Method for low-temperature liquid-phase preparation of nano indium-based catalyst

Abstract

The invention discloses a method for low-temperature liquid-phase preparation of a nano indium-based catalyst in the field of material chemistry and photocatalysis, which comprises the following steps: dissolving solid indium salt in liquid-phase N, N-dimethylformamide, and carrying out ultrasonic dispersion to obtain a solution A; adding deionized water into the solution A, and stirring to obtain a solution B; adding an ammonium hydroxide solution into the solution B, adjusting the pH value to 8.0, and continuously stirring to obtain a solution C; the solution C is transferred into a reaction bottle to be sealed, the reaction bottle is placed in a drying oven to be subjected to a liquid phase reaction, the reaction time is 2-12 h, the temperature of the drying oven is 90-120 DEG C, and a product D of indium oxide and hydroxyl indium oxide is generated; separating the product D by using a centrifugal method to obtain a precipitate E; and drying the precipitate E to obtain the indium-based catalyst. According to the method, the unique effect of N, N-dimethylformamide (DMF) in liquid phase reaction is combined, through solvent conditions, reaction concentration and temperature, complex treatment steps such as high-temperature calcination are avoided, low-temperature liquid phase direct preparation of the nano indium-based catalyst is achieved, and the physical and chemical characteristics of the indium-based catalyst can be accurately regulated and controlled.

Description

Technical Field

[0001] The invention belongs to the field of material chemistry and photocatalysis, and in particular relates to a method for synthesizing an indium-based catalyst by adopting a low-temperature liquid phase method. Background Art

[0002] Indium-based materials (such as InOOH and In2O3) have great application potential in the fields of energy and environment due to their excellent photocatalytic performance and chemical stability. For example, indium oxide (In2O3), as an n-type wide bandgap semiconductor (bandgap is about 2.7-3.6 eV), not only shows excellent performance in photocatalysis, but is also widely used in gas sensors, transparent conductive electrodes and electrochemical electrode materials. In addition, indium oxyhydroxide (InOOH), as an important precursor of In2O3, not only has good processability, but is also used in the fields of molecular sieves and catalytic carriers due to its porous structure.

[0003] Traditional methods for preparing indium-based materials mainly include high-temperature solid-phase method, hydrothermal method, vapor deposition method, etc. Among them, the high-temperature solid-phase method often requires a high temperature greater than or equal to 500°C, high energy consumption and difficulty in controlling the grain size and morphology of the product; the hydrothermal method needs to be carried out under high temperature and high pressure conditions. Although the crystal morphology is relatively uniform, the reaction equipment requirements are high; vapor deposition technology requires expensive equipment. These preparation processes rely on high-temperature calcination or heat treatment. Under high temperature conditions, the grains of the material are easy to aggregate, resulting in a decrease in specific surface area, thereby limiting the catalytic performance.

[0004] In recent years, in order to reduce energy consumption and improve the controllability of product morphology, low-temperature liquid phase method has gradually become an emerging preparation technology. Most of the existing liquid phase methods still rely on high-temperature hydrothermal environment or complex solvent system, which limits their practical application. For example, the method of preparing indium oxide nanomaterials by hydrothermal method published in the document with Chinese patent number 201010207646.9 uses soluble indium salt and urea to hydrothermally react at 120-140°C, and then calcined to obtain indium oxide. Although high-purity indium oxide can be prepared, this method needs to be carried out under high temperature and high pressure environment, which not only increases energy consumption, but also makes the operating conditions complicated. Another example is the paper "Preparation of In2O3nanocrystals by a low-temperaturesolution process" (Cryst.Growth Des.2008,8,2,695-699), in which the disclosed scheme is to use a hydrothermal method to react at 200°C for 24 hours to prepare indium oxide nanocrystals, but it still relies on high-temperature hydrothermal conditions, and the solvent system includes a ternary mixed solution of urea, diethylene glycol and deionized water, which is relatively complex, limiting the feasibility of its large-scale production. Although these methods can effectively control the morphology and size of the product, they still face many problems in practical applications due to the harsh reaction conditions. Therefore, the development of a method for preparing indium-based materials with low energy consumption, simple operation and controllable morphology, especially a method for directly preparing functional indium-based catalysts at relatively low temperatures, has important scientific value and application prospects. Summary of the invention

[0005] The purpose of the present invention is to solve the above-mentioned many problems that the preparation of existing indium-based catalysts all depends on high temperature conditions, and to provide a method for preparing nano indium-based catalysts in a low-temperature liquid phase based on a liquid phase reaction, thereby avoiding high-temperature processes and achieving efficient and controllable preparation of indium oxyhydroxide (InOOH) and indium oxide (In2O3).

[0006] To achieve the above object, the technical solution adopted by the method for preparing nano-indium-based catalyst in low-temperature liquid phase of the present invention comprises the following steps:

[0007] Step 1): dissolving a solid indium salt in a liquid phase of N,N-dimethylformamide and dispersing by ultrasonication to obtain a solution A;

[0008] Step 2): adding deionized water to solution A and stirring to obtain solution B;

[0009] Step 3): adding ammonium hydroxide solution to solution B, adjusting the pH to 8.0, and continuing stirring to obtain solution C;

[0010] Step 4): Transfer solution C to a reaction bottle, seal it, and place it in an oven for liquid phase reaction. The reaction time t is 2 to 12 hours, and the oven temperature is 90 to 120° C. to generate product D of indium oxide and indium oxyhydroxyl;

[0011] Step 5): The product D is washed and separated by centrifugation to obtain a precipitate E;

[0012] Step 6): Dry the precipitate E to obtain a nano-indium-based catalyst.

[0013] Furthermore, the concentration of the indium salt dissolved in the liquid phase of N,N-dimethylformamide is 1 to 100 mg / mL.

[0014] Furthermore, during the liquid phase reaction, when the indium salt concentration R is less than 20 mg / mL, indium oxide is preferentially generated; when the indium salt concentration R is greater than 50 mg / mL and the reaction time t is less than 6 h, indium oxyhydroxy is preferentially generated.

[0015] The present invention has the following advantages after adopting the above technical solution:

[0016] 1. The N,N-dimethylformamide (DMF) used in the present invention is a kind of solvent with strong polarity, which can effectively dissolve various metal salts, which makes DMF provide uniform reaction medium in liquid phase synthesis, promotes the dissolution of precursor and the full contact between reactants, thereby improving reaction efficiency. In addition, the strong polar group in the DMF molecule can form a stable coordination environment with the metal ion, prevents the metal ion from precipitating prematurely or incomplete reaction, which helps to control the purity and grain size of the product. Therefore, DMF plays the role of solvation, stabilization, and regulation reaction in liquid phase reaction as a solvent, and has multiple functions.

[0017] 2. The present invention combines the unique role of N,N-dimethylformamide (DMF) in liquid phase reactions, avoids complex processing steps such as high-temperature calcination through solvent conditions, reaction concentration and temperature, and realizes the low-temperature liquid phase direct preparation of indium-based catalysts, which makes the synthesis process more green and energy-saving, easy to operate, and suitable for industrial large-scale production.

[0018] 3. The present invention can synthesize indium-based materials with high specific surface area and specific morphology under mild conditions by regulating reaction conditions (such as solvent type, pH, temperature) and selectively adding auxiliary reagents. By controlling the combination of indium salt concentration, reaction time and solvent system, the physical and chemical properties of indium-based catalysts can be precisely regulated to achieve the selective synthesis of products InOOH and In2O3, and further optimize their catalytic performance.

[0019] 4. The present invention achieves efficient and controllable preparation of indium oxyhydroxide (InOOH) and indium oxide (In2O3) by optimizing the solvent environment, reaction temperature and indium salt concentration. The indium-based material prepared by this method under mild conditions has a high specific surface area and good morphology, which significantly improves its catalytic performance. At the same time, the process avoids the high-temperature calcination process, significantly reduces energy consumption and production costs, and meets the diversified needs of fields such as photocatalysis, gas sensing and environmental remediation. The prepared indium-based catalyst has good crystallinity, good morphology and high crystallinity, is suitable for photocatalysis, gas sensing and environmental governance, and can be widely used in the fields of photocatalysis and environmental remediation. Compared with traditional methods, the reaction temperature is significantly reduced, and the controllability is stronger, which is a green and efficient new technology path.

[0020] 5. By introducing a regulating solvent (such as a trace amount of deionized water or ammonium hydroxide) into the reaction system, the pH value and reaction kinetics of the reaction environment can be adjusted, thereby achieving precise control of the material morphology and crystal phase, which helps to obtain indium-based materials with specific properties.

[0021] 6. By adjusting the indium salt concentration and reaction time, indium oxyhydroxide (InOOH) or indium oxide (In2O3) can be selectively prepared under low temperature conditions. This controllability significantly improves the crystallization performance of indium-based catalysts.

[0022] 7. The present invention uses a wide range of raw materials, such as precursors such as indium nitrate, indium chloride or indium acetate, and the solvent system includes common organic solvents such as N,N-dimethylformamide (DMF), which has strong applicability and flexibility and can meet the customized needs of different indium-based materials. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] In order to further understand the present invention and make its objectives, technical solutions and advantages clearer, the present invention is now described in detail with reference to the accompanying drawings.

[0024] Figure 1 is a SEM image of indium oxyhydroxide (InOOH) in Example 1;

[0025] Figure 2 is the XRD pattern of indium oxide (In2O3) in Example 2;

[0026] Figure 3 is a SEM image of indium oxide (In2O3) in Example 2;

[0027] Figure 4 is the XRD pattern of indium oxyhydroxide (InOOH) in Example 3. DETAILED DESCRIPTION

[0028] The present invention uses indium salt as a precursor, and realizes the precise preparation of indium oxyhydroxide (InOOH) or indium oxide (In2O3) catalytic materials by regulating the solvent environment, reaction temperature and pH value under low-temperature liquid phase conditions, as follows:

[0029] Solid indium salt is dissolved in liquid N,N-dimethylformamide (DMF) and dispersed by ultrasonic to obtain solution A. The indium salt can be indium nitrate (In(NO3)3), indium chloride (InCl3) or indium acetate (In(Ac)3), or a mixture of any two of these three indium salts. The mass ratio R of the indium salt to the volume of DMF is in the range of 1 to 100 mg / mL, that is, the concentration of the indium salt dissolved in the liquid N,N-dimethylformamide is 1 to 100 mg / mL.

[0030] Deionized water was slowly added to solution A so that the volume of water in the system accounted for about 1-4% of the volume of DMF. After adding water, stirring was continued for 1 hour to obtain solution B.

[0031] An appropriate amount of ammonium hydroxide (NH4OH) solution was added to solution B, the pH of the reaction system was adjusted to 8.0, and stirring was continued for 30 minutes to obtain solution C. This step helps to adjust the rate of the hydrolysis reaction and promote the hydrolysis process of the indium salt.

[0032] Then, the solution C is transferred to a reaction bottle, sealed and placed in an oven for liquid phase reaction, the reaction time t is 2 to 12 hours, the oven temperature is 90 to 120°C, and the product D of indium oxide and indium oxyhydroxide is generated. During the liquid phase reaction, when the indium salt concentration R<20 mg / mL, it means that the indium salt is at a lower concentration, which promotes the generation of indium oxide (In2O3) and preferentially generates indium oxide (In2O3). When the indium salt concentration R>50 mg / mL and the reaction time t<6h, indium oxyhydroxide (InOOH) is preferentially generated. A shorter reaction time (t<6h) is conducive to the generation of InOOH, while extending the reaction time, that is, when t≥10h, the reaction will proceed further, and part of InOOH will be converted into indium oxide (In2O3). In the present invention, the selection and amount of solvent directly affect the solubility of indium salt, reaction rate and stability of the reaction system. In a high concentration of DMF solvent, indium salt can stably exist and promote the formation of InOOH; while when the amount of solvent is small, indium ions easily aggregate and form indium oxide (In2O3) crystals. The selection and concentration adjustment of different solvent systems can control the distribution and reaction rate of indium ions, thereby affecting the morphology and crystal phase of the product.

[0033] After the liquid phase reaction is completed, the product D is separated by centrifugation, the supernatant is discarded, and it is washed with anhydrous ethanol or deionized water for multiple times to remove the residual solvent and by-products to obtain a precipitate E.

[0034] Finally, the washed precipitate D was placed in a vacuum drying oven at 60° C. and dried to obtain the desired indium-based catalyst.

[0035] Three embodiments of the present invention are provided below:

[0036] Example 1

[0037] Step 1: Add 30 mL of N,N-dimethylformamide (DMF) solvent to indium nitrate (In(NO3)3), the volume ratio R of indium salt mass to DMF is 80 mg / mL, and ultrasonically disperse to completely dissolve the indium nitrate to obtain solution A.

[0038] Step 2: Slowly add deionized water to solution A so that the volume of water in the system accounts for about 1% of the volume of DMF. After adding water, continue stirring for 1 hour to obtain solution B.

[0039] Step 3: Add an appropriate amount of ammonium hydroxide (NH4OH) solution to solution B, adjust the pH of the reaction system to 8.0, and continue stirring for 30 minutes to obtain solution C.

[0040] Step 4: Transfer solution C to a 50 mL reaction bottle, seal it, and place it in an oven at 120° C. for 6 hours to obtain a reaction product D.

[0041] Step 5: Cool the product D to room temperature and separate the precipitate by centrifugation. After discarding the supernatant, wash the precipitate three times with anhydrous ethanol and deionized water alternately to remove the residual solvent and by-products, and obtain precipitate E.

[0042] Step 6: The washed precipitate E was placed in a vacuum drying oven at 60°C and dried for 12 hours to obtain Figure 1 The nano-sized indium oxyhydroxide (InOOH) powder is shown. Figure 1 The SEM image of indium oxyhydroxide (InOOH) shown in FIG. Figure 1 InOOH nanoparticles with small particle size and regular morphology are shown in the figure, which shows that the low-temperature liquid phase method can effectively control the crystal growth of the product and generate smaller catalyst particles. Such small-sized particles have a larger specific surface area, can provide more active sites, and improve their catalytic efficiency. It can be seen from the SEM image that the present invention successfully achieves the efficient synthesis of InOOH nanoparticles, which meets the demand for high-performance materials in catalytic applications.

[0043] Example 2

[0044] Step 1: Add 30 mL of N,N-dimethylformamide (DMF) solvent to indium nitrate (In(NO3)3·xH2O) and indium chloride (InCl3), the molar ratio of indium nitrate to indium chloride is 2:1, the amount ratio of indium salt to DMF is 10 mg / mL, and ultrasonic dispersion is performed for 30 minutes to obtain solution A.

[0045] Step 2: Slowly add deionized water to solution A so that the volume of water in the system accounts for about 2% of the total solvent volume (relative to the volume of DMF). After adding water, continue stirring for 1 hour to obtain solution B.

[0046] Step 3: Add an appropriate amount of ammonium hydroxide (NH4OH) solution to solution B, adjust the pH of the reaction system to 8.0, and continue stirring for 30 minutes to obtain solution C. This step helps to adjust the rate of the hydrolysis reaction and promote the hydrolysis process of the indium salt.

[0047] Step 4: Transfer solution C to a sealed reaction bottle, place it in an oven at 100° C. for reaction for 12 hours to obtain a reaction product D.

[0048] Step 5: After the reaction is completed, the reaction product D is separated into a solid product by centrifugation and washed several times with deionized water to remove residual solvent and by-products, and precipitate E.

[0049] Step 6: Place the washed precipitate E in a vacuum drying oven at 60°C and dry for 24 hours to obtain Figure 2 The indium oxide (In2O3) powder shown has good crystalline properties.

[0050] from Figure 2 It can be seen that the diffraction peak is sharp and strong, indicating that the In2O3 material has good crystallinity. In addition to the characteristic peak of In2O3, there are almost no other peaks, such as the diffraction peaks of other impurity phases such as InOOH, indicating that the synthesis method successfully avoids the formation of impurities or by-products and obtains In2O3 materials with higher purity. This shows that the proper reaction conditions such as temperature, reaction time, and solvent can effectively inhibit the formation of other phases (such as indium oxide InOOH).

[0051] like Figure 3 The SEM image shown shows that In2O3 has a good crystal structure and regular particle morphology, which indicates that the growth of the crystals during the reaction is effectively controlled. This ordered crystal structure is usually conducive to the improvement of catalytic activity. This shows that the low-temperature liquid phase synthesis method has a good ability to control the product phase and crystallinity, can effectively avoid the formation of impurities, and obtain high-performance nano-indium oxide (In2O3) materials. This is of great significance for improving catalytic performance, stability and efficiency in applications.

[0052] Example 3

[0053] Step 1: Add 30 mL of N,N-dimethylformamide (DMF) solvent to indium acetate (In(Ac)3), the dosage ratio of indium acetate to DMF is 70 mg / mL, and ultrasonically disperse for 30 minutes to obtain solution A.

[0054] Step 2: Slowly add anhydrous methanol solution to solution A to make the volume fraction of methanol in the system reach 4% of the total solvent volume (relative to the volume of DMF). After adding methanol, continue stirring for 1 hour to obtain solution B.

[0055] Step 3: Add ammonium hydroxide solution to solution B and adjust the pH to 8.0 to obtain solution C.

[0056] Step 4: Transfer solution C to a reaction bottle and heat the reaction at 90°C for 2 hours to generate product D.

[0057] Step 5: Separate product D by centrifugation, discard the supernatant, and wash with anhydrous ethanol or deionized water for multiple times to obtain precipitate E.

[0058] Step 6: The precipitate E was dried under vacuum at 60°C for 24 hours to obtain indium oxyhydroxide (InOOH) nanomaterials. Figure 4 The indium-based catalyst (InOOH) nanomaterial shown in the XRD graph shows strong diffraction peaks related to InOOH, and these peaks correspond to the crystal planes of InOOH known in the literature, which indicates that the low-temperature liquid phase method can successfully synthesize InOOH, and the reaction conditions can effectively control its crystal phase and have good crystallization properties.

Claims

1. A method for preparing nano-indium-based catalysts in a low-temperature liquid phase, characterized in that The following steps are involved: Step 1): dissolving a solid indium salt in a liquid phase of N,N-dimethylformamide and dispersing by ultrasonication to obtain a solution A; Step 2): adding deionized water to solution A and stirring to obtain solution B; Step 3): adding ammonium hydroxide solution to solution B, adjusting the pH to 8.0, and continuing stirring to obtain solution C; Step 4): Transfer solution C to a reaction bottle, seal it, and place it in an oven for liquid phase reaction. The reaction time is 2 to 12 hours, and the oven temperature is 90 to 120° C. to generate product D of indium oxide and indium oxyhydroxyl; Step 5): separating the product D by centrifugation to obtain a precipitate E; Step 6): Dry the precipitate E to obtain a nano-indium-based catalyst.

2. The method for preparing nano-indium-based catalysts in a low-temperature liquid phase according to claim 1, characterized in that: In step 1), the concentration of the indium salt dissolved in the liquid phase of N,N-dimethylformamide is 1 to 100 mg / mL.

3. The method for preparing nano-indium-based catalysts in a low-temperature liquid phase according to claim 1, characterized in that: In step 1), the indium salt is indium nitrate (In(NO3)3), indium chloride (InCl3), indium acetate (In(Ac)3) or a mixture of any two thereof.

4. The method for preparing nano-indium-based catalysts in a low-temperature liquid phase according to claim 1, characterized in that: When the indium salt is a mixture of indium nitrate and indium chloride, the molar ratio of indium nitrate to indium chloride in the system is 2:

1.

5. The method for preparing nano-indium-based catalysts in a low-temperature liquid phase according to claim 1, characterized in that: In step 2), after adding deionized water, the volume of water in the system accounts for 1-4% of the volume of N,N-dimethylformamide.

6. The method for preparing nano-indium-based catalysts in a low-temperature liquid phase according to claim 1, characterized in that: In step 4), during the liquid phase reaction, when the indium salt concentration R<20 mg / mL, indium oxide is preferentially generated; when the indium salt concentration R>50 mg / mL and the reaction time t<6 h, indium oxyhydroxy is preferentially generated.

7. The method for preparing nano-indium-based catalysts in a low-temperature liquid phase according to claim 4, characterized in that: When the indium salt concentration R>50 mg / mL and the reaction time t≥10 h, part of the indium oxyhydroxide is converted into indium oxide.

8. The method for preparing an indium-based catalyst in a low-temperature liquid phase according to claim 1, characterized in that: In step 6), the precipitate D is placed in a vacuum drying oven at 60° C. and dried for 12 hours.

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