Preparation and Application of an Integrated Cuprous Oxide Photoelectrode

Abstract

The present invention discloses a preparation method based on an integrated cuprous oxide photocathode. The method includes the preparation of a protein template, the step of preparing a hole transport layer on a conductive substrate, the formation of an inverse protein cuprous oxide photonic crystal structure, and the preparation of a protective layer. Its feature lies in that the step of preparing the photocathode based on the multiple modification of cuprous oxide photonic crystals includes: self-assembling a nanoscale protein template on the substrate with a hole transport layer, then electroplating cuprous oxide and a protective layer by an electrochemical method, and finally forming a multifunctional photocathode with an inverse protein photonic crystal structure through a high-temperature pyrolysis method or a solvent adsorption and desorption method. The multi-layer modified inverse protein Cu2O photocathode obtained by the present invention presents an ordered porous structure and exhibits the characteristics of a photonic crystal. By controlling the size of the protein template, the internal morphology of the inverse protein photonic crystal is regulated, and with the assistance of superimposing multi-layer functional thin films, three goals are achieved: a, improving the light capture ability of the material; b, increasing the photogenerated charge separation efficiency and accelerating the transfer of photogenerated electrons-holes from the bulk to prevent their self-oxidation; c, and avoiding the self-reduction of cuprous oxide through the presence of the protective layer. In the photo-electrochemical catalytic carbon dioxide reaction, the integrated Cu2O photocathode efficiently converts carbon dioxide into carbon monoxide (Φ STC = 1.6%, Yeild CO = 46.7 mmol / h).

Description

Technical Field

[0001] The present invention belongs to the technical field of photocatalytic CO2 conversion, and relates to an integrated cuprous oxide photocatalytic material, a preparation method thereof, and an application thereof. Background Art

[0002] With the continuous development of China's industry, the demand for energy in China continues to rise. The combustion of fossil fuels will emit a large amount of carbon dioxide. Therefore, converting CO2 into fuel or value-added fuel is a very promising option to solve the energy shortage problem and environmental problems. Semiconductor materials can catalyze the conversion of CO2 into fuel or additional chemicals through the photoelectrochemical process, which has attracted extensive attention.

[0003] Cuprous oxide (Cu2O) is a naturally occurring p-type semiconductor material. The direct bandgap is 1.9 - 2.2 eV, and it has potential applications in photocatalytic water splitting and photocatalytic CO2 reduction. However, the main factors affecting the photocatalytic performance of Cu2O are the limited specific surface area, light absorption ability, charge separation efficiency, and its susceptibility to photocorrosion. These factors greatly limit the application of Cu2O in the field of photocatalysis. Research shows that the construction of heterojunctions can improve the photogenerated charge separation efficiency, and the introduction of a hole transport layer and a protective layer can further improve the stability of Cu2O. In addition, designing the traditional planar electrode structure into a porous array structure can greatly increase the photoelectrochemical catalytic surface area. Based on the above discussion, developing a method to prepare heterojunction structures, hole transport layers, protective layers, and active photonic crystals is expected to solve the problems existing in pure-phase Cu2O materials, which is of great significance for promoting the development of photocatalysis. Summary of the Invention

[0004] According to one aspect of the present application, a preparation method of an integrated cuprous oxide photocathode with a porous array structure is provided. The integrated Cu2O photocathode with a porous array structure prepared by this method has a highly ordered pore structure and an intensive charge transport functional layer, and has good catalytic prospects for photocatalytic CO2 reduction and water splitting reactions.

[0005] In the present application, PS microspheres are self-assembled on a conductive substrate, and Cu2O is filled in the voids of the PS microspheres using this as a template, and different hole transport layers and protective layers are modified on the Cu2O. After removing the template, a series of integrated Cu2O photocathodes with a three-dimensional pore array structure are obtained.

[0006] A preparation method of an integrated cuprous oxide (Cu2O) photocatalytic material, characterized in that the method at least includes: preparation of a hole transport layer, preparation of a template, depositing cuprous oxide on the template, removing the template, and preparation of a protective layer to obtain the integrated cuprous oxide photocathode;

[0007] Among them, the template is polystyrene (PS) microspheres self-assembled on a substrate.

[0008] The hole transport layer is selected from at least one of inorganic semiconductor materials and organic materials;

[0009] Preferably, the hole transport layer is selected from FeOOH, MoO x 、WO x 、NiO, FTB (poly[(9,9-dioctylfluorene-2,7-diyl)-CO-(4,4′-(N-(4-sec-butylphenyl)diphenylamine)]), PVK (polyvinylcarbazole), TCTA (tris(4-carbazolyl-9-ylphenyl)amine), PEDOT:PSS (poly(3,4-ethylenedioxythiophene) / polystyrenesulfonate)) of at least one;

[0010] More preferably, the hole transport material is selected from FeOOH, NiO, CuO, CuSCN, poly(3,4-ethylenedioxythiophene) / PEDOT:PSS;

[0011] Preferably, the preparation method of the hole transport layer is selected from at least one of spin coating and calcination, chemical deposition, vacuum thermal evaporation, and magnetron sputtering technology;

[0012] The nano-microspheres self-assembled on the conductive substrate include self-assembling the nano-microspheres on the conductive substrate; preferably, the self-assembly method is selected from at least one of vertical / tilted solvent evaporation self-assembly method, convective self-assembly method, physical confinement self-assembly method, dip-coating self-assembly method, and dip-coating and scraping method;

[0013] Preferably, the solvent of the PS microsphere solution is selected from at least one of deionized water, absolute ethanol, absolute methanol, and isopropanol;

[0014] Preferably, the mass fraction of the PS microsphere solution is 0.05-1 wt%;

[0015] More preferably, the mass fraction of the PS microsphere solution is 0.1-0.3 wt%;

[0016] The deposition of Cu2O includes depositing Cu2O on the template;

[0017] Preferably, the deposition method is selected from at least one of water bath chemical reduction method, electro-deposition method, and hydrothermal method;

[0018] The method for removing the template includes one of soaking and eluting, and thermal cracking;

[0019] Preferably, the solution for soaking and eluting includes one of acetone, tetrahydrofuran, toluene, and N,N-dimethylformamide (DMF);

[0020] Preferably, the thermal decomposition conditions are 400 - 600 °C;

[0021] The protective layer is selected from at least one of inorganic semiconductor materials and organic materials;

[0022] Preferably, the protective layer is selected from at least one of polypyrrole, polythiophene, polyaniline, and TiO₂;

[0023] More preferably, the protective layer material is selected from at least one of polypyrrole, polythiophene, and TiO₂.

[0024] Preferably, the preparation method of the protective layer is selected from at least one of hydrothermal, spin - coating calcination, and electrochemical deposition techniques;

[0025] The conductive substrate is selected from at least one of metal substrates, conductive glass substrates, flexible substrates, and silicon wafers;

[0026] Preferably, the metal conductive substrate is selected from at least one of copper sheets, nickel sheets, aluminum sheets, and titanium sheets;

[0027] Preferably, the glass conductive substrate is selected from at least one of ITO conductive glass, FTO conductive glass, and AZO conductive glass;

[0028] Preferably, the flexible substrate is selected from at least one of transparent polyester amide and conductive PET;

[0029] According to another aspect of the present application, the application of the prepared integrated cuprous oxide photocathode in photo - electrocatalytic carbon dioxide conversion or water splitting, the characteristics include at least one of the cuprous oxide composite catalytic materials with a porous array structure prepared by the above - mentioned method, and performing photo - electrocatalytic carbon dioxide reduction or water splitting reactions, photo - response tests, and stability tests. Description of the Drawings

[0030] Figure 1 It is the surface scanning electron microscopy (SEM) image and particle size distribution of the PS template prepared by the vertical self - assembly method.

[0031] Figure 2 It is the surface scanning electron microscopy (SEM) image of Cu₂O Io prepared by the electrodeposition method.

[0032] Figure 3 It is the surface and cross - section scanning electron microscopy (SEM) images of the FCuP Io photocathode.

[0033] Figure 4 It is the yield graph and Φ of the FCuP Io photocathode in the photo - electrocatalytic CO₂ reduction reaction. STC .

[0034] Figure 5 For the stability of the FCuP Io photocathode.

[0035] Figure 6 For the long-term reaction stability of the FCuP Io photocathode. Specific embodiments

[0036] The preparation method of the multi-modified cuprous oxide photonic crystal material provided by the present invention, the photoelectrocatalytic CO2 reduction test and the stability test are further elaborated below in conjunction with specific embodiments. However, the present application is not limited to these examples. The drugs used in the present application are directly used without further purification without special instructions. Specific embodiments

[0038] The preparation method of the integrated Cu2O photocathode provided by the present invention is further elaborated below in conjunction with specific embodiments.

[0039] Example 1:

[0040] Preparation of PS microspheres (400 nm)

[0041] Mix 10 ml of styrene with 80 ml of absolute ethanol, add 1 g of polyvinylpyrrolidone to the above mixed solution, stir for 0.5 - 1 h, add 10 ml of azodiisobutyramidine hydrochloride solution (AIBA, 7.8 g / L), and react at 70 °C for 12 hours under a N2 atmosphere. After the reaction, cool to room temperature, wash and centrifuge with deionized water, and place the centrifuged polystyrene (PS) microspheres in a 70 °C constant temperature oven for drying. Weigh a certain amount of dried PS powder and prepare a 10 wt% monodisperse PS microsphere storage solution.

[0042] Example 2

[0043] Preparation of integrated cuprous oxide photocathode functional material (FCuP Io: FeOOH@Cu2O Io@PPy)

[0044] (1) Pretreatment of the FTO conductive substrate:

[0045] Use to clean the dust particles and organic oil stains attached to the surface of the FTO conductive substrate, and then ultrasonically clean the FTO conductive substrate with deionized water, FTO cleaning solution, and isopropyl alcohol for 15 min respectively, and set aside.

[0046] (2) Preparation of the Fh hole transport layer:

[0047] Dissolve 0.108 g of FeCl3·6H2O and 0.056 g of Na2SO4 in 40 ml of deionized water. After stirring for 0.5 - 1 hour, tilt the conductive substrate with the conductive side downward at an angle of 30 - 60° and stand it on the inner wall of the PTFE liner. React at 120 °C for 2 h. After the reaction, cool it to room temperature, wash the FTO conductive substrate with deionized water, and dry it with nitrogen to obtain the Fh hole transport layer.

[0048] (3)Preparation of PS microsphere array

[0049] Dilute the 10 wt% PS microsphere stock solution to a 0.15 wt% PS microsphere mixture. Stir for 0.5 - 1 h. Vertically place the Fh conductive substrate sheet obtained in step (2) in the evaporation tank. Pour the PS microsphere mixture into the evaporation tank to submerge the Fh conductive substrate, and evaporate at room temperature. After the solvent is completely evaporated, an electrode with a template is obtained. The scanning electron microscope image (SEM) and particle size distribution of this template are as Figure 1 shown.

[0050] (4)Preparation of Cu2O protein structure:

[0051] Prepare a mixed solution of 0.4 M copper sulfate and 4 M lactic acid respectively as the electro-deposited p type cuprous oxide. Use a three-electrode system for the electro-deposition of cuprous oxide. Among them, the PS array obtained in step (3) is used as the working electrode, a platinum sheet is used as the counter electrode, and Ag / AgCl is used as the reference electrode for electro-deposition to obtain Cu2O. p -Cu2O adopts chronoamperometry, -0.6 mA / cm 2 , electro-deposit at 60 °C for 20 min.

[0052] (5)Formation of cuprous oxide inverse protein structure:

[0053] Immerse the electrode obtained in step (4) in DMF solvent to dissolve the PS microspheres. After soaking for 6 hours, take it out and dry it with nitrogen. A Cu2O photonic crystal structure is formed. The Cu2O photonic crystal structure is as Figure 2 shown.

[0054] (6)Preparation of polypyrrole (PPy) protective layer:

[0055] Prepare a 0.3 mM acetonitrile solution of pyrrole as the precursor solution for the electro-deposition of polypyrrole, and 0.1 M tetrabutylammonium hexafluorophosphate (TBAP) as the supporting electrolyte. Use a three-electrode system for the preparation of polypyrrole. Among them, the electrode obtained in step (5) is used as the working electrode, platinum is used as the counter electrode, and Ag / Ag + is used as the reference electrode. Use the potentiostatic method (0.8V vs Ag / Ag +), deposit for 2 min. A Cu2O Io photonic crystal protected by polypyrrole (PPy) is formed, and the structure of the Cu2O photonic crystal protected by polypyrrole is shown in Figure 3.

[0056] Example 3

[0057] Preparation of photocatalytic material of multi-modified cuprous oxide photonic crystal photocathode material (NiO@Cu2O Io@PTh)

[0058] (1) Pretreatment of FTO conductive substrate:

[0059] Clean the FTO conductive glass substrate by the method described in step (1) of Example 1.

[0060] (2) Preparation of NiO x Preparation of hole transport layer:

[0061] Dissolve 0.2908 g of NiCl2·6H2O in 10 ml of 2-methoxyethanol, add 1 μL of acetylacetone as an additive to prepare a NiO x precursor solution. Age at 45 °C for 12 hours. Spin-coat the NiO x precursor solution on the FTO conductive glass at a speed of 4000 r / min, anneal at 175 °C for 1.5 hours, and then subject the NiO x film to ultraviolet-ozone treatment.

[0062] (3) Preparation of PS microsphere array

[0063] Use the method described in step (2) of Example 2 to self-assemble a PS microsphere array on the surface of the NiO x hole transport layer prepared in step (2).

[0064] (4) Preparation of Cu2O protein structure:

[0065] Prepare Cu2O by the method described in step (4) of Example 2 for the PS microsphere template prepared in step (3).

[0066] (5) Formation of Cu2O inverse protein structure:

[0067] Immerse the electrode obtained in step (4) in acetone solvent to remove the PS microspheres, take it out after soaking for 6 hours, and dry it with nitrogen to obtain an electrode with an inverse protein structure.

[0068] (6) Preparation of polythiophene protective layer

[0069] Prepare an acetonitrile solution of 0.3 mM thiophene as the precursor solution for electrodepositing polythiophene, and 0.1 M TBAP as the supporting electrolyte. The preparation of polythiophene is carried out using a three-electrode system. Among them, the electrode obtained in step (5) is used as the working electrode, platinum is used as the counter electrode, and Ag / Ag + is used as the reference electrode, and the potentiostatic method (1.2 V vs Ag / Ag + ) is adopted, and deposition for 2 min is sufficient.

[0070] Example 4

[0071] Performance test of the integrated Cu2O photocathode (FCuP Io) in the photoelectrochemical catalytic CO2

[0072] Evaluation of the photocatalytic CO2 reduction performance of the porous array structure cuprous oxide photocatalytic material: The test is carried out using a three-electrode body. The integrated cuprous oxide photocathode prepared in Example 2 is used as the working electrode, a platinum sheet is used as the counter electrode, and Ag / Ag + is used as the reference electrode, a 30 ml acetonitrile solution of TBAP (0.1 M) is used as the electrolyte, an external bias voltage is provided by Chenhua CHI660E, a xenon lamp is used as the simulated sunlight source, and a gas chromatograph is used as the CO production detection device. The CO production is counted every 15 min. As Figure 4 shown, compared with the pure-phase Cu2O photocathode, at -2.0 V vs Ag / Ag + bias voltage, the integrated FCuP Io photocathode has the highest CO production rate of 46.4 μmol / h under the full spectrum, the Faraday efficiency is close to 100%, and the efficiency of solar energy conversion to CO (Solar Conversion to CO: Φ STC ) is 1.6%. It shows that the integrated cuprous oxide photocathode (FCuP Io) can efficiently convert CO2 into CO.

[0073] Example 5

[0074] Stability test

[0075] The stability tests of the FCuP Io prepared in Example 2 and the unmodified Cu2O photocathode are carried out. Using a xenon lamp to simulate sunlight (100 mW / cm 2 ), the integrated cuprous oxide photocathode prepared in Example 2 is used as the working electrode, a platinum sheet is used as the counter electrode, and Ag / Ag + is used as the reference electrode, a 30 mL acetonitrile solution of TBAP (0.1 M) is used as the electrolyte, and an external bias voltage is provided by Chenhua CHI660E. The scanning range is -0.8 to -2.0 V vs Ag / Ag +, the scanning rate is 20 mV / s, and the recorded current-biased voltage curve is recorded. As Figure 5 shown, the FCuP Io photocathode has good optical response and long-term photocurrent stability within the scanning range; it shows long-term stable CO2 conversion efficiency and photocurrent density in the two-electrode reaction ( Figure 6 ), indicating that the FCuP Io photocathode efficiently and stably utilizes solar energy to convert carbon dioxide into carbon monoxide.

[0076] The description of the above examples is only used to help understand the method and its core idea of the present invention, including the best mode, and enables any person skilled in the art to practice the present invention. The above embodiments do not impose any form of limitation on this application. For those skilled in the relevant art, without departing from the principle of the present invention, making several modifications and improvements to the present invention also fall within the protection scope of the patent of the present invention. The protection scope of the patent of the present invention is defined by the claims and may include other embodiments that can be conceived by those skilled in the art. If these other embodiments have structural elements that are not different from the literal description of the claims, or if they include equivalent structural elements that have no substantial difference from the literal description of the claims, then these other embodiments should also be included within the scope of the claims.

Claims

1. A preparation method of an integrated cuprous oxide photocathode, characterized in that, The method includes: (1) preparing a hole transport layer on an FTO template, and the hole transport layer is selected from Fh hydrated iron, MoO x ; (2) preparing a PS microsphere array; (3) depositing a p-type cuprous oxide protein structure on the PS microsphere array by electrodeposition; (4) removing the PS microspheres to form a cuprous oxide inverse protein structure; (5) preparing a protective layer by electrodeposition, and the protective layer is polypyrrole or polythiophene.

2. Application of the integrated cuprous oxide photocathode obtained by the preparation method according to claim 1 in the photoelectrochemical catalytic conversion of carbon dioxide.

Images