CN110449185A - A kind of preparation method and application of self-supporting bimetallic CoNi-MOF nano-array composite catalyst - Google Patents

Abstract

The invention discloses a kind of preparation method of self-supporting bimetallic CoNi-MOF nano-array composite catalyst and the applications restored based on the catalyst in electrochemistry nitrogen, belong to nanocomposite, electrochemical catalysis technical field.It has main steps that dipicolimic acid 2, nickel nitrate, lithium hydroxide, ammonium persulfate are raw material with 2, and the nano-array composite material of cobalt piece load C o-MOF is made；The nano-array composite material is impregnated into nickel nitrate-ethanol solution, self-supporting bimetallic CoNi-MOF nano-array composite catalyst is made.The catalyst preparation low cost of raw materials, preparation process is simple, and energy consumption of reaction is low, has wide prospects for commercial application.The catalyst is used for efficient electro-catalysis nitrogen reduction reaction, has good electrochemistry nitrogenase activity.

Description

A kind of preparation method of self-supporting bimetallic CoNi-MOF nanoarray composite catalyst and application

technical field

The invention relates to a preparation method of a self-supporting bimetallic CoNi-MOF nano-array composite catalyst and an application of electrocatalytic nitrogen reduction reaction based on the catalyst, belonging to the technical fields of nano-composite materials and electrochemical catalysis.

Background technique

NH ₃ is one of the most important chemicals at present, and its annual output ranks first among all kinds of chemicals. China is also a big industrial country in the synthesis of NH _3. As a high energy consumption industry, the energy consumed by the synthesis of NH ₃ industry accounts for 1% of the global total. -2%, the downstream products of NH ₃ are mainly chemical fertilizers, and other important chemical products such as synthetic fibers, explosives, industrial fuels, etc. More than 140 million tons of NH ₃ are produced annually by the Haber-Bosch process, and demand is growing. Ammonia plays an important role in supporting the global population due to its role as an essential precursor in fertilizer production. However, this process is energy demanding and associated with low efficiency. Typical reactions require temperatures and pressures of about 500°C and >200 atm and use of Fe/Ru catalysts. Thus, it is estimated globally that about 2% of the world energy budget is devoted to _NH3 production. Considering the current limitations of fossil fuels and the challenges of global climate change, it is particularly important to explore catalytic reactions for the synthesis _of NH under mild conditions.

The room-temperature synthesis of _NH3 by electrochemical reduction of _N2 , using natural water as the hydrogen source, with mild reaction conditions and voltage regulation, has attracted widespread attention. The core of this synthesis is an efficient and stable catalyst. For this reason, it is a very promising and challenging task to develop a catalyst with a simple and economical synthesis process and a high-efficiency and stable catalytic performance.

SUMMARY OF THE INVENTION

One of the technical tasks of the present invention is to provide a self-supporting bimetallic CoNi-MOF nano-array composite catalyst in order to make up for the deficiencies of the prior art, that is, a cobalt sheet-supported Ni ²⁺ doped Co-MOF nano-array composite catalyst. The preparation method has the advantages of simple preparation process, low raw material cost, low reaction energy consumption and industrial application prospect.

The second technical task of the present invention is to provide the use of the composite material, that is, the self-supporting bimetallic CoNi-MOF nano-array composite catalyst is used for high-efficiency electrocatalytic nitrogen reduction reaction, and the composite material has good electrocatalytic nitrogen fixation activity and electrochemical performance. stability.

For achieving the above object, the technical scheme adopted in the present invention is as follows:

1. A kind of preparation method of self-supporting bimetallic CoNi-MOF nano-array composite catalyst

(1) Preparation of Co-MOF/Co nanoarray composites After co-dissolving 1.5-2.0 mmol of 2,6-pyridinedicarboxylic acid and 2.0-4.5 mmol of lithium hydroxide in 5-8 mL of water, 1.2-3.0 mmol of Ammonium sulfate to obtain clear ammonium persulfate-2,6-pyridinedicarboxylic acid alkali solution;

The activated 1cm×1cm cobalt sheet was immersed in ammonium persulfate-2,6-pyridinedicarboxylic acid alkali solution, reacted at room temperature for 2-3 hours, washed with water 3 times, and the product was a cobalt sheet-supported Co-MOF nanoarray. Composite material, namely Co-MOF/Co nanoarray composite material;

(2) Preparation of self-supporting bimetallic CoNi-MOF nanoarray composite catalyst The Co-MOF/Co nanoarray composite material was dipped into 10 mL ethanol solution containing 1.5-4.0 g nickel nitrate, and reacted at room temperature for 1.5-2 h; Rinse with water and ethanol for 3 times, and dry to constant weight at 85°C to prepare a cobalt sheet supported Ni ²⁺ doped Co-MOF nanoarray composite material, that is, a self-supporting bimetallic CoNi-MOF nanoarray composite catalyst.

The activated 1cm×1cm cobalt sheet is prepared by 180W ultrasonic for 2-4min in dilute hydrochloric acid with a mass fraction of 1.5% to remove surface impurities, and then washed with distilled water and ethanol respectively.

The Co-MOF belongs to a metal-organic framework, the chemical formula is [Co ₂ (PDCA) ₂ (H ₂ O) ₅ ]n, and PDCA is an anion of 2,6-pyridinedicarboxylate; a structure of Co-MOF nanosheets The unit is composed of two Co(II) ions, two PDCA anions and five H ₂ O molecules; the PDCA has the following structural formula:

2. Application of the self-supporting bimetallic CoNi-MOF nanoarray composite catalyst prepared by the described preparation method for electrocatalytic nitrogen reduction to ammonia

(1) Electrocatalytic nitrogen reduction Connect the H-type two-chamber electrolytic cell to the electrochemical workstation, separate the two chambers with Nafion 115 proton exchange membrane, and add 30 mL of PBS buffer solution with a concentration of 0.1 M to both chambers; The supported bimetallic CoNi-MOF nanoarray composite catalyst was used as the working electrode, the Ag/AgCl reference electrode was placed in the electrolyte of the cathodic chamber; the platinum sheet auxiliary electrode was placed in the electrolyte of the anodic chamber; After N ₂ for 10 min, set an external voltage of -0.6 to -1.8 V for electrocatalytic nitrogen reduction, take the reaction solution of the catalytic reaction for 2 h, and measure the concentration of NH ₄ ⁺ in the reaction solution to test the bimetallic CoNi-MOF nanosheet catalyst based on Nitrogen reduction performance;

(2) To draw a standard curve, use ammonium chloride and 0.1M PBS buffer solution with pH=7 to prepare a series of NH ₄ ⁺ standard solutions with concentrations of 0.01 mM, 0.02 mM, 0.03 mM, 0.05 mM and 0.1 mM;

Pipette 2mL series of standard solutions, add 2mL NaOH solution with a concentration of 1.0M, 1mL NaClO solution with a concentration of 0.05M, and 0.2mL sodium nitroferricyanide solution with a mass fraction of 1% in turn, shake well, 25 ℃ Place for 2h, detect the absorbance peak value at the wavelength of 653nm of the solution with a UV-vis spectrophotometer, draw the standard curve of absorbance-concentration, that is, A-c, to obtain the standard curve equation;

The 1.0M NaOH solution contains 5% salicylic acid and 5% sodium citrate in mass fraction;

(3) Calculation of Nitrogen Reduction to Ammonia Yield Measure the concentration of NH ₄ ⁺ in the reaction solution, pipette 2mL of the reaction solution for catalytic reaction 2h, replace the 2mL standard solution in step (2), and calculate the ammonia yield according to the standard curve equation .

3. The above-mentioned self-supporting bimetallic CoNi-MOF nanoarray composite catalyst was used for electrocatalytic reduction of nitrogen to ammonia. When the applied voltage was -1.2V vs Ag/AgCl, the ammonia yield was 37.8-43.2μg _NH3 ·h ^-1 · mg ^-1 _catalyst , the Faradaic efficiency was 23.8-30.1%, indicating the material's high electrocatalytic nitrogen fixation activity.

The beneficial technical effects of the present invention are as follows:

(1) The self-supporting bimetallic CoNi-MOF nano-array composite catalyst obtained by the present invention has the advantages of simple preparation process, simple and easy control, high product preparation efficiency and easy industrialization.

(2) The self-supporting bimetallic CoNi-MOF nano-array composite catalyst prepared in the present invention does not require pyrolysis-oxidation, and completely retains the porous CoNi-MOF, which has a large specific surface area and exposes more active sites; , the material is a Co-MOF nanoarray composite material supported by cobalt sheets supported by Ni ²⁺ . The synergistic effect of Ni ²⁺ and Co ²⁺ in the composite material increases the catalytic activity of the composite material for nitrogen fixation into ammonia, and the electrocatalytic NRR production at room temperature. The yield of ammonia is higher.

Detailed ways

The present invention will be further described below in conjunction with the embodiments, but the protection scope of the present invention is not limited to the embodiments, and changes made by professionals in the field to the technical solutions of the present invention should all fall within the protection scope of the present invention.

Embodiment 1 A kind of preparation method of self-supporting bimetallic CoNi-MOF nano-array composite catalyst

(1) Preparation of Co-MOF/Co nanoarray composites After co-dissolving 1.5 mmol of 2,6-pyridinedicarboxylic acid and 2.0 mmol of lithium hydroxide in 5 mL of water, 1.2 mmol of ammonium persulfate was added to obtain clear persulfuric acid Ammonium-2,6-pyridinedicarboxylic acid alkali solution;

The activated 1cm×1cm cobalt sheet was immersed in an alkaline solution of ammonium persulfate-2,6-pyridinedicarboxylic acid, reacted at room temperature for 2 hours, and washed with water for 3 times to obtain a cobalt sheet-supported Co-MOF nanoarray composite material. , namely Co-MOF/Co nanoarray composites;

(2) Preparation of self-supporting bimetallic CoNi-MOF nanoarray composite catalyst The Co-MOF/Co nanoarray composite material was immersed in 10 mL ethanol solution containing 1.5 g nickel nitrate, and reacted at room temperature for 1.5 h; deionized water and ethanol were used in turn. Rinse 3 times and dry to constant weight at 85°C to prepare a Co-MOF nano-array composite material supported by cobalt sheet supported Ni ²⁺ , namely a self-supporting bimetallic CoNi-MOF nano-array composite catalyst.

The activated 1cm×1cm cobalt sheet was prepared by 180W ultrasonic for 2min in dilute hydrochloric acid with a mass fraction of 1.5% to remove surface impurities, and then washed with distilled water and ethanol respectively.

The Co-MOF belongs to a metal-organic framework, the chemical formula is [Co ₂ (PDCA) ₂ (H ₂ O) ₅ ]n, and PDCA is an anion of 2,6-pyridinedicarboxylate; a structure of Co-MOF nanosheets The unit is composed of two Co(II) ions, two PDCA anions and five H ₂ O molecules; the PDCA has the following structural formula:

Embodiment 2 A kind of preparation method of self-supporting bimetallic CoNi-MOF nano-array composite catalyst

(1) Preparation of Co-MOF/Co nanoarray composites After co-dissolving 1.7 mmol of 2,6-pyridinedicarboxylic acid and 3.2 mmol of lithium hydroxide in 6.5 mL of water, 2.1 mmol of ammonium persulfate was added to obtain a clear Ammonium sulfate-2,6-pyridinedicarboxylic acid alkali solution;

The activated 1cm×1cm cobalt sheet was immersed in ammonium persulfate-2,6-pyridinedicarboxylic acid alkali solution, reacted at room temperature for 2.5 hours, and washed with water for 3 times to obtain a cobalt sheet-supported Co-MOF nanoarray composite. material, namely Co-MOF/Co nanoarray composite;

(2) Preparation of self-supporting bimetallic CoNi-MOF nanoarray composite catalyst The Co-MOF/Co nanoarray composite material was immersed in 10 mL ethanol solution containing 2.7 g nickel nitrate, and reacted at room temperature for 1.2 h; deionized water and ethanol were used in turn. Rinse 3 times and dry to constant weight at 85°C to prepare a Co-MOF nano-array composite material supported by cobalt sheet supported Ni ²⁺ , namely a self-supporting bimetallic CoNi-MOF nano-array composite catalyst.

The activated 1cm×1cm cobalt sheet was prepared by 180W ultrasonic for 3 minutes in dilute hydrochloric acid with a mass fraction of 1.5% to remove surface impurities, and then washed with distilled water and ethanol respectively.

The structure of the Co-MOF is the same as that of Example 1.

Embodiment 3 A kind of preparation method of self-supporting bimetallic CoNi-MOF nano-array composite catalyst

(1) Preparation of Co-MOF/Co nanoarray composites After co-dissolving 2.0 mmol of 2,6-pyridinedicarboxylic acid and 4.5 mmol of lithium hydroxide in 8 mL of water, 3.0 mmol of ammonium persulfate was added to obtain clear persulfuric acid Ammonium-2,6-pyridinedicarboxylic acid alkali solution;

The activated 1cm×1cm cobalt sheet was immersed in an alkaline solution of ammonium persulfate-2,6-pyridinedicarboxylic acid, reacted at room temperature for 3 hours, and washed with water for 3 times to obtain a cobalt sheet-supported Co-MOF nanoarray composite material. , namely Co-MOF/Co nanoarray composites;

(2) Preparation of self-supporting bimetallic CoNi-MOF nanoarray composite catalyst

The Co-MOF/Co nanoarray composites were immersed in 10 mL of ethanol solution containing 4.0 g of nickel nitrate, and reacted at room temperature for 2 h; washed with deionized water and ethanol for 3 times in turn, and dried at 85 °C to constant weight to obtain cobalt sheet supported Ni ²⁺ doped Co-MOF nanoarray composite material, namely self-supporting bimetallic CoNi-MOF nanoarray composite catalyst.

The activated 1cm×1cm cobalt sheet is prepared by 180W ultrasonic for 4 minutes in dilute hydrochloric acid with a mass fraction of 1.5% to remove surface impurities, and then washed with distilled water and ethanol respectively.

The structure of the Co-MOF is the same as that of Example 1.

Example 4 Application of self-supporting bimetallic CoNi-MOF nanoarray composite catalyst for electrocatalytic reduction of nitrogen to ammonia

(1) Electrocatalytic nitrogen reduction

The H-type two-chamber electrolytic cell was connected to the electrochemical workstation, the two chambers were separated by a Nafion115 proton exchange membrane, and 30 mL of pH=7 PBS buffer solution with a concentration of 0.1 M was added to both chambers; the load prepared in Example 1 was added. The self-supporting bimetallic CoNi-MOF nanoarray composite catalyst is used as the working electrode, and the Ag/AgCl reference electrode is placed in the electrolyte of the cathode compartment; the platinum sheet auxiliary electrode is placed in the electrolyte of the anode compartment; After feeding N ₂ for 10 min, set an external voltage of -1.2V for electrocatalytic nitrogen reduction, take the reaction solution of the catalytic reaction for 2 h, and measure the concentration of NH ₄ ⁺ in the reaction solution to test the nitrogen reduction based on bimetallic CoNi-MOF nanosheet catalysts performance;

(2) Draw the standard curve

Use ammonium chloride and pH=7 0.1M PBS buffer solution to prepare a series of NH ₄ ⁺ standard solutions with concentrations of 0.01 mM, 0.02 mM, 0.03 mM, 0.05 mM, 0.1 mM;

Pipette 2mL series of standard solutions, add 2mL NaOH solution with a concentration of 1.0M, 1mL NaClO solution with a concentration of 0.05M, and 0.2mL sodium nitroferricyanide solution with a mass fraction of 1% in turn, shake well, 25 ℃ Place for 2h, detect the absorbance peak value at the wavelength of 653nm of the solution with a UV-vis spectrophotometer, draw the standard curve of absorbance-concentration, that is, A-c, to obtain the standard curve equation;

The 1.0M NaOH solution contains 5% salicylic acid and 5% sodium citrate in mass fraction;

(3) Calculation of Nitrogen Reduction to Ammonia Yield Measure the concentration of NH ₄ ⁺ in the reaction solution, pipette 2mL of the reaction solution for catalytic reaction 2h, replace the 2mL standard solution in step (2), and calculate the ammonia yield according to the standard curve equation .

The above self-supporting bimetallic CoNi-MOF nanoarray composite catalyst was used for electrocatalytic reduction of nitrogen to ammonia. When the applied voltage was -1.2V vs Ag/AgCl, the ammonia yield was 37.8μg _NH3 ·h ^-1 ·mg ^-1 _catalyst , the Faradaic efficiency is 23.8%, indicating the efficient electrocatalytic nitrogen fixation activity of the material.

Example 5

The method is the same as in Example 4, except that the supported self-supporting bimetallic CoNi-MOF nanoarray composite catalyst prepared in Example 2 is used instead of the composite catalyst in Example 1; when the applied voltage is -1.2V vs Ag/AgCl, ammonia The yield was 43.2μg _NH3 ·h ^-1 ·mg ^-1 _catalyst , and the Faradaic efficiency was 30.1%, indicating the high electrocatalytic nitrogen fixation activity of the material.

Example 6

The method is the same as in Example 4, except that the supported self-supporting bimetallic CoNi-MOF nanoarray composite catalyst prepared in Example 3 is used instead of the composite catalyst prepared in Example 1; when the applied voltage is -1.2V vs Ag/AgCl , the ammonia yield was 40.5μg _NH3 ·h ^-1 ·mg ^-1 _catalyst , and the Faradaic efficiency was 26.7%, indicating that the material has high electrocatalytic nitrogen fixation activity.

Claims (4)

1. a kind of preparation method of self-supporting bimetallic CoNi-MOF nano-array composite catalyst, which is characterized in that step is such as Under:

(1) Co-MOF/Co nano-array composite material is prepared

By the 2 of 1.5-2.0mmol, after dipicolimic acid 2 and 2.0-4.5mmol lithium hydroxide are codissolved in 5-8mL water, it is added 1.2-3.0mmol ammonium persulfate obtains clear ammonium persulfate -2, dipicolimic acid 2 aqueous slkali；

1cm × 1cm cobalt piece of activation is immersed in ammonium persulfate -2, in dipicolimic acid 2 aqueous slkali, after reacting at room temperature 2-3h, It is washed with water 3 times, it is cobalt piece load C o-MOF nano-array composite material that product, which is made, i.e. Co-MOF/Co nano-array is compound Material；

(2) self-supporting bimetallic CoNi-MOF nano-array composite catalyst is prepared

Co-MOF/Co nano-array composite material is impregnated into the 10mL ethanol solution of the nickel nitrate containing 1.5-4.0g, room temperature is anti- Answer 1.5-2h；It is successively rinsed 3 times with deionized water and ethyl alcohol, 85 DEG C of dryings to constant weight, cobalt piece is made and loads Ni²⁺The Co- of doping MOF nano-array composite material, i.e. self-supporting bimetallic CoNi-MOF nano-array composite catalyst.

2. a kind of preparation method of self-supporting bimetallic CoNi-MOF nano-array composite catalyst as described in claim 1, It is characterized in that, 1cm × 1cm cobalt piece of the activation, is the 180W ultrasound 2-4min in the dilute hydrochloric acid that mass fraction is 1.5% Surface irregularities are removed, are made after then being cleaned respectively with distilled water, ethyl alcohol.

3. a kind of preparation method of self-supporting bimetallic CoNi-MOF nano-array composite catalyst as described in claim 1, It is characterized in that, the Co-MOF, belongs to Metal-organic frame, chemical formula is [Co₂(PDCA)₂(H₂O)₅] n, PDCA 2, Dipicolimic acid 2 anion；One structural unit of Co-MOF nanometer sheet, by two Co (II) ions, two PDCA anions With five H₂O molecule is constituted；The PDCA, structural formula are as follows:

4. the self-supporting bimetallic CoNi-MOF nano-array composite catalyst of preparation method preparation as described in claim 1 is used In the application of electro-catalysis nitrogen reduction ammonification.