Method for improving selectivity and yield of co2 photo-catalytic reduction to co by single atom orientation based on heterojunction coupling

Abstract

The application discloses a method for improving the selectivity and yield of CO2 in gas-solid phase photocatalytic reduction to CO based on heterojunction coupling single atom orientation. The method comprises the following steps: increasing the TiO2 component in type I heterojunction TiO2 / BiVO4, slowing down the transmission of photo-generated electrons, only meeting the demand of 2-electron reduction product CO, inhibiting the generation of 8-electron reduction product CH4, and realizing that the selectivity of CO generated by gas-solid phase photocatalytic reduction of CO2 reaches 100%; on the basis of the TiO2 / BiVO4-4 heterojunction, a trace amount of Cu single atom is loaded for modification, the excellent adsorption and activation CO2 performance of the Cu single atom is utilized, the yield of CO is further improved, and the 100% selectivity of CO is maintained. Through the method, the type I heterojunction can be coupled with the single atom, the selectivity and yield of CO are simultaneously improved by a two-step method, and the problems of low selectivity and low yield of more C1 / C2+ products obtained by photocatalytic reduction of CO2 can be solved.

Description

Technical Field

[0001] This invention belongs to the field of photocatalysis technology, specifically relating to a method for improving the selectivity and yield of gas-solid phase photocatalytic reduction of CO2 to CO based on heterojunction coupling of single atoms. Background Technology

[0002] Photocatalytic reduction of CO2 can utilize solar energy to convert CO2 into hydrocarbon fuels, mitigating the greenhouse effect caused by large CO2 emissions (Chemical Society Reviews 2020, 49, 2937–3004). In this gas-solid phase system, only CO2 and water vapor participate in the reaction, requiring no solvents, photosensitizers, or sacrificial agents, making it green, clean, economical, and environmentally friendly (Angewandte Chemie 2022, 134, e202206579). However, the gas-solid phase system faces challenges such as low selectivity (coexistence of CO, CH4, and H2) and low product yields (the C=O bond in CO2 is highly stable), limiting its widespread application.

[0003] In the photocatalytic CO2 reaction, CO is a 2-electron reduction product (CO2 + 2e-). - +2H + →CO+H2O), while CH4 is an 8-electron reduction product (CO2+8e). - +8H + →CH4 + 2H2O). Currently, much research focuses on enhancing electron-hole pair separation and accelerating electron transport to further increase CO2 activation (Journal of the American Chemical Society 2019, 141, 13434–13441). However, while accelerating electron transport does benefit CH4 formation, it inevitably leads to CO formation as well. If the electron transport rate can be reduced to meet only the 2-electron requirement, it is hoped that 100% selective CO formation can be achieved. Based on this, compared to S-type or Z-type heterojunctions with fast electron transport, I-type nested heterojunctions with low-speed electron transport will be beneficial for improving CO selectivity. However, this may reduce the CO yield. Summary of the Invention

[0004] The purpose of this invention is to propose a method for improving the selectivity and yield of CO generated from gas-solid phase photocatalytic reduction of CO2 based on heterojunction coupling and single-atom orientation, in order to solve the problems of low product selectivity and low yield in the existing photocatalytic reduction of CO2.

[0005] The present invention provides a method for improving the selectivity and yield of gas-solid phase photocatalytic reduction of CO2 to CO based on heterojunction coupled single atom orientation, comprising the following steps: using type I heterojunction TiO2 / BiVO4 as a photocatalyst, CO2 is reduced to CO through a gas-solid phase photocatalytic reduction reaction.

[0006] In the above method, increasing the TiO2 component in the type I heterojunction TiO2 / BiVO4 can slow down the transport of photogenerated electrons, only satisfying the 2-electron reduction product CO(CO2+2e) - +2H + The demand for →CO+H2O) suppresses the 8-electron reduction product CH4(CO2+8e) - +8H + The generation of CO(CH4+2H2O) achieves 100% CO selectivity in the gas-solid phase photoreduction of CO2.

[0007] According to an embodiment of the present invention, the type I heterojunction TiO2 / BiVO4 is prepared by a hydrothermal method. In the type I heterojunction TiO2 / BiVO4, the molar ratio of TiO2 to BiVO4 is greater than or equal to 4:1, such as 4:1, 5:1, 6:1, 7:1, etc.

[0008] According to an embodiment of the present invention, the gas-solid phase photocatalytic reduction reaction is carried out in a closed photoreactor.

[0009] According to an embodiment of the present invention, the type I heterojunction TiO2 / BiVO4 is pressed into a disc with a diameter of 10-20 mm (specifically 13 mm) and then placed into a reactor.

[0010] According to an embodiment of the present invention, the reactants of the gas-solid phase photocatalytic reduction reaction are only high-purity CO2 (99.999% purity) and water vapor.

[0011] According to an embodiment of the present invention, the water vapor is introduced by high-purity CO2 through water (7 mL) at a flow rate of 80 mL / min.

[0012] According to an embodiment of the present invention, air is removed from the closed reactor under vacuum, and high-purity CO2 (purity 99.999%) is introduced. The CO2 is carried by water vapor through 7 mL of aqueous solution at a flow rate of 25-100 mL / min (specifically 80 mL / min) until the reactor pressure reaches atmospheric pressure.

[0013] According to an embodiment of the present invention, the light source for the gas-solid phase photocatalytic reduction reaction is provided by an Xe lamp (wavelength 200-800nm).

[0014] The present invention provides another method for improving the selectivity and yield of gas-solid phase photocatalytic reduction of CO2 to CO based on heterojunction coupling single atom orientation, comprising the following steps: using a type I heterojunction TiO2 / BiVO4 loaded with trace amounts of Cu single atoms as a photocatalyst, CO2 is reduced to CO through a gas-solid phase photocatalytic reduction reaction.

[0015] The above method, based on the TiO2 / BiVO4 heterojunction, is modified with trace amounts of Cu single atoms. By utilizing the excellent adsorption and activation performance of Cu single atoms for CO2, the yield of CO is further improved, while maintaining 100% selectivity for CO.

[0016] According to an embodiment of the present invention, the type I heterojunction TiO2 / BiVO4 is prepared by a hydrothermal method, wherein the molar ratio of TiO2 to BiVO4 in the type I heterojunction TiO2 / BiVO4 is greater than or equal to 4:1.

[0017] According to an embodiment of the present invention, in the type I heterojunction TiO2 / BiVO4 loaded with trace amounts of Cu single atoms, the Cu single atom content is 0.02-0.5 wt%, specifically 0.13 wt%.

[0018] According to an embodiment of the present invention, in the type I heterojunction TiO2 / BiVO4 loaded with trace amounts of Cu single atoms, the Cu single atoms are prepared by liquid nitrogen cooling combined with photo-irradiation.

[0019] The specific preparation method is as follows: TiO2 / BiVO4 is dispersed in an aqueous solution of copper nitrate and frozen into a block shape with liquid nitrogen; then it is irradiated with an Xe lamp (wavelength 200-800nm) for 5-10 minutes; it is then allowed to melt naturally, centrifuged, and washed with water.

[0020] According to an embodiment of the present invention, the gas-solid phase photocatalytic reduction reaction is carried out in a closed photoreactor.

[0021] According to an embodiment of the present invention, the type I heterojunction TiO2 / BiVO4 loaded with trace amounts of Cu single atoms is pressed into a disc with a diameter of 10-20 mm (specifically 13 mm) and placed into a reactor.

[0022] According to an embodiment of the present invention, the reactants of the gas-solid phase photocatalytic reduction reaction are only high-purity CO2 (99.999% purity) and water vapor.

[0023] According to an embodiment of the present invention, the water vapor is introduced by high-purity CO2 through water (7 mL) at a flow rate of 25-100 mL / min. The volume of water in the container is 7 mL, and the CO2 is introduced into the water vapor through the water-filled container, with the CO2 humidity in the reactor being approximately 50%.

[0024] According to an embodiment of the present invention, air is removed from the closed reactor under vacuum, and high-purity CO2 (purity 99.999%) is introduced. The CO2 is carried by water vapor through 7 mL of aqueous solution at a flow rate of 80 mL / min until the reactor pressure reaches atmospheric pressure.

[0025] According to an embodiment of the present invention, the light source for the gas-solid phase photocatalytic reduction reaction is provided by an Xe lamp (wavelength 200-800nm).

[0026] According to an embodiment of the present invention, a built-in electric field exists in the type I heterojunction TiO2 / BiVO4, with the direction being TiO2 pointing towards BiVO4.

[0027] According to an embodiment of the present invention, a type I heterojunction TiO2 / BiVO4 is selected, and the TiO2 component is increased to slow down the photogenerated electron transport, which is revealed by physicochemical techniques. The physicochemical techniques include ultraviolet-visible diffuse reflectance spectroscopy, electrochemical photocurrent response, electrochemical impedance spectroscopy, and fluorescence spectroscopy.

[0028] Compared with the prior art, the present invention has the following beneficial effects:

[0029] (1) Compared with Z-type or S-type heterojunctions, I-type heterojunctions, which have poorer optical properties, have been developed and utilized. By increasing the TiO2 component in TiO2 / BiVO4, electron transport is further slowed down, and 2-electron product CO is selectively generated, ultimately achieving 100% selectivity for CO.

[0030] (2) Based on TiO2 / BiVO4-4, the CO yield was further improved by loading trace amounts of Cu single-atom modification, while maintaining 100% selectivity for CO. The improved yield is due to the excellent adsorption and activation performance of Cu single atoms for CO2, and the maintenance of 100% selectivity is due to the fact that Cu single-atom modification did not accelerate the low-speed electron transport of the support TiO2 / BiVO4-4.

[0031] (3) The combination of heterojunction and single atom fully leverages their respective advantages to achieve simultaneous improvement in the selectivity and yield of photoreduced CO2 products. Attached Figure Description

[0032] Figure 1 This is an aberration-corrected transmission electron microscope image of the TiO2 / BiVO4-4 heterojunction prepared in Example 1;

[0033] Figure 2 These are the UV-Vis diffuse reflectance spectra of the TiO2 / BiVO4 heterojunction prepared in Example 1 and the material prepared in Comparative Example 1.

[0034] Figure 3 These are the electrochemical photocurrent response diagrams of the TiO2 / BiVO4 heterojunction prepared in Example 1 and the material prepared in Comparative Example 1.

[0035] Figure 4 These are the electrochemical impedance spectroscopy diagrams of the TiO2 / BiVO4 heterojunction prepared in Example 1 and the material prepared in Comparative Example 1.

[0036] Figure 5 The fluorescence spectra of the TiO2 / BiVO4 heterojunction prepared in Example 1 and the material prepared in Comparative Example 1 are shown.

[0037] Figure 6 The yield and selectivity of the photocatalytic CO2 reduction products of the TiO2 / BiVO4 heterojunction obtained in Example 2 are shown.

[0038] Figure 7 This is a spherical aberration corrected transmission electron microscope image of the TiO2 / BiVO4-4-loaded Cu single atoms prepared in Example 3;

[0039] Figure 8 The electrochemical photocurrent response diagrams are for the TiO2 / BiVO4 heterojunction prepared in Example 1 and the TiO2 / BiVO4-4 loaded with Cu single atoms prepared in Example 3.

[0040] Figure 9 The electrochemical impedance spectroscopy diagrams are of the TiO2 / BiVO4 heterojunction prepared in Example 1 and the TiO2 / BiVO4-4 supported Cu single atoms prepared in Example 3.

[0041] Figure 10 The yield of CO produced by photocatalytic reduction of CO2 using different materials prepared in Example 1, Example 3 and Comparative Example 2 is respectively.

[0042] Figure 11 This is a transmission electron microscope (TEM) image of the TiO2 / BiVO4-4-loaded Cu nanoparticles prepared in Example 3, with spherical aberration correction.

[0043] Figure 12 This is a schematic diagram illustrating the principle of efficient photocatalytic reduction of CO2 to a single product CO by a heterojunction coupled single-atom catalyst. Detailed Implementation

[0044] The present invention will now be described in further detail with reference to specific embodiments. The given embodiments are merely illustrative of the invention and not intended to limit its scope. The embodiments provided below can serve as a guide for further improvements by those skilled in the art and do not constitute a limitation on the invention in any way.

[0045] Unless otherwise specified, the experimental methods used in the following examples are conventional methods, performed according to the techniques or conditions described in the literature in this field or according to the product instructions. Unless otherwise specified, the materials and reagents used in the following examples are commercially available.

[0046] Example 1

[0047] Type I heterojunction TiO2 / BiVO4 was prepared by adjusting the molar ratio of TiO2 to BiVO4 to 0.5, 1, 3 and 4.

[0048] (1) Add 0.485g Bi(NO3)3·5H2O to 40mL of ultrapure water and stir for 10min to prepare solution A; then add 0.117g NH4VO3 and 1.2g urea to 32mL of ultrapure water and stir for 10min to prepare solution B; under stirring conditions, slowly add solution A to solution B, then add a certain amount of TiO2 (the molar ratio of TiO2 to BiVO4 is X, X = 0.5, 1, 3, 4) and continue stirring for 60min before transferring to a 100mL hydrothermal reactor and hydrothermating at 90℃ for 12 hours. After naturally cooling to room temperature, centrifuge to obtain the precipitate, wash three times with ultrapure water, dry at 60℃ overnight, and grind to obtain solid powder.

[0049] (2) The powder was reduced under pure H2 conditions for 2 hours at a reduction temperature of 400℃ and a heating rate of 2℃ / min to finally obtain the TiO2 / BiVO4 heterojunction catalyst.

[0050] A catalyst with a TiO2 to BiVO4 molar ratio of 0.5 is denoted as TiO2 / BiVO4-0.5;

[0051] A catalyst with a molar ratio of TiO2 to BiVO4 of 1 is denoted as TiO2 / BiVO4-1;

[0052] A catalyst with a molar ratio of TiO2 to BiVO4 of 3 is denoted as TiO2 / BiVO4-3;

[0053] A catalyst with a TiO2 to BiVO4 molar ratio of 4 is denoted as TiO2 / BiVO4-4.

[0054] Figure 1 This is a spherical aberration-corrected transmission electron microscope (TEM) image of the TiO2 / BiVO4-4 heterojunction prepared according to Example 1 of the present invention. The heterojunction interface between TiO2 and BiVO4 is clearly visible in the image.

[0055] Example 2

[0056] The TiO2 / BiVO4 heterojunction prepared in Example 1 was used for gas-solid phase photocatalytic reduction of CO2.

[0057] 30 mg of TiO2 / BiVO4 heterojunction was molded into 13 mm diameter discs in a mold and then placed in a sealed photocatalytic reactor. Air was removed from the reactor under vacuum. High-purity CO2 (99.999% purity) was introduced, with water vapor carried by 7 mL of aqueous solution at a flow rate of 80 mL / min, until the reactor pressure reached atmospheric pressure. The Xe lamp was then turned on to begin the photocatalytic reduction of CO2.

[0058] Figure 6 The yield and selectivity of the photocatalytic CO2 reduction products of the TiO2 / BiVO4 heterojunction obtained according to Example 2 of the present invention are described. Figure 6 a and b show that the reduction products are CO and CH4. With the increase of TiO2 content, the yield of CO product increases, while the corresponding yield of CH4 decreases. Figure 6 c clearly shows that increasing the TiO2 component can improve the CO selectivity (reaction time 5 hours). When the molar ratio of TiO2 to BiVO4 is 4, the CO selectivity reaches 100%.

[0059] Example 3

[0060] Prepare Cu single-atom modified catalyst based on TiO2 / BiVO4-4 (prepared in Example 1).

[0061] (1) Disperse TiO2 / BiVO4-4 powder in 150mL of ultrapure water, stir for 1 hour, and add a certain amount of Cu(NO3)2·3H2O aqueous solution (Cu loading is 0.13wt%).

[0062] (2) Transfer the suspension to liquid nitrogen and freeze it into a block, then irradiate it with Xe lamp for 5 minutes.

[0063] (3) Melt naturally at room temperature, centrifuge, wash with ultrapure water, freeze dry, and finally obtain Cu1-TiO2 / BiVO4-4.

[0064] Figure 7 This is an aberration-corrected transmission electron microscope (TEM) image of Cu1-TiO2 / BiVO4-4 prepared according to Example 3 of the present invention. It can be clearly seen from the image that Cu exists as single atoms dispersed on the TiO2 / BiVO4-4 heterojunction.

[0065] Example 4

[0066] Cu1-TiO2 / BiVO4-4 prepared in Example 3 was used for gas-solid phase photocatalytic reduction of CO2.

[0067] 30 mg of Cu1-TiO2 / BiVO4-4 was molded into 13 mm diameter discs in a mold and then placed in a sealed photocatalytic reactor. Air was removed from the reactor under vacuum. High-purity CO2 was introduced, with water vapor carried by 7 mL of aqueous solution at a flow rate of 80 mL / min, until the reactor pressure reached atmospheric pressure. The Xe lamp was then turned on to begin the photocatalytic reduction of CO2.

[0068] Figure 11 The yields of CO produced by photocatalytic reduction of CO2 to CO using the catalysts obtained in Examples 2 and 4 of this invention are respectively. Figure 11 The results showed that compared to TiO2 / BiVO4-4 (4.53 μmol·g), cat -1 ·h -1 The CO yield obtained (CO yield = CO concentration * volume / catalyst dosage / reaction time), Cu1-TiO2 / BiVO4-4 (17.33 μmol·g) cat -1 ·h -1 The CO yield increased by 3.82 times. Furthermore, the CO selectivity obtained from Cu1-TiO2 / BiVO4-4 remained at 100%, indicating that Cu single-atom modification failed to accelerate electron transport on the TiO2 / BiVO4-4 support.

[0069] Comparative Example 1

[0070] (1) Preparation of TiO2 catalyst:

[0071] Add 8 mL of 30% hydrogen peroxide and 50 mL of 10 M sodium hydroxide aqueous solution dropwise to 5 mL of tetrabutyl titanate, and stir for 20 min. Then, hydrothermally heat the suspension at 180 °C for 19 hours. Allow it to cool naturally to room temperature, centrifuge, and wash three times with ultrapure water. Then, soak it in hydrochloric acid aqueous solution (0.1 M) for 12 hours, centrifuge, wash three times with ultrapure water, dry at 60 °C overnight, and grind to obtain a solid powder. Calcine the powder in a muffle furnace at 550 °C for 2 hours.

[0072] The powder was stirred in 72 mL of ultrapure water for 60 min, then transferred to a 100 mL hydrothermal reactor and hydrothermated at 90 °C for 12 h. After naturally cooling to room temperature, the precipitate was obtained by centrifugation, washed three times with ultrapure water, dried overnight at 60 °C, and then ground to obtain a solid powder.

[0073] The powder was reduced under pure H2 conditions for 2 hours at a reduction temperature of 400℃ and a heating rate of 2℃ / min to finally obtain the TiO2 catalyst.

[0074] (2) Preparation of BiVO4 catalyst:

[0075] 0.485 g Bi(NO3)3·5H2O was added to 40 mL of ultrapure water and stirred for 10 min to prepare solution A. Then, 0.117 g NH4VO3 and 1.2 g urea were added to 32 mL of ultrapure water and stirred for 10 min to prepare solution B. Solution A was slowly added dropwise to solution B under stirring, and the mixture was stirred continuously for 60 min. The solution was then transferred to a 100 mL hydrothermal reactor and hydrothermally heated at 90 °C for 12 hours. After naturally cooling to room temperature, the precipitate was obtained by centrifugation, washed three times with ultrapure water, dried overnight at 60 °C, and ground to obtain a solid powder.

[0076] The powder was reduced under pure H2 conditions for 2 hours at a reduction temperature of 400℃ and a heating rate of 2℃ / min to finally obtain the BiVO4 catalyst.

[0077] Comparative Example 2

[0078] Preparation of Cu particle catalysts based on TiO2 / BiVO4-4:

[0079] A certain amount of Cu(NO3)2·3H2O aqueous solution (Cu loading was 0.48 wt%) was added dropwise to TiO2 / BiVO4-4 (a type I heterojunction TiO2 / BiVO4 with a molar ratio of TiO2 to BiVO4 of 4 prepared in Example 1), and allowed to stand overnight. After centrifugation and washing with ultrapure water three times, the mixture was dried at 60°C overnight and ground to obtain the Cu-TiO2 / BiVO4-4 catalyst.

[0080] Figure 11 This is a transmission electron microscope (TEM) image of the TiO2 / BiVO4-4-loaded Cu nanoparticles prepared in Example 3, with spherical aberration correction.

[0081] Figure 2 These are the ultraviolet-visible diffuse reflectance spectra of different materials prepared according to Example 1 and Comparative Example 1 of the present invention. The results show that TiO2 / BiVO4 exhibits photoresponse in the ultraviolet-visible region. The photoresponse in the visible region is mainly attributed to BiVO4. Increasing the TiO2 content weakens the response of TiO2 / BiVO4 to visible light, thereby reducing the number of photogenerated electrons and slowing down electron transport to some extent.

[0082] Figure 3 These are electrochemical photocurrent response diagrams of different materials prepared according to Example 1 and Comparative Example 1 of the present invention. The results show that BiVO4 and TiO2 / BiVO4 have good photocurrent responses, while the photocurrent response of TiO2 / BiVO4 weakens with increasing TiO2 content. The heterojunction TiO2 / BiVO4-4 exhibits the weakest photocurrent response, directly reflecting the slowest electron transport.

[0083] Figure 4These are electrochemical impedance spectroscopy (EIS) diagrams of different materials prepared according to Example 1 and Comparative Example 1 of the present invention. The results show that BiVO4 has the smallest Nyquist high-frequency radius, corresponding to the smallest impedance; as the TiO2 content increases, the high-frequency radius of TiO2 / BiVO4 becomes larger and larger, and the high-frequency radius of TiO2 / BiVO4-4 is relatively the largest, corresponding to the relatively largest impedance, directly reflecting the slowest electron transport.

[0084] Figure 5 These are fluorescence spectra of different materials prepared according to Example 1 and Comparative Example 1 of the present invention. The results show that as the TiO2 content increases, the fluorescence intensity of TiO2 / BiVO4 becomes stronger and stronger. The fluorescence intensity of TiO2 / BiVO4-4 in the heterojunction is the strongest, corresponding to the electron-hole pair recombination with the highest relative probability, which directly reflects the slowest electron transport.

[0085] Figure 8 These are electrochemical photocurrent response diagrams of different materials prepared according to Examples 1 and 3 of the present invention. The results show that, compared with TiO2 / BiVO4-4, the photocurrent response of Cu1-TiO2 / BiVO4-4 modified with Cu single atoms is weakened, indicating slower electron transport.

[0086] Figure 9 These are electrochemical impedance spectroscopy (EIS) diagrams of different materials prepared according to Examples 1 and 3 of the present invention. The results show that, compared to TiO2 / BiVO4-4, Cu1-TiO2 / BiVO4-4 modified with Cu single atoms has a relatively larger high-frequency radius of electrochemical Nyquist impedance, corresponding to a relatively larger impedance, which directly reflects slower electron transport.

[0087] Figure 10 This describes the photocatalytic reduction of CO2 to CO yield using different materials prepared according to Examples 1, 3, and Comparative Example 2, as well as the commercially available catalyst P25 TiO2. The results show that the yield of Cu1-TiO2 / BiVO4-4 modified with a single Cu atom is 17.33 μmol·g⁻¹. cat -1 ·h -1 This further increased the TiO2 / BiVO4-4 ratio by 4.53 μmol·g. cat -1 ·h -1 The CO yield of Cu1-TiO2 / BiVO4-4 was significantly higher than that of Cu nanoparticles Cu-TiO2 / BiVO4-4 (2.10 μmol·g). cat -1 ·h -1The CO yield is likely due to the excellent adsorption and activation performance of Cu single atoms for CO2, while Cu nanoparticles, as electron-hole pairs, have a negative impact on the composite.

[0088] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above descriptions are merely specific embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for improving the selectivity and yield of gas-solid phase photocatalytic reduction of CO2 to CO based on heterojunction coupling of single atoms, comprising the following steps: With a trace amount of Cu single atoms The heterojunction TiO2 / BiVO4 is used as a photocatalyst to reduce CO2 to CO via a gas-solid phase photocatalytic reduction reaction.

2. The method according to claim 1, characterized in that: The loading of trace Cu single atoms In the heterojunction TiO2 / BiVO4, the Cu single atom content is 0.02-0.5wt%.

3. The method according to claim 1 or 2, characterized in that: The The heterojunction TiO2 / BiVO4 was prepared by a hydrothermal method. In the TiO2 / BiVO4 heterojunction, the molar ratio of TiO2 to BiVO4 is greater than or equal to 4:

1.

4. The method according to claim 1 or 2, characterized in that: The loading of trace Cu single atoms In the TiO2 / BiVO4 heterojunction, Cu single atoms were prepared by liquid nitrogen cooling combined with photo-irradiation.

5. The method according to claim 4, characterized in that: The loading of trace Cu single atoms The preparation method of Cu single atoms in TiO2 / BiVO4 heterojunction includes the following steps: dispersing TiO2 / BiVO4 in copper nitrate aqueous solution, freezing it into a block shape with liquid nitrogen; then irradiating it with Xe lamp for 5-10 min; melting it naturally, centrifuging it, and washing it with water.

6. The method according to claim 1 or 2, characterized in that: The gas-solid phase photocatalytic reduction reaction is carried out in a closed photoreactor.

7. The method according to claim 1 or 2, characterized in that: The The heterojunction TiO2 / BiVO4 is compressed into discs with a diameter of 10-20 mm and then placed into the reactor. Or, the loading of trace Cu single atoms The heterojunction TiO2 / BiVO4 is compressed into discs with a diameter of 10-20 mm and then placed into the reactor.

8. The method according to claim 1 or 2, characterized in that: The reactants of the gas-solid phase photocatalytic reduction reaction are only high-purity CO2 and water vapor; Alternatively, the light source for the gas-solid phase photocatalytic reduction reaction may be provided by an Xe lamp.

9. The method according to claim 8, characterized in that: The water vapor is introduced by high-purity CO2 through water at a flow rate of 25-100 ml / min.

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