Preparation method of copper phosphate nanosheet for catalyzing ethylene production at low potential

Abstract

This invention discloses a method for preparing copper phosphate nanosheets for catalytic ethylene production at low potential. The method uses commercial copper powder as a precursor and PBS buffer solution as the reaction medium. After ultrasonic treatment, the commercial copper powder is converted into Cu3(PO4)2 nanosheets. The method provided by this invention has widely available raw materials and is simple to operate. The prepared copper phosphate nanosheets can be used as a catalyst in the electrocatalytic reduction of carbon dioxide, exhibiting excellent performance. The potential required for ethylene production is lower than that of copper powder.

Description

Technical Field

[0001] This invention belongs to the field of nanosheet preparation technology, specifically relating to a method for converting copper powder into copper phosphate nanosheets and its application in the field of electrocatalytic reduction of carbon dioxide. Background Technology

[0002] With rapid industrial development and the large-scale use of traditional fossil fuels, a significant amount of CO2 has been emitted into the atmosphere. As early as 2019, the atmospheric CO2 concentration exceeded 410 ppm, far surpassing the maximum safe concentration of 350 ppm, causing problems such as global warming, sea-level rise, and the energy crisis. In the coming decades, the CO2 produced from fossil fuel use will reach 496 billion tons. Therefore, capturing, storing, and converting CO2 into economically valuable chemicals and fuels is one way to solve the current predicament. Current methods for CO2 conversion mainly include thermocatalysis, photocatalysis, electrocatalysis, and biocatalysis. Electrochemical CO2 reduction reaction (ECO2RR) is one of the most promising solutions to these problems. By utilizing electricity obtained from clean energy sources, CO2 can be converted into raw materials for various chemical products, including carbon monoxide (CO), ethylene (C2H4), and ethanol (C2H5OH).

[0003] Cu is a unique ECO2RR catalyst with a negative adsorption energy for the intermediate *CO and a positive adsorption energy for *H, thus it tends to reduce CO2 to hydrocarbons and alcohols. Furthermore, Cu has a moderate affinity for the intermediate *CO, promoting its hydrogenation and C / C coupling reactions. Therefore, Cu has a unique advantage in synthesizing multi-carbon products during ECO2RR. However, generally, the hydrogenation rate of low-carbon intermediates is faster than the C / C bond formation rate, which leads to C / C... 2+ The selectivity of the products is low; Cu catalysts produce at least 16 reduction products, and their reduction pathways and reaction mechanisms are very complex. Currently, using Cu catalysts as ECO2RR still presents many challenges, such as high overpotential, low energy efficiency, poor selectivity, slow electron transfer kinetics, low current density, and poor stability.

[0004] Copper-based materials used for the electrocatalytic reduction of carbon dioxide are mainly elemental copper, copper oxide, cuprous oxide, or alloys containing copper components. Research on copper phosphate for the electrocatalytic reduction of carbon dioxide is relatively limited. Currently, the precursor materials used in methods for preparing copper phosphate nanosheets are mostly copper-containing metal salts or copper-containing templates, which generate significant pollution during the reaction. In addition, most current methods for preparing copper phosphate require precipitants such as sodium hydroxide and urea, making the reaction process complex and variable, with harsh reaction conditions and stringent equipment requirements.

[0005] In summary, most existing methods for preparing copper phosphate nanosheets are complex or have high requirements for equipment and raw materials. Summary of the Invention

[0006] To address the shortcomings of the existing preparation methods, this invention provides a method for preparing copper phosphate nanosheets, which aims to enable them to catalytically reduce carbon dioxide to ethylene at a lower potential.

[0007] To achieve the above objectives, the present invention adopts the following technical solution:

[0008] A method for preparing copper phosphate nanosheets for catalytic ethylene production at low potential is characterized by using commercial copper powder as a precursor and phosphate-buffered saline (PBS) buffer solution as the reaction medium. The commercial copper powder is then converted into copper phosphate (Cu3(PO4)2) nanosheets via ultrasonic treatment. The specific method is as follows:

[0009] Weigh commercial copper powder and disperse it in a phosphate buffer solution to form a dispersion. Sonicate the resulting dispersion and collect the ultrasonically treated sample to obtain copper phosphate nanosheets.

[0010] Furthermore, the pH of the phosphate buffer solution is 7. The phosphate buffer solution can maintain the pH of the system at 7; copper will dissolve to some extent under acidic conditions, while other precipitates will form under alkaline conditions.

[0011] Furthermore, the power of the ultrasound is 1-900W and the ultrasound duration is 3-5h.

[0012] Furthermore, the concentration of the phosphate buffer solution is 0.2 mol / L, and the ratio of the commercial copper powder to the phosphate buffer solution is 0.1–20 mg: 100 mL.

[0013] Compared with existing technologies, the beneficial effects of this invention are as follows:

[0014] 1. The precursor material provided by this invention is commercial copper powder, which is widely available. No template or metal salt is required during the reaction process. The method is simple, the process is convenient, and there are no complicated synthesis steps. It is a simple method to convert copper powder into copper phosphate nanosheets.

[0015] 2. Compared with the traditional liquid phase exfoliation method for preparing nanosheets, the ultrasonic process of this invention does not require the participation of corresponding organic solvents, only PBS is needed, making the experimental environment more friendly.

[0016] 3. The copper phosphate nanosheets prepared by this invention can be used as a catalyst in the electrocatalytic reduction of carbon dioxide and have excellent performance. The potential required for the generation of ethylene is lower than that of copper powder. The maximum efficiency (48%) of ethylene generation by copper powder requires a potential of 3.2V, while the maximum efficiency (47%) of ethylene generation by the copper phosphate nanosheets of this invention only requires 2.4V.

[0017] 4. This invention provides a novel method for preparing nanosheets, which can directly convert commercial copper powder into copper phosphate nanosheets, providing a new approach for the preparation of subsequent copper phosphate nanosheet materials. Attached Figure Description

[0018] Figure 1 The commercial copper powder used in Example 1 ( Figure 1 (a)) and the prepared copper phosphate nanosheets ( Figure 1 (b) SEM image.

[0019] Figure 2 The commercial copper powder used in Example 2 ( Figure 2 (a)) and the prepared copper phosphate nanosheets ( Figure 2 (b) SEM image.

[0020] Figure 3 Commercial copper powder used in Example 3 ( Figure 3 (a)) and the prepared copper phosphate nanosheets ( Figure 3 (b) SEM image.

[0021] Figure 4 This is a SEM image of the copper phosphate nanosheets prepared in Example 4.

[0022] Figure 5 This is a SEM image of the copper phosphate nanosheets prepared in Example 5.

[0023] Figure 6 The diagram shows the product efficiency distribution and current distribution of the copper phosphate nanosheets prepared in Example 1 for the electrocatalytic reduction of carbon dioxide.

[0024] Figure 7 The diagram shows the efficiency distribution of gaseous products and the current diagram for the electrocatalytic reduction of carbon dioxide by pure copper.

[0025] Figure 8 (a) to (d) are the gas product efficiency distribution diagrams of the electrocatalytic reduction of carbon dioxide by copper phosphate nanosheets prepared in Examples 2-5, respectively. Detailed Implementation

[0026] To facilitate understanding by those skilled in the art, the present invention will be further described below in conjunction with the accompanying drawings and embodiments.

[0027] Example 1

[0028] In this embodiment, Cu3(PO4)2 nanosheets were prepared using copper powder with a particle size of 25 nm as raw material. The specific steps are as follows:

[0029] Weigh 10 mg of copper powder with a particle size of 25 nm. Disperse the weighed copper powder in 100 mL of 0.2 mol / L PBS buffer solution (pH=7) to form a dispersion. Sonicate the resulting dispersion at 120 W for 4 h, and collect the ultrasonically treated sample to obtain Cu3(PO4)2 nanosheets.

[0030] The SEM images of the commercial copper powder used in this embodiment and the prepared copper phosphate nanosheets are shown below. Figure 1 (a) and Figure 1 As shown in (b), the product has a uniform nanosheet morphology.

[0031] Example 2

[0032] This embodiment uses commercial copper powder with a particle size of 200 nm as raw material to prepare Cu3(PO4)2 nanosheets. The specific steps are as follows:

[0033] Weigh 10 mg of copper powder with a particle size of 200 nm. Disperse the weighed copper powder in 100 mL of 0.2 mol / L PBS buffer solution (pH=7) to form a dispersion. Sonicate the resulting dispersion at 120 W for 4 h, and collect the ultrasonically treated sample to obtain Cu3(PO4)2 nanosheets.

[0034] The SEM images of the commercial copper powder used in this embodiment and the prepared copper phosphate nanosheets are shown below. Figure 2 (a) and Figure 2 As shown in (b), the product has a uniform nanosheet morphology.

[0035] Example 3

[0036] This embodiment uses commercial copper powder with a particle size of 5 μm as raw material to prepare Cu3(PO4)2 nanosheets. The specific steps are as follows:

[0037] Weigh 10 mg of copper powder with a particle size of 5 μm. Disperse the weighed copper powder in 100 mL of 0.2 mol / L PBS buffer solution (pH = 7) to form a dispersion. Sonicate the resulting dispersion at 120 W for 4 h, and collect the ultrasonically treated sample to obtain Cu3(PO4)2 nanosheets.

[0038] The SEM images of the commercial copper powder used in this embodiment and the prepared copper phosphate nanosheets are shown below. Figure 3 (a) and Figure 3 As shown in (b), the product has a uniform nanosheet morphology.

[0039] Example 4

[0040] This embodiment uses commercial copper powder with a particle size of 25 nm as raw material to prepare Cu3(PO4)2 nanosheets. The specific steps are as follows:

[0041] Weigh 20 mg of copper powder with a particle size of 25 nm. Disperse the weighed copper powder in 100 mL of 0.2 mol / L PBS buffer solution (pH=7) to form a dispersion. Sonicate the resulting dispersion at 120 W for 4 h, and collect the ultrasonically treated sample to obtain Cu3(PO4)2 nanosheets.

[0042] SEM images of the copper phosphate nanosheets prepared in this embodiment are shown below. Figure 4 As shown, the product has a uniform nanosheet morphology.

[0043] Example 5

[0044] This embodiment uses commercial copper powder with a particle size of 25 nm as raw material to prepare Cu3(PO4)2 nanosheets. The specific steps are as follows:

[0045] Weigh 10 mg of copper powder with a particle size of 25 nm. Disperse the weighed copper powder in 100 mL of 0.2 mol / L PBS buffer solution (pH=7) to form a dispersion. Sonicate the resulting dispersion at 700 W for 4 h, and collect the ultrasonically treated sample to obtain Cu3(PO4)2 nanosheets.

[0046] SEM images of the copper phosphate nanosheets prepared in this embodiment are shown below. Figure 5 As shown, the product has a uniform nanosheet morphology.

[0047] The electrocatalytic reduction performance of the samples for CO2 was tested using a flow reactor, with the prepared Cu3(PO4)2 nanosheets used as the working electrode, an Ag / AgCl electrode as the reference electrode, and a nickel mesh as the counter electrode. The electrolyte was 1 mol / L. -1 A potassium hydroxide solution was used. During the electrochemical testing, a chronopotential method was employed. Gaseous products generated at different potentials were directly tested using a gas chromatograph connected to the reactor, while liquid products were subsequently tested using a superconducting nuclear magnetic resonance spectrometer.

[0048] Figure 6 and Figure 7The figures show the product efficiency distribution and current distribution of the electrocatalytic reduction of CO2 by Cu3(PO4)2 nanosheets and copper powder prepared in Example 1, respectively. From the figures, it can be seen that: First, the potential required for ethylene production by Cu3(PO4)2 nanosheets is lower than that by copper powder. The maximum efficiency (48%) of ethylene production by copper powder requires a potential of 3.2V, while the maximum efficiency (47%) of ethylene production by the copper phosphate nanosheets of this invention requires only 2.4V. Second, the total current of the reaction by Cu3(PO4)2 nanosheets is larger, while the maximum current of the reaction by copper powder is 428 mA / cm². -2 The maximum current for the reaction of copper phosphate nanosheets is 585 mA / cm. -2 Finally, the total C2 product content of Cu3(PO4)2 nanosheets can reach 83.3%.

[0049] Figure 8 (ad) shows the performance distribution of gaseous product efficiency of Cu3(PO4)2 nanosheets prepared in Examples 2-5 for electrocatalytic reduction of CO2. As can be seen from the figure, the potentials required to achieve the maximum ethylene efficiency (51.32%, 49.34%, 41.54%, and 40.53%, respectively) in Examples 2-5 are 2.2V, 2.2V, 2.4V, and 2.2V, respectively, which are all significantly improved compared to pure copper. This indicates that this method can prepare a copper phosphate nanosheet for catalytic ethylene production at low potential.

[0050] The above embodiments are typical examples of the present invention and are not intended to limit the invention in any way. Therefore, any adjustments or modifications made to the described process parameters by those skilled in the art based on the overall concept of the present invention, as long as they do not deviate from the inventive concept or exceed the scope defined in the claims, should fall within the protection scope of the present invention.

Claims

1. A method for preparing copper phosphate nanosheets catalyzing ethylene production at low potential, characterized by: A commercial copper powder is used as a precursor, a phosphate buffer solution is used as a reaction medium, and the commercial copper powder is converted into copper phosphate nanosheets after ultrasonic treatment, which specifically comprises the following steps: A commercial copper powder is weighed, and the copper powder is dispersed in a phosphate buffer solution with a pH of 7 and a concentration of 0.2 mol / L to form a dispersion, wherein the ratio of the commercial copper powder to the phosphate buffer solution is 0.1-20 mg:100 mL; the obtained dispersion is subjected to ultrasonic treatment, wherein the power of the ultrasonic treatment is 1-900 W, and the ultrasonic treatment time is 3-5 h; and the sample after the ultrasonic treatment is collected, thereby obtaining copper phosphate nanosheets.

2. The copper phosphate nanosheets prepared by the preparation method of claim 1.

3. The use of the copper phosphate nanosheets of claim 2 as a catalyst in an electrocatalytic reduction of carbon dioxide reaction.

4. Use according to claim 3, characterized in that: The copper phosphate nanosheets are used for the electrocatalytic reduction of carbon dioxide to produce ethylene.

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