A method for enhancing gas-phase photocatalytic CO2 reduction performance based on interdigitated electrodes

Abstract

The present invention discloses a method for enhancing the performance of gas-phase photocatalytic CO2 reduction using interdigitated electrodes. First, a photocatalyst and a binder are mixed and loaded onto interdigitated electrodes to assemble a photocatalyst interdigitated electrode film. Then, the photocatalyst interdigitated electrode film is placed in a container filled with CO2, and a small external voltage is applied to the photocatalyst interdigitated electrode film. This causes the micro-spacing between the interdigitated electrodes to form a high-intensity electric field, promoting the separation of photogenerated carriers. This simultaneously causes the Helmholtz layer to restructure, shifting the conduction band upward, raising the reduction potential of the photocatalyst to activate CO2, thereby improving the photocatalytic CO2 reduction performance. The method of the present invention overcomes the inherent defects of existing photocatalysts, such as the low theoretical reduction potential of the conduction band. Furthermore, by adjusting the voltage applied to the photocatalytic material or the interdigitated electrode spacing, the photocatalytic CO2 reduction performance of the catalyst can be significantly improved, achieving efficient catalytic reduction of CO2 to alkane-type energy substances.

Description

Technical Field

[0001] The present invention belongs to the technical field of gas-phase photoelectrocatalysis, and specifically relates to a method for enhancing gas-phase photocatalytic CO2 reduction performance based on interdigitated electrodes. Background Art

[0002] The current concentration of CO2 in the atmosphere is around 400 ppm. If its emissions are not restricted, it is expected to reach over 1000 ppm by 2100, which will cause the Earth's sea level and average temperature to rise simultaneously. Therefore, humanity urgently needs to develop advanced technologies that can reduce the concentration of CO2 in the atmosphere and convert CO2 into various useful high-value products to achieve a "closed-loop" carbon cycle. The CO2 catalytic conversion technologies currently under development include thermal catalysis, electrocatalysis, photocatalysis and other technical means. Among them, photocatalytic CO2 reduction technology mimics photosynthesis, using solar energy and photocatalysts to catalytically convert CO2 and H2O into high-value-added fuels and chemicals. It has the advantages of low carbon emissions, green and clean, low cost, safety and stability, and meets the development needs of building a resource-saving and environmentally friendly society.

[0003] Since the linear symmetric CO2 molecule is very stable in thermodynamics, its C=O bond energy is as high as 750 kJ / mol, and its theoretical reduction potential is as high as -1.9V (vs. NHE), the conduction band of most photocatalysts cannot reach the theoretical potential of CO2 reduction. On the other hand, in the photocatalytic reaction dominated by carrier transport, the ability of semiconductor materials to absorb photons is the key to their ability to stimulate the generation of photogenerated electrons and holes (e - -h + ) is a prerequisite for photocatalytic reactions. However, before migrating to the material surface to participate in the reaction, most electrons and holes will recombine in the form of radiation or combine under the influence of Coulomb forces to form excitons (ranging from a few picoseconds to tens of nanoseconds). In other words, the recombination rate of photogenerated electron-hole pairs in the bulk phase is much higher than the rate at which they migrate from the bulk phase to the interface to participate in the reaction. Therefore, increasing the conduction band reduction potential of the photocatalyst and overcoming the Coulomb force between photogenerated electron-hole pairs in the bulk phase to achieve their effective spatial separation are the keys to further improving photocatalytic efficiency.

[0004] Since photogenerated electrons and holes have opposite electrical properties, applying an external electric field is the most effective and direct method to separate electrons and holes. Applying an electric field on a photocatalyst can drive photogenerated carriers to move in opposite directions, increase the charge transfer rate of the carriers and reduce their recombination rate. Chinese patent CN101785971A discloses a photoelectrocatalytic device for degrading gaseous organic pollutants, which can significantly improve the performance of photocatalytic degradation of gaseous organic pollutants when a voltage of 0.2V is applied. However, when the voltage is further increased, the performance decreases instead, and the applied voltage and photocatalytic performance do not show a positive correlation. This is mainly because when the voltage is increased to a certain level, the Helmholtz layer of the material will be reconstructed under the action of a strong electric field, causing the conduction band to move upward, resulting in a further improvement in the reduction performance of the photocatalysis and a reduction in the oxidation ability of the valence band holes. Summary of the Invention

[0005] In response to the inherent defects of existing photocatalysts, such as the difficulty of meeting the theoretical potential for CO2 reduction and the high recombination rate of photogenerated carriers, and the need to improve their photocatalytic CO2 reduction performance, the present invention provides a method for enhancing the gas-phase photocatalytic CO2 reduction performance based on interdigitated electrodes. The present invention assembles a photocatalyst film by mixing a photocatalytic material with a binder and loading it onto interdigitated electrodes. Under the condition of applying a small external voltage, a high-intensity electric field is formed at the micro-spacing of the interdigitated electrodes to promote the separation of photogenerated carriers. At the same time, the Helmholtz layer is reconstructed, causing the conduction band to shift upward, raising the reduction potential of the photocatalyst to activate CO2, thereby improving the photocatalytic CO2 reduction performance. This method can significantly improve the photocatalytic CO2 reduction performance of the catalyst by adjusting the voltage applied to the two ends of the photocatalytic material or the interdigitated electrode spacing, thereby achieving efficient catalytic reduction of CO2 to alkane-type energy substances.

[0006] In order to achieve the above object, the technical solution adopted by the present invention is as follows:

[0007] A method for enhancing the gas-phase photocatalytic CO2 reduction performance based on interdigitated electrodes comprises the following steps: first, a photocatalyst and an adhesive are mixed and loaded onto interdigitated electrodes to assemble a photocatalyst interdigitated electrode film; then, the photocatalyst interdigitated electrode film is placed in a container filled with CO2, and a small external voltage is applied to the photocatalyst interdigitated electrode film, so that a high-intensity electric field is formed at the micro-spacing of the interdigitated electrodes to promote the separation of photogenerated carriers, while causing the Helmholtz layer to reconstruct and shift the conduction band upward, thereby increasing the reduction potential of the photocatalyst to activate CO2, thereby improving the photocatalytic CO2 reduction performance.

[0008] As a preferred improvement of the present invention: the interdigital electrodes are straight-line interdigital electrodes, wavy interdigital electrodes or arc-shaped interdigital electrodes.

[0009] As a preferred improvement of the present invention: the photocatalyst is TiO2, WO3, ZnO, BiVO4 or g-C3N4.

[0010] As a preferred improvement of the present invention: the adhesive is polyvinyl alcohol or polyethylene glycol.

[0011] As a preferred improvement of the present invention: the mixing ratio of the photocatalyst and the adhesive is (6:4) to (9:1).

[0012] As a preferred improvement of the present invention: the electrode spacing of the interdigitated electrodes is 1 to 500 μm.

[0013] As a preferred improvement of the present invention: the voltage of the applied small external voltage is 0.1 to 3.0V.

[0014] Advantages of the present invention:

[0015] 1. The present invention only needs to provide a relatively low voltage of 0.1 to 3.0 V to form a high-intensity electric field greater than 1000 V / cm, which can reconstruct the Helmholtz layer of the photocatalyst and shift the conduction band upward, enabling most photocatalytic materials that originally could not catalyze CO2 to achieve efficient catalytic CO2 reduction.

[0016] 2. The present invention forms a high-intensity electric field by applying a small external voltage to the interdigitated electrodes to form a micro-spacing, thereby driving the directional migration of photogenerated carriers and promoting the separation of photogenerated carriers; compared with photocatalysis, it exhibits higher photogenerated electron-hole separation efficiency and catalytic activity.

[0017] 3. The photoelectrocatalytic assembly used in the present invention has a simple assembly process and is applicable to a variety of photocatalysts; and in the actual application of gas-phase photoelectrocatalysis, the photocatalytic material has excellent reusability and durability, and therefore can be widely used in practice. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 Schematic diagram of the structure of the photocatalytic interdigitated electrode film;

[0019] Figure 2 This is the volt-ampere characteristic curve of the TiO2 photocatalytic interdigitated electrode film;

[0020] Figure 3 The photoluminescence spectra of TiO2 photocatalytic interdigitated electrode films under different voltage conditions;

[0021] Figure 4 The performance diagram of TiO2 photocatalytic interdigitated electrode film for gas-phase photoelectrocatalytic CO2 reduction at 0V and 1.0V respectively;

[0022] Figure 5This is a stability test diagram of the photoelectrocatalytic CO2 reduction reaction of TiO2 photocatalytic interdigitated electrode film under 1.0V conditions.

[0023] Figure 1 Middle: insulating ceramic substrate 1, photocatalyst 2, interdigitated electrode 3. Implementation Method

[0024] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely for the purpose of explaining the present invention and are not intended to limit the present invention. In addition, the technical features involved in the various embodiments of the present invention described below may be combined with each other as long as they do not conflict with each other.

[0025] The present invention provides a method for enhancing the gas-phase photocatalytic CO2 reduction performance based on interdigitated electrodes: first, a photocatalyst and a binder are mixed and loaded onto interdigitated electrodes to assemble a photocatalyst interdigitated electrode film; then, the photocatalyst interdigitated electrode film is placed in a container filled with CO2, and a small external voltage is applied to the photocatalyst interdigitated electrode film, so that the micro-spacing of the interdigitated electrodes forms a high-intensity electric field that promotes the separation of photogenerated carriers, while causing the Helmholtz layer to reconstruct and shift the conduction band upward, thereby increasing the reduction potential of the photocatalyst to activate CO2, thereby improving the photocatalytic CO2 reduction performance. The specific steps are:

[0026] First, a polyvinyl alcohol or polyethylene glycol binder is dissolved in an ethanol-water solution. The photocatalyst (TiO2, WO3, ZnO, BiVO4, or g-C3N4) and the binder are then thoroughly mixed at a ratio of 6:4 to 9:1. The mixture is then applied to linear, wavy, or arc-shaped interdigitated electrodes with a spacing of 1 to 500 μm. The electrodes are then calcined in a muffle furnace at 450°C for 2 hours to form a photocatalyst interdigitated electrode film.

[0027] The photocatalytic interdigitated electrode film assembled according to the above method was applied to gas-phase photoelectrocatalytic CO2 reduction. Specifically, the photocatalytic interdigitated electrode film was placed in a container filled with CO2 and a potential of 0.1V to 3.0V was applied to photocatalytically reduce the CO2. After a period of reaction, a sample was taken and measured by gas chromatography.

[0028] The following are examples: Example

[0029] A method for enhancing gas-phase photocatalytic CO2 reduction performance based on interdigitated electrodes comprises the following steps:

[0030] (1) Assembling photocatalyst interdigitated electrode thin films

[0031] First, 0.3g of polyvinyl alcohol binder was dissolved in 5ml of ethanol-water solution. Then, 0.7g of TiO2 and the binder were thoroughly mixed at a ratio of 7:3. The mixture was then applied to linear interdigitated electrodes with a spacing of 100μm and calcined in a muffle furnace at 450°C for 2 hours to obtain a TiO2 photocatalyst interdigitated electrode film.

[0032] (2) Photocatalytic interdigitated electrode thin film for gas-phase photoelectrocatalytic reduction of CO2

[0033] The TiO2 photocatalyst interdigitated electrode film obtained in step (1) is placed in a container filled with CO2, and a potential of 1.0 V is applied to perform photocatalytic reduction of CO2. After the reaction for 1 hour, a sample is taken out and measured by gas chromatography.

[0034] The results of the embodiment are analyzed:

[0035] (1) Schematic diagram of the structure of the photocatalyst interdigitated electrode film

[0036] from Figure 1 As shown, the photocatalyst interdigitated electrode film consists of an insulating ceramic substrate 1, a photocatalyst 2, and interdigitated electrodes 3. Based on the micro-pitch structure (1-100μm) of the interdigitated electrodes, an electric field-enhanced photocatalytic system is constructed. A high electric field strength can be generated under the application of a small external voltage. The electric field strength can reach up to 1000V / cm without the need for a counter electrode or electrolyte. This drives (pulls) the separation and migration of photogenerated carriers, thereby increasing the number of carriers reaching the catalyst interface to participate in the reaction, significantly improving the photoelectric performance of the catalyst.

[0037] (2) I-V characteristic curve of TiO2 photocatalyst interdigitated electrode film

[0038] like Figure 2 As shown in Figure 2, the photoelectric performance of the TiO2 photocatalyst interdigitated electrode thin film was measured using the voltammetric method. The voltammetric test range was +3.0 to -3.0. As the applied voltage increased, the ratio of the photocurrent to the dark current through the electrode film also increased, reaching a maximum of 107 times. The net difference between the photocurrent and the dark current represents the charge flux of photogenerated carriers. Therefore, under the action of the electric field, more photogenerated carriers migrate to the catalyst surface to participate in the CO2 conversion reaction.

[0039] (3) Photoluminescence spectra of TiO2 photocatalyst interdigitated electrode films under different voltage conditions

[0040] like Figure 3As shown in the photoluminescence spectrum, it is clear that the luminescence intensity is very high when no voltage is applied, indicating a high electron-hole recombination rate and few electrons and holes actually contributing to the photocatalytic reaction. However, when a small voltage is applied to the TiO2 photocatalytic interdigitated electrode film, the luminescence intensity weakens and further decreases with increasing applied voltage, indicating a decrease in the recombination efficiency of electrons and holes under the action of the electric field. In addition, the peak center of the photoluminescence signal continues to blueshift, indicating that the conduction band position continues to shift upward, and the theoretical reduction potential continues to increase, which is more conducive to CO2 photocatalytic reduction.

[0041] (4) Performance diagram of TiO2 photocatalyst interdigitated electrode film for gas-phase photoelectrocatalytic CO2 reduction at 0V and 1.0V

[0042] The TiO2 photocatalytic interdigitated electrode film was applied to gas-phase photoelectrocatalytic CO2 reduction. Specifically, the film was placed in a container filled with CO2 and subjected to potentials of 0V and 1.0V, respectively, for photocatalytic CO2 reduction. After a period of reaction, samples were taken and measured by gas chromatography.

[0043] like Figure 4 As shown in the figure, in the photocatalytic system, the products of CO2 reduction are mainly CH4 and C2H6, with yields of 48.4 and 16.1 μmol g -1 h -1 When a voltage of 1.0 V was applied to the TiO2 photocatalyst interdigitated electrode film, the yields of CH4 and C2H6 increased to 274.3 and 32.7 μmol g, respectively. -1 h -1 , and the generation of C3H8 was also detected with a yield of 10.4 μmol g -1 h -1 The results show that the catalytic effect is greatly improved after applying a certain bias voltage, and the photocatalytic CO2 reduction performance can be improved by up to 5 times, and an additional multi-electron product C3H8 is produced. These results indicate that the application of a small external voltage condition causes the micro-spacing of the interdigitated electrodes to form a high-intensity electric field, which promotes the separation of photogenerated carriers. At the same time, it causes the Helmholtz layer to reconstruct, causing the conduction band to shift upward, increasing the reduction potential of the photocatalyst to activate CO2, significantly improving the catalyst's photocatalytic CO2 reduction performance, and promoting the generation of higher-value multi-carbon products.

[0044] (5) Stability test diagram of the photoelectrocatalytic CO2 reduction reaction of TiO2 photocatalyst interdigitated electrode film at 1.0V

[0045] like Figure 5As shown, the TiO2 photocatalyst interdigitated electrode film was placed in a container filled with CO2, with a potential of 1.0V applied for 1 hour, and the CO2 reduction to alkane substances was tested for 5 cycles. There was no obvious attenuation in the production of CH4, C2H6, and C3H8, indicating that the electrochemical self-doped TiO2 nanotube-based material gas-phase photoelectrocatalysis has excellent stability and durability for CO2 reduction.

[0046] From the above analysis, it can be seen that the gas-phase photoelectrocatalytic CO2 reduction system constructed based on the TiO2 photocatalyst interdigitated electrode film in the method of this embodiment has high catalytic performance and can also maintain the excellent stability and durability of the material, which is more conducive to practical application. Example

[0047] A method for enhancing gas-phase photocatalytic CO2 reduction performance based on interdigitated electrodes comprises the following steps:

[0048] (1) Assembling photocatalyst interdigitated electrode thin films

[0049] First, 0.4g of polyvinyl alcohol was dissolved in 5ml of ethanol-water solution. Then, 0.6g of ZnO and a binder were thoroughly mixed at a ratio of 6:4. The mixture was then applied to arc-shaped interdigitated electrodes with a spacing of 200μm. The electrodes were then calcined in a muffle furnace at 450°C for 2 hours to obtain a ZnO photocatalyst interdigitated electrode film.

[0050] (2) Photocatalytic interdigitated electrode thin film for gas-phase photoelectrocatalytic reduction of CO2

[0051] The ZnO photocatalyst interdigitated electrode film obtained in step (1) is placed in a container filled with CO2, and a potential of 1.5 V is applied to perform photocatalytic reduction of CO2. After the reaction for 1 hour, a sample is taken out and measured by gas chromatography. Example

[0052] A method for enhancing gas-phase photocatalytic CO2 reduction performance based on interdigitated electrodes comprises the following steps:

[0053] (1) Assembling photocatalyst interdigitated electrode thin films

[0054] First, 0.2g of polyethylene glycol was dissolved in 5ml of ethanol-water solution. Then, 0.8g of WO3 and a binder were thoroughly mixed at a ratio of 8:2. The mixture was then applied to linear interdigitated electrodes with a spacing of 50μm and calcined in a muffle furnace at 450°C for 2 hours to obtain a WO3 photocatalyst interdigitated electrode film.

[0055] (2) Photocatalytic interdigitated electrode thin film for gas-phase photoelectrocatalytic reduction of CO2

[0056] The WO3 photocatalyst interdigitated electrode film obtained in step (1) is placed in a container filled with CO2, and a potential of 0.5 V is applied to perform photocatalytic reduction of CO2. After the reaction for 1 hour, a sample is taken out and measured by gas chromatography. Example

[0057] A method for enhancing gas-phase photocatalytic CO2 reduction performance based on interdigitated electrodes comprises the following steps:

[0058] (1) Assembling photocatalyst interdigitated electrode thin films

[0059] First, 0.4g of polyethylene glycol was dissolved in 5ml of ethanol-water solution. Then, 0.6g of BiVO4 and a binder were thoroughly mixed at a ratio of 6:4. The mixture was then applied to a wavy interdigitated electrode with a spacing of 300μm. The electrode was then calcined in a muffle furnace at 450°C for 2 hours to obtain a BiVO4 photocatalyst interdigitated electrode film.

[0060] (2) Photocatalytic interdigitated electrode thin film for gas-phase photoelectrocatalytic reduction of CO2

[0061] The BiVO4 photocatalyst interdigitated electrode film obtained in step (1) was placed in a container filled with CO2, and a potential of 1.5 V was applied to perform photocatalytic reduction of CO2. After the reaction for 1 hour, the sample was taken out and measured by gas chromatography. Example

[0062] A method for enhancing gas-phase photocatalytic CO2 reduction performance based on interdigitated electrodes comprises the following steps:

[0063] (1) Assembling photocatalyst interdigitated electrode thin films

[0064] First, 0.3g of polyvinyl alcohol was dissolved in 5ml of ethanol-water solution. Then, 0.7g of g-C3N4 and a binder were thoroughly mixed at a ratio of 7:3. The mixture was then applied to arc-shaped interdigitated electrodes with a spacing of 200μm and calcined in a muffle furnace at 450°C for 2 hours to obtain a g-C3N4 photocatalyst interdigitated electrode film.

[0065] (2) Photocatalytic interdigitated electrode thin film for gas-phase photoelectrocatalytic reduction of CO2

[0066] The g-C3N4 photocatalyst interdigitated electrode film obtained in step (1) was placed in a container filled with CO2, and a potential of 1.0 V was applied to perform photocatalytic reduction of CO2. After the reaction for 1 hour, the sample was taken out and measured by gas chromatography. Example

[0067] A method for enhancing gas-phase photocatalytic CO2 reduction performance based on interdigitated electrodes comprises the following steps:

[0068] (1) Assembling photocatalyst interdigitated electrode thin films

[0069] First, 0.2g of polyvinyl alcohol was dissolved in 5ml of ethanol-water solution. Then, 0.8g of TiO2 and a binder were thoroughly mixed at a ratio of 8:2. The mixture was then applied to a wavy interdigitated electrode with a spacing of 50μm. The electrode was then calcined in a muffle furnace at 450°C for 2 hours to obtain a TiO2 photocatalyst interdigitated electrode film.

[0070] (2) Photocatalytic interdigitated electrode thin film for gas-phase photoelectrocatalytic reduction of CO2

[0071] The TiO2 photocatalyst interdigitated electrode film obtained in step (1) is placed in a container filled with CO2, and a potential of 2.0 V is applied to perform photocatalytic reduction of CO2. After the reaction for 1 hour, a sample is taken out and measured by gas chromatography.

[0072] The electrochemical self-doped photocatalyst nanotube-based materials assembled by Examples 2-6 of the present invention all have strong gas-phase photoelectrocatalytic activity, can efficiently reduce CO2 to alkane energy substances under light conditions, and the materials themselves have excellent stability and durability.

[0073] Obviously, the above embodiments are merely examples for the purpose of clearly illustrating the present invention and are not intended to limit the implementation of the present invention. Those skilled in the art will readily appreciate that other variations or modifications may be made based on the above description. It is not necessary and impossible to enumerate all possible implementations here. Obvious variations or modifications derived therefrom remain within the scope of protection of the present invention.

Claims

1. A method for enhancing gas-phase photocatalytic CO2 reduction performance based on interdigitated electrodes, characterized by: First, a photocatalyst and a binder are mixed and loaded onto interdigitated electrodes to assemble a photocatalyst interdigitated electrode film. Then, the photocatalyst interdigitated electrode film is placed in a container filled with CO2, and a small external voltage is applied to the photocatalyst interdigitated electrode film. This creates a high-intensity electric field at the micro-spacing of the interdigitated electrodes, promoting the separation of photogenerated carriers. This also causes the Helmholtz layer to reconstruct, shifting the conduction band upward, and increasing the reduction potential of the photocatalyst to activate CO2, thereby improving the photocatalytic CO2 reduction performance. The interdigital electrodes are linear interdigital electrodes, wavy interdigital electrodes or arc-shaped interdigital electrodes; the electrode spacing of the interdigital electrodes is 1 to 500 μm; The photocatalyst is TiO2, WO3, ZnO, BiVO4 or g-C3N4; the adhesive is polyvinyl alcohol or polyethylene glycol; the mixing ratio of the photocatalyst to the adhesive is (6:4) to (9:1); The voltage of the applied micro external voltage is 0.1 to 3.0V.

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