Preparation method of carbon paper self-supporting PI-COF composite electrode and application thereof in electro-reduction of CO2

Abstract

The application relates to a preparation method of a carbon paper self-supporting PI-COF composite electrode and application of the carbon paper self-supporting PI-COF composite electrode in electro-reduction of CO2. Melamine is dispersed in NMP, pyromellitic anhydride is dissolved in NMP and a small amount of water is added, then carbon paper treated with hydrochloric acid is placed in a reaction kettle with the NMP solution of pyromellitic anhydride, the melamine dispersion is added drop by drop into the reaction kettle, the mixed solution is heated to 210 DEG C and kept for 24 h, the carbon paper is taken out after being cooled to room temperature, and the carbon paper self-supporting PI-COF composite electrode is obtained after natural air drying. The application obtains a non-metal composite electrode which is stable in structure and simple in raw material, the composite electrode is applied to electrochemical carbon dioxide reduction, the faradic efficiency of carbon monoxide at-0.6V v.s.RHE can reach 84%, no other by-products are generated, the composite electrode has high faradic efficiency and high selectivity, and has a wide application prospect in the field of electrochemical reduction of CO2.

Description

Technical Field

[0001] This invention belongs to the field of organic non-metallic materials technology, specifically relating to a method for preparing a carbon paper self-supporting PI-COF composite electrode and its application in the electroreduction of CO2. Background Technology

[0002] Carbon capture, utilization, and storage (CCUS) technology involves purifying carbon dioxide emitted during production processes and then recycling it into new production processes, rather than simply storing it. Compared to many other carbon dioxide conversion technologies, electrocatalytic carbon dioxide reduction (CO2RR) has unique advantages such as simple operation, simple conditions, and a mild process. The overall performance of electrocatalytic CO2RR depends on factors such as the catalyst, reaction medium, and battery design, and the types of products can be controlled by adjusting the catalyst. Therefore, electrochemical carbon dioxide conversion has significant research value and broad research prospects. The most important aspect of this research is the study of catalysts. Non-metallic materials, as low-cost, abundant, highly conductive, and environmentally friendly catalysts, are often used as catalysts for electrochemical carbon dioxide reduction. Among them, PI-COF is used in this type of catalytic reaction due to its unique physicochemical properties. Summary of the Invention

[0003] The purpose of this invention is to provide a method for preparing a carbon paper self-supporting PI-COF composite electrode with simple and readily available raw materials, simple preparation method, high catalytic efficiency and good selectivity, and its application in the electroreduction of CO2.

[0004] The technical solution adopted in this invention is as follows:

[0005] A method for preparing a carbon paper self-supporting PI-COF composite electrode includes the following steps: dispersing melamine in N-methylpyrrolidone to form a white suspension, obtaining a melamine dispersion; dissolving pyromellitic anhydride in N-methylpyrrolidone and adding a trace amount of water to obtain a pyromellitic anhydride N-methylpyrrolidone solution; adding pretreated carbon paper and the pyromellitic anhydride N-methylpyrrolidone solution together into a 100 mL reaction vessel liner; then adding the melamine dispersion dropwise into the reaction vessel liner; heating the reaction and allowing it to stand at room temperature; removing the carbon paper and air-drying it naturally to obtain the carbon paper self-supporting PI-COF composite electrode.

[0006] The above-mentioned method for preparing a carbon paper self-supporting PI-COF composite electrode uses a molar ratio of melamine:pyromellitic anhydride = 1:1.5.

[0007] In the above-mentioned method for preparing a carbon paper self-supporting PI-COF composite electrode, the amount of melamine used for dispersion and the amount of N-methylpyrrolidone used for dissolving pyromellitic anhydride are both 20 mL.

[0008] The above-mentioned method for preparing a carbon paper self-supporting PI-COF composite electrode includes the following steps in the pretreatment method of the carbon paper: cutting the carbon paper into a rectangle of 1×2cm, placing the cut carbon paper in concentrated hydrochloric acid and sonicating for 10 minutes, washing the sonicated carbon paper with secondary water multiple times until there is no hydrochloric acid residue on the surface of the carbon paper, drying it, and setting it aside for later use.

[0009] In the above-mentioned method for preparing a carbon paper self-supporting PI-COF composite electrode, when dispersing melamine in N-methylpyrrolidone, the melamine should be added to N-methylpyrrolidone slowly.

[0010] The above-mentioned method for preparing a carbon paper self-supporting PI-COF composite electrode, wherein the heating reaction conditions are: reacting at 210℃ for 24 hours.

[0011] In the above-mentioned method for preparing a carbon paper self-supporting PI-COF composite electrode, the standing time at room temperature is 24 hours.

[0012] Application of the carbon paper self-supporting PI-COF composite electrode prepared by any of the above preparation methods in the electroreduction of CO2.

[0013] The above application is performed as follows: A carbon paper self-supporting PI-COF composite electrode is used as the working electrode, Ag / AgCl is used as the reference electrode, a platinum sheet is used as the counter electrode, and 0.5M KHCO3 solution is used as the electrolyte. CO2 is continuously introduced and electrolysis is performed for 1 hour at a voltage of -0.6V vsRHE. The gas at the outlet is collected using a gas bag, and the concentration of carbon monoxide generated is determined using a gas chromatograph.

[0014] The beneficial effects of this invention are as follows:

[0015] 1. The carbon paper self-supporting PI-COF composite electrode prepared in this invention involves in-situ growth of PI-COF on the surface of rough carbon paper. In this invention, PI-COF is a spherical material formed by the stacking of two-dimensional sheet structures. This material can serve as a catalytic active site for the electrochemical reduction of carbon dioxide, efficiently and selectively electrocatalyzing the reduction of carbon dioxide. The Faradaic efficiency at -0.6V vsRHECO can reach 84%, and the product of carbon dioxide reduction is singular. The in-situ grown PI-COF exhibits good stability. After continuous electrolysis for 24 hours, the Faradaic efficiency of CO remains above 70%.

[0016] 2. This invention provides a method for synthesizing a carbon paper self-supporting PI-COF composite electrode in one step using simple and readily available raw materials. The carbon paper self-supporting PI-COF composite electrode prepared by this invention is made by growing two-dimensional sheet-like PI-COF in situ on the surface of rough carbon paper, and allowing the sheet-like PI-COF to be stacked into a spherical shape by standing at room temperature to form catalytic active sites.

[0017] 3. The method of this invention uses readily available and simple raw materials, and the operation steps are straightforward. It can be directly used as a working electrode without the need for auxiliary reagents such as binders or conductive agents. The organic non-metallic catalyst material prepared by the method of this invention shows promising potential in the electrocatalytic reduction of carbon dioxide. Attached Figure Description

[0018] Figure 1 This is the FT-IR image of PI-COF in the carbon paper self-supporting PI-COF composite electrode prepared in Example 1.

[0019] Figure 2 This is a SEM image of the carbon paper self-supporting PI-COF composite electrode prepared in Example 1.

[0020] Figure 3 This is a mapping diagram of the carbon paper self-supporting PI-COF composite electrode prepared in Example 1.

[0021] Figure 4 This is the AFM image of the carbon paper self-supporting PI-COF composite electrode prepared in Example 1.

[0022] Figure 5 This is a diagram of the apparatus used in Example 2 for the electrocatalytic reduction of carbon dioxide using a carbon paper self-supporting PI-COF composite electrode.

[0023] Figure 6 This is a Faraday current efficiency diagram of the electrocatalytic reduction of carbon dioxide products by a carbon paper self-supporting PI-COF composite electrode.

[0024] Figure 7 This is a graph showing the stability test of the electrocatalytic reduction of carbon dioxide using a carbon paper self-supporting PI-COF composite electrode. Detailed Implementation

[0025] Example 1: Carbon paper self-supporting PI-COF composite electrode

[0026] (I) The preparation method is as follows:

[0027] 1) Pretreatment of carbon paper: Cut the carbon paper into rectangles of 1×2cm. Place the cut carbon paper in concentrated hydrochloric acid and sonicate for 10 minutes. Wash the sonicated carbon paper with water several times until there is no hydrochloric acid residue on the surface of the carbon paper. Dry it and set it aside. The rough surface of the carbon paper helps PI-COF to grow on its surface.

[0028] 2) Preparation of carbon paper self-supporting PI-COF composite electrode: Melamine (MA) (378.4 mg, 3 mmol) was slowly added to 20 mL of N-methylpyrrolidone (NMP) to form a white suspension, which yielded a melamine dispersion; pyromellitic anhydride (PMDA) (981.2 mg, 4.5 mmol) was dissolved in 20 mL of NMP, and 162 μL of water was added to obtain a pyromellitic anhydride NMP solution; the pyromellitic anhydride NMP solution and pretreated carbon paper were placed in a 100 mL reactor liner, and the melamine dispersion was slowly added dropwise to the reactor liner to prevent melamine from agglomerating. The reactor was kept at 210 °C for 24 h, and then left to stand at room temperature for 24 h to allow PI-COF to continue growing on the carbon paper surface. The carbon paper was then removed and air-dried to obtain a carbon paper self-supporting PI-COF composite electrode.

[0029] (II) Test Results

[0030] Figure 1 This is the FT-IR image of PI-COF in the carbon paper self-supporting PI-COF composite electrode prepared in Example 1. Figure 1 As can be seen in the infrared absorption curve of PI-COF, it reaches 1785 cm⁻¹. -1 1733cm -1 The asymmetric stretching vibration peak of the carbonyl group in the imide, and 1362 cm⁻¹ -1 The stretching vibration peak of CNC at the point of reaction confirms that the reaction between melamine and pyromellitic anhydride proceeded as designed in the experiment.

[0031] Figure 2 This is a SEM image of the fabricated carbon paper self-supporting PI-COF composite electrode. From... Figure 2 As can be seen, the PI-COF prepared in Example 1 consists of micron-sized microspheres. These micron-sized microspheres are uniformly attached to the surface of carbon fibers, and these microspheres are the active sites for electrocatalytic carbon dioxide.

[0032] Figure 3 This is a mapping image of the carbon paper self-supporting PI-COF composite electrode prepared in Example 1. Figure 3 The conclusions are shown in Table 1.

[0033] Table 1. Element content of electrode materials

[0034] Element Weight / % CK 64.70 NK 28.48 OK 6.82 Totals 100.00

[0035] Depend on Figure 3 As shown in Table 1, C, N, and O elements are uniformly distributed in the material, proving that the material is a covalent organic framework with a regular structure.

[0036] Figure 4 This is the AFM image of the carbon paper self-supporting PI-COF composite electrode prepared in Example 1. From a macroscopic perspective, the material consists of micron-sized spheres attached to the surface of carbon fibers. From its microstructure, it can be seen that these spheres are formed by the accumulation of a large number of two-dimensional sheet-like structures, which well explains why the originally two-dimensional PI-COF structure appears spherical on a macroscopic scale.

[0037] Example 2: Application of carbon paper self-supporting PI-COF composite electrode in electrocatalytic carbon dioxide reduction

[0038] Method: The obtained carbon paper self-supporting PI-COF composite electrode was used as the working electrode.

[0039] Experimental setup such as Figure 5 As shown, the carbon paper self-supporting PI-COF composite electrode prepared in Example 1 was placed on an electrode clamp as the working electrode. Under atmospheric conditions, an H-type electrolytic cell from Tianjin Aida was selected as the electrolytic cell. The electrolyte was 0.5 M KHCO3 solution, with a volume of 70 mL. The proton exchange membrane was a Nafion 117 membrane, the reference electrode was Ag / AgCl, and the counter electrode was a platinum sheet. Electrolysis was performed for 1 hour under continuous carbon dioxide purging, with an electrolysis voltage of -0.6 V (relative to the hydrogen reversible electrode). The gas from the outlet was collected using a gas bag, and the concentration of generated carbon monoxide was determined using gas chromatography. The results are as follows: Figure 6 and Figure 7 .

[0040] like Figure 6 As shown, at a potential of -0.6V vs. RHE, the prepared carbon paper self-supporting PI-COF composite electrode exhibits a Faradaic efficiency of 84% for CO production, which is higher than that of general non-metallic materials. Under this potential condition, the hydrogen evolution reaction is maximally suppressed, and the electrochemical carbon dioxide reduction reaction produces only CO. In summary, this demonstrates that the composite electrode possesses not only high catalytic activity but also high selectivity in the electrocatalytic carbon dioxide reduction reaction.

[0041] like Figure 7 As shown, the prepared carbon paper self-supporting PI-COF composite electrode still exhibits a Faraday efficiency of over 70% for carbon monoxide after continuous electrolysis at a potential of -0.6V vs. RHE for 24 hours. This indicates that the composite electrode has good stability and can be used for a long time.

[0042] It is evident that the carbon paper self-supporting PI-COF composite electrode exhibits absolute advantages in the electrochemical reduction of carbon dioxide, whether in terms of Faraday current efficiency, catalyst selectivity, or working electrode stability. Therefore, the carbon paper self-supporting PI-COF composite electrode has a promising application prospect in the field of carbon dioxide electroreduction.

Claims

1. The application of a carbon paper self-supporting PI-COF composite electrode in the electroreduction of CO2, characterized in that, The method is as follows: A carbon paper self-supporting PI-COF composite electrode is used as the working electrode, Ag / AgCl is used as the reference electrode, a platinum sheet is used as the counter electrode, and 0.5 M KHCO3 solution is used as the electrolyte. CO2 is continuously introduced and electrolysis is performed for 1 hour at a voltage of -0.6 V vs RHE. The gas at the outlet is collected with a gas bag, and the concentration of carbon monoxide generated is determined by gas chromatography. The preparation method of the carbon paper self-supporting PI-COF composite electrode includes the following steps: dispersing melamine in... N A white suspension is formed in methylpyrrolidone to obtain a melamine dispersion; pyromellitic anhydride is dissolved in... N Adding a trace amount of water to methylpyrrolidone yields pyromellitic anhydride. N 1,3-methylpyrrolidone solution; pretreated carbon paper and pyromellitic anhydride N The methylpyrrolidone solution was added together with the 100 mL reaction vessel liner, and then the melamine dispersion was added dropwise to the reaction vessel liner. After heating and reacting, the mixture was allowed to stand at room temperature. The carbon paper was then removed and allowed to air dry naturally to obtain the carbon paper self-supporting PI-COF composite electrode.

2. The application according to claim 1, characterized in that, The molar ratio of melamine to pyromellitic anhydride is 1:1.

5.

3. The application according to claim 1, characterized in that, The substances used for dispersing melamine and for dissolving pyromellitic anhydride N 20 mL of each of the methylpyrrolidone groups.

4. The application according to claim 1, characterized in that, The pretreatment method for the carbon paper includes the following steps: cut the carbon paper into rectangles of 1×2 cm in size, place the cut carbon paper in concentrated hydrochloric acid and sonicate for 10 min, wash the sonicated carbon paper with water multiple times until there is no hydrochloric acid residue on the surface of the carbon paper, dry it, and set it aside.

5. The application according to claim 1, characterized in that, The melamine is dispersed in N When adding melamine to methylpyrrolidone, it should be done slowly. N In methylpyrrolidone.

6. The application according to claim 1, characterized in that, The heating reaction was carried out at 210 °C for 24 h.

7. The application according to claim 1, characterized in that, The time for standing at room temperature is 24 hours.

Images