Catalyst for photocatalytic oxidation of plant emissions of isoprene under visible light and use thereof

Abstract

The application discloses a catalyst for photocatalytic oxidation of plant emission isoprene under visible light and application thereof, and the catalyst comprises the following compounds or combinations thereof: nanometer titanium dioxide, copper oxide cluster modified mixed crystal type nanometer titanium dioxide and bismuth vanadate modified titanium dioxide heterojunction nanocomposite. The catalyst can photocatalytically degrade plant emission isoprene in an atmospheric environment under visible light and certain humidity, and oxidatively degrade the isoprene into carbon dioxide, so that the contribution of the plant emission isoprene to the generation of pollutants such as ozone and secondary organic aerosol in the atmosphere is reduced. For example, the prepared photocatalyst powder can be coated on the surface of a medium, and the photocatalyst on the surface of the medium can photocatalytically degrade plant emission isoprene through irradiation of sunlight.

Description

Technical Field

[0001] This invention relates to the field of photocatalysis technology, specifically to catalysts for the photocatalytic oxidation of isoprene emitted by plants under visible light and their applications. Background Technology

[0002] Isoprene is an important chemical signaling substance in plants, playing a crucial role in regulating plant temperature and growth, as well as preventing pests and diseases. Plants release isoprene into the atmosphere during normal growth and after injury. Trees such as oak, poplar, mulberry, and locust trees have particularly high release rates. It has been reported that global plant emissions of isoprene amount to 600 Tg annually, accounting for approximately 40% of global non-methane volatile organic compound (NMO) emissions. Isoprene released into the atmosphere is highly reactive with OH radicals, and under NOx conditions, it undergoes photochemical reactions to generate secondary pollutants such as ozone and secondary organic aerosols. Studies have shown that plant-emitted isoprene significantly contributes to ozone pollution in many urban areas of my country during summer and autumn. However, reducing the impact of plant-emitted isoprene on urban air quality remains a challenging problem in the field of air pollution control.

[0003] Previous studies have shown that mineral dust in atmospheric particulate matter exhibits heterogeneous photo-oxidation activity for isoprene and may be a significant sink for isoprene in the atmosphere. Currently, there are few reports on technologies for controlling isoprene emissions from plants in the atmosphere. A published invention patent (CN 116078367 A) discloses a class of catalysts for the photocatalytic oxidation of isoprene, including nano-titanium dioxide (P25 type titanium dioxide), carbon quantum dot-modified titanium dioxide, and cerium dioxide. However, the water loss resistance of these catalysts during visible light photocatalytic degradation of isoprene under atmospheric conditions requires further improvement. This invention develops a class of photocatalysts with excellent visible light activity, carbon dioxide selectivity, and good water loss resistance for isoprene, which can be used for the removal of isoprene emitted from plants in the atmospheric environment. Summary of the Invention

[0004] To address the aforementioned technical problems in the prior art, this invention provides a catalyst for the photocatalytic oxidation of isoprene emitted by plants and its application. The catalyst photocatalytically oxidizes and degrades isoprene emitted by the atmosphere and plants into carbon dioxide, thereby reducing the generation of secondary pollutants such as ozone by isoprene in the atmosphere through photochemical reactions.

[0005] This invention discloses a catalyst for the photocatalytic oxidation of isoprene emitted by plants. The catalyst is used for the photocatalytic degradation of isoprene emitted by plants. The catalyst comprises any of the following compounds or combinations thereof: nano-titanium dioxide, mixed-crystal nano-titanium dioxide modified with copper oxide clusters, and titanium dioxide heterojunction nanocomposite material modified with bismuth vanadate.

[0006] Preferably, the nano-titanium dioxide includes mixed-crystal nano-titanium dioxide prepared by the sol-gel method;

[0007] The sol-gel method includes:

[0008] Isopropyl titanate was dissolved in isopropanol to obtain the first mixture;

[0009] Isopropanol and water were mixed evenly at a volume ratio of 1:2 and then added dropwise to the first mixture while stirring continuously to obtain a sol.

[0010] After drying the sol obtained above, it was calcined at different temperatures to obtain mixed-crystal nano-titanium dioxide powder prepared by the sol-gel method.

[0011] Specifically, the methods for preparing mixed-crystalline nano-titanium dioxide using the sol-gel method include:

[0012] Dissolve 5 ml of isopropyl titanate in 10 ml of isopropanol and stir continuously for 30 min to mix it evenly, thus obtaining the first mixture.

[0013] Add 30 ml of isopropanol aqueous solution (isopropanol: water = 1:2) dropwise to the first mixture. The addition process is carried out at room temperature with continuous stirring to obtain a white sol.

[0014] After the white sol was aged at room temperature for 1-3 hours, it was placed in a forced-air drying oven and dried overnight at 100°C. Then, the titanium dioxide precursor was placed in a muffle furnace and heated at a heating rate of 5-20°C / min, and kept at 500-800°C for 2 hours to obtain mixed-crystal nano-titanium dioxide powder prepared by the sol-gel method.

[0015] Preferably, the method for preparing the copper oxide cluster-modified mixed-crystal nano-titanium dioxide includes:

[0016] Copper sulfate pentahydrate is dissolved in water to form a second mixture;

[0017] The mixed-crystal nano-titanium dioxide powder was dispersed in the second mixture and stirred vigorously at 80-100℃ for 1 hour to obtain the third mixed suspension.

[0018] After centrifugation, washing and drying of the third mixture, mixed-crystal nano-titanium dioxide modified with copper oxide clusters is obtained.

[0019] Specifically, the preparation methods of copper oxide cluster-modified mixed-crystal nano-titanium dioxide include:

[0020] Add 15.6 mg of copper sulfate pentahydrate to 15 ml of deionized water and sonicate for 2-10 min to dissolve it, thus obtaining the second mixture.

[0021] 250 mg of mixed-crystal nano-titanium dioxide powder was added to the second mixture, ultrasonicated at room temperature for 20 min, and then heated and stirred at 80-100℃ for 1 h to obtain the third mixture.

[0022] The third mixture was centrifuged, the supernatant was poured off, and then washed with deionized water and centrifuged several times. The resulting precipitate was then dried at 80-100℃ and ground into powder to obtain copper oxide cluster-modified mixed-crystal nano-titanium dioxide.

[0023] Preferably, the preparation method of the bismuth vanadate-modified titanium dioxide heterostructure nanocomposite material includes:

[0024] Bismuth nitrate pentahydrate was dissolved in concentrated nitric acid, then citric acid monohydrate was added, and the mixture was stirred until homogeneous. The pH of the solution was then adjusted to 7.5 with ammonia to obtain the fourth mixture.

[0025] Ammonium metavanadate was dissolved in hot water to obtain the fifth mixture;

[0026] The fifth mixture was added dropwise to the fourth mixture under continuous vigorous stirring to obtain the sixth mixture;

[0027] The sixth mixture was placed in a forced-air drying oven and heat-treated at 80°C overnight to obtain the bismuth vanadate precursor.

[0028] The bismuth vanadate precursor was calcined in a muffle furnace at 400-600℃ to obtain bismuth vanadate powder.

[0029] Bismuth vanadate powder and hexadecyltrimethylammonium bromide were dispersed in isopropanol to obtain the seventh mixture;

[0030] The seventh mixture is added dropwise to the first mixture while continuously stirring to ensure uniform mixing, thus obtaining the eighth mixture.

[0031] Isopropanol and water were mixed evenly at a volume ratio of 1:2 and then added dropwise to the eighth mixture. With continuous stirring, a sol was gradually formed.

[0032] The sol was heated and dried, then calcined in a muffle furnace to obtain a bismuth vanadate-modified titanium dioxide heterostructure nanocomposite material.

[0033] Specifically, the preparation methods of bismuth vanadate-modified titanium dioxide heterostructure nanocomposites include:

[0034] Dissolve 2.425g of bismuth nitrate pentahydrate in 30ml of concentrated nitric acid with a mass fraction of 32.5%, then add 2.1g of citric acid monohydrate, stir vigorously for 30min, and then adjust the pH of the solution to 7.5 with ammonia water to obtain the fourth mixture.

[0035] Dissolve 0.58g of ammonium metavanadate in 60ml of hot water at 70℃ to obtain the fifth mixture;

[0036] The fifth mixture was added dropwise to the fourth mixture under continuous vigorous stirring, and the mixture was stirred continuously for 60 minutes to obtain the sixth mixture.

[0037] The sixth mixture was placed in a forced-air drying oven and heat-treated at 80°C overnight to obtain the bismuth vanadate precursor.

[0038] The bismuth vanadate precursor was placed in a muffle furnace and heated to 500°C at 3°C / min. After calcination for 4 hours, it was naturally cooled to obtain bismuth vanadate powder.

[0039] 135 mg of bismuth vanadate powder was dispersed in 5 ml of isopropanol and sonicated for 10 min. Then, 13.5 mg of cetyltrimethylammonium bromide was added and sonicated for another 20 min to obtain the seventh mixture.

[0040] The seventh mixture is added dropwise to the first mixture while continuously stirring to ensure uniform mixing, thus obtaining the eighth mixture.

[0041] Add 30 ml of isopropanol aqueous solution (isopropanol: water = 1:2) dropwise to the eighth mixture, and gradually form a sol with constant stirring;

[0042] After the sol was allowed to stand at room temperature for 1-3 hours, it was placed in a forced-air drying oven and dried overnight at 100°C. Then, the bismuth vanadate-modified titanium dioxide precursor was placed in a muffle furnace and heated to 500°C at 10°C / min. After calcination at 500°C for 2 hours, bismuth vanadate-modified titanium dioxide heterostructure nanocomposite material was obtained.

[0043] This invention also provides a method for the photocatalytic degradation of isoprene emitted by plants, the method comprising the following steps:

[0044] The catalyst powder was dispersed in 5.5 ml of deionized water to obtain the ninth mixture;

[0045] The ninth mixture is sprayed, coated, smeared, or poured onto the surface of the medium.

[0046] By air drying or heating, a thin coating of catalyst is formed on the surface of the medium, and isoprene is photocatalytically oxidized and degraded through the catalyst coating on the surface of the medium.

[0047] Preferably, the medium includes: a stainless steel metal disc, plant leaves, tree trunks, building surfaces, or soil;

[0048] The wavelength range of the light source in the photocatalysis experiment was 400-760nm; the relative humidity of the photocatalysis experiment was 20%, and the temperature was room temperature.

[0049] Preferably, the thickness of the catalyst coating on the medium surface is 32.5-65 μm.

[0050] Compared with the prior art, the beneficial effects of the present invention are as follows: the catalyst photocatalytically degrades isoprene emitted by the atmospheric environment and plants, oxidizing it into carbon dioxide, thereby reducing the contribution of isoprene to the generation of pollutants such as ozone in the atmospheric environment. Attached Figure Description

[0051] Figure 1 This is a graph showing the photocatalytic degradation activity and selectivity of copper oxide cluster-modified mixed-crystal nano-titanium dioxide on isoprene under different humidity conditions.

[0052] Figure 2 This is a graph showing the photocatalytic degradation activity and selectivity of copper oxide cluster-modified mixed-crystal nano-titanium dioxide on isoprene at different residence times;

[0053] Figure 3 This is an experimental analysis diagram of the deactivation resistance of mixed-crystal nano-titanium dioxide modified with copper oxide clusters;

[0054] Figure 4 This is an experimental analysis diagram of the water resistance of mixed-crystal nano-titanium dioxide modified with copper oxide clusters;

[0055] Figure 5 This is a flowchart of the photocatalytic degradation method for isoprene. Specific implementation methods

[0056] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, 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, 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.

[0057] The present invention will now be described in further detail with reference to the accompanying drawings:

[0058] A catalyst for the photocatalytic oxidation of isoprene emitted by plants, the catalyst being used for the photocatalytic degradation of isoprene emitted by plants, the catalyst comprising any one of the following compounds or a combination thereof: nano-titanium dioxide, mixed-crystal nano-titanium dioxide modified with copper oxide clusters, and titanium dioxide heterostructure nanocomposite material modified with bismuth vanadate.

[0059] The catalyst photocatalytically degrades isoprene emitted from the atmosphere and plants into carbon dioxide, thereby reducing the formation of pollutants such as ozone from isoprene in the atmosphere. For example, the catalyst can be dispersed on the surface of a medium, allowing for the photocatalytic degradation of isoprene emitted from plants in the atmosphere. The medium may include: a stainless steel metal disc, plant leaves, tree trunks, building surfaces, or soil.

[0060] The nano-titanium dioxide includes mixed-crystal nano-titanium dioxide prepared by the sol-gel method.

[0061] like Figure 5 As shown, the methods for photocatalytic oxidation and degradation of isoprene using catalysts include:

[0062] Step S1: Weigh an appropriate amount of photocatalyst powder and disperse it in a certain volume of deionized water. To ensure that the powder particles can be well dispersed in water and thus exert good catalytic performance, it needs to be subjected to ultrasonic vibration treatment to obtain a stable and homogeneous ninth mixture.

[0063] Step S2: Spray or pour the ninth mixture onto the surface of the medium.

[0064] Step S3: Then, the photocatalyst powder is allowed to form a thin coating on the surface of the medium by natural air drying or heating, thereby enabling photocatalytic degradation of isoprene.

[0065] Example 1

[0066] Mixed-crystalline nano-titanium dioxide prepared by the sol-gel method was used as a catalyst. The preparation method used isopropyl titanate as the titanium source and employed a heat-assisted sol-gel method: 5 ml of isopropyl titanate was dissolved in 10 ml of isopropanol and stirred continuously for 30 min to obtain a first mixture; 30 ml of isopropanol aqueous solution (isopropanol:water = 1:2) was added dropwise to the first mixture at room temperature with continuous stirring to obtain a white sol; the white sol was allowed to stand at room temperature for 1-3 hours, then dried overnight at 100℃ in a forced-air drying oven; the obtained titanium dioxide precursor was then placed in a muffle furnace and heated at a rate of 5-20℃ / min, holding at 500-800℃ for 2 h to obtain mixed-crystalline nano-titanium dioxide powder prepared by the sol-gel method.

[0067] This mixed-crystal nano-titanium dioxide contains three different crystal phases: anatase, rutile, and a small amount of brookite. During preparation, the mixed-crystal structure can be formed by controlling the calcination temperature and heating rate. The presence of the rutile phase makes the titanium dioxide more easily excited by visible light, and at the same time, the separation efficiency of photogenerated electrons and holes inside it is improved, thus exhibiting excellent visible light photocatalytic ability.

[0068] Example 2

[0069] Photocatalytic degradation of isoprene was conducted in a laboratory-specific continuous flow reactor using copper oxide cluster-modified mixed-crystalline nano-titanium dioxide as a catalyst. The degradation effect on isoprene under different humidity levels and residence times was investigated, along with its resistance to deactivation and water resistance. Isoprene gas at 657.4 ppb was introduced into the continuous flow reactor, and the concentration changes of isoprene and generated carbon dioxide over 40 minutes were detected using proton transfer reaction-time-of-flight mass spectrometry and a greenhouse gas analyzer, respectively. A quartz glass window was installed at the top of the reactor, and xenon lamp light (visible light band 400-760 nm) was used for vertical irradiation to ensure sufficient light exposure for the catalyst.

[0070] 20 mg of copper oxide cluster-modified mixed-crystalline nano-titanium dioxide powder was ultrasonically dispersed in 5.5 ml of deionized water and poured onto a stainless steel disc (d = 5.5 cm). The disc was then placed in a drying oven at 80 °C to dry, forming a thin catalyst coating and obtaining the reaction medium. This reaction medium simulates the application of a catalyst to the surface of a medium such as plant leaves.

[0071] Condition 1: Effect of humidity on the photocatalytic degradation of isoprene

[0072] The activity and selectivity of copper oxide cluster-modified mixed-crystalline nano-titanium dioxide for the photocatalytic degradation of isoprene under different humidity conditions were tested. Specifically, by setting up a humidification device, i.e., controlling the reaction humidity by adjusting the proportion of water entering through bubbling, the activity and selectivity of isoprene at relative humidity of 0%, 20%, 40%, 60%, and 80% were tested under the conditions of a residence time of 1.36 s and a light source wavelength of 400-760 nm. Figure 1 As shown, although the activity is best at a relative humidity of RH=0, there will be no humid climate in the actual environment, and its selectivity is lower than that at RH=20%. In general, the higher the humidity, the more obvious the hindering effect on the performance of the catalyst. Usually, the best activity and selectivity are exhibited at a relative humidity of RH=20%.

[0073] Condition 2: Effect of residence time on photocatalytic degradation of isoprene

[0074] The activity and selectivity of copper oxide cluster-modified mixed-crystalline nano-titanium dioxide for the photocatalytic degradation of isoprene under different residence times (also known as different space velocities) were tested. Specifically, while keeping the isoprene concentration constant (657.4 ppb), the residence time was controlled by varying the velocity of the airflow passing over the catalyst surface in the reactor. The activity and selectivity of isoprene at residence times of 1.36 s, 2.46 s, 4.92 s, and 9.84 s were tested under conditions of RH = 20% and a light source wavelength of 400-760 nm. Figure 2 As shown, with the increase of the residence time of the reaction gas stream, the catalyst's activity for isoprene degradation gradually increases, but this is accompanied by a gradual decrease in selectivity. Overall, considering both the catalyst's activity and selectivity for isoprene catalysis and the actual gas space velocity in the environment, it can be considered that the catalyst has greater practical application value and advantages under the condition of a residence time of 1.36 s.

[0075] Condition 3: Effect of cycle number on photocatalytic degradation of isoprene

[0076] The activity and selectivity of copper oxide cluster-modified mixed-crystalline nano-titanium dioxide for the photocatalytic degradation of isoprene were tested after four photocatalytic degradation cycles. Specifically, after each photocatalytic reaction, no catalyst treatment was performed, and isoprene was photocatalytically degraded again under the same conditions. This process was repeated for four cycles. The test conditions were: residence time 1.36 s, RH = 20%, reaction time 2 h, and all other conditions remained consistent with condition 1. Figure 3 As shown, the activity decreased significantly during the second cycle. The characteristic feature is that the activity, starting from the end of the first cycle, continued to decrease slowly. By the third and fourth cycles, the activity remained at approximately 27% and did not decrease further. Regarding selectivity, the selectivity gradually increased with the number of cycles. Overall, the catalyst did not deactivate due to the gradual accumulation of reaction intermediates and maintained a relatively efficient oxidative degradation capacity for isoprene and intermediates accumulated on the catalyst surface. Therefore, the catalyst can be considered to have good resistance to deactivation.

[0077] Condition 4: Effect of humidity change on photocatalytic degradation of isoprene

[0078] The activity and selectivity of copper oxide cluster-modified mixed-crystalline nano-titanium dioxide for the photocatalytic degradation of isoprene were tested after four humidity changes. Specifically, after the photocatalytic reaction at each humidity level, no catalyst treatment was performed, and then the humidity was changed again to conduct photocatalytic degradation of isoprene. This process was repeated four times, with the following test conditions: residence time 1.36 s, relative humidity change sequence 20% → 80% → 60% → 40% → 20%, reaction time 2 h, and all other conditions remaining the same as in condition 1. Figure 4 As shown, when the relative humidity changes from 20% to 80%, the activity decreases from 31% to about 18%. However, when the relative humidity continues to decrease from 80% to 20%, the activity gradually recovers to about 27%. In terms of selectivity, the selectivity still shows a gradual upward trend with the successive changes in humidity. This is related to the degradation of intermediate products accumulated on the catalyst surface. Overall, in the experiment simulating the effect of humidity changes on catalyst activity in a real environment, the catalyst showed good water resistance. That is, the activity of the catalyst is inhibited under high humidity, but the activity of the catalyst gradually recovers when the humidity drops to low humidity.

[0079] The photocatalytic degradation of isoprene by copper oxide cluster-modified mixed-crystal nano-titanium dioxide under simulated different environmental conditions was achieved, and good degradation effect was obtained. It can overcome the influence of environmental factors and has good applicability.

[0080] Example 3

[0081] Preparation of modified titanium dioxide. The preparation method of bismuth vanadate-modified titanium dioxide heterostructure nanocomposites includes:

[0082] 2.425 g of bismuth nitrate pentahydrate was dissolved in 30 ml of 32.5% concentrated nitric acid, then 2.1 g of citric acid monohydrate was added. After vigorous stirring for 30 min, the pH of the solution was adjusted to 7.5 with ammonia water to obtain the fourth mixture. 0.58 g of ammonium metavanadate was dissolved in 60 ml of 70°C hot water to obtain the fifth mixture. The fifth mixture was added dropwise to the fourth mixture under continuous vigorous stirring for 60 min to obtain the sixth mixture. The sixth mixture was placed in a forced-air drying oven and heat-treated at 80°C overnight to obtain the bismuth vanadate precursor. The bismuth vanadate precursor was placed in a muffle furnace and heated to 500°C at 3°C / min, calcined for 4 h, and then naturally cooled to obtain bismuth vanadate powder. 135 mg of bismuth vanadate powder was dispersed in… In 5 ml of isopropanol, the mixture was sonicated for 10 min, and then 13.5 mg of hexadecyltrimethylammonium bromide was added. After sonication for another 20 min, a seventh mixture was obtained. The seventh mixture was added dropwise to the first mixture while stirring continuously to ensure uniform mixing, resulting in an eighth mixture. 30 ml of isopropanol aqueous solution (isopropanol:water = 1:2) was added dropwise to the eighth mixture while stirring continuously to gradually form a sol. The sol was allowed to stand at room temperature for 1-3 hours, then dried overnight at 100°C in a forced-air drying oven. The bismuth vanadate-modified titanium dioxide precursor was then placed in a muffle furnace and heated to 500°C at a rate of 10°C / min. After calcination at 500°C for 2 hours, a bismuth vanadate-modified titanium dioxide heterostructure nanocomposite material was obtained.

[0083] Specifically, titanium dioxide modified with 10 wt% bismuth vanadate was prepared.

[0084] In addition to the catalysts mentioned above, P25 titanium dioxide was used as a reference. Specifically, 20 mg of the above catalyst powder and P25 titanium dioxide powder were used to prepare catalyst discs, and photocatalytic degradation experiments of isoprene were conducted. The test results are shown in Table 1. During the photocatalytic process, the reaction was controlled under the following conditions: initial isoprene concentration of 657.4 ppb, residence time of 1.36 s, relative humidity of 20%, light source wavelength of 400-760 nm, and room temperature.

[0085] Table 1

[0086]

[0087] Comparing Experiments 1 and 2, it can be seen that although both P25 type titanium dioxide and mixed-crystal nano-titanium dioxide contain rutile and anatase phases, their respective rutile phase proportions differ. For the mixed-crystal nano-titanium dioxide with a rutile phase proportion of 90%, its isoprene conversion rate under visible light irradiation in the 400-760nm wavelength band is much higher than that of commercial P25 type titanium dioxide, and it still exhibits relatively high carbon dioxide selectivity even at a higher conversion rate. Comparing Experiments 2 and 3, it can be seen that the copper oxide cluster-modified mixed-crystal nano-titanium dioxide shows a further improvement in selectivity compared to the mixed-crystal nano-titanium dioxide, but the improvement is small. This may be related to the excessive loading of copper oxide clusters. However, overall, the modification of copper oxide clusters increases the absorption of visible light by the catalyst, and the Cu in the clusters... + It is also an excellent electron-trapping species, greatly improving carrier separation efficiency and transport speed, thus exhibiting good photocatalytic performance under visible light. Comparing experiments 1 and 4, it can be seen that by constructing a heterojunction composite material using bismuth vanadate, a narrow-bandgap photosensitive semiconductor, and titanium dioxide, its activity under visible light is significantly improved. Furthermore, because the dispersant hexadecyltrimethylammonium bromide was added during the preparation process, the prepared catalyst did not exhibit severe agglomeration, which lays the foundation for its good visible light activity. Overall, the catalysts used all showed good isoprene degradation effects under laboratory conditions and have good applicability.

[0088] The catalyst of this invention is inexpensive, highly stable, and environmentally friendly. In practical applications, it can achieve photocatalytic degradation of isoprene emitted by plants in the atmosphere through foliar spraying and ground spraying, and oxidize it into carbon dioxide, thereby reducing the generation of pollutants such as ozone and secondary organic aerosols by isoprene in the atmosphere through photochemical reactions.

[0089] Therefore, it is feasible to use the catalyst for the photocatalytic degradation of isoprene emitted by plants in the atmospheric environment. The required light source is sunlight, enabling timely photocatalytic degradation of isoprene released from plant leaves. The sprayed catalyst adheres evenly to the plant leaves, coming into contact with the isoprene and receiving uniform sunlight, thus achieving low-energy, high-activity degradation. In practical applications, the prepared catalyst suspension can be sprayed over forests using drones to address the environmental remediation of isoprene emitted by plants.

[0090] This invention employs photocatalytic oxidation technology, requiring no heating or electricity, and exhibits high photoactivity response in the visible light range, facilitating efficient utilization of sunlight. It can be applied via foliar or environmental spraying, allowing isoprene emitted by plants to directly contact the catalyst, which then oxidizes the isoprene to carbon dioxide under sunlight. Therefore, it is suitable for reaction systems involving the degradation of low-space-velocity, low-concentration isoprene emitted by plants in the atmosphere. Modification with copper oxide clusters and the construction of bismuth vanadate heterojunctions significantly broaden the absorption range of titanium dioxide in the visible light spectrum, thus significantly enhancing the photocatalytic performance of the catalyst under visible light. In tolerance experiments (resistance to deactivation and water resistance), the catalyst demonstrated good catalytic performance, indicating strong applicability, low environmental requirements, and high practical value.

[0091] It should be noted that the catalyst is not limited to nano-titanium dioxide, mixed-crystal nano-titanium dioxide modified with copper oxide clusters, and titanium dioxide heterostructure nanocomposites modified with bismuth vanadate. Pure-phase titanium dioxide, mixed-phase titanium dioxide, and bismuth vanadate materials prepared by other methods can also be used for the photocatalytic degradation of isoprene emitted by plants.

[0092] The above are merely preferred embodiments of the present invention and are not intended to limit the present 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. An application of a catalyst for the photocatalytic oxidation of isoprene emitted by plants under visible light, characterized in that, The catalyst comprises any of the following compounds or a combination thereof: Mixed-crystalline nano-titanium dioxide modified with copper oxide clusters, wherein the mixed-crystalline nano-titanium dioxide is composed of anatase, rutile, and a small portion of brookite, with rutile accounting for 90%; The method for using the catalyst for the photocatalytic oxidation of isoprene emitted by plants includes the following steps: The catalyst powder was dispersed in 5.5 ml of deionized water to obtain a mixture; The mixture is sprayed, coated, smeared, or poured onto the surface of the medium. By air drying or heating, a thin coating is formed on the surface of the medium by the catalyst, and isoprene is photocatalytically oxidized and degraded through the catalyst coating on the surface of the medium.

2. The application according to claim 1, characterized in that, The mixed-crystal nano-titanium dioxide includes nano-titanium dioxide prepared by the sol-gel method: The sol-gel method includes: Isopropyl titanate was dissolved in isopropanol to obtain the first mixture; Isopropanol and water were mixed evenly at a volume ratio of 1:2 and then added dropwise to the first mixture while stirring continuously to obtain a sol. After drying the prepared sol, it was calcined at different temperatures to obtain mixed-crystal nano-titanium dioxide powder prepared by the sol-gel method.

3. The application according to claim 2, characterized in that, Methods for preparing mixed-crystal nano-titanium dioxide using the sol-gel method include: Dissolve 5 ml of isopropyl titanate in 10 ml of isopropanol and stir continuously for 30 min to mix it evenly, thus obtaining the first mixture. Add 30 ml of isopropanol aqueous solution dropwise to the first mixture. The addition process is carried out at room temperature with continuous stirring to obtain a white sol. After the white sol was aged at room temperature for 1-3 hours, it was placed in a forced-air drying oven and dried overnight at 100℃. Then, the titanium dioxide precursor was placed in a muffle furnace and heated at a heating rate of 5-20℃ / min, and kept at 500-800℃ for 2 hours to obtain mixed-crystal nano-titanium dioxide powder prepared by the sol-gel method.

4. The application according to claim 2, characterized in that, Methods for preparing copper oxide cluster-modified mixed-crystal nano-titanium dioxide include: Copper sulfate pentahydrate is dissolved in water to form a second mixture; The mixed-crystal nano-titanium dioxide powder was dispersed in the second mixture and stirred vigorously at 80-100℃ for 1 h to obtain the third mixture. After centrifugation, washing and drying of the third mixture, mixed-crystal nano-titanium dioxide modified with copper oxide clusters is obtained.

5. The application according to claim 4, characterized in that, Methods for preparing copper oxide cluster-modified mixed-crystal nano-titanium dioxide include: Add 15.6 mg of copper sulfate pentahydrate to 15 ml of deionized water and sonicate for 2-10 min to dissolve it, thus obtaining the second mixture; 250 mg of mixed-crystal nano-titanium dioxide powder was added to the second mixture, ultrasonicated at room temperature for 20 min, and then heated and stirred at 80-100℃ for 1 h to obtain the third mixture. The third mixture was centrifuged, the supernatant was poured off, and then washed with deionized water and centrifuged several times. The resulting precipitate was then dried at 80-100℃ and ground into powder to obtain copper oxide cluster-modified mixed-crystal nano-titanium dioxide.

6. An application as described in any one of claims 1-5, characterized in that, The medium includes: stainless steel metal discs, plant leaves, tree trunks, building surfaces, or soil; The light source in the photocatalytic oxidation experiment had a wavelength range of 400-760 nm and a temperature of room temperature.

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