Lanthanum oxycarbonate-gallium oxide composite photocatalyst for catalytic reduction of carbon dioxide and preparation method of lanthanum oxycarbonate-gallium oxide composite photocatalyst

Abstract

The invention relates to the field of photocatalysts, in particular to a lanthanum oxycarbonate-gallium oxide composite photocatalyst for catalytic reduction of carbon dioxide and a preparation method thereof.The preparation method comprises the following steps that S1, sodium carbonate, sodium fluoride and lanthanum nitrate hexahydrate are dissolved in deionized water and stirred and mixed at the room temperature, then a hydrothermal reaction is conducted, and a precursor is obtained; after cooling, filtering, washing and drying in sequence to obtain a sodium lanthanum carbonate precursor; s2, weighing gallium nitrate, mixing with the sodium lanthanum carbonate precursor, grinding, and uniformly mixing to obtain a composite precursor; and S3, in a protective atmosphere, carrying out temperature programming treatment on the composite precursor, and naturally cooling to room temperature to obtain the lanthanum oxycarbonate-gallium oxide composite photocatalyst. The photocatalytic CO2 reduction performance of the composite photocatalyst prepared by the invention is superior to that of single lanthanum oxycarbonate and gallium oxide catalysts, and the composite photocatalyst shows excellent application potential.

Description

Technical Field

[0001] This invention relates to the field of photocatalysts, specifically to a lanthanum oxycarbonate-gallium oxide composite photocatalyst for the catalytic reduction of carbon dioxide and its preparation method. Background Technology

[0002] With the rapid development of global industrialization, the fossil fuel-based energy structure, while supporting the progress of human society, has also brought two severe challenges: the energy crisis caused by the depletion of fossil fuels, and global warming and ocean acidification caused by the large amounts of carbon dioxide (CO2) produced by their combustion. Against this backdrop, developing technologies that can convert the greenhouse gas CO2 into high-value-added carbon-based fuels (such as carbon monoxide, methane, methanol, and formic acid) is considered one of the ideal paths to achieving a "carbon cycle" and sustainable energy supply. Among numerous conversion technologies, semiconductor photocatalysis technology shows great application potential because it can directly utilize inexhaustible solar energy to drive the CO2 reduction reaction under mild conditions and is environmentally friendly.

[0003] The core of photocatalytic CO2 reduction lies in efficient, stable, and low-cost photocatalytic materials. An ideal photocatalyst should possess the following characteristics: broad-spectrum solar response, high efficiency in photogenerated electron-hole separation and migration, a suitable band structure to match the redox potential of CO2 reduction, abundant surface active sites to promote reactant adsorption and activation, and excellent photochemical stability. Although researchers have conducted extensive and in-depth studies on traditional semiconductor materials such as TiO2, ZnO, and CdS for decades, each has significant limitations. For example, TiO2 and ZnO have wide band gaps, absorbing only a small portion of ultraviolet light from sunlight, resulting in extremely low utilization efficiency of visible light; while CdS, although possessing suitable visible light response, suffers from severe photocorrosion and questionable stability. Therefore, developing novel, efficient, and stable visible-light-responsive photocatalytic materials remains an urgent need for technological advancement in this field.

[0004] In the exploration of novel photocatalysts, lanthanides (also known as rare earth elements) and their compounds, with their unique electronic structures, have gradually demonstrated irreplaceable importance and become a research frontier in materials science and photocatalysis. Among the many lanthanides, lanthanum (La), as a representative member, is relatively inexpensive and abundant, and its typical compounds, such as La₂O₃, La(OH)₃, and La₂O₂CO₃, have shown excellent performance in photocatalysis. In particular, lanthanum oxycarbonate (La₂O₂CO₃), with its layered crystal structure exposing La... 3+Lanthanum oxycarbonate (LOC) photocatalytic sites can serve as ideal CO2 adsorption and activation centers, and their semiconductor properties combined with the advantages of the aforementioned lanthanides make them a star material for CO2 photoreduction reactions. However, the preparation methods of LOC photocatalytic materials still face many challenges. Traditional hydrothermal and precipitation methods often suffer from uncontrollable morphology, easy particle agglomeration, and limited specific surface area, resulting in insufficient exposure of active sites. More importantly, the photogenerated carrier separation efficiency of pure LOC photocatalytic materials still needs further improvement. To overcome these bottlenecks, researchers have tried various strategies, among which constructing heterojunctions and using novel precursors for controllable synthesis are two effective approaches. Thermal decomposition of carbonate precursors is a classic method for preparing specific metal oxides or hydroxides. This method can achieve precise control over the morphology, crystal phase, and pore structure of the product through the composition and structural design of the precursor. Sodium lanthanum carbonate (Na4La2(CO3)5) is a well-defined lanthanum-based carbonate complex salt. During its thermal decomposition, the escape of sodium ions and carbonate ions creates a dynamic environment for the reconstruction of La species, readily forming active materials with high specific surface area and porous structures. This provides ideal conditions for exposing more surface active sites. Meanwhile, combining lanthanide materials with another suitable semiconductor to construct heterojunctions is a recognized effective strategy for improving charge separation efficiency. Gallium oxide (Ga2O3) is a semiconductor with a wide bandgap (~4.8 eV). Although its own photoresponse range is narrow, its conduction band position is very negative, its reduction ability is strong, and its electron mobility is high. When gallium oxide is combined with lanthanum oxycarbonate, they can potentially form a Type-II heterojunction or a direct Z-type heterojunction, thereby establishing a built-in electric field at the interface. This drives photogenerated electrons to migrate directionally from the conduction band of one material to the valence band of the other, achieving efficient spatial separation of electrons and holes and greatly suppressing the recombination probability.

[0005] Based on the above analysis, although existing technologies have recognized the potential of lanthanum oxycarbonate and gallium oxide in photocatalysis, there are currently no published documents or patent reports on the in-situ preparation of lanthanum oxycarbonate-gallium oxide composite photocatalysts with high CO2 photoreduction activity by controlling the calcination of sodium lanthanum carbonate and gallium oxide.

[0006] The purpose of this invention is to provide a simple, one-step calcination method for preparing highly active lanthanum oxycarbonate-gallium oxide composite photocatalysts. This method ingeniously utilizes the structural evolution of sodium lanthanum carbonate during heat treatment to conduct an interfacial reaction with gallium oxide, successfully obtaining high-purity lanthanum oxycarbonate. More importantly, it may form a tight heterojunction between lanthanum oxycarbonate and gallium oxide in situ. The material prepared by this method is expected to fully leverage the triple advantages of lanthanides in light capture, charge separation, and CO2 activation, while combining the synergistic effect of the heterojunction in promoting charge separation, thus exhibiting activity and stability far exceeding that of single components in the photocatalytic CO2 reduction reaction. This process route is simple, the raw materials are readily available, and it provides a novel approach for developing efficient and stable lanthanide photocatalytic materials, possessing significant scientific research value and promising industrial application prospects. Summary of the Invention

[0007] To address the problems existing in the prior art, the present invention aims to provide a simple, one-step calcination method for preparing highly active lanthanum oxycarbonate-gallium oxide composite photocatalysts. This method ingeniously utilizes the structural evolution of sodium lanthanum carbonate during heat treatment to conduct an interfacial reaction with gallium oxide, successfully obtaining high-purity lanthanum oxycarbonate. More importantly, it may form a tight heterojunction between lanthanum oxycarbonate and gallium oxide in situ. The material prepared by this method is expected to fully leverage the triple advantages of lanthanides in light capture, charge separation, and CO2 activation, while combining the synergistic effect of the heterojunction in promoting charge separation, thus exhibiting activity and stability far exceeding that of single components in the photocatalytic CO2 reduction reaction. This process route is simple, the raw materials are readily available, and it provides a novel approach for developing efficient and stable lanthanide photocatalytic materials, possessing significant scientific research value and promising industrial application prospects.

[0008] The objective of this invention is achieved through the following technical solution: In a first aspect, the present invention provides a method for preparing a lanthanum oxycarbonate-gallium oxide composite photocatalyst for catalytic reduction of carbon dioxide, comprising the following steps: S1. Dissolve sodium carbonate, sodium fluoride and lanthanum nitrate hexahydrate in deionized water, stir and mix at room temperature, then carry out a hydrothermal reaction, and after cooling, filter, wash and dry in sequence to obtain sodium lanthanum carbonate precursor. S2. Weigh gallium nitrate and sodium lanthanum carbonate precursor, mix them, grind them, and after uniform mixing, obtain the composite precursor. S3. Under a protective atmosphere, the composite precursor is heated to a controlled temperature and then naturally cooled to room temperature to obtain a lanthanum carbonate-gallium oxide composite photocatalyst.

[0009] Preferably, in S1, the molar ratio of sodium carbonate, sodium fluoride, and lanthanum nitrate hexahydrate is 10:6:2, and the molar ratio of deionized water to sodium carbonate is 20-50:1.

[0010] Preferably, in step S1, the hydrothermal reaction temperature is 140-220℃ and the reaction time is 12-24h.

[0011] Preferably, in step S1, the washing process includes: washing the filter cake obtained by filtration with deionized water and anhydrous ethanol 3 to 5 times in sequence; the drying conditions are: vacuum drying at 60-80°C for 12-24 hours.

[0012] Preferably, the mass ratio of sodium lanthanum carbonate precursor to gallium nitrate in S2 is 1:0.25-4.0.

[0013] Preferably, the protective atmosphere in S3 is argon or nitrogen; the temperature is programmed to 400-800℃ and kept at a constant temperature for 2-8 hours, with a programmed heating rate of 2-5℃ / min.

[0014] Secondly, the present invention provides a lanthanum oxycarbonate-gallium oxide composite photocatalyst for catalytic reduction of carbon dioxide, which is prepared by the above-described preparation method.

[0015] Thirdly, the present invention provides a lanthanum carbonate oxygenate-gallium oxide composite photocatalyst for the catalytic reduction of carbon dioxide.

[0016] The beneficial effects of this invention are as follows: 1. This invention controls key parameters in each step using a hydrothermal method to achieve directional nucleation and growth of sodium lanthanum carbonate precursor, ensuring high crystallinity and uniform morphology. After uniform grinding and in-situ composite under a protective atmosphere, lanthanum oxycarbonate and gallium oxide form a tightly bonded heterojunction structure, effectively avoiding the problems of particle agglomeration and loose interfacial bonding in traditional preparation processes, and significantly improving the structural stability and service life of the catalyst.

[0017] 2. During the calcination process, sodium lanthanum carbonate decomposes to form lanthanum oxycarbonate, which then recombines with gallium oxide in situ, creating a tight heterojunction interface that effectively promotes the separation and migration of photogenerated carriers. This catalyst is specifically designed for CO2 catalytic reduction and can drive the reaction using light energy at room temperature and pressure, eliminating the need for harsh conditions such as high temperature and pressure. It is energy-efficient and environmentally friendly. Its excellent CO2 adsorption and activation capacity and reduction selectivity can efficiently convert the greenhouse gas CO2 into high-value-added carbon-based fuels (such as carbon monoxide), alleviating the environmental pressure caused by CO2 emissions and achieving the recycling of carbon resources, thus meeting the needs of sustainable energy and environmental development under the "dual carbon" goal.

[0018] 3. The composite photocatalyst prepared in this invention exhibits superior CO2 reduction performance compared to single lanthanum oxycarbonate and gallium oxide catalysts, demonstrating excellent application potential. Compared to single lanthanum oxycarbonate or gallium oxide catalysts, the composite catalyst of this invention shows a more than fourfold increase in CO2 reduction activity, overcoming the technical bottlenecks of low activity and rapid carrier recombination in traditional photocatalytic materials.

[0019] 4. The raw materials used in this invention are all commercially available general chemicals, which are abundant and inexpensive, and do not require scarce or high-cost reagents. The preparation process only involves simple operations such as hydrothermal reaction, grinding, and programmed temperature calcination. The steps are clear, the parameters are well-defined, and the reproducibility is high. No complex and precision equipment is required. It can be directly adapted to existing chemical production lines for large-scale production, which combines economic benefits and industrial feasibility. Attached Figure Description

[0020] The present invention will be further described with reference to the accompanying drawings, but the embodiments in the drawings do not constitute any limitation on the present invention. For those skilled in the art, other drawings can be obtained based on the following drawings without creative effort.

[0021] Figure 1 Scanning electron microscope (SEM) image of the lanthanum oxycarbonate-gallium oxide photocatalyst prepared in Example 1.

[0022] Figure 2 Transmission electron microscope (TEM) image of the lanthanum oxycarbonate-gallium oxide photocatalyst prepared in Example 3.

[0023] Figure 3 The graph shows a comparison of the photocatalytic carbon dioxide reduction activities of the lanthanum oxycarbonate-gallium oxide photocatalysts prepared in Examples 1-5 and the comparative catalysts. Detailed Implementation

[0024] The technical solution of the present invention is illustrated below through specific examples. It should be understood that the one or more method steps mentioned in the present invention do not preclude the existence of other method steps before or after the combined steps, or the insertion of other method steps between these explicitly mentioned steps; it should also be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the present invention. Furthermore, unless otherwise stated, the numbering of each method step is merely a convenient tool for identifying each method step, and not for limiting the order of the method steps or defining the scope of the present invention. Changes or adjustments to their relative relationships, without substantially altering the technical content, should also be considered within the scope of the present invention.

[0025] To better understand the above technical solutions, exemplary embodiments of the present invention are described in more detail below. While exemplary embodiments of the present invention are shown, it should be understood that the present invention can be implemented in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided to enable a more thorough understanding of the present invention and to fully convey the scope of the invention to those skilled in the art.

[0026] The present invention will be further described below with reference to the following embodiments.

[0027] Example 1 A method for preparing a lanthanum carbonate-gallium oxide composite photocatalyst includes the following steps: 0.08 mol sodium carbonate, 0.048 mol sodium fluoride, and 0.016 mol lanthanum nitrate hexahydrate (molar ratio 10:6:2) were dissolved in deionized water, with a water:sodium carbonate molar ratio of 30:1. The mixture was magnetically stirred at room temperature for 1 hour to ensure the formation of a homogeneous precursor suspension. The mixture was then transferred to a polytetrafluoroethylene-lined high-pressure hydrothermal reactor and reacted at 200°C for 24 hours. After the reaction, the mixture was allowed to cool naturally to room temperature. The product was filtered and washed several times with deionized water and anhydrous ethanol, and finally dried under vacuum at 80°C to obtain sodium lanthanum carbonate.

[0028] Next, weigh 0.2g of the prepared sodium lanthanum carbonate and 0.8g of gallium nitrate, i.e., the mass ratio of sodium lanthanum carbonate to gallium nitrate is 1:4. Place both in an agate mortar and grind thoroughly for 1 hour to obtain a highly homogeneous mixture. Then, transfer it to an alumina crucible, place it in a muffle furnace, and calcine it to 550℃ at a programmed heating rate of 3℃ / min under a nitrogen atmosphere, and maintain this temperature for 4 hours. After calcination, allow it to cool naturally to room temperature with the furnace to obtain the lanthanum carbonate-gallium oxide photocatalyst material.

[0029] Figure 1 Scanning electron microscope image of the lanthanum oxycarbonate-gallium oxide photocatalyst material prepared for this embodiment.

[0030] This catalyst was used for photocatalytic CO2 reduction, and the CO yield after 5 hours of reaction was 8.0 μmol / g (see activity comparison). Figure 3 .

[0031] Example 2 0.08 mol sodium carbonate, 0.048 mol sodium fluoride, and 0.016 mol lanthanum nitrate hexahydrate (molar ratio 10:6:2) were dissolved in deionized water, with a water:sodium carbonate molar ratio of 30:1. The mixture was magnetically stirred at room temperature for 1 hour to ensure the formation of a homogeneous precursor suspension. The mixture was then transferred to a polytetrafluoroethylene-lined high-pressure hydrothermal reactor and reacted at 220°C for 12 hours. After the reaction, the mixture was allowed to cool naturally to room temperature. The product was filtered and washed several times with deionized water and anhydrous ethanol, and finally dried under vacuum at 60°C to obtain sodium lanthanum carbonate.

[0032] Next, weigh 0.8g of the prepared sodium lanthanum carbonate and 0.2g of gallium nitrate (i.e., the mass ratio of sodium lanthanum carbonate to gallium nitrate is 1:0.25). Place both in an agate mortar and grind thoroughly for 1 hour to obtain a highly homogeneous mixture. Then, transfer it to an alumina crucible, place it in a muffle furnace, and calcine it to 550℃ at a programmed heating rate of 3℃ / min under an argon atmosphere, and maintain this temperature for 4 hours. After calcination, allow it to cool naturally to room temperature with the furnace to obtain the lanthanum carbonate-gallium oxide photocatalyst material.

[0033] This catalyst was used for photocatalytic CO2 reduction, and the CO yield was 5.50 μmol / g after 5 hours of reaction (see activity comparison). Figure 3 .

[0034] Example 3 0.08 mol sodium carbonate, 0.048 mol sodium fluoride, and 0.016 mol lanthanum nitrate hexahydrate (molar ratio 10:6:2) were dissolved in deionized water, with a water:sodium carbonate molar ratio of 30:1. The mixture was magnetically stirred at room temperature for 1 hour to ensure the formation of a homogeneous precursor suspension. The mixture was then transferred to a polytetrafluoroethylene-lined high-pressure hydrothermal reactor and reacted at 220°C for 24 hours. After the reaction, the mixture was allowed to cool naturally to room temperature. The product was filtered and washed several times with deionized water and anhydrous ethanol, and finally dried under vacuum at 60°C to obtain sodium lanthanum carbonate.

[0035] Next, weigh 0.4g of the prepared sodium lanthanum carbonate and 0.6g of gallium nitrate (i.e., the mass ratio of sodium lanthanum carbonate to gallium nitrate is 1:1.5). Place both in an agate mortar and grind thoroughly for 1 hour to obtain a highly homogeneous mixture. Then, transfer it to an alumina crucible, place it in a muffle furnace, and calcine it to 550℃ at a programmed heating rate of 3℃ / min under an argon atmosphere, and maintain this temperature for 4 hours. After calcination, allow it to cool naturally to room temperature with the furnace to obtain the lanthanum carbonate-gallium oxide photocatalyst material.

[0036] Figure 2 Transmission electron microscope (TEM) image of the lanthanum oxycarbonate-gallium oxide photocatalytic material prepared for this embodiment.

[0037] This catalyst was used for photocatalytic CO2 reduction, and the CO yield after 5 hours of reaction was 16.0 μmol / g (see activity comparison). Figure 3 .

[0038] Example 4 0.08 mol sodium carbonate, 0.048 mol sodium fluoride, and 0.016 mol lanthanum nitrate hexahydrate (molar ratio 10:6:2) were dissolved in deionized water, with a water:sodium carbonate molar ratio of 30:1. The mixture was magnetically stirred at room temperature for 1 hour to ensure the formation of a homogeneous precursor suspension. The mixture was then transferred to a polytetrafluoroethylene-lined high-pressure hydrothermal reactor and reacted at 220°C for 24 hours. After the reaction, the mixture was allowed to cool naturally to room temperature. The product was filtered and washed several times with deionized water and anhydrous ethanol, and finally dried under vacuum at 60°C to obtain sodium lanthanum carbonate.

[0039] Next, weigh 0.4g of the prepared sodium lanthanum carbonate and 0.6g of gallium nitrate (i.e., the mass ratio of sodium lanthanum carbonate to gallium nitrate is 1:1.5). Place both in an agate mortar and grind thoroughly for 1 hour to obtain a highly homogeneous mixture. Then, transfer it to an alumina crucible, place it in a muffle furnace, and calcine it at a programmed heating rate of 5℃ / min to 800℃ under a nitrogen atmosphere, and maintain this temperature for 2 hours. After calcination, allow it to cool naturally to room temperature with the furnace to obtain the lanthanum carbonate-gallium oxide photocatalyst material.

[0040] This catalyst was used for photocatalytic CO2 reduction, and the CO yield after 5 hours of reaction was 14.5 μmol / g (see activity comparison). Figure 3 .

[0041] Example 5 0.08 mol sodium carbonate, 0.048 mol sodium fluoride, and 0.016 mol lanthanum nitrate hexahydrate (molar ratio 10:6:2) were dissolved in deionized water, with a water:sodium carbonate molar ratio of 30:1. The mixture was magnetically stirred at room temperature for 1 hour to ensure the formation of a homogeneous precursor suspension. The mixture was then transferred to a polytetrafluoroethylene-lined high-pressure hydrothermal reactor and reacted at 220°C for 24 hours. After the reaction, the mixture was allowed to cool naturally to room temperature. The product was filtered and washed several times with deionized water and anhydrous ethanol, and finally dried under vacuum at 60°C to obtain sodium lanthanum carbonate.

[0042] Next, weigh 0.4g of the prepared sodium lanthanum carbonate and 0.6g of gallium nitrate, i.e., the mass ratio of sodium lanthanum carbonate to gallium nitrate is 1:1.5. Place both in an agate mortar and grind thoroughly for 1 hour to obtain a highly homogeneous mixture. Then, transfer it to an alumina crucible, place it in a muffle furnace, and calcine it to 400℃ at a programmed heating rate of 2℃ / min under an argon atmosphere, and maintain this temperature for 8 hours. After calcination, allow it to cool naturally to room temperature with the furnace to obtain the lanthanum carbonate-gallium oxide photocatalyst material.

[0043] This catalyst was used for photocatalytic CO2 reduction, and the CO yield was 12 μmol / g after 5 hours of reaction (see activity comparison). Figure 3 .

[0044] Comparative Example 1 (pure lanthanum oxycarbonate photocatalyst) 0.08 mol sodium carbonate, 0.048 mol sodium fluoride, and 0.016 mol lanthanum nitrate hexahydrate (molar ratio 10:6:2) were dissolved in deionized water, with a water:sodium carbonate molar ratio of 30:1. The mixture was magnetically stirred at room temperature for 1 hour to ensure the formation of a homogeneous precursor suspension. The mixture was then transferred to a polytetrafluoroethylene-lined high-pressure hydrothermal reactor and reacted at 220°C for 24 hours. After the reaction, the mixture was allowed to cool naturally to room temperature. The product was filtered and washed several times with deionized water and anhydrous ethanol, and finally dried under vacuum at 60°C to obtain sodium lanthanum carbonate.

[0045] The prepared sodium lanthanum carbonate was then thoroughly ground for 0.5 hours. Subsequently, it was transferred to an alumina crucible and placed in a muffle furnace. Under an argon atmosphere, the temperature was programmed to rise to 550°C at a rate of 3°C / min, and then calcined at this temperature for 4 hours. After calcination, the furnace was allowed to cool naturally to room temperature to obtain pure lanthanum oxycarbonate photocatalyst material.

[0046] This catalyst was used for photocatalytic CO2 reduction, and the CO yield after 5 hours of reaction was 4.0 μmol / g (see activity comparison). Figure 3 .

[0047] Comparative Example 2 (Pure gallium oxide photocatalyst material) 1g of gallium nitrate (Ga(NO3)3) was directly placed in an agate mortar and ground thoroughly for 0.5h. Then, it was transferred to an alumina crucible and placed in a muffle furnace. The furnace was heated to 550℃ at a programmed heating rate of 3℃ / min under an argon atmosphere and calcined at this temperature for 4h. After calcination, the furnace was allowed to cool naturally to room temperature to obtain pure gallium oxide photocatalyst material.

[0048] This catalyst was used for photocatalytic CO2 reduction, and the CO yield after 5 hours of reaction was 3.3 μmol / g (see activity comparison). Figure 3 .

[0049] To describe the present invention more clearly, the following work has also been done: (1) Scanning electron microscope images were taken using the lanthanum oxycarbonate-gallium oxide photocatalyst prepared in Example 1, as shown in the image. Figure 1 As shown, a stacked, sheet-like porous structure is clearly visible in this photocatalyst; transmission electron microscopy images were taken using the lanthanum oxycarbonate-gallium oxide photocatalyst prepared in Example 3, as shown... Figure 2 As shown, it is clear that the C, La and Ga elements in the photocatalyst are evenly distributed, indicating that they are tightly bonded and form a uniform composite of lanthanum oxycarbonate and gallium oxide.

[0050] (2) In order to compare the advantages of the prepared composite photocatalysts, the present invention prepared separate lanthanum oxycarbonate and gallium oxide photocatalysts as comparative examples 1 and 2 using preparation conditions similar to those of Example 3, which showed the best photocatalytic performance.

[0051] (3) The lanthanum oxycarbonate-gallium oxide photocatalysts obtained in Examples 1-5, as well as the lanthanum oxycarbonate (Comparative Example 1) and gallium oxide (Comparative Example 2) photocatalysts alone, were tested to produce carbon monoxide by photocatalytic reduction of carbon dioxide.

[0052] The experimental conditions were: reaction temperature 5℃, carbon dioxide reaction pressure at atmospheric pressure, reactor volume 100mL, photocatalyst dosage 30mg, water 200uL, reaction time 5 hours, and Xe lamp.

[0053] After testing and analysis, the results are as follows: Figure 3 As shown.

[0054] The results show that the activities of the lanthanum oxycarbonate-gallium oxide composite catalysts prepared in this invention are higher than those of the simple lanthanum oxycarbonate and gallium oxide photocatalysts. In particular, under optimized conditions, the lanthanum oxycarbonate-gallium oxide photocatalyst prepared in Example 3 has the highest activity in photocatalytic reduction of CO2 to CO, which is more than 4 times that of the comparative example.

[0055] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. The illustrative expressions of the above terms in this specification should not be construed as necessarily referring to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. In addition, those skilled in the art can combine and integrate the different embodiments or examples described in this specification.

[0056] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present invention.

Claims

1. A method for preparing a lanthanum oxycarbonate-gallium oxide composite photocatalyst for catalytic reduction of carbon dioxide, characterized in that, Includes the following steps: S1. Dissolve sodium carbonate, sodium fluoride and lanthanum nitrate hexahydrate in deionized water, stir and mix at room temperature, then carry out a hydrothermal reaction, and after cooling, filter, wash and dry in sequence to obtain sodium lanthanum carbonate precursor. S2. Weigh gallium nitrate and sodium lanthanum carbonate precursor, mix them, grind them, and after uniform mixing, obtain the composite precursor. S3. Under a protective atmosphere, the composite precursor is heated to a controlled temperature and then naturally cooled to room temperature to obtain a lanthanum carbonate-gallium oxide composite photocatalyst.

2. The method for preparing a lanthanum oxycarbonate-gallium oxide composite photocatalyst for catalytic reduction of carbon dioxide according to claim 1, characterized in that, In S1, the molar ratio of sodium carbonate, sodium fluoride, and lanthanum nitrate hexahydrate is 10:6:2, and the molar ratio of deionized water to sodium carbonate is 20-50:

1.

3. The method for preparing a lanthanum oxycarbonate-gallium oxide composite photocatalyst for catalytic reduction of carbon dioxide according to claim 1, characterized in that, In S1, the hydrothermal reaction temperature is 140-220℃ and the reaction time is 12-24h.

4. The method for preparing a lanthanum oxycarbonate-gallium oxide composite photocatalyst for catalytic reduction of carbon dioxide according to claim 1, characterized in that, In step S1, the washing process includes: washing the filter cake obtained by filtration with deionized water and anhydrous ethanol 3 to 5 times in sequence; the drying conditions are: vacuum drying at 60-80℃ for 12-24 hours.

5. The method for preparing a lanthanum oxycarbonate-gallium oxide composite photocatalyst for catalytic reduction of carbon dioxide according to claim 1, characterized in that, In S2, the mass ratio of sodium lanthanum carbonate precursor to gallium nitrate is 1:0.25-4.

0.

6. The method for preparing a lanthanum oxycarbonate-gallium oxide composite photocatalyst for catalytic reduction of carbon dioxide according to claim 1, characterized in that, The protective atmosphere in S3 is argon or nitrogen; the temperature is programmed to 400-800℃ and kept at a constant temperature for 2-8 hours, with a programmed heating rate of 2-5℃ / min.

7. A lanthanum oxycarbonate-gallium oxide composite photocatalyst, characterized in that, The lanthanum oxycarbonate-gallium oxide composite photocatalyst was prepared using the preparation method described in claim 1.

8. The lanthanum oxycarbonate-gallium oxide composite photocatalyst of claim 7 is used for the catalytic reduction of carbon dioxide.

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