JP2002038298A - Method for forming anodic oxide film on titanium for photocatalyst - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for forming a thick anodic oxide-film on titanium for a photocatalyst, which shows a highly active photocatalytic action and gives superior antimicrobial, deodorizing, and stain-proofing effects. SOLUTION: This method comprises, (1) forming an anodic oxide film on titanium by the first anodizing in an electrolytic bath including phosphoric acid, sulfuric acid, hydrogen peroxide, and added powder of titanium oxide, and (2) re-anodizing the film formed titanium in a mixed bath of ammonium hydrogenfluoride with hydrogen peroxide.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to various building materials and other equipment and materials, for example, building materials,
The present invention relates to a method for producing a titanium anodic oxide coating for photocatalyst used for cooking utensils, tableware, sanitary equipment, and other civil engineering materials such as sewer pipes.

[0002]

2. Description of the Related Art Titanium is a metal which has the highest corrosion resistance among practical metals, has a lower specific gravity than steel and the like, and has a very high specific strength algae.
It has been widely used as building materials for factory plants, medical materials and the like. In recent years, due to its high corrosion resistance, its use in building materials, including roofing materials, has been rapidly advancing.
In addition, titanium oxide (TiO 2) discovered in the 1970s
₂ ) The self-cleaning, air purifying, and sterilizing effects of the photocatalytic action of the photocatalyst have attracted attention as environmental problems have become more prominent in recent years, and research for practical use in the field of building materials has been progressing. In other words, when ultraviolet light from sunlight or lighting fixtures is applied to titanium oxide, light energy is converted into chemical energy, which exerts a photocatalytic action to decompose organic substances and is a typical allergen generated in offices and residential rooms. In addition to the decomposition and removal of certain formaldehyde, antibacterial, deodorant and antifouling effects are obtained.

Methods of forming a titanium oxide film on the surface of titanium metal include a thermal oxidation method, a chemical oxidation method, and an anodic oxidation method. Among them, an anodic oxidation method excellent in uniformity and reproducibility of the film is preferred. It is commonly used. Research on the anodization of titanium has been conducted for a long time, but most of the obtained films are thin films of 1 μm or less, and the color shows interference colors.
In practice, there is a problem in durability. On the other hand, one of the present inventors, Ito et al., Reported that phosphoric acid (H ₃ PO ₄ ) and sulfuric acid (H ₂ SO ₄ )
Anodizing titanium at a voltage higher than the voltage at which spark discharge occurs in a binary or ternary mixed bath consisting of a bath containing hydrogen peroxide (H ₂ O ₂ ) and a bath of
A hard gray thick film type anodic oxide film having a thickness of several μm or more is formed, and the main component of this film is anatase type Ti.
It has reported that it is a O ₂ ( "colorant" 61,599 (1989
, "Material technology" 10,152 (1992), etc.). However, it has been confirmed that this film does not exhibit photocatalytic activity despite having anatase-type TiO ₂ as a main component.

[0004] The titanium anodic oxidation, usually, Ti _n O
TiO or Ti ₂ O represented by _2n-1 (n is a positive integer)
It is known that lower titanium oxides such as ₃ are by-produced (T. Shibata, YCZhu: Denki Kagaku, 61, 853 (1993), etc.
Fox et al. Also found that T was formed in TiO ₂ fine particles.
It has been reported that i ³⁺ ions have a function of lowering quantum efficiency (T. Torimoto, RJFox, MAFox: J. Electroch
em. Soc., 143, 3712 (1996). This decrease in quantum efficiency means a decrease in photocatalytic activity, and it is considered that the presence of the lower order titanium oxide is a cause of inhibiting the expression of photocatalytic activity of the thick-film anodic oxide film.

Therefore, the present inventor has developed a thick-film type titanium anodic oxide film produced from a mixed bath of phosphoric acid, sulfuric acid and hydrogen peroxide with ammonium hydrogen fluoride, which easily dissolves lower titanium oxide selectively. As a result of improvement by re-anodizing in a solution of hydrogen peroxide containing hydrogen peroxide, the photocatalytic activity by visible light could be expressed as expected. A method for forming a titanium anodic oxide film for a photocatalyst by reanodization is previously filed (Japanese Patent Application No. 11-42857). That is, after a primary anodic oxide film is formed on titanium, the generated titanium film is converted into an electrolytic bath containing fluoride ions such as ammonium hydrogen fluoride, hydrofluoric acid, or ammonium fluoride, or This is a method of performing anodic oxidation by dipping in an electrolytic bath containing hydrogen peroxide.

[0006] However, in the method of the invention by re-anodizing according to the earlier application, although the photocatalytic activity by visible light is exhibited, the photocatalytic activity is still insufficient in view of industrial use.

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems and to obtain a high photocatalytic activity, that is, to provide a thick-type titanium anodic oxide film having a high photocatalytic activity regardless of ultraviolet light or visible light. An object of the present invention is to provide a method for producing a titanium anodic oxide film for a photocatalyst, which exhibits excellent antibacterial, deodorant, and antifouling effects.

[0008]

According to the present invention, a method for forming a titanium anodic oxide film for a photocatalyst comprises phosphoric acid (H ₃ PO ₄ ),
Anodizing film is formed on titanium by primary anodizing in a bath in which fine powder of titanium oxide (TiO ₂ ) is added to an electrolytic bath containing sulfuric acid (H ₂ SO ₄ ) and hydrogen peroxide (H ₂ O ₂ ). After the formation, the titanium on which the coating is formed is re-anodized in a mixed bath of ammonium hydrogen fluoride (NH ₄ HF ₂ ) and hydrogen peroxide (H ₂ O ₂ ).
The photocatalytic activity of the coating obtained by this method was evaluated. As a result, the L ^* value (brightness) of the film was greatly increased by the addition of the TiO ₂ fine powder, and the apparent decomposition rate constant k in the gas-phase photooxidative decomposition reaction of acetaldehyde was correspondingly increased.
Was also found to increase significantly. This is because the TiO ₂ fine powder suppresses the production of lower titanium oxide by-produced in the film at the time of the primary anodic oxidation, and the secondary titanium oxide in the film is also eluted and reduced at the time of the secondary anodic oxidation. It is concluded that the added fine particles adhered to the surface of the film, which together contributed to a dramatic improvement in photocatalytic activity.

The titanium oxide fine powder may be a fine powder of titanium oxide mainly composed of anatase type or a fine powder of titanium oxide mainly composed of rutile type. A coating prepared from a bath to which an anatase-type titanium oxide fine powder is added exhibits a much higher photocatalytic activity than a coating obtained from a bath to which no fine powder is added. In the case of a coating made from a bath containing rutile-type titanium oxide fine powder,
Compared to that of the anatase type, it is considerably smaller, but has a higher photocatalytic activity than the coating obtained from the bath without addition.
The titanium oxide fine powder has, for example, an average particle diameter of several n.
m to several hundred nm, more preferably,
It is 5 nm to 300 nm. The anodic oxide film obtained by primary anodic oxidation may be a thick film type anodic oxide film having a thickness of several μm or more. It is preferable that the electrolytic bath voltage for re-anodizing is lower than the electrolytic bath voltage for primary anodizing.

[0010]

EXAMPLES (1) Aiming at high activation of titanium anodic oxide film, various commercially available TiO ₂ fine powders were added to an H ₃ PO ₄ —H ₂ SO ₄ —H ₂ O ₂ bath and anodized. The electrolytic behavior at that time was examined, and the film was subjected to re-anodization, and the photocatalytic activity of the film was evaluated. Hereinafter, an experimental method and an experimental result will be described.

(2.1) Anodization The titanium material used is the first type of pure titanium plate specified by JIS-4600 according to industry. The anodic oxidation for obtaining the thick film type is performed using a titanium plate (30 ^W × 50 ^L × 0.4 ^T m
m) a After degreased by immersion in hexane n-, washed with water, dried, the H ₃ PO ₄ -1.5M of 0.3M H ₂ SO ₄ -
0.3M of H ₂ O ₂ based electrolyte bath (hereinafter, a basic bath The bath) the TiO ₂ fine powder was performed by adding 100g (the primary anodic oxidation). The electrolysis method was a method in which the voltage was raised to 200 V by DC constant current electrolysis of 3.0 Adm ^-2 and then switched to constant voltage electrolysis to maintain the above voltage (200 V).
The total electrolysis time was 30 min, the bath temperature was 303 K, the counter electrode was the same titanium plate as the test piece, and the distance between the electrodes was 5 cm.

The average particle size and specific surface area of the TiO ₂ fine powder used in this experiment, the conductivity of the electrolytic solution when 100 g of the TiO ₂ fine powder was added to the basic bath, and the gas phase photo-oxidation of the TiO ₂ fine powder to acetaldehyde Table 1 shows the apparent decomposition rate constant k / h ^-1 g ^-1 in the decomposition reaction. All TiO ₂ are manufactured by Teika Co., Ltd. and have AMT-100.
For deodorizing photocatalyst, AMT-600 for general photocatalyst, JA
-1 and JR are for general pigments, and MT-150 is mainly for cosmetics. These TiO ₂ are all surface-untreated products.

In the re-anodizing, a thick film type anodic oxide coating material is used.
This was carried out in a mixed bath of 0.03 M NH ₄ HF ₂ and 0.3 M H ₂ O _{2 in} the same manner as in the case of the primary anodization (secondary anodization). However, the final bath voltage at this time is 1
The voltage was 50 V, the total electrolysis time was 5 min, and the bath temperature was 303 K.

(2.2) Measurement A potential-time curve and a current-potential curve were measured in order to obtain knowledge on electrolysis behavior. The obtained film was subjected to film thickness measurement, color measurement, and scanning electron microscope (SE).
M) Observation, X-ray diffraction (XRD) measurement, electron spin resonance (ESR) spectrum measurement, and evaluation of photocatalytic activity were performed.

(2.2.1) Potential-Time Curve, Potential-Current Curve In order to examine changes in electrolysis behavior with the addition of TiO ₂ fine powder, a potential-time curve and a current-potential curve were measured. For the measurement, Hokuto Denko Co., Ltd. Botenshostat / Galvanostat HA-3001A was used. The current density at the time of measuring the potential-time curve was 3.0 Adm ^-2 , and the boosting rate at the time of measuring the current-potential curve was 0.5 Vsec ^-1 . The reference electrode was an Ag / AgCl electrode.

(2.2.2) Film thickness In order to examine the effect of the addition of the TiO ₂ fine powder on the film thickness, the film thickness was measured. For the measurement, a high-frequency eddy current film thickness meter CGX-B2 manufactured by CMI was used. (2.2.3) Colorimetry The color was measured to investigate the effect of anodic oxidation on the color of the film. The measurement is made by Minolta colorimeter CR-30.
The L ^* , a ^* , and b ^* colorimetric methods were used, but the coatings obtained in this experiment were all gray-gray-white achromatic coatings, so only the L ^* value (brightness index) was used. displayed.

(2.2.4) SEM Observation Surface SEM observation was performed to investigate the effect of secondary anodic oxidation on the shape of the film. The measurement was performed using a JEOL scanning electron microscope JEM-5200 at an acceleration voltage of 15 kV. (2.2.5) XRD measurement XRD measurement was performed to investigate the effect of adding TiO ₂ fine powder on the crystal system of the film. The measurement was performed by Rigaku Denki Co., Ltd.
Using a super strong X-ray diffractometer RINT2500
-Kα ray, tube voltage 40 kV-tube current 80 mA.

(2.2.6) Evaluation of photocatalytic activity The photocatalytic activity of the anodic oxide film is determined by the gas phase of acetaldehyde.
It was evaluated by a photo-oxidative decomposition reaction. The method is as follows
It is. Test piece (irradiation area 15cm^Two) To 640 ml
After sealing in a reaction vessel, reduce to 5 mmHg.
And press N _TwoAcetaldehyde standard gas diluted with gas
After introducing air up to 300 mmHg,
The system was returned to normal pressure, and it was confirmed that adsorption equilibrium was reached in this state.
After confirmation, light irradiation was started. Every 15 minutes after light irradiation
The gas in the reaction vessel is sampled and analyzed by gas chromatography.
The amount of decrease in acetaldehyde was determined. The light source is Wac
om xenon lamp with light intensity of 320-400nm
2.5mWcm in integrated value^-2It is. Gas chroma used
Tograph is a GC-9 manufactured by Shimadzu Corporation. Table 1
TiO shown_TwoThe photocatalytic ability of the fine powder was similarly evaluated,
The light amount at this time is 500 μWcm^-2Where k is powder 1.0
It is a value for g equivalent.

(2.2.7) ESR spectrum measurement In order to examine the change in the lower titanium oxide content in the coating, E
An SR spectrum measurement was performed. An electron spin resonance apparatus TE200 manufactured by JEOL Ltd. was used for the measurement, and the measurement conditions were a microwave oscillation frequency of 100 KHz and a measurement magnetic field of 230 to 430.
mT and the measurement temperature were 173K. Note that the measurement sample was obtained by carefully removing only the film components from the film.

(3) Results and Discussion (3.1) Anodization FIG. 1 shows a potential-time curve when anodizing is performed using a TiO ₂ fine powder addition bath. In the basic bath without TiO _2, gas is generated violently from the anode surface until about 100 V immediately after the start of electrolysis, and spark discharge is observed at various places on the titanium plate surface of the anode when the potential exceeds 100 V. After the start of electrolysis, the final potential is
00V was reached. In the obtained anodized film material, the metallic luster of titanium was lost, and the entire surface was covered with a uniform dark gray film. However, in the TiO ₂ -added bath, no spark discharge was visually observed because the bath was cloudy. Further, from this figure, it can be seen that the rate of potential rise is higher in a bath containing TiO _{2 of the} same crystal system having a small particle diameter. This seems to be due to the difference in the conductivity of the electrolyte (Table 1). In the basic bath, TiO ₂
The fluctuation of the potential in the high potential region is larger than that of the addition bath. This seems to suggest that spark discharge is larger and more intense in the basic bath.

[0021]

[Table 1]

FIG. 2 shows a current-potential curve. In the basic bath, a clear peak is observed around 15V. this is,
This is considered to be based on the formation of a thin nm-level insulating film. Thereafter, the current value remains stable for about 30 V, but the current value rapidly becomes unstable at around 45 V. This is considered to be based on the fact that the above-mentioned insulating film is destroyed, and after 50 V, the current value greatly changes, and around 100 V, that is, from around the potential at which spark discharge is visually observed, The intensity is further increased, and the fluctuation of the current value is increased with the increase of the potential. Among the baths to which TiO ₂ fine powder was added, JA
It can be seen that -1 shows an electrolysis behavior similar to that of the basic bath. The JR-added bath shows an electrolysis behavior similar to that of the basic bath up to about 150 V, but thereafter, the current value is more stable than that of the basic bath. AMT with small particle size
-100 and MT-150 show different electrolysis behaviors from the basic bath, and it can be seen that both of them have a smaller vertical width of the current value at or above the dielectric breakdown voltage than the others. This suggests that the magnitude of the spark discharge in these systems is small, and it can be said that the tendency is particularly remarkable in the bath to which MT-150 is added. AMT-
The 600 addition bath shows intermediate behavior between JA-1 and MT-150.

(3.2) Film Thickness Table 2 shows the film thickness of the anodic oxide film produced by the method described in 2.1.

[0024]

[Table 2]

The thickness of the film formed from the basic bath is 5.5 μm.
m, which was reduced by 0.5 μm to 5.0 μm when subjected to secondary anodization. In the bath containing TiO ₂ fine powder, the smaller the particle size, the thinner the coating. This can be seen from the SEM images described below.
The coating obtained by adding TiO ₂ having a small particle diameter had a clearly smaller pore size than the coating from a basic bath or a bath having a large particle diameter added thereto. This suggests a reduction in the size of the spark discharge when considered together with the results of the current-potential curve. The porous anodic oxide film of titanium is macroscopically grown by repeating the generation of an insulating film and the destruction of the film due to spark discharge. Therefore, the cause of the decrease in the film thickness due to the addition of TiO _{2 having} a small particle diameter can be said to be the result of suppression of spark discharge.

(3.3) Colorimetry FIG. 3 shows the measurement results of the L ^* value of the anodic oxide film. The L ^* value of the primary anodized film prepared from the basic bath was 53.9,
After the secondary anodic oxidation treatment, the value was 60.2, indicating that the whiteness was considerably increased. It is known that the film containing low-order titanium oxide as a main component is a blue-black film, and the cause of whitening is that the low-order titanium oxide in the film is preferentially eluted by the secondary anodic oxidation treatment. It can be said that. TiO ₂
Each of the anodic oxide films prepared from the bath to which the fine powder was added had a larger L ^* value than the film prepared from the basic bath. In addition, when TiO ₂ having a small particle diameter is used, the L ^* value of the primary anodic oxide film and the L ^* value of the secondary anodic oxide film are larger.
^* The difference from the value is large. This is because, during primary anodization, TiO ₂ with a smaller particle size is more likely to be taken into the inside of the film and is less likely to affect the color of the surface. Part of the film remains exposed, and it is considered that a film obtained using TiO ₂ having a large particle size has a larger L ^* value at the stage of primary anodization.
It is considered that the hiding power of O ₂ is maximized when the particle diameter is 200 to 300 nm, and that after the secondary anodic oxidation, the TiO ₂ particles taken in during the primary anodic oxidation are considered to be exposed on the surface. The reason why the film obtained from the JR-added bath has considerable whiteness is probably due to the fact that this film has the largest hiding power among the used TiO ₂ .

(3.4) SEM observation SEM photographs of the surface of the anodic oxide film are shown in FIGS. The primary anodic oxide film prepared from the basic bath has a diameter of 0.5 to
A hole of about 1.5 μm is observed. The secondary anodic oxide film has a diameter of 0.1 to
It can be seen that fine holes of about 0.3 μm are newly generated (FIG. 4). The generation of the micropores is considered to be based on the elution of the lower titanium oxide. The primary anodic oxide film from the AMT-100 added bath is greatly different from the film obtained from the basic bath, and has a smaller pore diameter and a diameter of 1 μm or less. It can also be seen that fine TiO ₂ is precipitated.
In a film obtained by subjecting this to secondary anodic oxidation, TiO ₂ particles are fixed on one surface (FIG. 5). This is based on the fact that TiO ₂ taken in by primary anodic oxidation is partially eluted by secondary anodic oxidation, but insoluble ones are exposed on the film surface. AMT-600 can be said to be similar to AMT-100.
The elution amount is much smaller than -100. This is TiO
_This is the difference between the _two properties (Fig. 6).

The primary anodic oxide coating from the JA-1 addition bath is different from AMT-100 and 600 in that it has a shape relatively similar to the coating from the basic bath except that the particles are fixed to the surface. (FIG. 7). This is presumably because the particle size of JA-1 was overwhelmingly larger than that of AMT-100 or 600, so that it was not taken into the inside of the film and was fixed to the surface. In the anodic oxide film prepared from the bath to which MT-150 was added (FIG. 8), fine particles were fixed on the entire surface of the film. Also, like the film from the AMT-100 added bath, there is a tendency that the pore size becomes smaller. The number of holes is AMT-
There is also a tendency to be less than the film from the 100 addition bath. However, it can be seen that this is also less likely to elute than AMT-100. It can be seen that the film prepared from the JR-added bath formed a film relatively similar to JA-1 having a similar particle size (FIG. 9).

(3.5) XRD Measurement FIG. 10 shows the XRD pattern of the primary anodic oxide coating material prepared from the basic bath, AMT-100 and MT-150 added baths.
Shown in Since the film prepared from the basic bath shows only the peaks of titanium and anatase, it can be said that anatase is the main component. The film prepared from the AMT-100 added bath showed only the titanium and anatase peaks similarly to the film prepared from the basic bath, but the relative intensity of the anatase peak to the titanium peak was larger than that of the basic bath. You can see that it is. This is because, as can be seen from the results of the previous SEM observation, AMT-1
It seems that 00 was taken into the film. MT-15
At 0, rutile peaks can be confirmed in addition to titanium and anatase, but the rutile peak is considered to be based on MT-150.

(3.6) Photo-Gas Oxidative Decomposition of Acetaldehyde FIG. 11 shows the results of a photo-oxidative decomposition test of a secondary anodic oxide coating material prepared from various electrolytic baths on acetaldehyde. Although not shown in the figure, the titanium plate, the titanium plate whose surface was thermally oxidized at 873K, and all the primary anodic oxide coating materials did not show photocatalytic activity. However, as can be seen from the figure, the secondary anodic oxide coating material exhibits photocatalytic activity, and the activity greatly differs depending on the type of TiO ₂ fine powder to be added. Of these, AMT-10
Anatase type T such as 0, AMT-600, JA-1
The coating prepared from the bath to which iO ₂ was added exhibited significantly greater photocatalytic activity than the coating obtained from the basic bath, with AMT-600 exhibiting the highest activity. This seems to be due to the fact that the photocatalytic ability of AMT-600 itself against acetaldehyde is remarkably higher than other TiO ₂ (Table 1). Also, rutile TiO ₂
A film prepared from a bath to which is added is considerably smaller than that of the anatase type, but shows activity.

(3.7) ESR spectrum measurement The ESR spectra of various anodic oxide films were measured, the area of the peak part of the spectrum was obtained by integration processing, and the number of radicals based on the lower titanium oxide in the film was calculated from the calculated values. (■, ●) and k / h obtained from the results in FIG.
FIG. 11 shows a plot of ^-1 (○). In addition,
It is well known that the k value is an indicator of photocatalytic activity.

The primary anodic oxide film prepared from the basic bath contains the largest amount of low order titanium oxide.
It is significantly reduced in the primary anodic oxide film prepared from the bath to which the O ₂ fine powder is added. Therefore, it can be said that TiO ₂ has an effect of suppressing the by-product of lower titanium oxide in the film. This is considered to be mainly attributable to the fact that the addition of TiO ₂ has a function of reducing the spark discharge, as can be seen from the results of the potential-time curve and the current-potential curve. In addition, this leads to suppression of local heat generation at the time of discharge, which is also considered to be involved in suppression of low-order titanium oxide by-product. When these films are subjected to secondary anodic oxidation, the content of the low order titanium oxide in each film is further reduced. On the other hand, k is AMT-6
00 addition bath> MT-150 addition bath> coating prepared from basic bath. AMT-600 and MT-150
Although the content of low order titanium oxide is not much different,
The value of k is very different, but this is because AMT-60
0 can be attributed to its own photocatalytic activity (Table 1).
However, as described in 3.6, in the stage of primary anodization, even if a bath containing AMT-600 was used, no photocatalytic activity was exhibited, and the secondary anodizing treatment was required for the development of photocatalytic activity. It is necessary to carry out.

[0033]

According to the method for producing a titanium anodic oxide film for photocatalyst of the present invention, a primary anode is applied to titanium in a bath in which fine powder of titanium oxide is added to an electrolytic bath containing phosphoric acid, sulfuric acid and hydrogen peroxide. After anodized film is formed by oxidation, it is re-anodized in a mixed bath of ammonium hydrogen fluoride and hydrogen peroxide. In addition, a thick-film type titanium anodic oxide film for photocatalyst which can provide an antifouling effect can be produced.

[Brief description of the drawings]

FIG. 1 is a graph showing a potential-time curve in a basic bath and various titanium oxide added baths.

FIG. 2 is a graph showing current-potential curves in a basic bath and various titanium oxide added baths.

FIG. 3 is a graph showing L ^* values of an anodized film.

FIG. 4 is an SEM photograph of an anodic oxide film produced from a basic bath.

FIG. 5 is an SEM photograph of an anodic oxide film produced from an AMT-100 addition bath.

FIG. 6 is an SEM photograph of an anodic oxide film produced from an AMT-600 addition bath.

FIG. 7 shows S of the anodic oxide film produced from the JA-1 addition bath.
It is an EM photograph.

FIG. 8 is an SEM photograph of an anodic oxide film produced from an MT-150 addition bath.

FIG. 9 is an SEM of an anodic oxide film produced from a JR-added bath.
It is a photograph.

FIG. 10 is a graph showing an XRD pattern of an anodized film.

FIG. 11 is a graph showing a change in the amount of acetaldehyde due to light irradiation on the re-anodized oxide film.

FIG. 12 is a graph of the number of radicals in various anodic oxide films and the k value.

Claims (6)

[Claims] An anodic oxide film is formed by primary anodic oxidation on titanium in a bath in which fine powder of titanium oxide is added to an electrolytic bath containing phosphoric acid, sulfuric acid, and hydrogen peroxide.
A method for forming a titanium anodic oxide coating for photocatalyst, wherein the titanium having the coating formed thereon is re-anodized in a mixed bath of ammonium hydrogen peroxide and hydrogen peroxide. 2. The method for producing a titanium anodic oxide film for a photocatalyst according to claim 1, wherein the titanium oxide fine powder is a fine powder of titanium oxide mainly composed of anatase type. 3. The method for producing a titanium anodic oxide coating for a photocatalyst according to claim 1, wherein the titanium oxide fine powder is a rutile-type titanium oxide fine powder. 4. The method according to claim 1, wherein the titanium oxide fine powder has an average particle diameter of several nm to several hundreds of nm. 5. The titanium anodic oxide film for photocatalyst according to claim 1, wherein the anodic oxide film obtained by the primary anodic oxidation is a thick film type anodic oxide film having a thickness of several μm or more. Generation method. 6. The method for producing a titanium anodic oxide coating for a photocatalyst according to claim 1, wherein a final voltage of the electrolytic bath for re-anodizing is lower than a final voltage of the electrolytic bath for primary anodic oxidation.