Barium titanate composite cuprous oxide catalyst, and preparation method and application thereof

Abstract

This invention discloses a barium titanate composite cuprous oxide catalyst, its preparation method, and its application, belonging to the field of catalyst preparation technology. The preparation method of the barium titanate composite cuprous oxide catalyst includes: mixing BaTiO3 and Cu2O cubes at a mass ratio of 1:(0.1~0.4), adding them to an ethanol-water solution for composite formation, followed by filtration, washing, and vacuum drying. The composite catalyst is a heterostructure formed by BaTiO3 nanoparticles attached to the surface of Cu2O cubes. During the electrocatalytic reaction, simultaneous application of ultrasound results in a synergistic effect between the piezoelectric potential generated by BaTiO3 and the catalytic activity of Cu2O, which can efficiently promote nitrate adsorption activation and ammonia generation. Compared with existing technologies, this invention is the first to apply the piezoelectric-electrocatalytic synergistic mechanism to the field of electrocatalytic reduction of nitrogen-containing compounds, achieving an ammonia yield as high as 3370.38 μg·h⁻¹. ‑1 ·mg ‑1 With its excellent performance of 70.54% Faraday efficiency and simple, controllable, and low-cost preparation process, it provides a new route for the green synthesis of ammonia and has important industrial application prospects.

Description

Technical Field

[0001] This invention specifically relates to a barium titanate composite cuprous oxide catalyst, its preparation method, and its application, belonging to the field of catalyst preparation technology. Background Technology

[0002] Ammonia (NH3), as an important chemical raw material, is widely used in agricultural fertilizers, fine chemicals, and energy storage. Currently, the mainstream industrial method for ammonia synthesis is the Haber process, which requires high temperature and pressure conditions to synthesize ammonia through the catalytic reaction of nitrogen and hydrogen. However, the Haber process has inherent drawbacks such as high energy consumption, large carbon emissions, and stringent equipment requirements, making it difficult to meet the current demands for green and low-carbon development. Therefore, developing new, efficient, and green ammonia synthesis pathways under mild conditions has become a research hotspot in the field of catalysis.

[0003] Electrocatalytic nitrate (NO3) The reduction-based ammonia synthesis technology is considered a highly promising green ammonia synthesis technology to replace the traditional Haber process due to its advantages such as mild reaction conditions, the ability to be driven by renewable electricity, and the simultaneous treatment of nitrate wastewater and recovery of ammonia resources. The core of this technology lies in developing high-performance cathode catalysts to achieve efficient adsorption, activation, and reduction of nitrate ions, while suppressing side reactions such as hydrogen evolution and improving ammonia selectivity.

[0004] Currently, reported electrocatalysts for the reduction of nitrate to ammonia mainly include noble metal-based catalysts, transition metal oxide catalysts, and carbon-based composite materials. Among them, cuprous oxide (Cu₂O) has become a research hotspot in this field due to its certain adsorption and activation capabilities for nitrate, low cost, and environmental friendliness. However, single cuprous oxide catalysts suffer from problems such as low electron transfer efficiency, limited catalytic activity, and poor long-term reaction stability, making it difficult to meet practical application requirements. To address these issues, researchers have attempted to optimize the performance of cuprous oxide-based catalysts through composite material construction and heterostructure regulation.

[0005] In recent years, piezoelectric catalysis has gradually emerged as a novel strategy for enhancing catalysis. It involves introducing piezoelectric materials into the catalytic system and utilizing external stress to generate a piezoelectric potential in the materials, thereby controlling the charge distribution and transfer efficiency on the catalyst surface and improving catalytic performance. Barium titanate (BaTiO3), as a typical perovskite-type piezoelectric material, possesses advantages such as high piezoelectric coefficient, good chemical stability, and controllable preparation cost, and has been widely used in piezoelectric catalysis, energy harvesting, and other fields.

[0006] Chinese invention patent CN115323403A discloses a copper foam-supported cobalt nitride catalyst, applied to the electrocatalytic reduction of nitrate to ammonia. This technical solution enhances catalytic performance by combining copper and cobalt nitride, utilizing the coupling effect of the two components. However, its core lies in the regulation of the material's own electronic structure, without introducing a piezoelectric effect, and further improvement in its catalytic activity is still limited by the electron transfer efficiency of the electrocatalytic reaction itself. Chinese invention patent CN118237028A discloses a piezoelectric catalyst composed of barium titanate and cobalt tetraoxonide, applied to the ultrasonic-assisted degradation of organic pollutants in water. This technical solution prepares the composite catalyst via a one-pot solvothermal method, utilizing the piezoelectric effect of barium titanate excited by ultrasound, which synergistically combines with the metallic catalytic effect of cobalt tetraoxonide to achieve highly efficient degradation of organic pollutants.

[0007] In summary, the following technological gaps remain in the existing technology: Firstly, there are no reports on the application of piezoelectric catalysts formed by the composite of barium titanate and cuprous oxide in the electrocatalytic reduction of nitrate to ammonia; secondly, in existing electrocatalytic nitrate reduction systems, how to efficiently excite the piezoelectric effect of piezoelectric materials through applied stress to further enhance the piezoelectric-electrocatalytic synergistic effect still lacks systematic research. Particularly important is the fact that the technical approach of introducing the piezoelectric effect into the field of electrocatalytic nitrate reduction to ammonia, utilizing piezoelectric potential to regulate the charge distribution and transfer efficiency on the catalyst surface to achieve piezoelectric-electrocatalytic synergistic enhancement, has not been publicly disclosed in the existing technology.

[0008] Based on this, developing a piezoelectric catalyst and optimizing its application conditions in the electrocatalytic reduction of nitrate to ammonia is of great significance for promoting the industrial application of electrocatalytic reduction of nitrate to ammonia technology. Summary of the Invention

[0009] To overcome the shortcomings of the prior art, this invention provides a barium titanate composite cuprous oxide catalyst, its preparation method and application. By precisely controlling the catalyst structure and preparation process, the synergistic effect of piezoelectricity and catalytic activity is achieved, enabling efficient synthesis of ammonia from nitrate reduction under mild conditions.

[0010] To achieve the above objectives, the present invention adopts the following technical solution: One objective of this invention is to provide a method for preparing a barium titanate composite cuprous oxide catalyst, comprising the following steps: BaTiO3 and Cu2O cubes were mixed in a ratio of 1:(0.1~0.4), then added to an ethanol-water mixture and stirred to combine. After filtration, washing, and vacuum drying, a composite catalyst with piezoelectric effect was obtained.

[0011] Preferably, the preparation method of BaTiO3 is as follows: BaCl2·2H2O and isopropyl titanate are used as raw materials, mixed and dissolved in an ethanol system, and subjected to hydrothermal reaction. After centrifugation and washing with deionized water, the product is dried under vacuum to obtain BaTiO3.

[0012] Preferably, the pH of the hydrothermal reaction is 13.

[0013] Preferably, the Cu2O cube is prepared as follows: copper sulfate pentahydrate and an auxiliary agent are dissolved in deionized water, NaOH aqueous solution is added to form Cu(OH)2 precipitate, a reducing agent is added, and after aging reaction at room temperature, the product is filtered, washed with anhydrous ethanol and deionized water, and vacuum dried to obtain Cu2O cube.

[0014] Preferably, the auxiliary agent is trisodium citrate dihydrate, and the reducing agent is an aqueous solution of L-ascorbic acid.

[0015] Preferably, the mass ratio of the auxiliary agent to the reducing agent is 1:0.4.

[0016] The second objective of this invention is to provide a barium titanate composite cuprous oxide catalyst.

[0017] The third objective of this invention is to provide an application of barium titanate composite cuprous oxide catalyst in the electrocatalytic reduction of nitrogen-containing compounds.

[0018] Preferably, ultrasound is applied simultaneously during the electrocatalytic reduction of nitrogen-containing compounds to excite the piezoelectric effect of BaTiO3 in the composite catalyst.

[0019] Compared with the prior art, the present invention has the following beneficial effects: (1) This invention is the first to combine BaTiO3, which has a piezoelectric effect, with Cu2O cubic, an electrocatalytically active component, and simultaneously apply ultrasound during the electrocatalytic reaction. The piezoelectric potential generated by BaTiO3 is used to regulate the charge distribution and transfer efficiency on the catalyst surface. This "piezoelectric-electrocatalytic synergy" mechanism is unprecedented in this field and represents an original technical concept. Compared with existing technologies, the catalyst of this invention achieves an ammonia yield of 3000 μg·h under mild conditions. -1 ·mg -1 The above breakthroughs have overcome the performance bottlenecks of traditional electrocatalysts.

[0020] (2) The mild reaction conditions during the preparation process of this invention effectively avoid the destruction of the crystal forms of the two components, and completely preserve the piezoelectric crystal structure of BaTiO3, breaking through the technical bottleneck that existing composite processes easily lead to the loss of piezoelectric material performance; the piezoelectric potential generated by BaTiO3 under ultrasonic action can significantly reduce the adsorption energy barrier of nitrate ions on Cu2O active sites, while inhibiting the hydrogen evolution side reaction. (See attached instruction manual)Figure 4 Experimental results confirm that the present invention achieves a synergistic effect of 1+1>2.

[0021] (3) This invention optimizes the mass ratio of Cu2O to BaTiO3 to screen out the optimal composite ratio range. The optimal results obtained by the inventors through a large number of experiments ensure that the piezoelectric properties of BaTiO3 and the catalytic active sites of Cu2O are fully exposed and have a high synergistic effect, which solves the problems of uneven composite catalyst structure, poor synergy between components, or difficulty in accurately controlling the composite ratio in the prior art. Attached Figure Description

[0022] Figure 1 This is an electron microscope (TEM) image of the barium titanate composite cuprous oxide catalyst prepared in Example 1 of the present invention. Figure 2 The images show X-ray diffraction (XRD) patterns of the barium titanate composite cuprous oxide catalysts prepared in Examples 1-4 of this invention and the products prepared in Comparative Examples 1-2. Figure 3 The Raman spectra of the barium titanate composite cuprous oxide catalysts prepared in Examples 1-4 of this invention are shown. Figure 4 The image shows a comparison of the Faraday efficiency of the barium titanate composite cuprous oxide catalysts prepared in Examples 1-4 and Comparative Examples 1-2 before and after ultrasonication. Figure 5 The graph shows a comparison of the ammonia production rates of the barium titanate composite cuprous oxide catalysts prepared in Examples 1-4 and Comparative Examples 1-2 before and after ultrasonication. Figure 6 The image shows the piezoelectric microscopy (PFM) amplitude-voltage butterfly curve of the barium titanate composite cuprous oxide catalyst prepared in Example 1 of this invention. Detailed Implementation

[0023] The present invention will be further described below with reference to preferred embodiments and the accompanying drawings. The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values; these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of each range, the endpoint values ​​of each range and individual point values, and individual point values ​​can be combined to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein. Unless otherwise specified, the materials, reagents, etc., used in the following embodiments are commercially available. Unless otherwise specified, the experimental methods in the following embodiments are conventional methods.

[0024] Example 1 This embodiment provides a method for preparing a barium titanate composite cuprous oxide catalyst, specifically including the following steps: Preparation of BaTiO3@0.3Cu2O composite catalyst: BaTiO3 and Cu2O cubes were added to a reaction flask at a mass ratio of 1:0.3, along with 20 mL of ethanol-water mixed solution (volume ratio 1:1). The reaction was carried out under vigorous stirring for 12 h. After the reaction was completed, the sample was filtered and washed with deionized water during the filtration process. After washing, the sample was placed in a vacuum drying oven at 60 °C overnight to obtain the BaTiO3@0.3Cu2O composite catalyst.

[0025] The preparation steps of BaTiO3 are as follows: 5 mL of ethanol was added to a beaker, followed by 0.8250 g of BaCl2·2H2O, and 1 mL of isopropyl titanate was added dropwise. The mixture was stirred for 2 h to ensure complete dissolution. Subsequently, 0.2 M NaOH solution was added dropwise to the solution to adjust the pH of the system to 13. Finally, the pH-adjusted solution was transferred to a hydrothermal reactor and reacted at 180 °C for 24 h. After the reaction was completed, the product was washed by centrifugation with deionized water. After washing, the product was dried in a vacuum drying oven at 80 °C for 24 h to obtain BaTiO3 powder.

[0026] The preparation steps of the above Cu₂O cubes are as follows: 0.375 g of copper sulfate pentahydrate (CuSO₄·5H₂O, 1.5 mmol) and 0.147 g of trisodium citrate dihydrate (Na₃C₆H₅O₇·2H₂O, 0.5 mmol) were placed in a 200 mL beaker, and 80 mL of deionized water was added. After stirring until the reactants were completely dissolved, stirring was continued for 15 min. Next, 20 mL of 1.25 M NaOH aqueous solution was added dropwise, and stirring was continued for 15 min to form Cu(OH)₂ precipitate. Then, 50 mL of 0.03 M L-ascorbic acid aqueous solution was added dropwise to precipitate Cu²⁺. + A reduction reaction was carried out, and the solution was continuously stirred for 3 minutes to ensure complete reaction and synthesize Cu2O. Finally, the stirring was turned off, and the reaction system was allowed to settle at room temperature for 1 hour. After aging, the sample was filtered. During the filtration process, anhydrous ethanol and deionized water were used to wash the sample to remove residual NaOH and L-ascorbic acid from the reaction. After washing, the sample was placed in a vacuum drying oven at 60°C overnight to finally obtain Cu2O cubes.

[0027] Example 2 This embodiment provides a method for preparing a barium titanate composite cuprous oxide catalyst, specifically including the following steps: The difference between Example 2 and Example 1 is that the mass ratio of BaTiO3 to Cu2O cubes is 1:0.1. The rest of the preparation steps are the same as in Example 1, and the BaTiO3@0.1Cu2O composite catalyst is finally obtained.

[0028] Example 3 This embodiment provides a method for preparing a barium titanate composite cuprous oxide catalyst, specifically including the following steps: Example 3 differs from Example 1 in that the mass ratio of BaTiO3 to Cu2O cubes is 1:0.2. The remaining preparation steps are the same as in Example 1, and the BaTiO3@0.2Cu2O composite catalyst is finally obtained.

[0029] Example 4 This embodiment provides a method for preparing a barium titanate composite cuprous oxide catalyst, specifically including the following steps: Example 4 differs from Example 1 in that the mass ratio of BaTiO3 to Cu2O cubes is 1:0.4. The remaining preparation steps are the same as in Example 1, and the BaTiO3@0.4Cu2O composite catalyst is finally obtained.

[0030] Comparative Example 1 This comparative example provides a BaTiO3, which differs from Example 1 in that the BaTiO3 is not composited with Cu2O; the remaining steps are the same as the preparation process in Example 1, and the BaTiO3 is obtained.

[0031] Comparative Example 2 This comparative example provides a Cu2O cube, which differs from Example 1 in that the Cu2O is not composited with BaTiO3; the remaining steps are the same as the preparation process in Example 1 to obtain the Cu2O.

[0032] Example 5 The sample obtained in Example 1 was used to evaluate the catalytic performance of electrocatalytic reduction of nitrate to ammonia. The test apparatus was an H-type electrolytic cell. The solvent used in the reaction system was K2SO4 + KNO3. High-purity argon gas was continuously bubbled into the electrolyte for more than 30 minutes before the reaction. A piezoelectric composite catalyst was loaded onto the surface of a conductive substrate to form a cathode catalyst layer. The conductive substrate was selected from carbon paper. This cathode catalyst layer was assembled into the H-type dual-cell electrochemical reaction system and used as the cathode material. An ultrasonic probe was inserted into the cathode cell of the H-type dual-cell system as an external stress application device, and the ultrasound was activated simultaneously during the reaction. Depend on Figure 1 It can be seen that BaTiO3 nanoparticles are uniformly attached to the surface of Cu2O cubes, forming a closely contacted heterostructure. This structure is conducive to interfacial charge transfer and provides a structural basis for piezoelectric-electrocatalytic synergy.

[0033] Depend on Figure 2 It can be seen that the composite catalyst has both tetragonal BaTiO3 (PDF#05-0626) and Cu2O (PDF#05-0667) characteristic diffraction peaks, and no impurity phase is generated, indicating that the composite catalyst prepared by the present invention has high purity and good crystallinity. As the Cu2O content increases, its diffraction peak intensity increases accordingly, indicating that the composite ratio is controllable and adjustable.

[0034] Depend on Figure 3 Therefore, it is located at 307 cm. - The characteristic peaks near ¹ are the B1 mode marker peaks of tetragonal BaTiO3, indicating that the crystal structure of BaTiO3 remains intact during the recombination process, and its piezoelectric properties are preserved; 715, 517, and 255 cm⁻¹ - The peaks near ¹ belong to the A1 symmetry transverse optical mode of BaTiO3, further confirming the tetragonal phase structure of BaTiO3 in the composite catalyst.

[0035] Depend on Figure 4-5 It was found that the ammonia yield and Faraday efficiency of the composite catalyst were significantly improved after ultrasonication, indicating that the piezoelectric effect of BaTiO3 excited by ultrasound and the electrocatalytic activity of Cu2O produced a synergistic enhancement effect. This result confirms the effectiveness of the "piezoelectric-electrocatalytic synergy" mechanism of the present invention, achieving a technical effect of 1+1>2.

[0036] Depend on Figure 6 It can be seen that when the applied voltage is scanned in reverse from +10V to -10V, the phase exhibits a phase hysteresis loop of nearly 180°, which is a characteristic response of typical piezoelectric materials, indicating that BaTiO3 in the composite catalyst has good piezoelectric properties. Figure 6 It can be seen that the amplitude changes with voltage in a typical butterfly-shaped curve, and the amplitude reaches its minimum value near the coercive field, which further confirms that the composite catalyst has excellent piezoelectric response characteristics, and provides direct evidence for its enhanced catalytic performance in electrocatalytic reactions through the piezoelectric effect.

[0037] The above description is merely an embodiment of the present invention and does not limit the patent scope of the present invention. Any equivalent structural or procedural transformations made based on the content of the present invention specification, or direct or indirect applications in other related technical fields, are similarly included within the patent protection scope of the present invention.

Claims

1. A method for preparing a barium titanate composite cuprous oxide catalyst, characterized in that, BaTiO3 and Cu2O cubes were mixed in a ratio of 1:(0.1~0.4), then added to an ethanol-water mixture and stirred to combine. After filtration, washing, and vacuum drying, a composite catalyst with piezoelectric effect was obtained.

2. The preparation method of the barium titanate composite cuprous oxide catalyst as described in claim 1, characterized in that, The preparation method of BaTiO3 is as follows: BaCl2·2H2O and isopropyl titanate are used as raw materials, mixed and dissolved in an ethanol system, and subjected to hydrothermal reaction. After centrifugation and washing with deionized water, the product is dried under vacuum to obtain BaTiO3.

3. The preparation method of the barium titanate composite cuprous oxide catalyst as described in claim 2, characterized in that, The pH of the hydrothermal reaction is 13.

4. A method for preparing a composite catalyst with piezoelectric effect as described in any one of claims 1 to 3, characterized in that, The preparation method of the Cu2O cube is as follows: copper sulfate pentahydrate and an auxiliary agent are dissolved in deionized water, NaOH aqueous solution is added to form Cu(OH)2 precipitate, a reducing agent is added, and after aging reaction at room temperature, the product is filtered, washed with anhydrous ethanol and deionized water, and vacuum dried to obtain Cu2O cube.

5. The preparation method of the barium titanate composite cuprous oxide catalyst as described in claim 4, characterized in that, The auxiliary agent is trisodium citrate dihydrate, and the reducing agent is an aqueous solution of L-ascorbic acid.

6. The preparation method of the barium titanate composite cuprous oxide catalyst as described in claim 4, characterized in that, The mass ratio of the auxiliary agent to the reducing agent is 1:0.

4.

7. A barium titanate composite cuprous oxide catalyst prepared by the preparation method according to any one of claims 1 to 5.

8. The application of the barium titanate composite cuprous oxide catalyst as described in claim 7 in the field of electrocatalytic reduction of nitrogen-containing compounds.

9. The application as described in claim 8, characterized in that, Ultrasound is applied simultaneously during the electrocatalytic reduction of nitrogen-containing compounds to excite the piezoelectric effect of BaTiO3 in the composite catalyst.

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