Rhodium-based catalysts with nanospherical alpha-alumina as carrier, preparation method thereof and application thereof in photo-thermal catalysis

Abstract

The application belongs to the field of photo-thermal catalysis, and relates to a rhodium-based catalyst taking nanospherical alpha-aluminum oxide as a carrier, a preparation method of the rhodium-based catalyst and application of the rhodium-based catalyst in photo-thermal catalysis. The rhodium-based catalyst comprises nanospherical alpha-aluminum oxide carriers and rhodium nanoparticles loaded on the carriers, and the preparation method is as follows: a water solution of a rhodium-based precursor is uniformly mixed with nanospherical alpha-aluminum oxide, water is removed to obtain a powder, and then hydrogen is used for reduction reaction to reduce rhodium in the powder, and the rhodium-based catalyst is obtained. The rhodium-based photo-thermal catalyst provided by the application has the characteristics of high dispersion of active components and excellent thermal stability of a catalytic carrier, significantly enhances the adsorption and activation capacity of CO2 molecules, further improves the reaction efficiency, selectivity and catalyst stability of photo-thermal catalytic CO2 methanation, and provides an efficient and sustainable solution for realizing CO2 resource utilization.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of photo-thermal catalysis, and relates to a rhodium-based catalyst taking nanospherical alpha-aluminum oxide as a carrier, a preparation method thereof and application thereof in photo-thermal catalysis. BACKGROUND

[0002] The information disclosed in this Background section is for the purpose of increasing the understanding of the background of the present application and should not be taken as an acknowledgement or any form of suggestion that this information forms prior art with respect to any country.

[0003] Carbon dioxide (CO2) as a major greenhouse gas, its concentration continues to rise has become one of the important driving factors of global climate change. CO2 methanation reaction can alleviate the problem of global warming while producing high-calorific-value fuel, providing a new solution for energy supply and chemical production, and is an effective way to achieve "waste to treasure".

[0004] Traditional CO2 methanation technology mostly uses nickel-based catalysts at high temperature (> 300℃), which faces the problems of low activity, easy sintering, carbon deposition and high energy consumption. Photo-thermal catalysis can combine light energy and heat energy, and has the advantages of low energy consumption and high efficiency, so the development of high-efficiency photo-thermal catalyst is the key to promote the development of CO2 methanation technology. Rhodium (Rh) is the preferred noble metal for CO2 methanation due to its high catalytic activity, especially its significant role in CO2 molecule adsorption and activation and C-H bond formation (key step to improve methane selectivity). In particular, Rh can produce local photo-thermal effect to reduce the reaction activation energy under light conditions through surface plasmon resonance (SPR) effect; at the same time, SPR effect also promotes the generation of hot electrons, significantly enhances the activation and conversion ability of intermediates, and further improves the photo-thermal catalytic efficiency. However, due to the scarcity and high price of Rh resources, it is a key technical bottleneck to realize its efficient dispersion and stable loading on the basis of ensuring photo-thermal catalytic performance. SUMMARY

[0005] In view of the deficiencies in the prior art, the purpose of the present application is to provide a rhodium-based catalyst taking nanospherical alpha-aluminum oxide as a carrier, a preparation method thereof and application thereof in photo-thermal catalysis. The present application selects nanospherical alpha-aluminum oxide with excellent thermal stability and good surface structure regulation ability as a catalytic carrier, and obtains a rhodium-based photo-thermal catalyst with high dispersion of catalytically active components, excellent CO2 methanation activity in photo-thermal catalysis, high methane selectivity and good stability through simple impregnation, drying and calcination processes, which has important significance for the fields of energy, environment and catalytic materials.

[0006] In order to achieve the above purpose, the technical scheme is as follows:

[0007] In a first aspect, a rhodium-based catalyst supported on nanosphere-shaped α-alumina includes a nanosphere-shaped α-alumina support and rhodium nanoparticles loaded on the support.

[0008] Nanosphere-shaped α-alumina exhibits excellent thermal stability and good surface structure control. Furthermore, research has shown that nanosphere-shaped α-alumina, as a carrier for rhodium nanoparticles, a photothermal catalytic active material, can not only achieve efficient dispersion and stable loading of rhodium nanoparticles, but also that the catalyst formed by it has excellent photothermal catalytic CO2 methanation activity.

[0009] The nanosphere α-alumina support of this invention has a particle size of 50-200 nm. The rhodium nanoparticles of this invention are rhodium metal nanoparticles. The rhodium nanoparticles of this invention have a particle size of 0.5-8 nm. In the catalyst provided by this invention, the mass of the rhodium nanoparticles is 0.2-5% of the mass of the nanosphere α-alumina support.

[0010] Secondly, a method for preparing the above-mentioned rhodium-based catalyst supported on nano-spherical α-alumina involves mixing an aqueous solution of a rhodium-based precursor with nano-spherical α-alumina, removing water to obtain powder, and then using hydrogen to carry out a reduction reaction to reduce the rhodium in the powder, thereby obtaining the catalyst.

[0011] Mixing an aqueous solution of a rhodium-based precursor with nanospheres of α-alumina facilitates the uniform dispersion of both the rhodium-based precursor and the nanospheres of α-alumina, allowing the rhodium-based precursor to be uniformly adsorbed onto the nanospheres of α-alumina. Then, through hydrogen reduction, efficient dispersion and stable loading of rhodium nanoparticles can be achieved.

[0012] The rhodium-based precursor described in this invention is a precursor of rhodium nanoparticles, generally a rhodium salt, such as rhodium trichloride, rhodium nitrate, or rhodium sulfate.

[0013] Thirdly, the application of the above-mentioned rhodium-based catalyst supported on nanosphere α-alumina in photothermal catalysis.

[0014] Specifically, the photothermal catalysis is photothermal catalytic CO2 methanation.

[0015] The rhodium-based photothermal catalyst provided by this invention has the characteristics of highly dispersed active components and excellent thermal stability of the catalyst support, which significantly enhances the adsorption and activation ability of CO2 molecules, further improves the reaction efficiency, selectivity and catalyst stability of photothermal catalytic CO2 methanation, and provides an efficient and sustainable solution for realizing the resource utilization of CO2.

[0016] Fourthly, a method for photothermal catalytic CO2 methanation includes the following steps:

[0017] The above-mentioned rhodium-based catalyst was placed in a fixed-bed photothermal reactor, activated in a high-temperature hydrogen atmosphere and cooled to the reaction temperature. CO2 and H2 were introduced as reaction gases, and photothermal catalytic CO2 methanation was carried out under light irradiation.

[0018] The fixed-bed photothermal reactor described in this invention refers to a fixed-bed reactor equipped with a light source.

[0019] The beneficial effects of this invention are as follows:

[0020] 1. The rhodium-based photothermal catalyst provided by this invention can generate a localized photothermal effect through surface plasmon resonance (SPR) under illumination, significantly reducing the activation energy of the reaction and enhancing the activation and conversion capabilities of reaction intermediates. This photothermal synergistic effect allows the catalytic reaction to proceed at a lower temperature, thereby improving the overall photothermal catalytic efficiency while reducing energy consumption.

[0021] 2. Using nano-spherical α-alumina as a support effectively improves the dispersibility of rhodium, reduces agglomeration, and extends its service life. The rhodium-based photothermal catalyst described in this invention exhibits excellent resistance to carbon deposition and high-temperature stability during the reaction process, maintaining stable catalytic activity and adapting to multiple cycles without significant deactivation. Attached Figure Description

[0022] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an improper limitation of the invention.

[0023] Figure 1 These are high-magnification transmission electron microscopy images of the rhodium-based photothermal catalyst 0.5wt% Rh / α-Al2O3 prepared in the embodiments of the present invention at different magnifications. Figure 1 a and Figure 1 b) and element mapping diagram ( Figure 1 c).

[0024] Figure 2 The X-ray diffraction pattern of the rhodium-based photothermal catalyst 0.5wt%Rh / α-Al2O3 prepared in the embodiments of the present invention is shown.

[0025] Figure 3 The results of the thermal catalytic CO2 methanation performance evaluation of the rhodium-based photothermal catalyst 0.5wt% Rh / α-Al2O3 prepared in the embodiments of the present invention under different temperature conditions include the methane formation rate and selectivity.

[0026] Figure 4The results of the photothermal catalytic CO2 methanation performance evaluation of the rhodium-based photothermal catalyst 0.5wt% Rh / α-Al2O3 prepared in the embodiments of the present invention under different temperature conditions include the methane formation rate and selectivity.

[0027] Figure 5 This study tests the stability of the rhodium-based photothermal catalyst 0.5wt% Rh / α-Al2O3 prepared in the embodiments of the present invention in the photothermal catalytic CO2 methanation reaction.

[0028] Figure 6 The results of the photothermal catalytic CO2 methanation performance evaluation of the rhodium-based photothermal catalysts with different loadings prepared in the embodiments of the present invention at 350°C include the methane generation rate and selectivity. Detailed Implementation

[0029] It should be noted that the following detailed descriptions are exemplary and intended to provide further illustration of the invention. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0030] A typical embodiment of the present invention provides a rhodium-based catalyst supported on nanospherical α-alumina, comprising a nanospherical α-alumina support and rhodium nanoparticles supported on the support.

[0031] Nanosphere-shaped α-alumina exhibits excellent thermal stability and good surface structure control. Furthermore, research has shown that nanosphere-shaped α-alumina, as a carrier for rhodium nanoparticles, a photothermal catalytic active material, can not only achieve efficient dispersion and stable loading of rhodium nanoparticles, but also that the catalyst formed by it has excellent photothermal catalytic CO2 methanation activity.

[0032] In some embodiments, the particle size of the nanospherical α-alumina carrier is 50-200 nm, preferably 50-100 nm.

[0033] In some embodiments, the rhodium nanoparticles have a particle size of 0.5-8 nm, preferably 0.5-5 nm. The particle size of the rhodium nanoparticles can be characterized and determined by transmission electron microscopy (TEM).

[0034] In some embodiments, the mass of the rhodium nanoparticles is 0.2 to 5% of the mass of the nanospherical α-alumina carrier, preferably 0.5 to 4%.

[0035] Another embodiment of the present invention provides a method for preparing the above-mentioned rhodium-based catalyst supported on nanosphere α-alumina. The method involves mixing an aqueous solution of a rhodium-based precursor with nanosphere α-alumina, removing water to obtain a powder, and then using hydrogen to carry out a reduction reaction to reduce the rhodium in the powder, thereby obtaining the catalyst.

[0036] Specifically, an aqueous solution of a rhodium-based precursor is mixed with nanospheres of α-alumina, stirred thoroughly, and then allowed to stand to ensure that the rhodium-based precursor is fully adsorbed onto the surface of the nanospheres of α-alumina. Moisture is removed by evaporation to obtain a uniform, dry powder. The dried powder is then reduced in a hydrogen atmosphere to ensure that the rhodium-based precursor is completely reduced to metallic rhodium nanoparticles and uniformly dispersed on the surface of the nanospheres of α-alumina, thus obtaining the target product. This invention removes moisture through evaporation, which not only improves the loading efficiency of the nanospheres of α-alumina for the rhodium-based precursor, avoiding waste of the precursor, but also improves the uniformity of the dispersion of the rhodium-based precursor on the nanospheres of α-alumina.

[0037] In some embodiments, the concentration of the aqueous solution of the rhodium-based precursor is 0.01-0.15 mol / L.

[0038] In some embodiments, the mass of rhodium in the rhodium-based precursor is 0.2 to 5% of the mass of the nanosphere α-alumina carrier, preferably 0.5 to 4%.

[0039] In some embodiments, the drying temperature after water removal is 80-120°C, preferably 110°C. Specifically, the drying time is 12 hours.

[0040] In some embodiments, the reduction temperature is 500-800℃, preferably 600℃. Under these conditions, the reduced rhodium is guaranteed to be elemental rhodium, while the reduction of alumina is avoided.

[0041] In some embodiments, the reduction time is 2-6 hours, preferably 3 hours.

[0042] A third embodiment of the present invention provides an application of the above-mentioned rhodium-based catalyst supported on nanosphere α-alumina in photothermal catalysis.

[0043] Specifically, the photothermal catalysis is the photothermal catalytic CO2 methanation. Rhodium-based photothermal catalysts can significantly improve the efficiency and methane selectivity of the CO2 methanation reaction through photothermal synergy, providing an efficient solution for carbon resource utilization.

[0044] A fourth embodiment of the present invention provides a method for photothermal catalytic CO2 methanation, comprising the following steps:

[0045] The above-mentioned rhodium-based catalyst was placed in a fixed-bed photothermal reactor, activated in a high-temperature hydrogen atmosphere and cooled to the reaction temperature. CO2 and H2 were introduced as reaction gases, and photothermal catalytic CO2 methanation was carried out under light irradiation.

[0046] The catalyst activity is calculated based on the methane formation rate.

[0047] Before the catalytic reaction, the rhodium-based photothermal catalyst needs to be activated in a high-temperature hydrogen atmosphere to remove the metal oxides on the surface.

[0048] In some embodiments, the activation temperature is 350-600°C, preferably 400°C. Specifically, the heating rate is 10°C / min.

[0049] In some embodiments, the activation time is 0.5-1.5 h, preferably 1 h.

[0050] In some embodiments, the hydrogen flow rate during activation is 35-45 ml / min, preferably 40 ml / min.

[0051] In some embodiments, the reaction temperature is 150-350°C.

[0052] In some embodiments, the ratio of the CO2 and H2 reacting gases is 1:1-4, preferably 1:4.

[0053] In some embodiments, the mass ratio of the rhodium-based catalyst to the total flow rate of the reactant gas is 10-30 mg: 45-55 ml / min, preferably 10-30 mg: 50 ml / min, more preferably 20 mg: 45-55 ml / min, and even more preferably 20 mg: 50 ml / min.

[0054] In some embodiments, the illumination conditions are 1.0-5.0 W / cm². -2 It is equipped with a 300W xenon lamp and a ZF2 plano-convex lens.

[0055] To enable those skilled in the art to better understand the technical solution of the present invention, the technical solution of the present invention will be described in detail below with reference to specific embodiments.

[0056] Example 1

[0057] A method for preparing a rhodium-based photothermal catalyst (0.5 wt% Rh / α-Al2O3) supported on nanospheres of α-alumina includes the following steps:

[0058] Weigh 500 mg of nano-spherical α-alumina powder and add it to 2.5 ml of deionized water. Measure 2.453 ml of a 0.01 mol / L rhodium chloride aqueous solution. -1Add the above suspension, stir thoroughly, and allow to stand to allow the rhodium-based precursor to fully adsorb onto the support surface. Place the suspension in a sand bath at 110℃ and stir for 12 hours until completely dry. Reduce the dried powder under a hydrogen atmosphere at a flow rate of 40 ml / min, a reduction temperature of 600℃, and a reduction time of 3 hours. After reduction, allow it to cool naturally to room temperature. The resulting catalyst is named 0.5 wt% Rh / α-Al₂O₃.

[0059] Example 2

[0060] A method for preparing a rhodium-based photothermal catalyst (2wt% Rh / α-Al2O3) supported on nanospheres of α-alumina includes the following steps:

[0061] Weigh 500 mg of nano-spherical α-alumina powder and add it to 4 ml of deionized water. Measure 1 ml of 0.1 mol / L rhodium chloride aqueous solution. -1 Add the above suspension, stir thoroughly, and allow to stand to allow the rhodium-based precursor to fully adsorb onto the support surface. Place the suspension in a sand bath at 110℃ and stir for 12 hours until completely dry. Reduce the dried powder under a hydrogen atmosphere at a flow rate of 40 ml / min, a reduction temperature of 600℃, and a reduction time of 3 hours. After reduction, allow to cool naturally to room temperature. The resulting catalyst is named 2wt%Rh / α-Al2O3.

[0062] Example 3

[0063] A method for preparing a rhodium-based photothermal catalyst (4 wt% Rh / α-Al₂O₃) supported on nanospheres of α-alumina includes the following steps:

[0064] Weigh 500 mg of nano-spherical α-alumina powder and add it to 2.9 ml of deionized water. Measure 2.1 ml of a 0.1 mol / L rhodium chloride aqueous solution. -1 Add the above suspension, stir thoroughly, and allow to stand to allow the rhodium-based precursor to fully adsorb onto the support surface. Place the suspension in a sand bath at 110℃ and stir for 12 hours until completely dry. Reduce the dried powder under a hydrogen atmosphere at a flow rate of 40 ml / min, a reduction temperature of 600℃, and a reduction time of 3 hours. After reduction, allow to cool naturally to room temperature. The resulting catalyst is named 4wt%Rh / α-Al2O3.

[0065] Product analysis and performance testing:

[0066] Morphology and phase analysis of rhodium-based photothermal catalysts:

[0067] The TEM image of the rhodium-based photothermal catalyst 0.5 wt% Rh / α-Al₂O₃ prepared in Example 1 is shown below. Figure 1As shown in Figure a, the nanospheres of α-alumina have a particle size of 50-100 nm, and the nanoparticles (with a particle size of 0.5-5 nm) are uniformly distributed on the catalyst support. Figure 1 A further magnified image in b shows that the lattice spacing of the nanoparticles is 0.218 nm, which corresponds to the (111) crystal plane of rhodium. This indicates that the rhodium nanoparticles were successfully loaded onto the surface of the nanospheres of α-alumina and retained their typical metallic properties. Figure 1 The elemental distribution diagram of c further confirms the high dispersion of Rh nanoparticles, indicating that the preparation method effectively avoids particle agglomeration. Overall, the Rh nanoparticles in the 0.5wt% Rh / α-Al2O3 rhodium-based photothermal catalyst exhibit clear lattice characteristics and uniform particle distribution, providing an ideal structural basis for subsequent improvement of photothermal catalytic performance.

[0068] XRD patterns as follows Figure 2 As shown, all samples exhibited typical diffraction peaks at 35.16°, 37.8°, 43.39°, 52.57°, 57.51°, 66.53°, and 68.19°, corresponding to the (104), (110), (113), (024), (116), (214), and (300) crystal planes of the nanospherical α-Al2O3 support, respectively. However, the Rh diffraction peak intensities were not significant in the rhodium-based photothermal catalyst samples with different loadings, which can be explained by the low Rh loading and high dispersion. Furthermore, as the Rh metal loading increased, the diffraction peak intensities attributable to the α-Al2O3 support gradually decreased. This phenomenon suggests that with the increase of loading, Rh nanoparticles gradually cover the surface of the α-Al2O3 support, which may partially obscure the diffraction signal of the support, leading to a weakening of the diffraction peak intensities of the support crystal plane features. Furthermore, this may also reflect the enhanced interaction between the support surface and Rh, which further alters the surface properties and electronic structure of the crystal, providing important supporting evidence for the subsequent improvement of catalytic performance.

[0069] Performance evaluation of photothermal catalytic CO2 methanation:

[0070] (1) Experimental Methods: 20 mg of the photothermal catalyst (0.5 wt% Rh / α-Al2O3, 2 wt% Rh / α-Al2O3) prepared in the examples was weighed and placed in a fixed-bed photothermal reactor, uniformly dispersed and covered on quartz wool. Before the catalytic reaction, the photothermal catalyst was activated in a hydrogen atmosphere for 1 h to remove surface metal oxides. The hydrogen flow rate was 40 ml / min, and the activation temperature was 400 °C. After activation, the catalyst was naturally cooled to the catalytic reaction temperature (150 °C, 250 °C, 350 °C), and then the reaction gas was introduced for 30 min. The total flow rate of the reaction gas was 50 ml / min, and the CO2 / H2 ratio was 1:4. During the photothermal catalysis, a 300 W xenon lamp equipped with a ZF2 plano-convex lens was used as the light source to irradiate the top of the reactor with the full spectrum. For the thermal catalysis process, no light was added, and other conditions were the same as those for the photothermal catalysis. During the catalytic reaction, 0.2 ml of gas was taken at regular intervals (25 min, 50 min, and 75 min) and analyzed by gas chromatography to determine the composition of the generated gas. Four cycles were conducted at 350℃ to verify the cyclic stability of the photothermal catalyst. After each test, the gas was purged with the reaction gas for 1 hour before the next cycle began.

[0071] (2) Experimental Results: The comparison results of the thermocatalytic CO2 methanation and photothermal CO2 methanation activities of the 0.5wt% Rh / α-Al2O3 prepared in Example 1 under different temperature conditions are as follows: Figure 3 and Figure 4 As shown. From Figure 3 It can be seen that under thermocatalytic conditions at 150℃, the catalyst exhibits almost no catalytic activity. As the thermocatalytic reaction temperature increases, the catalytic activity gradually improves, especially at 350℃, where the catalytic activity is significantly enhanced. This indicates that the CO2 methanation reaction is limited by a high reaction energy barrier, while high-temperature conditions facilitate the full activation of reactant molecules and accelerate surface reaction kinetics. Furthermore... Figure 4 The photothermal catalytic activity shown was superior to that under pure thermal catalysis conditions at all test temperatures, demonstrating the significant effect of light irradiation. At 150 °C, the reaction rate under photothermal catalysis conditions reached 3.205 mmol·g⁻¹. -1 ·h -1 This indicates that even at low temperatures, the introduction of light can significantly enhance the activity of the catalyst. Furthermore, at 250℃, the photothermal catalytic performance was 57 times higher than that under dark conditions, further validating the crucial role of light in the reaction process. This significant performance improvement is mainly attributed to the hot electrons and photothermal effects generated by rhodium nanoparticles under SPR excitation, which significantly promotes the adsorption and activation of CO2 molecules, lowers the activation energy of the reaction, and thus improves the efficiency of the photothermal catalytic CO2 methanation reaction. Figure 5The effects of different catalyst loadings on photothermal CO2 methanation were compared. The results showed that the increase in metal loading was positively correlated with catalytic activity, but the selectivity decreased, which may be related to particle size. Figure 6 The 0.5wt% Rh / α-Al2O3 photothermal catalyst was shown to have good photothermal catalytic cycle stability, with methane selectivity maintained at around 98.7%.

[0072] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. Application of rhodium-based catalysts supported on nanosphere α-alumina in photothermal catalytic CO2 methanation under full-spectrum irradiation; The method for preparing the rhodium-based catalyst supported on nano-spherical α-alumina involves uniformly mixing an aqueous solution of the rhodium-based precursor with nano-spherical α-alumina, removing the water to obtain a powder, and then carrying out a reduction reaction with hydrogen at a temperature of 500-800℃ for 2-6 hours to reduce the rhodium in the powder, thus obtaining the catalyst.

2. The application as described in claim 1, characterized in that, The concentration of the aqueous solution of the rhodium-based precursor is 0.01-0.15 mol / L; Alternatively, the mass of rhodium in the rhodium-based precursor is 0.2-5% of the mass of the nanosphere α-alumina carrier.

3. The application as described in claim 1, characterized in that, The mass of rhodium in the rhodium-based precursor is 0.5 to 4% of the mass of the nanosphere α-alumina carrier.

4. The application as described in claim 1, characterized in that, Moisture is removed by evaporation; the drying temperature after water removal is 80-120℃.

5. The application as described in claim 1, characterized in that, The photothermal catalysis is photothermal CO2 methanation.

6. A method for photothermal catalytic CO2 methanation, characterized in that, Includes the following steps: A rhodium-based catalyst was placed in a fixed-bed photothermal reactor, activated in a high-temperature hydrogen atmosphere and cooled to the reaction temperature. CO2 and H2 were introduced as reaction gases, and photothermal catalytic CO2 methanation was carried out under light irradiation. The illumination conditions are full-spectrum irradiation; The method for preparing the rhodium-based catalyst involves uniformly mixing an aqueous solution of a rhodium-based precursor with nano-spherical α-alumina, removing the water to obtain a powder, and then using hydrogen to carry out a reduction reaction at a reduction temperature of 500-800℃ for 2-6 hours, thereby reducing the rhodium in the powder to obtain the catalyst.

7. The method of claim 6, characterized in that, The activation temperature is 350-600℃; Alternatively, the activation time is 0.5-1.5 hours; Alternatively, the hydrogen flow rate during activation is 35-45 mL / min; Alternatively, the reaction temperature is 150-350℃; Alternatively, the ratio of the CO2 and H2 reacting gases is 1:1-4; Alternatively, the mass ratio of the rhodium-based catalyst to the total flow rate of the reactant gas is 10-30 mg: 45-55 mL / min; Alternatively, the illumination conditions are 1.0-5.0 W / cm². -2 .

8. The method of claim 7, characterized in that, The activation temperature is 400℃.

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