Preparation method and application of photocatalytic ferroelectric heterojunction with photothermal-pyroelectric effect

Abstract

This invention discloses a method for preparing a photocatalytic ferroelectric heterojunction with photothermal-pyroelectric effect, comprising: Step 1, preparing carboxylated BaTiO3 nanoparticles (BaTiO3NPs), by adding the carboxylic acid-modified ferroelectric material and a metal salt solution together to a mixed solution of H2O and ethanol, and stirring to obtain a mixed solution; wherein the ferroelectric material is BaTiO3NPs, and the metal salt is In(NO3)3·4H2O; Step 2, adding a mixed solution of ammonia and ethanol to the mixed solution, reacting in an oil bath at 80°C for 30 min, centrifuging, washing and drying to obtain BaTiO3 / In(OH)3, and calcining at high temperature in a muffle furnace to obtain a BaTiO3 / In2O3 heterojunction; Step 3, grinding and mixing the obtained BaTiO3 / In2O3 with NaBH4 in a certain proportion, and calcining in a tube furnace under an argon atmosphere to obtain a black BaTiO3 / B-In2O3 heterojunction. By combining semiconductor materials with photothermal conversion properties with pyroelectric materials, a heterojunction is prepared that exhibits high photocatalytic reduction activity, thereby improving catalytic efficiency.

Description

Technical Field

[0001] This invention relates to a method for preparing and applying a photocatalytic ferroelectric heterojunction with photothermal-pyroelectric effect, belonging to the field of photocatalytic materials. Background Technology

[0002] Excessive CO2 emissions have led to an increasingly severe global greenhouse effect. Photocatalysis, particularly photocatalytic reduction of CO2, is a crucial strategy for solar energy development and utilization, possessing immense potential in alleviating global environmental pollution and the energy crisis. Utilizing sustainable solar energy to convert CO2 into high-value-added chemicals is an effective green approach to simultaneously address environmental pollution and the energy crisis. Traditional photocatalysts, due to their wide band gaps, can only absorb ultraviolet light with wavelengths less than 380 nm, achieving a solar energy utilization rate of only 3-5%, while infrared light, which accounts for over 50% of solar energy, is often neglected. Currently, traditional photocatalysts still suffer from narrow light absorption ranges, rapid electron-hole recombination rates, and low light conversion efficiency. Seeking highly efficient photocatalytic reduction catalysts for CO2 remains a significant goal in the field of photocatalysis. Increasing the catalyst's absorption of sunlight and improving electron-hole separation efficiency are two main approaches to improving photocatalytic efficiency. In recent years, methods that accelerate electron-hole separation by constructing external fields have attracted widespread attention due to their high efficiency. Pyroelectric materials, under temperature changes, participate in catalytic reactions by releasing surface-bound charges generated by spontaneous polarization. Simultaneously, the resulting pyroelectric electric field can also promote carrier separation efficiency. Combining photothermal conversion materials with pyroelectric materials utilizes the heat generated by near-infrared light as the driving force for temperature fluctuations in the pyroelectric material. This allows the pyroelectric effect to release charges and generate pyroelectric potentials, participating in photocatalytic reactions and improving the material's photocatalytic efficiency.

[0003] Among pyroelectric materials, BaTiO3 is widely used due to its large pyroelectric coefficient and suitable Curie temperature (130℃). In2O3-x, as a non-stoichiometric black indium oxide (B-In2O3), can absorb light across the entire solar spectrum and exhibits a high photothermal conversion effect. B-In2O3 can achieve photothermal reverse water-gas conversion (RWGS) with 100% selectivity under ambient conditions. In this invention, In2O3 is grown in situ on the surface of barium titanate, and a BaTiO3 / B-In2O3 heterojunction is prepared by high-temperature reduction. Under sunlight irradiation, the heat generated by B-In2O3 provides the driving force for the temperature change of the pyroelectric effect of BaTiO3. The release of charge and the generation of pyroelectric potential by BaTiO3 further act on B-In2O3, affecting its photocatalytic reaction. This study combines the photothermal effect, pyroelectric effect, and photocatalysis to investigate the photocatalytic reduction performance of the BaTiO3 / B-In2O3 heterojunction for CO2 reduction and reveals its reaction mechanism. This provides a theoretical basis for the design of highly efficient photocatalysts based on pyroelectric materials. Therefore, exploring how the built-in electric field of pyroelectricity can accelerate the separation and transfer of photogenerated carriers, and further improve the photocatalytic activity of BaTiO3 / B-In2O3 heterojunctions, is a challenge that researchers need to address next. Summary of the Invention

[0004] This invention designs and develops a method for preparing a photocatalytic ferroelectric heterojunction with photothermal-pyroelectric effect. By combining a semiconductor material with photothermal conversion properties with a pyroelectric material, the prepared heterojunction has high photocatalytic reduction activity and improves catalytic efficiency.

[0005] This invention also provides an application of a photocatalytic ferroelectric heterojunction with photothermal-pyroelectric effect, in which the prepared BaTiO3 / B-In2O3 heterojunction agent is used for photocatalytic carbon dioxide reduction reaction.

[0006] The technical solution provided by this invention is as follows:

[0007] A method for preparing a photocatalytic ferroelectric heterojunction with photothermal-pyroelectric effect, comprising:

[0008] Step 1: Prepare carboxylated BaTiO3 NPs by adding them together with the metal salt solution to a mixed solution of H2O and ethanol, and stirring to obtain a mixed solution;

[0009] The metal salt is In(NO3)3·4H2O;

[0010] Step 2: Add ammonia and ethanol solution to the mixed solution to form a homogeneous solution, and react in an oil bath at 80°C for 30 min. After centrifugation, washing and drying, BaTiO3 / In(OH)3 is obtained. Then, it is calcined at high temperature in a muffle furnace to obtain BaTiO3 / In2O3 heterojunction.

[0011] Step 3: Grind and mix the obtained BaTiO3 / In2O3 with NaBH4 in a certain proportion, and then calcine and wash them in an argon atmosphere in a tube furnace to obtain BaTiO3 / B-In2O3 heterojunction.

[0012] Preferably, the preparation process of the carboxylated BaTiO3 NPs includes:

[0013] 0.50 mL of 6.4 mmol of 3-aminopropyltriethoxysilane was added dropwise to a DMF solution containing succinic anhydride and stirred at room temperature for 3 h to generate N-3-(triethoxysilyl)propyl-4-carboxybutyramide. BaTiO3 NPs were added to this solvent and dispersed in the mixed solvent. After stirring at room temperature for 8 h, the mixture was washed three times with distilled water and ethanol at 5000 rpm. The mixture was then dried under vacuum at 60 °C for 10 h to obtain carboxylated BaTiO3 NPs.

[0014] The mixture contained 0.30 g of succinic anhydride, 3 mmol of DMF, and 20 mL of DMF. The mixed solvent was a 1:5 volume ratio of deionized water and DMF solution.

[0015] Preferably, in step one, the volume ratio of the mixed solution of H2O and ethanol is 1:3.

[0016] Preferably, in step two, the calcination temperature in the muffle furnace is 450°C and the calcination time is 3 hours.

[0017] Preferably, step three includes:

[0018] BTO / In2O3 and NaBH4 were ground and mixed evenly at a mass ratio of 1:2. The mixture was calcined in an argon atmosphere in a tube furnace at 400℃ for 3 hours, then water was added and stirred for 12 hours. The mixture was then washed twice with H2O and ethanol and centrifuged until the residual NaBH4 was completely removed. The mixture was then dried at 60℃ to obtain black BTO / B-In2O3.

[0019] An application of a photocatalytic ferroelectric heterojunction with photothermal-pyroelectric effect is disclosed, wherein a BaTiO3 / B-In2O3 heterojunction is prepared using the aforementioned method for preparing a photocatalytic ferroelectric heterojunction with photothermal-pyroelectric effect, and the BaTiO3 / B-In2O3 heterojunction is used for photocatalytic carbon dioxide reduction reaction.

[0020] The beneficial effects of this invention are as follows: In the process of preparing BTO / B-In2O3 heterojunctions, carboxyl-modified BaTiO3 nanoparticles are added to a solution containing In(NO3)3·4H2O, and the positively charged In... 3+ The BTO / In₂O₃ nanoparticles are adsorbed onto the surface of carboxylated BaTiO₃ nanoparticles via electrostatic attraction. Then, ammonia is added, and under solvothermal conditions, In(OH)₃ nanoparticles grow in situ on the surface of the BaTiO₃ nanoparticles. Unanchored In(OH)₃ nanoparticles are removed by centrifugation and washing, followed by high-temperature calcination to obtain a BTO / In₂O₃ heterojunction. BTO / In₂O₃ and NaBH₄ are ground and mixed uniformly at a mass ratio of 1:2, and then calcined in an argon atmosphere at 400℃ for 3 hours to obtain a BTO / B-In₂O₃ heterojunction, demonstrating its significant application potential in photocatalysis.

[0021] In this invention, after 4 hours of full-spectrum reaction, BTO, In₂O₃, B-In₂O₃, BTO / In₂O₃, BTO / B-In₂O₃, and BTO / B-In₂O₃ under temperature fluctuations under photocatalytic reduction of CO₂ to CO. The CO yields of BTO, In₂O₃, B-In₂O₃, BTO / In₂O₃, and BTO / B-In₂O₃ were 24.14, 27.14, 42.53, 85.46, and 146.56 μmol·g⁻¹, respectively. -1 ·h -1 The CO yield of BTO / B-In2O3 was 6.07 times, 5.4 times, 3.45 times, and 1.71 times that of BTO, In2O3, B-In2O3, and BTO / In2O3 under the same conditions, respectively. Photocatalytic CO reduction tests were performed on BTO / B-In2O3 with the lamp source turned on and off every 10 minutes (approximately 8 cycles). The results showed that the CO yield of the BTO / B-In2O3 heterojunction was further improved, reaching 215.43 μmol·g⁻¹. -1 ·h -1 The efficiency of BTO / B-In2O3 under no temperature change is 1.47 times that of BTO / B-In2O3, indicating that the pyroelectric effect of BTO can improve the photocatalytic CO2 reduction efficiency of heterojunction materials.

[0022] In the field of materials applications, this method comprehensively considers that under full-spectrum light irradiation, B-In2O3 in the BTO / B-In2O3 heterojunction can act as a photothermal conversion agent, providing a driving force for the pyroelectric effect of BaTiO3 through temperature change (ΔT). ΔT causes BaTiO3 to polarize and release surface charge under sunlight irradiation, thereby affecting the carrier separation rate and electron transport rate in B-In2O3 nanoparticles, resulting in higher photocatalytic CO2 reduction efficiency. The photothermal-pyroelectric-photocatalyst BTO / B-In2O3 heterojunction constructed by introducing photothermal and pyroelectric effects exhibits high photocatalytic CO2 reduction activity. Among pyroelectric materials, BaTiO3 has a large pyroelectric coefficient and a suitable Curie temperature (130℃), making it a traditional pyroelectric material. Combining semiconductor materials with photothermal conversion properties with pyroelectric materials, utilizing light as the driving force for the pyroelectric effect, will provide new insights for novel and efficient photothermal-pyroelectric-photocatalysts. Attached Figure Description

[0023] Figure 1 is a transmission electron microscope (TEM) image of the BTO / B-In2O3 heterojunction obtained in this invention.

[0024] Figure 1(a) is a transmission electron microscope image of the BTO NPs described in this invention.

[0025] Figure 1(b) is a transmission electron microscope image of the BTO / In2O3 heterojunction described in this invention.

[0026] Figure 1(c) is a transmission electron microscope image of the BTO / B-In2O3 heterojunction described in this invention.

[0027] Figure 1(d) is a transmission electron microscope image of the BTO / B-In2O3 heterojunction described in this invention.

[0028] Figure 1(e) is an EDS elemental mapping image of Ba element in the BTO / B-In2O3 heterojunction described in this invention.

[0029] Figure 1(f) is an EDS elemental mapping image of Ti element in the BTO / B-In2O3 heterojunction described in this invention.

[0030] Figure 1(g) is an EDS elemental mapping image of the O element in the BTO / B-In2O3 heterojunction described in this invention.

[0031] Figure 1(h) is an EDS elemental mapping image of the In element in the BTO / B-In2O3 heterojunction described in this invention.

[0032] Figure 2 The image shows the X-ray diffraction pattern of the BTO / B-In2O3 heterojunction obtained in this invention.

[0033] Figure 3(a) shows the temperature changes of the blank sample, BTO, In2O3, BTO / In2O3, B-In2O3 and BTO / B-In2O3 under full-spectrum irradiation as described in this invention.

[0034] Figure 3(b) is a three-dimensional temperature change histogram according to the present invention.

[0035] Figure 4(a) shows the CO production of BTO, In2O3, B-In2O3, BTO / In2O3 and BTO / B-In2O3 and BTO / B-In2O3 under temperature fluctuations as described in this invention.

[0036] Figure 4(b) shows the CO yield of BTO, In2O3, B-In2O3, BTO / In2O3 and BTO / B-In2O3 and BTO / B-In2O3 under temperature fluctuations as described in this invention. Detailed Implementation

[0037] The present invention will now be described in further detail with reference to the accompanying drawings, so that those skilled in the art can implement it based on the description.

[0038] As shown in Figures 1-4, this invention provides a method for preparing a photocatalytic ferroelectric heterojunction with photothermal-pyroelectric effect, comprising:

[0039] Step 1: Prepare carboxylated BaTiO3 NPs by adding them together with a metal salt solution to a mixed solution of H2O and ethanol, and stirring to obtain a mixed solution; wherein the metal salt is In(NO3)3·4H2O.

[0040] Step 2: Add ammonia and ethanol solution to the mixed solution to form a homogeneous solution, and react in an oil bath at 80°C for 30 min. After centrifugation, washing and drying, BaTiO3 / In(OH)3 is obtained. Then, it is calcined at high temperature in a muffle furnace to obtain BaTiO3 / In2O3 heterojunction.

[0041] Step 3: Grind and mix the obtained BaTiO3 / In2O3 with NaBH4 in a certain proportion, and then calcine and wash them in an argon atmosphere in a tube furnace to obtain BaTiO3 / B-In2O3 heterojunction.

[0042] Specifically, it includes:

[0043] Preparation of carboxylated BaTiO3 NPs:

[0044] 0.50 mL of 6.4 mmol of 3-aminopropyltriethoxysilane was added dropwise to a DMF solution containing succinic anhydride and stirred at room temperature for 3 h to generate N-3-(triethoxysilyl)propyl-4-carboxybutyramide. BaTiO3 NPs were added to this solvent and dispersed in the mixed solvent. After stirring at room temperature for 8 h, the mixture was washed three times with distilled water and ethanol at 5000 rpm. The mixture was then dried under vacuum at 60 °C for 10 h to obtain carboxylated BaTiO3 NPs.

[0045] The mixture contained 0.30 g of succinic anhydride, 3 mmol of DMF, and 20 mL of DMF. The mixed solvent was a 1:5 volume ratio of deionized water and DMF solution.

[0046] The carboxylic acid-modified BaTiO3 NPs ferroelectric material and metal salt solution were placed in a mixed solution of NH3·H2O and ethanol and stirred to obtain a mixed solution.

[0047] The ferroelectric material is BaTiO3 nanoparticles, the metal salt is In(NO3)3·4H2O, and the volume ratio of the H2O and ethanol mixture is (V:V = 1:3). When carboxyl-modified BaTiO3 NPs are added to the above solution, the positively charged In... 3+ They will be adsorbed onto the surface of carboxylated BaTiO3 NPs through electrostatic attraction.

[0048] Ammonia and ethanol solutions were added to the mixed solution to form a homogeneous solution, and the mixture was reacted in an oil bath at 80°C for 30 min. After centrifugation, washing and drying, BaTiO3 / In(OH)3 was obtained. Under solvothermal conditions, In(OH)3 nanoparticles grew in situ on the surface of BaTiO3 nanoparticles. Unanchored In(OH)3 nanoparticles were removed by centrifugation and washing. Then, the mixture was calcined at 450°C in a muffle furnace for 3 h to obtain a BaTiO3 / In2O3 heterojunction.

[0049] All centrifugal washing was performed 3 to 5 times, the centrifuge speed was 5000 r / min, and the drying conditions were 60℃-80℃ in a vacuum drying oven.

[0050] BTO / In2O3 and NaBH4 were ground and mixed evenly at a mass ratio of 1:2. The mixture was calcined in an argon atmosphere in a tube furnace at 400℃ for 3 hours, then water was added and stirred for 12 hours. The mixture was then washed twice with H2O and ethanol and centrifuged until the residual NaBH4 was completely removed. The mixture was then dried at 60℃ to obtain black BTO / B-In2O3.

[0051] The BaTiO3 / B-In2O3 heterojunction prepared in this invention can be used as a catalyst for photocatalytic carbon dioxide reduction reaction.

[0052] BTO is short for BaTiO3.

[0053] Example

[0054] 2g of In(NO3)3·4H2O was added to solution A to form a homogeneous solution. Then, carboxylated BTO NPs were added to the homogeneous solution and stirred for 12h. Solution B was then slowly added dropwise. After the addition was complete, the mixture was stirred in an oil bath at 80℃ for 30min. After centrifugation, washing, and vacuum drying at 60℃, BaTiO3 / In(OH)3 was obtained. Then, it was calcined at high temperature in a muffle furnace to obtain a BaTiO3 / In2O3 heterojunction.

[0055] BTO / In2O3 and NaBH4 were ground and mixed evenly at a mass ratio of 1:2. The mixture was then calcined in an argon atmosphere in a tube furnace at 400℃ for 3 hours. Water was added and stirred for 12 hours until the residual NaBH4 was completely removed. The mixture was then washed twice with H2O and ethanol, centrifuged, and dried at 60℃ to obtain black BTO / B-In2O3.

[0056] Solution A is a mixture of C2H5OH and H2O in a volume ratio of 3:1, and solvent B is a mixture of 18 mL NH3·H2O and 54 mL ethanol.

[0057] As shown in Figures 1(a) and 1(c), TEM observation of the morphology and structure of the samples reveals that BTO NPs are irregularly shaped spherical particles with smooth surfaces and an average diameter of approximately 200 nm. From the TEM images of the BTO / B-In2O3 heterojunction, numerous irregular B-In2O3 nanoparticles can be clearly seen surrounding the spherical BTO NPs, indicating successful in-situ preparation of B-In2O3 NPs on the surface of BTO NPs. The HRTEM image of BTO / B-In2O3, Figure 1(b), clearly shows a lattice with a spacing of 0.398 nm, corresponding to the (100) crystal plane of the tetragonal BTO NPs, while lattices with spacings of 0.247 nm and 0.292 nm correspond to the (002) and (222) crystal planes of In, respectively. This indicates that after NaBH4 reduction, BTO / In2O3 not only generates B-In2O3 but also elemental In. Figures 1(d) to (h) show the EDS elemental mapping diagrams, which show that Ba, Ti, O, and In elements are uniformly distributed on the BTO / B-In2O3 surface. Compared with Ba and Ti, the positions of O and In elements indicate that B-In2O3 is anchored on the surface of BTO NPs.

[0058] like Figure 2As shown, the crystal structures of BTO, In2O3, B-In2O3, BTO / In2O3, and BTO / B-In2O3 were characterized by XRD. The original BTO showed typical tetragonal phase diffraction peaks. The peaks of In2O3 at 21.5°, 30.6°, 35.2°, 37.7°, 41.8°, 45.7°, 51.0°, and 60.6° correspond to the (211), (222), (400), (411), (332), (431), (440), and (622) crystal planes of In2O3 (JCPDS#71-2194). Unlike In₂O₃, B-In₂O₃ exhibited characteristic peaks at 30.5° (222), 33.1° (321), 35.5° (400), 51.0° (440), and 60.7° (622), among which the diffraction peaks at 32.9° (101), 36.3° (002), 39.2° (110), 54.5° (112), 56.6° (200), 63.2° (103), 67.0° (211), and 69.1° (202) all belong to In. This result is consistent with the TEM analysis, indicating that some In₂O₃ is reduced to B-In₂O₃, and some In₂O₃ is reduced to elemental In. Characteristic XRD diffraction peaks of In₂O₃ and BTO can be observed in the BTO / In₂O₃ heterojunction, indicating that In₂O₃ NPs were successfully grown on the surface of carboxylated BTO NPs. After reduction with NaBH4, the characteristic diffraction peaks of BTO NPs and B-In2O3 indicate that In2O3 on the surface of BTO NPs was successfully reduced to B-In2O3.

[0059] like Figure 3(a) , 3(b)As shown, the temperature changes of the blank sample, BTO, In2O3, B-In2O3, BTO / B-In2O3, and BTO / In2O3 over time under full-spectrum irradiation are illustrated. The catalyst surface temperature was monitored in real-time using an infrared thermometer. After 60 seconds of full-spectrum light irradiation, the temperature changes of the blank sample, BTO, In2O3, BTO / In2O3, B-In2O3, and BTO / B-In2O3 were 46℃, 70.8℃, 112.7℃, 116.7℃, 248.7℃, and 238.2℃, respectively. Both B-In2O3 and BTO / B-In2O3 heterojunctions exhibit excellent photothermal conversion performance. This is because the large number of oxygen vacancies introduced on the B-In2O3 surface allows the material to absorb light across the entire spectrum, improving the photothermal conversion efficiency. B-In2O3, however, has superior light absorption properties compared to BTO / B-In2O3, thus exhibiting a higher photothermal conversion efficiency. The photothermal-pyroelectric-photocatalytic reduction of CO2 was investigated using a full-spectrum light source to explore the catalytic activity of BTO, In2O3, B-In2O3, BTO / In2O3, BTO / B-In2O3, and BTO / B-In2O3 in reducing CO2 under temperature fluctuations.

[0060] Figure 4(a) shows the photocatalytic reduction of CO2 to CO yield of BTO, In2O3, B-In2O3, BTO / In2O3, BTO / B-In2O3, and BTO / B-In2O3 under temperature fluctuations after 4 h of reaction. Figure 4(b) shows the CO yield of the corresponding catalysts. The CO yields of BTO, In2O3, B-In2O3, BTO / In2O3, and BTO / B-In2O3 are 24.14, 27.14, 42.53, 85.46, and 146.56 μmol·g, respectively. -1 ·h -1 The CO yield of BTO / B-In2O3 was 6.07 times, 5.4 times, 3.45 times, and 1.71 times that of BTO, In2O3, B-In2O3, and BTO / In2O3 under the same conditions, respectively. Photocatalytic CO reduction tests were performed on BTO / B-In2O3 with the lamp source turned on and off every 10 minutes (approximately 8 cycles). The results showed that the CO yield of the BTO / B-In2O3 heterojunction was further improved, reaching 215.43 μmol·g⁻¹. -1 ·h -1 The efficiency of BTO / B-In2O3 under no temperature change is 1.47 times that of BTO / B-In2O3, indicating that the pyroelectric effect of BTO can improve the photocatalytic CO2 reduction efficiency of heterojunction materials.

[0061] The preparation method of BTO / B-In2O3 provided by this invention is simple, safe, and energy-efficient, with no toxic solvents used in the preparation process, making it green and environmentally friendly. It demonstrates high photocatalytic CO2 reduction efficiency, and its cost and photocatalytic CO2 reduction efficiency have significant industrial application value.

[0062] Although embodiments of the present invention have been disclosed above, they are not limited to the applications listed in the specification and embodiments. They can be applied to various fields suitable for the present invention. For those skilled in the art, other modifications can be easily made. Therefore, without departing from the general concept defined by the claims and their equivalents, the present invention is not limited to the specific details and illustrations shown and described herein.

Claims

1. A method for preparing a photocatalytic ferroelectric heterojunction with photothermal-pyroelectric effect, characterized in that, include: Step 1: Prepare carboxylated BaTiO3 NPs by adding them together with the metal salt solution to a mixed solution of H2O and ethanol, and stirring to obtain a mixed solution; The metal salt is In(NO3)3·4H2O; The preparation process of the carboxylated BaTiO3 NPs includes: 0.50 mL of 3-aminopropyltriethoxysilane was added dropwise to a DMF solution containing succinic anhydride and stirred at room temperature for 3 h to generate N-3-(triethoxysilyl)propyl-4-carboxybutyramide. BaTiO3 NPs were added to this solvent and dispersed in the mixed solvent. After stirring at room temperature for 8 h, the NPs were washed three times with distilled water and ethanol at 5000 rpm. The NPs were then dried under vacuum at 60 °C for 10 h to obtain carboxylated BaTiO3 NPs. The ingredients included 0.30 g of succinic anhydride, 3 mmol of DMF, and 20 mL of DMF. The mixed solvent was a 1:5 volume ratio of deionized water and DMF solution. Step 2: Add ammonia and ethanol solution to the mixed solution to form a homogeneous solution, and react in an oil bath at 80 ℃ for 30 min. After centrifugation, washing and drying, BaTiO3 / In(OH)3 is obtained. Then, it is calcined at high temperature in a muffle furnace to obtain BaTiO3 / In2O3 heterojunction. Step 3: Grind and mix the obtained BaTiO3 / In2O3 with NaBH4 in a certain proportion, then calcine and wash the mixture in an argon atmosphere in a tube furnace to obtain a BaTiO3 / B-In2O3 heterojunction, comprising: BaTiO3 / In2O3 with NaBH4 in a mass ratio of 1 :2 was mixed uniformly by grinding, calcined in a tube furnace at 400 °C for 3 h in an argon atmosphere, then stirred with water for 12 h, washed with H2O and ethanol for 2 times, centrifuged until the residual NaBH4 was completely removed, dried at 60 °C, to obtain black BaTiO3 / B-In2O 3。 2. The method for preparing a photocatalytic ferroelectric heterojunction with photothermal-pyroelectric effect according to claim 1, characterized in that, In step one, the volume ratio of water to ethanol in the mixed solution of H2O and ethanol is 1:

3.

3. The method for preparing a photocatalytic ferroelectric heterojunction with photothermal-pyroelectric effect according to claim 2, characterized in that, In step two, the calcination temperature in the muffle furnace is 450 °C, and the calcination time is 3 h.

4. An application of a photocatalytic ferroelectric heterojunction with photothermal-pyroelectric effect, characterized in that, BaTiO3 / B-In2O3 heterojunctions are prepared using the method for preparing photocatalytic ferroelectric heterojunctions with photothermal-pyroelectric effect as described in any one of claims 1-3, characterized in that the BaTiO3 / B-In2O3 heterojunctions are used for photocatalytic carbon dioxide reduction reaction.

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