A multi-valence copper-based nanomaterial, a preparation method and application thereof

Abstract

The application relates to the fields of material science and electrocatalysis, in particular to a multi-valence copper-based nanomaterial, a preparation method and application thereof, and discloses a preparation method of a multi-valence copper-based nanomaterial, and the operation steps are as follows: step 1, Cu2Te powder is subjected to freezing-low-temperature liquid phase stripping to prepare two-dimensional Cu2Te nanosheets; step 2, the two-dimensional Cu2Te nanosheets are placed in an H-shaped electrolytic cell to be subjected to in-situ electrochemical reduction, the deposition rate of Te element and TeO3 2‑ Is controlled by controlling the reduction current density, and then copper-based nanomaterials with different valences are obtained. The two-dimensional Cu2Te nanosheets are obtained through the freezing-low-temperature liquid phase stripping process, the precursors are widely sourced, no organic solvent needs to be added in the ultrasonic process, the method is simple, and the operation is convenient, so the method is a simple method for preparing two-dimensional materials.

Description

Technical Field

[0001] This invention relates to the fields of materials science and electrocatalysis, specifically to a multivalent copper-based nanomaterial, its preparation method, and its applications. Background Technology

[0002] With the continuous increase in demand for fossil resources, developing efficient and low-energy-consumption methods to achieve energy structure transformation is imperative. It has been reported that electrocatalytic reduction of carbon- or nitrogen-containing resources can maintain global elemental balance and achieve green molecular conversion. Therefore, CN-C coupling through multi-species co-electrolysis has enabled the construction of CN bonds and the direct production of urea. Urea, due to its important role in agriculture and the chemical industry, has always influenced the development of global industry and agriculture. Although electrocatalytic CN-C coupling shows great potential in sustainable urea synthesis, the interaction mechanism between the catalytic site and intermediate species remains unclear. The presence of competitive hydrogenation of intermediate products negatively impacts the selectivity of urea synthesis, necessitating the exploration of corresponding strategies to promote CN-C coupling and urea synthesis.

[0003] It is noteworthy that copper exhibits highly attractive properties in both nitrate and carbon dioxide reduction reactions, thus it is predicted to be the optimal low-cost metal for the co-reduction of nitrate and carbon dioxide to urea. However, Cu's 3d orbitals are completely occupied, hindering charge transfer, and it is also difficult to form bonds with C or N atoms through hybridization of 3d and 2p orbitals, resulting in its intrinsic reactivity. Furthermore, in the nitrate reduction reaction, Cu... 0 It is easily poisoned and deactivated by nitrite, while in the carbon dioxide reduction reaction, high-valence copper species (Cu) + or Cu 2+ The presence of Cu is crucial for CC coupling. Furthermore, in multi-intermediate urea production processes, the activity of individual reaction sites is typically limited. Therefore, in the synthesis of urea, constructing a Cu... 0 -Cu + The dual active sites adsorb and activate nitrate and carbon dioxide respectively, and CN coupling is achieved using the subsequently generated key intermediates *NH2 and *CO, which can efficiently promote the formation yield and selectivity of urea. However, under electroreduction conditions, Cu... + The site is extremely unstable and can be easily reduced to Cu. 0 Therefore, exploring a simple and large-scale application method for preparing multivalent copper-based nanomaterials to achieve high-efficiency electrosynthesis of urea has become a focus of attention. Summary of the Invention

[0004] To address the technical problems mentioned in the background section, this invention provides a multivalent copper-based nanomaterial, its preparation method, and its applications.

[0005] This invention is achieved using the following technical solution: a method for preparing multivalent copper-based nanomaterials, comprising the following steps:

[0006] Step 1: First, Cu2Te powder is subjected to freeze-low temperature liquid phase exfoliation to obtain two-dimensional Cu2Te nanosheets;

[0007] Step 2: Place the two-dimensional Cu2Te nanosheets in an H-type electrolytic cell for in-situ electrochemical reduction. Control the reduction current density to regulate the reaction of elemental Te and TeO3. 2- The precipitation rate can be adjusted to obtain copper-based nanomaterials with different valence states.

[0008] Preferably, the average particle size of the Cu2Te powder in step 1 is 10 micrometers, and the freeze-low temperature liquid phase exfoliation operation in step 1 is as follows: the Cu2Te powder is frozen in liquid nitrogen, then the frozen sample is dispersed in a mixture of isopropanol and water, and placed in a freezer at -86°C for ultrasonic exfoliation, followed by centrifugation after ultrasonication.

[0009] Preferably, in step 1, the freezing time is 8-12 hours and the ultrasound time is 1-2 hours.

[0010] Preferably, the specific operation of step 2 is as follows: the two-dimensional Cu2Te nanosheets obtained in step 1 are dispersed in ethanol and then uniformly sprayed onto carbon paper; in an H-type electrolytic cell, a platinum sheet is used as the counter electrode, Ag / AgCl is used as the reference electrode, the carbon paper uniformly loaded with two-dimensional Cu2Te nanosheets is used as the working electrode, and an aqueous solution of potassium nitrate and potassium hydroxide is used as the electrolyte, and a constant current is applied to carry out the reaction; after the reaction is completed, the carbon paper used as the working electrode is taken out, washed several times with deionized water, and then dried with nitrogen gas, thus obtaining multivalent copper-based nanomaterials on the carbon paper.

[0011] Preferably, the carbon paper has a size of 2×2cm. 2 The loading of two-dimensional Cu2Te nanosheets was 1 mg / cm³. 2 .

[0012] Preferably, the concentration of the potassium nitrate aqueous solution is 0.1–0.5 mol / L, and the concentration of the potassium hydroxide aqueous solution is 1–2 mol / L.

[0013] Preferably, the applied constant current density ranges from 5 to 30 mA / cm². 2 .

[0014] Preferably, the electrochemical reaction takes 0.5 to 1 hour.

[0015] This invention also proposes a multivalent copper-based nanomaterial and its application in the electrocatalytic CN-coupling synthesis of urea. The multivalent copper-based nanomaterial is prepared by the above-described method.

[0016] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0017] This invention obtains two-dimensional Cu2Te nanosheets through a cryogenic-low-temperature liquid phase exfoliation process. The precursors are widely available, and the ultrasonic process does not require the addition of organic solvents. The method is simple and easy to operate, making it a convenient method for preparing two-dimensional materials.

[0018] The in-situ electrochemical reduction process provided by this invention can force Te to precipitate under the action of a reduction current, thereby obtaining copper-based nanomaterials with different valence states. The product has a stable structure, requires little equipment, has a simple process, short operation time, and is environmentally friendly, making it suitable for large-scale production.

[0019] The copper-based nanomaterials prepared by this invention have novel structures, smooth surfaces, and uniform dimensions.

[0020] The multivalent copper-based nanomaterials prepared in this invention, when loaded onto conductive carbon paper, can be directly used as the working electrode for electrocatalytic CN-coupled synthesis. Under room temperature conditions, the electrocatalytic co-reduction of nitrate and carbon dioxide to urea can be achieved. The urea synthesis yields are 10.21 mmol h⁻¹ gcat.⁻¹ and 15.11%, respectively. Attached Figure Description

[0021] Figure 1 This is a TEM image of the multivalent copper-based nanomaterials prepared in Example 1 under conditions of 5 mA / cm². Figure 1 (a) and XRD pattern ( Figure 1 (b)

[0022] Figure 2 This is a TEM image of the multivalent copper-based nanomaterials prepared in Example 2 under conditions of 10 mA / cm². Figure 2 (a) and XRD pattern ( Figure 2 (b)

[0023] Figure 3 This is a TEM image of the multivalent copper-based nanomaterials prepared in Example 3 under conditions of 15 mA / cm². Figure 3 (a) and XRD pattern ( Figure 3 (b)

[0024] Figure 4 This is a TEM image of the multivalent copper-based nanomaterials prepared in Example 4 under conditions of 20 mA / cm². Figure 4 (a) and XRD pattern ( Figure 4 (b)

[0025] Figure 5 This is a TEM image of the multivalent copper-based nanomaterials prepared in Example 5 under conditions of 25 mA / cm². Figure 5 (a) and XRD pattern ( Figure 5 (b)

[0026] Figure 6 This is a TEM image of the multivalent copper-based nanomaterials prepared in Example 6 under conditions of 30 mA / cm². Figure 6 (a) and XRD pattern ( Figure 6 (b)

[0027] Figure 7 This is the UV spectrum of the electrocatalytic CN coupling of the multivalent copper-based nanomaterials obtained in Example 5. Figure 7 (a) shows the result before enzymatic hydrolysis, and (b) shows the result after enzymatic hydrolysis.

[0028] Figure 8 These are the Faraday efficiency and yield diagrams for the electrocatalytic CN coupling of the multivalent copper-based nanomaterials obtained in Example 5;

[0029] Figure 9 This is a flowchart of the preparation method proposed in this invention. Detailed Implementation

[0030] The present invention will now be further described in conjunction with the accompanying drawings and specific embodiments. It should be noted that, without conflict, the various embodiments or technical features described below can be arbitrarily combined to form new embodiments.

[0031] Example 1

[0032] This embodiment prepares multivalent copper-based nanomaterials according to the following steps:

[0033] Step 1: Freeze Cu2Te powder with an average particle size of 10 micrometers in liquid nitrogen for 12 hours. Then disperse the frozen sample in a mixture of isopropanol and water (volume ratio of 1:1). Place it in a freezer at -86°C for continuous sonication for 2 hours. After sonication, centrifuge to obtain two-dimensional Cu2Te nanosheets.

[0034] Step 2: Disperse the two-dimensional Cu2Te nanosheets obtained in Step 1 in ethanol, and then uniformly spray them onto a substrate with a size of 2×2cm. 2 On the carbon paper, the loading was 1 mg / cm 2 ;

[0035] In an H-type electrolytic cell, a platinum sheet was used as the counter electrode, Ag / AgCl as the reference electrode, carbon paper uniformly loaded with two-dimensional Cu₂Te nanosheets as the working electrode, and a 0.1 mol / L potassium nitrate and 1 mol / L potassium hydroxide aqueous solution was used as the electrolyte. An application of -5 mA / cm² was applied. 2 The reaction was carried out under a constant current for 0.5 h. After the reaction was completed, the carbon paper used as the working electrode was removed, washed several times with deionized water, and then dried with nitrogen gas to obtain multivalent copper-based nanomaterials on the carbon paper.

[0036] Figure 1 This is a TEM image of the target product obtained in this embodiment. Figure 1 (a) and XRD pattern ( Figure 1 (b)). TEM shows that the obtained product is a nanosheet structure, and XRD pattern confirms that a two-phase mixture of Cu2Te and Cu2O is obtained after the reaction.

[0037] Example 2

[0038] This embodiment prepares multivalent copper-based nanomaterials according to the following steps:

[0039] Step 1: Freeze Cu2Te powder with an average particle size of 10 micrometers in liquid nitrogen for 12 hours. Then disperse the frozen sample in a mixture of isopropanol and water (volume ratio of 1:1). Place it in a freezer at -86°C for continuous sonication for 2 hours. After sonication, centrifuge to obtain two-dimensional Cu2Te nanosheets.

[0040] Step 2: Disperse the two-dimensional Cu2Te nanosheets obtained in Step 1 in ethanol, and then uniformly spray them onto a substrate with a size of 2×2cm. 2 On the carbon paper, the loading was 1 mg / cm 2 ;

[0041] In an H-type electrolytic cell, a platinum sheet was used as the counter electrode, Ag / AgCl as the reference electrode, carbon paper uniformly loaded with two-dimensional Cu₂Te nanosheets as the working electrode, and a 0.1 mol / L potassium nitrate and 1 mol / L potassium hydroxide aqueous solution was used as the electrolyte. An application of -10 mA / cm² was applied. 2 The reaction was carried out under a constant current for 0.5 h. After the reaction was completed, the carbon paper used as the working electrode was removed, washed several times with deionized water, and then dried with nitrogen gas to obtain multivalent copper-based nanomaterials on the carbon paper.

[0042] Figure 2 This is a TEM image of the target product obtained in this embodiment. Figure 2 (a) and XRD pattern ( Figure 2 (b)). TEM shows that the obtained product is a nanosheet structure, and XRD pattern confirms that a two-phase mixture of Cu2Te and Cu2O is obtained after the reaction.

[0043] Example 3

[0044] This embodiment prepares multivalent copper-based nanomaterials according to the following steps:

[0045] Step 1: Freeze Cu2Te powder with an average particle size of 10 micrometers in liquid nitrogen for 12 hours. Then disperse the frozen sample in a mixture of isopropanol and water (volume ratio of 1:1). Place it in a freezer at -86°C for continuous sonication for 2 hours. After sonication, centrifuge to obtain two-dimensional Cu2Te nanosheets.

[0046] Step 2: Disperse the two-dimensional Cu2Te nanosheets obtained in Step 1 in ethanol, and then uniformly spray them onto a substrate with a size of 2×2cm. 2 On the carbon paper, the loading was 1 mg / cm 2 ;

[0047] In an H-type electrolytic cell, a platinum sheet was used as the counter electrode, Ag / AgCl as the reference electrode, carbon paper uniformly loaded with two-dimensional Cu₂Te nanosheets as the working electrode, and a 0.1 mol / L potassium nitrate and 1 mol / L potassium hydroxide aqueous solution was used as the electrolyte. An application of -15 mA / cm² was applied. 2 The reaction was carried out under a constant current for 0.5 h. After the reaction was completed, the carbon paper used as the working electrode was removed, washed several times with deionized water, and then dried with nitrogen gas to obtain multivalent copper-based nanomaterials on the carbon paper.

[0048] Figure 3 This is a TEM image of the target product obtained in this embodiment. Figure 3 (a) and XRD pattern ( Figure 3 (b)). TEM shows that the obtained product is a nanosheet structure, and XRD pattern confirms that a two-phase mixture of Cu2Te and Cu2O is obtained after the reaction.

[0049] Example 4

[0050] This embodiment prepares multivalent copper-based nanomaterials according to the following steps:

[0051] Step 1: Freeze Cu2Te powder with an average particle size of 10 micrometers in liquid nitrogen for 12 hours. Then disperse the frozen sample in a mixture of isopropanol and water (volume ratio of 1:1). Place it in a freezer at -86°C for continuous sonication for 2 hours. After sonication, centrifuge to obtain two-dimensional Cu2Te nanosheets.

[0052] Step 2: Disperse the two-dimensional Cu2Te nanosheets obtained in Step 1 in ethanol, and then uniformly spray them onto a substrate with a size of 2×2cm. 2 On the carbon paper, the loading was 1 mg / cm 2 ;

[0053] In an H-type electrolytic cell, a platinum sheet was used as the counter electrode, Ag / AgCl as the reference electrode, carbon paper uniformly loaded with two-dimensional Cu₂Te nanosheets as the working electrode, and a 0.1 mol / L potassium nitrate and 1 mol / L potassium hydroxide aqueous solution was used as the electrolyte. An application of -20 mA / cm² was applied. 2 The reaction was carried out under a constant current for 0.5 h. After the reaction was completed, the carbon paper used as the working electrode was removed, washed several times with deionized water, and then dried with nitrogen gas to obtain multivalent copper-based nanomaterials on the carbon paper.

[0054] Figure 4 This is a TEM image of the target product obtained in this embodiment. Figure 4 (a) and XRD pattern ( Figure 4 (b)). TEM shows that the obtained product is a nanosheet structure, and XRD pattern confirms that a two-phase mixture of Cu2O and Cu is obtained after the reaction.

[0055] Example 5

[0056] This embodiment prepares multivalent copper-based nanomaterials according to the following steps:

[0057] Step 1: Freeze Cu2Te powder with an average particle size of 10 micrometers in liquid nitrogen for 12 hours. Then disperse the frozen sample in a mixture of isopropanol and water (volume ratio of 1:1). Place it in a freezer at -86°C for continuous sonication for 2 hours. After sonication, centrifuge to obtain two-dimensional Cu2Te nanosheets.

[0058] Step 2: Disperse the two-dimensional Cu2Te nanosheets obtained in Step 1 in ethanol, and then uniformly spray them onto a substrate with a size of 2×2cm. 2 On the carbon paper, the loading was 1 mg / cm 2 ;

[0059] In an H-type electrolytic cell, a platinum sheet was used as the counter electrode, Ag / AgCl as the reference electrode, carbon paper uniformly loaded with two-dimensional Cu₂Te nanosheets as the working electrode, and a 0.1 mol / L potassium nitrate and 1 mol / L potassium hydroxide aqueous solution was used as the electrolyte. An application of -25 mA / cm² was applied. 2 The reaction was carried out under a constant current for 0.5 h. After the reaction was completed, the carbon paper used as the working electrode was removed, washed several times with deionized water, and then dried with nitrogen gas to obtain multivalent copper-based nanomaterials on the carbon paper.

[0060] Figure 5 This is a TEM image of the target product obtained in this embodiment. Figure 5 (a) and XRD pattern ( Figure 5 (b)). TEM shows that the obtained product is a nanosheet structure, and XRD pattern confirms that a two-phase mixture of Cu2O and Cu is obtained after the reaction.

[0061] Example 6

[0062] This embodiment prepares multivalent copper-based nanomaterials according to the following steps:

[0063] Step 1: Freeze Cu2Te powder with an average particle size of 10 micrometers in liquid nitrogen for 12 hours. Then disperse the frozen sample in a mixture of isopropanol and water (volume ratio of 1:1). Place it in a freezer at -86°C for continuous sonication for 2 hours. After sonication, centrifuge to obtain two-dimensional Cu2Te nanosheets.

[0064] Step 2: Disperse the two-dimensional Cu2Te nanosheets obtained in Step 1 in ethanol, and then uniformly spray them onto a substrate with a size of 2×2cm. 2 On the carbon paper, the loading was 1 mg / cm 2 ;

[0065] In an H-type electrolytic cell, a platinum sheet was used as the counter electrode, Ag / AgCl as the reference electrode, carbon paper uniformly loaded with two-dimensional Cu₂Te nanosheets as the working electrode, and a 0.1 mol / L potassium nitrate and 1 mol / L potassium hydroxide aqueous solution was used as the electrolyte. An application of -30 mA / cm² was applied. 2 The reaction was carried out under a constant current for 0.5 h. After the reaction was completed, the carbon paper used as the working electrode was removed, washed several times with deionized water, and then dried with nitrogen gas to obtain multivalent copper-based nanomaterials on the carbon paper.

[0066] Figure 6 This is a TEM image of the target product obtained in this embodiment. Figure 6 (a) and XRD pattern ( Figure 6 (b)). TEM shows that the obtained product is a nanosheet structure, and XRD pattern confirms that a two-phase mixture of Cu2O and Cu is obtained after the reaction.

[0067] The electrocatalytic CN-coupling synthesis performance of the multivalent copper-based nanomaterials prepared in Example 5 was tested in an H-type electrolytic cell. In the H-type electrolytic cell, a platinum sheet was used as the counter electrode, Ag / AgCl as the reference electrode, carbon paper uniformly loaded with multivalent copper-based nanomaterials as the working electrode, and a 0.1 mol / L potassium nitrate aqueous solution was used as the electrolyte. Carbon dioxide was introduced into the electrolytic cell system at a flow rate of 20 sccm, and different voltages (0, -0.1, -0.2, -0.3, -0.4 V (vs. RHE)) were applied for 1 h. The electrolyte after the cathode reaction was collected, and the electrolyte was quantitatively analyzed by a UV spectrophotometer. The results are as follows: Figure 7 and Figure 8As shown in the figure, the highest urea synthesis efficiency (15.11%) is achieved at -0.1V (vs. RHE), and the highest urea synthesis yield (10.21 mmol / h) is achieved at -0.3V (vs. RHE). -1 g cat. -1 This demonstrates that the obtained material has the ability to efficiently electrocatalyze the coupling of CN to synthesize urea.

[0068] The above embodiments are merely preferred embodiments of the present invention and should not be construed as limiting the scope of protection of the present invention. Any non-substantial changes and substitutions made by those skilled in the art based on the present invention shall fall within the scope of protection claimed by the present invention.

Claims

1. A method for preparing a multi-valence state copper-based nanomaterial, characterized in that, The operation steps are as follows: Step 1, first, the Cu2Te powder is subjected to freeze-low-temperature liquid phase exfoliation to obtain two-dimensional Cu2Te nanosheets; Step 2, two-dimensional Cu2Te nanosheets are placed in an H-type electrolytic cell for in-situ electrochemical reduction, and the deposition rate of Te element and TeO3 2- is controlled by controlling the reduction current density, thereby obtaining copper-based nanomaterials with different valence states; The average particle size of the Cu2Te powder in step 1 is 10 microns, and the freeze-low-temperature liquid phase exfoliation operation in step 1 is as follows: the Cu2Te powder is frozen in liquid nitrogen, then the frozen sample is dispersed in a mixture of isopropyl alcohol and water, and is placed in a freezer at-86℃ for ultrasonic exfoliation, and after ultrasonic exfoliation, centrifugation is performed; In step 1, the freezing time is 8-12h, and the ultrasonic time is 1-2h; The specific operation of the step 2 is as follows: the two-dimensional Cu2Te nanosheet obtained in the step 1 is dispersed in ethanol, and then uniformly sprayed on carbon paper; in an H-type electrolytic cell, with a platinum sheet as a counter electrode, with Ag / AgCl as a reference electrode, with the carbon paper uniformly loaded with the two-dimensional Cu2Te nanosheet as a working electrode, with a potassium nitrate and potassium hydroxide aqueous solution as an electrolyte, a constant current is applied for reaction; after the reaction is completed, the carbon paper as the working electrode is taken out, washed several times with deionized water, and then dried by nitrogen, so that a multi-valence copper-based nanomaterial is obtained on the carbon paper, and the constant current density range is 5-30 mA / cm 2 .

2. The method for preparing a multivalent copper-based nanomaterial as described in claim 1, characterized in that, The carbon paper has a size of 2 x 2 cm 2 The loading of the two-dimensional Cu2Te nanosheets is 1 mg / cm 2 .

3. The method for preparing a multivalent copper-based nanomaterial as described in claim 1, characterized in that, The concentration of the potassium nitrate aqueous solution is 0.1-0.5mol / L, and the concentration of the potassium hydroxide aqueous solution is 1-2mol / L.

4. The method for preparing a multivalent copper-based nanomaterial as described in claim 1, characterized in that, The time of the electrochemical reaction is 0.5-1h.

5. A multi-valent copper-based nanomaterial, characterized in that, The method is prepared by using any one of claims 1-4.

6. Use of a multi-valent copper-based nanomaterial in the electrocatalytic C-N coupling to form urea, characterized in that, The multi-valence copper-based nanomaterial is prepared by using claim 5.

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