Photocatalyst for capturing and converting low concentration carbon dioxide in air

Abstract

Disclosed are a photocatalyst for capturing and converting low-concentration carbon dioxide in the air, and a method for capturing and photo-converting carbon dioxide in the air by using same. The photocatalyst for capturing and converting carbon dioxide may comprise bismuth oxyhalide in which at least one metal is supported and which has oxygen vacancies.

Description

Photocatalysts for capturing and converting low-concentration carbon dioxide from the atmosphere

[0001] The present invention relates to a photocatalyst for capturing and converting carbon dioxide, which can directly capture and convert low-concentration carbon dioxide under actual atmospheric conditions into a high-value-added material, and a method for capturing and photoconverting carbon dioxide in the atmosphere using the same.

[0002] Carbon dioxide emissions are projected to continue increasing, causing global temperatures to rise by 2.1℃ by 2100. To address this issue, active research is underway into developing technologies to reduce carbon dioxide emissions. However, it is realistically difficult to drastically reduce carbon dioxide emissions in a short period of time. Carbon capture and storage (CCS) technology, or CCU, is currently being adopted as a viable means of reducing carbon dioxide emissions to achieve sustainable growth, and direct air CO2 capture (DAC) technology is currently being demonstrated.

[0003] However, these technologies primarily utilize metal-organic frameworks (MOFs) and zeolites as capture agents, raising concerns about the consumption of water resources and additional energy consumption, such as heat, for the regeneration of capture materials. Furthermore, due to their competitive adsorption mechanism, they are significantly affected by oxygen and moisture in the air, and MOFs lose their durability at high temperatures, posing challenges when applied to continuously remove carbon dioxide from the atmosphere.

[0004] One object of the present invention is to provide a photocatalyst for capturing and converting carbon dioxide, which can selectively capture low-concentration carbon dioxide in the atmosphere under conditions containing oxygen and moisture and convert it into a high value-added compound using sunlight.

[0005] Another object of the present invention is to provide a method for capturing and photoconverting carbon dioxide in the atmosphere using the photocatalyst.

[0006] In one aspect, the present invention provides a photocatalyst for carbon dioxide capture and conversion comprising a bismuth oxyhalide supported with one or more metals and having oxygen vacancies.

[0007] In one embodiment, the metal may be selected from Cu, Fe, Co, Ni, Mn, Ru, Pt, Au, and Ag.

[0008] In one embodiment, the metal may be included in an amount of 0.01 to 2 wt% relative to the total weight of the catalyst.

[0009] In one embodiment, the metal includes Cu and Fe, and the Cu may be included in an amount of 0.01 to 0.5 wt% and the Fe may be included in an amount of 0.3 to 1 wt% relative to the total weight of the catalyst.

[0010] In one embodiment, the photocatalyst can selectively capture carbon dioxide of 1000 ppm or less in the atmosphere under dark conditions, and can convert the captured carbon dioxide into CO or CH4 when irradiated with light.

[0011] In another aspect, the present invention provides a method for capturing and photoconverting carbon dioxide in the atmosphere, comprising a first step of selectively capturing carbon dioxide in the atmosphere using the photocatalyst, and a second step of irradiating light on the catalyst in which carbon dioxide is captured to reduce it into a photoconversion product.

[0012] In one embodiment, the first step may be performed under dark conditions.

[0013] In one embodiment, the photoconversion product may comprise CO or CH4.

[0014] The photocatalyst according to the present invention has improved carbon dioxide adsorption and catalytic activity due to the oxygen vacancy activity of bismuth oxyhalide, and can additionally improve the photoconversion rate of captured carbon dioxide due to the structure in which one or more metals are supported.

[0015] In addition, by using the photocatalyst of the present invention, low concentration (approximately 450 ppm) carbon dioxide in the atmosphere can be selectively adsorbed under dark conditions (night) containing oxygen and moisture, and the adsorbed carbon dioxide can be photoconverted under light conditions (daytime) to be reduced into a high value-added material.

[0016] FIG. 1 is a drawing showing a photocatalyst for carbon dioxide capture and conversion according to an embodiment of the present invention.

[0017] Figure 2 is a schematic diagram showing a method for capturing and converting carbon dioxide in the atmosphere according to an embodiment of the present invention.

[0018] Figures 3 to 13 are drawings showing experimental results according to experimental examples of the present invention.

[0019] Hereinafter, embodiments of the present invention will be described in detail with reference to the attached drawings. The present invention may be modified in various ways and may take various forms. Therefore, specific embodiments are illustrated in the drawings and described in detail in the text. However, this is not intended to limit the present invention to a specific disclosed form, but should be understood to include all modifications, equivalents, and substitutes included in the spirit and technical scope of the present invention. In describing each drawing, similar reference numerals are used to indicate similar components. In the attached drawings, the dimensions of structures are shown larger than actual size to ensure clarity of the present invention.

[0020] The terminology used in this application is only used to describe specific embodiments and is not intended to limit the present invention. The singular expression includes the plural expression unless the context clearly indicates otherwise. In this application, the terms "comprise" or "have" should be understood to indicate the presence of a feature, number, step, operation, component, or combination thereof described in the specification, but do not preclude the possibility of the presence or addition of one or more other features, numbers, steps, operations, components, or combinations thereof.

[0021] Unless otherwise defined, all terms used herein, including technical or scientific terms, have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. Terms defined in commonly used dictionaries should be interpreted as having a meaning consistent with their meaning in the context of the relevant technology, and will not be interpreted in an idealized or overly formal sense unless explicitly defined herein.

[0022] FIG. 1 is a drawing showing a photocatalyst for carbon dioxide capture and conversion according to an embodiment of the present invention.

[0023] Referring to FIG. 1, a photocatalyst for carbon dioxide capture and conversion according to an embodiment of the present invention may include a bismuth oxyhalide having one or more metals supported thereon and oxygen vacancies.

[0024] The bismuth oxyhalide of the present invention can be represented by BiOX (X = Cl, Br, I). In addition, the bismuth oxyhalide of the present invention can have an oxygen vacancy. A bismuth oxyhalide activated by an oxygen vacancy can adsorb carbon dioxide in the atmosphere about three times better than a bismuth oxyhalide without an oxygen vacancy.

[0025] Meanwhile, the bismuth oxyhalide having an oxygen vacancy of the present invention may support one or more metals. As the metal is supported, the carbon dioxide capture performance of the catalyst is enhanced, and the photoconversion performance can be improved by about 2.5 times or more compared to a bismuth oxyhalide activated by an oxygen vacancy.

[0026] In one embodiment, the metal may be selected from Cu, Fe, Co, Ni, Mn, Ru, Pt, Au, and Ag, but is not particularly limited. In addition, in order to improve the selective capture and photoconversion performance of low-concentration carbon dioxide (about 1000 ppm or less) in the atmosphere, the metal may be included in an amount of 0.01 to 2 wt% relative to the total weight of the catalyst, but is not limited thereto, and may be included in an appropriate amount depending on each metal.

[0027] Preferably, the photocatalyst may include a bimetallic metal. In this case, it may include two metals selected from the above-mentioned metals, and most preferably, it may include Cu and Fe. In addition, to obtain optimal carbon dioxide capture and photoconversion performance, Cu may be included in an amount of 0.01 to 0.5 wt%, and Fe may be included in an amount of 0.3 to 1 wt%, relative to the total weight of the catalyst.

[0028] The photocatalyst of the present invention can selectively capture carbon dioxide of 1000 ppm or less in the atmosphere under dark conditions, and can convert the captured carbon dioxide into CO or CH4 when irradiated with light.

[0029] More specifically, the photocatalyst of the present invention can selectively adsorb low-concentration (approximately 450 ppm) carbon dioxide in the atmosphere under dark conditions (night) containing oxygen and moisture, and photoconvert the adsorbed carbon dioxide under light conditions (daytime) to reduce it into CO or CH4, which are high value-added substances.

[0030]

[0031] Figure 2 is a schematic diagram showing a method for capturing and converting carbon dioxide in the atmosphere according to an embodiment of the present invention.

[0032] Referring to FIG. 2, a method for capturing and photoconverting carbon dioxide in the atmosphere according to an embodiment of the present invention may include a first step of selectively capturing carbon dioxide in the atmosphere using the photocatalyst of the present invention, and a second step of irradiating light on the catalyst in which carbon dioxide is captured to reduce it into a photoconversion product.

[0033] The first step is to selectively capture low-concentration carbon dioxide in the atmosphere using the photocatalyst of the present invention. This first step can be performed under dark conditions. The photocatalyst of the present invention can effectively adsorb carbon dioxide even in a typical atmospheric environment containing oxygen, moisture, and a low concentration of carbon dioxide (approximately 450 ppm).

[0034] The second step is to irradiate light on the catalyst in which carbon dioxide is captured to reduce it into a photoconversion product. Here, the light irradiation can be sunlight or light of the same or similar wavelength as sunlight. For example, AM 1.5 (100 mW cm -2 ) can be irradiated with light. Meanwhile, by the irradiation with light, carbon dioxide can be reduced to a photoconversion product including CO or CH4.

[0035] According to the present invention, low-concentration (approximately 450 ppm) carbon dioxide in the atmosphere can be selectively adsorbed under dark conditions (night) containing oxygen and moisture, and the adsorbed carbon dioxide can be photoconverted under light conditions (daytime) to be reduced into a high value-added material.

[0036] Hereinafter, embodiments of the present invention will be described in detail. However, the embodiments described below are merely some embodiments of the present invention, and the scope of the present invention is not limited to the embodiments described below.

[0037]

[0038] [Example 1: Preparation of bismuth oxyhalide (Pure BiOX(X=Cl, Br, I))]

[0039] Add 5 mmol of Bi(NO3)3·5H2O to 50 mL of distilled water (DI water) and completely dissolve through ultrasonic treatment for more than 10 minutes. Add 5 mmol of NaX (X=Cl, Br, I) respectively and stir for 30 minutes. Transfer the completely dissolved solution to a 100 mL PTFE liner and perform hydrothermal synthesis at 160°C for 16 hours. Once the reaction is complete and cooled to room temperature, wash several times with water and ethanol. Centrifuge to obtain powder and dry in an oven at 60°C for more than 12 hours.

[0040] [Example 2: Preparation of bismuth oxyhalide activated by oxygen vacancies (Ov BiOX)]

[0041] Add Bi(NO3)3·5H2O (5 mmol) to 50 mL of ethylene glycol solution and completely dissolve through ultrasonication for more than 10 minutes. Add 5 mmol of NaX (X=Cl, Br, I) each and stir for 30 minutes. Add 0-2 mL of 1M HX (X=Cl, Br, I) each and stir for 5 minutes. The completely dissolved solution is placed in a 100 mL PTFE liner and hydrothermally synthesized at 160°C for 16 hours. After the reaction is complete and cooled to room temperature, wash several times with water and ethanol. After obtaining powder using a centrifuge, dry it in an oven at 60°C for more than 12 hours. Heat-treat the dried powder at 300°C (10°C / min) for 1 hour in an Ar atmosphere to remove trace organic matter.

[0042] [Example 3: Preparation of bismuth oxyhalide activated by metal-bonded oxygen vacancies (M / Ov BiOX)]

[0043] To bond metal to the Ov BiOX catalyst manufactured according to Example 2, 400 mg Ov BiOX was placed in a PTFE beaker and 60 mL of distilled water was added. After adding 0.01 to 3 wt% of the metal precursor, the mixture was immersed in a preheated 90°C constant temperature water bath and stirred for 1 hour and 30 minutes. After the reaction was completed, it was cooled to room temperature, washed with water, separated using a centrifuge, and dried in an oven at 60°C for more than 12 hours.

[0044] [Example 4: Preparation of bismuth oxyhalide activated by oxygen vacancies bonded between two metals (M1M2 / Ov BiOX)]

[0045] To bond other metals to the M / Ov BiOX catalyst manufactured according to Example 3, 400 mg of M / Ov BiOX was placed in a PTFE beaker and 60 mL of distilled water was added. After adding 0.01 to 3 wt% of the metal precursor, the mixture was immersed in a preheated 90°C constant temperature water bath and stirred for 1 hour and 30 minutes. After the reaction was completed, the mixture was cooled to room temperature, washed with water, separated using a centrifuge, and dried in an oven at 60°C for more than 12 hours.

[0046]

[0047] [Experimental Example 1: Catalyst Characteristics Evaluation]

[0048] In order to analyze the crystal structure of the catalysts according to Examples 1 to 4, the powder form of Pure BiOCl (Example 1), Ov BiOCl (Example 2) and CuFe / Ov BiOCl (Example 4) was measured using an EMPUREAN device from PANalytical by applying Cu-Kα radiation (40 kV, 30 mA) with a wavelength of 1.5406 Å.

[0049] Referring to the result, Fig. 4, it can be seen that it matches well with BiOCl (JCPDS 06-0249). The diffraction peak of Ov-BiOCl with activated oxygen vacancies showed a broadening pattern with lower intensity and wider peak width compared to the pure BiOCl catalyst. In addition, CuFe / Ov BiOCl, each supporting CuFe ions, did not show significant changes in XRD.

[0050] Meanwhile, in order to measure the composition and components of the catalyst surface, a ThermoFisher (NEXSA) device was used to measure the powder form of Pure BiOCl (Example 1), Ov BiOCl (Example 2), and CuFe / Ov BiOCl (Example 4) by adding Al-Kα (1486.6 eV). The surface element composition of the prepared samples was analyzed to show the composition of Bi, Cl, and O elements, and the composition of Cu and Fe elements was also confirmed in CuFe / Ov BiOCl.

[0051] Looking at Figure 5 showing the results, first comparing the Bi 4f peaks, the peaks at 159.2 and 164.5 eV are Bi 4f 7 / 2 and Bi 4f 5 / 2 Two peaks appeared, and Ov BiOCl, which activated the oxygen vacancy, shifted by 0.2 eV to lower binding energy (159 and 164.3 eV), which is due to the oxygen vacancy of Bi (3-x)+ This is a phenomenon caused by formation. In the Cl 2p spectrum, Cl 2p 3 / 2 and Cl 2p 1 / 2 Two peaks belonging to were identified. The new peak appearing at a higher binding energy than the O 1s peak of Ov BiOCl may be due to oxygen coordination such as OH or adsorbed oxygen. This also suggests the presence of oxygen vacancies. It is clearly seen that the contribution of Bi-O is reduced in BiOCl where Ov is formed due to the removal of oxygen atoms linked to Bi atoms. In Fig. 5(d), the elements were confirmed to be well supported by Cu and Fe ions in CuFe / Ov BiOCl.

[0052] Next, the color change of the catalyst after surface modification was observed and the light absorption range of the catalyst was measured using an analyzer from Shimadzu. BaSO4 (Barium sulfate) was used as a reference first, and the light absorption spectrum in the wavelength range of 200 nm to 900 nm was measured in the form of catalyst powder.

[0053] As a result, as can be seen from the catalyst color in Fig. 6, the color of the catalyst changed to dark brown (Ov BiOCl) due to the activation of oxygen vacancies. In addition, as can be seen from the DRS, the absorption in the visible and infrared wavelength ranges of the catalyst with activated oxygen vacancies was significantly increased compared to the conventional BiOCl. The catalyst supporting CuFe ions did not show a significant difference from Ov BiOCl in catalyst color and DRS.

[0054] Meanwhile, CuFe / Ov BiOCl sample powder was measured using a field emission transmission electron microscope (FE-TEM) (200 kV) to observe images of ultrafine regions and analyze components and structures of catalysts according to Examples 1 to 4.

[0055] As a result, the (001) and (101) lattices of BiOCl were confirmed in TEM analysis, similar to the crystal phase confirmed in XRD (Fig. 7a). In addition, it was confirmed that metal clusters were attached to the surface in Figs. 7(b) and (c). The presence of Bi, O, Cl, Cu, and Fe elements was confirmed through EDS analysis, and the BiOCl catalyst was confirmed through TEM, and it can be seen that Cu and Fe were well supported.

[0056]

[0057] [Experimental Example 2: Atmospheric Carbon Dioxide Adsorption and Conversion Experiment]

[0058] To evaluate the carbon dioxide adsorption and conversion performance in the atmosphere, an actual atmospheric condition of approximately 0.05% carbon dioxide (CO2) / air atmosphere (Air Balance) was used. 150 mg of the catalyst according to Example 4 was applied to a 3 cm wide 2 It was filled into the sample holder and placed on the bottom of a stainless steel reactor of about 120 mL. Air was flowed at 200℃ for 12 hours for surface pretreatment (removal of carbon and organic matter). The concentration of carbon dioxide and air was controlled by adjusting the flow rate with a mass flow controller (MFC), and the humidity was maintained at ±45% by passing it through an impinger containing water. This mixed gas was put in a sampling gas bag in advance, and after the pretreatment was completed, the inside of the reactor was made vacuum and the reactor was filled using the gas bag that was placed in advance.

[0059] Carbon dioxide was captured for 2 hours to check the change in captured concentration and light source (sunlight, AM 1.5, 100 mW cm -2 ) was added and the gas inside the reactor was sampled for a certain period of time to confirm the substances and amounts produced. The gas was decomposed and the amount produced was confirmed by quantitatively determining carbon monoxide and carbon dioxide using GC-FID (YL). (See Fig. 3)

[0060]

[0061] [Experimental Example 3: Results of an atmospheric carbon dioxide adsorption and conversion experiment]

[0062] Comparison of atmospheric carbon dioxide capture and conversion using pure BiOCl and Ov BiOCl catalysts.

[0063] Figure 8 illustrates the results of atmospheric carbon dioxide capture and conversion using pure BiOCl and Ov BiOCl catalysts activated with oxygen vacancies. (a) shows the capture result under approximately 0.05% carbon dioxide conditions in an oxygen-containing air atmosphere similar to atmospheric carbon dioxide conditions, and (b) and (c) show the concentrations of carbon monoxide and methane, which are products converted by sunlight using the captured carbon dioxide.

[0064] The results show that the carbon dioxide capture rate of the catalyst activated by oxygen vacancies was 150 ppmv, which is about three times higher than that of Pure BiOCl. It was confirmed that carbon dioxide was selectively and relatively better adsorbed due to the activated portion by oxygen vacancies. In addition, the photoconversion product of the captured carbon dioxide was more than three times higher for the Ov BiOCl catalyst than for Pure BiOCl.

[0065] Evaluation of the capture performance of Ov BiOCl according to atmospheric carbon dioxide concentration and humidity conditions

[0066] Figure 9 shows the results of evaluating the carbon dioxide capture performance of the Ov BiOCl catalyst at atmospheric carbon dioxide concentrations (0.05 to 1%). As a result, it was confirmed that at 0.1% (1000 ppmv), approximately 250 ppmv of capture and photoconversion products were 15 ppmv and 2 ppmv of CO and CH4, respectively. In addition, at 1% (10,000 ppmv) carbon dioxide concentration, approximately 1200 ppmv of capture and photoconversion products were 18 ppmv and 3 ppmv of CO and CH4, respectively.

[0067] The difference in capture amount and photoconversion product was compared according to the concentration of carbon dioxide in the atmosphere, and the results showed that capture and photoconversion performance tended to increase as the concentration of carbon dioxide increased.

[0068] Next, the carbon dioxide capture and conversion performance in the atmosphere was evaluated according to humidity. As a result, there was no significant difference in carbon dioxide capture amount depending on humidity. Selective carbon dioxide adsorption appears to be unaffected by competition with water. However, in terms of photoconversion performance, the highest product concentrations of CO and CH4 were observed at 85% RH, a high humidity. This difference is attributed to the H generated on the surface as water dissociates.

[0069] Comparison of atmospheric carbon dioxide capture and conversion with M / Ov BiOCl

[0070] Figures 10(a)-(c) show the results of comparing the carbon dioxide capture and conversion performance of catalysts loaded with Cu, Fe, and Co on an Ov BiOCl catalyst, respectively. Performance was compared by loading various metals at different contents (0.01-2 wt%), and the differences in carbon dioxide capture and photoconversion performance were confirmed.

[0071] By supporting the metal, the carbon dioxide capture capacity was increased by approximately 30-50 ppmv compared to the existing Pure BiOCl and Ov BiOCl, and the photoconversion performance was improved by approximately 4 times compared to Pure BiOCl. The carbon dioxide capture and conversion performance was optimized at the content of 0.05 wt% Cu, 1 wt% Fe, and 0.3 wt% Co.

[0072] Comparison of atmospheric carbon dioxide capture and conversion by M1M2 / Ov BiOCl

[0073] Figure 11(a) shows the results of comparing the carbon dioxide capture and conversion performance of bimetallic photocatalysts, M1M2 / Ov BiOCl (M1M2=CuCo, CuNi, CuFe). As a result, the CuFe-supported photocatalyst showed the best carbon dioxide capture and photoconversion performance. Compared to pure BiOCl and Ov BiOCl, the capture performance was captured by approximately 160 ppmv and 100 ppmv more, and the photoconversion performance was improved by approximately 5 times and 2.5 times or more, respectively. In this way, it was confirmed that the performance was increased compared to the existing catalyst when Cu+Co, Cu+Ni, or Cu+Fe were supported together.

[0074] Figure 11(b) shows the results of evaluating carbon dioxide capture and conversion performance by fixing 0.05 wt% Cu, which had the best performance, and adding Fe according to the content in order to optimize the content of Cu and Fe that were finally selected. The performance was the best when the content was 0.05 wt% Cu and 0.3 wt% Fe.

[0075] Atmospheric carbon dioxide capture and conversion performance of optimized catalysts

[0076] Figure 12 shows the carbon dioxide capture and conversion performance of optimized catalysts in the atmosphere. Referring to Figure 12, Fe / Ov BiOCl containing 1 wt% Fe showed the highest carbon dioxide capture performance, followed by CuFe / Ov BiOCl containing 0.05 wt% Cu and 0.3 wt% Fe, which showed high carbon dioxide capture performance.

[0077] Meanwhile, the photoconversion performance of the bimetallic catalyst (CuFe / Ov BiOCl) was significantly higher than that of Fe / Ov BiOCl and Cu / Ov BiOCl.

[0078] Comparison of atmospheric carbon dioxide capture and conversion by pure BiOX and Ov BiOX (X=Cl, Br, I)

[0079] Figure 13 shows the atmospheric carbon dioxide capture and conversion performance of catalysts with modified halogen elements. Referring to Figure 13, all catalysts containing Cl, Br, and I exhibited atmospheric carbon dioxide capture and conversion performance.

[0080] Although the present invention has been described above with reference to preferred embodiments thereof, it will be understood by those skilled in the art that various modifications and changes may be made to the present invention without departing from the spirit and scope of the present invention as set forth in the claims below.

Claims

1. Containing a bismuth oxyhalide having one or more metals supported and oxygen vacancies, Photocatalysts for carbon dioxide capture and conversion.

2. In paragraph 1, The above metal is selected from Cu, Fe, Co, Ni, Mn, Ru, Pt, Au and Ag. Photocatalysts for carbon dioxide capture and conversion.

3. In paragraph 1, The above metal is included in an amount of 0.01 to 2 wt% relative to the total weight of the catalyst. Photocatalysts for carbon dioxide capture and conversion.

4. In paragraph 1, The above metal contains Cu and Fe, Photocatalysts for carbon dioxide capture and conversion.

5. In paragraph 4, Compared to the total weight of the catalyst, Cu is included in an amount of 0.01 to 0.5 wt%, and Fe is included in an amount of 0.3 to 1 wt%. Photocatalysts for carbon dioxide capture and conversion.

6. In paragraph 1, The above photocatalyst is characterized by selectively capturing carbon dioxide of 1000 ppm or less in the atmosphere under dark conditions. Photocatalysts for carbon dioxide capture and conversion.

7. In paragraph 6, The above photocatalyst is characterized in that it converts captured carbon dioxide into CO or CH4 when irradiated with light. Photocatalysts for carbon dioxide capture and conversion.

8. A first step of selectively capturing carbon dioxide in the atmosphere using a photocatalyst according to any one of clauses 1 to 7; and A second step of irradiating light on a catalyst in which carbon dioxide is captured to reduce it into a photoconversion product; A method for capturing and converting carbon dioxide in the atmosphere.

9. In paragraph 8, The above first step is characterized in that it is performed under dark conditions. A method for capturing and converting carbon dioxide in the atmosphere.

10. In paragraph 8, The above photoconversion product comprises CO or CH4. A method for capturing and converting carbon dioxide in the atmosphere.

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