Preparation method and application of a nano-alumina-based heterojunction catalyst

Abstract

This invention discloses a method for preparing a heterojunction catalyst based on nano-alumina and its application. The method employs a hydrothermal approach, simultaneously growing wide-bandgap semiconductor TiO2 and narrow-bandgap semiconductor CdS on the surface of nano-sized Al2O3, each having an atomic-level epitaxial interface, to construct an Al2O3@TiO2_CdS heterostructure. Al2O3 acts as a charge-conducting intermediate, promoting the directional migration of photogenerated electrons from CdS to TiO2 in the Al2O3@TiO2_CdS heterostructure. This results in a 10-fold improvement in visible-light hydrogen production performance compared to the heterostructure without the charge-conducting intermediate, revealing the advantages of alumina as an inexpensive charge-conducting intermediate in optimizing the interface between the catalyst and semiconductors compared to traditional metals.

Description

Technical Field

[0001] This invention relates to the field of photocatalytic water-to-hydrogen technology, specifically to a method for preparing and applying a heterojunction catalyst based on nano-alumina. Background Technology

[0002] High oil prices and ever-increasing greenhouse gas emissions remain unresolved global economic and climate issues. For a sustainable future for humanity, we must comprehensively utilize resources, protect the environment, and live in harmony with nature. The shortage of fossil fuels and global environmental problems urgently need to be addressed. Hydrogen energy, as a clean and pollution-free energy source, has attracted increasing attention. Hydrogen has the following characteristics: good thermal conductivity, easy recovery, good combustion performance, low loss, environmental friendliness, non-corrosive water byproduct, and high energy density per unit mass.

[0003] Traditional hydrogen production methods, such as hydrocarbon steam reforming, water electrolysis, and heavy oil oxidation, while still highly efficient, limit the development of energy-efficient hydrogen resources due to their high energy consumption and the generation of harmful substances during the conversion process. Therefore, converting water into hydrogen using solar energy is considered a promising solution to these problems.

[0004] The limitations of photocatalytic water-to-hydrogen production processes mainly stem from two factors: competition between the recombination and transfer of photogenerated electrons and holes; and insufficient utilization of solar energy. An ideal photocatalyst should possess a broad photoresponse range and effectively suppress the recombination of photogenerated charges and holes.

[0005] Currently, traditional methods for broadening the light absorption range of photocatalysts mainly include anion / cation doping, vacancy introduction, metal nano-ion resonance, fuel sensitization, and heterojunction construction. Compared to other strategies for broadening the light absorption range, heterojunctions constructed by loading narrow-bandgap semiconductors such as CdS and CuO onto the surface of wide-bandgap photocatalysts not only achieve visible light performance but also improve the separation characteristics of photogenerated charges. Furthermore, they offer greater flexibility in material selection and implementation, making them a more ideal strategy for broadening the light absorption range of materials. In heterostructures composed of a wide-bandgap semiconductor and a narrow-bandgap semiconductor with a higher conduction band bottom-valence band top position, the migration of photogenerated electrons from the narrow-bandgap semiconductor excited by low-energy visible light to the wide-bandgap semiconductor is key to simultaneously achieving high visible light absorption and high charge separation characteristics. Unfortunately, due to the significant differences in elemental composition, lattice structure, and electronic structure between wide-bandgap semiconductors and narrow-bandgap semiconductors, it is usually difficult to form strong interfacial interactions when they come into direct contact. This results in a high charge migration barrier at the interface, which severely hinders the directional migration of photogenerated charges excited by visible light across the interface and seriously affects the photocatalytic activity and charge separation characteristics of the aforementioned heterostructures under visible light irradiation.

[0006] Therefore, in order to solve the above problems, the present invention is thus developed. Summary of the Invention

[0007] To address at least one of the aforementioned technical problems, the present invention aims to provide a method for preparing and applying a heterojunction catalyst based on nano-alumina. An Al2O3@TiO2_CdS heterojunction catalyst was successfully synthesized using a hydrothermal method. In this catalyst, Al2O3 acts as a charge-conducting intermediate, promoting the directional migration of photogenerated electrons from CdS to TiO2 in the Al2O3@TiO2_CdS heterojunction. This results in a 10-fold improvement in visible light hydrogen production performance compared to the heterostructure without a charge-conducting intermediate.

[0008] The technical solution of this invention is:

[0009] One objective of this invention is to provide a method for preparing a heterojunction catalyst based on nano-alumina, wherein the heterojunction catalyst is Al2O3@TiO2_CdS, comprising the following steps:

[0010] (1) Take 100~300mg of precursor Al2O3, 20~60mL of deionized water and magnetic stirring rod, add them to the inner liner of a 100mL hydrothermal reactor, and stir magnetically for 10~20 minutes;

[0011] (2) Add Cd(NO3)2·4H2O and thiourea in a molar ratio of 1:1 according to the target amount of CdS, and continue stirring for 30~60 minutes;

[0012] (3) Next, add 150~350mg of TiO2 sol and continue stirring for 30~60 minutes;

[0013] (4) Remove the magnetic stir bar, seal the polytetrafluoroethylene inner liner and place it in the stainless steel outer shell of the reactor, and place it in a forced-air drying oven at 180°C for 3 to 6 hours;

[0014] (5) After the hydrothermal reactor cools naturally to room temperature, the residual ions on the surface of the product are removed by centrifugation using deionized water, and then dried at 60-80°C for 8-12 hours to obtain the heterojunction catalyst used for photocatalysis.

[0015] Preferably, the precursor Al2O3 is obtained by the following method:

[0016] (11) Add 10-20g of Al2O3 powder and 300-400mL of deionized water to a beaker with a volume of 400-500mL, stir magnetically for 10-20 minutes, and then continue to sonicate for 30-60 minutes;

[0017] (12) After the ultrasound is finished, let it stand for 1 to 2 hours, pour off the upper suspension, and repeat the above operation 3 to 5 times until the Al2O3 powder can settle quickly in 1 to 2 hours and the upper liquid becomes transparent.

[0018] (13) The obtained sediment was dried in air at 60-80℃ for 8-12 hours to obtain the precursor Al2O3.

[0019] Preferably, the Al2O3 powder in step (11) has a particle size of 100-150 nm and a purity of 99.99%.

[0020] Preferably, the target amount of CdS in step (2) is calculated based on a molar ratio of Al2O3:TiO2:CdS of 2:1:1.

[0021] Preferably, the preparation method of TiO2 sol in step (3) is as follows:

[0022] (31) Add 1-2g of nitric acid to 100-500mL of water and stir well;

[0023] (32) Add 10~30g of TiO2 powder while stirring;

[0024] (33) Continue stirring for 1 to 3 hours until the mixture is homogeneous, and obtain TiO2 sol.

[0025] Another objective of this invention is to provide the application of the Al2O3@TiO2_CdS heterojunction catalyst prepared by the above method in photocatalytic water production of hydrogen.

[0026] Preferably, 30-60 mg of the sample with the supported catalyst is added to a reactor containing 80-100 mL of deionized water and 1-4 g of sacrificial agent. The reactor is magnetically stirred, and the temperature of the reactor is maintained at room temperature using a circulating water cooling system. The reactor is then evacuated and irradiated with visible light of wavelength λ>420 nm using a full-spectrum or cutoff filter to perform photocatalytic hydrogen production.

[0027] Preferably, the step of supporting the catalyst is as follows:

[0028] S1. Add 20-50 mg of the sample to be tested to 10-40 mL of deionizer, and add 10-20 mL of sacrificial agent and 0.5-1 mL of a catalyst precursor solution with a mass concentration of 1-2 mg / mL. Irradiate with a xenon lamp with full spectrum for 1 hour under magnetic stirring.

[0029] S2. After irradiation, centrifuge, wash and dry to collect the sample loaded with the co-catalyst.

[0030] Preferably, the cocatalyst precursor in step S1 includes at least one of H2PtCl6 and H2AuCl6.

[0031] Preferably, the sacrificial agent is at least one of methanol, Na2S, and Na2SO3.

[0032] Compared with the prior art, the advantages of the present invention are:

[0033] This invention discloses a method for preparing and applying a heterojunction catalyst based on nano-alumina. An Al2O3@TiO2_CdS heterojunction catalyst was successfully synthesized via a hydrothermal method. In the Al2O3@TiO2_CdS heterojunction, Al2O3 serves as both a precursor for TiO2 and an epitaxial growth substrate for CdS, forming atomic-level epitaxial interfaces of Al2O3 / CdS and Al2O3 / TiO2. This greatly facilitates Al2O3's role as an intermediate for charge transport between TiO2 and CdS. Because CdS is directly epitaxially grown on the Al2O3 surface, donor states are formed within the CdS. The donor levels on the semiconductor side of the metal-semiconductor interface can effectively reduce the Schottky barrier. Therefore, the donor states in TiO2 and CdS can lower the Schottky barrier at the Al2O3 / CdS and Al2O3 / TiO2 interfaces, facilitating cross-interface charge transport, promoting the directional injection of photogenerated electrons from CdS into TiO2, improving charge transfer efficiency, suppressing the recombination of photogenerated electrons and holes, and greatly improving the visible light photocatalytic hydrogen production efficiency. Verification shows that the heterojunction catalyst prepared in this invention exhibits 10 times better visible light hydrogen production performance than the catalyst without a charge-conducting intermediate. Attached Figure Description

[0034] The present invention will be further described below with reference to the accompanying drawings and embodiments:

[0035] Figure 1 The XRD diffraction pattern of the heterojunction catalyst prepared in Example 1 of this invention;

[0036] Figure 2 (a) is a SEM cross-sectional scan of the heterojunction catalyst prepared in Example 1 of the present invention, and (b) to (e) are EDS elemental distribution diagrams of Cd, Ti, S and O in the heterojunction catalyst, respectively.

[0037] Figure 3 This is a particle size analysis diagram of Al2O3, the precursor in Example 1 of the present invention. Detailed Implementation

[0038] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to specific embodiments and the accompanying drawings. It should be understood that these descriptions are merely exemplary and not intended to limit the scope of the invention. Furthermore, descriptions of well-known structures and techniques are omitted in the following description to avoid unnecessarily obscuring the concept of the invention.

[0039] An embodiment of the present invention discloses a method for preparing a heterojunction catalyst based on nano-alumina, wherein the heterojunction catalyst is Al2O3@TiO2_CdS, and the preparation method includes the following steps:

[0040] (1) Take 100~300mg of precursor Al2O3, 20~60mL of deionized water and magnetic stirring rod, add them to the inner liner of a 100mL hydrothermal reactor, and stir magnetically for 10~20 minutes;

[0041] (2) Add Cd(NO3)2·4H2O and thiourea in a molar ratio of 1:1 according to the target amount of CdS, and continue stirring for 30~60 minutes;

[0042] (3) Next, add 150~350mg of TiO2 sol and continue stirring for 30~60 minutes;

[0043] (4) Remove the magnetic stir bar, seal the polytetrafluoroethylene inner liner and place it in the stainless steel outer shell of the reactor, and place it in a forced-air drying oven at 180°C for 3 to 6 hours;

[0044] (5) After the hydrothermal reactor cools naturally to room temperature, the residual ions on the surface of the product are removed by centrifugation using deionized water, and then dried at 60-80°C for 8-12 hours to obtain the heterojunction catalyst used for photocatalysis.

[0045] According to some preferred embodiments of the present invention, the precursor Al2O3 is obtained by the following method:

[0046] (11) Add 10-20g of Al2O3 powder and 300-400mL of deionized water to a beaker with a volume of 400-500mL, stir magnetically for 10-20 minutes, and then continue to sonicate for 30-60 minutes;

[0047] (12) After the ultrasound is finished, let it stand for 1 to 2 hours, pour off the upper suspension, and repeat the above operation 3 to 5 times until the Al2O3 powder can settle quickly in 1 to 2 hours and the upper liquid becomes transparent.

[0048] (13) The obtained sediment was dried in air at 60-80℃ for 8-12 hours to obtain the precursor Al2O3.

[0049] According to some preferred embodiments of the present invention, the Al2O3 powder in step (11) has a particle size of 100-150 nm and a purity of 99.99%, as shown in the specific particle size analysis diagram. Figure 3 As shown. The precursor Al2O3 is obtained by sand milling for 30-60 minutes and then filtering. In this embodiment of the invention, the composite photocatalyst formed by nano-sized Al2O3 has a small particle size, which makes it easier to disperse in water to form a suspension, and it has good light transmittance, enabling it to better absorb a large amount of sunlight.

[0050] According to some preferred embodiments of the present invention, the preparation method of TiO2 sol in step (3) is as follows:

[0051] (31) Add 1-2g of nitric acid to 100-500mL of water and stir well;

[0052] (32) Add 10~30g of TiO2 powder while stirring;

[0053] (33) Continue stirring for 1 to 3 hours until the mixture is homogeneous, and obtain TiO2 sol.

[0054] According to some preferred embodiments of the present invention, the target amount of CdS in step (2) is calculated based on a molar ratio of Al2O3:TiO2:CdS of 2:1:1. Example 1

[0055] Preparation of Al2O3@TiO2_CdS heterojunction catalyst

[0056] Take 300 mg of precursor Al2O3, 50 mL of deionized water, and a magnetic stir bar, and add them to the inner liner of a 100 mL hydrothermal reactor. Stir magnetically for 10 minutes. Then add 150-350 mg of TiO2 sol and continue stirring for 30 minutes. Next, add Cd(NO3)2·4H2O and thiourea at a molar ratio of 1:1 according to the target amount of CdS, and continue stirring for 30 minutes. Remove the magnetic stir bar, seal the polytetrafluoroethylene inner liner, place it in the outer sleeve of the stainless steel reactor, and keep it in a forced-air oven at 180°C for 5 hours. After the hydrothermal reactor cools naturally to room temperature, wash away residual ions on the surface of the product using deionized water by centrifugation, and dry at 60°C for 12 hours to obtain the sample. Its XDR diffraction pattern is shown below. Figure 1 As shown in (5), the screenshots of the sample by SEM and EDS are as follows: Figure 2 As shown in (a) to (e).

[0057] Comparative Example 1: Preparation of precursor Al2O3

[0058] 10g of Al2O3 powder and 400mL of deionized water were added to a 500mL beaker. The mixture was magnetically stirred for 10 minutes, followed by sonication for 30 minutes. After sonication, the mixture was allowed to stand for 1 hour. The supernatant was then discarded, and this process was repeated three times until the Al2O3 powder settled rapidly within 1 hour, making the supernatant liquid transparent. The resulting precipitate was dried in air at 60℃ for 12 hours to obtain the precursor Al2O3. Its XDR diffraction pattern is shown below. Figure 1 As shown in (1).

[0059] Comparative Example 2: Preparation of CdS

[0060] Add Cd(NO3)2·4H2O and thiourea in a molar ratio of 1:1, and continue stirring for 30-60 minutes. Remove the magnetic stir bar, seal the polytetrafluoroethylene inner liner inside the stainless steel reactor, and place it in a forced-air oven at 180℃ for 4 hours. After the hydrothermal reactor cools naturally to room temperature, wash away residual ions on the product surface using deionized water by centrifugation, and dry at 60℃ for 12 hours to obtain the sample. Its XDR diffraction pattern is shown below. Figure 1 As shown in (2).

[0061] Comparative Example 3: Preparation of Al2O3@TiO2 heterojunction catalyst

[0062] Take 300 mg of the precursor Al₂O₃ from Comparative Example 1, add it to 40 mL of deionized water and a magnetic stir bar, and place it in the inner liner of a 100 mL hydrothermal reactor. Stir magnetically for 10 minutes. Then add 150-350 mg of TiO₂ sol and continue stirring for 30 minutes. Remove the magnetic stir bar, seal the polytetrafluoroethylene inner liner, place it in the outer shell of a stainless steel reactor, and keep it in a forced-air oven at 180°C for 5 hours. After the hydrothermal reactor cools naturally to room temperature, wash away residual ions on the surface of the product using deionized water by centrifugation, and dry it at 60°C for 12 hours to obtain the sample. Its XDR diffraction pattern is shown below. Figure 1 As shown in (3).

[0063] Comparative Example 4: Preparation of Al2O3@TiO2&CdS heterojunction catalyst

[0064] Take 300 mg of precursor Al₂O₃ from Comparative Example 1, 40 mL of deionized water, and a magnetic stir bar, and add them to the inner liner of a 100 mL hydrothermal reactor. Stir magnetically for 10 minutes, then add 150-350 mg of TiO₂ sol and continue stirring for 30 minutes. Remove the magnetic stir bar, seal the PTFE inner liner inside a stainless steel reactor jacket, and place it in a forced-air oven at 180°C for 5 hours. After the hydrothermal reactor cools naturally to room temperature, wash away residual ions on the product surface using deionized water via centrifugation. Then... The obtained product, Cd(NO3)2·4H2O and thiourea (at a CdS molar ratio of 1:1), 40 mL of deionized water, and a magnetic stir bar were added to the inner liner of the reactor, and stirring was continued for 30 minutes. The magnetic stir bar was removed, and the polytetrafluoroethylene inner liner was sealed and placed inside a stainless steel reactor jacket. The reactor was then placed in a forced-air oven at 180°C for 6 hours. After the hydrothermal reactor cooled naturally to room temperature, residual ions on the product surface were washed away using deionized water via centrifugation. The product was then dried at 60°C for 12 hours to obtain the sample. Its XDR diffraction pattern is shown below. Figure 1 As shown in (4).

[0065] like Figure 1 The XRD diffraction patterns of the samples obtained in Comparative Examples 1, 2, 3, 4 and Example 1 are shown. It can be seen that the CdS prepared by hydrothermal method contains both hexagonal and tetragonal phases. The precursor Al2O3 has a typical hexagonal structure, corresponding to card JCPDF-29-0063. The XRD pattern of the Al2O3@TiO2 core-shell structure basically retains the original Al2O3 diffraction peaks. The newly added peaks at 25.28° and 48.1° can be corresponding to (101) and (200) of the anatase phase TiO2, respectively, indicating that the hydrothermal process in ion water promotes the formation of anatase phase TiO2 on the Al2O3 surface. Compared with the Al2O3@TiO2 core-shell structure, the XRD diffraction pattern of the Al2O3@TiO2&CdS heterojunction adds cubic phase CdS at 30.8° and 36.6°. The presence of the 200 and hexagonal CdS (102) crystal planes indicates that subsequent heat treatment can continue to grow CdS with both hexagonal and cubic structures on the surface of the Al2O3@TiO2 core-shell structure. The XRD diffraction pattern of Al2O3@TiO2_CdS is similar to that of Al2O3@TiO2&CdS, with the main diffraction peaks still being those of the precursor Al2O3, while also exhibiting diffraction signals of anatase TiO2 and CdS with both hexagonal and cubic structures. This indicates that a one-step hydrothermal method can simultaneously promote the formation of TiO2 and CdS. It is noted that the specific diffraction peak intensities of the Al2O3@TiO2_CdS heterostructure and the Al2O3@TiO2&CdS heterostructure are significantly different, indicating that while they have similar phase compositions, the proportions of different phases differ.

[0066] pass Figure 2The interface scanning image of Al2O3@TiO2_CdS clearly shows that hemispherical CdS particles and tetrahedral TiO2_ particles grow simultaneously on the surface of the Al2O3@ matrix, and there is no obvious transition layer between CdS and Al2O3@, indicating that a direct interface has been formed between them. Figure 2 The EDS elemental distribution diagram further indicates that the hemispherical particles with a diameter of approximately 400 nm are CdS.

[0067] In summary, in the Al2O3@TiO2_CdS heterojunction of this invention, Al2O3 serves as both the precursor of TiO2 and the epitaxial growth substrate of CdS, forming atomic-level epitaxial interfaces of Al2O3 / CdS and Al2O3 / TiO2. This greatly facilitates Al2O3's role as an intermediate for charge transport between TiO2 and CdS. Since CdS is directly epitaxially grown on the Al2O3 surface, donor states are formed in CdS. The donor levels on the semiconductor side of the metal-semiconductor interface can effectively reduce the Schottky barrier. Therefore, the donor states in TiO2 and CdS can reduce the Schottky barrier at the Al2O3 / CdS and Al2O3 / TiO2 interfaces, facilitating cross-interface charge transport, promoting the directional injection of photogenerated electrons from CdS into TiO2, improving charge transfer efficiency, suppressing recombination of photogenerated electrons and holes, and significantly improving the visible light photocatalytic hydrogen production efficiency. Example 2

[0068] This invention provides an example of applying the heterojunction catalyst prepared by the method in Example 1 to a photocatalytic water-to-hydrogen reaction. Specifically, 30-60 mg of a sample with a supported catalyst is added to a reactor containing 80-100 mL of deionized water and 1-4 g of sacrificial agent. The reactor is magnetically stirred, and the temperature of the reactor is maintained at room temperature using a circulating water cooling system. The reactor is then evacuated, and irradiated with visible light of wavelength λ>420 nm using a full-spectrum or cutoff filter to perform photocatalytic hydrogen production.

[0069] More specifically, the supported catalyst: 50 mg of the sample to be tested in Example 1 was added to 40 mL of deionized water, along with 10 mL of anhydrous methanol and 0.5 mL of H2PtCl6 solution with a mass concentration of 1 mg / mL. After irradiation with a xenon lamp for 1 hour under magnetic stirring, the sample was centrifuged, washed, and dried to obtain the sample with the supported catalyst.

[0070] A sample containing 30 mg of the supported catalyst was added to a reactor containing 100 mL of deionized water and 1 g of sacrificial agent. The reactor was magnetically stirred and kept at room temperature using a circulating water cooling system. The reactor was then evacuated and irradiated with full-spectrum or visible light (with a cutoff filter wavelength λ > 420 nm). The gas composition in the reactor was tested by gas chromatography every 0.5 hours to obtain the hydrogen production.

[0071] Comparative Example 5

[0072] Supported catalyst: 50 mg of the test sample of Comparative Example 2 was added to 40 mL of deionized water, along with 10 mL of anhydrous methanol and 0.5 mL of H2PtCl6 solution with a mass concentration of 1 mg / mL. The sample was irradiated with a xenon lamp for 1 hour under magnetic stirring. After irradiation, the sample was centrifuged, washed, and dried to obtain the sample with supported catalyst.

[0073] A sample containing 30 mg of the supported catalyst was added to a reactor containing 100 mL of deionized water and 1 g of sacrificial agent. The reactor was magnetically stirred and kept at room temperature using a circulating water cooling system. The reactor was then evacuated and irradiated with full-spectrum or visible light (with a cutoff filter wavelength λ > 420 nm). The gas composition in the reactor was tested by gas chromatography every 0.5 hours to obtain the hydrogen production.

[0074] Comparative Example 6

[0075] Supported catalyst: 50 mg of the test sample of Comparative Example 3 was added to 40 mL of deionized water, along with 10 mL of anhydrous methanol and 0.5 mL of H2PtCl6 solution with a mass concentration of 1 mg / mL. The sample was irradiated with a xenon lamp for 1 hour under magnetic stirring. After irradiation, the sample was centrifuged, washed, and dried to obtain the sample with supported catalyst.

[0076] A sample containing 30 mg of the supported catalyst was added to a reactor containing 100 mL of deionized water and 1 g of sacrificial agent. The reactor was magnetically stirred and kept at room temperature using a circulating water cooling system. The reactor was then evacuated and irradiated with full-spectrum or visible light (with a cutoff filter wavelength λ > 420 nm). The gas composition in the reactor was tested by gas chromatography every 0.5 hours to obtain the hydrogen production.

[0077] Comparative Example 7

[0078] Supported catalyst: 50 mg of the test sample of Comparative Example 4 was added to 40 mL of deionized water, along with 10 mL of anhydrous methanol and 0.5 mL of H2PtCl6 solution with a mass concentration of 1 mg / mL. The sample was irradiated with a xenon lamp for 1 hour under magnetic stirring. After irradiation, the sample was centrifuged, washed, and dried to obtain the sample with supported catalyst.

[0079] A sample containing 30 mg of the supported catalyst was added to a reactor containing 100 mL of deionized water and 1 g of sacrificial agent. The reactor was magnetically stirred and kept at room temperature using a circulating water cooling system. The reactor was then evacuated and irradiated with full-spectrum or visible light (with a cutoff filter wavelength λ > 420 nm). The gas composition in the reactor was tested by gas chromatography every 0.5 hours to obtain the hydrogen production.

[0080] Table 1. Hydrogen production rates of Comparative Examples 5 to 7 and Example 2 under full-spectrum and visible light irradiation.

[0081] Implementation Comparative Example 5 Comparative Example 6 Comparative Example 7 Example 2 Hydrogen production rate at full spectrum (μmol / h / 50mg) 15.51 0.45 22.21 50.81 Hydrogen production rate under visible light (μmol / h / 50mg) 3.52 0.055 3.31 33.25

[0082] Results Analysis: As shown in Table 1, the hydrogen production rates of Comparative Examples 5 to 7 and Example 2 under full-spectrum and visible light irradiation were 15.51, 0.45, 22.21, and 50.81 μmol / h / 50 mg, and 3.52, 0.055, 3.31, and 33.25 μmol / h / 50 mg, respectively. Clearly, Example 2 exhibits superior photocatalytic hydrogen production performance in both the full-spectrum and visible light bands. It has been verified that the heterojunction catalyst prepared in Example 1 of this invention demonstrates a 10-fold improvement in visible light hydrogen production performance in photocatalytic water production compared to the method without a charge-conducting intermediate.

[0083] Other embodiments of the invention will readily occur to those skilled in the art upon consideration of the specification and practice of the invention. This application is intended to cover any uses or adaptations of the invention that follow the general principles of the invention and include common knowledge or customary techniques in the art not disclosed herein.

[0084] It should be understood that the present invention is not limited to the structure described above and shown in the accompanying drawings, and various modifications and changes can be made without departing from its scope.

Claims

1. A method for the preparation of a nano-alumina based heterojunction catalyst for photocatalytic hydrogen production from water, characterized by, The heterojunction catalyst is Al2O3@TiO2_CdS, and includes the following steps: (1) Take 100~300mg of precursor Al2O3, 20~60mL of deionized water and magnetic stirring rod, add them to the inner liner of a 100mL hydrothermal reactor, and stir magnetically for 10~20 minutes; (2) Add Cd(NO3)2·4H2O and thiourea in a molar ratio of 1:1 according to the target amount of CdS, and continue stirring for 30~60 minutes; (3) Next, add 150~350mg of TiO2 sol and continue stirring for 30~60 minutes; the preparation method of TiO2 sol in step (3) is as follows: (31) Add 1~2g of nitric acid to 100~500mL of water and stir evenly; (32) Add 10~30g of TiO2 powder while stirring; (33) Continue stirring for 1~3 hours and stir evenly to obtain TiO2 sol; (4) Remove the magnetic stirring rod, seal the polytetrafluoroethylene inner liner and place it in the stainless steel outer shell of the reactor, and place it in a forced-air drying oven at 180°C for 3 to 6 hours; (5) After the hydrothermal reactor cools naturally to room temperature, the residual ions on the surface of the product are removed by centrifugation using deionized water, and then dried at 60-80°C for 8-12 hours to obtain the heterojunction catalyst used for photocatalysis.

2. The method for preparing a nano-alumina-based heterojunction catalyst for photocatalytic hydrogen production from water according to claim 1, characterized in that, The precursor Al2O3 was obtained by the following method: (11) Add 10-20g of Al2O3 powder and 300-400mL of deionized water to a beaker with a volume of 400-500mL, stir magnetically for 10-20 minutes, and then continue to sonicate for 30-60 minutes; (12) After the ultrasound is finished, let it stand for 1 to 2 hours, pour off the upper suspension, and repeat the above operation 3 to 5 times until the Al2O3 powder can settle quickly in 1 to 2 hours and the upper liquid becomes transparent. (13) The obtained sediment was dried in air at 60-80℃ for 8-12 hours to obtain the precursor Al2O3.

3. The method for preparing a nano-alumina based heterojunction catalyst for photocatalytic hydrogen production from water as claimed in claim 2, wherein, The Al2O3 powder in step (11) has a particle size of 100-150 nm and a purity of 99.99%.

4. The method for preparing a nano-alumina-based heterojunction catalyst for photocatalytic water production of hydrogen according to claim 1, characterized in that, The target amount of CdS in step (2) is calculated based on a molar ratio of Al2O3:TiO2:CdS of 2:1:

1.

5. The application of the heterojunction catalyst prepared by the preparation method according to any one of claims 1-4 in photocatalytic hydrogen production from water.

6. Use according to claim 5, characterized in that, Add 30-60 mg of heterojunction catalyst with supported co-catalyst to a reactor containing 80-100 mL of deionized water and 1-4 g of sacrificial agent. Stir magnetically and maintain the temperature of the reactor at room temperature using a circulating water cooling system. Evacuate the reactor and then irradiate it with visible light of wavelength λ>420 nm using a full-spectrum or cutoff filter to perform photocatalytic hydrogen production.

7. Use according to claim 6, characterized in that, The steps for supporting the catalyst are as follows: S1. Add 20-50 mg of the heterojunction catalyst to be tested to 10-40 mL of deionizer, and add 10-20 mL of sacrificial agent and 0.5-1 mL of a catalyst precursor solution with a mass concentration of 1-2 mg / mL. Irradiate with a xenon lamp with full spectrum for 1 hour under magnetic stirring. S2. After irradiation, centrifuge, wash and dry to collect the heterojunction catalyst supported on the catalyst.

8. Use according to claim 7, characterized in that, The cocatalyst precursor in step S1 includes at least one of H2PtCl6 and H2AuCl6.

9. Use according to claim 6, characterized in that, The sacrificial agent is at least one of methanol, Na2S, and Na2SO3.

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