JPS6328895A - Oxidation-reduction method and diaphragm type photoelectrochemical device - Google Patents

Abstract

PURPOSE:To carry out oxidation and reduction at a low cost with light as an energy source without requiring a power source by projecting light on a semiconductor in a diaphragm which divides an electrolytic soln. into two parts so as to separately cause oxidation and reduction reactions in the two parts of the electrolytic soln. CONSTITUTION:An electrolytic cell 4 is partitioned into an oxidation cell 4a and a reduction cell 4b with a diaphragm 2 contg. a semiconductor 1 made of an N-type semiconductor 1n and an electrolytic soln. 3 in the cell 4 is divided into two parts. Light from a light source 9 is projected on the contact interface 5 between the semiconductor 1 and the electrolytic soln. 3 to produce excited electrons e<-> and positive holes h<+> by light excitation. The positive holes h<+> cause an oxidation reaction with the electrolytic soln. 3a in the oxidation cell 4a. The excited electrons e<-> transfer to the rear side of the diaphragm 2 along an electric potential gradient in the diaphragm 2 and cause a reduction reaction with the electrolytic soln. 3b in the reduction cell 4b. The diaphragm type photoelectrochemical device requires no electric energy and can be utilized for producing gaseous hydrogen at a low cost at a remote place.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a wet redox method that converts and utilizes light energy into chemical energy, and a technique for applying this redox method to various uses.

[Conventional technology]

Oxidation and reduction reactions in electrolytes have been conventionally carried out in the fields of plating, metal refining, surface treatment, hydrogen production, and electrolytic synthesis of various compounds.

By the way, in order to cause an oxidation/reduction reaction in an electrolytic solution, generally, an anode plate is placed at one end of the electrolytic cell, a cathode plate is placed at the other end of the electrolytic cell, and a voltage is applied between the two plates. By doing so, an oxidation reaction is caused near the anode plate, and a reduction reaction is caused near the cathode plate.

[Problem that the invention attempts to solve]

However, as mentioned above, a large amount of electrical energy is required to cause the oxidation/reduction reaction, and the running costs and equipment costs are accordingly high.

The present invention has been made in view of the above-mentioned circumstances, and its first purpose is to use solar energy and other light of all wavelengths depending on the purpose as an energy source to generate electricity as in the past. The purpose is to provide an oxidation-reduction method that does not require energy and can reduce running costs and equipment costs.The second purpose is to apply the above-mentioned oxidation-reduction method to plating, hydrogen gas, etc. The object of the present invention is to provide a diaphragm-type photoelectrochemical device that can be used in various fields such as production of substances, quantitative determination of substances, batteries, photosynthesis, waste liquid treatment, sterilization, and medical instruments.

[Means for solving problems]

That is, the characteristic configuration of the redox method according to the first invention is that an electrolytic solution is separated by a diaphragm having a semiconductor, and light is irradiated to the contact interface between the semiconductor and the electrolytic solution, so that the electrolytic solution in one of the electrolytic solutions is removed. The purpose of this method is to cause an oxidation reaction and a reduction reaction in the other electrolyte, and its functions and effects are as follows.

[For production]

For example, when an N-type semiconductor is used as the diaphragm, the difference between the Fermi level of the semiconductor and the oxidation-reduction potential of the electrolyte creates a 5-chottky barrier at the contact interface between the semiconductor and the electrolyte, which causes a 5-chottky barrier to flow toward the inside of the diaphragm. This creates a potential gradient, or band bending, and a space charge layer is formed, which maintains an energetic balance. When the N-type semiconductor in this state is irradiated with light, it is photoexcited and generates excited electrons (e-) in the conduction band and holes (h) in the valence band. These excited electrons move into the diaphragm and further to the back side due to the potential gradient of the space charge layer, causing a reduction reaction with the solution on the back side. At the same time, the holes generated on the light-irradiated surface cause an oxidation reaction with the solution on the light-irradiated side.

Further, when a P-type semiconductor is used as the diaphragm, the holes move into the diaphragm and further to the back side due to the potential gradient of the space charge layer, and finally reach the back surface of the diaphragm. The holes that reach the back surface cause an oxidation reaction with the solution on the back side of the diaphragm. At the same time, the excited electrons generated on the light-irradiated surface cause a reduction reaction with the solution on the light-irradiated side.

〔Effect of the invention〕

As a result, by simply irradiating the semiconductor of the diaphragm with light, oxidation and reduction reactions can occur in both electrolytes, eliminating the need for electrical energy (running costs and equipment costs). etc., can be done at low cost.

[Means for solving problems]

Further, the characteristic configuration of the diaphragm type electrochemical device according to the second invention is that two electrolytic cells are formed which are separated by a diaphragm having a semiconductor, and a light irradiation part is formed on the semiconductor of the diaphragm. The functions and effects are as follows.

[Function] When the light irradiation part of the semiconductor is irradiated with light, an oxidation reaction occurs in the negative electrolytic cell and a reduction reaction occurs in the other electrolytic cell, according to the principle of the oxidation/reduction method explained above. I will do it.

〔Effect of the invention〕

As a result, oxidation and reduction reactions can occur simultaneously in both electrolytic cells using only light energy without the need for electrical energy, so it can be used as an element that uses light energy for plating, hydrogen gas production, and material processing. quantitative, battery,
It can now be applied to various fields such as photosynthesis, waste liquid treatment, sterilization, and medical equipment. In particular, this device is useful in the above-mentioned fields, such as in mountainous areas where electricity is not available, on the ocean, or in outer space. Furthermore, since this device can be constructed only from a diaphragm containing a semiconductor and an electrolytic cell containing an electrolytic solution, it has the advantage that it can be manufactured with a simple structure with fewer parts.

[Example 1] Embodiments of the present invention will be described below based on the drawings.

As shown in Figure 1, an electrolytic cell (
4) has a thin diaphragm (2) composed of an N-type semiconductor in the center.
) is arranged, and the electrolyte (3) supplied into the electrolytic cell (4)
) are completely separated by a diaphragm (2). Examples of the N-type semiconductor include Ti0z, ZrO□, ZnO, and WO.
3. FezO=, Cd555nOz, GaAs.

Although semiconductors such as GaP can be used, titanium oxide (TiO□) semiconductors are particularly preferred. The electrolytic cell (
A light source section (9) is arranged outside the semiconductor (1).
The light irradiation part (5) formed at the contact interface with the electrolytic solution (3a) in one of the electrolytic cells (4a) is irradiated. As described above, this light irradiation causes an oxidation reaction to occur in the electrolyte (3a) on the light-irradiated side, and a reduction reaction to occur in the electrolyte (3b) in the dark area on the back side, which is not irradiated with light. Oxidation tank (4a) where this oxidation reaction occurs
As the electrolytic solution supplied within the chamber, for example, water, an aqueous sodium hydroxide solution, alcohol, an aqueous sodium perchlorate solution, etc. may be used. In particular, in order to promote the oxidation reaction, a substance with strong electron donating property may be used. It is preferable to mix it.

On the other hand, as the electrolytic solution (3b) supplied into the reduction tank (4b) where the reduction reaction occurs, it is preferable to use a sulfuric acid aqueous solution, water, etc. In particular, a substance with strong electron acceptability to promote the reduction reaction. It is preferable to mix.

As shown in FIG. 2, the oxidation tank (4a) and the reduction tank (4a)
b) can be communicated by a salt bridge (6) filled with a concentrated solution such as potassium chloride or potassium sulphate.

That is, when this salt bridge (6) is not provided, the electrolyte (3a) separated by the diaphragm (2), (
In 3b), even if oxidation and reduction reactions occur, only anions decrease on the light irradiation side, and only cations decrease on the back side of the dark area, so both electrolytes (3a)
, (3b), the ions that serve as the counter charge cannot exist stably, resulting in a reverse reaction, and the upper reaction is apparently suppressed, but when the salt bridge (6) is used,
On the light irradiation side, the cations in the solution go to the salt bridge (6), and the salt bridge (
The anion of the salt constituting 6) moves into the solution on the light irradiation side. Conversely, on the back side of the dark area, the anions in the solution are moved to the salt bridge (6), and the cations of the constituent salts of the salt bridge (6) are moved into the solution on the back side of the dark area, and both electrolytes are (3
a) and (3b) are kept electrically neutral, allowing the reaction to proceed smoothly. In other words, by using the salt bridge (6), it becomes possible to irreversibly promote oxidation and reduction reactions.

Note that the thickness of the diaphragm (2) can be changed as appropriate, and both electrolytes (3a) and (3b) are placed in the tank (4a) in succession.
).

(4b), various types (4a), (4b)
You can also stir it inside. Further, as the light source section (9), an optical fiber may be used to irradiate light into the interior, or an artificial light source may be used. Furthermore, Figure 3 (a) and (b)
As shown in FIG.
5) may be provided so that the electrolytes (3a) and (3b) are completely separated by the diaphragm (2) and the ion permeable membrane (25). The one shown in Figure 3 (a) has an ion permeable membrane (25) placed at the bottom, and the one shown in Figure 3 (b) has an ion permeable membrane (25) placed at the top. be.

[Example 2] Figure 4 shows the diaphragm (2) made of Cu2O, GaAs, GaP.
, tnP, or other P-type semiconductor (1P). In this case, contrary to the first embodiment, the electrolytic cell on the light irradiation side becomes the reduction tank (4b), and the electrolytic cell on the back side of the dark part becomes the oxidizing tank (4a).

That is, when a P-type semiconductor (1P) and a solution first come into contact,
Based on the difference between the Fermi level of the P-type semiconductor (1P) and the redox potential of the solution, 5 shots are taken at the surface of the P-type semiconductor (1P).
tky barrier, a potential gradient or band bending toward the inside of the semiconductor (1P), a space charge layer is formed, and energy balance is maintained. When the P-type semiconductor (1P) in this state is irradiated with light, it is photoexcited and generates excited electrons (e-) in the conduction band and holes (h) in the valence band.

These holes (h+) move into the interior of the semiconductor (1P) and further to the back side due to the potential gradient of the space charge layer, and cause an oxidation reaction when they come into contact with the solution on the back side of the dark area. At the same time, the excited electrons (e-) generated on the light-irradiated surface cause a reduction reaction when they come into contact with the solution on the light-irradiated side.

[Example 3] FIG. 5 shows a diaphragm (2) constructed by laminating an N-type semiconductor (1n) and a conductive metal (7).

For example, titanium or platinum can be used as the metal, although it is not limited thereto. In this example, the example L2
Compared to this, electron transfer to the back surface becomes easier, and accordingly, the recombination consumption of the holes generated by light irradiation and the excited electrons is suppressed, and the reaction efficiency is further promoted.

[Example 4] As shown in FIG. 6, the diaphragm (2) was made of a P-type semiconductor (1P
) and a conductive metal (7) may be laminated, and the same effect as in Example 3 can be achieved in this case as well.

[Example 5] FIG. 7 shows that the diaphragm (2) is constructed by laminating an N-type semiconductor (In) and a P-type semiconductor film (1P).
) is placed on the light irradiation surface and the P-type semiconductor (1P) is placed on the back side of the dark area, and has the following advantages.

In other words, when the solution comes into contact with the P-type semiconductor (1P) on the back surface of the diaphragm (2), P
Due to the difference between the Fermi level of the P-type semiconductor (1P) and the redox potential of the solution, a hand bends on the surface of the P-type semiconductor (1P) and a space charge layer is formed, which maintains an energetic balance. .

Next, when light is irradiated to the P-type semiconductor (1P) through the N-type semiconductor (In) film and film on the light-irradiated surface, excited electrons (e-) are added to the conduction band and the valence band is hole (ho)
) occurs. This excited electron (e-) moves to the P-type semiconductor (1P) surface due to the potential gradient of the space charge layer,
Conversely, the holes (ho) will move to the surface of the N-type semiconductor (1n). Along with this, charge separation of electron (e-) and hole (ho) pairs generated by light irradiation is performed, and both electrolytes (3a) are separated.

The efficiency of the oxidation and reduction reactions in (3b) is further enhanced.

In addition, as shown in FIG. 8, light irradiation is applied to a P-type semiconductor (1P
) may be used as a side. In other words, when the P-type semiconductor (1P) and N-type semiconductor (1n) on both sides of the device come into contact with the solution, a space charge layer is formed on the surface of each semiconductor (1P) and (In). When light passes through the P-type semiconductor (1P) film and film on the light-irradiated surface and irradiates the N-type semiconductor (1n), it is photoexcited and generates excited electrons (e-) in the conduction band and positive electrons in the valence band. Hole (
ho). The holes (ho) move to the N-type semiconductor (In) surface due to the potential gradient of the space charge layer, and the excited electrons (e-) move to the P-type semiconductor (1P) surface, on the contrary. Along with this, electrons (e) generated by light irradiation
-) and hole (ho) pairs are promoted, and the efficiency of oxidation and reduction reactions in both electrolytes (3a) and (3b) is further enhanced.

[Example 6] A substance that promotes oxidation is attached to the surface of the semiconductor (1) that contacts the oxidation tank (4a), or a substance that promotes reduction is attached to the surface of the semiconductor (1) that contacts the reduction tank (4b). or both substances may be used together. Here, as a substance that promotes oxidation, for example, a dye etc. can be used,
It will have the following advantages. In other words, an N-type semiconductor (
In) When a dye is attached to the surface, first,
When irradiated with light, as shown in Figure 9 (a), an N-type half-4
A dye attached to the surface of the body (in) absorbs light and becomes excited. Next, electron injection from this excited dye into the conduction band of the N-type semiconductor (1n) occurs. The injected electrons (e-) move inward due to the potential gradient of the space charge layer and further reach the back surface of the dark area. The dye that has lost electrons receives electrons from the substance in the solution and returns to its original state.

When the dye is attached to the surface of the N-type semiconductor (1n) in this way, it becomes possible to expand the light absorption region of the N-type semiconductor (1n) to the light absorption region of the dye, which is separated by the diaphragm (2). It becomes possible to further promote the oxidation/reduction reactions in both the electrolytic cells (4a) and (4b).

Further, even when a dye is attached to the surface of the P-type semiconductor (1P), the same effect as in the case of the N-type semiconductor (1n) can be obtained, as shown in FIG. 9(b). That is, the dye (Dye) attached to the surface of the P-type semiconductor (1P) absorbs light and becomes excited. Electrons are transferred from the valence band of the P-type semiconductor (1P) to the vacant molecular orbitals of the excited dye, and holes (ho) are injected into the valence band. Further, the dye (Dye) that has received electrons gives electrons to the substance in the solution and returns to its original state. When the dye is attached to the surface of the P-type semiconductor (1P) in this way, it becomes possible to expand the light absorption region of the P-type semiconductor (1P) to the light absorption region of the dye, and the light absorption region of the P-type semiconductor (1P) can be separated by the diaphragm-type photoelectric element. Both electrolytes (3a), (
It becomes possible to further promote the oxidation/reduction reaction in step 3b).

[Example 7] Next, a case where the diaphragm type photoelectrochemical device of the present invention is applied to metal plating will be described.

First, the structure of this plating apparatus will be briefly described. The structure shown in FIGS. 10 to 14 can be used. (4) in the figure is an electrolytic cell divided into left and right halves,
One oxidation tank (4a) on the side irradiated with light is made of a transparent material, and the other reduction tank (4b) is made of an opaque material. A diaphragm (2) is provided between the two tanks (4a) and (4b) via rubber gaskets (13) and (13), respectively, and a holding part (
22) into the recess (23) of the holding frame (11) and tighten both holding parts (22) and (22) with screws from both sides to make both tanks (4a) and (4b) watertight. is joined to. In addition, this holding frame (1) is attached to a base (12
), and the oxidation tank (4a) and reduction tank (4b) are connected by a salt bridge (6) made of potassium sulfate or the like. Note that (10) is a rubber gasket.

(i) In the case of platinum plating The form of the diaphragm (2) and the composition of the electrolyte can be changed as appropriate as described above, but in this example, titanium is plated on the back side of the titanium oxide shown in FIG. The oxidation tank (4a) is used as a diaphragm (2) with a thin film formed on it.
1 mol/l Na011 as electrolyte (3a)
A chloroplatinic acid solution was used as the electrolyte (3b) in the reduction tank (4b). In addition, this chloroplatinic acid solution is
A solution of 0 g of chloroplatinic acid (HzPtCIJl) dissolved in 3 ml of acetic acid and diluted to about 6 ffII! with double-distilled water was used, and the pH was adjusted to 5 to 6 with sodium carbonate (NazCOz). The graph in Figure 15 shows the change over time in the amount of platinum deposited on the titanium surface on the back side of the dark area when the device is irradiated with light using an IKH xenon lamp. As shown in the figure, there is a proportional relationship between the light irradiation time and the amount of platinum precipitated, and this platinum precipitation is caused by a reduction reaction on the back surface of the dark area based on the principle of the diaphragm photoelectrochemical device mentioned above. It can be seen that the reaction accompanying this light irradiation can be expressed by the following reaction formula (11 to (3)).

TiO2+ 4h! /=4h"+4e-(1140H
−+4h”→ 0□+2H20−(21H2PtC1,
+ (Ti) + 4 e-→Pt(Ti) + 2
HCI + 4 C1--(3) (ii) For copper plating, use 1 mol/1 NaOH solution on the light irradiation side and 1 mol/β sulfuric acid solution on the back side of the dark area as the base solution 0,0
05 mol of copper sulfate (CuSOt) solution was added, and both electrolytes were connected through a salt bridge of 2SO. This device has lK
The 16th graph shows the dependence of the amount of copper deposited on the back side of the dark area on the light irradiation time when irradiated with a H xenon lamp.
This is a graph of the figure. Looking at this graph, it can be seen that the amount of copper precipitation increases with the light irradiation time. Further, the reaction during this light irradiation can be expressed by the following reaction formulas (4) to (6).

TiO2+ 2h sea=2h"+ 2e--(4120
H-+2h" →%0□+H20-(51CuSO4+
(Ti) + 2e- -*Cu(Ti)+SO4"-- (61 (iii) For lead plating, add 1 mol/ii of NaOH on the light irradiation side and 0 on the back side.
．． Pb at concentrations of 1 mol/f and 0.3 mol/12
(NOz)z was added, and both electrolytes were connected through a salt bridge of 2SO and potassium nitrate (KNO3). This device has
The graph in FIG. 17 shows the dependence of the amount of lead deposited on the titanium surface on the back side of the dark area on the irradiation time when light was irradiated with a 500 W xenon lamp. Looking at this graph,
It can be seen that the amount of lead precipitation is proportional to the light irradiation time. Also, as the concentration of Pb(NO3)z increases,
It can also be seen that the amount of lead precipitation is increasing. From this, in the electrolyte separated by the diaphragm, (7) to (9)
It is possible that a reaction like this is occurring.

Ti0z + 2hv = 2h" + 2e-(7)
20) de + 2h″ = V20□+)1.0
−(81Pb (NO3)! + (Ti) +
2 e-→Pb(Ti) + 2 NO3- (91 As described above, plating using the diaphragm photoelectrochemical device according to the present invention and conventional electroplating, chemical plating, hot-dip plating,
When compared with thermal spray plating, vapor deposition plating, vapor phase plating, etc., the plating apparatus of the present invention has the following advantages.

In other words, since the plating apparatus of the present invention mainly uses natural light as the energy source for plating, the plating process cost is low (and the problem of harmful gases generated during plating work is solved, so waste treatment equipment is unnecessary). ,
This has the advantage of lower equipment costs. In addition, since it is possible to use energy that is unlikely to run out, such as sunlight, it is possible to operate the device semi-permanently, and in this method, light energy can be directly converted into chemical energy. Since plating is performed during the process of converting light energy into light, it is possible to efficiently utilize light energy. Further, in methods such as electroplating that utilize electrode reactions, two electrodes are required, but in the present invention, plating can be performed using only one diaphragm. It is also possible to adjust the thickness of the plating by changing the amount of light.

[Example 8] Next, a case will be described in which the diaphragm type photoelectrochemical device of the present invention is applied to the production of hydrogen gas.

As shown in FIG. 18, in addition to the apparatus shown in Example 7, the apparatus includes a supply pipe (14) that supplies nitrogen gas to the reduction tank (4b), and replaces this nitrogen gas. Gas pile 7 measures the amount of hydrogen gas flowing out.
(15) are connected. In addition, (18) in the figure
is the nitrogen gas outlet pipe, (19) is the sample gas outlet, (1
6) is a stirrer, and (17) is a drive unit that drives the stirrer (16).

As the diaphragm (2), the N-type semiconductor (1n) on the light irradiated surface was made of TiOz, and the metal on the back surface of the dark part was made of Ti, and the test was carried out by the method described in detail below.

First, in the electrolytic cell (4a) of the light irradiation part, l mol/
Add 1 of NaOH. In the electrolytic cell (4b) on the back side of the dark area, 1 mol/E of H2SO4 or pH2, o
and 4.1, add 8 rounds of acidic solution, and add both electrolytes (3
a) and (3b) were connected at the salt bridge (6) of SO. When this device was irradiated with light using an IKW xenon lamp (9), the amount of hydrogen generated on the back side of the dark area was investigated. Note that the above pH 2.0 solution is 0.2 mol/β potassium chloride (KCI) in 100 ml.
/ 1 salt? , 21.2 ml of (HCI) and 27.8 ml of water
It was made by adding 8ml.

In addition, a solution with a pH of 4.1 contains 0.1 mol/l of acetic acid (
CH3COOH) 200ml, 0.1mol/1
of sodium acetate (CHzcOONa) 50 m j!
It was made by adding.

The irradiation time dependence of the amount of hydrogen generated in each solution is shown as follows:
The graph will look like the one in Figure 19. This graph shows that there is a proportional relationship between the amount of hydrogen generated, the hydrogen ion concentration, and the light irradiation time.

In addition, by adding platinum as a reduction catalyst to the titanium surface on the back side of the dark area, and by adding EDTA, a substance that promotes oxidation, to the electrolyte on the light irradiation side, the amount of hydrogen generated can be changed. When I investigated whether it changed, I found the graph shown in Figure 20. This graph shows that the amount of hydrogen generated increases by supporting platinum or adding EDTA to the liquid on the light irradiation side.

In other words, in this way, an acidic solution is placed in the electrolytic tank (4b) on the back side of the dark area separated by the diaphragm type photoelectrochemical element, and an alkaline solution etc. is placed in the electrolytic tank (4a) on the light irradiated side, and both electrolytes are mixed. By connecting with the salt bridge (6) and irradiating with light,
Hydrogen production is possible.

Furthermore, it is possible to modify the back side of the dark area with platinum, etc., which is a substance that promotes reduction, and to add E into the electrolyte (3a) on the front side.
By adding substances that promote oxidation such as DTA,
The amount of hydrogen generated can be increased.

The hydrogen production method according to the present invention and the conventional water cooling air reforming method,
Comparing the hydrogen production method using the partial oxidation method, the present invention can utilize sunlight that is unlikely to be depleted, and in the process of converting light energy into chemical energy, Hydrogen, which is easier to store than electricity or heat, is generated using a simple energy conversion element, and theoretically has the advantage of improved energy efficiency.

[Example 9] Next, an example in which the diaphragm type photoelectrochemical device of the present invention is applied to the quantitative determination of a substance will be described.

As the diaphragm (2), the light irradiation surface is made of Ti, which is an N-type semiconductor.
An experimental example in which p-benzoquinone was quantified using titanium metal with platinum supported on the back side of the dark area will be described in detail below.

Put 1 mol/12 NaOH on the light irradiation side and 1 mol/12 solution containing p-benzoquinone in NaCIOa on the back side of the dark part, and measure the electrode potential of the metal surface on the back side when light irradiated with an IKH xenon lamp. It was measured.

As a result, it was found that stagnation first occurs at the potential at which p-benzoquinone reduction occurs, and then shifts to the hydrogen generation potential.

Next, it was found that increasing the concentration of p-benzoquinone (transition time) increases the time during which the potential stagnates (transition time). Plotting the relationship between the concentration of p-benzoquinone and the transition time on a graph shows that As shown in Figure 21, it was found that there was a proportional relationship between the two.In other words, it became clear that p-benzoquinone could be quantified by measuring the transition time.

It has been found that chemical substances can be quantified by measuring the electrode potential of the diaphragm photoelectrochemical device in this manner.

Therefore, this element can be applied as a sensor such as a gas sensor, humidity sensor, ion sensor, biosensor, etc. In other words, in the above experimental example, the light irradiation surface is N
It is stated that p-benzoquinone can be quantified by measuring the transition time of the stagnation potential on the back surface of a diaphragm type photoelectrochemical device consisting of TiO2, which is a type semiconductor, and Pt/Ti on the back surface. Quantification of substances other than benzoquinone is possible as long as they have a lower reduction potential than hydrogen.

Furthermore, by detecting electromotive force and color changes, the sensor of the present invention is simple and versatile as a conventional gas, humidity, ion, or biosensor. It becomes sexually rich.

[Example 10] Next, an example in which the diaphragm type photoelectrochemical device of the present invention is applied to a battery will be described.

As the apparatus, the one shown in FIG. 22 can be used.

In the figure, (8) is a conductive material connecting both platinum electrodes (20) and (20), and (21) is a voltmeter. Further, as an example of the diaphragm (2), a diaphragm-type photoelectrochemical device is constructed in which the light irradiation surface is made of Ti0z, which is an N-type semiconductor, and the back surface of the dark part is made of Ti or platinum supported on Ti. Electromotive force was measured using the element.

1 mol/
The electromotive force after 18.3 minutes was investigated by adding sulfuric acid (1) and changing the type of solution added to the electrolytic cell (4a) on the light irradiation side. As the solution (3a) on the light irradiation side, )1zs
O4,, NaOH, CH=0)1. Four different solutions of Nac104 were used. The concentration of each solution is all 1.
mol/i! It is. The results are summarized in Table 1.
become that way. Looking at Table 1, the back side is Ti and T.
In both cases where platinum is supported on i, the solution on the light irradiation side is 1 mol/l of NaOH, and the solution on the back side of the dark area is 1 mol/l! It was found that H2SO generates the highest electromotive force. In other words, in this diaphragm photoelectrochemical device where the light irradiation side is an N-type semiconductor, a substance that is easily oxidized such as NaOH is placed on the light irradiation side, and a substance that is easily reduced such as sulfuric acid is placed in the electrolytic cell on the back side of the dark area. A large electromotive force can be obtained by adding a substance that promotes oxidation to the surface or a substance that promotes reduction, such as platinum, to the back surface.

Table 1 Electromotive voltage (mV) in each solution From the above results, when comparing conventional primary batteries, secondary batteries, fuel cells, and solar cells with the battery according to the present invention, there are the following advantages.

In other words, secondary batteries and secondary batteries cannot generate electricity due to the active material inside the battery being depleted or depleted, and fuel cells cannot be used to generate electricity chemically or electrically from outside. Electricity cannot be extracted unless synthesized fuel and oxygen are supplied. In the three types of batteries described above, two electrodes are also required. However, the battery of the present invention converts light energy such as sunlight into electricity, and is more economically efficient than conventional batteries that use chemical substances synthesized through secondary processing. It is. Furthermore, the battery of the present invention does not require two electrodes,
It is a battery that can generate electricity just by using one diaphragm.

Among the conventional battery types, dry photovoltaic cells called solar cells utilize the same principle as the battery in the present invention in that they extract electricity by using light energy such as sunlight. However, in dry photovoltaic cells,
Requires extremely pure single crystal semiconductor. Also P
.

Since the N junction portion also needs to be made to a certain thickness, the cost is extremely high. On the other hand, 1 in the present invention
In a wet photovoltaic cell using a single diaphragm, it is not necessary to use a single crystal semiconductor of high purity, and a polycrystalline semiconductor prepared by firing may be used. Furthermore, simply adding a semiconductor to the solution creates an energy structure similar to the P, N junction in a solar cell at the semiconductor solution interface, resulting in a very low cost.

[Example 11] Next, an example in which the diaphragm type photoelectrochemical device of the present invention is applied to photosynthesis will be described. As the apparatus, the one shown in FIG. 23 can be used. The diaphragm (2) was made of N-type semiconductor Tie on the front side and Ti on the back side, and an experiment was conducted to synthesize formaldehyde from methanol using the method described in detail below. .

First, 0.1 mol/l is placed in the electrolytic tank (4a) on the light irradiation side.
CH, OH of 1.
50a+ each of 0mol/1 Hz S'04
Pour both electrolytes (3a) and (3b) into KzS.
O4 salt! (6) I contacted you. Soow to this device
When the dependence of the CM and OR concentrations on the irradiation time when irradiated with light using a xenon lamp is investigated, the graph shown in FIG. 24 is obtained. In addition, 1. Omo
1/l of NaOH into the electrolytic cell (4b) on the back side.
0 mol/n C1130H was added in an amount of 50 m2 each, and both electrolytes (3a) and (3b) were connected through a KtSOa salt bridge (6). When this device was irradiated with light using a 500 W xenon lamp (9), the dependence of the CH30H concentration on the irradiation time was investigated, as shown in FIG. 25. Further, when the solution after the reaction was examined by steam gas chromatography, the graph shown in FIG. 26 was obtained, and it was found that formaldehyde was produced based on the retention time.

It is thought that the reaction when methanol is introduced into the electrolytic solution (3a) on the light irradiation side proceeds as shown in aω~(2).

TiO2+hv-+ h"+e-(101CH, O
H+h'-・C)120H+)l"-CII
J・CHzOH= HCHO+ %Hz Q
The reaction when methanol is put into the electrolyte (3b) on the back side of 21 is thought to proceed as shown in α31-CIT).

TiO2+h sea h"10e--(13) H"10□+e-=HO□ □a-season HOz+H"+e
--= 2HO・□α9・0)1 +C
)IsOH= ・CHzOH+HzO' 06), CH
20H+ →HCHO+ %)lz Q
7) It was thus found that formaldehyde was generated from methanol through the oxidation and reduction reactions of the diaphragm photoelectrochemical device.

As mentioned above, when the photosynthesis of the present invention is compared with, for example, conventional electrolytic synthesis, the method of the present invention has the following advantages.

In conventional synthesis methods such as electrolysis, it is not possible to make the electrolyte solutions in the anode cell and the cathode cell completely different, but rather, the redox reaction is carried out within one type of electrolyte cell solution.

Therefore, the reaction products at each electrode often undergo a reverse reaction, producing by-products and reducing the reaction efficiency of the target substance. Furthermore, after the reaction is complete, multiple steps and technical innovations are required to separate the products at both poles. In contrast, in the present invention, redox reactions can be carried out separately in completely different solutions by using two diaphragm-type photoelectrochemical devices, thereby suppressing reverse reactions.
The reaction efficiency of the target substance can be increased, and product separation in the re-reactor can be performed at the same time. moreover,
Selectivity can be imparted to the reaction by changing the intensity of light irradiated onto the semiconductor surface and the type of semiconductor. As described above, the present invention has the advantage that synthesis can be performed simply by light irradiation, and there is no troublesome operation.

[Example 12] Next, an example in which the diaphragm type photoelectrochemical device of the present invention is applied to waste liquid treatment will be described. That is, by utilizing the oxidation and reduction reactions in the electrolyte separated by the above element, harmful substances such as CN-, Cr'', and other harmful organic compounds can be treated. For example, in the conventional treatment method for Cr,
Cr" does not form hydroxide, so Na2S
Previously, O2, NaH3O3, etc. were added, Cr3+ was formed at one end, and then the hydroxide was formed and removed from the solution. Since it is possible to reduce to Cr'', there is no need to use the above-mentioned reducing agent that generates a bad odor during the reaction. Also CN
- and harmful organic compounds can also be decomposed into CO□ and the like by an oxidation reaction in the electrolyte separated by the diaphragm photoelectrochemical device.

Comparing the waste liquid treatment method according to the present invention with known treatment methods, there are the following advantages.

In other words, in the conventional technology, waste liquid is treated by redox reaction using chemicals, electricity, and microorganisms, so this method has disadvantages such as residual chemicals, bad odors, etc., and high cost. On the other hand, the method of waste liquid treatment in the present invention is to treat waste liquid by an oxidation-reduction reaction that occurs in the process of converting energy such as sunlight into chemical energy. It is a clean waste liquid treatment method that does not leave behind chemicals or generate bad odors, as it only requires filling one side of the partition with a chemical element with water and the other side with waste liquid. Considering this aspect, it can be said to be an economically efficient method because it is a waste liquid treatment method that uses sunlight that is not in danger of being depleted.

[Example 13] Furthermore, sterilization can be achieved by utilizing the reaction in the dark area on the back side separated by the diaphragm photoelectrochemical device of the present invention. If the bacterial cells to be sterilized can be sterilized by a reduction reaction, the purpose can be achieved by using an N-type semiconductor for the light irradiation surface. Conversely, if it is a bacterial cell that is sterilized by an oxidation reaction,
This objective can be achieved by using a P-type semiconductor for the light irradiation surface. In addition, if there is dissolved oxygen in the electrolyte behind the dark area, even if the light irradiation surface is an N-type semiconductor, OH radicals with strong oxidizing power will be generated due to reactions such as α group ~ Q91. In addition, it is also possible to sterilize bacterial cells by oxidation reaction.

H'+Oz+e--' HOz -08
)80□＋H” +e−→2 )10
□0 Comparing the above sterilization method of the present invention with well-known sterilization methods such as heat treatment, radiation irradiation, and chemical treatment,
It has the following advantages. In other words, the well-known sterilization methods have problems in that the quality of the product changes due to heating or the like, and the chemicals used for sterilization remain. However, in the present invention, microorganisms are sterilized directly by converting energy such as sunlight into chemical energy, or in an aqueous solution, by OH radicals generated in the process, so no heat is generated. It is possible to prevent deterioration of products, etc. without causing any damage. In this case, the excess OH
Even if radicals are generated, there is no problem because they will recombine and disappear. Another great advantage is that by sterilizing the solution with the solution on the back side of the diaphragm photoelectrochemical device, it is possible to prevent the product from deteriorating without exposing it to direct light. As described above, the present invention can be said to be an inexpensive and simple membrane surface method that can maintain product quality.

[Example 14] As a further application of the sterilization in the dark, it is possible to sterilize face masks that are harmful to the human body. For example, by using optical fibers, etc., it is possible to introduce light into the part of the human body where the bacterial cells are located. there is no problem. In other words, with optical fiber etc.
By introducing strong light into the human body, it is possible to sterilize bacteria that are harmful to the human body.

To be more specific, treatments using strong light called lasers have traditionally been carried out in medical equipment, and the following describes one example of laser therapy, which is used for cancer treatment. do.

Hematoporphyrin derivatives (HpD) have the property of selectively remaining in cancer cells for a longer period of time than in normal cells.

When this Hp D is injected intravenously, it moves to cancer cells. Next, when krypton ion laser ultraviolet light (wavelength 406 nm, output 500 mW) is guided into the human body through an optical fiber, )lpD is excited by this light and fluoresces. This fluorescence is measured using a spectroscope or high-intensity photoelectric detector to find the affected area. Next, apply a red variable wavelength dye laser (wavelength 630 nm, output approximately 3
A cancer treatment method has also been implemented in which cancer cells are killed by irradiation at 00 mW for 20 to 30 minutes.

This method has the advantage that since HpD has the property of selectively absorbing light, it can be treated without damaging surrounding cells.

However, as the laser beam is continuously irradiated wE, the tissue near the treated surface becomes opaque to the laser beam, and the laser beam cannot reach the deep part, making it difficult to treat the deep part.

Additionally, Hp D has the disadvantage of causing a side effect of photosensitivity, which is severe skin inflammation under direct sunlight. As described above, the conventional medical treatment using laser light has a high therapeutic ability, but at the same time has strong side effects. However, in the treatment method using the material of the present invention, the surface of the diaphragm-type photoelectrochemical device is irradiated with light through an optical fiber, etc., without directly irradiating the human body with light, so that the treatment of the affected area can be performed even on the back side. Since it is possible, it has the advantage of having no side effects.

[Brief explanation of the drawing]

The drawings show examples of the redox method and diaphragm type photoelectrochemical device according to the present invention, FIG. 1 is an explanatory diagram showing the redox reaction, and FIGS. 2 to 9 are different examples showing the redox reaction. An explanatory diagram of an example, Fig. 10 is a front view of the plating device, Fig. 11
The figure is a cross-sectional view of the same as above, Figure 12 is an exploded cross-sectional view of the same as above,
Figure 3 is a plan view of the same as above, Figure 14 is an exploded sectional view of the same as above, Figure 15 is a graph showing the relationship between light irradiation time and amount of platinum precipitation, and Figure 16 is a graph showing the relationship between light irradiation time and amount of copper precipitation. The graph shown in Figure 17 is a graph showing the relationship between the light irradiation time and the amount of lead precipitation, and Figure 18 is a schematic diagram showing the hydrogen gas generator.
Figures 9 and 20 are graphs showing the relationship between light irradiation time and hydrogen generation amount, Figure 21 is a graph showing the relationship between p-benzoquinone concentration and transition time, Figure 22 is a schematic diagram of a wet photovoltaic cell,
FIG. 23 is a schematic diagram of the photosynthesis apparatus, FIGS. 24 and 25 are graphs showing the relationship between light irradiation time and methanol concentration, and FIG. 26 is a chart of gas chromatography. (1)...Semiconductor, (1n)...N-type semiconductor, (1P)...P-type semiconductor, (2)...
...Diaphragm, (3) ...Electrolyte, (3a)
... Electrolyte of oxidation tank, (3b) ... Electrolyte of reduction tank, (4) ... Electrolytic tank, (4a) ...
...Oxidation tank, (4b) ...Reduction tank, (5)
......Light irradiation part, (6)......Salt bridge, (7
)・・・Metal, (8)・・・Conductive material.

Claims (19)

[Claims] (1) Electrolyte (3) at diaphragm (2) containing semiconductor (1)
) is separated and the contact interface between the semiconductor (1) and the electrolyte (3) is irradiated with light to cause an oxidation reaction in one electrolyte (3a) and at the same time to cause an oxidation reaction in the other electrolyte (3b). An oxidation-reduction method characterized by causing a reduction reaction within the body. (2) Two electrolytic cells (4a) and (4b) partitioned by a diaphragm (2) having a semiconductor (1) are formed, and the diaphragm (2)
1. A diaphragm-type photoelectrochemical device characterized in that a light irradiation part (5) is formed in the semiconductor (1). (3) Both electrolytic cells (4a) and (4b) are connected to a salt bridge (6).
A diaphragm-type photoelectrochemical device according to claim (2). (4) The diaphragm-type photoelectrochemical device according to claim (2), wherein both the electrolytic cells (4a) and (4b) are connected by an ion-permeable membrane (25). (5) The diaphragm-type photoelectrochemical device according to any one of claims (2) to (4), wherein the diaphragm (2) is composed of an N-type semiconductor film (1n). element. (6) The diaphragm-type photoelectrochemical device according to any one of claims (2) to (4), wherein the diaphragm (2) is composed of a P-type semiconductor film (1P). element. (7) The diaphragm (2) is constructed by laminating an N-type semiconductor film (1n) and a conductive metal (7). The diaphragm-type photoelectrochemical device according to the above item. (8) The diaphragm (2) is constructed by laminating a P-type semiconductor film (1P) and a conductive metal (7). The diaphragm-type photoelectrochemical device according to the above item. (9) The diaphragm (2) is constructed by laminating an N-type semiconductor film (1n) and a P-type semiconductor film (1P). The diaphragm-type photoelectrochemical device according to any one of the items. (10) The two electrolytic cells are composed of an oxidation tank (4a) and a reduction tank (4b), and the oxidation tank (4a) for semiconductor (1)
The diaphragm-type photoelectrochemical device according to any one of claims (2) to (9), wherein a substance that promotes oxidation is attached to the surface in contact with the diaphragm type photoelectrochemical device. (11) The two electrolytic cells are composed of an oxidation tank (4a) and a reduction tank (4b), and a reduction tank (4b) for the semiconductor (1).
The diaphragm-type photoelectrochemical device according to any one of claims (2) to (10), wherein a substance that promotes reduction is attached to a surface in contact with the diaphragm. (12) The two electrolytic cells are composed of an oxidation tank (4a) and a reduction tank (4b), and the electrolyte (3) in the oxidation tank (4a)
The diaphragm-type photoelectrochemical device according to any one of claims (2) to (8), wherein a) contains a substance that promotes oxidation. (13) The two electrolytic cells are composed of an oxidation tank (4a) and a reduction tank (4b), and the electrolyte (3) in the reduction tank (4b)
The diaphragm-type photoelectrochemical device according to any one of claims (2) to (12), wherein b) contains a substance that promotes reduction. (14) The two electrolytic cells are composed of an oxidation tank (4a) and a reduction tank (4b), and the reduction tank (4b) has an electrolyte (3
Any one of claims (2) to (5), in which a plating solution in which metal is dissolved is supplied as b),
Or the diaphragm-type photoelectrochemical device according to item (7) or any one of items (9) to (13). (15) The two electrolytic cells are composed of an oxidation tank (4a) and a reduction tank (4b), and the reduction tank (4b) has an electrolytic solution (3
The diaphragm-type photoelectrochemical device according to any one of claims (2) to (13), wherein an acidic aqueous solution is supplied as b). (16) The electrolytic cell (4) is supplied with an aqueous solution containing an organic compound in the electrolytic solution (3). The diaphragm type photoelectrochemical device described above. (17) The electrolytic layer (4) is supplied with a non-aqueous solution containing an organic solvent in the electrolytic solution (3). The diaphragm type photoelectrochemical device described above. (18) The electrolytic cell (4) is supplied with waste liquid as the electrolytic solution (3).
13) The diaphragm-type photoelectrochemical device according to any one of the items. (19) The two electrolytic cells are composed of an oxidation tank (4a) and a reduction tank (4b).
) is electrically connected by a conductive material (8), the diaphragm type photoelectrochemical device according to any one of claims (2) to (18).