Preparation method and application of phthalocyanine modified cuprous oxide catalyst

Abstract

The invention discloses a preparation method and application of phthalocyanine modified cuprous oxide, belongs to the field of preparation of high-performance catalytic materials, and mainly relates to preparation and modification of catalytic materials for electrocatalytic carbon dioxide reaction. The Cu2O surface is modified by phthalocyanine, so that the surface charge distribution is optimized, the chemical adsorption of CO2 is enhanced, and the selectivity of ethanol is improved. The preparation process does not involve a high-risk link, the reaction condition is mild, the step design is simple, and the operation difficulty is low.

Description

Technical Field

[0001] The invention belongs to the field of high-performance catalytic material preparation, and mainly relates to the preparation and modification of catalysts for the reaction of carbon dioxide electroreduction to produce ethanol. Background Art

[0002] The acceleration of industrialization and social progress have driven the continuous growth of energy demand, prompted the large-scale exploitation and utilization of fossil fuels, and caused a surge in carbon dioxide (CO2) emissions, intensified the greenhouse effect, and faced major challenges to the development of human society. Exploring and implementing effective CO2 fixation and reuse technologies and converting them into fuels or chemicals with high added value is a highly promising response strategy. It has far-reaching significance for alleviating current environmental pressures and promoting the realization of the "dual carbon" strategic goals, and is a key link in responding to climate change and promoting sustainable development.

[0003] There are many methods to achieve CO2 conversion, such as chemical, photochemical, biological, mineral and electrochemical. Compared with other conversion methods, electrochemical conversion has the remarkable characteristics of mild reaction conditions, relatively simple process flow and environmental friendliness, making CO2 electrocatalytic reduction (CO2RR) regarded as one of the solutions with great practical application potential. As an important fuel additive and chemical raw material, ethanol has huge market demand. At present, the main production route of ethanol relies on the fermentation process of starch-based biomass, but this method is limited by the volatility of raw material supply and high production costs.

[0004] Using CO2RR technology to directly reduce CO2 to ethanol can not only realize the recycling of carbon resources, but also effectively reduce the dependence on biomass resources, which has important economic value and social significance. However, due to the high energy barrier and slow kinetic limitations in the CO2 electrocatalytic reaction to ethanol, its industrial application process is greatly restricted. Therefore, it is urgent to develop efficient electrocatalysts to reduce the CO2 activation barrier, accelerate the reaction kinetics and improve energy efficiency.

[0005] In order to solve the above problems, a composite material of phthalocyanine modified cuprous oxide is currently designed as a catalyst for the catalytic reaction. Cu2O is one of the most promising catalysts that can catalyze the highly selective reduction of CO2 to multi-carbon products, but its catalytic performance still faces problems such as low activity and selectivity and insufficient stability. By modifying the surface of Cu2O with phthalocyanine molecules, the local concentration of the reaction intermediates reduced to ethanol at the copper active site is increased, thereby improving the ethanol selectivity. Summary of the invention

[0006] The primary purpose of the present invention is to prepare a catalytic material for the CO2 electroreduction reaction to produce ethanol. The selectivity of ethanol in the reaction is improved by modifying Cu2O with phthalocyanine.

[0007] In order to achieve the above technical objectives, the technical solution adopted by the present invention is as follows:

[0008] The catalyst material of the present invention comprises the following synthesis steps:

[0009] Step 1: Dissolve copper sulfate pentahydrate and deionized water in a glass bottle, place in an 80°C oil bath, then add a mixture of oleic acid and ethanol, and stir for 30 minutes under magnetic stirring. After that, add NaOH aqueous solution and keep for 10 minutes. Then introduce glucose aqueous solution as a reducing agent, and observe that the color of the suspension gradually changes from dark blue to brick red.

[0010] Step 2: The brick-red product was collected by centrifugation, carefully washed with cyclohexane and ethanol to remove residual oleic acid, and finally dried in a vacuum oven overnight to obtain d-Cu2O.

[0011] Step 3: The obtained d-Cu2O and phthalocyanine molecules (Pc) were ultrasonically mixed in N,N-dimethylformamide (DMF) for 15 minutes. Subsequently, the precipitate was collected by centrifugation, washed three times with DMF, vacuum dried, and then physically ground to obtain the catalyst material, which was recorded as Cu2O@Pc.

[0012] The material obtained by the invention is used as a catalyst for the reaction of producing ethanol by CO2 electroreduction.

[0013] The catalyst material prepared by the method of the present invention optimizes the surface charge distribution and enhances the CO2 chemical adsorption, wherein the phthalocyanine molecule adsorbate produces a high concentration of the key early intermediate CO * , these complex molecules maximize the local concentration of reaction intermediates reduced to ethanol at the copper active site, and the molecules have no effect on the metal active center.

[0014] The Cu2O@Pc catalytic material prepared by the method of the present invention exhibits higher ethanol production selectivity than d-Cu2O. The Faradaic efficiency of ethanol at a voltage of -1.4 V (vs. RHE) is increased from 29.17% to 38.46%. Within the tested voltage range, the ratio of the Faradaic efficiency of ethanol to ethylene can be maintained above 1.5, and reaches a maximum of 1.69 at a voltage of -1.1 V (vs. RHE). BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 X-ray diffraction patterns of d-Cu2O, Cu2O@Pc and Pc.

[0016] Figure 2 (a) is the Fourier transform infrared spectra of d-Cu2O, Cu2O@Pc and Pc, and (b) is the UV-visible absorption spectra of d-Cu2O, Cu2O@Pc and Pc.

[0017] Figure 3 (a) is the nitrogen adsorption-desorption isotherms of d-Cu2O and Cu2O@Pc, and (b) is the pore size distribution diagram of d-Cu2O and Cu2O@Pc.

[0018] Figure 4 SEM images of the prepared materials d-Cu2O and Cu2O@Pc; (a)-(b) are SEM images of d-Cu2O, and (c)-(d) are SEM images of Cu2O@Pc.

[0019] Figure 5 (a) is the TEM image of Cu2O@Pc, and (b) is the energy spectrum element analysis image of Cu2O@Pc.

[0020] Figure 6 (a)-(b) are the product distribution and Faraday efficiency of d-Cu2O and Cu2O@Pc at different voltages in an H-type electrolytic cell, (c)-(d) are the Faraday efficiencies of ethanol and ethylene of d-Cu2O and Cu2O@Pc at different voltages in an H-type electrolytic cell. DETAILED DESCRIPTION

[0021] The present invention will be further described below in conjunction with examples, but the present invention is not limited to the following examples.

[0022] Example 1

[0023] 1mmol of copper sulfate pentahydrate and 15mL of water were dissolved in a glass bottle and placed in an oil bath at 80℃. Then, a mixture of 2mL of oleic acid and 5mL of ethanol was added and stirred for 30min under magnetic stirring. After that, 5mL of 1M NaOH aqueous solution was added and kept for 10min. Subsequently, 5mL of 2M glucose aqueous solution was introduced as a reducing agent and reacted at 80℃ for 3h. The color of the suspension gradually changed from dark blue to brick red. The brick red product was collected by centrifugation, carefully washed with cyclohexane and ethanol for dozens of times to remove residual oleic acid, and finally dried in a vacuum oven at 50℃ overnight for further use. 30mg of the obtained d-Cu2O and 5mg of phthalocyanine molecules (Pc) were ultrasonically mixed in 40mL of N,N-dimethylformamide (DMF) and kept for 15min. Subsequently, the precipitate was collected by centrifugation, washed three times with DMF, vacuum dried and then physically ground to obtain Cu2O@Pc.

[0024] Example 2 (Comparative Example)

[0025] 1mmol of copper sulfate pentahydrate was dissolved in 15mL of water in a glass bottle and placed in an oil bath at 80°C. Then, a mixture of 2mL of oleic acid and 5mL of ethanol was added and stirred for 30min under magnetic stirring. After that, 5mL of 1M NaOH aqueous solution was added and kept for 10min. Subsequently, 5mL of 2M glucose aqueous solution was introduced as a reducing agent and reacted at 80°C for 3h. The color of the suspension gradually changed from dark blue to brick red. The brick red product was collected by centrifugation, carefully washed with cyclohexane and ethanol for dozens of times to remove residual oleic acid, and finally dried in a vacuum oven at 50°C overnight to obtain d-Cu2O.

[0026] Figure 1 X-ray diffraction patterns of d-Cu2O, Cu2O@Pc and Pc.

[0027] Figure 2 (a) is the Fourier transform infrared spectra of d-Cu2O, Cu2O@Pc and Pc, and (b) is the UV-visible absorption spectra of d-Cu2O, Cu2O@Pc and Pc.

[0028] Figure 3 (a) is the nitrogen adsorption-desorption isotherms of d-Cu2O and Cu2O@Pc, and (b) is the pore size distribution diagram of d-Cu2O and Cu2O@Pc.

[0029] Figure 4 SEM images of the prepared materials d-Cu2O and Cu2O@Pc; (a)-(b) are SEM images of d-Cu2O, and (c)-(d) are SEM images of Cu2O@Pc.

[0030] Figure 5 (a) is the TEM image of Cu2O@Pc, and (b) is the energy spectrum element analysis image of Cu2O@Pc.

[0031] Figure 6 (a)-(b) are the product distribution and Faraday efficiency of d-Cu2O and Cu2O@Pc at different voltages in an H-type electrolytic cell, (c)-(d) are the Faraday efficiencies of ethanol and ethylene of d-Cu2O and Cu2O@Pc at different voltages in an H-type electrolytic cell.

[0032] The above is only an embodiment of the present invention, and the common knowledge such as the known specific structure and characteristics in the scheme is not described in detail here. It should be pointed out that for those skilled in the art, several modifications and improvements can be made without departing from the structure of the present invention, which should also be regarded as the protection scope of the present invention, and these will not affect the effect of the implementation of the present invention and the practicality of the patent.

Claims

1. A method for preparing a phthalocyanine modified Cu2O catalytic material, characterized in that: The following steps are involved: Step 1: Dissolve copper sulfate pentahydrate and deionized water in a glass bottle, place in an 80°C oil bath, then add a mixture of oleic acid and ethanol, and stir for 30 minutes under magnetic stirring. After that, add NaOH aqueous solution and keep for 10 minutes. Then introduce glucose aqueous solution as a reducing agent, and observe that the color of the suspension gradually changes from dark blue to brick red. Step 2: The brick-red product was collected by centrifugation, carefully washed with cyclohexane and ethanol to remove residual oleic acid, and finally dried in a vacuum oven overnight to obtain rhombic dodecahedral cuprous oxide (d-Cu2O). Step 3: The obtained d-Cu2O and phthalocyanine molecules (Pc) were ultrasonically mixed in N,N-dimethylformamide (DMF) for 15 minutes. Subsequently, the precipitate was collected by centrifugation, washed three times with DMF, vacuum dried, and then physically ground to obtain the catalyst material, which was recorded as Cu2O@Pc.

2. A phthalocyanine-modified Cu2O catalytic material prepared according to the method of claim 1.

3. A phthalocyanine-modified Cu2O catalytic material prepared according to the method of claim 1, which is used for electrocatalytic CO2 reduction to produce ethanol.

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