KR20120134506A - Surface-modified photocatalyst and method of preparing same - Google Patents

Abstract

PURPOSE: A surface reformed photo catalyst and a manufacturing method of the same are provided to increase stability and efficiently decompose pollutants. CONSTITUTION: A surface reformed photo catalyst includes noble metal supported titanium dioxide, and phosphate group combined on the surface of the titanium dioxide. A manufacturing method of the photo catalyst includes the following steps: titanium dioxide liquid is mixed with a noble metal containing precursor; the mixture is reduced to manufacture the noble metal supported titanium dioxide; the noble metal supported titanium dioxide is added into a phosphoric acid solution; and the resultant product is thermally treated. The noble metal is Pt, Pd, Ru, Au, Ag, Ni, Cu, or the combination of the same. [Reference numerals] (AA) Comparative embodiment 1; (BB) Comparative embodiment 2; (CC) Comparative embodiment 3; (DD) Embodiment 1; (E1,E2,E3) UV irradiation time(min)

Description

SURFACE-MODIFIED PHOTOCATALYST AND METHOD OF PREPARING SAME

The present invention relates to surface modified photocatalysts and methods for their preparation.

When light with a predetermined energy or more is irradiated, a material that excites electrons to generate electrons and holes is called a semiconductor, and among these, a material that exhibits catalytic activity is called a photocatalyst.

These photocatalysts are used to generate energy or to clean contaminated water. In particular, such photocatalysts have been known to be able to decompose various biologically degradable substances that existing microorganisms cannot remove. In addition, the photocatalyst can be used semi-permanently and oxidizes most organic matters and decomposes them into carbon dioxide and water, so there is little secondary pollution and is effective for removing bleach and odor. Accordingly, various studies on environmentally friendly wastewater treatment methods using photocatalysts have been made.

In the wastewater treatment method using a photocatalyst, when light having energy above the band gap of the photocatalyst is irradiated, electrons and holes are generated on the surface of the photocatalyst. Energy energized electrons react with dissolved oxygen in water, and at the same time, holes on the surface of the photocatalyst oxidize water or OH ^- to form oxidizing OH radicals, and the resulting OH radicals decompose harmful organic substances. Will be.

The photocatalyst has been widely studied as a practical photocatalyst for the purification of contaminated water because titanium dioxide is very active, stable, non-toxic and inexpensive under ultraviolet irradiation.

Titanium dioxide produces electrons and holes excited under ultraviolet irradiation, and contaminants are decomposed by the holes thus produced, or by OH radicals produced by the reaction of holes with water (or OH ⁻ ).

Photocatalytic activity is affected by the properties of TiO ₂ such as specific surface area, surface charge, crystallinity, surface crystalline surface, particle size, surface functional group density and lattice defects. In particular, since most photocatalytic reactions occur at the surface, the surface properties of TiO ₂ are important factors in determining photocatalytic reaction kinetics, mechanisms and efficiencies.

In order to improve the properties of TiO ₂ , in particular to increase the photocatalytic efficiency (contaminant decomposition efficiency), TiO ₂ is used in various ways such as polymer coating, metal deposition, anion complexation, and silica and hydride. Research has been attempted to modify the surface of.

The present invention is to provide a surface-modified photocatalyst having excellent contaminant decomposition efficiency and excellent stability.

The present invention also provides a method for producing the photocatalyst.

One embodiment of the present invention is a titanium dioxide (TiO ₂ ) loaded with a precious metal; And it provides a surface-modified photocatalyst comprising a phosphate group (PO ₄ ^3- ) bonded to the titanium dioxide surface.

The photocatalyst may have a P 2p spectrum and a spectrum due to a noble metal at the time of XPS measurement.

In the photocatalyst, the P / Ti atomic ratio may be 0.01 to 0.5. Further, in the photocatalyst, the P / Ti atomic ratio may be 0.05 to 0.2.

The amount of the precious metal supported may be 0.1 to 10 parts by weight based on 100 parts by weight of titanium dioxide. The amount of the precious metal supported may be 0.5 to 1.5 parts by weight based on 100 parts by weight of titanium dioxide.

The precious metal may be Pt, Pd, Ru, Au, Ag, Ni, Cu or a combination thereof.

The photocatalyst may be used as a photocatalyst selected from the group consisting of a photocatalyst for wastewater treatment, a photocatalyst for an air purifier, a photocatalyst for purifying air, a photocatalyst for purifying water, a photocatalyst for removing odors, and a photocatalyst for antibacterial activity.

Another embodiment of the present invention is to mix the titanium dioxide liquid and the noble metal containing precursor; Reducing the mixture to prepare titanium dioxide carrying precious metals; Adding titanium dioxide carrying the noble metal to the phosphoric acid solution; It provides a method for producing a surface-modified photocatalyst comprising the step of heat-treating the obtained product.

The reduction can be carried out by a light supporting method.

The precious metal-containing precursor may be a compound containing a precious metal which is Pt, Pd, Ru, Au, Ag, Ni, Cu, or a combination thereof.

The heat treatment process may be carried out at 50 to 1000 ℃ for 1 minute to 10 hours.

Other specific details of embodiments of the present invention are included in the following detailed description.

The present invention provides a surface modified photocatalyst having high contaminant decomposition efficiency and stability.

1 is a view showing an example of a contaminant decomposition mechanism of the photocatalyst according to an embodiment of the present invention.
2 is a view showing an example of a contaminant decomposition mechanism of a conventional photocatalyst.
Figure 3 is a graph showing the measurement of the XPS (X-ray photoelectron spectroscopy) spectrum of the photocatalyst of Example 2 and Comparative Examples 1, 3, 5.
4 is an energy-filtration transmission electron microscope (EFTEM) and a high resolution transmission electron microscope (HRTEM) photograph of the photocatalyst of Example 1. FIG.
FIG. 5 is a graph showing surface charges of photocatalysts of Example 1 and Comparative Examples 1 to 3;
FIG. 6 is a graph showing the fluorescence emission intensity of 7-hydroxycumarin according to ultraviolet irradiation time of the photocatalysts of Example 1 and Comparative Examples 1 to 3. FIG.
Figure 7 is a graph showing the measurement of the photocurrent amount of the photocatalyst of Example 1 and Comparative Examples 1 to 3.
8 is a graph showing the decomposition rate of 2,4-dichlorophenoxy acetic acid according to the ultraviolet irradiation time of the photocatalysts of Example 1 and Comparative Examples 1 to 3 under various pH conditions.
Figure 9 is a graph showing the measurement of the production rate of 2,4-dichlorophenol according to the ultraviolet irradiation time of the photocatalyst of Example 1 and Comparative Examples 1 to 3 under various pH conditions.
10 is a graph showing the measurement of the chlorine production rate according to the ultraviolet irradiation time of the photocatalyst of Example 1 and Comparative Examples 1 to 3 under various pH conditions.
11 is a graph showing the pH stability of the photocatalysts of Example 1 and Comparative Example 4;
12 is a graph showing the resolution of 4-chlorophenol in the photocatalysts of Example 1 and Comparative Example 3;

Hereinafter, embodiments of the present invention will be described in detail. However, this is presented as an example, by which the present invention is not limited and the present invention is defined only by the scope of the claims to be described later.

The present invention relates to a photocatalyst whose surface is modified by combining two methods of phosphoric acid adsorption and other surface modification methods for supporting precious metals. Photocatalyst of the present invention is a titanium dioxide (TiO ₂ ) loaded with a precious metal; And a phosphoric acid group (PO ₄ ^3- ) bonded to the titanium dioxide surface.

The photocatalyst is one having a P 2p spectrum and a spectrum due to a noble metal in X-ray photoelectron spectroscopy (XPS) measurement. The spectra attributable to the precious metals are Pt 4f spectra for Pt, Au 4f spectra for Au, Ag 3d spectra for Ag, Pd 3d spectra for Pd, Ru 3d and Cu for Ru In the case of Cu 2p spectrum, Ni may be Ni 2p spectrum.

The phosphate group bound to the surface serves to generate a mobile OH radical having a greater oxidizing power than the OH radical adsorbed on the titanium dioxide surface.

In the photocatalyst of the present invention, the P / Ti atomic ratio may be 0.01 to 0.5, with 0.05 to 0.2 being preferred. When the P / Ti atomic ratio is included in the above range, it is possible to exhibit better light efficiency (photoactivity).

The amount of the precious metal supported may be 0.1 to 10 parts by weight, and 0.5 to 1.5 parts by weight based on 100 parts by weight of titanium dioxide. When the supported amount of the noble metal is included in the above range, it may exhibit more excellent light efficiency (photo activity).

As the titanium dioxide, commercially available titanium dioxide or a commercially available one such as Deggusa P-25 (manufactured by Degussa Corp.) or Hombikat UV 100 (Sachtleben Chemie GmbH) can be used.

Pt, Pd, Ru, Au, Ag, Ni, Cu or a combination thereof may be used as the noble metal.

Photocatalyst according to an embodiment of the present invention having the above configuration, it is possible to quickly transfer the electrons excited by the platinum supported on the surface to oxygen to suppress recombination with holes, and also by the phosphate group bonded to the surface Highly oxidizing, mobile OH radicals can be generated mainly, resulting in improved pollutant degradation efficiency. In addition, the adsorption of contaminants may be prevented by the phosphate group bound to the surface, thereby suppressing the generation of highly toxic decomposition by-products caused by reaction with holes. In addition, since the phosphate group is strongly bound to titanium dioxide, the photocatalyst may exhibit very high pH stability. If fluorine is bonded instead of the phosphate group, the binding force is weaker than that of the phosphate group, and there is a concern that the pH stability is slightly lowered.

Such a photocatalyst according to an embodiment of the present invention can be used as a wastewater treatment, air purifier, air purification, water purification, odor removal or antibacterial photocatalyst, in particular phenolic compounds known as environmental pollutants (phenolic It shows good decomposition efficiency when applied to wastewater treatment containing compounds.

A mechanism for decomposing contaminants by a photocatalyst according to an embodiment of the present invention is shown in FIG. 1 using 2,4-dichlorophenoxy acetic acid contaminants as an example. As shown in Fig. 1, the pollutant is limited to adsorption by the phosphate group of the photocatalyst, and when light is irradiated to the photocatalyst, the generated electrons are rapidly transferred to oxygen by platinum, and the hole and water react, The highly mobile OH radicals are formed, and these OH radicals can attack the benzene ring of 2,4-dichlorophenoxy acetic acid, thereby suppressing the generation of 2,4-dichlorophenol, which is a by-product of high toxicity.

On the contrary, the contaminant decomposition mechanism of the photocatalyst with Pt and without phosphate bond is 2,4-dichlorophenoxy acetic acid directly bonds with Ti of the photocatalyst, as shown in FIG. By this oxidation, highly toxic 2,4-dichlorophenol is formed.

Another embodiment of the present invention is to provide a method for producing a photocatalyst having the above-described configuration. The manufacturing method can be carried out by a light supporting method or a thermal method.

The manufacturing method by the optical support method mixes titanium dioxide liquid and a noble metal containing precursor; Reducing the mixture to prepare titanium dioxide having a precious metal supported on its surface; Adding titanium dioxide having the precious metal supported on the surface thereof to a phosphoric acid solution; The process of heat-processing the obtained product is included. Hereinafter, each process is explained in full detail.

First, the titanium dioxide liquid and the noble metal-containing precursor are mixed. At this time, the amount of the noble metal-containing precursor is suitably used in an amount such that the supported amount of the noble metal in the final photocatalyst is 0.1 to 10 parts by weight, preferably 0.5 to 1.5 parts by weight based on 100 parts by weight of titanium dioxide. Water may be used as the solvent in the titanium dioxide liquid, but is not limited thereto. In addition, the concentration of the titanium dioxide liquid can be appropriately adjusted.

As the noble metal-containing precursor, a compound containing a noble metal such as Pt, Pd, Ru, Au, Ag, Ni, Cu, or a combination thereof may be used. For example, chloroplatinic acid (H ₂ PtCl ₆ ), palladium chloride (palladium chloride, PdCl ₂ ), ruthenium chloride (RuCl ₃ ), chloroauric acid (HAuCl ₄ ). Silver nitrate (AgNO ₃ ), nickel chloride (Nickel chloride, NiCl ₂ ), copper chloride (CuCl ₂ ), or a combination thereof.

The mixture is then reduced. This reduction step can be carried out by a photodeposition method.

The photosupporting method can be carried out by further using an electron donor material. As the electron donor material, methanol, ethanol, an organic acid or a combination thereof may be used. The amount of the electron donor material used may be 0.01 to 10 M. In addition, the optical support method is carried out while irradiating light, the light that can be used may be a mercury lamp, Xe-arc lamp and the like.

In the reduction process, the platinum precursor is supported on the surface of titanium dioxide while being reduced to platinum.

Subsequently, titanium dioxide supported by platinum prepared in the above step is added to the phosphoric acid solution. The phosphoric acid solution may be an aqueous phosphoric acid solution, and the concentration of the phosphoric acid solution is appropriately 0.001 to 1M.

The obtained product is subjected to heat treatment. According to this heat treatment step, the binding of the phosphate group to the titanium dioxide surface is strengthened, thereby preparing a photocatalyst according to one embodiment of the present invention.

The heat treatment process may be carried out at 50 to 1000 ℃ for 1 minute to 10 hours. When the heat treatment process is performed during the temperature range and the time, it is possible to obtain an advantage that the bonding of the surface phosphate groups is enhanced.

Among the methods for producing the photocatalyst of the present invention, the thermal method includes a step of mixing a titanium dioxide liquid and a noble metal-containing precursor and heat treating the mixture. At this time, the titanium dioxide liquid, the noble metal-containing precursor and the mixing ratio thereof are the same as those of the above optical supporting method, a detailed description thereof will be omitted.

The heat treatment process may be performed for 10 minutes to 10 hours at 200 to 1000 ℃ while injecting hydrogen into the reducing agent. When the heat treatment process is performed during the temperature range and the time, the precious metal ions on the surface are reduced and supported on the titanium dioxide surface.

The photocatalyst production method of the present invention can produce a photocatalyst having excellent photocatalytic activity in a simple and economical process.

Other specific details of embodiments of the present invention are included in the following detailed description.

Since the photocatalyst prepared by the production method of the present invention shows excellent pollutant decomposition efficiency, it can be usefully used for wastewater treatment.

Hereinafter, specific embodiments of the present invention will be described. However, the embodiments described below are only intended to illustrate or explain the present invention, and thus the present invention should not be limited thereto.

(Example 1)

TiO ₂ aqueous suspension (Degussa P25) and chloroplatinic acid (H ₂ PtCl ₆ , 12.2M) at a concentration of 0.0005% by weight were mixed in the presence of an electron donor, methanol (1M), to which a 200-W mercury lamp was added. UV light was irradiated for 30 minutes.

After performing the irradiation step, the filtration and washing steps were carried out to obtain Pt / TiO ₂ powder. The Pt loading was measured using an inductively coupled plasma-atomic emission spectroscopy (ICP-AES, Spectro), and it was about 0.5 parts by weight to 100 parts by weight of TiO ₂ .

Subsequently, 0.1 g of the obtained Pt / TiO ₂ powder was dispersed in an aqueous solution of phosphoric acid (Sigma-Aldrich, concentration: 30 mM, usage: 100 mL), and the dispersion was stirred for 5 hours. The stirred product was filtered to give a filtrate, which was dried for 1.5 hours in a 100 ° C. oven and then heat treated at 300 ° C. for 1 hour.

The heat treatment product was washed thoroughly with distilled water to remove weakly bound phosphate anions, thereby preparing a Pt / TiO ₂ photocatalyst having a phosphate group bound to the surface.

(Example 2)

A Pt / TiO ₂ photocatalyst having a phosphate group bonded to the surface thereof was prepared in the same manner as in Example 1, except that a phosphoric acid aqueous solution having a concentration of 5 mM was used.

(Example 3)

A Pt / TiO ₂ photocatalyst was prepared in the same manner as in Example 1 except that a phosphoric acid aqueous solution having a concentration of 100 mM was used.

(Example 4)

A Pt / TiO ₂ photocatalyst having a phosphate group bonded to the surface thereof was prepared in the same manner as in Example 1 except that the heat treatment was performed at 100 ° C.

(Example 5)

A Pt / TiO ₂ photocatalyst having a phosphate group bonded to the surface thereof was prepared in the same manner as in Example 3 except that the heat treatment was performed at 100 ° C.

(Comparative Example 1)

TiO ₂ was used as the photocatalyst.

(Comparative Example 2)

0.1 g of TiO ₂ powder was dispersed in an aqueous solution of phosphoric acid (Sigma-Aldrich, 30 mM, 100 mL), and the dispersion was stirred for 5 hours. The stirred product was filtered to give a filtrate, which was dried for 1.5 hours in a 100 ° C. oven and then heat treated at 300 ° C. for 1 hour.

The heat treatment product was thoroughly washed with distilled water to remove weakly bound phosphate anions, thereby preparing a TiO ₂ photocatalyst having a phosphate group bound to the surface.

(Comparative Example 3)

Pt / TiO ₂ powder prepared in Example 1 was used as a photocatalyst.

(Comparative Example 4)

A Pt / TiO ₂ photocatalyst having a fluorine group bonded to the surface thereof was prepared in the same manner as in Example 1 except that sodium fluoride was used instead of phosphoric acid.

(Comparative Example 5)

A TiO ₂ photocatalyst having a phosphoric acid group bonded to the surface thereof was prepared in the same manner as in Comparative Example 2 except that a phosphoric acid aqueous solution having a concentration of 5 mM was used.

(Comparative Example 6)

A TiO ₂ photocatalyst having a phosphoric acid group bonded to the surface thereof was prepared in the same manner as in Comparative Example 2 except that a phosphoric acid aqueous solution having a concentration of 100 mM was used.

* Physical property measurement

1) Measurement of surface atomic composition

Surface atomic compositions of the photocatalysts of Example 2 and Comparative Examples 1, 3, and 5 were measured by X-ray photoelectron spectroscopy (XPS, Kratos, XSAM 800 pci) using Mg Kα light as an excitation source. The results are shown in Figs. 3 (a), (d), (b) and (c), respectively. As shown in FIG. 3, the photocatalyst of Example 2 obtained a P 2p spectrum of 133.5 eV binding energy, which corresponds to a phosphate group bonded to the TiO ₂ surface, and the energy band of Pt 4f was supported on the TiO ₂ surface. Corresponds to Pt ⁰ . From this result, it can be seen that the photocatalyst of Example 2 is supported by Pt and that a phosphate group is bonded.

2) Energy-filtered transmission electron microscope (EFTEM) and high-resolution transmission electron microscope (HRTEM) measurements

Elemental analysis of the photocatalyst prepared according to Example 1 was measured with an energy-filtered transmission electron microscope (EFTEM) equipped with an omega energy filter (JEM-2200FS microscope calibrated with Cs). Among the measurement results, a zero-loss filtering image result is shown in FIG. 4A, and elemental mapping of Ti, O, and P is shown in FIGS. 4B and 4B. c) and (d), respectively. In addition, a high-resolution transmission electron microscope photograph is shown in Fig. 4E. As shown in FIG. 4, the P element is well dispersed on the TiO ₂ surface (FIG. 4D), and the Pt element is present as a cluster having a size of about 2-4 nm (FIG. 4E). )).

3) Surface charge measurement

In order to determine the surface charges of the photocatalysts of Example 1 and Comparative Examples 1 to 3, 0.0003 g of the photocatalyst was added to water to prepare an aqueous suspension, and the zeta potential of the aqueous suspension was electrophoretic light scattering photoelectron. Spectrophotometer, ELS 8000, Otsuka) was used to measure the pH change. The results are shown in Fig. As shown in FIG. 5, the zero zeta potential point (PZZP) of the photocatalyst of Comparative Example 1 was obtained at about pH 6.5, which is consistent with the literature values. In addition, it can be seen that the photocatalyst of Comparative Example 3 on which Pt was loaded was obtained at a pH value substantially similar to the zeta potential point as the photocatalyst of Comparative Example 1. On the contrary, it can be seen that the PZZPs of the photocatalysts of Example 1 and Comparative Example 2 were obtained at a value significantly lowered to pH about 5.0.

4) P / Ti atomic ratio measurement

The atomic% of P and Ti contained in the photocatalysts of Examples 1 to 5 and Comparative Examples 1 to 3 was measured by XPS, and the P / Ti atomic ratio was calculated from the results, and the results are shown in Table 1 below. It was.

H ₃ PO ₄ concentration (mM) Heat treatment temperature (캜) P (atomic%) Ti (atomic%) P / Ti atomic ratio Comparative Example 1 0 - - 26.2 - Comparative Example 2 30 300 3.4 23.2 0.15 Comparative Example 3 0 - - 25.7 - Example 2 5 300 1.9 24.2 0.08 Example 1 30 300 3.4 23.0 0.15 Example 3 100 300 4.0 22.0 0.18 Example 4 30 100 1.5 24.8 0.06 Example 5 100 100 2.4 24.3 0.10

As shown in Table 1, it can be seen that the P / Ti atomic ratio present on the surface of the photocatalyst increases as the concentration of phosphoric acid used or the heat treatment temperature increases. This is because the heat treatment process strengthens the chemical bond between the phosphate anion and the hydroxyl group present on the TiO ₂ surface (Scheme 1,> means the TiO ₂ surface).

[Reaction Scheme 1]

> Ti-OH + HOPO ₃ ^2- → Ti-O-PO ₃ ^2- + H ₂ O

* Catalytic activity measurement

1) Degradation of Phenolic Compounds

In a cylindrical Pyrex reactor (30 mL) with a quartz window, the photocatalysts of Examples 1 to 3 and Comparative Examples 1 to 3, 5 and 6 were dispersed in distilled water at a concentration of about 0.5 g / L to prepare a suspension.

To the suspension was added 4-chlorophenol (4-CP) 300M and bisphenol A (BPA) 200M under the conditions shown in Table 2 below, and the pH was adjusted to 3.0 using HClO ₄ (5M). Subsequently, the pH-adjusted mixture was stirred for 30 minutes, so that the adsorption equilibrium of 4-chlorophenol and bisphenol A was achieved in the photocatalyst.

The equilibrated mixture was then passed through a 10-cm IR water filter and a cutoff filter (λ> 320 nm) using a 300-W Xe arc lamp (Oriel) as the light source, containing the equilibrated mixture Focused in a cylindrical Pyrex reactor. That is, as a result, ultraviolet rays with lambda> 320 nm were irradiated.

The incident light intensity (320 nm <lambda <500 nm) of the irradiated ultraviolet rays was measured using a ferrioxalate actinometery, and found to be about 2.8 X 10 ^-3 einstein min ^-1 L ^-1 .

The reactor was opened to prevent the lack of dissolved O ₂ (dioxygen), and magnetic stirring was performed during the irradiation process. Sample fractions were removed from the reactor during the irradiation process and filtered through a 0.45-μm polytetrafluoroethylene (PTFE) filter (Miillipore) to remove photocatalyst particles.

In addition, to examine the effects of using t-butyl alcohol (OH radical scavenger), an experiment was also performed in which t-butyl alcohol was added to the suspension under the conditions shown in Table 2 below.

In all experiments it was found that chloride was formed due to the decomposition of 4-chlorophenol.

The decomposition degree measured, that is, photocatalytic decomposition activity was calculated by the relative speed ( krel = k (catalyst) / k (Comparative Example 1 catalyst)) and is shown in Table 2 below.

catalyst Phosphoric Acid Concentration (mM) t-butyl alcohol addition amount (mM) krel (4-CP) krel (BPA) Comparative Example 1 0 0 1.0 1.0 Comparative Example 5 5 0 1.2 - Comparative Example 2 30 0 1.3 2.0 Comparative Example 6 100 0 0.9 - Comparative Example 3 0 0 1.1 1.5 Comparative Example 3 0 10 0.7 1.0 Example 2 5 0 2.7 - Example 1 30 0 3.2 4.9 Example 1 30 10 0.6 1.0 Example 3 100 0 2.9 -

As shown in Table 2 above, It can be seen that the photocatalysts of Examples 1, 2, and 3 show much better activity than those of Comparative Examples 1, 2, 3, 5, and 6.

In more detail, in Table 2, the relative rate ( krel ) values for decomposition of 4-CP and BPA of the photocatalyst of Comparative Example 2 were 1.3 and 2.0, respectively, and in Comparative Example 3 were 1.1 and 1.5, respectively. In the case of Example 1, it can be seen that 3.2 and 4.9, respectively.

From these results, it can be seen that the photocatalyst surface-modified with platinum and phosphoric acid improves the photocatalyst efficiency more than the photocatalyst surface-modified only with platinum and the photocatalytic surface-modified only with phosphoric acid. It can be seen that there is a synergy effect that is superior to the sum of the effects of the modified photocatalyst and the surface modified photocatalyst only with phosphoric acid.

In addition, it can be seen that the effect of the addition of the hydroxyl radical scavenger t-butyl alcohol has a different effect in the photocatalysts of Comparative Example 3 and Example 1. That is, as shown in Table 2, when the t-butyl alcohol was added to the photocatalyst of Example 1, the photocatalytic resolution of 4-CP and BPA was significantly decreased (4-CP: krel decreased from 3.2 to 0.6, BPA: krel decreased from 4.9 to 1.0, reduced by about 80%), and in Comparative Example 3, relatively small (4-CP: krel decreased from 1.1 to 0.7, BPA: krel decreased from 1.5 to 1.0, About 35% reduction). This result is considered to be because the role of the OH radical plays an important role in decomposing the phenolic compound in the photocatalyst of Example 1, rather than the photocatalyst of Comparative Example 3.

2) OH radical generation measurement

In a cylindrical Pyrex reactor (30 mL) with a quartz window, the photocatalysts of Example 1 and Comparative Examples 1 to 3 were dispersed in distilled water at a concentration of about 0.5 g / L to prepare a suspension. 1 mM of cumarin was added to this suspension, and the pH was adjusted to 3.0 using HClO ₄ (5M).

Subsequently, using a 300-W Xe arc lamp (Oriel) as a light source, the light beam was passed through a 10-cm IR water filter and a cutoff filter (λ> 320 nm) to the resulting mixture, and into the cylindrical Pyrex reactor containing the mixture. Focused. That is, as a result, ultraviolet rays with lambda> 320 nm were irradiated.

The incident light intensity (320 nm <lambda <500 nm) of the irradiated ultraviolet rays was measured using a ferrioxalate actinometery, and found to be about 2.8 X 10 ^-3 einstein min ^-1 L ^-1 .

The reactor was opened to prevent deficiency of dissolved O 2 (dioxygen) and magnetic stirring was performed during the irradiation process. Sample fractions were removed from the reactor during the irradiation process and filtered through a 0.45-μm polytetrafluoroethylene (PTFE) filter (Miillipore) to remove photocatalyst particles.

According to the ultraviolet irradiation, the cumin was converted to 7-hydroxycumarin, and the fluorescence emission intensity of the 7-hydroxycumarin thus produced was measured using a spectrofluorometer (Shimadzu RF-5301).

This experiment is to find out that phosphate group and Pt bonded to TiO ₂ promote OH radical generation. That is, the photocatalyst generates OH radicals by reacting holes and water (or OH ⁻ ) by a photoreaction, and reacts with cumin mixed with these OH radicals to form 7-hydroxycumarin, thus 7-hydroxy It is understood that the more the sycumarin is produced, the more OH radicals are formed.

The results are shown in Fig. As shown in FIG. 6, the photocatalyst of Comparative Example 2 in which a phosphate group was bonded and Comparative Example 3, in which platinum was supported, had a somewhat improved emission intensity compared to Comparative Example 1. In addition, it can be seen that Example 1, in which a phosphate group is bonded and platinum is supported, is markedly improved, that is, exhibits about 4 times or more emission intensity compared to Comparative Examples 2 and 3. From this result, it can be seen that the OH radical formation effect is greatly increased when phosphate bonds and platinum support are carried out together, rather than only phosphate groups or platinum alone.

3) Measurement of photocurrent

The photocurrent amounts of the photocatalysts of Example 1 and Comparative Examples 1 to 3 were measured, and the results are shown in FIG. 7. The photocurrent measurement experiment was performed as follows. A photocatalyst was dispersed in distilled water at a concentration of about 0.5 g / L to prepare a suspension, and a working electrode was prepared by immersing an inert Pt electrode plate (1 × 1 cm 2).

A photoelectrochemical cell having a three-electrode system using the working electrode, graphite rod counter electrode and Hg / Hg ₂ Cl ₂ / KCl reference electrode was prepared. At this time, in an aqueous solution prepared by dissolving 0.1M LiClO ₄ in water as an electrolyte, 0.5 mM of FeCl ₃ -6H ₂ O was transferred to an electron shuttle (Fe ³⁺ / Fe ²⁺⁾ and electrons from the semiconductor composite to the Pt electrode plate. And a pH of 2.0, in which 200 µM of 4-chlorophenol was added as an electron donor material.

Connected to the computer, constant potential electrolysis device (potentiostat, EG & G 263 A2) and, in the photoelectric chemical cells, Fe ³⁺ / Fe ²⁺ couple (+ 0.53V _SCE) than the reduction potential, a positive potential of the potential of the use of (+ 0.7 V _SCE ) was applied, and the photocurrent was measured while irradiating λ> 320 nm ultraviolet rays while continuously purging nitrogen gas into the suspension. The results are shown in Fig.

As shown in FIG. 7, it can be seen that the photocatalysts of Example 1 and Comparative Example 3 exhibited an improved photocurrent amount compared to the photocatalyst of Comparative Example 1, and in particular, Example 1 exhibited the most improved photocurrent amount. On the contrary, it can be seen that the photocatalyst of Comparative Example 2 exhibited a lower amount of photocurrent than that of Comparative Example 1. From this result, the phosphate group does not improve the electron transfer rate like Pt, but when the phosphate group and Pt are together, the electron transfer rate is improved than that of Pt, and these results are similar to the results shown in Table 2.

4) Determination of photocatalytic degradation efficiency at various pH

In a cylindrical Pyrex reactor (30 mL) with a quartz window, the photocatalysts of Example 1 and Comparative Examples 1-3 were dispersed in distilled water at a concentration of about 0.5 g / L to prepare a suspension. 500 M of 2,4-dichlorophenoxy acetic acid (2,4-D, Sigma) was added to this suspension. The pH of the resulting solution was adjusted to 3.0, 6.5 and 11.0 using HClO ₄ (5M) or NaOH (5M), respectively. Subsequently, the pH-adjusted mixed solution was stirred for 30 minutes, so that the adsorption equilibrium of 2,4-dichlorophenoxy acetic acid was achieved in the photocatalyst.

Subsequently, using a 300-W Xe arc lamp (Oriel) as the light source in the equilibrated mixture, a light beam was passed through a 10-cm IR water filter and a cutoff filter (λ> 320 nm) to form a cylindrical container containing the equilibrated mixture. Focused in a Pyrex reactor. That is, as a result, ultraviolet rays having a lambda> 320 nm were irradiated.

The incident light intensity (320 nm <lambda <500 nm) of the irradiated ultraviolet rays was measured using a ferrioxalate actinometery, and found to be about 2.8 X 10 ^-3 einstein min ^-1 L ^-1 .

The reactor was opened to prevent the lack of dissolved O ₂ (dioxygen), and magnetic stirring was performed during the irradiation process. Sample fractions were removed from the reactor during the irradiation process and filtered through a 0.45-μm polytetrafluoroethylene (PTFE) filter (Miillipore) to remove photocatalyst particles.

The decomposition degree of 2,4-diclophenoxy acetic acid (2,4-D) according to the experiment was measured, and the results are shown in FIGS. 8A, 8B, and 8C, respectively. In addition, the amount of 2,4-dichlorophenol (2,4-DCP), which is an intermediate product generated in the decomposition reaction, was measured at pH 3.0, 6.5, and 11.0, and the results are shown in FIGS. 9 (d), (e), and (f). ), Respectively.

In addition, the amount of chloride produced as a reaction product was measured at pH 3.0, 6.5, and 11.0, and the results are shown in FIGS. 10 (g), (h), and (i), respectively.

Referring to (a), (b) and (c) of FIG. 8, it can be seen that the photocatalyst of Example 1 has the best efficiency of decomposing 2,4-dichlorophenoxy acetic acid at pH 6.5 and 11.

In addition, as shown in (d), (e) and (f) of FIG. 9, the photocatalyst of Example 1 is an intermediate product, and the toxic substance 2,4-dichlorophenol is made smaller than the photocatalysts of Comparative Examples 1 to 3. It can be seen that. In addition, as shown in (g), (h) and (i) of Figure 10, it can be seen that the photocatalyst of Example 1 forms more chloride than the photocatalysts of Comparative Examples 1 to 3 decomposition products. This is because the photocatalysts of Comparative Examples 1 and 3 mainly degrade the carboxyl groups of 2,4-dichlorophenoxy acetic acid, as shown in FIG. The production rate of chloride appears to be high because it mainly decomposes the benzene ring of phenoxy acetic acid. The photocatalyst of Comparative Example 2 also decomposes the benzene ring of 2,4-dichlorophenoxy acetic acid mainly but appears to have a low chloride production rate because the transfer of excited electrons is not fast.

5) pH stability

0.15 g of the photocatalysts of Example 1 and Comparative Example 4 were added to 300 ml of water adjusted to pH 3.0, 4.5, 6.5, 9.0 and 11, and stirred for 3 hours to desorb the phosphoric acid group and the fluorine group. Subsequently, filtration and drying were performed. The atomic% of P and Ti and the atomic% of F and Ti of the dried product were measured by XPS to obtain P / Ti and F / Ti atomic ratios. In addition, the atomic% of P and Ti and the atomic% of F and Ti of the surface-modified titanium dioxide before desorption of the phosphate group and the fluorine group were measured by XPS, and from the result, (P / Ti) ₀ (or (F / Ti) ₀ )

From the results obtained, (P / Ti) / (P / Ti) ₀ and (F / Ti) / (F / Ti) ₀ are calculated and plotted as (P / Ti) r and (F / Ti) r, respectively. 11 is shown. As shown in FIG. 11, the photocatalyst of Example 1 was stable up to pH 11, while the photocatalyst of Comparative Example 4 began to decrease in the amount of surface fluorine as the pH was increased, and surface fluorine was completely desorbed at pH 11. This result is because the fluorine anion bound to the titanium dioxide surface easily falls under the basic condition, while the phosphate group is well bound under the basic condition.

6) Light stability measurement

In a cylindrical Pyrex reactor (30 mL) with a quartz window, suspensions were prepared by dispersing the photocatalysts of Example 1 and Comparative Example 3 in distilled water at a concentration of about 0.5 g / L. 300M of 4-chlorophenol (4-CP) was added to this suspension, and the pH was adjusted to 3.0 using HClO ₄ (5M). Subsequently, the pH-adjusted mixture was stirred for 30 minutes, so that the adsorption equilibrium of 4-chlorophenol on the photocatalyst was achieved.

Subsequently, using a 300-W Xe arc lamp (Oriel) as the light source in the equilibrated mixture, a light beam was passed through a 10-cm IR water filter and a cutoff filter (λ> 320 nm) to form a cylindrical container containing the equilibrated mixture. Focused in a Pyrex reactor. That is, as a result, ultraviolet rays with lambda> 320 nm were irradiated.

The incident light intensity (320 nm <lambda <500 nm) of the irradiated ultraviolet rays was measured using a ferrioxalate actinometery, and found to be about 2.8 X 10 ^-3 einstein min ^-1 L ^-1 .

The reactor was opened to prevent the lack of dissolved O ₂ (dioxygen), and magnetic stirring was performed during the irradiation process. Sample fractions were removed from the reactor during the irradiation process and filtered through a 0.45-μm polytetrafluoroethylene (PTFE) filter (Miillipore) to remove photocatalyst particles.

In this way, the degree of decomposition of 4-chlorophenol was measured (1 cycle).

This process was repeated 4 cycles, 4-M chlorophenol (4-CP) 300M was added for each cycle, and this suspension was stirred for 30 minutes, and the adsorption equilibrium of 4-chlorophenol in a photocatalyst was carried out.

The results are shown in FIG. As shown in FIG. 12, it can be seen that the photocatalysts of Example 1 and Comparative Example 3 have almost maintained their activity even after several uses .

The present invention is not limited to the above embodiments, but may be manufactured in various forms, and a person skilled in the art to which the present invention pertains has another specific form without changing the essential features of the present invention. It will be appreciated that the present invention may be practiced as. It is therefore to be understood that the above-described embodiments are illustrative in all aspects and not restrictive.

Claims (14)

Precious metal loaded titanium dioxide (TiO ₂ ); And
Phosphoric acid group (PO ₄ ^3- ) bonded to the titanium dioxide surface
Surface modified photocatalyst comprising a. The method of claim 1,
Wherein said photocatalyst has a P 2p spectrum and a spectrum due to a noble metal upon XPS measurement. The method of claim 1,
In the photocatalyst, the surface modified photocatalyst having a P / Ti atomic ratio of 0.01 to 0.5. The method of claim 1,
In the photocatalyst, the surface modified photocatalyst having a P / Ti atomic ratio of 0.05 to 0.2. The method of claim 1,
The amount of the precious metal supported is 0.1 to 10 parts by weight based on 100 parts by weight of titanium dioxide surface-modified photocatalyst. The method of claim 1,
The supported amount of the noble metal is 0.5 to 1.5 parts by weight based on 100 parts by weight of titanium dioxide surface modified photocatalyst. The method of claim 1,
The precious metal is Pt, Pd, Ru, Au, Ag, Ni, Cu or a combination thereof surface modified photocatalyst. The method of claim 1,
The photocatalyst is used as a photocatalyst selected from the group consisting of a photocatalyst for wastewater treatment, a photocatalyst for an air purifier, a photocatalyst for purifying air, a photocatalyst for purifying water, a photocatalyst for removing odors, and a photocatalyst for antibacterial activity. Mixing titanium dioxide liquid with a noble metal-containing precursor;
Reducing the mixture to prepare titanium dioxide carrying precious metals;
Adding titanium dioxide carrying the noble metal to the phosphoric acid solution;
Heat treatment of the obtained product
A method of making a surface modified photocatalyst comprising a process. 10. The method of claim 9,
The reduction is a method of producing a surface-modified photocatalyst that is carried out by a photo supporting method. 10. The method of claim 9,
And the noble metal-containing precursor is a compound containing a noble metal which is Pt, Pd, Ru, Au, Ag, Ni, Cu or a combination thereof. 10. The method of claim 9,
The heat treatment process is a method of producing a surface-modified photocatalyst that is carried out at 50 to 1000 ℃ for 1 minute to 10 hours. Mixing titanium dioxide liquid with a noble metal-containing precursor;
Heat treatment of the mixture
A method of making a surface modified photocatalyst comprising a process. The method of claim 13,
The heat treatment process is a method of producing a surface-modified photocatalyst that is carried out for 10 minutes to 10 hours at 200 to 1000 ℃ while injecting hydrogen into the reducing agent.

Images