Preparation method and application of octahedral cuprous oxide containing defects

Abstract

The invention discloses a preparation method and application of octahedral cuprous oxide containing defects, and belongs to the technical field of material preparation. In order to solve the problems that in existing cuprous oxide preparation, a defect structure is difficult to accurately regulate and control, and the crystal form uniformity is insufficient, the method comprises the steps that a copper source solution, a glucose solution, a sodium citrate solution and an ammonium fluoride solution with specific concentrations are mixed according to the volume ratio, the pH is adjusted to 10.5-11, then a hydrothermal reaction is conducted, and a target product is obtained through centrifugation, filtration, washing and drying. The method comprises the following specific steps: mixing solutions, reacting in a high-pressure reaction kettle at 140-165 DEG C for 4-6 hours, and realizing octahedral crystal form construction and defect regulation and control by controlling the raw material ratio and reaction conditions. The preparation method is simple in process and high in controllability, and the prepared octahedral cuprous oxide containing defects can serve as a catalyst to be applied to the fields of catalytic decomposition of ammonium perchlorate and the like and has good industrial application prospects.

Description

Technical Field

[0001] The present invention relates to the technical field of material preparation. More specifically, the present invention relates to a preparation method and application of octahedral cuprous oxide containing defects. Background Art

[0002] Cuprous oxide (Cu2O) has attracted much attention in the fields of energy catalysis, environmental governance, etc. due to its unique optical, electrical and catalytic properties. Octahedral Cu2O exhibits excellent activity in catalytic reactions due to its highly exposed crystal planes and regular structure, but the precise regulation of the defect structure is the key to improving its performance. When preparing Cu2O by the traditional hydrothermal method, problems such as uneven defect distribution and poor crystal form integrity are often faced.

[0003] In the prior art, the rough control of the raw material ratio and reaction conditions makes it difficult to directionally guide the crystal nucleus growth process, and the defect formation mechanism is not clear. For example, improper concentration matching of the copper source and the reducing agent easily causes the imbalance of the redox reaction rate and generates irregular crystal forms; inaccurate pH adjustment will affect the stability of the coordination ions, thereby interfering with the crystal plane growth kinetics. In addition, the lack of real-time monitoring of the crystal nucleus morphology and solution state during the reaction process makes it impossible to dynamically adjust the parameters to control the defect etching degree, resulting in unstable or randomly distributed pore structures.

[0004] In terms of defect regulation, traditional methods mostly rely on the temperature or pressure changes in a single stage, without considering the stage differences in crystal nucleus nucleation, defect etching and structure stability. For example, too fast heating rate will lead to disordered growth of crystal nuclei, and insufficient stirring rate during the etching stage is difficult to achieve uniform distribution of defects. At the same time, improper parameter selection during the washing and drying process is likely to cause product agglomeration or structure damage, affecting the final catalytic performance.

[0005] Due to the lack of a staged linkage control strategy and real-time monitoring means, it is difficult for the prior art to achieve controllable introduction of defects while constructing the octahedral crystal form, resulting in insufficient activity and stability of the product in applications such as ammonium perchlorate catalytic decomposition. Therefore, there is an urgent need for a preparation method that precisely regulates the raw material ratio, reaction conditions and staged monitoring to solve the problems of difficult defect structure regulation and poor crystal form uniformity. Summary of the Invention

[0006] An object of the present invention is to provide a preparation method and application of octahedral cuprous oxide containing defects, which can realize the controllable preparation of octahedral cuprous oxide containing defects through specific raw material ratio and reaction steps, and solve the problems of irregular crystal form and uneven defect distribution.

[0007] To achieve these objects and other advantages of the present invention, according to one aspect of the present invention, the present invention provides a preparation method of octahedral cuprous oxide containing defects, comprising the following steps: Step 1: Mix a copper source solution with a concentration of 0.05 - 0.15 M, a glucose solution with a concentration of 0.05 - 0.15 M, a sodium citrate solution with a concentration of 0.03 - 0.08 M, and an ammonium fluoride solution with a concentration of 0.03 - 0.08 M in a volume ratio of 1:(0.8 - 1.2):(0.8 - 1.1):(0.9 - 1.2), stir evenly, and adjust the pH to 10.5 - 11 to obtain a mixed solution; Step 2: Place the mixed solution obtained in Step 1 into a high-pressure reaction kettle, seal it, and gradually heat it to 140 - 165 °C in stages, and the reaction lasts for 4 - 6 h; Step 3: After the reaction is completed, cool the reaction kettle to room temperature, take out the reaction solution, centrifuge and filter to separate the precipitate, wash it, and dry it to obtain the defective octahedral cuprous oxide. Among them, the copper source solution is a precursor solution that provides copper ions (Cu²⁺), and water-soluble copper salts such as copper nitrate and copper sulfate can be selected; the glucose solution is used as a reducing agent to reduce Cu²⁺ to Cu⁺, and then form Cu2O crystal nuclei. The concentration matches that of the copper source solution (0.05 - 0.15 M) to ensure the balance of the redox reaction; the sodium citrate solution is used as a complexing agent to form a stable complex with Cu²⁺, adjust the release rate of copper ions, and control the crystal growth kinetics; the ammonium fluoride solution is used as an etching agent, and the F⁻ ions act on the surface of Cu2O to induce the formation of defects and pore structures. In the present invention, by reasonably adjusting the concentrations of the copper source, reducing agent, surfactant, and ammonium fluoride, the crystal morphology and pore structure of cuprous oxide are effectively controlled. In particular, the addition of ammonium fluoride can not only inhibit the over-reduction of copper ions and promote the formation of the octahedral structure, but also trigger the generation of crystal surface defects and pores through the action of fluoride ions, significantly improving the specific surface area and catalytic performance of cuprous oxide.

[0008] Preferably, in Step 1, the copper source solution, glucose solution, sodium citrate solution, and ammonium fluoride solution are sequentially added to the reaction vessel, magnetically stirred at 200 - 400 rpm for 10 - 20 min to form a premixed solution, and a 1 M NaOH solution is added dropwise to the premixed solution at a dropping rate of 1.0 - 2.0 mL / min to initially adjust the pH to 10, and then a 1 M NaOH solution is added dropwise at a dropping rate of 0.2 - 0.5 mL / min to slowly adjust the pH to 10.5 - 11, and continue stirring for 30 - 60 min to obtain a mixed solution.

[0009] Preferably, in Step 2, a multi-stage continuous heating method is adopted, specifically: Nucleation orientation stage: Heat the system to 140 - 145 °C at a rate of 3 - 5 °C / min, control the stirring rate at 100 - 200 rpm, keep the temperature constant for 1 - 2 h, and stabilize the system pressure at 1.0 - 1.5 MPa; Monitor the morphology of the crystal nuclei through on-line XRD. When the octahedral crystal nuclei are mature, enter the next stage; Defect dynamic etching stage: Further increase the temperature to 160 - 165 °C at a rate of 1 - 2 °C / min, increase the stirring rate to 300 - 500 rpm, and control the pressure ≤ 2.5 MPa; Monitor the conductivity of the solution in real time. When the fluctuation amplitude of the conductivity ≤ ±0.1 mS / cm -1 ·min -1 , enter the next stage; Hole stabilization stage: Further decrease the temperature to 150 °C at a rate of 0.5 - 1.0 °C / min, reduce the stirring rate to 50 - 100 rpm, keep the temperature constant for 0.5 - 1 h, and control the pressure ≤ 1.0 MPa through the pressure relief valve.

[0010] In the nucleation orientation stage, by controlling the heating rate, stirring rate and pressure, Cu2O is guided to preferentially form octahedral crystal nuclei, inhibiting the formation of other crystal forms (such as cubes, spheres), and ensuring the orderly growth of the {111} and {200} crystal planes of the crystal nuclei.

[0011] Defect dynamic etching stage: Utilize the selective etching effect of fluoride ions on the surface of the Cu2O crystal to form nanoscale holes on the surface of the crystal nuclei and form nanosheets in the holes. At the same time, control the etching depth and uniformity by adjusting the temperature and stirring rate.

[0012] Hole stabilization stage: By reducing the temperature and pressure and slow stirring, fix the hole and nanosheet structures formed by etching, avoid excessive expansion or collapse of the holes under high temperature and high pressure, and ensure the stability of the defect structure.

[0013] Preferably, the monitoring of the crystal nucleus morphology through on-line XRD specifically includes the following steps: Collect the diffraction peak data of crystal planes (111), (200), (211) at a frequency of 10 - 30 seconds / time using an on-line XRD probe; When the full width at half maximum (FWHM) of the diffraction peak of crystal plane (111) ≤ 0.3° and the peak intensity ratio of crystal plane (200) / crystal plane (211) ≥ 1.2, it is determined that the octahedral crystal nuclei are mature; If the FWHM of the diffraction peak of crystal plane (111) > 0.3°, trigger the heating rate to be reduced to 1 - 2 °C / min and the stirring rate to be increased to 300 - 400 rpm until the FWHM ≤ 0.3°; If the peak intensity ratio of crystal plane (200) / crystal plane (211) < 1.2, ammonium fluoride solution is additionally added at a rate of 0.1 - 0.3 mL / min until the peak intensity ratio ≥ 1.2.

[0014] The on-line XRD monitoring uses a high-temperature and high-pressure resistant probe installed on the inner wall of the reaction kettle to collect crystal plane diffraction data in real time, dynamically judge the maturity of crystal nuclei, and avoid time lag and sample contamination caused by off-line detection.

[0015] The full width at half maximum is a parameter reflecting the crystallinity of the crystal plane. The smaller the full width at half maximum, the more orderly the arrangement of atoms on the crystal plane and the stronger the regularity of the octahedral crystal nuclei. The diffraction peak intensity ratio of crystal planes (200) and (211) is used to quantify the growth orientation of octahedral crystal nuclei. A ratio ≥ 1.2 indicates that crystal plane (200) is dominant, conforming to the characteristics of the octahedral crystal form. The increase in the intensity of crystal plane (211) indicates the formation of surface pores and nanosheet structures, but its intensity is still lower than that of crystal plane (200). The degree of defect regulation needs to be quantified by the ratio of (200) / (211).

[0016] Preferably, the on-line XRD probe is installed on the inner wall of the high-pressure reaction kettle. It uses a high-temperature and high-pressure resistant X-ray diffraction probe. The material of the probe window is beryllium or diamond. The diffraction intensity signal is obtained through a high-speed data acquisition module. The wavelet transform algorithm is used to eliminate noise interference and extract the original diffraction peaks of crystal planes (111), (200), and (211). Based on the Lorentz fitting model, the full width at half maximum and the peak intensity ratio of the diffraction peaks of each crystal plane are calculated, and the fitting error ≤ ±0.02°.

[0017] The on-line XRD probe can be fixed to the inner wall of the reaction kettle through a high-pressure sealing flange. The window faces the center of the reaction solution and forms a 45° angle with the horizontal plane to avoid signal occlusion by the stirring paddle. The probe is equipped with a high-speed detector to collect diffraction signals at a frequency of 10 Hz and transmit them to the signal processing unit through a shielded cable. First, the wavelet transform algorithm (db5 wavelet basis, 5-layer decomposition) is used to remove noise, for example, filtering out high-frequency vibration noise caused by stirring (>100 Hz) and low-frequency drift noise of the heating element (<0.1 Hz), and retaining the characteristic signals of crystal plane diffraction (10 - 50 Hz). Then, based on the Lorentz fitting model, the diffraction peaks of crystal planes (111), (200), and (211) are fitted to calculate the full width at half maximum and the peak intensity ratio. The parameters are automatically optimized during the fitting process to ensure that the error is controlled within ±0.015°. The on-line XRD real-time monitoring and feedback regulation solve the problem that the maturity of crystal nuclei in traditional methods depends on empirical judgment. Through quantitative parameter control, the growth directivity of the octahedral characteristic crystal planes of crystal nuclei is increased by 40%, avoiding the problem of uneven defects caused by the etching stage when the crystal nuclei are not mature.

[0018] Preferably, the real-time monitoring of the solution conductivity specifically includes the following steps: The conductivity data of the solution is collected in real time by a conductivity sensor, and the amplitude of conductivity fluctuation is calculated, which is defined as the moving window average of the absolute value of the conductivity change per minute, and the window width is 5 min; When the amplitude of conductivity fluctuation in three consecutive windows ≤ ±0.1 mS·cm -1 ·min -1 , it is determined that the dynamic etching stage of the defect is completed; If the amplitude of conductivity fluctuation continuously > ±0.1 mS·cm -1 ·min -1 for more than 10 min, the temperature is adjusted back to 155 - 158 °C, and the stirring rate is increased to 400 - 500 rpm until the amplitude of conductivity fluctuation ≤ ±0.1 mS·cm -1 ·min -1 .

[0019] Among them, the amplitude of conductivity fluctuation is defined as the moving window average of the absolute value of the conductivity change per minute (window width 5 min), which reflects the dynamic change of the ion concentration in the solution and indirectly characterizes the dissolution - deposition equilibrium state of the ions on the crystal surface during the defect etching process.

[0020] Real - time monitoring and feedback control: The data is collected in real time through a conductivity sensor. When the fluctuation amplitude exceeds the threshold, the temperature and stirring rate are automatically adjusted to make the etching process return to a stable state, avoiding over - etching or under - etching.

[0021] The conductivity sensor (four - electrode type, the probe material is zirconia ceramic) is horizontally installed on the inner wall of the reaction kettle through a high - pressure sealing flange. The probe extends below the liquid level, avoiding the strong shear area of the stirring paddle to ensure that representative data of the main body of the solution is collected. The sensor collects conductivity signals at a frequency of 10 Hz. After being converted by a 24 - bit high - precision analog - to - digital converter, it is transmitted to the control system through an industrial Ethernet. The real - time monitoring of conductivity provides a dynamic feedback mechanism for defect etching, solving the problem that the etching end point in traditional methods depends on empirical judgment. The four - electrode sensor eliminates the electrode polarization effect, and the measurement accuracy reaches ±0.1%, which is 5 times higher than that of the two - electrode sensor. The optimized installation position of the probe avoids stirring interference, enabling the conductivity data to truly reflect the change of ion concentration during the etching process. When over - etching occurs, adjusting the temperature and stirring rate can restore stability within 15 min, avoiding the excessive expansion of the hole structure; when under - etching occurs, accelerating mass transfer can increase the etching efficiency by 25%.

[0022] Preferably, the conductivity sensor adopts a four - electrode conductivity sensor resistant to high temperature and high pressure, the sensor probe material is titanium alloy or zirconia ceramic, and the conductivity sensor is installed on the inner wall of the high - pressure reaction kettle through a high - pressure sealing flange; The conductivity sensor collects conductivity signals in real time through a high-precision analog-to-digital converter, with a sampling frequency of 10 Hz; the original signal is processed by wavelet denoising to filter out mechanical vibration and electromagnetic interference noise, and the conductivity data of the solution is obtained.

[0023] Among them, the four-electrode conductivity sensor includes two measurement electrodes and two current electrodes. By applying a constant current and measuring the voltage drop, the influence of electrode polarization and solution resistance is eliminated, which is suitable for accurate measurement in high ion concentration and high pressure environments.

[0024] Wavelet denoising processing: Aiming at the mechanical vibration noise (such as the thermal expansion vibration during the heating of the reaction kettle) and electromagnetic interference (such as the noise of motors and frequency converters) in the conductivity signal, multi-scale decomposition is carried out through wavelet transform to retain the real signal components and improve the data reliability.

[0025] The sensor probe is made of titanium alloy (the surface is treated by anodic oxidation to enhance corrosion resistance), and is vertically installed on the inner wall of the reaction kettle through an O-ring high-pressure seal flange. The top of the probe is ensured to be in the middle layer area with relatively weak solution turbulence, reducing the interference of bubbles and eddies generated by the stirring paddle. The high-precision analog-to-digital converter (sampling frequency 10 Hz) is integrated inside the sensor to collect the original conductivity signal in real time, and then it is processed by a wavelet denoising algorithm (selecting the sym8 wavelet basis and decomposing 4 layers), setting a soft threshold to remove noise and retaining the low-frequency signal (<10 Hz) reflecting the change of ion concentration. The processed signal is transmitted to the PLC control system for real-time calculation of the fluctuation amplitude and triggering of the control logic.

[0026] The combination of the four-electrode sensor and the optimized installation position improves the stability of conductivity measurement. The corrosion resistance of the titanium alloy probe ensures the measurement accuracy during long-term use, and compared with the stainless steel probe, the service life is extended. The wavelet denoising processing effectively filters out the power frequency interference generated by the stirring motor and the noise generated by the vibration of the reaction kettle, improving the signal-to-noise ratio of the conductivity signal. The optimized monitoring system can capture the minute ion concentration changes (such as fluctuations of 0.05 mS / cm⁻¹) during the etching process, providing a precise control basis for defect dynamic etching, ensuring that the hole depth and density on the surface of each octahedral crystal are consistent, and ultimately improving the uniformity of the catalytic active sites of the product.

[0027] Preferably, the specific process of step three is as follows: Centrifuge the reaction solution at a speed of 8000 - 12000 rpm for 5 - 10 min to separate the precipitate; Wash the precipitate with deionized water three times, with the amount of water used each time being 5 to 10 times the volume of the precipitate, the stirring rate being 200 to 400 rpm, and the stirring time being 5 min; then wash it with absolute ethanol twice, with the amount of ethanol used each time being 3 to 5 times the volume of the precipitate, and perform ultrasonic-assisted washing for 10 min; Place the washed precipitate in a vacuum drying oven, control the temperature to be 50 to 70 °C, the vacuum degree to be -0.08 to -0.1 MPa, and dry for 10 to 14 h to obtain the defective octahedral cuprous oxide.

[0028] The present invention also provides that the surface of the defective octahedral cuprous oxide prepared by the preparation method of the defective octahedral cuprous oxide contains a plurality of defective pores, and the defective pores are filled with nanosheets.

[0029] The present invention also provides the application of the defective octahedral cuprous oxide as a catalyst in the catalytic decomposition of ammonium perchlorate.

[0030] The reaction mechanism of the present invention is specifically as follows: 1. Dissolution and complexation of the copper source: In an aqueous solution, the copper source (such as copper chloride or copper acetate) first dissolves to generate Cu²⁺ ions. These Cu²⁺ ions undergo complexation with sodium citrate in the solution to form a copper-sodium citrate complex. The formation of this complex helps to stabilize the copper ions and prevent their premature precipitation during the reduction process, thereby controlling the reduction process of copper.

[0031] 2. Reduction effect of glucose: Glucose (as a reducing agent) undergoes a reduction reaction with Cu²⁺ ions through its alcohol group (-OH) in an alkaline environment to generate Cu⁺ ions. At this time, copper(II) is reduced to copper(I) cuprous oxide (Cu2O) and begins to crystallize. The reduction effect of glucose not only provides electrons but also may control the morphology of the generated cuprous oxide through its molecular structure, promoting the formation of an octahedral structure.

[0032] 3. Role of ammonium fluoride: Ammonium fluoride (NH4HF2) releases fluoride ions (F⁻) in water. The fluoride ions may form complexes with copper(I) ions, inhibit the excessive aggregation of copper(I), prevent the formation of irregular crystal morphologies, and promote the formation of an octahedral crystal structure. In addition, the fluoride ions in ammonium fluoride may promote the formation of a pore structure by inducing surface defects. The participation of fluoride ions may lead to differences in the local crystal growth rate, thereby forming pores inside the crystal.

[0033] 4. Role of the alkaline environment: NaOH provides an alkaline environment, which is crucial for the crystal growth of cuprous oxide. The alkaline environment helps to promote the reduction of copper(II) and stabilize the structure of cuprous oxide (Cu2O). In addition, NaOH may control the crystal growth direction by regulating the pH value, thereby controlling the formation and distribution of pores.

[0034] 5. Formation of octahedral crystals and generation of pores: During the hydrothermal reaction process, as the temperature increases, the crystals of cuprous oxide (Cu2O) begin to crystallize into an octahedral shape. Crystal surface defects, the role of ammonium fluoride on the crystal planes, and the reducing agent in the solution may act together to cause pores to form on the surface of octahedral cuprous oxide, and small nanosheets to form within the pores. The role of fluoride ions may be to inhibit the excessive deposition of copper ions, resulting in irregular crystal growth, causing an irregular pore structure on the surface of the octahedron and small nanosheets to form within the pores. This pore structure and the nanosheets within the pores can increase the specific surface area of the material, contributing to its catalytic performance.

[0035] 6. Formation mechanism of pores and nanosheets: Fluoride ions may interact with the surface of cuprous oxide (Cu2O) crystals to induce defects within the crystal. Especially during the crystal growth process, the growth rate of certain local regions is slowed down, leading to the formation of pores. Sodium citrate acts as a surfactant in the solution, reducing the interfacial tension and inhibiting the excessive growth of crystals, helping to form smaller nanoparticles or sheet-like structures. The pores provide a local reaction environment that allows nanosheets to grow inside them. At the same time, sodium citrate can form a stable hydration layer, reducing the aggregation between nanoparticles and promoting the oriented growth of nanosheets within the pores.

[0036] In the present invention, the copper source (such as copper chloride or copper acetate) forms a complex with sodium citrate after dissolution to stabilize copper ions. Glucose acts as a reducing agent to reduce copper(II) to copper(I). Ammonium fluoride promotes the formation of the morphology, pores, and nanosheet structure of octahedral cuprous oxide by providing fluoride ions. Fluoride ions control the formation of pores and nanosheets by inhibiting excessive crystal growth and inducing surface defects. The alkaline environment (NaOH) helps to maintain the stability of cuprous oxide crystals and promotes the formation of the octahedral structure.

[0037] The present invention has at least the following beneficial effects: The present invention provides a preparation method and application of octahedral cuprous oxide with defects. By defining the concentrations and volume ratios of copper source, glucose, sodium citrate, and ammonium fluoride, combined with specific pH adjustment and hydrothermal reaction conditions, it ensures the directional formation of octahedral crystal nuclei and the preliminary induction of defects, laying a foundation for subsequent defect regulation. The prepared product has regular crystal forms and uniform defect distribution. By adjusting the pH step by step and controlling the stirring parameters, it avoids the excessive local concentration caused by the rapid addition of NaOH solution, ensures the stable formation of coordination ions, improves the uniformity of the premixed solution, promotes the orderly growth of crystal nuclei in the subsequent reaction, and reduces the generation of irregular crystal forms. Its multi-stage linkage control realizes the directional nucleation of crystal nuclei, dynamic etching of defects, and stability of pores by adjusting the temperature, stirring rate, and pressure in stages, precisely regulating the defect formation process, avoiding the blindness of traditional single-stage regulation, and significantly improving the controllability of the defect structure and the consistency of the product structure. Using online XRD to monitor the morphology of crystal nuclei in real time, quantitatively judging the maturity of crystal nuclei through diffraction peak data, and timely adjusting the heating rate and stirring parameters to ensure that only qualified crystal nuclei enter the etching stage, avoiding the problem of uneven defects caused by immature crystal nuclei from the source and improving the product quality. Its XRD probe resistant to high temperature and high pressure and efficient data processing technology ensure the stable acquisition of crystal plane diffraction data under harsh reaction conditions, eliminate noise interference, and accurately calculate the full width at half maximum and peak intensity ratio, providing a reliable basis for judging the maturity of crystal nuclei and improving the accuracy of the regulation strategy. Using real-time monitoring of conductivity combined with a dynamic adjustment mechanism, accurately judging the end point of defect etching through the fluctuation amplitude of conductivity, avoiding structural damage caused by over-etching or unclear defects caused by insufficient etching, ensuring that the defect structure is fully formed and remains stable, and optimizing the catalytic performance of the product. Optimizing the installation position and material of the conductivity sensor, combined with high-precision signal acquisition and noise reduction processing, effectively reduces the influence of mechanical vibration and electromagnetic interference on the data, ensures that the conductivity data truly reflects the solution state, and provides a reliable reference for the control of the defect etching stage. Through specific centrifugation, washing, and drying parameters, the precipitate is efficiently separated by high-speed centrifugation, residual impurities are removed by multi-stage washing, and vacuum drying avoids oxidation and agglomeration, ensuring the high purity and structural integrity of the product, providing a good foundation for its application in the catalytic field.

[0038] Other advantages, objectives, and features of the present invention will be partially reflected by the following description, and partially will be understood by those skilled in the art through the research and practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 SEM image of the defective octahedral cuprous oxide prepared in Example 1; Figure 2 SEM image of the octahedral cuprous oxide prepared in Comparative Example 1; Figure 3XRD pattern of the defective octahedral cuprous oxide prepared in Example 1; Figure 4 XRD pattern of the octahedral cuprous oxide prepared in Comparative Example 1; Figure 5 TG curve and DTG curve of the decomposition of ammonium perchlorate catalyzed by the defective octahedral cuprous oxide prepared in Example 1; Figure 6 TG curve and DTG curve of the decomposition of ammonium perchlorate catalyzed by the octahedral cuprous oxide prepared in Comparative Example 1. Detailed implementation manners

[0040] The present invention will be further described in detail below in conjunction with the accompanying drawings and specific implementation manners, so that those skilled in the art can implement it according to the description in the specification.

[0041] It should be understood that the terms such as "having", "comprising" and "including" used herein do not exclude the presence or addition of one or more other elements or their combinations.

[0042] It should be noted that the experimental methods described in the following implementation examples are all conventional methods unless otherwise specified, and the reagents and materials can be obtained from commercial channels unless otherwise specified.

[0043] Example 1 Preparation of defective octahedral cuprous oxide Solution preparation Copper source solution: Weigh 1.70 g of copper chloride dihydrate (CuCl2·2H2O), dissolve it in 100 mL of deionized water, and stir until completely dissolved to obtain a copper source solution with a concentration of 0.1 M.

[0044] Glucose solution: Weigh 1.80 g of glucose, dissolve it in 100 mL of deionized water to obtain a glucose solution with a concentration of 0.1 M.

[0045] Sodium citrate solution: Weigh 1.47 g of sodium citrate, dissolve it in 100 mL of deionized water to obtain a sodium citrate solution with a concentration of 0.05 M.

[0046] Ammonium fluoride solution: Weigh 0.38 g of ammonium fluoride, dissolve it in 100 mL of deionized water to obtain an ammonium fluoride solution with a concentration of 0.05 M.

[0047] Solution mixing and pH adjustment According to the volume ratio of 1:1:1:1 (copper source solution: glucose solution: sodium citrate solution: ammonium fluoride solution), take 10 mL of copper source solution, 10 mL of glucose solution, 10 mL of sodium citrate solution, and 10 mL of ammonium fluoride solution, and add them to a 250 mL reaction vessel in sequence.

[0048] Magnetically stir at 300 rpm for 15 min to form a premixed solution.

[0049] Dropwise add 1 M NaOH solution to the premixed solution at a rate of 1.5 mL / min, adjust the pH to 10.8, and continue stirring for 30 min to obtain a mixed solution.

[0050] Hydrothermal reaction Transfer the mixed solution to a 50 mL high-pressure reactor (lined with polytetrafluoroethylene), seal it, and heat it to 160 °C at a rate of 4 °C / min, and maintain the temperature for reaction for 5 h.

[0051] Post-treatment After the reaction is completed, naturally cool it to room temperature, take out the reaction solution, centrifuge it at 10000 rpm for 8 min to separate the precipitate.

[0052] Wash the precipitate with deionized water 3 times (the amount of water used each time is 8 times the volume of the precipitate, stirring rate 300 rpm, stirring for 5 min), and then wash it with absolute ethanol 2 times (the amount of ethanol used each time is 4 times the volume of the precipitate, ultrasonic-assisted washing for 10 min).

[0053] Place the washed precipitate in a vacuum drying oven, control the temperature at 60 °C and the vacuum degree at -0.09 MPa, and dry it for 12 h to obtain octahedral cuprous oxide with defects.

[0054] Example 2: Preparation of premixed solution and stepwise pH adjustment Solution preparation Same as Example 1, prepare 0.1 M copper chloride solution, 0.1 M glucose solution, 0.05 M sodium citrate solution, and 0.05 M ammonium fluoride solution.

[0055] Solution mixing and pre-stirring Take 20 mL of copper source solution, 16 mL of glucose solution (volume ratio 1:0.8), 18 mL of sodium citrate solution (volume ratio 1:0.9), and 20 mL of ammonium fluoride solution (volume ratio 1:1), and add them to the reaction vessel in sequence.

[0056] Magnetically stir at 200 rpm for 20 min to form a premixed solution.

[0057] Stepwise pH adjustment First, dropwise add 1 M NaOH solution at a rate of 2.0 mL / min to adjust the pH of the premixed solution to 10, which takes about 5 min.

[0058] Subsequently, slowly dropwise add NaOH solution at a rate of 0.2 mL / min for 30 min to precisely adjust the pH to 10.5, while maintaining the stirring rate at 400 rpm.

[0059] After the pH was stabilized, stirring was continued for 60 min to allow the components to fully complex and obtain a uniformly mixed solution.

[0060] Subsequent steps The hydrothermal reaction and post-treatment were the same as in Example 1.

[0061] In this example, by using a "fast first and then slow" NaOH dropping rate (2.0 mL / min → 0.2 mL / min), the interference of sudden pH changes on the copper ion complexation reaction was avoided. The stirring rate of the premixed solution was gradually increased from 200 rpm to 400 rpm to ensure that sodium citrate and Cu²⁺ fully formed a stable complex, inhibit premature precipitation of copper ions, and improve the uniformity of pore distribution.

[0062] Example 3: Multi-stage linkage hydrothermal reaction control Solution preparation and mixing Same as Example 2.

[0063] Hardware configuration XRD probe: A diamond window high-temperature and high-pressure resistant probe (temperature resistance 200 °C, pressure resistance 3 MPa) was used and fixed to the inner wall of the reaction kettle through a flange. The axis of the probe was perpendicular to the liquid surface and 5 cm away from the bottom of the kettle.

[0064] Data acquisition: A high-speed data acquisition module (sampling frequency 10 Hz) was used to obtain the diffraction intensity signal in real time, and mechanical vibration noise (such as the vibration interference of the stirring paddle) was filtered by the wavelet transform algorithm (decomposition level 3 layers).

[0065] Data processing: The crystal plane parameters were calculated based on the Lorentz fitting model, and the fitting error was controlled within ±0.015°.

[0066] Conductivity sensor configuration Probe material: A titanium alloy probe (platinum-plated on the surface to improve corrosion resistance) was used and vertically installed on the inner wall of the reaction kettle through a high-pressure sealing flange. The top of the probe was 1 / 3 of the height from the liquid surface (suitable for a 50 mL reaction kettle, liquid surface height 10 cm, and the probe extended 3.3 cm).

[0067] Signal acquisition: A high-precision analog-to-digital converter (sampling frequency 10 Hz) transmitted the signal in real time, and mechanical vibration noise (such as the thermal expansion noise during the heating of the reaction kettle) was removed by the wavelet transform algorithm (db4 wavelet basis, 5-layer decomposition).

[0068] Nucleation stage of crystal nucleus orientation The reaction kettle was heated to 140 °C (heating rate 5 °C / min), the stirring rate was 200 rpm, and it was kept at a constant temperature for 1 h.

[0069] The on-line XRD probe (window material: beryllium, installed on the inner wall of the reactor) collects crystal plane data at a frequency of 30 seconds per time: When it is detected that the full width at half maximum of (111) = 0.35° (>0.3°), the regulation mechanism is triggered: the heating rate is reduced to 1°C / min, the stirring rate is increased to 300 rpm. After 30 min, the full width at half maximum is reduced to 0.28°, meeting the maturation condition.

[0070] If the peak intensity ratio of (200) / (211) = 1.1 (<1.2), ammonium fluoride solution (0.05 M) is added at a rate of 0.2 mL / min. After 5 min, the peak intensity ratio rises to 1.3, reaching the standard.

[0071] Defect dynamic etching stage When the temperature rises to 160°C and the stirring rate is 300 rpm, the initial fluctuation amplitude of the conductivity is 0.15 mS・cm⁻¹・min⁻¹ (>0.1), triggering regulation: the heating rate is reduced to 1°C / min, the stirring rate is increased to 400 rpm. After 15 min, the fluctuation amplitude is reduced to 0.09 mS・cm⁻¹・min⁻¹, meeting the condition and entering the pore stability stage.

[0072] Pore stability stage Cool down to 150°C at a rate of 0.5°C / min, reduce the stirring rate to 80 rpm, control the pressure ≤1.0 MPa through the pressure relief valve, and keep it at a constant temperature for 1 h.

[0073] Post-treatment Same as Example 2.

[0074] The multi-stage control strategy realizes the coordinated regulation of crystal nucleus growth and defect etching through differential temperature, stirring rate, and pressure parameters. The low-temperature and low-speed stirring (145°C, 150 rpm) in the nucleation stage promotes the regular growth of octahedral crystal nuclei. The high-temperature and high-speed stirring (165°C, 400 rpm) in the etching stage enhances the etching effect of fluoride ions on the crystal surface, forming uniform pores. The temperature and pressure reduction (150°C, 0.8 MPa) in the stabilization stage ensures the fixation of the pore structure and avoids crystal collapse caused by excessive etching. Online XRD monitoring judges the maturity of crystal nuclei in real time through quantitative indicators (full width at half maximum ≤ 0.3°, peak intensity ratio ≥ 1.2), preventing immature crystal nuclei from entering the etching stage. When the full width at half maximum exceeds the standard, reducing the heating rate and increasing the stirring rate can enhance mass transfer in the solution and promote the regular growth of crystal planes. When the peak intensity ratio is insufficient, ammonium fluoride is added to adjust the crystal plane growth kinetics through fluoride ions, ensuring the preferential growth of the {200} crystal plane of octahedral crystal nuclei. By using real-time monitoring of conductivity combined with a dynamic adjustment mechanism, the end point of defect etching is accurately judged through the amplitude of conductivity fluctuations, avoiding structural damage caused by excessive etching or unclear defects caused by insufficient etching, ensuring that the defect structure is fully formed and stable, and optimizing the catalytic performance of the product.

[0075] Example 4: Optimization of the post-treatment process The solution preparation and hydrothermal reaction are the same as in Example 3.

[0076] Centrifugal separation After the reaction solution is cooled, it is transferred to a centrifuge tube and centrifuged at 12000 rpm for 5 min to separate the precipitate.

[0077] Multi-stage washing Washing with deionized water: Each time, use deionized water 10 times the volume of the precipitate, stir at 400 rpm for 5 min, and wash 3 times to remove water-soluble impurities such as residual NaOH and sodium citrate.

[0078] Washing with absolute ethanol: Each time, use absolute ethanol 5 times the volume of the precipitate, and wash with ultrasonic assistance for 10 min (ultrasonic frequency 40 kHz) to remove glucose and residual ammonium fluoride adsorbed on the crystal surface.

[0079] Vacuum drying Lay the washed precipitate flat in a petri dish, place it in a vacuum drying oven, control the temperature at 70°C and the vacuum degree at -0.1 MPa, and dry for 10 h.

[0080] High-speed centrifugation (12,000 rpm) ensures the efficient separation of tiny particles (50 - 100 nm), improving the precipitation recovery rate. In multi-stage washing, a high dosage of deionized water (10 times) and high-speed stirring (400 rpm) effectively remove polar impurities. The ultrasonic washing with anhydrous ethanol utilizes the cavitation effect to remove non-polar residues, enhancing the product purity. The vacuum drying parameters (70°C, -0.1 MPa) avoid the oxidation of cuprous oxide while shortening the drying time.

[0081] Comparative Example 1: The ammonium fluoride solution was omitted. The difference from Example 1 lies in that the ammonium fluoride solution was not added in Step 1, and the concentrations and volume ratios of the other raw materials remained unchanged (copper source: glucose: sodium citrate = 1:1:1).

[0082] The cuprous oxide products obtained in Example 1 and Comparative Example 1 were subjected to scanning electron microscopy (SEM) measurement, X-ray diffraction (XRD) measurement, and thermogravimetric analysis measurement of the decomposition of ammonium perchlorate (AP) for comparison. The results are as Figures 1 to 6 shown.

[0083] Among them, the thermogravimetric analysis measurement method for the decomposition of ammonium perchlorate (AP) is as follows: 5 mg of the dried powder products obtained in Example 1 and Comparative Example 1 were respectively taken, and ground and mixed with 50 mg of ammonium perchlorate (AP, analytical pure, particle size ≤ 50 μm) in an agate mortar for 5 min to evenly disperse the catalyst on the surface of AP particles. The analysis and test were carried out using a thermogravimetric analyzer.

[0084] From Figure 1 the SEM images, it can be seen that the octahedral cuprous oxide prepared in Example 1 has multiple defect holes on its surface, and the defect holes are filled with micro-nanosheets. While Figure 2 from the SEM images of Comparative Example 1, it can be seen that the surface of the octahedral cuprous oxide prepared is smooth and has no defect holes. This is because the addition of ammonium fluoride in Example 1 induces uniform holes on the octahedral surface through the etching effect of F⁻ ions (defect dynamic etching stage) and the coordination effect (inhibiting the excessive aggregation of Cu⁺), and promotes the growth of nanosheets in the holes. In Comparative Example 1, the F⁻ ions are absent, the etching effect disappears, and the crystal plane growth is mainly based on the thermodynamically stable smooth surface, and the "hole-sheet" structure cannot be formed.

[0085] From Figure 3 and Figure 4 the XRD patterns, it can be seen that the crystal forms of the products in Example 1 and Comparative Example 1 both belong to cuprous oxide, and there are no impurity peaks in both, indicating that ammonium fluoride only regulates the surface structure and does not change the bulk composition of Cu2O, excluding the compositional changes in the bulk phase and confirming that the defects are surface controllable modifications. And the defect-free cuprous oxide ( Figure 4Compared with , the peak area of defective cuprous oxide becomes wider, indicating that its crystal grains are smaller and there are certain defects such as dislocations and vacancies inside the material. In addition, the (211) crystal plane of defective cuprous oxide is significantly higher than that of defect-free cuprous oxide. The (211) plane helps to form nanostructures (such as nanosheets or nanowires) beneficial to catalytic and optoelectronic properties, improving the specific surface area and reaction activity of the material.

[0086] From Figure 5 and Figure 6 ' TG curve, it can be seen that the defective octahedral cuprous oxide prepared in Example 1 causes ammonium perchlorate (AP) to start decomposing earlier and complete the decomposition earlier, greatly promoting the decomposition process of AP. From the DTG curve, it can be seen that the defective octahedral cuprous oxide changes the DTG decomposition peak of AP from two to one, indicating that the defective catalyst changes the original two-step decomposition of AP into one-step decomposition.

[0087] Take the cuprous oxide products prepared in Examples 1 to 4 and Comparative Example 1 as samples, and measure their specific surface areas respectively. The specific method is as follows: Take about 50 mg of the sample and place it in a glass sample tube, and connect it to a vacuum degassing station.

[0088] Degas at a vacuum degree ≤ 10⁻³ Pa and a temperature of 150 °C for 4 h to remove the water, organic matter and impurity gases adsorbed on the surface (to avoid interfering with the adsorption process).

[0089] After degassing, quickly transfer it to the sample chamber of the sorption analyzer and maintain a vacuum environment until the test starts.

[0090] Instrument: Micromeritics ASAP 2020 static volumetric specific surface area analyzer (Micromeritics, USA).

[0091] Adsorbate: High-purity nitrogen (purity ≥ 99.999%, purified by a liquid nitrogen cold trap).

[0092] Test temperature: Liquid nitrogen temperature (77.35 K, maintained by continuously replenishing liquid nitrogen through a Dewar flask).

[0093] 3. Test procedure Vacuum calibration: Before the test, calibrate the instrument pipeline under vacuum (pressure ≤ 10⁻ 6 Pa) to eliminate the dead volume error.

[0094] Adsorption isotherm determination: Inject a certain amount of nitrogen into the sample tube, measure the pressure change after equilibrium, and calculate the adsorption amount (corrected based on the ideal gas state equation PV = nRT).

[0095] Measure the adsorption branch and desorption branch data in sequence. The equilibrium time at each pressure point is ≥ 5 min (extended to 10 min in the micropore region).

[0096] Data processing: Calculate the specific surface area using the multi-point BET method.

[0097] Fit with the Brunauer - Emmett - Teller (BET) equation. The formula is: ; where V is the adsorption volume at the equilibrium pressure P, V m is the monolayer adsorption volume, and C is the BET constant (reflecting the interaction strength between the adsorbent and the adsorbate).

[0098] The measurement results are shown in Table 1.

[0099] Table 1 The results show that the specific surface area of the defective octahedral cuprous oxide prepared in Examples 1 - 4 is 12 - 14 m² / g, which is significantly higher than that of Comparative Example 1. The core reason is the defects and pore structures induced by ammonium fluoride: F⁻ ions in ammonium fluoride induce crystal plane defects during the hydrothermal reaction, promoting pore formation, and the filling of nanosheets further increases the surface roughness.

[0100] The specific surface area of Example 4 is the highest, attributed to the precise regulation in the crystal nucleus oriented nucleation stage (more regular crystal plane growth and uniform defect distribution), high - speed stirring (400 rpm) in the etching stage to enhance fluoride ion mass transfer and form more through - channels, and the optimization of the post - treatment process.

[0101] When there is no ammonium fluoride in Comparative Example 1, the absence of F⁻ ions leads to the disappearance of the etching effect, and the crystal surface is mainly smooth, with the specific surface area close to that of dense cuprous oxide (5 - 6 m² / g).

[0102] Although the embodiments of the present invention have been disclosed as above, they are not limited to only the applications listed in the specification and embodiments. It can be fully applied to various fields suitable for the present invention. For those familiar with the field, additional modifications can be easily made. Therefore, without departing from the general concept defined by the claims and the equivalent scope, the present invention is not limited to the specific details and the examples shown and described herein.

Claims

1. A method for preparing defective octahedral cuprous oxide, characterized in that: The following steps are involved: Step 1, mixing a copper source solution with a concentration of 0.05-0.15M, a glucose solution with a concentration of 0.05-0.15M, a sodium citrate solution with a concentration of 0.03-0.08M, and an ammonium fluoride solution with a concentration of 0.03-0.08M in a volume ratio of 1: (0.8-1.2): (0.8-1.1): (0.9-1.2), stirring evenly, and adjusting the pH to 10.5-11 to obtain a mixed solution; Step 2: placing the mixed solution obtained in step 1 in a high pressure reactor, sealing it and heating it in stages to 140-165° C., and continuing the reaction for 4-6 hours; Step 3: After the reaction is completed, the reactor is cooled to room temperature, the reaction solution is taken out, centrifuged, filtered to separate the precipitate, washed, and dried to obtain the defective octahedral cuprous oxide.

2. The method for preparing defective octahedral cuprous oxide according to claim 1, characterized in that: In the step 1, the copper source solution, the glucose solution, the sodium citrate solution and the ammonium fluoride solution are sequentially added to the reaction container, and magnetic stirring is performed at 200-400 rpm for 10-20 min to form a premixed solution, and a 1 M NaOH solution is added dropwise to the premixed solution at a dropping speed of 1.0-2.0 mL / min, and the pH is initially adjusted to 10, and then a 1 M NaOH solution is added dropwise at a dropping speed of 0.2-0.5 mL / min, and the pH is slowly adjusted to 10.5-11, and stirring is continued for 30-60 min to obtain a mixed solution.

3. The method for preparing defective octahedral cuprous oxide according to claim 1, characterized in that: The step 2 adopts a multi-stage continuous heating method, specifically: Directed nucleation stage: the temperature is raised to 140-145°C at a rate of 3-5°C / min, the stirring rate is controlled to 100-200rpm, and the constant temperature is maintained for 1-2 hours to stabilize the system pressure at 1.0-1.5 MPa; the nucleus morphology is monitored by online XRD, and when the octahedral nucleus is mature, it enters the next stage; Defect dynamic etching stage: further increase the temperature to 160-165°C at 1-2°C / min, increase the stirring rate to 300-500 rpm, and control the pressure ≤2.5 MPa; monitor the solution conductivity in real time, and when the conductivity fluctuation range is ≤±0.1 mS / cm -1 ·min -1 When the time comes, enter the next stage; Pore ​​stabilization stage: further reduce the temperature to 150°C at a rate of 0.5~1.0°C / min, reduce the stirring rate to 50~100rpm, maintain the constant temperature for 0.5~1 h, and control the pressure to ≤1.0 MPa through the pressure release valve.

4. The method for preparing defective octahedral cuprous oxide according to claim 3, characterized in that: The monitoring of the crystal nucleus morphology by online XRD specifically comprises the following steps: The diffraction peak data of the crystal planes (111), (200), and (211) were collected using an online XRD probe at a frequency of 10 to 30 seconds per time; When the half-peak width of the diffraction peak of the crystal plane (111) is ≤0.3° and the peak intensity ratio of the crystal plane (200) / crystal plane (211) is ≥1.2, the octahedral nucleus is determined to be mature; If the half-peak width of the diffraction peak of the crystal plane (111) is greater than 0.3°, the trigger heating rate is reduced to 1~2°C / min, and the stirring rate is increased to 300~400 rpm until the half-peak width is ≤0.3°; If the peak intensity ratio of the crystal plane (200) / crystal plane (211) is less than 1.2, additional ammonium fluoride solution is added at an acceleration rate of 0.1-0.3 mL / min until the peak intensity ratio is ≥1.

2.

5. The method for preparing defective octahedral cuprous oxide according to claim 4, characterized in that: The online XRD probe is installed on the inner wall of the high-pressure reactor. It adopts a high-temperature and high-pressure resistant X-ray diffraction probe. The probe window material is beryllium or diamond. The diffraction intensity signal is obtained through a high-speed data acquisition module. The wavelet transform algorithm is used to eliminate noise interference and extract the original diffraction peaks of the crystal planes (111), (200), and (211). The half-peak width and peak intensity ratio of the diffraction peaks of each crystal plane are calculated based on the Lorentz fitting model, and the fitting error is ≤±0.02°.

6. The method for preparing defective octahedral cuprous oxide according to claim 3, characterized in that: The real-time monitoring of solution conductivity specifically comprises the following steps: The conductivity sensor is used to collect the solution conductivity data in real time and calculate the conductivity fluctuation amplitude, which is defined as the sliding window average of the absolute value of the conductivity change per minute, with a window width of 5 minutes. When the conductivity fluctuation range of three consecutive windows is ≤±0.1mS·cm -1 ·min -1 When , it is determined that the defect dynamic etching stage is completed; If the conductivity fluctuation range continues to be > ±0.1 mS·cm -1 ·min -1 If the temperature exceeds 10 min, adjust the temperature back to 155-158°C and increase the stirring rate to 400-500 rpm until the conductivity fluctuation is ≤±0.1 mS·cm -1 ·min -1 .

7. The method for preparing defective octahedral cuprous oxide according to claim 6, characterized in that: The conductivity sensor adopts a high temperature and high pressure resistant four-electrode conductivity sensor, the sensor probe is made of titanium alloy or zirconia ceramic, and the conductivity sensor is installed on the inner wall of the high pressure reactor through a high pressure sealing flange; The conductivity sensor collects conductivity signals in real time through a high-precision analog-to-digital converter with a sampling frequency of 10 Hz; wavelet noise reduction is performed on the original signal to filter out mechanical vibration and electromagnetic interference noise, thereby obtaining solution conductivity data.

8. The method for preparing defective octahedral cuprous oxide according to claim 1, characterized in that: The specific process of step three is: The reaction solution was centrifuged at 8000-12000 rpm for 5-10 min to separate the precipitate; First, wash the precipitate with deionized water for 3 times, with the amount of water used each time being 5 to 10 times the volume of the precipitate, stirring at a rate of 200 to 400 rpm for 5 min; then wash it with anhydrous ethanol for 2 times, with the amount of ethanol used each time being 3 to 5 times the volume of the precipitate, and perform ultrasonic-assisted washing for 10 min; The washed precipitate is placed in a vacuum drying oven, the temperature is controlled to be 50-70° C., the vacuum degree is -0.08--0.1 MPa, and it is dried for 10-14 h to obtain the defective octahedral cuprous oxide.

9. The defective octahedral cuprous oxide prepared by the method for preparing defective octahedral cuprous oxide according to any one of claims 1 to 8, characterized in that: The surface of the defective octahedral cuprous oxide contains a plurality of defect holes, and the defect holes are filled with nanosheets.

10. Use of the defective octahedral cuprous oxide according to claim 9 as a catalyst in the catalytic decomposition of ammonium perchlorate.

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