KR20100003902A - Photoelectrocatalytic oxidation electrode for treatment of non-degradable waste and method for treating non-degradable waste using same - Google Patents

Abstract

PURPOSE: A photoelectrocatalytic oxidation electrode for treatment of non-degradable waste water and a non-degradable waste water treatment method using the same are provided to prevent the recombination of electrons and holes by creating an electric potential difference and maximize decomposition efficiency of non-degradable material. CONSTITUTION: A photoelectrocatalytic oxidation electrode for treatment of non-degradable waste water comprises a conductive support and a photocatalyst layer. The conductive support is selected from the group consisting of graphite, carbon nanotube, Indium-Tin-Oxide and their mixture. The photocatalyst layer including a first optical catalyst of mesoporous and a TiO2 second optical catalyst of mixed crystal type is formed on the supporter.

Description

Photoelectrocatalytic oxidation electrode for refractory wastewater treatment and non-degradable wastewater treatment method using same

The present invention relates to an electrode for photoelectrocatalytic oxidation for hardly decomposable wastewater treatment and a method for treating hardly decomposable wastewater using the same. More particularly, the catalyst can be easily recovered and the potential difference is generated in the hardly decomposable wastewater treatment. Electrode for photocatalytic oxidation for difficult-decomposable wastewater treatment, which can prevent recombination of holes and electrons, and maximize the decomposition efficiency of hardly decomposable substances contained in wastewater through continuous generation of OH radicals It relates to a processing method.

Photocatalyst related research is directly related to the development of solar energy utilization technology. Solar energy utilization technology can be largely divided into solar cells, solar heat, photocatalysts, etc. The core of the photocatalyst is to directly convert solar energy into chemical energy. The conversion to chemical energy was mainly due to the production of hydrogen by photochemical decomposition of water using chemical fuel synthesis and chemical reactions. However, 30 years later, the current technology remains at the basic level, whereas the decomposition of environmental pollutants using photocatalyst and photocatalyst Although the use technology as a functional coating material appeared later in time, significant advances have been made in both academic and practical aspects, and commercial products are already on the market.

Photocatalyst applications mainly function as coating materials, and their applications are very broad and diverse. Specifically, it is used in various places such as medical supplies, kitchen and residential goods, various construction materials, road equipment, buildings, automobile supplies, and clothing. In the area of environmental purification, researches related to the development of indoor air purifiers have been mainstream, and NOx and volatile organic compound (VOC) removal technologies have been steadily being studied. On the other hand, research activities and paper publications are very active in the field of water treatment, but the products used are rare. On the other hand, new applications of photocatalysts are continuously being explored, and researches are being actively conducted to supplement the disadvantages of existing photocatalysts, which have recently been reported.

The photocatalysis method used for the hardly degradable wastewater treatment disperses the TiO ₂ photocatalyst in water and irradiates UV with energy above the band gap to generate a pair of electrons and holes on the TiO ₂ photocatalyst surface. It is a method of treating organic pollutants in water by direct and indirect oxidation of electrons and holes. Although the treatment efficiency is relatively excellent, there is a problem in that the recovery of the dispersed photocatalyst is not easy, and additives such as oxygen and hydrogen peroxide must be continuously added to lower the rate at which holes are recombined with electrons as much as possible.

 Among the above problems, a method that is attempted to compensate for the problem of recovering the dispersed photocatalyst is a method of fixing the photocatalyst to various supports. As a method of fixing a photocatalyst to a support, three methods of impregnation, chemical vapor deposition (CVD), and sol-gel are generally used. The immobilized photocatalyst is slightly different depending on the coating method, but the amount of the photocatalyst to be coated is very small and the surface area is very low compared to the powder. In addition, since the thickness of the photocatalyst is thin, there is a disadvantage that the treatment efficiency of the organic material is significantly reduced. As a method of compensating the problems of the immobilized photocatalyst, various methods, such as a method of increasing the activity of the photocatalyst itself and enhancing the activity, and a method of forming and preparing a composite so that a larger amount of the catalyst can participate in the photocatalytic reaction Are being tried.

In order to compensate for the disadvantage that the electron acceptor such as oxygen or hydrogen peroxide must be continuously added to prevent the rapid recombination of the electrons and holes, research on photoelectrocatalytic oxidation is being actively conducted. This method uses TiO ₂ on an electrically conductive support. It is a method of fixing photocatalysts such as the like and artificially generating a potential difference in the immobilized photocatalyst to prevent recombination of holes and electrons, thereby enabling continuous generation of OH radicals. Since the photocatalytic oxidation method uses TiO ₂ fixed to the support, a separate photocatalyst recovery device is not required. The photoelectrocatalytic oxidation method does not require a photocatalyst recovery device, and generates an electric potential difference with a potentiostat to move toward the counter electrode. Because it prevents recombination, there is an advantage in that it is possible to reduce the use of consumed chemicals such as oxygen or hydrogen peroxide, which are electron acceptors, to prevent recombination of electrons and holes. In addition, since the electrons generated by light circulate from the counter electrode to the outside, the efficiency is much higher than that of photocatalytic oxidation, and is present in the ionic state in water by the reduction reaction by the electrons moved to the counter electrode. It can be removed by reducing the heavy metal and there is an advantage that can be recovered if expensive precious metal is present.

However, for the effective application of this method, it is essential to manufacture electrodes having excellent electrical conductivity and organic decomposition efficiency.

The present invention is to solve the problems of the prior art as described above, by fixing the photocatalyst to the support having an electrical conductivity to prepare an electrode for the photoelectric catalytic oxidation, it is possible to easily recover the catalyst in the treatment of difficult-decomposable wastewater In order to minimize the rate at which holes recombine with electrons, additives such as oxygen and hydrogen peroxide do not need to be continuously added. An object for photoelectrocatalytic oxidation for difficult-decomposable wastewater treatment is provided.

The present invention also provides a method for treating hardly decomposable wastewater which exhibits excellent decomposition efficiency using the photoelectrocatalytic oxidation electrode as described above.

However, technical problems to be achieved by the present invention are not limited to the above-mentioned problems, and other technical problems will be clearly understood by those skilled in the art from the following description.

In order to achieve the above object, according to a first embodiment of the present invention comprises a conductive support, and a photocatalyst layer formed on the support, the photocatalyst layer is a first photocatalyst of mesoporous, and anatase type: rutile type Provided is a photoelectrocatalytic oxidation electrode for refractory wastewater treatment comprising a mixed crystal type TiO ₂ second photocatalyst comprising a crystal structure of 80:20 to 60:40 in a weight ratio.

According to a second embodiment of the present invention, there is provided a hardly degradable wastewater treatment method using the photoelectrocatalytic oxidation electrode.

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

The photoelectrocatalytic oxidation electrode according to the present invention can easily recover the catalyst in the treatment of difficult-decomposable wastewater, prevent the recombination of holes and electrons by generating a potential difference, and also enables the continuous generation of OH radicals. It is possible to maximize the decomposition efficiency of hardly decomposable substances such as formic acid, metal oxides, metal organic compounds and mordants contained in the waste water.

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.

Unless otherwise specified in the present specification, "mesoporous" means including pores having a pore diameter of 2 to 50 nm, and "nanoparticles" refers to particles having a diameter of 2 to 100 nm.

As the photoelectrocatalytic oxidation electrode, an electrode in which TiO ₂ is fixed in the form of a thin film has been generally used. The most widely used sol-gel method is used to fix TiO ₂ in the form of a thin film. However, the sol-gel method has no problem in forming a thin film when TiO _{2 is} coated on a glass or ceramic carrier. There are many difficulties in forming a mechanically and thermally stable electrode. For the preparation of the photoelectrocatalytic oxidation electrode, the durability according to the dispersion degree, type, performance, properties of the support, binder type, and molding strength should be considered.

Accordingly, in the present invention, by using an electrode support that is chemically stable and excellent in conductivity, and forms a photocatalyst layer using heterogeneous photocatalysts having different characteristics on the electrode support, chemical, mechanical, and thermal stability are achieved, resulting in high decomposition efficiency and The electrode for photoelectrocatalytic oxidation with durability can be manufactured.

That is, the electrode for photovoltaic catalytic oxidation for the hardly decomposable wastewater treatment according to the first embodiment of the present invention includes a conductive support, and a photocatalyst layer formed on the support, wherein the photocatalyst layer is a first photocatalyst of mesoporous, and A mixed crystal crystalline TiO ₂ second photocatalyst comprising an anatase: rutile crystalline phase in a weight ratio of 80:20 to 60:40.

The support may be used without particular limitation as long as it has conductivity and has appropriate mechanical strength. Specifically, one selected from the group consisting of graphite, carbon nanotubes, indium tin oxide (ITO), and mixtures thereof may be used, and a glass substrate coated with the indium tin oxide may also be used.

Among these, graphite having high electrical conductivity and smooth emission of electrons generated by a photocatalytic reaction to an external circuit, and carbon nanotubes having excellent mechanical strength and electrical conductivity are more preferable. Do. In addition, among the carbon nanotubes, single-wall nanotubes (SWNTs) having a stiffness of about 1TPa and excellent in electric conductivity of 10 ³ S / cm are more preferable.

The photocatalyst layer includes heterogeneous photocatalysts having different characteristics.

Specifically, a mixed crystal type TiO ₂ second photocatalyst comprising a mesoporous first photocatalyst and an anatase: rutile crystalline phase in a weight ratio of 80:20 to 60:40. The first photocatalyst and the second photocatalyst may form a photocatalyst layer in a mixed state, and more preferably, the first photocatalyst may form a photocatalyst layer in a state where the first photocatalyst is surface treated by the second photocatalyst.

The first photocatalyst has a large specific surface area to exhibit excellent catalyst efficiency, and can be used without particular limitation as long as it has mesoporosity among those normally used as photocatalysts. Specifically, mesoporous TiO ₂ is mentioned.

The TiO ₂ may be crystalline or amorphous, and in the crystalline form, may have an anatase type, a rutile type, a brookite type, and a mixed type thereof.

The mesopores included in the first photocatalyst preferably have a pore diameter of 4.4 to 7.5 nm. When it has a pore diameter in the above range, it is preferable in terms of the effect of improving the catalytic activity and the balance of mechanical strength.

As the second photocatalyst, a mixed crystal type TiO ₂ containing an anatase type: rutile type crystal phase in a weight ratio of 80:20 to 60:40 may be used.

The reactivity varies depending on the crystal structure of the photocatalyst. The second photocatalyst has a mixed crystal phase of the anatase type and the rutile type crystal phase, and thus exhibits excellent photoactivity.

The second photocatalyst preferably comprises an anatase crystalline phase and a rutile crystalline phase in a weight ratio of 80:20 to 60:40, more preferably 70:30 to 60:40. When including the respective crystal phase in the weight ratio as described above it can exhibit an excellent photoactivity improvement effect.

The second photocatalyst may be porous or nonporous, preferably nonporous.

The first photocatalyst and the second photocatalyst having physical properties having the above properties are preferably included in the photocatalyst layer in a weight ratio of 2: 1 to 1: 1. When mixed in the above weight ratio, it is preferable because the photoactivity can be improved by increasing the surface conductivity in the photocatalyst layer.

The photocatalyst layer may further include one selected from the group consisting of a conductive agent, a binder, and a mixture thereof.

The conductive agent is for imparting conductivity to the electrode, and may be used without particular limitation as long as it is a material having electronic conductivity without causing chemical change in the battery. Specific examples thereof may include natural graphite, artificial graphite, carbon black, acetylene black, ketjen black, carbon fiber, and the like, and one of these conductive agents may be selected and used.

The conductive agent is preferably included in 10 to 1000 parts by weight, more preferably 30 to 50 parts by weight with respect to 100 parts by weight of the photocatalyst. When included in the content range as described above can exhibit excellent conductivity without fear of deterioration of the photocatalyst efficiency.

The binder serves to improve the durability of the electrode as a material stable to the electrochemical reaction. The binder may be one selected from the group consisting of water-soluble polymers, hydrophobic polymers, electrically conductive polymers, derivatives thereof, and combinations thereof. Examples of the water-soluble polymer include polyvinyl alcohol, carboxymethyl cellulose, methyl cellulose, ethyl cellulose, isopropyl cellulose, hydroxymethyl cellulose, hydroxyethyl cellulose, hydroxypropyl methyl cellulose, cyanoethyl cellulose, and ethyl-hydroxyethyl cellulose. , Polyoxyethylene, poly N-vinylpyrrolidone, polyvinylacetate and one selected from the group consisting of a combination thereof are possible. The hydrophobic polymer may be polyvinyl fluoride, polyvinylidene fluoride, tetrafluoroethylene polymer, trifluoroethylene polymer, difluoroethylene polymer, ethylene-tetrafluoroethylene copolymer, tetrafluoroethylene-hexafluoro One selected from the group consisting of a low propylene copolymer, a tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer, a trifluoroethylene chloride polymer, polyethylene, polypropylene, and combinations thereof is possible. Also polyaniline, polypyrrole, polyacetylene, polyacene, polythiophene, polyalkylthiophene, poly (p-phenylene), polyphenylene, polyphenylene sulfide, polyphenylenevinylene, polyfuran, polyacetylene, poly With polyselenophene, polyisothianaphthene, polythiophenevinylene, polyperinaphthalene, polyanthracene, polynaphthalene, polypropylene, polyazulene, derivatives thereof and copolymers thereof It is also possible to use one or more electrically conductive polymers selected from the group consisting of. In addition, other phenol resins may be used.

The polyaniline (Polyaniline: PANI) is a well-known conductive polymer, easy manufacturing and processing, has been studied a lot of physical and chemical, and is a polymer that is commercialized on a relatively good stability and large scale. In addition, polyaniline and polyethylene have an advantage of excellent strength by forming an interpenetrated network (IPN).

In addition, the carboxyalkyl cellulose is also widely used as a conductive binder has a hydroxyl group at the end. As a result, the contact angle in the water can be lowered and the conductivity can increase the reaction of the interface in the water.

More preferably, as the binder, polyaniline, carboxyalkyl cellulose, polyethylene, polyaniline emeraldine salt and mixtures thereof may be used.

Since the photocatalytic oxidation reaction is a surface reaction, as the amount of the photocatalyst on the electrode surface increases, the treatment efficiency of the organic material also increases. However, if the amount of the photocatalyst is excessively increased, the electrical conductivity decreases, which affects the treatment efficiency. In addition, since the binder affects the shape of the electrode and the strength in the water during manufacturing, it is preferable to properly adjust the ratio of the photocatalyst and the conductive binder. Specifically, the binder is preferably included in 20% by weight or less, more preferably 5 to 20% by weight based on the total weight of the photocatalyst layer. When included in the photocatalytic layer within the content range as described above, it is preferable because it can exhibit excellent conductivity and the adhesion effect of the photocatalyst layer to the support without fear of lowering the photocatalytic efficiency.

The photoelectrocatalytic oxidation electrode having the above configuration exhibits the best UV absorption in the ultraviolet wavelength region of 210 to 400 nm.

The photoelectrocatalytic oxidation electrode according to the embodiment of the present invention as described above may be prepared by applying a composition for forming a photocatalyst layer including a photocatalyst on a conductive support by a conventional slurry coating method, and drying it.

The photocatalyst composition may be prepared by dispersing a first photocatalyst and a second photocatalyst in a solvent. In this case, the first photocatalyst and the second photocatalyst are the same as described above.

As the solvent, alcohols such as ethanol, isopropyl alcohol, n-propyl alcohol, butyl alcohol, water, dimethylacetamide, dimethyl sulfoxide, N-methylpyrrolidone and the like can be preferably used. The solvent may be included in the amount of the balance, and the amount of the solvent may be appropriately adjusted in consideration of the applicability of the composition.

The photocatalyst composition may further include one selected from the group consisting of a conductive agent, a binder, and a mixture thereof, and the conductive agent and the binder are the same as described above.

The coating process may be a screen printing method, a spray coating method or a coating method using a doctor blade or the like depending on the viscosity of the composition, but is not limited thereto.

The electrode according to the present invention can be prepared by drying and removing the solvent in the composition applied on the support after the coating step.

However, when the organic substance used as the other additive remains in the composition, an additional firing process may be further performed.

According to a second embodiment of the present invention, a method for treating hardly decomposable wastewater using the photoelectrocatalytic oxidation electrode is provided.

The non-degradable wastewater treatment method using the photoelectrocatalytic oxidation electrode can be carried out by a conventional method, for example, a wastewater treatment apparatus equipped with an ultraviolet lamp, a potentiostat, a stirrer, and a TOC analyzer. After the electrode is installed in the wastewater, the hardly decomposable organic substance in the wastewater can be decomposed.

The photoelectrocatalytic oxidation electrode according to the present invention can decompose metal oxides, metal organic compounds, mordants, etc. in addition to formic acid in wastewater.

The electrode is a mechanism in which OH radicals and hydrogen are formed by oxidation and reduction reactions, and can be applied to the production of electrodes for fuel cells in addition to wastewater treatment.

Hereinafter, the present invention will be described in more detail with reference to the following examples, but the following examples are only preferred embodiments of the present invention, and the present invention is not limited to the following examples.

( Example  One)

Secondary distilled water was added to the titanium isopropoxide to form titanium dioxide particles, and hydrochloric acid was added to the particles to prepare TiO ₂ nanoparticles. The precipitate formed after adding H ₂ O to the prepared TiO ₂ nanoparticles was separated from the precipitate and H ₂ O by using a centrifuge. After centrifugation, hydrochloric acid was slowly added to the precipitate while stirring to prepare a titanium stabilizing solution in which TiO ₂ nanoparticles were dispersed. In the titanium stabilization solution, P25 (Degussa P25, manufactured by Degussa Corp., anatase type: Luti-type crystalline phase = 70: 30 weight ratio, specific surface area 50 m ² g ⁻¹ ) sufficiently dispersed in anhydrous ethanol (Abs. EtOH) After addition, the triblock copolymer (pluronic P123) of poly (ethylene oxide) poly (propylene oxide) poly (ethylene oxide) was dissolved in an organic solvent of 1-propanol, and mixed with a solution prepared to prepare a light absorption layer-forming composition. It was. At this time, P123: titanium isopropoxide: HCl: H ₂ O: 1-propanol was used in a molar ratio of 1: 109.7: 181: 7: 1800, and the TiO ₂ and P25 were mixed to a weight ratio of 2: 1.

The prepared photocatalyst layer-forming composition was applied to an ITO glass substrate using a spin coater at 1,000 rpm for 1 minute. The ITO glass substrate coated with the composition for forming a photocatalyst layer was dried for 24 hours at 40 ° C. and 20% or less humidity, and the dried electrode was calcined at 450 ° C. for 4 hours to remove the surfactant of P123 used as a template. An electrode was prepared.

( Comparative example  One)

The precipitate formed after adding H ₂ O to titanium isopropoxide was separated from the precipitate and H ₂ O by using a centrifuge. After centrifugation, hydrochloric acid was slowly added to the precipitate while stirring to prepare a titanium stabilizing solution in which TiO ₂ nanoparticles were dispersed. The triblock copolymer (pluronic P123) of poly (ethylene oxide) poly (propylene oxide) poly (ethylene oxide) as a template was dissolved in an organic solvent of 1-propanol, mixed with a titanium stabilizing solution and stirred for about 1 hour to form a light absorption layer. A composition for preparation was prepared. At this time, P123: titanium isopropoxide: HCl: H ₂ O: 1-propanol was used in a molar ratio of 1: 109.7: 181: 7: 1800.

The prepared photocatalyst layer-forming composition was applied to an ITO glass substrate using a spin coater at 1,000 rpm for 1 minute. The ITO glass substrate coated with the composition for forming a photocatalyst layer was dried at 40 ° C. under 20% humidity for 24 hours, and the electrode dried to form pores in the TiO ₂ nanoparticles was formed by removing P123 used as a template. The electrode was prepared by baking for 4 hours at.

(Property evaluation)

The size of the pores formed in the photocatalyst layer was measured using a transmission electron microscope and a pore meter with respect to the electrode prepared in Example 1. The results are shown in FIGS. 1A-1D.

The pore measuring device is an ellipse that can measure the surface area, pore distribution and pore size in the electrode by adsorbing or desorbing toluene to the electrode and correcting the errors caused by the substrate using an elliposometry in the machine itself. A Somitri porosimeter was used.

1A is a high magnification transmission electron microscope observation photograph of the electrode of Example 1, Figure 1B is a low magnification transmission electron microscope observation photograph of the electrode of Example 1.

Figure 1c is a graph showing the results of observing the pore distribution of the electrode of Example 1, Figure 1d is a graph showing the results of observing the distribution according to the pore diameter in the electrode of Example 1.

In FIG. 1C, P / Po on the x-axis is a relative pressure obtained by dividing the pressure (P) of the adsorbed material by the saturated vapor pressure (Po) of the material, and the y-axis shows the adsorption amount by volume (cc / g).

In FIG. 1D, the y-axis shows the volume (cc / g) of nitrogen adsorbed or desorbed per 1 g of catalyst when the nitrogen is adsorbed or desorbed into the pores at a constant pressure.

1A and 1B, it can be seen that mesopores having a uniform pore size are uniformly dispersed in the photocatalyst layer of the electrode. In addition, as shown in Figure 1d it can be seen that the size of the pores included in the photocatalyst layer of the electrode is about 4.4 to 7.5nm.

( Photoelectric  Catalytic oxidation reaction)

Photoelectrocatalytic oxidation experiments were performed on the electrodes prepared in Example 1 and Comparative Example 1.

Photoelectrocatalytic oxidation experiment was carried out in the following manner.

In the photocatalytic oxidation test apparatus, the reactor is a borosilicate material in rectangular form (75 mm Х 100 mm Х 125 mm, thickness 2.5 mm), which is open in air and has a capacity of 800 mL. As a light source, a UV lamp having a main wavelength of 365 nm (black light: manufactured by Sankyo Denki, Japan, F15T8BSB, 15W) was used, and was irradiated from the side of the reactor (100 mm 125 mm). The intensity of the ultraviolet ray reaching the sample was controlled by using the distance between the sample and the UV lamp, and the intensity of the ultraviolet ray was measured using a radiometer (manufactured by San Gabriel, CA91778, USA). The photoelectrocatalytic oxidation electrode is installed in the center of the reactor, and the electrode submerged in solution has an area of 35 cm ² It was made to be. The measurement results are shown in FIG.

2 is a graph showing the results of photoelectrocatalytic oxidation experiments on the electrodes of Example 1 and Comparative Example 1. FIG.

As shown in FIG. 2, the electrode of Example 1 made by mixing mesoporous TiO ₂ and P25 was UV light at a wavelength of 362 nm with respect to a reference wavelength of 365 nm compared with the electrode of Comparative Example 1 made using mesoporous TiO. The water absorption was better. This result is because the thickness of the photocatalyst layer was increased by the addition of P25 having a mixed crystal structure in the case of the electrode of Example 1, thereby increasing the amount of photocatalyst on the surface.

(Evaluation of Formic Acid Decomposition)

Formic acid decomposition effects of the photoelectrocatalytic oxidation method (PEC) and the photocatalytic oxidation method (PC) were evaluated for the electrodes prepared in Example 1 and Comparative Example 1. Formic acid decomposition effect was analyzed by TOC by taking samples at regular intervals after the photoreaction. The results are shown in FIGS. 3 and 4.

3 is a graph showing the results of evaluating the formic acid decomposition effect by the photoelectrocatalytic oxidation method (PEC) and photocatalytic oxidation method (PC) over time with respect to the electrode prepared in Example 1 and Comparative Example 1,

Figure 4 is a graph showing the results of measuring the amount of formic acid decomposition by the photoelectrocatalytic oxidation method (PEC) and photocatalytic oxidation method (PC) of the electrode prepared in Example 1 and Comparative Example 1.

In FIG. 3, C / Co on the Y-axis denotes a value analyzed by a total organic compound analyzer (TOC analyzer), which is sampled per hour and analyzed by a total organic compound analyzer (TOC analyzer).

As the photoreaction proceeds, formic acid begins to decompose. 3 and 4, the decomposition efficiency of formic acid by the electrode according to Comparative Example 1 was 10%, the formic acid decomposition efficiency by the electrode according to Example 1 was 57%. That is, formic acid decomposition efficiency by the electrode of Example 1 was found to be about 5 times higher than the electrode of Comparative Example 1. This is believed to be the result of increasing the decomposition efficiency of formic acid by adding P25, which has excellent photoactivity, to increase the amount of TiO _{2 on} the surface. In addition, it was investigated that the decomposition efficiency of photoelectrocatalytic oxidation (PEC) was higher than the photocatalytic oxidation efficiency (PC) of both the electrodes of Example 1 and Comparative Example 1. This is because the photoelectrocatalytic oxidation smoothly prevented recombination of electrons and holes.

( Example  2)

The precipitate formed after adding H ₂ O to titanium isopropoxide was separated from the precipitate and H ₂ O by using a centrifuge. After centrifugation, hydrochloric acid was slowly added to the precipitate while stirring to prepare a titanium stabilizing solution in which TiO ₂ nanoparticles were dispersed.

P25 (Degussa P25, manufactured by Degussa Corp., anatase type: Lutie type = 70:30 weight ratio, specific surface area 50 m ² g ^-1 ) was sufficiently dispersed in anhydrous ethanol (abs. EtOH), and then P25 and graphite were weight ratio Furnace was mixed at 5: 5, and polyethylene and polyaniline emeraldine salts were further added as a binder to prepare a mixed solution. At this time, the amount of the binder added was 20% by weight of the total amount.

The mixed solution was added to the titanium stabilized solution prepared above, and then mixed with a solution prepared by dissolving a triblock copolymer (pluronic P123) of poly (ethylene oxide) poly (propylene oxide) poly (ethylene oxide) in an organic solvent. A composition for forming a light absorption layer was prepared. At this time, P123: titanium isopropoxide: HCl: H ₂ O: 1-propanol was used in a molar ratio of 1: 109.7: 181: 7: 1800, and the TiO ₂ and P25 were mixed to a weight ratio of 2: 1.

The composition for forming the light absorption layer was sufficiently dispersed for 20 minutes using a homogenizer (US-600NCVP, manufactured by Nissei), and the graphite substrate was immersed in the mixed solution and then baked in a 130 ^° C. oven for 90 minutes to make a graphite substrate. An electrode coated with a mixture of TiO ₂ and graphite on a support was prepared.

( Comparative example  2)

P25 (Degussa P25, manufactured by Degussa Corp., specific surface area 50 m ² g ^-1 ) was sonicated in anhydrous ethanol for at least 2 hours, and then dispersed in graphite (timcal grafite & carbon, KS6) and polyethylene and polyaniline emeraldine as binders. The salt was added and stirred at room temperature for 24 hours. Thereafter, the mixture was dried for at least 24 hours in a 55 ^° C. oven to evaporate the solvent to obtain a TiO ₂ -graphite powder. The prepared TiO ₂ -graphite powder was put in a molding machine having a size of 100 mm Х 50 mm and molded at a pressure of 3 ton, and then baked at 130 ^° C. for 90 minutes to prepare an electrode.

(Evaluation of Formic Acid Decomposition)

The electrode prepared in Example 1, Example 2 and Comparative Example 2 was carried out in the same manner as described above to evaluate the formic acid decomposition effect, the results are shown in FIG.

5 is a graph showing the results of evaluating the formic acid decomposition effect by the photoelectrocatalytic oxidation method and the photocatalytic oxidation method for the electrodes prepared in Examples 1, 2 and Comparative Example 2.

As shown in FIG. 5, the electrode according to Comparative Example 2 showed a formic acid decomposition efficiency of less than 50%, while the electrodes according to Examples 1 and 2 both exhibited a formic acid decomposition efficiency of 55% or more. In particular, it is considered that the electrode of Example 2 can exhibit excellent conductivity and strength compared to the electrode of Comparative Example 2 by using a graphite support, and thus exhibits more excellent formic acid decomposition efficiency.

The photoelectrocatalytic oxidation of the three electrodes showed better formic acid decomposition efficiency than the photocatalytic oxidation, but the electrodes of Examples 1 and 2 showed better photoelectrocatalytic oxidation than the electrodes of Comparative Example 2. This is because photooxidation and photoreduction occur smoothly by preventing the recombination of excited electrons with holes in the photoelectrocatalytic oxidation reaction.

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 technical spirit or essential features of the present invention. It will be appreciated that the present invention may be practiced as. Therefore, it should be understood that the embodiments described above are exemplary in all respects and not restrictive.

Figure 1a is a high magnification transmission electron microscope observation photograph of the electrode of Example 1.

Figure 1b is a low magnification transmission electron microscope observation photograph of the electrode of Example 1.

Figure 1c is a graph showing the results of observing the pore distribution for the electrode of Example 1.

Figure 1d is a graph showing the results of observing the distribution according to the pore diameter in the electrode of Example 1.

2 is a graph showing the results of photoelectrocatalytic oxidation experiments on the electrodes of Example 1 and Comparative Example 1. FIG.

3 is a graph showing the results of evaluating the formic acid decomposition effect by the photoelectrocatalytic oxidation method (PEC) and photocatalytic oxidation method (PC) over time with respect to the electrode prepared in Example 1 and Comparative Example 1.

Figure 4 is a graph showing the results of measuring the amount of formic acid decomposition by the photoelectrocatalytic oxidation method (PEC) and photocatalytic oxidation method (PC) of the electrode prepared in Example 1 and Comparative Example 1.

5 is a graph showing the results of evaluating the formic acid decomposition effect by the photoelectrocatalytic oxidation method and the photocatalytic oxidation method for the electrodes prepared in Examples 1, 2 and Comparative Example 2.

Claims (12)

Conductive support; And It includes a photocatalyst layer formed on the support, The photocatalyst layer is made of mesoporous An electrode for photocatalytic oxidation for hardly decomposable wastewater treatment comprising a first photocatalyst and a mixed crystal crystalline TiO ₂ second photocatalyst comprising an anatase type: rutile type crystal structure in a weight ratio of 80:20 to 60:40. The method of claim 1, The support is a photoelectric catalytic oxidation electrode that is selected from the group consisting of graphite, carbon nanotubes, indium tin oxide and mixtures thereof. The method of claim 1, The first photocatalyst is a photoelectric catalytic oxidation electrode surface-treated by a second photocatalyst. The method of claim 1, The first photocatalyst is a photovoltaic catalytic oxidation electrode comprising mesopores having a pore diameter of 4.4 to 7.5nm. The method of claim 1, The first photocatalyst is a mesoporous TiO ₂ electrode for photocatalytic oxidation. The method of claim 1, The first photocatalyst and the second photocatalyst are in the photocatalyst layer is included in the photocatalyst layer in a weight ratio of 2: 1 to 1: 1. The method of claim 1, The photocatalyst layer is a photoelectrocatalytic oxidation electrode that further comprises selected from the group consisting of a conductive agent, a binder, and mixtures thereof. The method of claim 7, wherein The conductive agent is selected from the group consisting of natural graphite, artificial graphite, carbon black, acetylene black, ketjen black, carbon fiber, metal powder, metal fibers and mixtures thereof. The method of claim 7, wherein Wherein the conductive agent is 10 to 1000 parts by weight based on 100 parts by weight of the photocatalyst, the electrode for catalytic oxidation. The method of claim 7, wherein Wherein the binder is selected from the group consisting of water-soluble polymers, hydrophobic polymers, conductive polymers and mixtures thereof. The method of claim 7, wherein The binder is a photoelectrocatalytic oxidation electrode is included in less than 20% by weight based on the total weight of the photocatalyst layer. A method for treating hardly decomposable wastewater using the photoelectrocatalytic oxidation electrode according to any one of claims 1 to 11.

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