阅读说明：本技术 一种用于电化学还原二氧化碳的银基催化剂及其制备方法 (Silver-based catalyst for electrochemical reduction of carbon dioxide and preparation method thereof ) 是由 宋爽 朱颖 何志桥 于 2020-11-02 设计创作，主要内容包括：本发明公开了一种用于电化学还原二氧化碳的银基催化剂及其制备方法。本发明一种用于电化学还原二氧化碳的银基催化剂,包括泡沫银基底和负载在泡沫银基底上的金属有机框架。制备方法如下：一、将泡沫银基底加入聚丙烯酸、氨水的混合溶液中,并加入异丙醇,再加入多巴胺盐酸盐溶液,充分反应后取出泡沫银基底。二、将步骤一得到的泡沫银基底放入金属-氨溶液中并搅拌后,再放入硝酸盐和3,5-二羧酸吡啶混合溶液中并进行水热反应。本发明在泡沫银上负载金属有机框架,显著提高了泡沫银对CO的法拉第效率,达到了91.21％,且基本没有甲酸生成,能够高效催化电化学还原二氧化碳为一氧化碳,可以有效解决大气中二氧化碳浓度过高的问题,完善碳循环产业链,有着良好的应用前景。(The invention discloses a silver-based catalyst for electrochemically reducing carbon dioxide and a preparation method thereof. The invention relates to a silver-based catalyst for electrochemically reducing carbon dioxide, which comprises a foamed silver substrate and a metal organic framework loaded on the foamed silver substrate. The preparation method comprises the following steps: firstly, adding a foamed silver substrate into a mixed solution of polyacrylic acid and ammonia water, adding isopropanol, adding a dopamine hydrochloride solution, and taking out the foamed silver substrate after full reaction. And secondly, putting the foamed silver substrate obtained in the step one into a metal-ammonia solution, stirring, and then putting into a mixed solution of nitrate and 3, 5-pyridinedicarboxylic acid, and carrying out hydrothermal reaction. According to the invention, the metal organic framework is loaded on the foamed silver, so that the Faraday efficiency of the foamed silver to CO is remarkably improved to 91.21%, formic acid is basically not generated, carbon dioxide can be efficiently catalyzed and electrochemically reduced to carbon monoxide, the problem of overhigh concentration of carbon dioxide in the atmosphere can be effectively solved, the carbon cycle industrial chain is perfected, and the application prospect is good.)

1. A silver-based catalyst for electrochemical reduction of carbon dioxide comprising a foamed silver substrate; the method is characterized in that: also includes a metal organic framework supported on the foamed silver substrate.

2. A silver-based catalyst for electrochemical reduction of carbon dioxide according to claim 1, characterized in that: the metal organic frame adopts a silver organic frame.

3. The method of claim 1 for preparing a silver-based catalyst for electrochemical reduction of carbon dioxide, wherein: adding the foamed silver substrate into a mixed solution of polyacrylic acid and ammonia water, adding isopropanol, adding a dopamine hydrochloride solution, and taking out the foamed silver substrate after full reaction.

And step two, putting the foamed silver substrate obtained in the step one into a metal-ammonia solution, stirring, and then putting into a mixed solution of nitrate and 3, 5-pyridinedicarboxylic acid, and carrying out hydrothermal reaction.

4. The method of claim 1 for preparing a silver-based catalyst for electrochemical reduction of carbon dioxide, characterized in that: and the metal-ammonia solution in the second step is silver-ammonia solution.

5. The method of claim 1 for preparing a silver-based catalyst for electrochemical reduction of carbon dioxide, characterized in that: dropwise adding the isopropanol in the step one after stirring at room temperature; the amount of isopropanol added was 0.98 mol.

6. The method of claim 1 for preparing a silver-based catalyst for electrochemical reduction of carbon dioxide, characterized in that: washing the foamed silver substrate in the step one before adding a mixed solution of polyacrylic acid and ammonia water; the specific washing process is as follows: sequentially carrying out ultrasonic treatment by using acetone, ethanol and deionized water, drying in an oven, cooling to room temperature, and putting into a dryer for later use.

7. The method of claim 1 for preparing a silver-based catalyst for electrochemical reduction of carbon dioxide, characterized in that: the mixed solution of polyacrylic acid and ammonia water is obtained by dripping polyacrylic acid solution and ammonia water into deionized water until the polyacrylic acid solution and the ammonia water are completely dissolved.

8. The method of claim 1 for preparing a silver-based catalyst for electrochemical reduction of carbon dioxide, characterized in that: the concentration of the polyacrylic acid solution in the first step is 0.2 g/mL; the ratio of the dosage of the polyacrylic acid solution to the surface area of the foamed silver substrate is 500/4-600/4 mu L/cm²The silver foam of (1); the molar mass of the ammonia water is 2M; the ratio of the using amount of the ammonia water to the surface area of the foamed silver substrate is 500/4-600/4 mu L/cm²(ii) a The ratio of the addition amount of the dopamine hydrochloride to the surface area of the foamed silver substrate is 0.20/4mmol/cm²(ii) a The final volume ratio of water to isopropanol is 1: 3.

9. The method of claim 1 for preparing a silver-based catalyst for electrochemical reduction of carbon dioxide, characterized in that: silver nitrate is adopted as the nitrate in the second step; the ratio of the addition of the silver nitrate to the surface area of the foamed silver substrate is 0.0038/4mol/cm²The silver foam of (1); the ratio of the addition amount of the 3, 5-pyridinedicarboxylic acid to the surface area of the foamed silver substrate was 0.0012/4mol/cm²The silver foam of (1); the hydrothermal temperature in step two was 120 ℃.

10. The method of claim 1 for preparing a silver-based catalyst for electrochemical reduction of carbon dioxide, characterized in that: in the second step, the hydrothermal reaction time is 18-30 h.

Technical Field

The invention belongs to the technical field of carbon dioxide reduction catalysts, and particularly relates to a silver-based catalyst for electrochemically reducing carbon dioxide and a preparation method thereof.

Background

Since the industrial revolution, traditional fossil fuels including coal, oil and natural gas have become the leading energy supply means of human society, and the concentration of carbon dioxide, which is the main combustion product of fossil fuels, in the atmosphere is also increasing. Excessive carbon dioxide emissions can lead to a number of environmental problems including greenhouse effect, sea level elevation, el nino frequency, land salinization, and the like. At present, electrochemical, photochemical, thermochemical and biochemical methods can treat carbon dioxide, wherein electrochemical reduction of carbon dioxide has the most development potential due to simple reaction conditions and high conversion rate, and has the potential for large-scale industrial application.

In the electrochemical reduction of carbon dioxide, the kind of product may be affected by various factors, such as the kind of catalyst, the electrolyte solution, the temperature and voltage, and the like. In which the catalyst plays a decisive role, different catalysts will lead to different paths and thus to different reaction products for the electrochemical reduction of carbon dioxide. Compared with other noble metal catalysts, silver (Ag) is rich in reserves, low in price, high in selectivity to carbon monoxide and high in overpotential; for example, the highest faradaic efficiency of CO for silver foam at-1.12 v (vs rhe) is 82.91%, while the product is not unique and contains about 3% formic acid. The metal organic framework has larger electrochemical active area, higher crystallinity and proper pore size distribution, and can effectively reduce the overpotential required by the reaction.

Disclosure of Invention

The invention aims to solve the problem of over-high overpotential of silver in the reaction process of electrochemical reduction of carbon dioxide, and provides a silver-based catalyst for electrochemical reduction of carbon dioxide and a preparation method thereof.

The invention relates to a silver-based catalyst for electrochemically reducing carbon dioxide, which comprises a foamed silver substrate and a metal organic framework loaded on the foamed silver substrate.

Preferably, the metal organic frame is a silver organic frame.

The preparation method of the silver-based catalyst comprises the following steps:

adding the foamed silver substrate into a mixed solution of polyacrylic acid and ammonia water, adding isopropanol, adding a dopamine hydrochloride solution, and taking out the foamed silver substrate after full reaction.

And step two, putting the foamed silver substrate obtained in the step one into a metal-ammonia solution, stirring, and then putting into a mixed solution of nitrate and 3, 5-pyridinedicarboxylic acid, and carrying out hydrothermal reaction.

Preferably, the metal-ammonia solution in the second step is a silver-ammonia solution.

Preferably, the isopropanol in step one is added dropwise after stirring at room temperature. The amount of isopropanol added was 0.98 mol.

Preferably, the foamed silver substrate in the step one is washed before the mixed solution of polyacrylic acid and ammonia water is added; the specific washing process is as follows: sequentially carrying out ultrasonic treatment by using acetone, ethanol and deionized water, drying in an oven, cooling to room temperature, and putting into a dryer for later use.

Preferably, the mixed solution of polyacrylic acid and ammonia water is obtained by dripping polyacrylic acid solution and ammonia water into deionized water until the polyacrylic acid solution and the ammonia water are completely dissolved.

Preferably, the concentration of the polyacrylic acid solution in the first step is 0.2 g/mL; the ratio of the dosage of the polyacrylic acid solution to the surface area of the foamed silver substrate is 500/4-600/4 mu L/cm²The silver foam of (1); the molar mass of the ammonia water is 2M; the ratio of the using amount of the ammonia water to the surface area of the foamed silver substrate is 500/4-600/4 mu L/cm². The ratio of the addition amount of the dopamine hydrochloride to the surface area of the foamed silver substrate is 0.20/4mmol/cm². The final volume ratio of water to isopropanol is 1: 3.

Preferably, silver nitrate is adopted as the nitrate in the second step; the ratio of the addition of the silver nitrate to the surface area of the foamed silver substrate is 0.0038/4mol/cm²The silver foam of (1); the ratio of the addition amount of the 3, 5-pyridinedicarboxylic acid to the surface area of the foamed silver substrate was 0.0012/4mol/cm²The silver foam of (1). Step two, water heatingThe temperature was 120 ℃.

Preferably, in the second step, the hydrothermal reaction time is 18-30 h.

The invention has the beneficial effects that:

1. according to the invention, the metal organic framework is loaded on the foamed silver, so that the Faraday efficiency of the foamed silver to CO is remarkably improved to 91.21%, formic acid is basically not generated, carbon dioxide can be efficiently catalyzed and electrochemically reduced to carbon monoxide, the problem of overhigh concentration of carbon dioxide in the atmosphere can be effectively solved, the carbon cycle industrial chain is perfected, and the application prospect is good.

2. The silver-based metal organic framework material is synthesized in situ, so that the catalytic overpotential of silver is effectively reduced, and the conversion rate of reducing carbon dioxide into carbon monoxide is improved.

3. According to the invention, the effect of directly loading the metal organic framework on the foamed silver is realized by adding the foamed silver into the mixed solution of the silver ammonia solution, the nitrate and the 3, 5-pyridinedicarboxylic acid after the foamed silver reacts with the mixed solution of the polyacrylic acid-ammonia water, the isopropanol and the dopamine hydrochloride solution, and compared with the mode of preparing the metal organic framework powder and loading the metal organic framework powder on the substrate in the prior art, the method is simpler, the loading is more stable, and the reliability of the long-term use of the silver-based catalyst is ensured.

Drawings

Fig. 1 is an XRD pattern of the silver-based metal organic framework synthesized in example 2.

Fig. 2 is a TEM image of the silver-based metal organic framework synthesized in example 2.

FIG. 3 shows the catalyst prepared in each example in CO₂Saturated 0.1M KHCO₃Graph of faradaic efficiency in solution.

Detailed Description

The invention is further described below with reference to the accompanying drawings.

Example 1

(1) Cutting a rectangular foamed silver sheet with the thickness of 1cm multiplied by 2cm from the foamed silver, then carrying out ultrasonic treatment on the obtained foamed silver sheet for 15min by using acetone, ethanol and deionized water, drying the foamed silver sheet in a 50 ℃ oven, cooling the dried foamed silver sheet to the room temperature, and putting the dried foamed silver sheet into a dryer for later use.

(2) Completely dissolving 500 mu L of 0.2g/mL polyacrylic acid (PAA) and 500 mu L of ammonia water (2M) in 16.5mL of deionized water, adding two pieces of foamed silver flakes obtained by the treatment in the step (1), stirring for 10min at room temperature, dropwise adding 75mL of Isopropanol (IPA) into the solution to fully disperse the PAA, then adding 7.5mL of 5mg/mL dopamine hydrochloride solution into the mixture at 50 ℃ to react for 3.5h, wherein the final volume ratio of water to IPA is 1: 3. And then taking out the foamed silver sheet.

(3) Preparing a silver ammonia solution: 4mL of aqueous ammonia (2M) was diluted to 50mL with water and added dropwise to 100mL of a 10g/mL silver nitrate solution until the brown color disappeared.

(4) And (3) putting the foamed silver sheet prepared in the step (2) into the silver ammonia solution prepared in the step (3), stirring for 2h, taking out the foamed silver sheet, putting the foamed silver sheet into 40mL of deionized water containing 0.64g of silver nitrate and 0.2g of 3, 5-pyridinedicarboxylic acid, ultrasonically mixing uniformly, pouring the mixture into a polytetrafluoroethylene reaction kettle, carrying out hydrothermal treatment at 120 ℃ for 18h, cooling to room temperature, taking out to obtain a silver-based catalyst electrode sheet, and drying in an oven for later use.

Example 2

(1) Cutting a 1cm multiplied by 2cm rectangular foam silver sheet by the foam silver, then carrying out ultrasonic treatment for 15min by acetone, ethanol and deionized water, drying in a 50 ℃ oven, cooling to room temperature, and putting into a dryer for later use.

(2) Completely dissolving 500 mu L of 0.2g/mL polyacrylic acid (PAA) and 500 mu L of ammonia water (2M) in 16.5mL of deionized water, adding two pieces of foamed silver flakes obtained by the treatment in the step (1), stirring for 10min at room temperature, dropwise adding 75mL of Isopropanol (IPA) into the solution to fully disperse the PAA, then adding 7.5mL of 5mg/mL dopamine hydrochloride solution into the mixture at 50 ℃ to react for 3.5h, wherein the final volume ratio of water to IPA is 1: 3.

(3) Preparing a silver ammonia solution: 4mL of aqueous ammonia (2M) was diluted to 50mL and added dropwise to 100mL of a 10g/mL silver nitrate solution until the brown color disappeared.

(4) And (3) putting the foam silver sheet prepared in the step (2) into the silver ammonia solution prepared in the step (3), stirring for 2h, putting into 40mL deionized water containing 0.64g of silver nitrate and 0.2g of 3, 5-pyridinedicarboxylate, ultrasonically mixing uniformly, pouring into a polytetrafluoroethylene reaction kettle, carrying out hydrothermal treatment at 120 ℃ for 24h, cooling to room temperature, taking out to obtain a silver-based catalyst electrode sheet, and drying in an oven for later use.

As can be seen from FIG. 1 (XRD pattern of catalyst), the diffraction peaks at 38.1 °, 44.3 °, 64.46 °, 77.41 °, 81.56 ° of the silver-based catalyst prepared in this example correspond to the (111), (200), (220), (311), (222) crystal planes (JCPDS No.01-089-3722) in the Ag standard card, respectively. It is fully seen from the figure that the crystal plane of Ag in the silver-based catalyst obtained in example 2 is mainly represented by (111); since Ag (111) is a suitable electrocatalyst for stabilizing COOH and releasing CO, the silver-based catalyst provided in this example has high selectivity and can effectively catalyze the reaction of electrochemically reducing carbon dioxide.

As can be seen from fig. 2 (TEM image of catalyst), the arrangement of Ag in the catalyst obtained in this example is very uniform, and it is illustrated from the side that the structure obtained by the present invention can stabilize metals and reduce their agglomeration. This also increases the stability of the working electrode.

Example 3

(1) Cutting a 1cm multiplied by 2cm rectangular foam silver sheet by the foam silver, then carrying out ultrasonic treatment for 15min by acetone, ethanol and deionized water, drying in a 50 ℃ oven, cooling to room temperature, and putting into a dryer for later use.

(2) 0.2g/mL polyacrylic acid (PAA) 500. mu.L and 500. mu.L aqueous ammonia (2M) were completely dissolved in 16.5mL deionized water, two pieces of treated silver foam were added, followed by stirring at room temperature for 10min, dropwise addition of 75mL isopropyl alcohol (IPA) in the solution to thoroughly disperse the PAA, followed by addition of 7.5mL of 5mg/mL dopamine hydrochloride solution at 50 ℃ to the mixture for 3.5h, wherein the final volume ratio of water to IPA was 1: 3.

(3) Preparing a silver ammonia solution: 4mL of aqueous ammonia (2M) was diluted to 50mL and added dropwise to 100mL of a 10g/mL silver nitrate solution until the brown color disappeared.

(4) And (3) putting the foamed silver sheet prepared in the step (2) into the silver ammonia solution prepared in the step (3), stirring for 2h, putting into 40mL of deionized water containing 0.64g of silver nitrate and 0.2g of 3, 5-pyridinedicarboxylate, ultrasonically mixing uniformly, pouring into a polytetrafluoroethylene reaction kettle, carrying out hydrothermal treatment at 120 ℃ for 30h, cooling to room temperature, taking out the electrode sheet, and drying in an oven for later use.

The CO faradaic efficiencies of the silver-based catalysts obtained in examples 1 to 3 by different hydrothermal reaction times are shown in fig. 3, and the CO faradaic efficiencies of the silver-based catalysts obtained in examples 1 to 3 are 87.9%, 91.21% and 89.06%, respectively, which are significantly higher than those of the existing silver foam catalysts. Particularly, the faradaic efficiency of CO of the silver-based catalyst obtained in example 2 with the hydrothermal reaction time of 24 hours is more than 90%, and the faradaic efficiency of CO is higher than that of CO₂The catalytic efficiency of (2) is extremely high.