KR20230140290A - Carbon nitride-titanium oxide composite for reducing nitrogen oxides and a method for producing the same - Google Patents

Abstract

One embodiment of the present invention provides a carbon nitride-titanium oxide composite for reducing nitrogen oxides and a method for manufacturing the same. The carbon nitride-titanium oxide composite for reducing nitrogen oxides includes a graphite carbon nitride having an interlayer structure; and titanium oxide positioned to cover the surface of the carbon nitride, wherein the titanium oxide is a spherical particle and has a two-phase structure in which an anatase phase and a rutile phase exist simultaneously.

Description

Carbon nitride-titanium oxide composite for reducing nitrogen oxides and a method for producing the same {Carbon nitride-titanium oxide composite for reducing nitrogen oxides and a method for producing the same}

The present invention relates to a carbon nitride-titanium oxide composite for reducing nitrogen oxides and a method for manufacturing the same. More specifically, the present invention relates to a carbon nitride-titanium oxide composite having a high visible light absorption rate and a high nitrogen oxide removal rate only by physically mixing carbon nitride and titanium oxide. A titanium oxide complex is provided.

Currently, humanity's means of generating energy is thermal power generation, which is mainly based on fossil fuels such as oil and coal. In general, when carbon-based fuel is burned in thermal power plants and internal combustion engine vehicles, exhaust gas reacts with nitrogen in the air at high temperature to generate gaseous nitrogen oxides. These gaseous nitrogen oxides react with moisture and other volatile organic compounds due to ultraviolet rays, producing acid rain and photochemical smog, and have fatal effects on the environment and human body. Recognizing this seriousness, regulations on air pollutant emissions are gradually being strengthened. Therefore, a solution to reduce nitrogen oxides in the atmosphere is needed.

Recently, as air pollution has worsened, technology to remove nitrogen oxides has been receiving more attention, and various technologies are being developed for this purpose. To date, there are two methods: (i) removal method by adsorption or absorption and (ii) removal method by destruction. Removal methods through adsorption or absorption require post-treatment of the adsorbed or absorbed material and generate secondary pollutants. Removal methods by destruction include various methods such as direct decomposition, selective catalytic/non-catalytic reduction, and plasma-assisted catalytic reduction. However, it is mostly effective in removing nitrogen oxides at low concentrations, and requires additional complicated processes or a lot of energy.

Accordingly, the recent nitrogen oxide reduction technology using photocatalysts that can use solar energy reduces nitrogen oxides in the air by oxidizing gaseous nitrogen oxides to nitrate through a reaction with electrons and holes generated through solar energy.

The nitrogen oxide reduction method has a simple process structure, is easy to use, does not require a lot of energy because nitrogen oxides are removed through solar energy, and the process cost is very low, so it is considered a promising nitrogen oxide removal method. . Among them, titanium dioxide is widely used as a photocatalytic oxidation active material for nitrogen oxide removal. However, titanium dioxide has the disadvantage of being unable to absorb visible light due to its wide bandgap (3.20 eV), which limits its nitrogen oxide removal performance under actual sunlight.

Therefore, many challenges still remain for the development of processes and materials for reducing nitrogen oxides.

Republic of Korea Patent No. 10-1348547

The technical problem to be achieved by the present invention is to provide a carbon nitride-titanium oxide composite for reducing nitrogen oxides and a method for manufacturing the same.

The carbon nitride-titanium oxide complex for reducing nitrogen oxides can be manufactured in a simple process by physical mixing, has a higher visible light absorption rate than existing photocatalysts, and provides a photocatalyst capable of efficient separation of photogenerated electrons and holes. The purpose is to

Using this, the purpose is to provide a carbon nitride-titanium oxide complex that can remove a large amount of nitrogen oxides compared to existing photocatalysts.

The technical problem to be achieved by the present invention is not limited to the technical problem mentioned above, and other technical problems not mentioned can be clearly understood by those skilled in the art from the description below. There will be.

In order to achieve the above technical problem, an embodiment of the present invention provides a carbon nitride-titanium oxide composite for reducing nitrogen oxides.

The carbon nitride-titanium oxide composite for reducing nitrogen oxides according to an embodiment of the present invention includes graphite carbon nitride having an interlayer structure; and titanium oxide positioned to cover the surface of the carbon nitride, wherein the titanium oxide is a spherical particle and may have a two-phase structure in which an anatase phase and a rutile phase exist simultaneously.

Additionally, according to one embodiment of the present invention, the weight ratio of titanium oxide and carbon nitride may be 9:1 to 1:9.

Additionally, according to an embodiment of the present invention, the carbon nitride may be a graphite two-dimensional layered structure compound containing an aromatic triazine ring.

Additionally, according to an embodiment of the present invention, the interlayer distance of the carbon nitride may be 0.3 nm to 0.35 nm.

Additionally, according to one embodiment of the present invention, the titanium oxide may be spherical particles with a diameter of 20 nm to 30 nm.

Additionally, according to one embodiment of the present invention, the carbon nitride-titanium oxide composite for reducing nitrogen oxides can absorb light with a wavelength of 200 nm to 500 nm.

In order to achieve the above technical problem, another embodiment of the present invention provides a method for manufacturing a carbon nitride-titanium oxide composite for reducing nitrogen oxides.

The method for producing the carbon nitride-titanium oxide composite for reducing nitrogen oxides according to an embodiment of the present invention includes preparing graphite carbon nitride and spherical particle titanium oxide having an interlayer structure; and the carbon nitride and titanium oxide It may include physically mixing to form a carbon nitride-titanium oxide complex.

Additionally, according to one embodiment of the present invention, the weight ratio of the carbon nitride and titanium oxide may be 9:1 to 1:9.

In addition, according to one embodiment of the present invention, in the step of forming the carbon nitride-titanium oxide complex, the carbon nitride-titanium oxide complex is prepared by performing a powder mixing process or a solution mixing process of the carbon nitride and the titanium oxide. It can be manufactured.

The carbon nitride-titanium oxide composite for reducing nitrogen oxides according to an embodiment of the present invention exhibits high light efficiency in the visible light region and can increase the separation efficiency of photoexcited electron-hole pairs, thereby improving nitrogen oxide reduction performance. There is a possible effect.

In addition, the carbon nitride-titanium oxide composite for reducing nitrogen oxides according to an embodiment of the present invention has the effect of being simply manufactured by physically mixing particles.

The effects of the present invention are not limited to the effects described above, and should be understood to include all effects that can be inferred from the configuration of the invention described in the detailed description or claims of the present invention.

Figure 1 is a scanning electron microscope image of a carbon nitride-titanium oxide composite according to an embodiment of the present invention.
Figure 2 shows ( _a ) ) Fourier transform infrared spectroscopic analysis spectrum.
Figure 3 is a DRS-UV/Vis spectra graph of carbon nitride-titanium oxide complex (CN10, CN20, CN30), titanium dioxide (TiO ₂ ), and carbon nitride (CN) according to an embodiment of the present invention.
Figure 4 is a graph showing the nitrogen oxide removal performance of the carbon nitride-titanium oxide composite under fluorescent light irradiation according to an embodiment of the present invention.
Figure 5 is a graph confirming the nitrogen oxide removal performance of the carbon nitride-titanium oxide composite under ultraviolet irradiation according to an embodiment of the present invention.
Figure 6 is a schematic diagram showing the band gap and mechanism of nitrogen oxide removal reaction of a carbon nitride-titanium oxide composite under fluorescent light or ultraviolet ray irradiation according to an embodiment of the present invention.
Figure 7 is an emission spectrum graph showing the wavelength of the light source used in the experiment ((a) ultraviolet rays, (b) fluorescent lamps).
Figure 8 is a graph showing the nitrogen oxide removal performance of the carbon nitride-titanium oxide composite according to the input material under fluorescent lamp irradiation according to an embodiment of the present invention.
Figure 9 is a graph showing the nitrogen oxide removal performance of the carbon nitride-titanium oxide composite according to the difference in titanium dioxide under fluorescent lamp irradiation according to an embodiment of the present invention.
Figure 10 is a graph showing the nitrogen oxide removal performance of the carbon nitride-titanium oxide composite according to the manufacturing method under fluorescent lamp irradiation according to an embodiment of the present invention.
Figure 11 is a DRS-UV-vis spectrum of CN20 and CN20-350 according to an embodiment of the present invention.
Figure 12 is a schematic diagram showing the nitrogen oxide removal mechanism of the carbon nitride-titanium oxide composite under fluorescent lamp or ultraviolet ray irradiation according to an embodiment of the present invention.
Figure 13 is a flowchart showing a method of manufacturing a carbon nitride-titanium oxide composite according to an embodiment of the present invention.

Hereinafter, the present invention will be described with reference to the attached drawings. However, the present invention may be implemented in various different forms and, therefore, is not limited to the embodiments described herein. In order to clearly explain the present invention in the drawings, parts that are not related to the description are omitted, and similar parts are given similar reference numerals throughout the specification.

Throughout the specification, when a part is said to be "connected (connected, contacted, combined)" with another part, this means not only "directly connected" but also "indirectly connected" with another member in between. "Includes cases where it is. In addition, when a part is said to “include” a certain component, this does not mean that other components are excluded, but that other components can be added, unless specifically stated to the contrary.

The terms used herein are only used to describe specific embodiments and are not intended to limit the invention. Singular expressions include plural expressions unless the context clearly dictates otherwise. In this specification, terms such as “comprise” or “have” are intended to indicate the presence of features, numbers, steps, operations, components, parts, or combinations thereof described in the specification, but are not intended to indicate the presence of one or more other features. It should be understood that this does not exclude in advance the possibility of the existence or addition of elements, numbers, steps, operations, components, parts, or combinations thereof.

Hereinafter, embodiments of the present invention will be described in detail with reference to the attached drawings.

A carbon nitride-titanium oxide composite for reducing nitrogen oxides according to an embodiment of the present invention will be described.

The carbon nitride-titanium oxide composite for reducing nitrogen oxides according to an embodiment of the present invention includes graphite carbon nitride having an interlayer structure; and titanium oxide positioned to cover the surface of the carbon nitride, wherein the titanium oxide is a spherical particle and has a two-phase structure in which an anatase phase and a rutile phase exist simultaneously.

Generally, commercially available titanium dioxide has a wide bandgap, so it can only be used in the ultraviolet region, and has a high degree of charge recombination, showing limited nitrogen oxide removal performance.

On the other hand, the carbon nitride-titanium oxide composite for reducing nitrogen oxides according to an embodiment of the present invention is a combination of titanium oxide and carbon nitride, and can exhibit superior light absorption and nitrogen oxide removal performance compared to existing titanium dioxide. .

At this time, the weight ratio of titanium oxide and carbon nitride according to an embodiment of the present invention may be 9:1 to 1:9.

At this time, the weight ratio of titanium oxide and carbon nitride according to an embodiment of the present invention may preferably be 9:1 to 5:5.

The reason why the weight ratio of titanium oxide and carbon nitride is 9:1 to 5:5 is that when the content of carbon nitride (CN) is 10 wt% or less, there may be a problem of lowering the nitrate ion selectivity, and the carbon nitride ( This is because if the content of CN) is more than 50wt%, there may be a problem of reduced nitrogen monoxide removal efficiency.

The nitrogen oxide removal performance according to the titanium oxide and carbon nitride content will be described in detail later in the experimental examples below.

At this time, the carbon nitride may be a graphite two-dimensional layered polymer containing an aromatic triazine ring.

For example, the carbon nitride may be melon, poly(triazine imide), or poly(heptazine imide).

The aromatic triazine ring of the carbon nitride is an unsaturated 6-membered heterocyclic compound with three nitrogen atoms in the ring and has semiconductor properties. It has a band gap of 2.73 eV and a maximum response wavelength of 450 nm.

In this specification, graphitic carbon nitride may mean carbon nitride having a two-dimensional layered structure including an aromatic triazine ring.

At this time, the interlayer distance of the carbon nitride may be 0.3 nm to 0.35 nm.

At this time, when carbon nitride with a two-dimensional layered structure is used as a constituent material of the photocatalyst, it may have the effect of increasing nitrate selectivity.

Therefore, when the carbon nitride and titanium oxide are hybridized, the characteristics of each material are expressed without changing the band gap of the carbon nitride-titanium oxide complex, thereby creating a synergistic effect and increasing the light absorption rate in the visible light region, and the nitrogen oxide Removal efficiency can be increased.

The detailed nitrogen oxide removal mechanism of the carbon nitride-titanium oxide composite is described later in the experimental examples below.

Additionally, in the present invention, the titanium oxide may include one or more types selected from titanium dioxide (TiO ₂ ).

The titanium oxide described above may be a material with a high carbon monoxide removal rate.

At this time, the titanium oxide may have a two-phase structure in which an anatase phase and a rutile phase exist simultaneously, and the two-phase structure in which an anatase phase and a rutile phase exist simultaneously is It has the characteristic of having higher activity compared to single-phase structures, and the rutile phase has high activity in visible light, which can result in high nitrogen oxide removal efficiency.

Additionally, the titanium oxide may be spherical particles with a size of 20 nm to 30 nm.

The reason why the size of the titanium oxide particles is 20 nm to 30 nm is that if the size of the titanium oxide particles is 20 nm or less, there may be problems that are difficult to handle in the process, and if the size of the titanium oxide particles is 30 nm or more, compared to nanoparticles. There may be a problem that the synergistic effect due to carbon nitride is lowered as the contact interface is reduced.

In addition, the carbon nitride-titanium oxide composite for reducing nitrogen oxides can absorb light with a wavelength of 200 nm to 500 nm.

By absorbing light with a wavelength of 200 nm to 500 nm, not only ultraviolet rays of light but also visible light wavelengths can be absorbed, and thus the light absorption rate can be increased, and thus the removal efficiency of nitrogen oxides can be increased.

In addition, during the nitrogen oxide removal process of the carbon nitride-titanium oxide complex, intermediate products generated from titanium oxide react with carbon nitride, thereby increasing nitrogen oxide removal efficiency.

A method for manufacturing a carbon nitride-titanium oxide composite for reducing nitrogen oxides according to another embodiment of the present invention will be described.

The method of manufacturing the carbon nitride-titanium oxide composite for reducing nitrogen oxides includes preparing graphite carbon nitride having an interlayer structure and titanium oxide having spherical particles; and physically mixing the carbon nitride and titanium oxide to form carbon nitride-titanium. It may include forming an oxide complex.

In the first step, it may include preparing graphite carbon nitride and spherical particle titanium oxide having an interlayer structure. (S100)

The graphitic carbon nitride having the interlayer structure is a graphitic two-dimensional layered structure compound containing an aromatic triazine ring.

In the present invention, the graphitic carbon nitride having an interlayer structure, for example, a method of producing the graphitic carbon nitride having an interlayer structure includes the steps of dissolving trithiosynuric acid in dimethyl sulfoxide by performing ultrasonic treatment; mixing the solution with water; Graphite carbon nitride (tri-s-triazine) can be produced by performing the steps of filtering, washing, and drying; and calcining the dried powder.

Additionally, the titanium oxide of the spherical particles may be titanium dioxide (TiO ₂ ).

In the second step, it may include physically mixing the carbon nitride and titanium oxide to form a carbon nitride-titanium oxide complex. (S200)

The weight ratio of the carbon nitride and titanium oxide may be 1:9 to 9:1, and preferably the weight ratio of the carbon nitride and titanium oxide may be 1:9 to 5:5.

Additionally, the carbon nitride-titanium oxide complex can be manufactured by performing a process of mixing the carbon nitride and the titanium oxide in a mortar or a process of mixing them in a solution.

The mixing process in a mortar or a mixing process in a solution is a physical mixing process that allows carbon nitride and titanium oxide to come into contact to form a composite.

At this time, the mixing process in the solution does not cause any reaction in the solvent, and the hybrid can be produced by physical mixing by dispersing and stirring carbon nitride (CN) and titanium oxide (TiO ₂ ).

Therefore, the manufacturing method of the carbon nitride-titanium oxide composite according to an embodiment of the present invention can be simply manufactured by physical mixing, and is manufactured at a specific ratio, so that the nitrogen oxide reduction performance of the carbon nitride-titanium oxide composite is increased. there is.

Manufacturing example

First, to prepare titanium oxide and carbon nitride,

As the titanium oxide, P25 from Degussa, a commercially available titanium dioxide (TiO ₂ ), was used.

In addition, the method for producing graphite carbon nitride (CN) as carbon nitride is as follows.

Preparing a solution by dissolving tri-thiocyanuric acid (Sigma-Aldrich, USA; 95.0%) in 10 mL of dimethyl sulfoxide (Daejung, Korea, 99.5%) through sonication. ; Mixing the solution with 20 ml of water (H ₂ O); Filtering the solution mixed with water (H ₂ O) after 1 hour, washing with water, and drying at 80°C; And the dried powder was heated to 550°C for 4 hours in a nitrogen atmosphere at a temperature increase rate of 2.3°C per minute. It includes the step of producing graphitic carbon nitride (CN) by firing in a pipe at °C.

Next, 80 mg (80 wt%) titanium dioxide (TiO ₂ ) and 20 mg (20 wt%) graphite carbon nitride (CN) were added to a mortar and mixed to form a graphite carbon nitride-titanium dioxide complex. .

Example

In this specification, each carbon nitride-titanium oxide composite is referred to as CN30 when the amount of CN compared to TiO ₂ is 30 wt%, CN20 when the amount of CN compared to TiO ₂ is 20 wt%, and CN10 when the amount of CN compared to TiO ₂ is 10 wt%. CN represents pure graphitic carbon nitride, and TiO ₂ represents pure titanium dioxide.

Structural characteristics of the carbon nitride-titanium oxide composite will be described with reference to FIGS. 1 and 2.

Figure 1 is a scanning electron microscope image of a carbon nitride-titanium oxide composite according to an embodiment of the present invention.

Referring to FIG. 1, it can be seen from the scanning electron microscope image that titanium dioxide (TiO ₂ ) is a very small spherical particle with a size of about 30 nm.

In addition, referring to Figure 1 (c to d), in the case of the graphite carbon nitride-titanium dioxide composite (CN/TiO ₂ ) of the above production example, it can be seen that TiO ₂ covers the relatively large surface of CN. there is.

Additionally, referring to Figure 1 (e), it can be seen that as the ratio of carbon nitride (CN) increases, more carbon nitride (CN) appears on the surface.

Figure 2 shows ( _a ) ) Fourier transform infrared spectroscopic analysis spectrum.

Referring to FIG. 2(a), in X-ray diffraction analysis, TiO ₂ has a two-phase structure having both an anatase phase and a rutile phase, and compared It can be confirmed that the carbon nitride (CN) prepared as a group is a graphitic carbon nitride with an interlayer distance of 0.33 nm (27.4°).

In addition, in the case of the carbon nitride-titanium oxide complex peak, it shows a similar pattern to the titanium dioxide TiO ₂ peak, and the characteristic pattern of carbon nitride is not clearly visible. This is because the peak intensity of amorphous carbon is higher than the peak intensity of TiO ₂ , which has high crystallinity. This is because the nitride (CN) peak intensity is low, making observation difficult.

Referring to Figure 2(b), in Fourier-Transform Infrared spectroscopy, in the case of TiO ₂ and carbon nitride-titanium oxide complexes (CN10, CN20, CN30), in the range of 650-800 cm ^-1 The observed peaks represent absorption peaks for Ti-O and O-Ti-O bonds.

In addition, in the case of carbon nitride (CN) and carbon nitride-titanium oxide complexes (CN10, CN20, CN30), all peaks visible in the range of 1200-1600 cm ^-1 are aromatic triazine rings composed of carbon and nitrogen of carbon nitride (CN). It is a characteristic caused by stretching vibration.

Additionally, the peak visible in the range of 3000-3600 cm ^-1 represents the stretching vibration of the unpolymerized NH bond remaining in the carbon nitride or the OH bond of the water molecule adsorbed into the pore structure.

Referring to FIG. 3, the optical properties of the carbon nitride-titanium oxide composite according to an embodiment of the present invention will be described.

Figure 3 is a DRS-UV/Vis spectra graph of carbon nitride-titanium oxide complex (CN10, CN20, CN30), titanium dioxide (TiO ₂ ), and carbon nitride (CN) according to an embodiment of the present invention.

Referring to the top of FIG. 3, titanium dioxide (TiO ₂ ) is a white particle, but forms a hybrid with dark yellow carbon nitride (CN), so as the carbon nitride (CN) content increases, the color gradually becomes darker yellow. You can see that it changes to .

In addition, in the ultraviolet-visible diffuse reflectance spectroscopy (Ultraviolet/Visible) of FIG. 3, the carbon nitride (CN) content of the carbon nitride-titanium oxide composite compared to TiO ₂ , which has limited absorbance to light above 400 nm. It can be seen that as this increases, the absorbance in the visible light region (380 nm to 780 nm) increases.

Through this, it can be confirmed that hybridization of carbon nitride (CN) and titanium dioxide (TiO ₂ ) can improve the absorption rate of visible light.

Referring to FIG. 4, the nitrogen oxide removal performance of the carbon nitride-titanium oxide composite according to an embodiment of the present invention will be described.

Figure 4 is a graph showing the nitrogen oxide removal performance of the carbon nitride-titanium oxide composite under fluorescent light irradiation according to an embodiment of the present invention.

Table 1 below shows titanium dioxide (TiO ₂ ), carbon nitride (CN), and the carbon nitride-titanium oxide complex according to an embodiment of the present invention under light irradiation in the fluorescent lamp wavelength range (365-700 nm, 6000 ± 300 lux). (CN10, CN20, CN30) showed nitrogen monoxide (NO) removal efficiency, nitrogen dioxide (NO ₂ ) generation efficiency, nitrogen oxide (NOx) removal efficiency, and nitrate ion (NO ₃ ^- ) selectivity.

Sample NO removal
(%) NO ₂ generation
(%) No _x removal
(%) NO ₃ ^- selectivity
(%) TiO ₂ 32.79 15.98 16.81 51.27 CN10 43.72 24.38 19.34 44.24 CN20 50.44 26.18 24.27 48.12 CN30 29.04 15.75 13.30 45.80 CN 12.19 3.19 9.0 73.83 Bulk g-CN 4.98 3.14 1.83 36.75

Referring to Figure 4 and Table 1, in the case of titanium dioxide (TiO ₂ ), it shows a NO removal efficiency of 32.79% and a NOx removal efficiency of 16.81%, and in the case of carbon nitride (CN), it shows a NO removal efficiency of 12.19% and a NOx removal efficiency of 9.0%. It can be confirmed that the NOx removal efficiency is %. In the case of carbon nitride-titanium oxide complexes (CN10, CN20, CN30), depending on the ratio, an increase effect exceeds the arithmetic average removal efficiency, and specific values will be described later.

For example, in the case of carbon nitride-titanium oxide composite (CN10), considering that the ratio of titanium dioxide and carbon nitride (CN) is 9:1, it is expected to show a NOx removal efficiency of 30.73% and a NOx removal efficiency of 16.03%. As expected, the experimental results show that the carbon nitride-titanium oxide composite (CN10) sample shows a NO removal efficiency of 43.72% and a NOx removal efficiency of 19.34%.

In other words, it can be seen that the nitrogen oxide removal effect increases when a composite is composed of titanium dioxide (TiO ₂ ) and carbon nitride (CN).

In addition, it can be confirmed that when titanium dioxide (TiO ₂ ) and carbon nitride (CN) form a composite at a ratio of 8:2, the NO removal efficiency is 50.44% and the NOx removal efficiency is 24.27%.

Through this, a hybrid product made of titanium dioxide (TiO ₂ ) and carbon nitride (CN) at a ratio of 8:2 shows a very large synergistic effect and can exhibit the best nitrogen oxide removal performance.

At this time, Bulk g-CN, which is made by calcining DCDA (Dicyandiamide) at 550°C, shows lower NO removal efficiency and higher NO ₂ generation efficiency compared to carbon nitride (CN). Therefore, carbon nitride (CN) rather than bulk g-CN was used to prepare the hybrid.

Referring to FIG. 5, the nitrogen oxide removal performance of the carbon nitride-titanium oxide composite under ultraviolet ray irradiation according to an embodiment of the present invention will be described.

Figure 5 is a graph confirming the nitrogen oxide removal performance of the carbon nitride-titanium oxide composite under ultraviolet irradiation according to an embodiment of the present invention.

Table 2 shows the nitrogen monoxide (NO) removal efficiency of the comparative titanium dioxide (TiO ₂ ), carbon nitride (CN), and carbon nitride-titanium oxide composite under light irradiation in the ultraviolet region (300-400 nm, 6000±300 lux), It showed nitrogen dioxide (NO ₂ ) production efficiency, nitrogen oxide (NOx) removal efficiency, and nitrate ion (NO ₃ ^- ) selectivity.

Sample NO removal
(%) NO ₂ generation
(%) No _x removal
(%) NO ₃ ^- selectivity
(%) TiO ₂ 58.88 29.48 29.4 49.93 CN10 62.65 22.01 40.34 64.39 CN20 68.01 17.29 50.72 74.58 CN30 62.78 33.95 28.83 45.92 CN 24.3 9.96 14.34 59.01

Referring to FIG. 5 and Table 2, not only titanium dioxide (TiO ₂ ) but also carbon nitride-titanium oxide complexes (CN10, CN20, CN30) can show high NO removal efficiency. At this time, it can be confirmed that the carbon nitride-titanium oxide composite (CN20) exhibits the highest NOx removal efficiency.

_The carbon nitride-titanium oxide composite (CN20) can exhibit the highest _NO

With reference to FIGS. 6 and 7, the nitrogen removal reaction mechanism of the carbon nitride-titanium oxide composite according to light according to an embodiment of the present invention will be described.

Figure 6 is a schematic diagram showing the band gap and mechanism of nitrogen oxide removal reaction of a carbon nitride-titanium oxide composite under fluorescent light or ultraviolet ray irradiation according to an embodiment of the present invention.

Figure 7 is an emission spectrum graph showing the wavelength of the light source used in the experiment ((a) ultraviolet rays, (b) fluorescent lamps).

First, referring to Figure 7(a) (ultraviolet light), it can be seen that the peak is detected at a wavelength between 300nm and 400nm, and referring to Figure 7(b) (fluorescent light), a wide wavelength range of 365nm to 700nm is observed. It can be seen that the peak appears in .

Referring to FIG. 6, under ultraviolet rays or fluorescent light irradiation, electrons (e-) are excited from the valence band (VB) to the conduction band (CB) in both carbon nitride (CN) and titanium dioxide (TiO ₂ ), and the valence band (VB) is excited. It can be confirmed that holes (h+) are formed in .

Additionally, in titanium dioxide (TiO ₂ ), electrons in the conduction band (CB) form O ₂ radicals, and the O ₂ radicals meet NO to form NO ₃ ^- (①). And the hole created in the valence band (VB) of titanium dioxide (TiO ₂ ) forms an OH radical that meets NO to form HNO ₂ (②).

At this time, NO ₃ ^- generated from titanium dioxide (TiO ₂ ) is adsorbed on Ti on the surface of titanium dioxide (TiO ₂ ), and when the adsorption reaches saturation, the electrons formed in the conduction band (CB) of TiO ₂ are converted to NO ₃ ^- It cannot be produced, so instead a reaction is performed to change the OH radical formed during the NO ₂ production reaction into an OH anion (③).

For this reason, when titanium dioxide (TiO ₂ ) is present alone, the amount of NO ₂ produced is large and the selectivity of NO ₃ ^- is about 50%, whereas the surface of carbon nitride (CN) presented in the present invention has a high electronegativity of nitrogen. Because the surface has a partial negative charge and does not adsorb NO ₃ ^- well, the selectivity of the reaction to produce NO ₃ ^- is high. (About 60% of ultraviolet rays, over 70% of fluorescent lights)

At this time, the effect of increasing the selectivity of the reaction for producing NO ₃ ^- is that electrons that can be generated through the reaction mechanism shown below in FIG. 6 in the valence band (VB) of titanium dioxide (TiO ₂ ). By removing holes in the valence band (VB) of carbon nitride (CN), holes in carbon nitride (CN) that are relatively less consumed are effectively removed, thereby promoting NO and NOx removal reactions through photocatalytic reduction reactions. You can.(④)

Therefore, in the case of the titanium dioxide (TiO ₂ )-carbon nitride (CN) composite manufactured by physically mixing the two materials of titanium dioxide (TiO ₂ ) and carbon nitride (CN), it shows a synergistic effect that exceeds the performance of the individual materials. You can.

With reference to FIGS. 8 and 9, the nitrogen oxide removal performance of the carbon nitride-titanium oxide composite according to an embodiment of the present invention will be described.

Figure 8 is a graph showing the nitrogen oxide removal performance of the carbon nitride-titanium oxide composite according to the input material under fluorescent lamp irradiation according to an embodiment of the present invention.

Table ₃ below shows _the nitrogen monoxide (NO) removal efficiency, nitrogen dioxide (NO ₂ ) generation efficiency, nitrogen oxide (NOx) removal efficiency, and nitrate ion (NO ₃ ^- ) This is a table showing selectivity.

Sample NO removal
(%) NO ₂ generation
(%) No _x removal
(%) NO ₃ ^- selectivity
(%) TiO ₂ 32.79 15.98 16.81 51.27 TCA/TiO ₂ -20 38.48 20.26 18.22 47.35 TCA-550 10.66 4.94 5.72 53.66

Referring to Figures 8 to Table 3, TCA-550 is a control prepared by directly calcining the precursor TCA in powder form without a solution process. The TCA-550 has a NO removal efficiency of 10.66% and NO ₂ of 4.94%. Generation efficiency and NOx removal efficiency of 5.72% can be shown.

In particular, TCA-550 shows lower NO ₃ ^- selectivity compared to carbon nitride (CN). When a composite of TCA-550 and TiO ₂ was prepared (TCA/TiO ₂ -20 experimental group, in this case, the proportion of TCA-550 in the hybrid was 20%), NO removal efficiency of 38.48%, NO ₂ production efficiency of 20.26%, With a NOx removal efficiency of 18.22%, it shows an overall lower photocatalytic efficiency compared to carbon nitride-titanium oxide composite (CN20).

Through this, it can be confirmed that the role of carbon nitride (CN) is important to obtain the best performance.

Figure 9 is a graph showing the nitrogen oxide removal performance of the carbon nitride-titanium oxide composite according to the difference in titanium dioxide under fluorescent lamp irradiation according to an embodiment of the present invention.

Table 4 below shows titanium dioxide (TiO ₂ ) commercially available as NP400, a hybrid using NP400 and carbon nitride (CN) as a carbon nitride-titanium oxide complex as CN/NP20, and nitrogen monoxide (CN) of carbon nitride (CN) under fluorescent lamp irradiation. This table shows the NO) removal efficiency, nitrogen dioxide (NO ₂ ) generation efficiency, nitrogen oxide (NOx) removal efficiency, and nitrate ion (NO ₃ ^- ) selectivity.

Sample NO removal
(%) NO ₂ generation
(%) No _x removal
(%) NO ₃ ^- selectivity
(%) NP400 8.77 5.65 3.12 35.6 CN/NP20 14.58 6.68 7.9 54.18 CN 12.19 3.19 9.0 73.83

Referring to Figures 9 to Table 4, NP400 is a commercially available titanium dioxide (TiO ₂ ) product and is a control group having a single-phase structure of anatase, which is known to have low activity in visible light. The NP400 contains 8.77% NO. It shows removal efficiency, NO ₂ generation efficiency of 5.65%, and NOx removal efficiency of 3.12%.

When the carbon nitride-titanium oxide composite according to an embodiment of the present invention is composed of a hybrid using NP400 and carbon nitride (CN), it shows a NO removal efficiency of 14.58%, a NO ₂ production efficiency of 6.68%, and a NO 2 production efficiency of 7.9%. You can check the NOx removal efficiency.

Referring to FIGS. 10 to 12, nitrogen oxide removal performance according to the carbon nitride-titanium oxide composite manufacturing method will be described.

Figure 10 is a graph showing the nitrogen oxide removal performance of the carbon nitride-titanium oxide composite according to the manufacturing method under fluorescent lamp irradiation according to an embodiment of the present invention.

Figure 11 is a DRS-UV-vis spectrum of CN20 and CN20-350 according to an embodiment of the present invention.

Figure 12 is a schematic diagram showing the nitrogen oxide removal mechanism of the carbon nitride-titanium oxide composite under fluorescent lamp or ultraviolet ray irradiation according to an embodiment of the present invention.

In order to manufacture a carbon nitride-titanium oxide composite with a more uniform and reliable heterojunction structure, the prepared carbon nitride-titanium oxide composite (CN20) was fired at 350°C in a nitrogen atmosphere.

This is named the calcination hybrid (CN20-350).

Referring to Figure 10, it can be seen that the calcinated hybrid material (CN20-350) exhibits lower NO removal efficiency and NOx removal efficiency than before calcination (CN20).

Referring to Figure 11, it can be seen through DRS-UV-vis spectra that the absorption ability of CN20-350 for light above 450 nm is greatly reduced.

In addition, when the fired hybrid material (CN20-350) has a heterojunction structure, the charge of the conduction band (CB) from carbon nitride (CN) moves to the conduction band (CB) of TiO ₂ , which has a lower potential, As the holes in the valence band (VB) of TiO ₂ also move to the holes of carbon nitride (CN), which has a lower potential, O ₂ radicals generated in the conduction band (CB) of carbon nitride (CN) and the valence band of TiO ₂ As the OH radicals generated from (VB) are reduced, NO removal performance may be reduced.

Therefore, it can be confirmed that the carbon nitride-titanium oxide composite of the present invention can increase the NOx removal efficiency of the unfired material.

The description of the present invention described above is for illustrative purposes, and those skilled in the art will understand that the present invention can be easily modified into other specific forms without changing the technical idea or essential features of the present invention. will be. Therefore, the embodiments described above should be understood in all respects as illustrative and not restrictive. For example, each component described as single may be implemented in a distributed manner, and similarly, components described as distributed may also be implemented in a combined form.

The scope of the present invention is indicated by the patent claims described below, and all changes or modified forms derived from the meaning and scope of the claims and their equivalent concepts should be construed as being included in the scope of the present invention.

Claims (9)

Graphite carbon nitride with an interlayer structure; and
Includes titanium oxide positioned to cover the surface of the carbon nitride,
The titanium oxide is a spherical particle and has a two-phase structure in which an anatase phase and a rutile phase exist simultaneously. A carbon nitride-titanium oxide complex for reducing nitrogen oxides. According to paragraph 1,
A carbon nitride-titanium oxide composite for reducing nitrogen oxides, characterized in that the weight ratio of the titanium oxide and carbon nitride is 9:1 to 1:9. According to paragraph 1,
The carbon nitride is a carbon nitride-titanium oxide composite for reducing nitrogen oxides, characterized in that the carbon nitride is a graphite two-dimensional layered structure compound containing an aromatic triazine ring. According to paragraph 1,
A carbon nitride-titanium oxide composite for reducing nitrogen oxides, characterized in that the interlayer distance of the carbon nitride is 0.30 nm to 0.35 nm. According to paragraph 1,
A carbon nitride-titanium oxide composite for reducing nitrogen oxides, characterized in that the titanium oxide is a spherical particle with a diameter of 20 nm to 30 nm. According to paragraph 1,
The carbon nitride-titanium oxide complex for reducing nitrogen oxides is characterized in that it absorbs light with a wavelength of 200 nm to 500 nm. Preparing graphitic carbon nitride and spherical particle titanium oxide having an interlayer structure; And
A method for producing a carbon nitride-titanium oxide composite for reducing nitrogen oxides, comprising the step of physically mixing the carbon nitride and titanium oxide to form a carbon nitride-titanium oxide composite. In clause 7,
A method for producing a carbon nitride-titanium oxide composite for reducing nitrogen oxides, characterized in that the weight ratio of the carbon nitride and titanium oxide is 9:1 to 1:9. In clause 7,
In the step of forming the carbon nitride-titanium oxide complex,
The carbon nitride-titanium oxide composite is a method of producing a carbon nitride-titanium oxide composite for reducing nitrogen oxides, characterized in that the carbon nitride and the titanium oxide are manufactured by performing a powder mixing process or a solution mixing process.

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