A method for preparing a core-shell material of cuprous oxide and metallic copper

Abstract

The application relates to a preparation method of a cuprous oxide and metal copper core-shell material and belongs to the technical field of core-shell materials. The operation steps are as follows: (1) a copper foil is polished with sandpaper, and is sequentially ultrasonically washed with dilute sulfuric acid and ethanol to obtain a copper foil catalyst; (2) the copper foil catalyst is subjected to oxidation treatment in potassium bicarbonate solution, part of copper on the surface of the copper foil catalyst is dissolved, and another part of copper is converted into divalent basic copper carbonate, thereby obtaining a precursor; (3) the precursor is subjected to reduction treatment in the potassium bicarbonate solution, the basic copper carbonate on the surface of the precursor is converted into monovalent cuprous oxide, and a cuprous oxide and metal copper core-shell material is obtained; the core-shell material has a nano dendritic morphology, and the faradic efficiency of electrocatalytic carbon dioxide reduction to produce formic acid is as high as 96%. The raw material is cheap and easy to obtain, the preparation is carried out at normal temperature and pressure, no additional toxic by-products are generated, and the required equipment is simple, so that the method is a method for realizing large-scale preparation of the cuprous oxide and copper core-shell material.

Description

Technical Field

[0001] This invention belongs to the field of core-shell material technology, and particularly relates to a method for preparing and applying a core-shell material of cuprous oxide and metallic copper. Background Technology

[0002] Electrocatalytic carbon dioxide reduction can convert carbon dioxide into high-value-added chemicals, which is a crucial step in achieving the "dual carbon" goal. Copper-based materials, with their high activity, low consumption, and ease of processing, are considered the most promising electrocatalysts for carbon dioxide reduction. However, due to the competing reaction of hydrogen evolution, readily available bulk materials such as copper foil often exhibit low selectivity for carbon products. Core-shell structure construction strategies can further reduce the rate-determining energy barrier of the reaction through electronic interactions, and are considered one of the most promising methods for modifying bulk copper materials.

[0003] Traditional core-shell material synthesis processes often involve steps such as high-temperature annealing, solvothermal reaction, etching, and chemical reduction. Among these, high-temperature annealing is costly and often requires a specific inert atmosphere for protection, resulting in complex equipment; solvothermal reaction conditions are harsh, requiring high-pressure equipment, and product separation and purification are difficult; etching and chemical reduction processes both require the addition of chemical reagents, which is costly and may generate toxic waste. Summary of the Invention

[0004] In order to achieve low-cost, environmentally friendly, and simple synthesis of core-shell catalysts with copper oxide as the shell and metallic copper as the core, this invention provides a method for preparing core-shell materials of cuprous oxide and metallic copper.

[0005] The preparation steps of a core-shell material of cuprous oxide and metallic copper are as follows: (1) The copper foil was first polished with sandpaper, and then ultrasonically washed with dilute sulfuric acid and ethanol in sequence to obtain the copper foil catalyst; (2) The copper foil catalyst is oxidized in a potassium bicarbonate solution with a concentration of 0.1-1.0 M to obtain a precursor; the oxidation treatment uses a silver chloride electrode as a reference electrode and a platinum wire as a counter electrode. (3) The precursor is reduced in a potassium bicarbonate solution with a concentration of 0.1-1.0 M to obtain a core-shell material of cuprous oxide and metallic copper; the reduction treatment uses a silver chloride electrode as a reference electrode and a platinum wire as a counter electrode. The core-shell materials of cuprous oxide and metallic copper exhibit a nano-dendritic morphology, and the Faraday efficiency for the electrocatalytic reduction of carbon dioxide to formic acid is as high as 96%.

[0006] The further defined technical solution is as follows: In step (1), the area of ​​the copper foil is 0.5–6.0 cm². 2 The thickness is 0.01 to 0.03 mm.

[0007] In step (1), the ultrasonic washing time of the dilute sulfuric acid is 5 to 10 min, and the ultrasonic washing time of the ethanol is 10 to 50 min.

[0008] In step (2), the oxidation treatment voltage is 3.0 to 3.5 V and the time is 100 to 300 s.

[0009] In step (3), the voltage of the reduction treatment is -0.4 to -0.8 V and the time is 400 to 600 s.

[0010] Compared with the prior art, the beneficial technical effects of the present invention are reflected in the following aspects: 1. This invention employs electro-driven oxidation-reduction to obtain a core-shell material with cuprous oxide as the shell and metallic copper as the core; the electrocatalytic carbon dioxide reduction to formic acid production of the core-shell material of this invention has a Faraday efficiency of up to 96%.

[0011] 2. In the oxidation process of step (2) of the present invention, part of the copper on the surface of the copper foil catalyst dissolves and another part of the copper is converted into divalent basic copper carbonate, thereby obtaining the precursor; in the reduction process, the basic copper carbonate on the surface of the precursor is converted into monovalent cuprous oxide, thereby obtaining the cuprous oxide and copper core-shell material.

[0012] 3. The raw materials used in the preparation method of this invention are inexpensive and readily available, and can be carried out at room temperature and pressure without producing additional toxic byproducts. The required equipment is simple, making it a method for large-scale preparation of cuprous oxide and copper core-shell materials. Attached Figure Description

[0013] Figure 1 The X-ray diffraction patterns are those of the cuprous oxide and copper core-shell catalysts prepared in Example 1 and the copper foil catalyst prepared in Comparative Example 1.

[0014] Figure 2 The image shows a scanning electron microscope image of cuprous oxide and copper core-shell catalyst prepared in Example 1.

[0015] Figure 3 The image shows the energy dispersive X-ray elemental distribution of cuprous oxide and copper core-shell catalysts prepared in Example 1.

[0016] Figure 4 The X-ray diffraction pattern of the precursor prepared in Example 2 is shown.

[0017] Figure 5 The image shows a scanning electron microscope image of the copper foil catalyst prepared in Comparative Example 1.

[0018] Figure 6The product Faraday efficiency curve of the copper foil catalyst prepared in Comparative Example 1 is shown.

[0019] Figure 7 The product Faraday efficiency curves are for the cuprous oxide and copper core-shell catalysts prepared in Example 1. Detailed Implementation

[0020] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the embodiments of the present invention.

[0021] The raw materials used in the following examples are not subject to any special restrictions on their source; they can be commercially available.

[0022] Example 1 The preparation steps of a core-shell material of cuprous oxide and metallic copper are as follows: (1) Take an area of ​​1.0 cm 2 A copper foil with a thickness of 0.01 mm was polished with sandpaper and then ultrasonically washed with dilute sulfuric acid and ethanol in sequence for 10 min each time to obtain a copper foil catalyst.

[0023] (2) In a 0.5 M potassium bicarbonate solution, the copper foil catalyst was oxidized at 3.3 V for 240 s with a silver chloride electrode as the reference electrode and a platinum wire as the counter electrode to obtain the precursor.

[0024] (3) In a 0.5 M potassium bicarbonate solution, the precursor was reduced for 480 s at a voltage of -0.55 V with silver chloride electrode as reference electrode and platinum wire as counter electrode to obtain cuprous oxide and copper core-shell catalyst.

[0025] like Figure 1 As shown, the X-ray diffraction patterns of cuprous oxide and the copper core-shell catalyst in Example 1 were obtained using X-ray analysis. Figure 1 It is evident that the diffraction peak positions of Example 1 conform to the standard diffraction data card JCPDS NO. 99-0034 for copper and the standard diffraction data card JCPDS NO. 99-0041 for cuprous oxide. This demonstrates that during the reduction process, the basic copper carbonate on the surface of the precursor is converted into monovalent cuprous oxide, thereby obtaining the cuprous oxide and copper core-shell material.

[0026] like Figure 2 As shown, scanning electron microscopy analysis revealed that the cuprous oxide and copper core-shell catalysts in Example 1 exhibited a nanodendritic morphology.

[0027] like Figure 3 As shown, the elemental distribution of cuprous oxide and copper core-shell catalysts in Example 1 was obtained by energy-dispersive X-ray diffraction analysis. Figure 3In the diagram, A represents the dark-field phase of cuprous oxide and the copper core-shell catalyst; B is the superposition of copper and oxygen elemental distribution maps; C is the copper elemental distribution map; and D is the oxygen elemental distribution map. Figure 3 It can be seen that Example 1 is composed of a core-shell structure with cuprous oxide as the shell and metallic copper as the core.

[0028] Example 2 (1) Take an area of ​​1.0 cm 2 A copper foil with a thickness of 0.01 mm was polished with sandpaper and then ultrasonically washed with dilute sulfuric acid and ethanol in sequence for 10 min each time to obtain a copper foil catalyst.

[0029] (2) In a 0.5 M potassium bicarbonate solution, the copper foil catalyst was oxidized at 3.3 V for 240 s with a silver chloride electrode as the reference electrode and a platinum wire as the counter electrode to obtain the precursor.

[0030] like Figure 4 As shown, the X-ray diffraction pattern of the precursor in Example 2 was obtained using X-ray analysis. Figure 4 It is evident that the diffraction peak positions of Example 2 conform to the standard diffraction data card JCPDS NO. 99-0034 for copper and the standard diffraction data card JCPDS NO. 41-1390 for basic copper carbonate. This demonstrates that during the oxidation process, some copper on the surface of the copper foil catalyst dissolves, while another portion of copper is converted into divalent basic copper carbonate, thereby obtaining the precursor.

[0031] Comparative Example 1 1) Take an area of ​​1.0 cm² 2 A copper foil with a thickness of 0.01 mm was polished with sandpaper and then ultrasonically washed with dilute sulfuric acid and ethanol in sequence for 10 min each time to obtain a copper foil catalyst.

[0032] like Figure 1 As shown, the X-ray diffraction pattern of the copper foil catalyst in Comparative Example 1 was obtained by X-ray analysis. Figure 1 It can be seen that the diffraction peak positions of Comparative Example 1 conform to the standard diffraction data card for copper, JCPDS NO. 99-0034, proving that the copper foil catalyst contains only metallic copper phase and no other impurity phases.

[0033] like Figure 5 As shown, the copper foil catalyst in Comparative Example 1 was analyzed using scanning electron microscopy, and its scanning electron microscope image was obtained. Figure 5 It can be seen that Comparative Example 1 has a sheet-like morphology.

[0034] Example 3 The electrocatalytic carbon dioxide reduction activities of Comparative Example 1 and Example 1 were evaluated in an H-type cell. Specific steps and results are as follows: All electrochemical data were measured using a standard three-electrode system. Comparative Example 1 or Example 1 served as the working electrode, silver chloride as the reference electrode, and platinum wire as the counter electrode. A mixture of carbon dioxide-saturated 0.5 M potassium bicarbonate and 0.5 mM hexadecyltrimethylammonium bromide was used as the electrolyte. A Nafion membrane was used as the ion-exchange membrane. Measurements were performed at -0.4, -0.5, -0.6, -0.7, -0.8, and -0.9 V using chronoamperometry for 3600 s. The gaseous products were analyzed by gas chromatography, and the liquid products were analyzed by 1H NMR spectroscopy.

[0035] The Faraday efficiency curve of the product of Comparative Example 1 is shown below. Figure 6 As shown. By Figure 6 It can be seen that the formic acid Faraday efficiency of the copper foil catalyst prepared by Comparative Example 1 first increases and then decreases within the voltage range, reaching the highest value of 64% at -0.6 V.

[0036] The Faraday efficiency curve of the product in Example 1 is as follows: Figure 7 As shown. By Figure 7 It can be seen that the formic acid Faradaic efficiency of the cuprous oxide and copper core-shell catalysts prepared in Example 1 first increases and then decreases within the specified voltage range, reaching a maximum value of 96% at -0.6 V. Meanwhile, the formic acid Faradaic efficiencies of both the cuprous oxide and copper core-shell catalysts prepared in Example 1 are higher than those of the copper foil catalyst prepared in Comparative Example 1 within the specified voltage range. The results indicate that the core-shell construction strategy can optimize the catalyst's reactivity, resulting in electrochemically pretreated core-shell catalysts exhibiting significantly higher performance than untreated catalysts.

[0037] As can be seen from Examples 1-3 and Comparative Example 1 above, the cuprous oxide and copper core-shell catalysts prepared by this invention have the characteristics of high electrocatalytic activity for carbon dioxide reduction, and the formic acid Faradaic efficiency is better than that of the copper foil catalyst. Any obvious variations or modifications derived therefrom are still within the protection scope of the preparation method of this invention.

Claims

1. A method for preparing a core-shell material of cuprous oxide and metallic copper, characterized in that, The operation steps are as follows: (1) The copper foil was first polished with sandpaper, and then ultrasonically washed with dilute sulfuric acid and ethanol in sequence to obtain the copper foil catalyst; (2) The copper foil catalyst is oxidized in a potassium bicarbonate solution with a concentration of 0.1-1.0 M to obtain a precursor; the oxidation treatment uses a silver chloride electrode as a reference electrode and a platinum wire as a counter electrode. (3) The precursor is reduced in a potassium bicarbonate solution with a concentration of 0.1-1.0 M to obtain a core-shell material of cuprous oxide and metallic copper; the reduction treatment uses a silver chloride electrode as a reference electrode and a platinum wire as a counter electrode. The core-shell materials of cuprous oxide and metallic copper exhibit a nano-dendritic morphology, and the Faraday efficiency of electrocatalytic carbon dioxide reduction to formic acid is as high as 96%. In step (2), the oxidation treatment voltage is 3.0–3.5 V and the time is 100–300 s; In step (3), the voltage of the reduction treatment is -0.4 to -0.8 V and the time is 400 to 600 s.

2. The preparation method according to claim 1, characterized in that: In step (1), the area of ​​the copper foil is 0.5–6.0 cm². 2 The thickness is 0.01 to 0.03 mm.

3. The preparation method according to claim 1, characterized in that: In step (1), the ultrasonic washing time of the dilute sulfuric acid is 5 to 10 min, and the ultrasonic washing time of the ethanol is 10 to 50 min.

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