KR101910443B1 - Method for fabricating self-doped titanium dioxide photoanode and photoelectrochemical small-scale water purification system thereof - Google Patents

Abstract

In Sikkim the invention by a self-doped Ti ⁴⁺ of titanium dioxide (TiO ₂₎ to Ti ³⁺ enhance the optical absorption and electrical conductivity of the titanium dioxide, and to the Ti ⁴⁺ Ti ³⁺ self improving the doping efficiency The present invention relates to a self-doped titanium dioxide photoelectrode capable of inhibiting re-oxidation of Ti ³⁺ to Ti ⁴⁺ and a photoelectrochemical water treatment apparatus using self-doped titanium dioxide photoelectrode, A method of manufacturing a doped titanium dioxide photoelectrode includes: forming a titanium oxide nanostructure on a titanium base material by anodizing a titanium base material into a fluorine-containing electrolyte; Heat treating the titanium base material to convert it into an amorphous titanium oxide nanostructure; Depositing a promoter nanoparticle on a titanium base material including an amorphous titanium oxide nanostructure; A step of reducing the Ti ⁴⁺ of the amorphous titanium oxide nanostructure to Ti ³⁺ by applying a power source to the titanium base material deposited with the catalyst nanoparticles in the pH buffer solution; Characterized in that comprises a; and Ti ³⁺ is self-converting to a self-doping by firing doped amorphous titanium oxide nano-crystalline structure of titanium oxide nano-structure.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a self-doped titanium dioxide photoelectrode and a photoelectrochemical water treatment apparatus using self-doped titanium dioxide photoelectrode,

The present invention is a, more particularly, Ti ⁴⁺ of titanium dioxide (TiO ₂₎ relates to a photoelectric chemical water treatment apparatus using a manufacturing method and a self-doped titanium dioxide photo-electrode of the titanium dioxide photoelectrodes doping itself to Ti ³⁺ self which in self Sikkim for increasing the light absorption of titanium dioxide and doped electrical conductivity, along with to the Ti ³⁺ Ti ⁴⁺ Ti ³⁺ self improving the doping efficiency can be suppressed from being re-oxidized to Ti ⁴⁺ Doped titanium dioxide photoelectrode, and a photoelectrochemical water treatment apparatus using the self-doped titanium dioxide photoelectrode.

Recently, domestic exposure to humidifier disinfectant has attracted attention as a problem of the hazardousness of the drug - based management technology of existing life - style products. PHMG (polyhexamethylene guanidine), which is the main component of humidifier disinfectant, can induce periodic damage and cancer and cause genetic deformation. Although the market for these products is growing rapidly, regulation of chemical management due to the use of hazardous substances is somewhat behind.

Meanwhile, the need for advanced oxidation technology, which is a powerful water treatment technology, has been increased to cope with water pollution due to the degradable trace organic pollutants. The photocatalyst-based oxidation technique is a substitute technology for the conventional oxidation process based on hydrogen peroxide and ozone. A number of methods have been proposed. In addition, the method of removing harmful microorganisms is mainly chemical-based chlorine disinfection, but chlorine disinfection is resistant to some infectious bacteria such as Legionella, so it is difficult to disinfect sufficiently, and when chlorine components are present in water, , Thereby generating harmful disinfection by-products such as THMs (Trihalomethanes), chloramines and the like.

Conventional water treatment methods using titanium oxide (TiO ₂ ), which is a typical photocatalyst, are used to immobilize the support on a support, such as light absorption limited to ultraviolet rays (UV), low electric conductivity, recombination of photochemically generated electron-holes The water treatment efficiency is deteriorated. In this respect, a method has been proposed in which immobilized titanium dioxide is used as a photo-anode and an external voltage is applied together with light irradiation to promote the oxidation-reduction reaction (see Korean Patent Publication No. 2016-60191 ). However, this method did not overcome the limit of titanium dioxide's low conductivity and ultraviolet light absorption.

The present applicant has proposed a method of electrically doping a part of Ti ⁴⁺ with Ti ³⁺ by electrically cathodizing the titanium oxide nanostructure by improving the electrical conductivity of titanium dioxide and increasing the light absorptivity of the visible region (See Korean Patent No. 1400861 and Korean Patent No. 1401655). However, since these methods electrically reduce the titanium dioxide nanostructure formed with the anatase structure by heat treatment, the self-doping is confined to the surface of the nanostructure due to the stabilized crystal structure, thereby improving the light absorptivity and electrical conductivity There is a limitation in that it is limited. Further, the Ti ³⁺ produced by the reduction of Ti ⁴⁺ not been stabilized is likely to be re-oxidized to Ti ^4+.

On the other hand, in a photoelectrochemical water treatment system using a photo electrode (anode), hydrogen gas may be generated through a reduction reaction occurring at the cathode, which may cause a safety problem. Therefore, there is a need for a method capable of supporting the formation of an oxidizing agent required for water treatment through a reduction reaction of the surface of the cathode instead of delaying the hydrogen generation reaction.

Korean Patent Publication No. 2016-60191 Korean Patent No. 1400861 Korea Patent No. 1401655

In Sikkim the present invention is one made in view the above problems, by the self-doped Ti ⁴⁺ of titanium dioxide (TiO ₂₎ to Ti ³⁺ improve the light absorptivity of the titanium dioxide and the electrical conductivity, Ti ⁴⁺ Doped titanium dioxide photoelectrode capable of enhancing the self-doping efficiency of Ti ³⁺ to Ti ³⁺ and inhibiting the reoxidization of Ti ³⁺ to Ti ⁴⁺ , and a photoelectron utilizing a self-doped titanium dioxide photoelectrode The object of the present invention is to provide a chemical water treatment apparatus.

The present invention is titanium dioxide (TiO by ensuring that the process proceeds to a Ti ³⁺ Ti ⁴⁺ self-doping step prior to the crystallization of the titanium dioxide (TiO ₂₎ a self-doped, as well as progress in the internal surface of the titanium dioxide (TiO _{2) 2} ) to improve the light absorption and electrical conductivity of titanium dioxide by lowering the energy band gap of the titanium dioxide, and a photoelectrochemical method using a self-doped titanium dioxide photoelectrode Another object is to provide a water treatment apparatus.

According to another aspect of the present invention, there is provided a method of manufacturing a self-doped titanium dioxide photoelectrode, comprising: forming a titanium oxide nanostructure on a titanium base material by anodizing a titanium base material into a fluorine-containing electrolyte; Heat treating the titanium base material to convert it into an amorphous titanium oxide nanostructure; Depositing a promoter nanoparticle on a titanium base material including an amorphous titanium oxide nanostructure; A step of reducing the Ti ⁴⁺ of the amorphous titanium oxide nanostructure to Ti ³⁺ by applying a power source to the titanium base material deposited with the catalyst nanoparticles in the pH buffer solution; Characterized in that comprises a; and Ti ³⁺ is self-converting to a self-doping by firing doped amorphous titanium oxide nano-crystalline structure of titanium oxide nano-structure.

The step of putting the titanium base material to which the co-catalyst nanoparticles deposited in the pH buffer solution is applied to the reduction of Ti ⁴⁺ to Ti of the amorphous titanium oxide nanostructure ³⁺ power; is a hydrogen ion (H ⁺⁾ the pH buffer solution and Ti ⁴⁺ ions Ti ⁴⁺ of by reaction with the progress of the reduction process to Ti ^3+, the oxygen vacancy (oxygen vacancy) in the amorphous titanium oxide nano-structure is formed, and oxygen vacancies (oxygen vacancy) and Ti ⁴⁺ The reduction of Ti ⁴⁺ to Ti ³⁺ by the reaction of ions proceeds.

Oxygen vacancies are generated in the amorphous titanium oxide nanostructure where the co-catalyst nanoparticles are oxidized to oxide nanoparticles where the co-catalyst nanoparticles are located, and the generated oxygen vacancies are converted into the Ti ⁴ of the amorphous titanium oxide nanostructure ⁺ Ions, and the Ti ⁴⁺ ions are reduced to Ti ³⁺ ions.

The co-catalyst nanoparticles are transition metals. The co-catalyst nanoparticles are platinum-based transition metals, and are either Pt or Pd. In addition, the co-catalyst nanoparticles are either Cu or Ag.

The pH buffer solution is any one of a KH ₂ PO ₄ solution and a NaHCO ₃ solution.

The photoelectrochemical water treatment apparatus using the self-doped titanium dioxide photoelectrode according to the present invention includes a photoelectrochemical water treatment tank providing a space where the photoelectrochemical reaction proceeds; A photocathode and a cathode provided in the photoelectrochemical water treatment tank; A voltage supply device for applying power to the cathode and the cathode; And a light source for irradiating a visible ray or ultraviolet ray to the photocathode, wherein the photocathode is a titanium dioxide photo electrode having a transition metal oxide and a Ti ³⁺ ion self-doped.

The negative electrode is composed of a conductive material, two electron reduction the catalyst is supported as possible of the dissolved oxygen, dissolved when the power is applied to the cathode oxygen, hydrogen ions produced by the reduction reaction of the negative electrode (H ⁺⁾ and the second electronic (2e ^- Hydrogen peroxide (H ₂ O ₂ ) is produced by the reaction between the hydrogen peroxide

The catalyst capable of two-electron reduction of dissolved oxygen is any one of carbon nanotubes, graphene oxide, and carbon fibers. In addition, the transition metal oxide is an oxide of a platinum transition metal, or a copper oxide (CuO) and a silver oxide (AgO).

The photo-electrochemical reaction is a reaction between organic radicals (OH) generated by a photocatalytic mechanism of a self-doped titanium dioxide photoelectrode and an organic contaminant, the reaction between hydrogen peroxide (H ₂ O ₂ ) Includes reactions with contaminants.

The self-doped titanium dioxide photoelectrode according to the present invention and the photoelectrochemical water treatment apparatus using the self-doped titanium dioxide photoelectrode have the following effects.

According to enhance the optical absorption and electrical conductivity characteristics by doping self the Ti ^{3 +} for titanium dioxide, platinum-based transition to form an oxygen vacancy (oxygen vacancy) the titanium dioxide through the oxidation of the metal Ti ^{3 +} the oxygen vacancy (oxygen by so coupling the vacancy) it can inhibit re-oxidation of the Ti ^{3 +.}

Further, the self-doping process is performed before the crystallization process of the titanium dioxide nanostructure is performed to increase the self-doping ratio within the titanium dioxide, thereby lowering the energy band gap of the titanium dioxide, thereby further improving the light absorption and electrical conductivity characteristics.

In addition, the generation of Photoelectrochemical according as the water purifying apparatus constructed by supporting a two-electron reduction the catalyst capable of dissolved oxygen in the negative electrode produced in the hydrogen ion (H ⁺⁾ is a hydrogen peroxide (H ₂ O ₂₎ in the water treatment oxidant with Sikkim inhibition The water treatment efficiency can be improved.

1 is a flowchart illustrating a method of manufacturing a self-doped titanium dioxide photoelectrode according to an embodiment of the present invention.
2 is a schematic view of an electro-optic chemical water treatment apparatus using a self-doped titanium dioxide photoelectrode according to an embodiment of the present invention.
FIG. 3 is a graph showing the results of X-ray photoelectron spectroscopy on the surfaces of the self-doped titanium dioxide photoelectrode according to Experimental Example 1 and the self-doped titanium dioxide photoelectrode according to the comparative example.
4 shows the results of measurement of the removal efficiency of methylene blue according to the change of the light source and voltage application conditions in Experimental Example 3. FIG.
FIG. 5 shows the results of measuring the removal efficiency of E. coli according to changes in the light source and voltage application conditions in Experimental Example 3. FIG.
6 is a graph showing the removal efficiency of methylene blue according to the change of the light source in Experimental Example 3. FIG.

The present invention provides a technique for manufacturing a self-doped titanium dioxide photoelectrode.

Titanium dioxide (TiO ₂ ), as mentioned in the 'Background of the Invention', plays a role of generating radicals of hydroxyl (· OH) under ultraviolet irradiation environment to remove contaminants in the water, and the anode of the electrochemical water treatment apparatus when used as an anode, promotes the redox reaction of aquatic pollutants. However, as mentioned in the Background of the Invention, titanium dioxide (TiO ₂ ) itself has a problem of low electric conductivity and limited light absorption by ultraviolet rays. To solve this problem, TiO ₂ of TiO ₂ ⁴⁺ is reduced to a form of self-doping with Ti ³⁺ (see Korean Patent No. 1400861 and Korean Patent No. 1401655).

The present invention relates to a process for preparing self-doped titanium dioxide by reducing Ti ⁴⁺ of TiO ₂ to Ti ³⁺ , thereby improving the self-doping efficiency of Ti ⁴⁺ to Ti ³⁺ , ³⁺ is inhibited from being reoxidized to Ti ⁴⁺ , and a technique capable of absorbing visible light by Ti ³⁺ and maintaining excellent electrical conductivity characteristics is proposed.

As a way to suppress with to the Ti ⁴⁺ Ti ³⁺ self improving the doping efficiency of the Ti ³⁺ it is reoxidized into Ti ^4+, titanium dioxide before proceeding with the reduction process to the Ti ⁴⁺ Ti ³⁺ A method of depositing a cobalt-based cocatalyst on TiO ₂ is applied. The platinum-series co-catalysts such as Pt and Pd deposited on titanium dioxide (TiO ₂ ) are oxidized to PtO and PdO during the reduction of Ti ³⁺ to Ti ⁴⁺ , and titanium dioxide (TiO ₂ Oxygen vacancies are generated in the oxygen vacancies. In this process, Ti ⁴⁺ of titanium dioxide (TiO ₂ ) is combined with oxygen vacancy and reduced to Ti ³⁺ . Since Ti ³⁺ is combined with the oxygen vacancy of titanium dioxide (TiO ₂ ), Ti ³⁺ forms a stable form and is inhibited from being reoxidized to Ti ⁴⁺ .

The reduction of Ti ⁴⁺ to Ti ³⁺ can be achieved by the reaction of Ti ⁴⁺ and hydrogen ions (H ⁺ ) in addition to the above-described promoter system. In the present invention, the reduction process of Ti ⁴⁺ to Ti ³⁺ proceeds in a pH buffer solution, thereby inducing the reaction of Ti ^{4+ with} the hydrogen ion (H ⁺ ) supplied from the pH buffer solution.

In summary, the reduction of Ti ⁴⁺ to Ti ^{3+ in} the present invention is ^accomplished by 1) the reaction of Ti ⁴⁺ with the oxygen vacancy produced by the oxidation of the cocatalyst, and 2) the reaction of hydrogen ions (H ⁺ ) And the reaction of Ti ⁴⁺ . As self-doping of Ti ⁴⁺ into Ti ³⁺ proceeds as described above, the self-doping efficiency is improved, and as the Ti ³⁺ bonds to the oxygen vacancy generated by the oxidation of the cocatalyst, Ti ³⁺ can be inhibited from being re-oxidized to Ti ⁴⁺ .

Hereinafter, a method of manufacturing a self-doped titanium dioxide photo-electrode according to an embodiment of the present invention and a photo-electrochemical small-sized water treatment apparatus using a self-doped titanium dioxide photo electrode will be described in detail. First, a method of manufacturing a self-doped titanium dioxide photoelectrode according to an embodiment of the present invention will be described.

Referring to FIG. 1, a plate or mesh-like titanium (Ti) base material is prepared (S101). A pretreatment process can be applied to remove contaminants on the titanium matrix. Specifically, a titanium base material may be put in an organic solvent such as acetone to perform ultrasonic cleaning, and a native oxide on a titanium base material may be removed by heating a titanium base material in a reducing solvent such as oxalic acid and heating .

After the pretreatment process is completed, the titanium oxide nanostructure formation process is performed (S102). Specifically, a titanium base material is placed in a fluorine-containing electrolyte and anodized to form a titanium oxide nanostructure on the titanium base material. Specifically, a titanium base material is placed in an ethylene glycol solution containing about 0.1 M of fluorine ions, about 5 wt% of distilled water, about 1 wt% of lactic acid, and a voltage of 50 to 100 V relative to a Pt- The titanium oxide nanostructure is formed on the titanium base material by applying it to the base material for about 1 to 3 hours. The lactic acid may not be contained in the ethylene glycol solution. The resulting titanium oxide nanostructures have shapes such as nanotubes, nanorods, nanoneedles, and nanofibers.

The titanium oxide nanostructure produced in order to enhance the mechanical strength of the titanium oxide nanostructure formed on the titanium base material may be removed and the titanium oxide nanostructure may be produced by anodizing again. If the anodic oxidation is performed again after removing the titanium oxide nanostructure, the titanium oxide nanostructure first grows at the site where the titanium oxide nanostructure is removed, thereby improving the mechanical strength of the titanium oxide nanostructure. Removal of the resulting titanium oxide nanostructure can be achieved by ultrasonication in distilled water containing about 10 wt% ethanol, and the addition of ethanol can be omitted.

In a state where a titanium oxide nanostructure is formed on a titanium base material, the titanium base material is baked at a low temperature of 200 DEG C or less for about 1 hour to amorphize the titanium oxide nanostructure, and an electrolyte remaining in the titanium base material and the titanium oxide nanostructure (S103).

Next, the process of depositing the promoter nanoparticles on the amorphous titanium oxide nanostructure is performed (S104). The co-catalyst nanoparticles are platinum transition metals such as Pt and Pd, and can be deposited through a physical vapor deposition process such as chemical vapor deposition or sputtering. The co-catalyst nanoparticles are oxidized in the form of oxides in the self-doping process described below. Oxygen vacancies are formed in the titanium oxide nanostructure by oxidation of the cocatalyst, and oxygen vacancy and Ti ⁴⁺ The reaction proceeds, which will be described later in detail. Further, when the finally completed self-doped crystalline titanium oxide nanostructure is used for the purpose of disinfecting the water treatment apparatus, Cu or Ag may be utilized as the co-catalyst nanoparticles.

In a state where the catalyst nanoparticles are deposited on the amorphous titanium oxide nanostructure, a self-doping process is performed (S105). Here, self-doping refers to the effect of doping Ti ³⁺ ions into an amorphous titanium oxide nanostructure, and actually, a Ti ⁴⁺ ion of an amorphous titanium oxide nanostructure is reduced to Ti ³⁺ ions. The self-doping process proceeds as follows.

After the titanium base material including the amorphous titanium oxide nanostructure having the catalyst nanoparticles deposited on the pH buffer solution is placed on the cathode, power is applied to the counter electrode for 60 to 240 seconds at a current density of 10 to 20 mA / cm ² . By such power application, cathodic reduction occurs in the titanium base material, and the Ti ⁴⁺ ions of the amorphous titanium oxide nanostructure are reduced to Ti ³⁺ ions.

Specifically, the hydrogen ions (H ⁺⁾ amorphous Ti ⁴⁺ ions to Ti ⁴⁺ ions and reaction of the titanium oxide nano-structure of the pH buffer solution is reduced to Ti ³⁺ ion (see formula 1 below). As the pH buffer solution, a KH ₂ PO ₄ solution or a NaHCO ₃ solution can be used. The reduction of Ti ⁴⁺ to Ti ³⁺ by the reaction of hydrogen ions (H ⁺ ) and Ti ⁴⁺ ions in the pH buffer solution can be defined as a reduction reaction by proton intercalation.

The reduction of Ti ⁴⁺ to Ti ³⁺ proceeds by the reaction of oxygen vacancy and Ti ⁴⁺ ions in addition to the reduction reaction by proton intercalation. Specifically, the co-catalyst nanoparticles such as Pt or Pd deposited on the amorphous titanium oxide nanostructure in the above-described self-doping process are oxidized to PtO or PdO. As the promoter nanoparticles are converted into oxides, oxygen vacancies are formed in the amorphous titanium oxide nanostructures at the sites where the promoter nanoparticles are located. The resulting oxygen vacancy reacts with the Ti ⁴⁺ ion of the amorphous titanium oxide nanostructure, and thus the Ti ⁴⁺ ion is reduced to Ti ³⁺ ions (see Equation 2 below).

By reduction of Ti ⁴⁺ to Ti ³⁺ reason for the self-doped titanium dioxide is Ti ^3+, is the electrical conductivity of the titanium dioxide is improved along with the expansion of the light absorption wavelength band is a visible light region by the Ti ^3+, as described above Because. Thus, to be a light absorbing characteristic and electrical conductivity by maintaining Ti ³⁺ needs to be suppressed to the reoxidation of Ti ⁴⁺ Ti ^3+.

In the case of the present invention, besides the reduction reaction by proton intercalation, the reduction reaction of Ti ⁴⁺ to Ti ³⁺ through the reaction of Ti ⁴⁺ with the oxygen vacancy generated by the oxidation of the promoter nanoparticles And the reduced Ti ³⁺ ion is bonded to the oxygen vacancy of the amorphous titanium oxide nanostructure, the stabilization of Ti ³⁺ is inhibited from being re-oxidized to Ti ⁴⁺ .

(Equation 1)

Ti ⁴⁺ + H ⁺ + e ^- & gt ^; Ti ³⁺ H ⁺

(Equation 2)

Ti ^{4 +} -O-Ti ^{4 +} + Pd (0)? Ti ^{3 +} -V-Ti ^{3 +} + Pd ^{2 +} O (V:

The amorphous titanium oxide nanostructure having self-doped Ti ³⁺ ions is completed through the above-described self-doping process. In this state, the self-doped amorphous titanium oxide nanostructure is fired at 400 to 500 DEG C for 1 to 2 hours under an inert gas atmosphere such as Ar and N2 for ₁ to 2 hours to convert the amorphous titanium oxide nanostructure into crystalline titanium oxide nanostructure And the method of manufacturing the self-doped titanium dioxide light electrode is completed (S106) (S107). The final completed self-doped crystalline titanium oxide nanostructure, that is, the self-doped titanium dioxide photoelectrode, can be anatase crystalline.

On the other hand, the amorphous titanium oxide in accordance with the self-doping process proceeds before sintering step for crystallization of the nanostructure, amorphous titanium oxide surface self-doping process in the internal as well as of the nano-structures are in progress of titanium dioxide (TiO ₂₎ the energy band gap of the ( energy bandgap) is lowered, so that the light absorption rate and electrical conductivity of titanium dioxide are improved. Such an energy bandgap characteristic is supported by the experimental results described later.

The method of manufacturing the self-doped titanium dioxide photoelectrode according to an embodiment of the present invention has been described above. Hereinafter, a photoelectrochemical water treatment apparatus using a self-doped titanium dioxide photo electrode according to an embodiment of the present invention will be described.

Referring to FIG. 2, an electro-optic chemical water treatment apparatus using a self-doped titanium dioxide photoelectrode according to an embodiment of the present invention includes a photoelectric chemical water treatment tank 110.

The optoelectrochemical water treatment tank 110 provides a space where the photoelectrochemical reaction proceeds, and organic organic contaminants in the water in the water treatment tank are reduced and removed by photoelectrochemical reaction. The photoelectrochemical reaction is a reaction between a radical of hydroxide (.OH) generated by a photocatalytic mechanism of a self-doped titanium dioxide photoelectrode and an organic contaminant, a reaction between an organic contaminant and hydrogen peroxide (H ₂ O ₂ ) And the reaction with organic contaminants.

The photovoltaic chemical water treatment tank 110 is provided with a photo-anode 121 and a cathode 122 which are immersed in water and a photovoltaic electrode 121 and a voltage supply device 130 for applying power to the cathode 122 are provided. In addition, a light source (not shown) for irradiating visible light or ultraviolet light to the photolithography pole 121 is provided at one side of the optoelectrochemical water treatment bath 110.

In addition to the role of an electrode, the photocathode 121 serves as a photocatalyst for generating radicals of hydroxyl (.OH) through photocatalytic reaction during light irradiation, that is, visible light or ultraviolet light irradiation. A self-doped titanium dioxide photoelectrode manufactured by a manufacturing method according to an embodiment of the present invention is applied. That is, the photodiode 121 is a titanium dioxide photo electrode having a transition metal oxide according to the present invention and self-doped Ti ³⁺ ions. The transition metal constituting the transition metal oxide may be a platinum transition metal such as Pt or Pd or a transition metal such as Cu or Ag.

The transition metal oxide of the platinum series has a characteristic capable of temporarily accommodating electrons generated upon irradiation of light, and it is possible to prevent the electrons generated in light irradiation from being eliminated by recombination with holes. On the other hand, copper oxide (CuO) or silver oxide (AgO) can be used as the transition metal oxide if it is an objective of disinfection of pathogenic microorganisms and the like, and it is also possible to apply a platinum transition metal oxide together.

The cathode 122 is made of a conductive material carrying a catalyst capable of two-electron reduction of dissolved oxygen. Specifically, a catalyst supporting a two-electron reduction of dissolved oxygen in a conductive material such as graphite, stainless steel, and titanium can be applied to a negative electrode. As a catalyst capable of two-electron reduction of dissolved oxygen, a carbon nanotube, Graphene oxide, or carbon fiber may be used. Catalysts such as carbon nanotubes, graphene oxide, and carbon fibers accelerate the reaction between dissolved oxygen in water and hydrogen ions (H ⁺ ) and two electrons (2e ^- ) generated by the reduction reaction of the negative electrode It serves to reduce dissolved oxygen to hydrogen peroxide (H ₂ O ₂ ). The hydrogen ion (H ⁺ ) generated by the reduction reaction of the cathode can cause a safety problem, which is eliminated by the above-described two-electron reduction reaction of dissolved oxygen, (H ₂ O ₂ ) is produced, the efficiency of removing organic contaminants by photoelectrochemical reaction can be improved.

The self-doped titanium dioxide photoelectrode according to one embodiment of the present invention and the photoelectrochemical water treatment apparatus using the self-doped titanium dioxide photoelectrode have been described above. Hereinafter, the present invention will be described in more detail with reference to experimental examples.

Experimental Example 1: Production of self-doped titanium dioxide photoelectrode >

The titanium base material (size: 3 cm x 2 cm) having a purity of 99.9% was immersed in an ethylene glycol solution containing 0.1 M NH ₄ F, 5 wt% distilled water and 1 wt% lactic acid and platinum (Pt) foil of the same size After that, a voltage of 50 V versus Pt was applied for 2 hours to form a titanium oxide nanostructure on the titanium surface (Step 1).

Then, sonicated titanium oxide nanostructures were removed by sonication in distilled water containing about 10 wt% ethanol (Step 2). Then, the titanium oxide nanostructure production conditions (step 1) were applied in the same manner to produce the titanium oxide nanostructure (step 3). After washing with distilled water, the surface electrolyte was removed by baking at 200 ° C for 1 hour in an atmospheric environment (Step 4). Thereafter, Pd nanoparticles were deposited on the titanium base material on which the titanium oxide nanostructure was formed by using the sputtering process (Step 5).

NaOH was added to the 0.1 M KH ₂ PO ₄ solution to make neutral pH. The titanium base material with the Pd nanoparticles deposited was immersed in the solution, and the plate was placed at an interval of about 5 cm from the platinum foil of the same size. Then, a current of 15 mA / (Fig. 1). The oxidation of Pd nanoparticles and self-doping were induced (Step 6). The self-doped amorphous titanium oxide nanostructure was sintered at 450 ° C for 1 hour in an N ₂ -injected environment to convert it to anatase crystal structure (Step 7).

In order to compare the characteristics of the self-doped titanium dioxide photoelectrode prepared in Experimental Example 1, a self-doped titanium dioxide photoelectrode according to a comparative example was prepared. The self-doped titanium dioxide photoelectrode according to the comparative example is entirely the same as the manufacturing process of Experimental Example 1, and only the procedure of Step 6 and Step 7 is applied.

≪ Experimental Example 2: Comparison of electrochemical characteristics >

FIG. 3 shows results of X-ray photoelectron spectroscopy on the surfaces of the self-doped titanium dioxide photoelectrode according to Experimental Example 1 and the self-doped titanium dioxide photoelectrode according to the comparative example. 3, the comparison example, while the case where the Ti ³⁺ observed in titanium dioxide photo-electrode surface, in Experimental Example 1 was not observed the Ti ^3+. As a result, self-doping is localized only on the surface, whereas self-doping before crystallization is performed in Experiment 1, that is, in the case of the present invention, self-doping is mainly performed in titanium dioxide .

The energy bandgap of the self-doped titanium dioxide photoelectrode according to Experimental Example 1 and the self-doped titanium dioxide photoelectrode according to Comparative Example were measured to be 1.41 eV in Experimental Example 1, It can be seen that it is possible for the self-doped titanium dioxide photo-electrode according to Experimental Example 1 to absorb light of lower energy, which can absorb light energy at a higher rate under the same light irradiation condition .

In addition, the donor density value representing the electrical conductivity was measured using Electrochemical Impedance Spectroscopy for the self-doped titanium dioxide photoelectrode according to Experimental Example 1 and the self-doped titanium dioxide photoelectrode according to Comparative Example. As a result, 1 2.69x10 ²⁵ cm ^-3, the comparative example appeared to 1.13x10 ²⁵ cm ^-3. Accordingly, it can be seen that the self-doped titanium dioxide photoelectrode according to the present invention has an improved photoelectric conductivity as well as a light energy absorption rate as compared with the conventional method.

EXPERIMENTAL EXAMPLE 3 Performance Evaluation of Photoelectrochemical Water Treatment Device Using Self-Doped Titanium Dioxide Photoelectrode [

A 3 cm x 2 cm self-doped TiO 2 photoelectrode was immersed in 60 mL of the treated water and platinum wire was used as a counter electrode and Ag / AgCl was used as a reference electrode. The purification process of the water to be treated was observed by supplying energy in various combinations of ultraviolet rays having a wavelength of 400 nm or less, visible light having a wavelength of 400 nm or more, and an applied voltage of 1 V NHE. The number of treated cells was 10 μM of Methylene Blue or 10 ⁷ CFU / mL of E. coli.

FIG. 4 shows the results of measurement of the removal efficiency of methylene blue according to the change of the light source and voltage application conditions in Experimental Example 3. FIG. Referring to FIG. 4, it was confirmed that the removal efficiency of methylene blue, which is an organic surface material, was dramatically improved when both light and an ultraviolet irradiation condition were irradiated with light alone or applied with both light and applied voltage. This is because the photoelectrically induced electrons are induced to the counter electrode through the applied voltage and the improved electrical conductivity of the self-doped titanium dioxide photoelectron facilitates the electron transfer.

FIG. 5 shows the results of measuring the removal efficiency of E. coli according to changes in light source and voltage application conditions in Experimental Example 3. FIG. As described above, it was confirmed that supplying light and an applied voltage at the same time was more excellent in disinfection efficiency (disinfection rate of 80 to 90%) than supplying light or applied voltage alone. The results are also excellent in comparison with the result of evaluating the disinfecting ability with only ultraviolet rays (disinfection rate is around 10%) without using the photoelectrode.

FIG. 6 shows the results of measurement of the removal efficiency of methylene blue according to the change of the light source in Experimental Example 3. FIG. This result is an example in which ultraviolet rays or visible rays are supplied together under an applied voltage of 1 V NHE. In the visible light and ultraviolet light irradiation conditions, it was confirmed that the present invention, i.e., Experimental Example 1, exhibits superior organic removal performance to that of the Comparative Example, and particularly, in the visible light condition, the organic removal performance of the Examples is much higher than that of Comparative Examples.

110: photoelectric chemical water treatment tank 121:
122: cathode 130: voltage supply

Claims (13)

Forming a titanium oxide nanostructure on a titanium base material by anodizing the titanium base material into a fluorine-containing electrolyte;
Heat treating the titanium base material to convert it into an amorphous titanium oxide nanostructure;
Depositing a promoter nanoparticle on a titanium base material including an amorphous titanium oxide nanostructure;
A step of reducing the Ti ⁴⁺ of the amorphous titanium oxide nanostructure to Ti ³⁺ by applying a power source to the titanium base material deposited with the catalyst nanoparticles in the pH buffer solution; And
Ti ³⁺ is self-converting to a self-doping by firing doped amorphous titanium oxide nano-crystalline structure of titanium oxide nano-structure; made, including,
The titanium base material on which the catalyst nanoparticles are deposited is placed in a pH buffer solution and power is applied to reduce Ti ⁴⁺ of the amorphous titanium oxide nanostructure to Ti ³⁺ ,
The reduction of Ti ⁴⁺ to Ti ³⁺ by the reaction of hydrogen ions (H ⁺ ) and Ti ⁴⁺ ions in the pH buffer solution proceeds,
Characterized in that an oxygen vacancy is formed in the amorphous titanium oxide nanostructure and the reduction process of Ti ⁴⁺ to Ti ³⁺ is proceeded by reaction of oxygen vacancy with Ti ⁴⁺ ion, Of titanium dioxide photoelectrode.
delete 2. The method of claim 1, wherein the promoter nanoparticles are oxidized to form an oxygen vacancy in the amorphous titanium oxide nanostructure at the site where the promoter nanoparticles are located,
Wherein the generated oxygen vacancies react with Ti ⁴⁺ ions of the amorphous titanium oxide nanostructure to reduce Ti ⁴⁺ ions to Ti ³⁺ ions.
The method of claim 1, wherein the co-catalyst nanoparticles are transition metals.
The method of claim 1, wherein the co-catalyst nanoparticles are platinum-based transition metals and are Pt and Pd.
The method of claim 1, wherein the co-catalyst nanoparticles are one of Cu and Ag.
The method of claim 1, wherein the pH buffer solution is one of a KH ₂ PO ₄ solution and a NaHCO ₃ solution.
A photoelectric chemical water treatment tank which provides a space where the photoelectric chemical reaction proceeds;
A photocathode and a cathode provided in the photoelectrochemical water treatment tank;
A voltage supply device for applying power to the cathode and the cathode; And
And a light source for irradiating a visible ray or an ultraviolet ray to the glow pole,
^{Wherein the} photocathode is a titanium dioxide photo electrode having a transition metal oxide and self-doped Ti ³⁺ ions,
The photo-electrochemical reaction is a reaction between organic radicals (OH) generated by a photocatalytic mechanism of a self-doped titanium dioxide photoelectrode and an organic contaminant, the reaction between hydrogen peroxide (H ₂ O ₂ ) Wherein the photoelectrochemical water treatment apparatus comprises a self-doped titanium dioxide photoelectrode.
The method as claimed in claim 8, wherein the cathode is made of a conductive material on which a catalyst capable of two-electron reduction of dissolved oxygen is supported,
Hydrogen peroxide (H ₂ O ₂ ) is generated by a reaction between dissolved oxygen, a hydrogen ion (H ⁺ ) and a two electrons (2e ^- ) generated by a reduction reaction of a cathode upon application of power to the cathode. Photoelectrochemical water treatment system using titanium dioxide photoelectrode.
10. The method of claim 9, wherein the catalyst capable of two-electron reduction of dissolved oxygen is any one of carbon nanotubes, graphene oxide, and carbon fibers. Water treatment device.
9. The photoelectrochemical water treatment apparatus according to claim 8, wherein the transition metal oxide is an oxide of a platinum transition metal or a copper oxide (CuO) and a silver oxide (AgO). .
delete The self-doped titanium dioxide photoelectrode according to claim 8, wherein the photocathode is a self-doped titanium dioxide photo-electrode produced by the method of any one of claims 1 to 7. Photoelectrochemical water treatment system using.

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