A method for preparing gallium-based oxides in different crystalline forms and applications thereof
By combining precipitation with calcination and plasma pretreatment, the preparation process of gallium-based oxides was simplified, solving the problems of high temperature and high energy consumption and difficulty in controlling metastable phases, and realizing the efficient catalytic conversion of gallium-based oxides into CO2.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- XIAN UNIV OF SCI & TECH
- Filing Date
- 2026-05-09
- Publication Date
- 2026-06-19
AI Technical Summary
Existing methods for preparing gallium-based oxides suffer from problems such as high temperature and high energy consumption, difficulty in controlling metastable phases, and complicated processes. Traditional thermocatalytic CO2 conversion processes have high energy consumption and limited selectivity, while plasma catalytic systems have low energy efficiency and poor product selectivity.
By combining precipitation with calcination and plasma pretreatment, the crystal form of gallium-based oxides can be controlled. α-Ga2O3, β-Ga2O3, and ε-Ga2O3 can be prepared through low-temperature calcination and plasma treatment, simplifying the process and reducing costs.
Selective and controllable preparation of three crystal forms was achieved, reducing the thermal budget, suppressing high-temperature phase transitions, improving surface defects, and enhancing the catalytic activity and CO2 conversion efficiency of the catalyst.
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Figure CN122233425A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of CO2 resource utilization technology, specifically to a method and application for preparing gallium-based oxides with different crystal forms. Background Technology
[0002] The efficient conversion and resource utilization of carbon dioxide (CO2) has become a research hotspot in the fields of energy, chemical engineering, and materials. Traditional thermocatalytic CO2 conversion processes are usually limited by reaction thermodynamic equilibrium and kinetic obstacles, often requiring high temperature and high pressure conditions, resulting in high energy consumption, limited reaction selectivity, and easy catalyst sintering and deactivation.
[0003] Dielectric barrier discharge (DBD) plasma technology exhibits unique advantages in CO2 activation due to its ability to excite high-energy electrons, free radicals, excited-state molecules, and other active species at room temperature and pressure. However, standalone plasma systems suffer from low energy efficiency, poor product selectivity, and uncontrollable reaction pathways, which severely restrict their industrial applications.
[0004] In recent years, plasma-catalyst synergistic systems have been considered an important approach to overcoming the bottleneck in CO2 conversion. For example, alkali metal oxide catalysts can be synergistically combined with plasma to catalyze CO2 conversion, as alkali metals readily convert acidic CO2 gases. Alternatively, semiconductor oxide catalysts can be synergistically combined with DBD plasma, utilizing the catalyst's excellent electronic band structure and active sites to catalyze CO2 conversion. In these systems, the catalyst not only provides adsorption and reaction sites but also regulates the distribution, lifetime, and reaction pathways of active species within the plasma, achieving efficient energy utilization and enhanced reaction selectivity.
[0005] Gallium-based oxides, as an important class of semiconductor oxide materials, generally suffer from problems such as high temperature and high energy consumption, difficulty in controlling metastable phases, and cumbersome processes in their existing preparation methods. For example, the traditional melt growth of β-Ga2O3 requires temperatures exceeding 1000℃ and relies on noble metal crucibles, while metastable phases such as α-Ga2O3 and ε-Ga2O3 often require complex epitaxial processes (such as metal-organic chemical vapor deposition, molecular beam epitaxy, etc., which require precise temperature control and buffer layer design) and expensive substrates (their preparation cost is high due to reliance on noble iridium crucibles) due to their poor thermal stability, and they are also prone to uncontrollable phase transitions. Summary of the Invention
[0006] To address the aforementioned problems, this invention provides a method and application for preparing gallium-based oxides with different crystal forms. For the α and β crystal forms, a precursor is obtained via precipitation, followed by calcination and plasma pretreatment to achieve crystal form control and surface defect generation at relatively low temperatures. For the ε crystal form, direct calcination and plasma treatment allow for stable pure phase preparation without relying on a specific substrate. Active species in the plasma, such as high-energy electrons, free radicals, and excited-state molecules, effectively reduce the thermal budget, suppress high-temperature phase transitions, and improve surface defects. This method simplifies the process, reduces costs, and enables selective and controllable preparation of the three crystal forms, solving the problems of high temperature and high energy consumption, difficulty in controlling metastable phases, and cumbersome processes in existing preparation methods.
[0007] To achieve the above objectives, the present invention adopts the following technical solution: The purpose of this invention is to provide a method for preparing gallium-based oxides with different crystal forms, comprising the following steps: Using gallium source and precipitant as raw materials, precipitation is carried out in a solvent system to obtain a precursor; the precursor is calcined at 450℃~800℃ and then subjected to plasma pretreatment to obtain gallium-based oxide; the gallium-based oxide is α-Ga2O3 or β-Ga2O3.
[0008] Alternatively, gallium source can be used as raw material, calcined at 150℃~600℃, and then subjected to plasma treatment to obtain gallium-based oxide; the gallium-based oxide is ε-Ga2O3.
[0009] In a preferred embodiment of the present invention, when the gallium-based oxide is α-Ga2O3 or β-Ga2O3, the mass ratio of gallium source to anhydrous sodium carbonate is 3:2 to 2.2, the gallium source is gallium nitrate, the precipitant is anhydrous sodium carbonate, ammonia or urea, and the solvent is water.
[0010] In a preferred embodiment of the present invention, the plasma treatment power is 60W~70W and the time is 10min~30min.
[0011] In a preferred embodiment of the present invention, when the gallium-based oxide is α-Ga2O3, the calcination temperature is 450℃~500℃ and the time is 3h~5h.
[0012] In a preferred embodiment of the present invention, when the gallium-based oxide is β-Ga2O3, the calcination temperature is 750℃~800℃ and the time is 3h~5h.
[0013] In a preferred embodiment of the present invention, when the gallium-based oxide is ε-Ga2O3, the calcination is carried out in a stepwise calcination manner, which is to calcine at 150℃~250℃ for 18h~20h, followed by calcination at 400℃~600℃ for 6h~8h.
[0014] In a preferred embodiment of the present invention, when the gallium-based oxide is α-Ga2O3 or β-Ga2O3, it needs to be aged after precipitation to obtain the precursor; the aging temperature is 70℃~90℃ and the time is 12h~24h.
[0015] Another object of the present invention is to provide an application of gallium-based oxides prepared by the above-described method for preparing gallium-based oxides with different crystal forms in the catalytic conversion of CO2.
[0016] Compared with the prior art, the beneficial effects of the present invention are: 1. This invention provides a method for preparing gallium-based oxides with different crystal forms. For α and β crystal forms, a precursor is obtained by precipitation, followed by calcination and plasma pretreatment, which allows for crystal form control and surface defect generation at relatively low temperatures. For ε crystal form, a pure phase can be stably obtained without relying on a specific substrate through direct calcination and plasma treatment. Active species in the plasma, such as high-energy electrons, free radicals, and excited-state molecules, effectively reduce the thermal budget, suppress high-temperature phase transitions, and improve the surface defects of gallium-based oxides. This method simplifies the process, reduces costs, and achieves selective and controllable preparation of three crystal forms, demonstrating good industrialization prospects. It thus solves the problems of high temperature and high energy consumption, difficulty in controlling metastable phases, and cumbersome processes in existing preparation methods.
[0017] 2. Among the gallium-based oxides provided by the present invention, β-Ga2O3 has a moderate band gap and the highest oxygen vacancy concentration, making it superior to α-Ga2O3 and ε-Ga2O3 in terms of electron transport capability and oxygen free radical capture capability.
[0018] 3. This invention provides the application of gallium-based oxides in the catalytic conversion of CO2. When β-Ga2O3 is applied to the catalytic conversion of CO2, the CO2 conversion rate can reach a stable period of 26.7%. The CO selectivity and energy efficiency are better than α-Ga2O3 and ε-Ga2O3, and the performance is better than commercial Ga2O3. Attached Figure Description
[0019] Figure 1 The images show the XRD patterns of different crystal forms of Ga2O3 according to the present invention.
[0020] Figure 2 The UV images show different crystal forms of Ga2O3 according to the present invention.
[0021] Figure 3 The images show the EPR test results of Ga2O3 with different crystal forms according to the present invention.
[0022] Figure 4 XPS images of Ga2O3 with different crystal forms according to the present invention. Figure 4Figure a shows the full spectrum, figure b shows the Ga 2d spectrum, and figure c shows the O 1s spectrum.
[0023] Figure 5 This is a stability diagram of Ga2O3 with different crystal forms according to the present invention.
[0024] Figure 6 This is a graph showing the CO2 conversion rate of Ga2O3 with different crystal forms according to the present invention.
[0025] Figure 7 This is a CO selectivity diagram for different crystal forms of Ga2O3 according to the present invention.
[0026] Figure 8 This is a diagram showing the energy efficiency of Ga2O3 with different crystal forms according to the present invention.
[0027] Figure 9 This is a graph showing the CO2 conversion rate of commercial Ga2O3 according to the present invention. Detailed Implementation
[0028] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.
[0029] It should be noted that the technical terms used in this invention are only for the purpose of describing specific embodiments and are not intended to limit the scope of protection of this invention. Unless otherwise specified, all raw materials, reagents, instruments and equipment used in the following embodiments of this invention can be purchased from the market or prepared by existing methods.
[0030] Gallium-based oxides, as an important class of semiconductor oxide materials, generally suffer from high temperature and high energy consumption, difficulty in controlling metastable phases, and cumbersome processes in existing preparation methods. For example, traditional melt growth of β-Ga₂O₃ requires temperatures exceeding 1000℃ and relies on noble metal crucibles, while metastable phases such as α-Ga₂O₃ and ε-Ga₂O₃ often require complex epitaxial processes and expensive substrates due to their poor thermal stability, and are prone to uncontrollable phase transitions. To address these shortcomings, this invention proposes two technical routes: for α and β crystal forms, a precipitation method is used to obtain the precursor, followed by calcination and plasma pretreatment, which allows for crystal form control and surface defect generation at lower temperatures; for the ε crystal form, direct calcination and plasma treatment allow for stable pure phase acquisition without relying on a specific substrate. The active species in the plasma effectively reduce the thermal budget, suppress high-temperature phase transitions, and improve surface defects. Overall, this method simplifies the process, reduces costs, and achieves selective and controllable preparation of three crystal forms, overcoming existing technical bottlenecks and possessing promising industrialization prospects.
[0031] First, this invention provides a method for preparing gallium-based oxides with different crystal forms, comprising the following steps: Using gallium source and precipitant as raw materials, precipitation is carried out in a solvent system to obtain a precursor; the precursor is calcined at 450℃~800℃ and then subjected to plasma pretreatment to obtain gallium-based oxide; the gallium-based oxide is α-Ga2O3 or β-Ga2O3.
[0032] Alternatively, gallium source can be used as raw material, calcined at 150℃~600℃, and then subjected to plasma treatment to obtain gallium-based oxide; the gallium-based oxide is ε-Ga2O3.
[0033] It should be noted that this invention synergizes the non-equilibrium high-energy activation characteristics of DBD plasma with the diverse crystal structure system of gallium oxide materials. By directionally controlling the crystal form of Ga2O3, the relationship between catalytic performance and crystal structure is established, thereby breaking through the limitations of single crystal forms in catalytic activity, product selectivity, and reaction stability. The essence of this invention is to transform the traditional "material-performance" system into a "crystal structure-plasma environment-synergistic catalytic effect" model.
[0034] When the gallium-based oxide is α-Ga₂O₃, the specific preparation process is as follows: Gallium nitrate is dissolved in deionized water to obtain a gallium nitrate solution. Anhydrous sodium carbonate is dissolved in deionized water to obtain a precipitant. Then, under stirring at 80℃ and 800 rpm, the precipitant is added dropwise to the gallium nitrate solution using a syringe pump to ensure thorough mixing and form a mixed solution. When the pH of the mixed solution reaches 7-8, the addition is stopped, and stirring continues for 3-5 hours to ensure complete precipitation. After stirring, the resulting solution is aged, filtered, and washed until most impurity ions are removed. After filtration, the precipitate is dried to obtain GaOOH powder, the precursor. The GaOOH powder is placed in a muffle furnace and calcined at 450℃-500℃ for 3-5 hours to obtain calcined powder. The calcined powder is pretreated in a DBD reactor to obtain α-Ga₂O₃ powder.
[0035] When the gallium-based oxide is β-Ga₂O₃, the specific preparation process is as follows: Gallium nitrate is dissolved in deionized water to obtain a gallium nitrate solution. Anhydrous sodium carbonate is dissolved in deionized water to obtain a precipitant. Then, under stirring at 70℃~90℃ and 700 rpm~900 rpm, the precipitant is added dropwise to the gallium nitrate solution using a syringe pump to ensure thorough mixing and form a mixed solution. When the pH of the mixed solution reaches 7~8, the addition is stopped, and stirring continues for 3h~5h to ensure complete precipitation. After stirring, the resulting solution is aged, filtered, and washed until most impurity ions are removed. After filtration, the precipitate is dried to obtain GaOOH powder, the precursor. The GaOOH powder is placed in a muffle furnace and calcined at 750℃~800℃ for 3h~5h to obtain calcined powder. The calcined powder is pretreated in a DBD reactor to obtain β-Ga₂O₃ powder.
[0036] In the above process, the mass-to-volume ratio of gallium nitrate to deionized water in the gallium nitrate solution was 3 g:50 mL. In the precipitant, the mass-to-volume ratio of anhydrous sodium carbonate to deionized water was 2.12 g:100 mL. The injection rate of the syringe pump was 110 mL / h to 130 mL / h. The aging temperature was 70℃ to 90℃, and the time was 12 h to 24 h. The drying temperature was 70℃ to 90℃, and the time was 12 h to 24 h.
[0037] When the gallium-based oxide is ε-Ga₂O₃, the specific preparation process is as follows: Gallium nitrate is placed in a muffle furnace and calcined at 150℃~250℃ for 18h~20h to obtain δ-Ga₂O₃ powder. The δ-Ga₂O₃ powder is then placed in a muffle furnace and calcined at 400℃~600℃ for 6h~8h to obtain ε-Ga₂O₃ powder. This ε-Ga₂O₃ powder is then pretreated in a DBD reactor to obtain ε-Ga₂O₃ powder.
[0038] The plasma treatment has a power of 60W to 70W and a time of 10min to 30min, preferably 20min.
[0039] Secondly, the present invention provides a gallium-based oxide prepared by the above method.
[0040] Gallium-based oxides are characterized by diverse crystal forms, wide band gaps, excellent chemical stability, great electrical potential, and low cost.
[0041] Finally, the present invention provides an application of the above-mentioned gallium-based oxide in the catalytic conversion of CO2.
[0042] This invention utilizes high-energy electrons generated by DBD plasma to continuously bombard CO2 flowing through a region, causing it to dissociate. A gallium-based oxide catalyst is then introduced to adsorb and activate the CO2, facilitating further reaction. Simultaneously, the plasma bombardment process may create more oxygen vacancies on the catalyst surface; these vacancies are favorable active sites for CO2 adsorption and activation, further promoting CO2 dissociation. Through deep synergy of physical and chemical processes, highly efficient activation and directional conversion of CO2 molecules are achieved under relatively mild conditions.
[0043] Compared to photocatalysis and thermocatalysis, the core mechanism of this invention relies on the continuous bombardment of carbon dioxide in the flowing region by the generated low-temperature plasma. This avoids the high energy consumption and easy carbon deposition problems of high-temperature thermocatalysis, and also overcomes the limitation of ordinary photocatalysis by the intensity of the light source. Simultaneously, a Ga2O3 catalyst is added to the carbon dioxide flowing region. Utilizing the unique wide bandgap and easy defect formation properties of Ga2O3, the high-energy electron energy of the DBD plasma is effectively captured and converted into chemical reducing power, selectively converting carbon dioxide into carbon monoxide and oxygen.
[0044] The following specific examples will provide further explanation.
[0045] Example 1 A method for preparing α-Ga2O3 includes the following steps: 3g of gallium nitrate was dissolved in 50mL of deionized water to obtain a precursor solution. 2.12g of anhydrous sodium carbonate was dissolved in 100mL of deionized water to obtain a precipitant. Then, under stirring at 80℃ and 800 rpm, the precipitant was slowly added dropwise to the precursor solution using a syringe pump at a rate of 120mL / h, ensuring thorough mixing to form a mixed solution. Addition was stopped when the pH of the mixed solution reached 7, and stirring continued for 4h to ensure complete precipitation. After stirring, the resulting solution was aged at 80℃ for 24h. The aged solution was filtered and repeatedly washed until most impurity ions were removed. After filtration, the precipitate was dried in an oven at 80℃ for 24h to obtain GaOOH powder. The GaOOH powder was placed in a muffle furnace and calcined at 450℃ for 4h to obtain calcined powder. The calcined powder was pretreated in a DBD reactor at 60W for 20min to obtain α-Ga₂O₃ powder.
[0046] Example 2 A method for preparing β-Ga2O3 includes the following steps: 3g of gallium nitrate was dissolved in 50mL of deionized water to obtain a precursor solution. 2.12g of anhydrous sodium carbonate was dissolved in 100mL of deionized water to obtain a precipitant. Then, under stirring at 80℃ and 800 rpm, the precipitant was slowly added dropwise to the precursor solution using a syringe pump at a rate of 120mL / h, ensuring thorough mixing to form a mixed solution. Addition was stopped when the pH of the mixed solution reached 7, and stirring continued for 4h to ensure complete precipitation. After stirring, the resulting solution was aged at 80℃ for 24h. The aged solution was filtered and repeatedly washed until most impurity ions were removed. After filtration, the precipitate was dried in an oven at 80℃ for 24h to obtain GaOOH powder. The GaOOH powder was placed in a muffle furnace and calcined at 750℃ for 4h to obtain calcined powder. The calcined powder was pretreated in a DBD reactor at 60W for 20min to obtain β-Ga₂O₃ powder.
[0047] Example 3 A method for preparing ε-Ga2O3 includes the following steps: 3g of gallium nitrate was placed in a muffle furnace and calcined at 200℃ for 18h to obtain δ-Ga2O3 powder. The δ-Ga2O3 powder was then placed in a muffle furnace and calcined at 500℃ for 6h to obtain ε-Ga2O3 powder. The ε-Ga2O3 powder was then pretreated in a DBD reactor at 60W for 20min to obtain ε-Ga2O3 powder.
[0048] The Ga2O3 with different crystal forms prepared in Examples 1 to 3 were characterized and their performance was tested.
[0049] Figure 1 These are XRD patterns of Ga₂O₃ with different crystal forms according to the present invention. Figure 1 It can be seen that the diffraction peaks of the α-Ga₂O₃ and β-Ga₂O₃ samples prepared by precipitation method are highly consistent with their PDF cards, and no obvious impurity phase peaks were observed. ε-Ga₂O₃, however, belongs to metastable gallium oxide, and its diffraction peaks are broad.
[0050] Figure 2 The UV images show different crystal forms of Ga2O3 according to the present invention. Figure 3 These are EPR test results for different crystal forms of Ga2O3 according to the present invention. Figures 2-3 It can be seen that β-Ga2O3 has a moderate band gap and a higher oxygen vacancy concentration compared with α-Ga2O3 and ε-Ga2O3, which indicates that β-Ga2O3 has excellent electron transport ability and oxygen free radical capture ability.
[0051] Figure 4 XPS images of Ga2O3 with different crystal forms according to the present invention. Figure 4 Figure a shows the full spectrum, figure b shows the Ga 2d spectrum, and figure c shows the O 1s spectrum. (From...) Figure 4 It can be seen that in the α-Ga2O3, β-Ga2O3 and ε-Ga2O3 samples, Ga has a +3 valence and O has a -2 valence.
[0052] Next, this invention demonstrates the application of different crystal forms of Ga2O3 in the catalytic conversion of CO2. Specifically, 0.2 g of catalyst was introduced into the DBD system using the in-catalyst integration (IPC) method. The CO2 inlet gas flow rate was set to 20 mL / min. Tests were conducted at input power levels of 35 W, 50 W, 65 W, and 80 W. The collected gases were then analyzed using a gas chromatograph to determine the CO2 conversion rate, CO selectivity, and energy efficiency. For stability testing, the input power was controlled at 80 W, and the collected gases were analyzed every 15 minutes to determine the stability.
[0053] Figure 5 This is a stability diagram of Ga2O3 with different crystal forms according to the present invention. Figure 5 It can be seen that β-Ga2O3 has excellent stability, and the CO2 conversion rate can be maintained at 26.7%. No catalyst deactivation was found during the 24-hour test. However, α-Ga2O3 and ε-Ga2O3 performed poorly, with CO2 conversion rates of 22.5% and 24.5% during the stable period, respectively.
[0054] Figure 6 This is a graph showing the CO2 conversion rate of Ga2O3 with different crystal forms according to the present invention. Figure 7 This is a CO selectivity diagram for different crystal forms of Ga2O3 according to the present invention. Figure 8This is a diagram showing the energy efficiency of different crystal forms of Ga2O3 according to the present invention. Figures 6-8 It can be seen that the CO2 conversion rate, CO selectivity, and energy efficiency ratio all follow the order: β-Ga2O3 > ε-Ga2O3 > α-Ga2O3. This is consistent with the characterization test results, indicating that β-Ga2O3 has excellent performance in the field of DBD plasma catalytic conversion of carbon dioxide.
[0055] Finally, this invention tested the CO2 conversion rate of commercial gallium oxide, i.e., β-crystal Ga2O3, under different input powers. Figure 9 This is a graph showing the CO2 conversion rate of commercial Ga2O3 according to the present invention. (Source: [Insert Source Here]) Figure 9 It is known that the optimal CO2 conversion rate of commercial Ga2O3 is 25.1%, which is lower than that of the prepared β-Ga2O3. The reason why the conversion rate of commercial β-gallium oxide is better than that of the α-Ga2O3 and ε-Ga2O3 of this invention is that α-Ga2O3 and ε-Ga2O3 are metastable crystal forms, while β-Ga2O3 is the most stable crystal form.
[0056] It should be noted that when numerical ranges are involved in this invention, it should be understood that both endpoints of each numerical range, as well as any value between the two endpoints, can be selected. Since the steps and methods used are the same as in the embodiments, preferred embodiments are described here to avoid redundancy. Although preferred embodiments of this invention have been described, those skilled in the art, once they understand the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the appended scope of protection is intended to be interpreted as including the preferred embodiments and all changes and modifications falling within the scope of this invention.
[0057] Obviously, those skilled in the art can make various modifications and variations to this invention without departing from its spirit and scope. Therefore, if these modifications and variations fall within the scope of protection of this invention and its equivalents, this invention also intends to include these modifications and variations.
Claims
1. A method for preparing gallium-based oxides with different crystal forms, characterized in that, Includes the following steps: Using gallium source and precipitant as raw materials, precipitation is carried out in a solvent system to obtain a precursor; the precursor is calcined at 450℃~800℃ and then subjected to plasma pretreatment to obtain gallium-based oxide; the gallium-based oxide is α-Ga2O3 or β-Ga2O3. Alternatively, gallium source can be used as raw material, calcined at 150℃~600℃, and then subjected to plasma treatment to obtain gallium-based oxide; the gallium-based oxide is ε-Ga2O3.
2. The method for preparing gallium-based oxides with different crystal forms according to claim 1, characterized in that, When the gallium-based oxide is α-Ga2O3 or β-Ga2O3, the mass ratio of gallium source to anhydrous sodium carbonate is 3:2~2.2, the gallium source is gallium nitrate, the precipitant is anhydrous sodium carbonate, ammonia or urea, and the solvent is water.
3. The method for preparing gallium-based oxides with different crystal forms according to claim 1, characterized in that, The plasma treatment power is 60W~70W, and the time is 10min~30min.
4. The method for preparing gallium-based oxides with different crystal forms according to claim 1, characterized in that, When the gallium-based oxide is α-Ga2O3, the calcination temperature is 450℃~500℃ and the time is 3h~5h.
5. The method for preparing gallium-based oxides with different crystal forms according to claim 1, characterized in that, When the gallium-based oxide is β-Ga2O3, the calcination temperature is 750℃~800℃ and the time is 3h~5h.
6. The method for preparing gallium-based oxides with different crystal forms according to claim 1, characterized in that, When the gallium-based oxide is ε-Ga2O3, the calcination is carried out in a stepwise manner, which is to calcine at 150℃~250℃ for 18h~20h, followed by calcination at 400℃~600℃ for 6h~8h.
7. The method for preparing gallium-based oxides with different crystal forms according to claim 1, characterized in that, When the gallium-based oxide is α-Ga2O3 or β-Ga2O3, it needs to be aged after precipitation to obtain the precursor; the aging temperature is 70℃~90℃ and the time is 12h~24h.
8. The application of gallium-based oxides prepared by the method for preparing gallium-based oxides of different crystal forms according to any one of claims 1 to 7 in the catalytic conversion of CO2.