for 3 hours, cooling to room temperature, washing with ethanol, and naturally airing to obtain the cobaltosic oxide/foam nickel.

The SEM image of fig. 18 shows that the material prepared is tricobalt tetraoxide.

Double-electrode electrolysis was performed using the tricobalt tetraoxide/graphite alkyne/nickel foam of example 1 or the graphite alkyne/nickel foam of comparative example 1 or the tricobalt tetraoxide/nickel foam of comparative example 2 as an anode, an electrode working area of 3cm×3cm, and a cobalt phosphide/nickel foam sheet as a cathode (see example 1 for the preparation process), and an electrode working area of 3cm×3 cm. The anolyte is 1mol/L potassium hydroxide+0.4mol/L KA oil (the molar ratio of cyclohexanone to cyclohexanol in KA oil is 1:1), and flows into the anolyte tank at a flow rate of 3 mL/min; the catholyte was 1mol/L potassium hydroxide and flowed into the anolyte at a flow rate of 3 mL/min. The anolyte and catholyte cells were connected by a 3.5cm x 3.5cm proton exchange membrane (Nafion 117).

FIG. 19 shows LSV curves of various catalysts for the electrolysis of KA oil, and it can be seen from the graphs that the catalyst using tricobalt tetraoxide/graphite alkyne/nickel foam as anode has the best catalytic activity when the current reaches 1A, the voltage required for the electrolysis of KA oil is only 2.0V, which is lower than 2.36V of graphite alkyne/nickel foam and 2.25V of tricobalt tetraoxide/nickel foam.

To elucidate the reasons for the improved catalytic activity of tricobalt tetraoxide/graphite alkyne/nickel foam, the adsorption behavior of the anode catalyst on KA oil was studied, and the anode catalysts prepared in example 1 and comparative example 1 were tested for open circuit voltage decay curves (fig. 20), which reflect how much KA oil was adsorbed on Helmholtz layer on the electrode surface, the more adsorption, the more voltage drop. It can be seen from the figure that the open circuit voltage of the tricobalt tetraoxide/graphite alkyne/nickel foam anode catalyst was reduced by 10mV, well below 3mV for tricobalt tetraoxide/nickel foam, when KA oil was added. Fig. 21 and 22 are differential capacitance curves for the tricobalt tetraoxide/graphite alkyne/foamed nickel anode catalyst and tricobalt tetraoxide/foamed nickel catalyst, respectively. When KA molecules are adsorbed on the electrode surface instead of water molecules, the dielectric constant in the electric double layer is reduced and the effective thickness is increased. According to the inverse relation of capacitance and effective thickness, the interface capacitance will decrease. After KA oil is added, the capacitance of the cobaltosic oxide/graphite alkyne/foam nickel anode catalyst is obviously reduced (figure 21), and the cobaltosic oxide/foam nickel catalyst is not obviously changed (figure 22), which shows that the graphite alkyne can effectively promote the enrichment and adsorption of KA oil molecules on the electrode surface, thereby improving the catalytic activity.

Comparative example 2

(1) Preparation of cobaltosic oxide/graphene/foam nickel anode catalyst

The graphene powder was added to an eggplant-shaped bottle containing 24mL ethanol and 1.2mL deionized water, and sonicated for 30 minutes to mix well. Subsequently, 1.2mL of 0.2mol/L cobalt acetate was added dropwise, followed by dropwise addition of 0.5mL of aqueous ammonia. Heating at 80 ℃ and stirring for 12 hours, transferring to a reaction kettle, reacting for 3 hours at 150 ℃, cooling to room temperature, washing with ethanol, and naturally airing to obtain the cobaltosic oxide/graphene.

100mg of cobaltosic oxide/graphene powder is weighed and dissolved in 6.6mL of ethanol, 5.8mL of water and 0.6mL of Nafion mixed solution, and ultrasonic treatment is carried out for 30 minutes to uniformly mix the powder. Then uniformly coating on 3cm multiplied by 3cm foam nickel to make the loading of cobaltosic oxide/graphene powder be 2mg/cm ² And obtaining the cobaltosic oxide/graphene/foam nickel anode catalyst.

The double-electrode electrolysis is carried out by taking cobaltosic oxide/graphite alkyne/foam nickel or cobaltosic oxide/graphene/foam nickel as an anode, taking a cobalt phosphide/foam nickel sheet as a cathode, and taking the working area of the electrode as 3cm multiplied by 3cm (see the preparation process of example 1). The anolyte is 1mol/L potassium hydroxide+0.4mol/L KA oil (the molar ratio of cyclohexanone to cyclohexanol in KA oil is 1:1), and flows into the anolyte tank at a flow rate of 3 mL/min; the catholyte was 1mol/L potassium hydroxide and flowed into the anolyte at a flow rate of 3 mL/min. The anolyte and catholyte cells were connected by a 3.5cm x 3.5cm proton exchange membrane (Nafion 117).

FIG. 23 is a LSV plot of KA oil electrolysis with different catalysts, from which it can be seen that the catalyst with tricobalt tetraoxide/graphite alkyne/nickel foam as anode requires only 2.0V for KA oil electrolysis when the current reaches 1A, which is lower than 2.36V for tricobalt tetraoxide/graphene/nickel foam anode catalyst, indicating that tricobalt tetraoxide/graphite alkyne/nickel foam anode catalyst has better catalytic activity than tricobalt tetraoxide/graphene/nickel foam anode catalyst, further illustrating the advantages of this in situ growth catalyst strategy.

It should be understood that the foregoing examples of the present invention are provided merely for clearly illustrating the present invention and are not intended to limit the embodiments of the present invention, and that various other changes and modifications may be made therein by one skilled in the art without departing from the spirit and scope of the present invention as defined by the appended claims.

Claims

1. A self-supporting anode catalyst, characterized in that the anode catalyst comprises

Foam metal as a conductive base material;

2. The anode catalyst of claim 1, wherein the metal foam comprises one or more of iron foam, nickel foam, cobalt foam, copper foam, nickel iron foam, nickel copper foam, cobalt nickel foam, nickel molybdenum foam, nickel chromium aluminum foam, nickel iron chromium aluminum foam, copper tin foam, nickel aluminum foam.

3. The anode catalyst of claim 1, wherein the metal oxide comprises one or more of cobalt oxide, nickel oxide, iron oxide.

4. A method for preparing an anode catalyst according to any one of claims 1 to 3, comprising the steps of:

immersing the cleaned foam metal and copper foil in an acetone solution containing pyridine and tetramethyl ethylenediamine;

adding hexaethynyl benzene into the acetone solution under inert atmosphere, and carrying out light-shielding reaction for 12-48 hours at 40-60 ℃ to obtain hydrophobic graphite alkyne growing on the foam metal in situ, wherein the hydrophobic graphite alkyne is marked as graphite alkyne/foam metal;

dipping graphite alkyne/foam metal into alcohol solution, then dropwise adding transition metal salt solution and ammonia water into the alcohol solution in sequence, firstly reacting for 8-16h at 50-100 ℃, then transferring into a reaction kettle, and continuously reacting for 1-12h at 100-200 ℃ to obtain metal oxide growing on the hydrophobic graphite alkyne in situ, and marking the metal oxide/graphite alkyne/foam metal.

5. The method according to claim 4, wherein the transition metal in the transition metal salt solution comprises one or more of cobalt nitrate, cobalt chloride, cobalt acetate, cobalt sulfate, nickel nitrate, nickel chloride, nickel acetate, nickel sulfate, iron nitrate, iron chloride, and ferrous sulfate.

6. Use of an anode catalyst according to any one of claims 1-3 or prepared by a method according to any one of claims 4 or 5 in the electrocatalytic production of adipic acid.

7. An electrocatalytic system for preparing adipic acid from KA oil, comprising the anode catalyst according to any one of claims 1-3 or the anode catalyst, the cathode catalyst and the electrolyte comprising KA oil prepared by the preparation method according to any one of claims 4 or 5.

8. The electrocatalytic system of claim 7, wherein the cathode catalyst comprises one or more of nickel phosphide/metal foam, cobalt phosphide/metal foam, iron phosphide/metal foam, copper phosphide/metal foam.

9. A method for preparing adipic acid by electrocatalytic KA oil, which is characterized in that the electrocatalytic system of any one of claims 7 or 8 is assembled into a double-electrode flow electrolytic cell, and voltage is applied to perform electrocatalytic reaction;

10. The method of claim 9, wherein the applied voltage is 1-3V and the reaction temperature is 25-80 ℃.