A method for preparing cation-doped nickel-iron amorphous compound

Abstract

The invention provides a method for preparing a cation-doped nickel-iron amorphous compound, wherein the cation-doped nickel-iron amorphous compound is prepared by etching with a self-template method, and the method (self-template method) avoids the stacking of nanosheets, prevents the occurrence of problems such as active site masking, is conducive to the full exposure of the surface area of ​​the active site of the catalytic material and the full contact with the electrolyte, and cation doping can improve the adsorption capacity of the material to hydrogen intermediates and oxygen intermediates, and effectively improve the catalytic performance of the material. The method has certain universality, and the type and content of the doping element can be adjusted according to different requirements to cope with different catalytic environments. In addition, the nanomaterial is used as a furfuryl alcohol oxidation catalyst, showing excellent catalytic performance and having broad application prospects. The mass fraction of the doped cation in the product is precisely controllable, and the method has the advantages of simple equipment, easy control, good process repeatability, stable product quality, etc.

Description

Technical Field

[0001] The invention belongs to the field of catalysis and relates to a method for preparing a cation-doped nickel-iron amorphous compound using an organic metal framework MIL-88B (Fe) as a precursor. Background Art

[0002] Faced with the increasingly severe environmental pollution and environmental restoration problems and the accelerated consumption of non-renewable energy such as fossil fuels, the development and storage technology of new energy has become an urgent need for the sustainable development of the current society. Therefore, finding a clean, renewable, safe, efficient and environmentally friendly new energy is of particular significance to the future development of human society. As a new energy source, hydrogen energy has the advantages of cleanliness, high combustion heat, storability, cheapness and easy availability, so it is recognized as one of the most ideal and potential energy sources to replace fossil fuels. Electrolysis of water to produce hydrogen energy is one of the more mature, promising and cleanest methods to obtain hydrogen energy. Generally speaking, the water splitting reaction includes two half reactions, namely the hydrogen evolution reaction (HER) and the oxygen evolution reaction (OER). The oxygen evolution reaction (OER) occurring at the anode is slow, resulting in low overall energy conversion efficiency, and the reaction product (O2) does not have a high value. Traditional water electrolyzers produce H2 and O2 at the same time, so an additional process is required to achieve gas separation to prevent the safety hazards of H2 / O2 mixing. In addition, the potential formation of reactive oxygen species (ROS) may cause degradation of the electrolytic cell diaphragm, resulting in premature damage to the electrolysis device. The oxidation reaction kinetics of furfuryl alcohol (FFA) is more favorable than the oxygen evolution reaction, and the oxidation product furoic acid (FA) at the anode is more valuable than oxygen. Therefore, the oxidation reaction of furfuryl alcohol to furoic acid at the anode of the electrolytic cell is used to replace the oxygen evolution reaction.

[0003] In the selection of catalytic materials, so far, precious metal platinum (Pt) and iridium (Ir) based electrocatalysts are still used as benchmark HER and OER electrocatalysts, respectively. However, the high cost and scarcity of platinum and iridium severely limit their widespread application in water electrolysis to produce hydrogen. Nickel-iron amorphous compounds have great prospects as bifunctional electrocatalysts that catalyze HER and OER simultaneously in alkaline solutions due to the earth abundance of their constituent elements and excellent durability. At present, although nickel-iron amorphous compounds show excellent OER electrocatalysts, their HER activity is extremely poor in alkaline solutions, resulting in a very high overall water splitting voltage in alkaline electrolyte solutions. Cation doping can improve the adsorption capacity of materials for hydrogen intermediates and oxygen intermediates, thereby effectively improving the overall water splitting performance. The structure grown by the self-template method can fully expose the active sites, and in response to different catalytic environments and catalytic substances, different cations can be selected for element doping to further improve the catalytic efficiency. Summary of the invention

[0004] In order to solve the problems of how to effectively improve the catalytic activity of nickel-iron amorphous compounds and fully expose active sites, the present invention proposes a method for preparing cation-doped nickel-iron amorphous compounds.

[0005] In order to achieve the above object, the present invention provides the following technical solutions:

[0006] (1) Preparation of precursor MIL-88B (Fe): ultrasonically disperse a certain amount of anhydrous ferric chloride in an appropriate amount of dimethylformamide (DMF), stir evenly, then add a certain amount of terephthalic acid (BDC), and stir until completely dissolved; drop a small amount of sodium hydroxide solution of a certain concentration into the obtained uniform solution while stirring, and then seal and stir for a certain period of time; transfer all the solution to a reactor, seal it in an outer shell, and then transfer it to an oven, keep the temperature constant for a certain period of time, and cool it naturally; centrifuge and wash the product in the reactor lining with deionized water and anhydrous ethanol, then disperse the product in deionized water, freeze the obtained dispersion, and finally transfer it to a freeze dryer for freeze drying to obtain the precursor MIL-88B (Fe);

[0007] Preferably, in the step (1), the amount of anhydrous ferric chloride is 160-970 mg, the amount of dimethylformamide is 5-30 mL, the amount of terephthalic acid is 170-1000 mg, the concentration of the sodium hydroxide solution is 1.9-2.1 mol / L, the amount is 0.4-2.4 mL, the sealed stirring time is 3-5 min, the volume of the reactor used is 25-100 mL, the temperature of the oven is selected to be 95-120° C., and the insulation time is 11-13 h;

[0008] (2) Preparation of cation-doped nickel-iron amorphous compound: weigh a certain amount of the precursor MIL-88B (Fe) obtained in step (1) and put it into a round-bottom flask, add an appropriate amount of deionized water, and ultrasonically disperse it for a period of time to fully disperse it, and stir it for a period of time to form a uniform solution; weigh a certain amount of nickel nitrate hexahydrate, an appropriate amount of cyclohexamethylenetetramine and a small amount of anhydrous sodium citrate and put them into a beaker, add an appropriate amount of deionized water, and stir until they are completely dissolved to form a clear and transparent solution; pour the solution in the above beaker into the round-bottom flask containing the precursor MIL-88B (Fe) dispersion, ultrasonically disperse it, and stir it until it is uniform; then add a small amount of pre-configured salt solution of the doping element under stirring, continue to stir until it is uniformly mixed, seal it and heat it in an oil bath pot, keep the temperature constant for a certain period of time, keep the solution still during this period, do not stir it, and after naturally cooling to room temperature, centrifuge and wash the obtained product, then disperse the product in deionized water, freeze the obtained dispersion, and finally transfer it to a freeze dryer for freeze drying to obtain a cation-doped nickel-iron amorphous compound;

[0009] Preferably, in the step (2), the amount of the precursor MIL-88B (Fe) is 10 to 70 mg, the amount of deionized water used to disperse the precursor MIL-88B (Fe) is 5 to 25 mL, the time for ultrasonic dispersion is 5 to 15 min, the time for stirring evenly is 5 to 15 min, the amount of nickel nitrate hexahydrate is 140 to 750 mg, the amount of cyclohexamethylenetetramine is 70 to 350 mg, the amount of sodium citrate is 13 to 65 mg, the amount of deionized water used to dissolve the above drugs is 4 to 20 mL, the concentration of the doping cation of the doping element salt solution is 2 to 10 mmol / L, the amount is 1 to 25 mL, the temperature of the oil bath is selected to be 75 to 95° C., and the insulation time is 4.5 to 6 h.

[0010] The advantages and beneficial effects of the present invention are:

[0011] 1. The present invention proposes a method for preparing a cation-doped nickel-iron amorphous compound, in which the nickel-iron amorphous compound is prepared by self-template etching. Compared with a single nanosheet or nanoflower ball structure, this method (self-template method) avoids the stacking of nanosheets and prevents the problem of active site masking, which is beneficial to the full exposure of the active surface area of ​​the catalytic material and the full contact with the electrolyte. In addition, the self-template method has the characteristics of fewer reaction steps and no need for additional templates.

[0012] 2. The present invention proposes a method for preparing a cation-doped nickel-iron amorphous compound. Cation doping enables the material to have good adsorption capacity for both hydrogen intermediates and oxygen intermediates, effectively improving the catalytic performance of the material.

[0013] 3. The present invention proposes a method for preparing a cation-doped nickel-iron amorphous compound. The mass fraction of the cation in the product is precisely controllable. The method has the advantages of simple equipment, easy control, good process repeatability, and stable product quality.

[0014] 4. The present invention proposes a method for preparing a cation-doped nickel-iron amorphous compound. The method has a certain universality and can adjust the type and content of the doping elements according to different requirements to cope with different catalytic environments.

[0015] 5. The present invention proposes a method for preparing a cation-doped nickel-iron amorphous compound. The nanomaterial is used as a furfuryl alcohol oxidation catalyst, exhibits excellent catalytic performance, and has broad application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 : A flow chart of a method for preparing a cation-doped nickel-iron amorphous compound proposed by the present invention;

[0017] Figure 2: A scanning electron microscope photograph of the precursor MIL-88B (Fe) obtained in Example 1 of the present invention;

[0018] Figure 3 : A scanning electron microscope photograph of the ruthenium-doped nickel-iron amorphous compound obtained in Example 1 of the present invention;

[0019] Figure 4 : X-ray diffraction pattern of the ruthenium-doped nickel-iron amorphous compound obtained in Example 1 of the present invention;

[0020] Figure 5 : Scanning electron microscope energy spectrum analysis diagram of the ruthenium-doped nickel-iron amorphous compound obtained in Example 1 of the present invention;

[0021] Figure 6 : Table of percentage of element contents of the ruthenium-doped nickel-iron amorphous compound obtained in Example 1 of the present invention;

[0022] Figure 7 : A scanning electron microscope photograph of the cerium-doped nickel-iron amorphous compound obtained in Example 2 of the present invention;

[0023] Figure 8 : Table of element contents in percentage of the cerium-doped nickel-iron amorphous compound obtained in Example 2 of the present invention;

[0024] Fig. 9 : A scanning electron microscope photograph of the cobalt-doped nickel-iron amorphous compound obtained in Example 3 of the present invention;

[0025] Fig.10 : Table of percentage of element contents of the cobalt-doped nickel-iron amorphous compound obtained in Example 3 of the present invention;

[0026] Fig.11 : Performance diagram of the ruthenium-doped nickel-iron amorphous compound obtained in Example 1 of the present invention used as a catalyst for oxidizing furfuryl alcohol. DETAILED DESCRIPTION

[0027] The present invention is described in detail below in conjunction with the accompanying drawings and embodiments, but the protection scope of the present invention is not limited to the following embodiments.

[0028] Embodiment 1:

[0029] (1) Preparation of precursor MIL-88B (Fe): 160 mg of anhydrous ferric chloride was ultrasonically dispersed in 5 mL of dimethylformamide (DMF), and then 170 mg of terephthalic acid (BDC) was added and stirred until completely dissolved; 0.4 mL of 1.9 mol / L sodium hydroxide solution was added dropwise to the obtained uniform solution under stirring, and then sealed and stirred for 3 min; the entire solution was transferred to a 25 mL reactor, sealed in an outer shell, and then transferred to an oven, kept at 95°C for 11.5 h, and cooled naturally; the product in the reactor lining was centrifuged and washed with deionized water and anhydrous ethanol, and then the product was dispersed in deionized water, the obtained dispersion was frozen, and finally transferred to a freeze dryer for freeze drying to obtain the precursor MIL-88B (Fe);

[0030] (2) Preparation of ruthenium-doped nickel-iron amorphous compound: Weigh 24 mg of the precursor MIL-88B (Fe) obtained in step (1) and put it into a round-bottom flask, add 10 mL of deionized water, and ultrasonically disperse it for 10 min to fully disperse it, and stir it for 15 min to form a uniform solution; weigh 280 mg of nickel nitrate hexahydrate, 140 mg of cyclohexamethylenetetramine, and 26 mg of anhydrous sodium citrate and put them into a beaker, add 8 mL of deionized water, and stir until it is completely dissolved to form a clear and transparent solution; pour the solution in the beaker into the flask containing the precursor MIL-88B (Fe); The L-88B (Fe) dispersion was ultrasonically dispersed in a round-bottom flask and stirred until uniform; then, a small amount of 5 mL of ruthenium trichloride solution with a pre-configured concentration of 9.7 mmol / L was added under stirring, and stirring was continued until uniformly mixed. After sealing, the oil bath was heated at 95°C for 4.5 hours. During this period, the solution was kept still and could not be stirred. After naturally cooling to room temperature, the obtained product was centrifuged and washed, and then the product was dispersed in deionized water. The obtained dispersion was frozen and finally transferred to a freeze dryer for freeze drying to obtain a ruthenium-doped nickel-iron amorphous compound.

[0031] Embodiment 2:

[0032] (1) Preparation of precursor MIL-88B (Fe): 490 mg of anhydrous ferric chloride was ultrasonically dispersed in 15 mL of dimethylformamide (DMF), and then 500 mg of terephthalic acid (BDC) was added and stirred until completely dissolved; 1.2 mL of 2.1 mol / L sodium hydroxide solution was added dropwise to the obtained uniform solution under stirring, and then sealed and stirred for 4 min; the entire solution was transferred to a reactor, sealed in an outer shell, and then transferred to an oven, kept at a constant temperature of 105°C for 12.5 h, and then cooled naturally; the product in the reactor lining was centrifuged and washed with deionized water and anhydrous ethanol, and then the product was dispersed in deionized water, the obtained dispersion was frozen, and finally transferred to a freeze dryer for freeze drying to obtain the precursor MIL-88B (Fe);

[0033] (2) Preparation of cerium-doped nickel-iron amorphous compound: 18 mg of the precursor MIL-88B (Fe) obtained in step (1) was weighed and placed in a round-bottom flask, 7.5 mL of deionized water was added, and ultrasonic dispersion was performed for 12 min to fully disperse it, and stirred for 5 min to form a uniform solution; 210 mg of nickel nitrate hexahydrate, 105 mg of cyclohexamethylenetetramine, and 20 mg of anhydrous sodium citrate were weighed and placed in a beaker, 6 mL of deionized water was added, and stirred until completely dissolved to form a clear and transparent solution; the solution in the beaker was poured into the flask containing the precursor MIL-88B (Fe). -88B(Fe) dispersion was ultrasonically dispersed in a round-bottom flask and stirred until uniform; then, a small amount of 3.5 mL of cerium nitrate solution with a pre-configured concentration of 8.66 mmol / L was added under stirring, and stirring was continued until uniformly mixed. After sealing, the oil bath was heated at 85°C for 5.5 hours, during which the solution was kept still without stirring. After naturally cooling to room temperature, the obtained product was centrifuged and washed, and then the product was dispersed in deionized water. The obtained dispersion was frozen and finally transferred to a freeze dryer for freeze drying to obtain a cerium-doped nickel-iron amorphous compound.

[0034] Embodiment 3:

[0035] (1) Preparation of precursor MIL-88B (Fe): 970 mg of anhydrous ferric chloride was ultrasonically dispersed in 30 mL of dimethylformamide (DMF), and then 1000 mg of terephthalic acid (BDC) was added and stirred until completely dissolved; 2.4 mL of 2 mol / L sodium hydroxide solution was added dropwise to the obtained uniform solution under stirring, and then sealed and stirred for 5 min; the entire solution was transferred to a reactor, sealed in an outer shell, and then transferred to an oven, kept at a constant temperature of 100°C for 12 h, and cooled naturally; the product in the reactor lining was centrifuged and washed with deionized water and anhydrous ethanol, and then the product was dispersed in deionized water, the obtained dispersion was frozen, and finally transferred to a freeze dryer for freeze drying to obtain the precursor MIL-88B (Fe);

[0036] (2) Preparation of cobalt-doped nickel-iron amorphous compound: Weigh 12 mg of the precursor MIL-88B (Fe) obtained in step (1) and put it into a round-bottom flask, add 5 mL of deionized water, and ultrasonically disperse it for 15 min to fully disperse it, and stir it for 10 min to form a uniform solution; weigh 140 mg of nickel nitrate hexahydrate, 70 mg of cyclohexamethylenetetramine, and 13 mg of anhydrous sodium citrate and put them into a beaker, add 4 mL of deionized water, and stir until it is completely dissolved to form a clear and transparent solution; pour the solution in the beaker into the precursor MIL -88B(Fe) dispersion was ultrasonically dispersed in a round-bottom flask and stirred until uniform; then, a small amount of 2.5 mL of cobalt nitrate solution with a pre-configured concentration of 7.65 mmol / L was added under stirring, and stirring was continued until uniformly mixed. After sealing, the oil bath was heated at 90°C for 5 hours. During this period, the solution was kept still and could not be stirred. After naturally cooling to room temperature, the obtained product was centrifuged and washed, and then the product was dispersed in deionized water. The obtained dispersion was frozen and finally transferred to a freeze dryer for freeze drying to obtain a cobalt-doped nickel-iron amorphous compound.

[0037] Although the above describes the specific implementation methods of the present invention in combination with the embodiments, it is not intended to limit the scope of protection of the present invention. Technical personnel in the relevant field should understand that various modifications or variations that can be made by technical personnel in the field without creative work on the basis of the technical solution of the present invention are still within the scope of protection of the present invention.

Claims

1. A method for preparing a cation-doped nickel-iron amorphous compound, characterized in that: The following steps are involved: (1) Preparation of precursor MIL-88B (Fe): ultrasonically disperse a certain amount of anhydrous ferric chloride in an appropriate amount of dimethylformamide (DMF), stir evenly, then add a certain amount of terephthalic acid (BDC), and stir until completely dissolved; drop a small amount of sodium hydroxide solution of a certain concentration into the obtained uniform solution while stirring, and then seal and stir for a certain period of time; The entire solution was transferred to a reactor, sealed in an outer shell, and then transferred to an oven, kept at a constant temperature for a certain period of time, and cooled naturally; the product in the reactor lining was centrifugally washed with deionized water and anhydrous ethanol, and then the product was dispersed in deionized water, the obtained dispersion was frozen, and finally transferred to a freeze dryer for freeze drying to obtain the precursor MIL-88B (Fe); Wherein: in the step (1), the amount of anhydrous ferric chloride is 160-970 mg, the amount of dimethylformamide is 5-30 mL, the amount of terephthalic acid is 170-1000 mg, the concentration of sodium hydroxide solution is 1.9-2.1 mol / L, the amount is 0.4-2.4 mL, the sealed stirring time is 3-5 min, the volume of the reactor used is 25-100 mL, the temperature of the oven is selected to be 95-120 °C, and the insulation time is 11-13 h; (2) Preparation of cation-doped nickel-iron amorphous compound: weigh a certain amount of the precursor MIL-88B (Fe) obtained in step (1) and put it into a round-bottom flask, add an appropriate amount of deionized water, and ultrasonically disperse it for a period of time to fully disperse it, and stir it for a period of time to form a uniform solution; weigh a certain amount of nickel nitrate hexahydrate, an appropriate amount of cyclohexamethylenetetramine and a small amount of anhydrous sodium citrate and put them into a beaker, add an appropriate amount of deionized water, and stir until they are completely dissolved to form a clear and transparent solution; pour the solution in the above beaker into the round-bottom flask containing the precursor MIL-88B (Fe) dispersion, ultrasonically disperse it, and stir it until it is uniform; then add a small amount of pre-configured salt solution of the doping element under stirring, continue to stir until it is uniformly mixed, seal it and heat it in an oil bath pot, keep the temperature constant for a certain period of time, keep the solution still during this period, do not stir it, and after naturally cooling to room temperature, centrifuge and wash the obtained product, then disperse the product in deionized water, freeze the obtained dispersion, and finally transfer it to a freeze dryer for freeze drying to obtain a cation-doped nickel-iron amorphous compound; Wherein: in the step (2), the amount of the precursor MIL-88B (Fe) is 10-70 mg, the amount of deionized water used to disperse the precursor MIL-88B (Fe) is 5-25 mL, the time for ultrasonic dispersion is 5-15 min, the time for stirring evenly is 5-15 min, the amount of nickel nitrate hexahydrate is 140-750 mg, the amount of cyclohexamethylenetetramine is 70-350 mg, the amount of sodium citrate is 13-65 mg, the amount of deionized water used to dissolve the above drugs is 4-20 mL, the concentration of the doping cation of the doping element salt solution is 2-10 mmol / L, the amount is 1-25 mL, the temperature of the oil bath is selected to be 75-95 ° C, and the insulation time is 4.5-6 h.

Images