A SiC photocatalyst with tubular morphology

Abstract

This invention discloses a SiC photocatalyst with a tubular morphology, its preparation method, and its applications, belonging to the field of photocatalyst preparation technology. The tubular SiC photocatalyst is synthesized from horsetail plant material through high-temperature calcination. This invention utilizes the lignin of horsetail plant itself as a morphological template during high-temperature calcination, ensuring the retention of the tubular morphology after calcination. The raw materials for this photocatalyst are inexpensive and readily available, the preparation method is convenient and feasible, and compared with commercial SiC materials, its photocatalytic reduction performance of carbon dioxide is significantly enhanced.

Description

Technical Field

[0001] This invention belongs to the field of photocatalyst preparation technology, specifically relating to a SiC photocatalyst with a tubular morphology, its preparation method, and its application in the photocatalytic reduction of carbon dioxide. Background Technology

[0002] The continued over-burning of fossil fuels has led to massive carbon dioxide emissions and a severe energy crisis. Solar photocatalysis is currently the most ideal method to solve global energy problems and environmental degradation. Over the past few decades, many types of semiconductor photocatalytic materials have been used in this field. However, current photocatalysts still suffer from problems such as low quantum efficiency, narrow light response range, poor stability, and high cost. Therefore, effectively converting CO2 molecules into value-added hydrocarbon fuels is key to mitigating the greenhouse effect and energy crisis. Currently, metal-free photocatalysts composed of non-metallic elements such as carbon, silicon, nitrogen, and boron are attracting increasing attention. Silicon carbide (SiC), for example, is a semiconductor that is resistant to corrosion and exhibits excellent sustainability and cost-effectiveness. Inoue et al. reported that photoexcited electrons in the negative conduction band (CB) of SiC have a stronger ability to reduce CO2. Silicon carbide (SiC) is an n-type semiconductor with high electron mobility and a negative conduction band position, resulting in a high reduction potential. These characteristics determine that SiC materials have a stronger reduction ability compared to other semiconductor materials, making it a promising candidate for CO2 reduction reactions. Currently reported methods for synthesizing SiC photocatalysts mainly include the sol-gel method, high-temperature magnesothermic reduction method, and high-pressure solvothermal method. While these methods can yield relatively pure SiC, the synthesis steps are cumbersome and do not align with the principles of green chemistry. Therefore, this work aims to achieve a breakthrough in SiC synthesis methods by shifting the raw material source to nature. Since the plant *Equisetum hyemale* contains a high proportion of carbon and silicon, and lacks interference from other elements, we attempted to carbonize this plant through high-temperature argon calcination, followed by thorough grinding and then calcination in air to remove carbon. Finally, we used NaOH to remove the SiO2 impurities generated during the process, thereby obtaining biomass-synthesized SiC. This synthesis method simplifies the SiC synthesis steps and truly achieves natural raw material sourcing, low cost, and adherence to the principles of green and sustainable development. Furthermore, we found that the abundant lignin in *Equisetum hyemale* can serve as a morphological template. SiC prepared using this method retains the original tubular morphological structure of *Equisetum hyemale*, increasing surface active sites and enhancing CO2 adsorption capacity compared to commercial SiC, thus facilitating the smooth progress of the CO2 reduction reaction. Summary of the Invention

[0003] To address the shortcomings of current technologies, the present invention aims to provide a SiC photocatalyst material based on the plant horsetail and its preparation method, for photocatalytic carbon dioxide reduction reaction. The raw materials for this composite photocatalyst are inexpensive and readily available, and the preparation scheme is convenient and feasible. Compared with the photocatalytic carbon dioxide reduction performance of commercial SiC materials, the carbon dioxide reduction performance of the SiC tubular photocatalyst material is significantly enhanced.

[0004] To achieve the above objectives, the present invention adopts the following technical solution:

[0005] A method for preparing a SiC photocatalyst material with a tubular morphology includes the following steps:

[0006] (1) Clean an appropriate amount of horsetail plant and dry it overnight;

[0007] (2) Grind the dried plant horsetail obtained in step (1), and after thorough grinding, transfer it to a tube furnace for carbonization, and then transfer it to a muffle furnace for decarbonization;

[0008] (3) The gray-green material obtained in step (2) is stirred with NaOH solution to remove most of the SiO2 impurities. After centrifugation, washing and drying, gray-green SiC tubular material is obtained.

[0009] Preferably, in step (1), the weight of the plant horsetail is 2g, the drying temperature is 120℃, and the drying time is 24h.

[0010] Preferably, in step (2), the calcination temperature in the tube furnace is 1500℃, the calcination time is 8h, and the calcination atmosphere is argon; the calcination conditions in the muffle furnace are: calcination temperature is 800℃, the calcination time is 6h, and the calcination atmosphere is air.

[0011] Preferably, in step (3), the SiC tubular material purification method includes the following steps: stirring with a 20% NaOH solution (the mass ratio of NaOH to H2O is 4:1) for 24 hours.

[0012] The beneficial effects of this invention are as follows: The tubular SiC photocatalyst material prepared by this simple high-temperature calcination method simplifies the SiC synthesis process and truly achieves natural raw material sourcing, low cost, and adherence to the concept of green and sustainable development. Furthermore, we found that the SiC prepared by this method also possesses a tubular morphology, which, compared to commercial SiC, increases the number of surface active sites, enhances CO2 adsorption capacity, and facilitates the smooth progress of the CO2 reduction reaction. Attached Figure Description

[0013] Figure 1 The image shows the XRD pattern of the SiC tubular material prepared by the synthesis method in Example 1.

[0014] Figure 2 This is a SEM image of the SiC tubular material prepared by the synthesis method in Example 1.

[0015] Figure 3 This is a TEM image of the SiC tubular material prepared by the synthesis method in Example 1.

[0016] Figure 4 The image shows an HRTEM image of the SiC tubular material prepared by the synthesis method in Example 1.

[0017] Figure 5 The activity test was compared between the SiC tubular material prepared by the synthesis method in Example 1 and the commercial SiC material.

[0018] Figure 6 The DRS bandgap diagram of the SiC tubular material prepared by the synthesis method in Example 1 is shown. Detailed Implementation

[0019] The present invention will be further illustrated below with reference to embodiments. These embodiments are for illustrative purposes only and do not limit the scope of the invention.

[0020] This invention proposes a method for preparing a catalyst by using lignin from the plant horsetail as a morphological template during high-temperature calcination, ensuring that the material retains its tubular morphology after calcination. The photocatalytic activity of the catalyst material was tested by conducting a carbon dioxide reduction reaction in a gas-solid phase system under full-band xenon lamp irradiation.

[0021] Physical property characterization methods for SiC photocatalyst materials with tubular morphology: X-ray powder diffraction (XRD) was used to analyze the composition and crystal phase structure of the catalyst material, scanning electron microscopy (SEM) and transmission electron microscopy (TEM) were used to observe the morphology and particle size of the catalyst material, and DRS was used to test the band gap position of the catalyst.

[0022] Comparative Example 1: Commodity SiC

[0023] Example 1:

[0024] A method for preparing SiC photocatalyst material with tubular morphology:

[0025] (1) Clean 2g of Equisetum hyemale and dry it at 120℃ for 24 hours;

[0026] (2) Grind the dried horsetail obtained in step (1), and after thorough grinding, transfer it to a tube furnace for carbonization (temperature 1500℃, time 8h, atmosphere argon), and then transfer it to a muffle furnace for decarbonization (temperature 800℃, time 6h, atmosphere air).

[0027] (3) The gray-green material obtained in step (2) was stirred with a 20% NaOH solution for 24 hours to remove most of the SiO2 impurities. After centrifugation, washing and drying, gray-green SiC tubular material was obtained.

[0028] Figure 1 The XRD pattern of the SiC tubular material prepared by the synthesis method in Example 1 is shown; the characteristic peaks correspond to 2H-SiC (PDF#29-1126) and 3C-SiC (PDF#29-1129), respectively. Figure 2 The image shows a SEM image of the SiC tubular material prepared by the synthesis method in Example 1; its morphology consists of tubular structures of varying sizes, ranging from 4 to 5 μm. Figure 3 The image shows a TEM image of the SiC tubular material prepared by the synthesis method in Example 1; its morphology is a tubular material with a diameter of 150 nm. Figure 4 The image shows an HRTEM image of the SiC tubular material prepared by the synthesis method in Example 1. It can be observed that there are obvious heterogeneous structure stripes of 2H and 3C phase silicon carbide, which further proves that it has a heterogeneous structure.

[0029] Application Comparative Examples / Examples:

[0030] The specific steps of the gas-solid phase photocatalytic carbon dioxide reduction experiment are as follows:

[0031] The gas-solid phase photocatalytic carbon dioxide reduction performance evaluation experiment of this invention was conducted in a Schlenk quartz reaction tube with a volume of approximately 190 mL. First, 5 mg of photocatalyst material was dispersed in 1 mL of deionized water. Then, the dispersion was dropped onto a 1.5*4 cm glass fiber filter paper, ensuring the photocatalyst covered the entire sheet. Next, the glass fiber filter paper was dried in a drying oven at 60 °C for 30 min before being loaded into the quartz reactor. Then, the quartz reactor was sealed, and high-purity CO2 gas was sequentially injected into the reactor, purging for at least 40 min to ensure the quartz tube was filled with high-purity CO2 gas. Next, 20 μL of pure water was injected into the quartz reactor through a rubber septum. The quartz reaction tube was fixed to a stirrer, and the glass fiber filter paper loaded with the photocatalyst material in the quartz reactor was irradiated with a 300 W xenon lamp for 2 hours. Afterward, a 0.5 mL sample was taken for testing.

[0032] Experimental procedure:

[0033] Two hours after irradiation with a xenon lamp, 0.5 mL of gaseous product was taken from a quartz tube using a gas chromatograph and injected into a gas chromatograph (GC Agilent 7890B) to detect and analyze the carbon dioxide reduction products.

[0034]

[0035] The above data demonstrates that, compared with commercial SiC materials, the SiC photocatalyst material with tubular morphology in this embodiment exhibits more efficient carbon dioxide reduction performance, resulting in a significant increase in the amount of carbon monoxide generated as a photocatalytic carbon dioxide reduction product.

[0036] It should be understood that the above embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Furthermore, it should be understood that after reading the contents of this invention, those skilled in the art can make various alterations or modifications to the invention, and these equivalent forms also fall within the scope defined by this invention.

Claims

1. The application of a SiC photocatalyst with a tubular morphology in the photocatalytic reduction of carbon dioxide, characterized in that: The SiC photocatalyst with tubular morphology is synthesized from the plant horsetail through high-temperature calcination. The SiC photocatalyst with tubular morphology exhibits obvious heterogeneous structure stripes of 2H and 3C phase silicon carbide, which is heterogeneous. The preparation method of the SiC photocatalyst with tubular morphology includes the following steps: (1) Clean and dry the horsetail plant; (2) Carbonize the dried plant horsetail, grind it thoroughly and then remove the carbon; (3) Add NaOH solution and stir, centrifuge, wash and dry to obtain the SiC photocatalyst with tubular morphology; In step (2), the carbonization temperature is 1500℃, the time is 8h, and the atmosphere is argon; the decarbonization temperature is 800℃, the time is 6h, and the atmosphere is air.

2. The application according to claim 1, characterized in that: In step (1), the drying temperature is 120℃ and the time is 24h.

3. The application according to claim 1, characterized in that: In step (3), the solution is stirred with a 20% NaOH solution for 24 hours.

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