A method for preparing a CuBi₂O₄ / CdO photocathode for photoelectrocatalytic water splitting

Abstract

This invention relates to a method for preparing a CuBi₂O₄ / CdO photocathode for photoelectrocatalytic water splitting. The invention utilizes a combination of electrodeposition and CVD processing to prepare a highly crystalline CuBi₂O₄ photocathode. During the preparation process, CdO particles are loaded onto the surface of the CuBi₂O₄ photocathode, forming a CuBi₂O₄ / CdO heterojunction. A CuBi₂O₄ electrode loaded with CdO particles is obtained on FTO glass, resulting in improved performance of the CuBi₂O₄ photocathode. Firstly, the CuBi₂O₄ electrode loaded with CdO particles exhibits a change in material color, significantly enhancing its light absorption performance. Secondly, the formation of the CuBi₂O₄ / CdO heterojunction greatly improves the carrier transfer rate and reduces the electron-hole recombination rate. Simultaneously, the photocorrosion properties of the material are greatly improved, significantly enhancing its stability in the working environment.

Description

Technical Field

[0001] This invention relates to a method for preparing a CuBi2O4 / CdO photocathode for photoelectrocatalytic water splitting, belonging to the field of photoelectrochemical technology. Background Technology

[0002] With the development and progress of human technology, energy and environmental issues have become increasingly prominent and seriously affect human health and development. One feasible way to solve these problems is to find a pollution-free and sustainable new energy source. Hydrogen energy, with its advantages of being pollution-free, sustainable, and having a high calorific value, is a high-quality energy source that perfectly meets people's expectations. However, while hydrogen energy has significant advantages, it also faces some problems that urgently need to be addressed, such as high production costs and transportation difficulties. One feasible solution in terms of production is photoelectrochemical (PEC) water splitting to produce hydrogen. This method reduces the cost of hydrogen production and significantly reduces environmental pollution. In photoelectrochemicals, most research on PEC water splitting focuses on photoanode materials, but only a few studies have investigated photocathodes based on metal oxides. A common strategy for achieving high-efficiency conversion of sunlight into hydrogen energy is to combine a narrow-bandgap photocathode with a more positive onset potential with a semiconductor photoelectrode with complementary light absorption into a series cell for complete water splitting to produce hydrogen. Therefore, finding a low-cost semiconductor photocathode material with a suitable bandgap structure and a more positive onset potential remains a challenge.

[0003] The following criteria are used to select photocathode materials: ① A suitable band gap. The band gap needs to be small enough to absorb more sunlight, and its position needs to be appropriate to ensure the photoelectrocatalytic water splitting process can occur; ② The material needs good stability to function stably in the photoelectrochemical process; ③ The material needs to be non-toxic and harmless; ④ The material needs to be inexpensive and readily available to reduce the cost of hydrogen production. CuBi₂O₄, as a p-type semiconductor, exhibits some attractive properties when used as a photocathode. These include: CuBi₂O₄ has a relatively narrow band gap (between 1.5 and 1.8 eV), and its conduction band is located at a potential more negative than the water reduction potential, while its valence band is located at a potential more positive than the water oxidation potential. This allows CuBi₂O₄ to better perform its photoelectrocatalytic function. At the same time, CuBi₂O₄ is also non-toxic, harmless, inexpensive, and readily available. However, CuBi₂O₄ also has some disadvantages, such as poor stability, low carrier mobility, and high photogenerated electron-hole recombination rate.

[0004] Therefore, obtaining CuBi2O4 photocathodes with higher photoelectric conversion efficiency and photoelectric stability in a simple and inexpensive manner remains a challenge. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention provides a method for preparing a CuBi2O4 / CdO photocathode for photoelectrocatalytic water splitting. Invention Overview:

[0007] This invention utilizes a combination of electrodeposition and CVD processing to prepare a highly crystalline CuBi₂O₄ photocathode. During the preparation process, CdO particles are loaded onto the surface of the CuBi₂O₄ photocathode, forming a CuBi₂O₄ / CdO heterojunction. This results in a CdO-loaded CuBi₂O₄ electrode on FTO glass, leading to improved performance of the CuBi₂O₄ photocathode. Firstly, the CdO-loaded CuBi₂O₄ electrode exhibits a change in material color, significantly enhancing its light absorption performance. Secondly, the CuBi₂O₄ / CdO heterojunction greatly improves the carrier transfer rate and reduces the electron-hole recombination rate. Simultaneously, the photocorrosion properties are greatly reduced, significantly improving the material's stability in the working environment. This invention successfully prepares a highly efficient and green photocatalytic material, providing a new approach for hydrogen energy production and application.

[0008] Terminology Explanation:

[0009] FTO glass: Fluorine-doped SnO2 transparent conductive glass.

[0010] CVD: Chemical vapor deposition (CVD) refers to the method of synthesizing coatings or nanomaterials by reacting chemical gases or vapors on the surface of a substrate.

[0011] This invention is achieved through the following technical solution:

[0012] A method for preparing a CuBi₂O₄ / CdO photocathode for photoelectrocatalytic water splitting includes the following steps:

[0013] 1) Provide a substrate and perform pretreatment;

[0014] 2) Preparation of electrodeposition precursor solution: Dissolve bismuth source, copper source, cadmium source and KClO4 in dimethyl sulfoxide and mix well to obtain electrodeposition precursor solution;

[0015] 3) Add the electrodeposition precursor solution to the electrodeposition tank, using the pretreated substrate from step (1) as the working electrode, a platinum sheet as the counter electrode, and Ag / AgCl as the reference electrode to form a three-electrode system for electrodeposition; the electrode spacing is 1-10 cm, the applied bias voltage is -1 to -3 V, and the deposition charge is maintained at 0.01 to 0.05 Ccm. -2 Repeated deposition; after electrodeposition, a substrate bearing precursor material is obtained;

[0016] 4) The substrate containing the precursor material is dried at room temperature and then placed in a muffle furnace for annealing for 2-6 hours to obtain a CuBi2O4 / CdO photocathode.

[0017] According to a preferred embodiment of the present invention, in step 1), the substrate is an FTO glass substrate.

[0018] According to a preferred embodiment of the present invention, in step 1), the pretreatment is as follows: the substrate is sequentially immersed in acetone, isopropanol, and deionized water and ultrasonically treated for 20-40 minutes each, and then the substrate is dried in a N2 atmosphere at room temperature.

[0019] According to a preferred embodiment of the present invention, in step 2), the bismuth source is Bi(NO3)3·5(H2O).

[0020] According to a preferred embodiment of the present invention, in step 2), the concentration of bismuth source in the electrodeposition precursor solution is 8-15 mM.

[0021] Most preferably, in step 2), the bismuth source concentration in the electrodeposition precursor solution is 10 mM.

[0022] According to a preferred embodiment of the present invention, in step 2), the copper source is Cu(NO3)2·3H2O.

[0023] According to a preferred embodiment of the present invention, in step 2), the copper source concentration in the electrodeposition precursor solution is 3-6 mM.

[0024] Most preferably, in step 2), the copper source concentration in the electrodeposition precursor solution is 5 mM.

[0025] According to a preferred embodiment of the present invention, in step 2), the cadmium source is Cd(NO3)2·4H2O.

[0026] According to a preferred embodiment of the present invention, in step 2), the concentration of cadmium source in the electrodeposition precursor solution is 0.5-3 mM.

[0027] Most preferably, in step 2), the concentration of the cadmium source in the electrodeposition precursor solution is 1 mM.

[0028] According to a preferred embodiment of the present invention, in step 2), the concentration of KClO4 in the electrodeposition precursor solution is 80-120 mM.

[0029] According to a preferred embodiment of the present invention, in step 3), the applied bias voltage is -1.5V, and the deposited charge is maintained at 0.04Ccm. -2 .

[0030] According to a preferred embodiment of the present invention, in step 3), the electrodeposition is repeated 8-12 times, with a 5-second pause between each deposition.

[0031] According to a preferred embodiment of the present invention, in step 4), the annealing temperature is 450-580°C.

[0032] Most preferably, in step 4), the annealing temperature is 500℃ and the annealing time is 3h.

[0033] The technical features and beneficial effects of this invention are as follows:

[0034] 1. This invention prepares a CuBi2O4 / CdO photocathode using a simple electrodeposition combined with CVD method. CdO particles are loaded onto the surface of the CuBi2O4 photocathode to form a CuBi2O4 / CdO heterojunction. A CuBi2O4 electrode loaded with CdO particles is obtained on FTO glass, which makes the CuBi2O4 photocathode have better performance. In addition, the two materials are very tightly bonded, which also makes the band gaps of the materials well matched.

[0035] 2. The CuBi2O4 / CdO photocathode prepared by this invention has a pn heterojunction structure. This structure greatly improves the photogenerated electron-hole transfer efficiency of the material and reduces the recombination effect of electrons and holes. At the same time, the carrier migration rate of the material is also greatly improved.

[0036] 3. The stability of the CuBi2O4 / CdO photocathode prepared by this invention has been greatly improved, which increases the service life of the material and reduces the cost, laying a good foundation for future industrial production. Attached Figure Description

[0037] Figure 1 The images shown are SEM images of the CuBi2O4 / CdO photocathode and the CuBi2O4 photocathode in Experimental Example 1 of this invention. a is the CuBi2O4 / CdO photocathode, and b is the CuBi2O4 photocathode.

[0038] Figure 2 The UV-Vis curves of the CuBi2O4 / CdO photocathode and the CuBi2O4 photocathode in Experiment Example 1 of this invention are shown.

[0039] Figure 3 This is an HRTEM image of the CuBi2O4 / CdO photocathode in Experimental Example 1 of this invention.

[0040] Figure 4 The images show the XRD patterns of the CuBi₂O₄ / CdO photocathode and the CuBi₂O₄ photocathode in Experimental Example 1 of this invention.

[0041] Figure 5 The JV curves are for the CuBi2O4 / CdO photocathode and the CuBi2O4 photocathode in Experiment Example 1 of this invention.

[0042] Figure 6 The IPCE efficiency curves of CuBi2O4 / CdO photocathode and CuBi2O4 photocathode in Experiment Example 1 of this invention are shown.

[0043] Figure 7 The stability curves of the CuBi2O4 / CdO photocathode and the CuBi2O4 photocathode in Experimental Example 1 of this invention are shown.

[0044] Figure 8 The EIS curves of the CuBi2O4 / CdO photocathode and the CuBi2O4 photocathode in Experiment Example 1 of this invention are shown.

[0045] Figure 9 The LSV curves of different samples obtained in Examples 1-3 are shown.

[0046] Figure 10 The diagram shows the hydrogen production process of water splitting using the CuBi2O4 / CdO photocathode of Example 1 and the CuBi2O4 photocathode of Comparative Example 1.

[0047] Figure 11 This is an EDS elemental distribution diagram of the CuBi2O4 / CdO photocathode in Example 1 of the present invention.

[0048] Figure 12 The images show the appearance of samples obtained at different annealing temperatures in Experimental Example 2 of this invention. Detailed Implementation

[0049] The present invention is further illustrated by the following examples, but is not limited thereto.

[0050] Unless otherwise specified, all reagents used in the examples are commercially available products.

[0051] Example 1

[0052] A method for preparing a CuBi₂O₄ / CdO photocathode for photoelectrocatalytic water splitting includes the following steps:

[0053] 1) The FTO glass substrate was sequentially immersed in acetone, isopropanol and deionized water, and ultrasonically treated for 30 minutes each, and then dried in a N2 atmosphere at room temperature;

[0054] 2) Preparation of electrodeposition precursor solution: Dissolve Bi(NO3)3·5(H2O), Cu(NO3)2·3H2O, Cd(NO3)2·4H2O, and KClO4 in dimethyl sulfoxide and mix thoroughly to obtain the electrodeposition precursor solution; the concentration of Bi(NO3)3·5(H2O) in the electrodeposition precursor solution is 10 mM, the concentration of Cu(NO3)2·3H2O is 5 mM, the concentration of Cd(NO3)2·4H2O is 1 mM, and the concentration of KClO4 in the electrodeposition precursor solution is 100 mM;

[0055] 3) Add the electrodeposition precursor solution to the electrodeposition tank, using the pretreated substrate from step (1) as the working electrode, a platinum sheet as the counter electrode, and Ag / AgCl as the reference electrode to form a three-electrode system for electrodeposition; the electrode spacing is 3 cm, the applied bias voltage is -1.5 V, and the deposition charge is maintained at 0.04 Ccm. -2 The electrodeposition process was repeated 10 times, with a 5-second pause between each deposition. After the electrodeposition was completed, a substrate bearing the precursor material was obtained.

[0056] 4) The substrate with the precursor material was dried at room temperature and then placed in a muffle furnace and annealed at 500°C for 3 hours to obtain CuBi2O4 / CdO photocathode (i.e. CuBi2O4 electrode loaded with CdO particles).

[0057] Comparative Example 1

[0058] A method for preparing a CuBi₂O₄ photocathode includes the following steps:

[0059] 1) The FTO glass substrate was sequentially immersed in acetone, isopropanol and deionized water, and ultrasonically treated for 30 minutes each, and then dried in a N2 atmosphere at room temperature;

[0060] 2) Preparation of electrodeposition precursor solution: Dissolve Bi(NO3)3·5(H2O), Cu(NO3)2·3H2O, and KClO4 in dimethyl sulfoxide and mix thoroughly to obtain the electrodeposition precursor solution; the concentration of Bi(NO3)3·5(H2O) in the electrodeposition precursor solution is 10 mM, the concentration of Cu(NO3)2·3H2O is 5 mM, and the concentration of KClO4 in the electrodeposition precursor solution is 100 mM;

[0061] 3) Add the electrodeposition precursor solution to the electrodeposition tank, using the pretreated substrate from step (1) as the working electrode, a platinum sheet as the counter electrode, and Ag / AgCl as the reference electrode to form a three-electrode system for electrodeposition; the electrode spacing is 3 cm, the applied bias voltage is -1.5 V, and the deposition charge is maintained at 0.04 Ccm. -2The electrodeposition process was repeated 10 times, with a 5-second pause between each deposition. After the electrodeposition was completed, a substrate bearing the precursor material was obtained.

[0062] 4) The substrate bearing the precursor material was dried at room temperature and then placed in a muffle furnace and annealed at 500°C for 3 hours to obtain a CuBi2O4 photocathode.

[0063] Experimental Example 1

[0064] 1. SEM images of the CuBi₂O₄ / CdO photocathode of Example 1 and the CuBi₂O₄ photocathode of Comparative Example 1 are shown below. Figure 1 As shown, from Figure 1 As can be seen, the CuBi2O4 electrode loaded with CdO particles of the present invention did not significantly change the morphology of the sample before and after loading, compared with Comparative Example 1.

[0065] 2. The UV-Vis curves of the CuBi₂O₄ / CdO photocathode of Example 1 and the CuBi₂O₄ photocathode of Comparative Example 1 are shown below. Figure 2 As shown, the CuBi2O4 electrode loaded with CdO particles in Example 1 of the present invention has a certain increase in ultraviolet absorption compared with Comparative Example 1, which indicates that the sample has enhanced light absorption performance.

[0066] 3. The HRTEM image of the CuBi2O4 / CdO photocathode in Example 1 is shown below. Figure 3 As shown, high-resolution TEM (HR-TEM) imaging revealed that the lattice spacings of copper bismuthate and CdO were 0.313 nm and 0.234 nm, respectively, and were composed of the (211) crystal plane of copper bismuthate and the (200) crystal plane of CdO, indicating the formation of a copper bismuthate / CdO buried heterojunction.

[0067] 4. The XRD patterns of the CuBi₂O₄ / CdO photocathode of Example 1 and the CuBi₂O₄ photocathode of Comparative Example 1 are shown below. Figure 4 As shown, the phase structure of the product was analyzed by powder X-ray diffraction (PXRD), and diffraction peaks of tetragonal copper bismuthate (JCPDS no. 48-1886) and cubic CdO (JCPDS no. 05-0640) were found in the copper bismuthate / CdO heterostructure.

[0068] 5. The JV curves of the CuBi₂O₄ / CdO photocathode of Example 1 and the CuBi₂O₄ photocathode of Comparative Example 1 are as follows: Figure 5 As shown in Example 1 of the present invention, the CuBi2O4 electrode loaded with CdO particles exhibits significantly improved photoelectric properties after loading with CdO particles.

[0069] 6. To gain a deeper understanding of the changes in photoresponse, the incident photon-to-current conversion efficiency (IPCE) under monochromatic light illumination was measured. The IPCE efficiency curves of the CuBi₂O₄ / CdO photocathode in Example 1 and the CuBi₂O₄ photocathode in Comparative Example 1 are shown below. Figure 6 As shown, through Figure 6 It can be seen that the IPCE value of CuBi2O4 / CdO photocathode is significantly improved, especially in the illumination range of 350–550 nm.

[0070] 7. The stability curves of the CuBi₂O₄ / CdO photocathode of Example 1 and the CuBi₂O₄ photocathode of Comparative Example 1 are shown below. Figure 7 As shown, the CuBi2O4 electrode loaded with CdO particles in Example 1 of the present invention exhibits significantly improved stability compared to ordinary samples.

[0071] 8. The EIS curves of the CuBi₂O₄ / CdO photocathode of Example 1 and the CuBi₂O₄ photocathode of Comparative Example 1 are shown below. Figure 8 As shown in the figure, the resistance of the sample is significantly reduced, and the conductivity is significantly improved.

[0072] Example 2

[0073] The preparation method of CuBi₂O₄ / CdO photocathode for photoelectrocatalytic water splitting described in Example 1 differs from that in:

[0074] In step 2), the concentration of Bi(NO3)3·5(H2O) in the electrodeposition precursor solution is 10 mM, the concentration of Cu(NO3)2·3H2O is 5 mM, the concentration of Cd(NO3)2·4H2O is 0.5 mM, the concentration of KClO4 in the electrodeposition precursor solution is 100 mM, and other steps are performed as in Example 1.

[0075] Example 3

[0076] The preparation method of CuBi₂O₄ / CdO photocathode for photoelectrocatalytic water splitting described in Example 1 differs from that in:

[0077] In step 2), the concentration of Bi(NO3)3·5(H2O) in the electrodeposition precursor solution is 10 mM, the concentration of Cu(NO3)2·3H2O is 5 mM, the concentration of Cd(NO3)2·4H2O is 1.5 mM, the concentration of KClO4 in the electrodeposition precursor solution is 100 mM, and other steps are performed as in Example 1.

[0078] Comparative Example 2

[0079] The preparation method of CuBi₂O₄ / CdO photocathode for photoelectrocatalytic water splitting described in Example 1 differs from that in:

[0080] In step 4), the substrate bearing the precursor material is dried at room temperature and then placed in a muffle furnace and annealed at 400°C for 3 hours to obtain a CuBi2O4 / CdO photocathode. Other steps are carried out according to Example 1.

[0081] Comparative Example 3

[0082] The preparation method of CuBi₂O₄ / CdO photocathode for photoelectrocatalytic water splitting described in Example 1 differs from that in:

[0083] In step 4), the substrate bearing the precursor material is dried at room temperature and then placed in a muffle furnace and annealed at 600°C for 3 hours to obtain a CuBi2O4 / CdO photocathode. Other steps are carried out according to Example 1.

[0084] Experimental Example 2

[0085] 1. The LSV curves of different samples obtained in Examples 1-3 are as follows: Figure 9 As shown, through Figure 9 It can be seen that the best results are achieved when the concentrations of Bi(NO3)3·5(H2O) in the electrodeposition precursor solution are 10 mM, Cu(NO3)2·3H2O is 5 mM, and Cd(NO3)2·4H2O is 1 mM.

[0086] 2. Hydrogen production from water splitting using the CuBi₂O₄ / CdO photocathode of Example 1 and the CuBi₂O₄ photocathode of Comparative Example 1, with gas production rates as follows: Figure 10 As shown in the figure, the gas generation performance of the CuBi2O4 electrode loaded with CdO particles is significantly improved.

[0087] 3. The EDS elemental distribution of the CuBi₂O₄ / CdO photocathode in Example 1 is shown in [reference needed]. Figure 11 This demonstrates the presence of Cd element distribution in the CuBi2O4 / CdO photocathode.

[0088] 4. The appearance of the samples obtained at different annealing temperatures in Example 1, Comparative Examples 2 and 3 is shown in the figure. Figure 12 Comparative Example 2 was annealed at 400℃ for 3 hours to obtain a CuBi2O4 / CdO photocathode, which had a light color and poor performance. Comparative Example 3 was annealed at 600℃ for 3 hours to obtain a CuBi2O4 / CdO photocathode, which had a darker color, but the substrate had cracked.

Claims

1. A method for preparing a CuBi₂O₄ / CdO photocathode for photoelectrocatalytic water splitting, comprising the following steps: 1) Provide a substrate and perform pretreatment; 2) Preparation of electrodeposition precursor solution: Dissolve bismuth source, copper source, cadmium source, and KClO4 in dimethyl sulfoxide and mix thoroughly to obtain the electrodeposition precursor solution. The concentration of bismuth source in the electrodeposition precursor solution is 8-15 mM, the copper source is Cu(NO3)2·3H2O, the concentration of copper source in the electrodeposition precursor solution is 3-6 mM, the concentration of cadmium source in the electrodeposition precursor solution is 0.5-3 mM, and the concentration of KClO4 in the electrodeposition precursor solution is 80-120 mM. 3) Add the electrodeposition precursor solution to the electrodeposition tank, using the pretreated substrate from step (1) as the working electrode, a platinum sheet as the counter electrode, and Ag / AgCl as the reference electrode to form a three-electrode system for electrodeposition; the electrode spacing is 1-10 cm, the applied bias voltage is -1.5 V, and the deposition charge is maintained at 0.04 Ccm. -2 The electrodeposition process was repeated 8-12 times, with a 5-second pause between each deposition. After the electrodeposition was completed, a substrate bearing the precursor material was obtained. 4) The substrate containing the precursor material is dried at room temperature and then placed in a muffle furnace for annealing for 2-6 hours to obtain a CuBi2O4 / CdO photocathode at an annealing temperature of 450-580℃.

2. The preparation method according to claim 1, characterized in that, In step 1), the substrate is an FTO glass substrate, and the pretreatment is as follows: the substrate is immersed in acetone, isopropanol and deionized water in sequence and ultrasonically treated for 20-40 minutes each, and then the substrate is dried in N2 atmosphere at room temperature.

3. The preparation method according to claim 1, characterized in that, In step 2), the bismuth source is Bi(NO3)3·5H2O.

4. The preparation method according to claim 1, characterized in that, In step 2), the cadmium source is Cd(NO3)2·4H2O.

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