Preparation method of cadmium oxide / cadmium sulfide / aluminum nano-structure photocatalytic material

Abstract

The invention discloses a preparation method of a cadmium oxide / cadmium sulfide / aluminum nano-structure photocatalytic material. The preparation method comprises the following steps: firstly, preparing a cadmium oxide flower-shaped nano-structure on conductive glass by utilizing an electro-deposition method; then growing a hydrangea-shaped cadmium sulfide nano-structure on the surface of the cadmium oxide flower-shaped nano-structure by utilizing a chemical bath deposition method; and finally, depositing aluminum nanoparticles on the surface of the cadmium oxide / cadmium sulfide nano-structure by using a magnetron sputtering method to prepare the cadmium oxide / cadmium sulfide / aluminum nano-structure photocatalytic material. The cadmium sulfide nanostructure with matched energy bands and the aluminum nanoparticles with the surface plasma resonance effect are used for cooperatively modifying the cadmium oxide nanostructure, the solar energy utilization rate and the photon-generated carrier separation efficiency are effectively improved, and excellent photoelectrochemical water decomposition electricity and hydrogen production performance is shown. The method is simple in process, the size of the obtained cadmium oxide / cadmium sulfide / aluminum heterostructure is nanoscale, and the cadmium oxide / cadmium sulfide / aluminum heterostructure is a novel nano-structure photocatalytic material and is suitable for the field of photoelectrochemical water decomposition.

Description

Technical Field

[0001] This invention relates to the field of composite photocatalytic material preparation technology, specifically to a method for preparing a cadmium oxide / cadmium sulfide / aluminum nanostructured photocatalytic material for photoelectrochemical water splitting to generate electricity and hydrogen. Background Technology

[0002] With the energy crisis and environmental pollution becoming increasingly serious, utilizing solar energy for photoelectrochemical water splitting via semiconductor photocatalysts to produce electricity and hydrogen is one of the effective ways to alleviate these problems. Under sunlight, photocatalysts are excited to generate electron-hole pairs. Electrons, with their reducing properties, reduce hydrogen ions in water to hydrogen gas, while holes, with their oxidizing properties, react with water to produce oxygen. However, current photocatalysts still face key scientific challenges such as low solar energy utilization and high carrier recombination rates.

[0003] To address the above scientific problems, the following solutions are proposed: developing visible-light-responsive photocatalysts and suppressing the recombination of photogenerated carriers. Cadmium oxide (CdO) is a narrow-bandgap semiconductor and an important visible-light-responsive photocatalytic material. However, the limited light energy utilization of cadmium oxide alone and the high recombination rate of photogenerated carriers greatly limit its photoelectrochemical water splitting performance.

[0004] To address this issue, cadmium oxide can be co-modified with band-matched semiconductors and metal nanoparticles with plasmon resonance effects. The step-like charge transport channels formed between the band-matched semiconductors can improve the separation efficiency of photogenerated carriers, while the surface plasmon resonance effect of the metal nanoparticles can enhance light utilization, generate hot electron injection, and extend carrier lifetime, thereby improving the photoelectrochemical water splitting performance.

[0005] Cadmium sulfide (CdS) possesses suitable band structure positions, enabling it to form a stepped charge transport channel with cadmium oxide. Aluminum (Al) is the most abundant non-precious metal in the world, inexpensive, and exhibits excellent surface plasmon resonance (SPR) effects from the ultraviolet to near-infrared bands. This invention utilizes the stepped charge transport channel formed by cadmium oxide and cadmium sulfide, along with the SPR effect of non-precious metal aluminum nanoparticles, to prepare a cadmium oxide / cadmium sulfide / aluminum nanostructured photocatalytic material to improve its photoelectrochemical water splitting for electricity generation and hydrogen production. Currently, there are no reports on the use of heterostructured photocatalytic materials formed by co-modifying cadmium oxide nanostructures with cadmium sulfide nanostructures and aluminum nanoparticles for photoelectrochemical water splitting. Summary of the Invention

[0006] The purpose of this invention is to provide a method for preparing cadmium oxide / cadmium sulfide / aluminum nanostructured photocatalytic materials. The cadmium oxide / cadmium sulfide / aluminum nanostructured photocatalytic materials prepared by the method of this invention can provide stepped charge transport channels, generate hot electron injection and prolong carrier lifetime, effectively improve solar energy utilization, suppress photogenerated carrier recombination, and ultimately improve their photoelectrochemical water splitting performance.

[0007] To achieve the above-mentioned objectives, the present invention provides the following technical solution: This invention provides a method for preparing cadmium oxide / cadmium sulfide / aluminum nanostructured photocatalytic materials. Figure 1 This is a flowchart of the preparation method according to an embodiment of the present invention, which includes the following steps: Step 1: Preparation of cadmium oxide flower-like nanostructures using electrodeposition method First, a certain amount of cadmium nitrate tetrahydrate and ammonium chloride were sequentially dissolved in deionized water and stirred with a magnetic stirrer until completely dissolved to obtain an electrolyte. Second, using this electrolyte, a cadmium hydroxide nanostructure was deposited on a clean conductive glass substrate at a certain temperature and voltage for a certain time through a three-electrode electrochemical system. Finally, the obtained cadmium hydroxide nanostructure was calcined and annealed at a certain temperature for a certain time to obtain a cadmium oxide flower-like nanostructure. Step 2: Prepare cadmium oxide / cadmium sulfide nanostructures using chemical bath deposition. First, a certain amount of cadmium acetate dihydrate is dissolved in deionized water and stirred with a magnetic stirrer until completely dissolved. Second, thiourea is added to the above solution and stirred until completely dissolved to obtain a reaction solution. Finally, a conductive glass with cadmium oxide flower-like nanostructures is horizontally immersed in the reaction solution, heated to a certain temperature and held for a certain time to obtain cadmium oxide / cadmium sulfide nanostructures. Step 3: Prepare cadmium oxide / cadmium sulfide / aluminum nanostructured photocatalytic materials using magnetron sputtering. First, a conductive glass on which cadmium oxide / cadmium sulfide nanostructures are grown is fixed on a stage and inserted into a substrate. Second, the vacuum chamber is evacuated and then argon gas is introduced. Finally, under room temperature conditions, the sputtering power and sputtering time are adjusted to sputter aluminum nanoparticles onto the cadmium oxide / cadmium sulfide nanostructures to obtain a cadmium oxide / cadmium sulfide / aluminum nanostructure photocatalytic material.

[0008] Preferably, in step 1, the electrodeposition temperature is 60~80℃, the electrodeposition voltage is -2~-1 volts, the electrodeposition time is 600~900 seconds, the annealing temperature is 350~500℃, and the annealing time is 1~5 hours.

[0009] Preferably, the heating temperature in step 2 is 60~80℃, and the holding time is 60~120 minutes.

[0010] Preferably, in step 3, the sputtering power is 130~150 watts and the sputtering time is 1~30 seconds.

[0011] The method for preparing a cadmium oxide / cadmium sulfide / aluminum nanostructured photocatalytic material according to the present invention belongs to the field of composite photocatalytic material preparation technology, and is specifically applied to the fields of photoelectrochemical water splitting for electricity production and hydrogen production.

[0012] The present invention has the following beneficial effects: (1) This invention cleverly combines electrodeposition, chemical bath deposition and magnetron sputtering to design a three-step synergistic process to prepare a cadmium oxide / cadmium sulfide / aluminum nanostructure photocatalytic material that integrates a stepped charge transport channel and surface plasmon resonance effect. (2) This invention utilizes the synergistic effect of the stepped charge transport channels formed by cadmium oxide and cadmium sulfide and the surface plasmon resonance effect of non-noble metal aluminum to effectively improve the solar energy utilization rate and photogenerated carrier separation efficiency, and significantly enhance the photoelectrochemical water splitting performance of cadmium oxide photocatalyst. At present, there are no reports on the use of cadmium oxide / cadmium sulfide / aluminum nanostructure photocatalytic materials for photoelectrochemical water splitting. (3) The process of this invention is simple and the size of the obtained cadmium oxide / cadmium sulfide / aluminum heterostructure is at the nanoscale. It is a new type of nanostructure photocatalytic material that is suitable for the field of photoelectrochemical water splitting. Attached Figure Description

[0013] Figure 1 This is a flowchart illustrating the preparation process of the cadmium oxide / cadmium sulfide / aluminum nanostructured photocatalytic material according to an embodiment of the present invention.

[0014] Figure 2 The X-ray diffraction pattern and photoelectron spectrum of the cadmium oxide / cadmium sulfide / aluminum nanostructure photocatalytic material prepared in the embodiments of the present invention are shown.

[0015] Figure 3 The image shows a scanning electron microscope image of the cadmium oxide / cadmium sulfide / aluminum nanostructured photocatalytic material prepared in an embodiment of the present invention.

[0016] Figure 4 Transmission electron microscope image of the cadmium oxide / cadmium sulfide / aluminum nanostructured photocatalytic material prepared in an embodiment of the present invention.

[0017] Figure 5 The power generation performance curves of the cadmium oxide / cadmium sulfide / aluminum nanostructured photocatalytic material prepared in the embodiments of the present invention are shown.

[0018] Figure 6 The hydrogen production performance curve of the cadmium oxide / cadmium sulfide / aluminum nanostructure photocatalytic material prepared in the embodiments of the present invention is shown. Detailed Implementation

[0019] The following embodiments further illustrate the above-described content of the present invention in detail. However, it should not be construed as limiting the scope of the present invention to the following embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort, without departing from the principles of the present invention, are within the scope of protection of the present invention.

[0020] Example Step 1: Preparation of cadmium oxide flower-like nanostructures by electrodeposition First, 7.5 mmol of cadmium nitrate tetrahydrate and 3.75 mmol of ammonium chloride were sequentially dissolved in 150 mL of deionized water and stirred with a magnetic stirrer until completely dissolved to obtain an electrolyte. Second, using this electrolyte, a three-electrode electrochemical system (working electrode: conductive glass; reference electrode: silver / silver chloride electrode; counter electrode: platinum wire) was used to deposit cadmium hydroxide nanostructures on the conductive glass surface at 70 °C for 800 seconds under a -1.3 V voltage. The cadmium hydroxide nanostructures were then subjected to a stepwise annealing process: first held at 350 °C for 3 hours, then heated to 500 °C and held for 1 hour, to completely convert cadmium hydroxide into cadmium oxide flower-like nanostructures. Step 2: Preparation of cadmium oxide / cadmium sulfide nanostructures by chemical bath deposition First, 5.6 mmol of cadmium acetate dihydrate was dissolved in 40 mL of deionized water and stirred with a magnetic stirrer until completely dissolved. Second, 10.4 mmol of thiourea was added to the above solution and stirring was continued until completely dissolved to obtain a reaction solution. Finally, a conductive glass with cadmium oxide flower-like nanostructures was horizontally immersed in the reaction solution, heated to 80 °C and held for 90 minutes to obtain cadmium oxide / cadmium sulfide nanostructures. Step 3: Preparation of cadmium oxide / cadmium sulfide / aluminum nanostructured photocatalytic materials by magnetron sputtering First, the conductive glass on which the cadmium oxide / cadmium sulfide nanostructures are grown is fixed on the stage and inserted into the substrate; second, the pressure in the vacuum chamber is evacuated to 1×10⁻⁶. -4 After the pressure was reduced to 1 Pa, argon gas was introduced to maintain the pressure in the vacuum chamber at 1 Pa. Finally, at room temperature, the sputtering power was adjusted to 135 W and the sputtering time was 4 seconds to sputter aluminum nanoparticles onto the cadmium oxide / cadmium sulfide nanostructure, thus obtaining a cadmium oxide / cadmium sulfide / aluminum nanostructure photocatalytic material.

[0021] This invention prepares cadmium oxide / cadmium sulfide / aluminum nanostructured photocatalytic materials through a three-step synergistic process. The core of this invention lies in utilizing the band matching of cadmium oxide and cadmium sulfide to construct a stepped charge transport channel, combined with the surface plasmon resonance effect of aluminum nanoparticles. This effectively improves solar energy utilization and photogenerated carrier separation efficiency, ultimately significantly enhancing the photoelectrochemical water splitting performance of cadmium oxide photocatalysis. The inventive points and specific technical effects of this invention are as follows: (1) The flower-like nanostructure of cadmium oxide is composed of a large number of nanoparticles (see Figure 3 (Scanning electron microscope image) It has an ultra-large specific surface area, which can increase the light absorption area and provide more reactive sites, laying the foundation for the modification of cadmium sulfide and aluminum; (2) Cadmium sulfide grows in the form of hydrangea-like nanostructures on the surface of cadmium oxide flower-like structures (see Figure 3 (Scanning electron microscope image) Cadmium sulfide and cadmium oxide form a stepped charge transport channel. This channel promotes the directional transfer of photogenerated electrons from cadmium sulfide to cadmium oxide, reduces electron-hole recombination, and solves the problem of high recombination rate of single cadmium oxide carriers; (3) Aluminum nanoparticles are uniformly coated on the surface of cadmium oxide / cadmium sulfide (see Figure 4 (Transmission electron microscopy) As a non-noble metal, aluminum nanoparticles exhibit excellent surface plasmon resonance effects from the ultraviolet to near-infrared bands, allowing them to absorb more sunlight and simultaneously generate hot electron injections into cadmium oxide / cadmium sulfide heterostructures, thus extending carrier lifetime; (4) The photocurrent density of the cadmium oxide / cadmium sulfide / aluminum nanostructure photocatalytic material prepared by the method of the present invention reaches 5.2 mA / cm², which is 5.8 times that of pure cadmium oxide; the maximum applied bias photoelectric conversion efficiency (ABPE) reaches 3.9%, which is 5.6 times that of pure cadmium oxide; and the maximum incident photon-electron conversion efficiency (IPCE) reaches 33.7%, which is 2.6 times that of pure cadmium oxide (see [link to original text]). Figure 5 (Electricity generation performance curve); the hydrogen production rate reaches 40.6 μmol / cm² / h, which is 2.2 times that of pure cadmium oxide (see...). Figure 6 (Hydrogen production performance curve).

[0022] Therefore, the photoelectrochemical water splitting electricity generation and hydrogen production performance of the cadmium oxide / cadmium sulfide / aluminum nanostructure photocatalytic material prepared by this invention are significantly improved, and it can be applied to the field of photoelectrochemical water splitting.

[0023] Table 1 lists the electrochemical hydrogen production performance of the cadmium oxide / cadmium sulfide / aluminum nanostructure photocatalytic material prepared by the method of this invention, compared with that of cadmium oxide. It can be seen that the performance of the cadmium oxide / cadmium sulfide / aluminum nanostructure photocatalytic material is significantly improved. The photocurrent density, maximum applied bias photoelectric conversion efficiency, maximum incident photon-electron conversion efficiency, and hydrogen production rate are 5.8, 5.6, 2.6, and 2.2 times that of pure cadmium oxide, respectively. (Table 1 follows.) Table 1. Comparison of electricity generation and hydrogen production performance of cadmium oxide / cadmium sulfide / aluminum nanostructured photocatalytic materials Serial Number Cadmium oxide / cadmium sulfide / aluminum Performance indicators Compared with cadmium oxide 1 Photocurrent density 5.2 mA / cm² 5.8 times 2 Maximum applied bias photoelectric conversion efficiency 3.9% 5.6 times 3 Maximum incident photon-electron conversion efficiency 33.7% 2.6 times 4 hydrogen production rate 40.6 micromoles / cm² / hour 2.2 times

[0024] Experiments and Data The following are the composition, morphology characterization, and photoelectrochemical water splitting electricity generation and hydrogen production performance test results of the cadmium oxide / cadmium sulfide / aluminum nanostructure photocatalytic materials prepared in the examples: Figure 2 The X-ray diffraction (XRD) and photoelectron spectroscopy (PES) spectra are presented. The XRD shows that the diffraction peaks of cadmium oxide match those of cubic rock salt cadmium oxide (JCPDS No. 65–2908), while the diffraction peaks of cadmium sulfide match those of hexagonal wurtzite cadmium sulfide (JCPDS No. 41–1049). The XRD PES spectrum indicates the presence of cadmium, sulfur, oxygen, and aluminum in the cadmium oxide / cadmium sulfide / aluminum nanostructured photocatalytic material. This demonstrates that cadmium sulfide and aluminum were successfully grown on cadmium oxide. Figure 3 These are low- and high-magnification scanning electron microscope images. As can be seen from the images, cadmium oxide consists of flower-like structures formed by aggregates of nanoparticles; cadmium sulfide exhibits hydrangea-like nanostructures with surface protrusions. Figure 4 These are transmission and high-resolution transmission electron microscopy images. The images further reveal that the surface of the cadmium oxide / cadmium sulfide nanostructure is covered by a thin film formed by aluminum nanoparticles. Figure 5 The figure shows the photoelectric performance curves. As can be seen from the figure, the photocurrent of the cadmium oxide / cadmium sulfide / aluminum nanostructure photocatalyst material reaches 5.2 mA / cm², approximately 5.8 times that of pure cadmium oxide. Compared to pure cadmium oxide, the photocurrent density of the cadmium oxide / cadmium sulfide / aluminum nanostructure photocatalyst material increases more rapidly with increasing voltage. The maximum applied bias photoelectric conversion efficiency (ABPE) of the cadmium oxide / cadmium sulfide / aluminum nanostructure photocatalyst material reaches 3.9%, 5.6 times that of pure cadmium oxide; the maximum incident photon-electron conversion efficiency (IPCE) reaches 33.7%, 2.6 times that of pure cadmium oxide. Therefore, the photoelectric performance of the cadmium oxide / cadmium sulfide / aluminum nanostructure photocatalyst material prepared in this invention is significantly improved. Figure 6 The figure shows the hydrogen production performance curve. As can be seen from the figure, the hydrogen production capacity of the cadmium oxide / cadmium sulfide / aluminum nanostructure photocatalytic material increases with time; the hydrogen production rate reaches 40.6 μmol / cm² / hour, which is approximately 2.2 times that of pure cadmium oxide; the cyclic hydrogen production capacity is stable within 1–4 hours; and the performance of electricity generation and hydrogen production is stable over long periods. Therefore, the photocatalytic water splitting hydrogen production performance of the cadmium oxide / cadmium sulfide / aluminum nanostructure photocatalytic material prepared in this invention is significantly improved.

Claims

1. A method for preparing a cadmium oxide / cadmium sulfide / aluminum nanostructured photocatalytic material, characterized in that, The specific preparation steps are as follows: Step 1: Preparation of cadmium oxide flower-like nanostructures using electrodeposition method First, a certain amount of cadmium nitrate tetrahydrate and ammonium chloride were sequentially dissolved in deionized water and stirred with a magnetic stirrer until completely dissolved to obtain an electrolyte. Second, using this electrolyte, a cadmium hydroxide nanostructure was deposited on a clean conductive glass substrate at a certain temperature and voltage for a certain time through a three-electrode electrochemical system. Finally, the obtained cadmium hydroxide nanostructure was calcined and annealed at a certain temperature for a certain time to obtain a cadmium oxide flower-like nanostructure. Step 2: Prepare cadmium oxide / cadmium sulfide nanostructures using chemical bath deposition. First, a certain amount of cadmium acetate dihydrate is dissolved in deionized water and stirred with a magnetic stirrer until completely dissolved. Second, thiourea is added to the above solution and stirred until completely dissolved to obtain a reaction solution. Finally, a conductive glass with cadmium oxide flower-like nanostructures is horizontally immersed in the reaction solution, heated to a certain temperature and held for a certain time to obtain cadmium oxide / cadmium sulfide nanostructures. Step 3: Prepare cadmium oxide / cadmium sulfide / aluminum nanostructured photocatalytic materials using magnetron sputtering. First, the conductive glass on which the cadmium oxide / cadmium sulfide nanostructures are grown is fixed on the stage and inserted into the substrate; second, the vacuum chamber is evacuated and then argon gas is introduced. Finally, under room temperature conditions, by adjusting the sputtering power and sputtering time, aluminum nanoparticles were sputtered onto the cadmium oxide / cadmium sulfide nanostructure to obtain a cadmium oxide / cadmium sulfide / aluminum nanostructure photocatalytic material.

2. The preparation method of the cadmium oxide / cadmium sulfide / aluminum nanostructure photocatalytic material according to claim 1, characterized in that, In step 1, the electrodeposition temperature is 60-80℃, the voltage is -2 to -1 volt, the time is 600-900 seconds, the annealing temperature is 350-500℃, and the annealing time is 1-5 hours.

3. The preparation method of the cadmium oxide / cadmium sulfide / aluminum nanostructure photocatalytic material according to claim 1, characterized in that, In step 2, the heating temperature is 60-80℃ and the holding time is 60-120 minutes.

4. The method for preparing the cadmium oxide / cadmium sulfide / aluminum nanostructured photocatalytic material according to claim 1, characterized in that, In step 3, the sputtering power is 130-150 watts and the sputtering time is 1-30 seconds.

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