A preparation method, product and application of rose-shaped basic copper nitrate Cu4(NO3)2(OH)6

Abstract

This invention provides a method for preparing, a product of, and the application of rose-shaped basic copper nitrate Cu4(NO3)2(OH)6. The preparation method employs a polyol-mediated process, followed by centrifugation to separate nanoparticles from the solvent, and drying to obtain basic copper nitrate Cu4(NO3)2(OH)6. This preparation process is simple, the reaction conditions are mild, and the product quality is highly controllable, making it suitable for industrial production. The Cu4(NO3)2(OH)6 prepared by this method exhibits a unique rose-shaped three-dimensional hierarchical porous structure. Its large specific surface area and open framework facilitate mass transfer of reactants; simultaneously, its abundant pores enable high-density exposure of active sites and the construction of a confined reaction microenvironment. This catalyst exhibits excellent C2 content in the electrocatalytic CO2 reduction reaction. 2+ It exhibits high product selectivity with a Faraday efficiency of up to 76.7%, while effectively suppressing competitive hydrogen evolution reactions and reducing the formation of hydrogen byproducts.

Description

Technical Field

[0001] This invention belongs to the field of electrochemical catalysis technology, specifically relating to a method for preparing rose-shaped basic copper nitrate Cu4(NO3)2(OH)6, the product, and its application. Background Technology

[0002] Electrocatalytic CO2 reduction (CO2RR), as a novel technology with mild reaction conditions and the potential to be combined with clean energy, can convert greenhouse gases into high-value-added fuels and chemicals, and has practical development prospects. Among the many products of CO2 electroreduction, multi-carbon products have become a research hotspot due to their high energy density and wide range of applications, but their conversion efficiency is usually limited by various competing reactions.

[0003] Designing and preparing novel electrocatalysts with excellent activity and high selectivity for multi-carbon products is crucial for the large-scale practical application of electrocatalytic CO2 reduction. Among numerous CO2 reduction catalysts, copper-based compound catalysts are considered to be ideal for achieving CO2 to C2 due to their unique electronic structure. 2+ The most promising material in the product has a unique position in CO2RR.

[0004] Basic copper nitrate, as a typical basic copper salt, also possesses the catalytic activity of copper-based compounds. The larger the specific surface area of ​​basic copper nitrate, the stronger its catalytic ability, making it a catalyst material with broad application prospects. Currently, most basic copper nitrates prepared in patents are Cu2(NO3)(OH)3. For example, patent document CN 103833066 A provides a method for preparing flake-shaped basic copper nitrate. Although it can obtain regular flake-shaped basic copper nitrate, its preparation process relies on a high-pressure reactor, and the strict operating procedures pose high safety risks. Furthermore, its micron-sized structural characteristics cannot meet the requirements of catalysts for nanoscale size and high dispersibility, resulting in a lack of competitiveness in terms of catalytic activity and adsorption performance.

[0005] Furthermore, in electrocatalysis applications, traditional two-dimensional nanosheets are prone to stacking and aggregation, preventing their internal active sites from participating in the electrocatalytic reaction. This leads to a reduction in the electrochemically active surface area, hindering mass transfer of reactants and severely limiting their catalytic performance. Therefore, breaking the spontaneous stacking of nanosheets and constructing a three-dimensional open structure with both high-density active sites and rapid mass transfer channels is key to fully realizing the catalytic potential of basic copper nitrate materials.

[0006] Currently, basic copper nitrate, as a copper salt, has certain application potential in the field of electrocatalytic CO2 reduction. For example, patent document CN 113151855 A proposes a copper nanocatalyst obtained by using basic copper nitrate as a precursor, adding sodium hydroxide, and then pre-reducing it under constant potential polarization. Using KI solution as the electrolyte, at a voltage of -1.3V (vs. RHE), the total Faradaic efficiency of multi-carbon products is 71.2%, showing good selectivity for improving the reduction of carbon dioxide to multi-carbon products. However, its good catalytic performance is due to the promoting effect of KI solution on C-C coupling, and it is overly dependent on the concentration control of sodium hydroxide. Too high or too low a concentration will lead to a significant decrease in the Faradaic efficiency of multi-carbon products, making it difficult to stably control in practical applications. The preparation method of basic copper nitrate provided in the paper has high overall raw material and production costs. The preparation needs to be carried out under high temperature reaction conditions, and continuous reflux is required during the reaction process, which increases the equipment cost and operation difficulty of industrial production.

[0007] Therefore, this paper aims to develop a synthetic method with a simple process, low raw material cost, large specific surface area, and C content. 2+ A highly selective three-dimensional porous basic copper nitrate catalyst is developed to enable the industrial application of electrocatalytic CO2 reduction into high-value-added chemicals. Summary of the Invention

[0008] To address the problems of complex synthesis processes, high safety risks, high raw material costs, and the lack of multi-level structural integration in existing basic copper nitrate synthesis technologies, this invention provides a method for preparing basic copper nitrate Cu4(NO3)2(OH)6 that features a simple operation process, mild reaction conditions, and conforms to the principles of green synthesis and sustainable development. The basic copper nitrate Cu4(NO3)2(OH)6 prepared by this invention exhibits a three-dimensional hierarchical porous structure, which avoids the stacking and aggregation of two-dimensional nanosheets, thus exposing more active sites. The product obtained by this preparation method and its applications are also disclosed.

[0009] The preparation method of this invention employs a simple and safe polyol-mediated method to synthesize a rose-shaped basic copper nitrate Cu4(NO3)2(OH)6, which is then used as an electrocatalytic CO2 reduction agent to produce C. 2+Electrode catalyst of the product. The above preparation method has a simple operation process, is suitable for scale-up production, and meets the requirements of green and sustainable development. The basic copper nitrate Cu4(NO3)2(OH)6 prepared by this method has a three-dimensional hierarchical rosette structure. This unique rosette structure is assembled from two-dimensional nanosheets, combining plate-like secondary structure and mesoporous characteristics, which can effectively inhibit nanosheet stacking and ensure a high active exposed area on the catalytic surface. On the other hand, its open skeleton constructs a smooth mass transfer pathway, ensuring rapid mass transfer of reactants. Under CO2RR reaction conditions, it can undergo complete structural dissociation and atomic rearrangement, constructing a catalytic interface rich in oxygen vacancy defects, providing abundant active sites, ensuring high catalytic activity for the electrocatalytic reduction of CO2 to C. 2+ The industrial application of these chemicals is of great significance.

[0010] A method for preparing rose-shaped basic copper nitrate Cu4(NO3)2(OH)6 includes the following steps:

[0011] (1) Dissolve copper nitrate trihydrate in diethylene glycol diethyl ether to obtain solution A;

[0012] (2) Dissolve sodium bicarbonate in a mixed solvent consisting of diethylene glycol and deionized water to obtain solution B;

[0013] (3) Heat solution A in a water bath and keep it warm. Add solution B slowly under vigorous stirring to initiate particle nucleation and continue the reaction. Then raise the temperature and continue the reaction. After the reaction is completed, post-treatment is performed to obtain the rose-shaped basic copper nitrate Cu4(NO3)2(OH)6.

[0014] In step (1) above:

[0015] Preferably, the mass-to-volume ratio of copper nitrate trihydrate (Cu(NO3)2·3H2O) to diethylene glycol diethyl ether (DEGDEE) is 5–15 mg / mL. More preferably, it is 8–12 mg / mL. Even more preferably, it is 10 mg / mL.

[0016] In step (2) above:

[0017] Preferably, the mass-to-volume ratio of sodium bicarbonate (NaHCO3) to the mixed solvent is 5–12 mg / mL. More preferably, it is 7–10 mg / mL. Even more preferably, it is 8–9 mg / mL.

[0018] Preferably, the volume ratio of diethylene glycol to deionized water in the mixed solvent is (2~8):1. More preferably, it is (4~6):1. Even more preferably, it is 5:1.

[0019] In step (3) above:

[0020] Preferably, the temperature at which solution A is heated and kept warm is 80~120 °C. More preferably, it is 100 °C.

[0021] Preferably, the stirring speed is 800~1200 rpm. More preferably, it is 1000 rpm.

[0022] Preferably, the reaction time for adding solution B is 10-30 min. More preferably, it is 20 min.

[0023] Preferably, the reaction system is heated to 100-200 °C and the reaction continues for 20-40 min. More preferably, the reaction system is heated to 150 °C and the reaction continues for 30 min.

[0024] Preferably, in step (3), the following post-processing is performed after the reaction is complete:

[0025] The reaction system was cooled and the nanoparticles were separated by centrifugation. The nanoparticles were then ultrasonically dispersed in anhydrous ethanol and centrifuged. This process was repeated twice. The solid particles were then vacuum dried to obtain the rose-shaped basic copper nitrate Cu4(NO3)2(OH)6.

[0026] As a further preferred option, the vacuum drying temperature is 50~70 °C and the time is 4~8 h. Even more preferred is that the vacuum drying temperature is 60 °C and the time is 6 h.

[0027] The preparation method of this invention employs a polyol-mediated method, achieving uniform nucleation and controllable growth of nanoparticles by controlling the homogeneous environment of the reaction system. The resulting product is used for electrocatalytic CO2 reduction to C. 2+ Products. Electrochemical performance testing of the Cu4(NO3)2(OH)6 catalyst revealed that the Cu4(NO3)2(OH)6 electrode, under a voltage condition of -1.8 V (vs. RHE), synthesized C... 2+ The product's Faraday efficiency reaches 76.7%, while hydrogen's Faraday efficiency is only 12.4%. This indicates that the Cu4(NO3)2(OH)6 electrode is effective against C 2+ The improved product selectivity has a significant effect, while simultaneously reducing hydrogen selectivity. This demonstrates that the Cu4(NO3)2(OH)6 catalyst in this invention improves upon the limited number of active sites caused by the small specific surface area. 2+ The method suffers from low product selectivity. However, it is simple, has mild reaction conditions, high safety, and is highly operable, meeting the requirements of green synthesis and sustainable development.

[0028] A rose-shaped basic copper nitrate, Cu4(NO3)2(OH)6, is prepared by any of the methods described above. This rose-shaped basic copper nitrate, Cu4(NO3)2(OH)6, exhibits a three-dimensional hierarchical rose cluster morphology and has a clear layered structure, which is formed by the self-assembly of uniformly thick nanosheets.

[0029] Application of a rose-shaped basic copper nitrate Cu4(NO3)2(OH)6 as described above in electrocatalytic CO2 reduction.

[0030] Preferably, the rose-shaped basic copper nitrate Cu4(NO3)2(OH)6 is sprayed onto the surface of carbon paper as a catalyst and used as the working electrode. The carbon paper serves as the gas diffusion electrode. A flow electrolytic cell is used, with a silver / silver chloride (Ag / AgCl) electrode as the reference electrode, nickel foam as the counter electrode, and potassium hydroxide (KOH) solution as the electrolyte, to carry out the electrocatalytic reduction reaction of carbon dioxide.

[0031] Preferably, the concentration of the potassium hydroxide solution in the electrolyte is 0.5~1.5 mol / L. More preferably, it is 1 mol / L.

[0032] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0033] (1) The method for preparing rose-shaped basic copper nitrate Cu4(NO3)2(OH)6 of the present invention first utilizes a simple polyol-mediated reduction reaction to prepare nanocrystalline Cu4(NO3)2(OH)6, then cools the reaction system for post-processing and product collection, finally obtaining the solid product Cu4(NO3)2(OH)6. The preparation process employs a water bath heating combined with stirring, and the mild reaction conditions break the stringent requirements of traditional high-temperature and high-pressure reactors. This system reduces the occurrence of side reactions such as thermal decomposition or excessive oxidation by accurately controlling the reaction temperature. Furthermore, the preparation process is simple, has high reaction safety, and uses inexpensive and readily available raw materials, allowing for industrial-scale production. In addition, the present invention provides an effective solution to overcome the bottlenecks of existing catalysts such as easy stacking, limited mass transfer, and complex preparation processes, and also provides new ideas for the structural design and practical application of high-performance CO2 reduction electrocatalytic materials.

[0034] (2) The basic copper nitrate Cu4(NO3)2(OH)6 of the present invention exhibits a three-dimensional hierarchical rosette morphology. This material is constructed from regular two-dimensional nanosheets assembled into a three-dimensional porous framework, forming a unique self-supporting structure. This hierarchical porous structure exhibits unique structural advantages: on the one hand, its three-dimensional cross-linked structure provides a rapid pathway for electron transport; on the other hand, the abundant open channels not only expose a high density of active sites but also provide a large number of confined reaction microenvironments. This microenvironment can effectively enrich reactants and accelerate the escape of gaseous products, thereby significantly improving the overall catalytic kinetics. In the basic copper nitrate crystal structure, the layers are interconnected by hydrogen bonds, and the Cu in its crystal framework... 2+ The cation occupies two unequal octahedral coordination sites, forming a unique crystal coordination environment. Due to the low thermodynamic stability of this compound, during electrochemical reduction, the OH groups in the lattice... - With NO3 - The ions are removed, inducing a large-scale structural rearrangement of Cu atoms, ultimately forming a copper-based catalyst rich in structural defects, which greatly increases the number of active sites.

[0035] (3) The basic copper nitrate Cu4(NO3)2(OH)6 of the present invention, when used as an electrode catalyst in the electrocatalytic CO2 reduction reaction, exhibits excellent C 2+ Product selectivity. During the potentiostatic test, the selectivity of H2 was controlled below 20% within the voltage range of -1.0 V to -1.8 V (vs. RHE). Under the condition of -1.8 V (vs. RHE), FE C 2+ The product yield reached 76.7%, while FE and H2 content was only 12.4%. This indicates that the basic copper nitrate catalyst Cu4(NO3)2(OH)6 exhibits good C content. 2+ The product selectivity simultaneously suppresses the competitive hydrogen evolution reaction, reducing the formation of hydrogen gas as a byproduct. In a 1 mol / L KOH electrolyte, at a voltage of -1.8 V (vs. RHE), the current density of Cu₄(NO₃)₂(OH)₆ can reach 375 mA·cm⁻¹. -2 It has outstanding industrialization potential. Attached Figure Description

[0036] Figure 1 The XRD pattern of the Cu4(NO3)2(OH)6 catalyst prepared in Example 1;

[0037] Figure 2 This is a low-magnification SEM image of the Cu4(NO3)2(OH)6 catalyst prepared in Example 1;

[0038] Figure 3 This is a high-magnification SEM image of the Cu4(NO3)2(OH)6 catalyst prepared in Example 1;

[0039] Figure 4 The image shows a TEM image of the Cu4(NO3)2(OH)6 catalyst prepared in Example 1.

[0040] Figure 5 The image shows the HRTEM image of the Cu4(NO3)2(OH)6 catalyst prepared in Example 1.

[0041] Figure 6 The LSV test result is shown for the Cu4(NO3)2(OH)6 catalyst prepared in Example 1.

[0042] Figure 7 The graph shows the electrochemical carbon dioxide reduction performance of the Cu4(NO3)2(OH)6 electrode prepared in Example 1. Detailed Implementation

[0043] The present invention will be further described in detail below through specific embodiments.

[0044] Example 1

[0045] A method for preparing rose-shaped basic copper nitrate Cu4(NO3)2(OH)6:

[0046] (1) Synthesis of nanocrystalline Cu4(NO3)2(OH)6: Using a polyol-mediated method, 300 mg of copper nitrate trihydrate (Cu(NO3)2·3H2O) was dissolved in 30 mL of diethylene glycol diethyl ether (DEGDEE) and stirred until completely dissolved to obtain solution A, which was then set aside for use.

[0047] Dissolve 100 mg of sodium bicarbonate (NaHCO3) in a mixed solvent consisting of 10 mL of diethylene glycol and 2 mL of deionized water, and stir until completely dissolved to obtain solution B.

[0048] The resulting solution A was then heated to 100 °C and maintained at a constant temperature in a water bath reaction system. Solution B was then slowly added under stirring at 1000 rpm to initiate particle nucleation, and the reaction was continued for 20 min. Subsequently, the temperature of the mixed solution reaction system was increased to 150 °C and the reaction was continued for another 30 min.

[0049] (2) Separation of the product: After the reaction was completed, the system was cooled, and the suspension was centrifuged to separate the nanoparticles from the solvent at a speed of 26,000 rpm for 20 min. The separated nanoparticles were ultrasonically dispersed in anhydrous ethanol, centrifuged, and the operation was repeated twice. Finally, the separated solid product (nanoparticles) was placed in a vacuum drying oven at a temperature of 60 ℃ and dried for 6 h to obtain the solid product rose-shaped basic copper nitrate Cu4(NO3)2(OH)6 catalyst.

[0050] Structural characterization:

[0051] Figure 1 This is the XRD pattern of Cu4(NO3)2(OH)6 obtained from powder X-ray diffraction analysis, as shown below. Figure 1 As shown, the diffraction peaks of the prepared material completely match the standard card (JCPDS No. 77-0148) of the monoclinic phase Cu4(NO3)2(OH)6, confirming the synthesis of Cu4(NO3)2(OH)6.

[0052] Figure 2 Figures 3 and 4 are low- and high-magnification scanning electron microscope (SEM) images of the Cu₄(NO₃)₂(OH)₆ catalyst prepared above, respectively. Figure 2 and 3 It can be seen that the prepared Cu4(NO3)2(OH)6 exhibits a three-dimensional hierarchical rose cluster structure with high specific surface area.

[0053] Figure 4 The image shows a transmission electron microscope (TEM) image of the prepared Cu₄(NO₃)₂(OH)₆ catalyst. Figure 4 It can be seen that the structure of this compound is formed by the self-assembly of nanosheets with uniform thickness.

[0054] Figure 5 Here is a high-resolution transmission electron microscope (HRTEM) image of the prepared Cu₄(NO₃)₂(OH)₆ catalyst. Figure 5 The image shows clear lattice fringes with lattice spacings of 0.22 nm and 0.25 nm, corresponding to the (121) and (-121) crystal planes, respectively. Figure 1 The XRD results were mutually verified.

[0055] application:

[0056] The Cu4(NO3)2(OH)6 catalyst prepared above was sprayed onto the surface of a gas diffusion electrode (GDE) using a spray gun, and used as the working electrode for testing the electrocatalytic CO2 reduction performance. Simultaneously, a flow electrolytic cell was used, with nickel foam as the counter electrode and a silver / silver chloride electrode (Ag / AgCl) as the reference electrode. The cathode and anode chambers were separated by a cation exchange membrane (Nafion 117), and the electrolyte was a 1 mol / L potassium hydroxide (KOH) solution. Chorometric amperometry (CA) combined with online gas chromatography (GC) and proton nuclear magnetic resonance (NMR) spectroscopy were employed. 1 H NMR is used to perform full component detection of liquid / gas phase products.

[0057] Figure 6The LSV test results for the Cu4(NO3)2(OH)6 catalyst show that, within the voltage range of 0 V to -2.0 V (vs. RHE), the current density of the Cu4(NO3)2(OH)6 catalyst under CO2 atmosphere is much greater than that under Ar atmosphere, proving that the catalyst has good CO2 reduction activity.

[0058] Figure 7 The Faraday efficiency of the Cu4(NO3)2(OH)6 catalyst was demonstrated by potentiostatic testing in the voltage range of -1.0 to -1.8 V (vs. RHE). It can be seen that the selectivity for H2 is consistently below 20%. Specifically, under the condition of -1.8 V (vs. RHE), C... 2+ The product has a Faraday efficiency of up to 76.7%, while the Faraday efficiency of hydrogen is only 12.4%.

Claims

1. A method for preparing rose-shaped basic copper nitrate Cu4(NO3)2(OH)6, characterized in that, Includes the following steps: (1) Dissolve copper nitrate trihydrate in diethylene glycol diethyl ether to obtain solution A; (2) Dissolve sodium bicarbonate in a mixed solvent consisting of diethylene glycol and deionized water to obtain solution B; (3) Heat solution A in a water bath and keep it warm. Add solution B slowly under vigorous stirring to initiate particle nucleation and continue the reaction. Then raise the temperature and continue the reaction. After the reaction is completed, post-treatment is performed to obtain the rose-shaped basic copper nitrate Cu4(NO3)2(OH)6.

2. The method for preparing rose-shaped basic copper nitrate Cu4(NO3)2(OH)6 according to claim 1, characterized in that... The mass-to-volume ratio of copper nitrate trihydrate to diethylene glycol diethyl ether is 5-15 mg / mL.

3. The method for preparing rose-shaped basic copper nitrate Cu4(NO3)2(OH)6 according to claim 1, characterized in that, The mass-to-volume ratio of sodium bicarbonate to the mixed solvent is 5-12 mg / mL.

4. The method for preparing rose-shaped basic copper nitrate Cu4(NO3)2(OH)6 according to claim 1, characterized in that, The volume ratio of diethylene glycol to deionized water in the mixed solvent is (2~8):

1.

5. The method for preparing rose-shaped basic copper nitrate Cu4(NO3)2(OH)6 according to claim 1, characterized in that, In step (3), the temperature at which solution A is heated and kept warm is 80~120 ℃; The stirring speed is 800~1200 rpm; The reaction time for adding solution B is 10~30 min; The reaction system is heated to 100~200 ℃ and the reaction continues for 20~40 min.

6. The method for preparing rose-shaped basic copper nitrate Cu4(NO3)2(OH)6 according to claim 1, characterized in that, In step (3), the following post-processing is performed after the reaction is complete: The reaction system was cooled and the nanoparticles were separated by centrifugation. The nanoparticles were then ultrasonically dispersed in anhydrous ethanol and centrifuged. This process was repeated twice. The solid particles were then vacuum dried to obtain the rose-shaped basic copper nitrate Cu4(NO3)2(OH)6.

7. The method for preparing rose-shaped basic copper nitrate Cu4(NO3)2(OH)6 according to claim 6, characterized in that, Vacuum drying temperature is 50~70 ℃, time is 4~8 h.

8. A rose-shaped basic copper nitrate Cu4(NO3)2(OH)6, characterized in that, It is prepared by the preparation method according to any one of claims 1 to 7.

9. The application of the rose-shaped basic copper nitrate Cu4(NO3)2(OH)6 as described in claim 8 in the electrocatalytic reduction of CO2.

10. The application according to claim 9, characterized in that, The rose-shaped basic copper nitrate Cu4(NO3)2(OH)6 catalyst was sprayed onto the surface of carbon paper and used as the working electrode. The carbon paper served as the gas diffusion electrode. A flow electrolytic cell was used, with a silver / silver chloride electrode as the reference electrode, nickel foam as the counter electrode, and potassium hydroxide solution as the electrolyte to carry out the electrocatalytic reduction reaction of carbon dioxide.

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