Electrode for electrolysis and electrolysis unit

Abstract

There are disclosed an electrode for electrolysis capable of efficiently forming ozone by electrolysis of an electrolytic solution (e.g., water) at ordinary temperature with a low current density, and an electrolysis unit using the electrode. The electrode for electrolysis includes a substrate and a surface layer formed on the surface of the substrate, and the surface layer is made of an amorphous insulator, for example, a thin film of amorphous tantalum oxide, amorphous tungsten oxide or amorphous aluminum oxide.

Description

BACKGROUND OF THE INVENTION[0001]The present invention relates to an electrode for electrolysis for use in an industrial or household electrolysis process.[0002]In general, ozone is a substance having a very strong oxidizing power, and it is expected that water in which ozone is dissolved, so-called ozone water is applied to a broad range of cleaning sterilization treatment of water and sewage, food and the like, and a cleaning treatment of a semiconductor device manufacturing process. As methods for forming the ozone water, there are known a method for dissolving, in water, ozone formed by irradiation with an ultraviolet ray or electric discharge, a method for forming ozone in water by electrolysis of the water, and the like.[0003]In Japanese Patent Application Laid-Open No. 11-77060 (Patent Document 1), an ozone water forming device is disclosed which includes ozone forming means for forming an ozone gas with an ultraviolet lamp and a tank to store water, whereby the formed ozone ...

AI Technical Summary

Benefits of technology

[0021]Therefore, the electrons move with a higher energy level, whereby an ozone forming efficiency for causing the ozone forming reaction can be raised.

[0022]According to the invention of the fourth aspect, in the above inventions, the insulator is aluminum oxide, so that the electrode for electrolysis according to the above inventions can be made of a comparatively inexpensive material, and production cost can be reduced. Moreover, any toxic substance such as lead dioxide is not used, whereby an environmental load can be reduced.

[0023]According to the invention of the fifth aspect, in the above inventions, the thickness of the surface layer is in a range of 20 nm or more to 2000 nm or less, so that the surface layer can be made of a thin film, and the electrons can move in the electrode via impurities of the surface layer or Fowler-Nordheim tunneling. Therefore, owing to an electrode reaction in the anode, the empty level around the bottom of the conduction band at the energy level higher than Fermi level as much as about the half of the band gap can receive the electrons from the electrolyte, and the movement of the electrons is caused with the higher energy level, whereby the electrolysis can be performed with the low current density, and ozone can efficiently be formed.

[0024]According to the invention of the sixth aspect, in the above inventions, the substrate is provided with the intermediate layer positioned on the inner side of the surface layer and formed of the metal which is not easily oxidized on the surface of the substrate. Therefore, the electrode reaction can be caused with the high energy level in the surface of the surface layer. In consequence, ozone can efficiently be formed with a lower current density.

[0025]In particularly, according to such inventions, the intermediate layer is formed of the metal which is not easily oxidized on the surface of the substrate. Therefore, when the electrolysis is performed with the electrode, it is possible to avoid a disadvantage that the substrate surface is oxidized and non-conducted. In consequence, durability of the electrode can be improved. As compared with the whole substrate is made of the material constituting the intermediate layer, the production cost can be reduced. Even in such a case, ozone can similarly efficiently be formed.

[0026]In the electrolysis unit according to the invention of the seventh aspect, the anode having the water permeability is constituted of the electrode for electrolysis according to the above inventions, and the anode and the cathode having the water permeability are arranged on both the surfaces of the cation exchange film. Therefore, protons move in the cation exchange film, whereby even when the electrolytic solution is pure water, ozone can efficiently be formed.

Problems solved by technology

However, in the above-mentioned ozone water forming method for generating the ozone gas by the ultraviolet lamp or the discharge system described above to dissolve this ozone gas in the water, the ozone gas forming device, an operation for dissolving the ozone gas in the water and the like are required, so that the device is liable to become complicated.

The method is a method for dissolving the formed ozone gas in the water, and hence it has a problem that it is difficult to efficiently form the ozone water having a desired concentration.

However, in the method disclosed in Patent Document 3 described above, diamond is used as an electrode substance, and hence there is a problem that cost of the device itself soars.

However, the element as the electrode for forming ozone has a low ozone forming efficiency, and it is difficult to efficiently form the ozone water by an electrolysis process.

This raises a problem that very high energy is consumed.

Furthermore, platinum is expensive.

When lead dioxide is used instead of platinum, there is a problem of toxicity.

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