JPS62154571A - Gas diffusion electrode - Google Patents

Abstract

PURPOSE:To provide a gas diffusion electrode which is acid resistant and having a current collector whose resistance is low and collecting current is high by coating the surface of a net obtained by braiding wires comprising Ti, Ta, or Cu covered with Ti or Ta with a platinum group metal or its oxide. CONSTITUTION:A gas diffusion electrode 1 is produced in such a way that a gas diffusion layer 3 comprising hydrophobic carbon black and polytetrafluoroethylene having a ratio of 7:3 is connected onto a reaction layer 2 having fine hydrophilic parts and hydrophobic parts comprising a RuO2+IrO2 catalyst, hydrophobic carbon black, and polytetrafluoroethylene having a ratio of 3:3:2. and a current collector 7 obtained by braiding wires 6 made of Ti wire 4 coated with Pt 5 is connector 7 has acid resistance, and is not attacked by acid produced when it is used in fuel cell, secondary battery, electrochemical reactor, anode for electrolysis, anode for plating. In addition, since the current collector has low electric resistance, it can collect large current.

Description

Detailed Description of the Invention (Industrial Field of Application) The present invention relates to fuel cells, secondary batteries, electrochemical reactors,
This article relates to improvements in gas diffusion electrodes used in various electrolytic anodes, plating anodes, etc.

(Prior art and its problems) Conventionally, as a gas diffusion layer, carbon black, polytetrafluoroethylene was added to a reaction layer having fine hydrophilic and hydrophobic parts made of PT, carbon black, and polytetrafluoroethylene. There is one in which a hydrophobic gas diffusion layer is bonded, and a current collector made of a Cu wire mesh is bonded to the surface of the gas diffusion layer opposite to the reaction layer.

When this gas diffusion electrode is used in fuel cells, secondary batteries, electrochemical reactors, etc., the electrolyte passes through the reaction layer but does not pass through the gas diffusion layer, and only gas diffuses through the gas diffusion layer. . In this case, when Cβ2 and SO□ gas exist as decomposition gas from the electrolyte and supply gas together with water vapor on the collector side of the gas diffusion layer and HCI and HtSO's are generated, these acids cause Cu Since the current collecting material made of a wire mesh is disturbed, the collected current decreases over time.

For this reason, Ti, which is not exposed to acid, can be used instead of Cu%% material.
A current collector made of Ta% stainless steel and carbon cloth was bonded to the surface of the gas diffusion layer.

However, if the mesh is made of Ti, Ta, stainless steel, etc., a high-resistance oxide film will be formed on the surface, so the current collection will be extremely small, and the current collector material made of carbon cloth, which does not have an oxide film, will have a high resistance, so Cu wire The current collected is lower than that of an electrode made of a mesh.

Therefore, the present invention aims to provide a gas diffusion electrode equipped with a current collector material that is not susceptible to acids, has low resistance during current collection, and has a high current collection current.

(Means for solving the problems) The gas diffusion electrode of the present invention for solving the above problems includes:
A reaction layer containing fine hydrophilic and hydrophobic parts consisting of a platinum group metal or its oxide or both, carbon black and polytetrafluoroethylene is coated with a hydrophobic layer consisting of carbon fibers and polytetrafluoroethylene. The gas diffusion layer is joined, and the surface of the gas diffusion layer opposite to the reaction layer is provided with a mesh braided with a wire made of Ti or Ta or Ti or Ta-coated Cu, a large number of cotton, or a large number of through holes. A current collector coated with a platinum group metal, an oxide thereof, or both is bonded or embedded in at least a portion of the plate that is in contact with the gas diffusion electrode.

(Function) In the gas diffusion electrode of the present invention configured as described above, the current collector material bonded or embedded in the surface of the gas diffusion layer is Tt or Tt.
A, a wire rod made of Ti or Ta-coated Cu is braided and a net is formed, or a plate having a large number of wires or a large number of through holes is coated with at least the portion in contact with the diffusion layer, for example, Pt,
Ru0z, Ire,, PdO, Ru()z + I r
Since it is made of a material coated with either Oz, pt+Ir (llz), when used in fuel cells, secondary batteries, electrochemical reactors, etc., the gas generated by the reaction or the supplied gas will be used as a collector material for the gas diffusion layer along with water vapor. Even if acid is generated on the side, the current collector material has acid resistance and will not be eroded, and has low electrical resistance and can collect a high current.

An example of the gas diffusion electrode of the present invention will be described with reference to the drawings (Example 1).

The gas diffusion electrode 1 shown in FIG.
O□+I r Oz catalyst, hydrophobic carbon black with an average particle size of 450, and polytetrafluoroethylene with an average particle size of 0.3μ in a ratio of 3:3:2, thickness 0.1, width 12
Hydrophobic carbon black with an average particle size of 420 mm and polytetrafluoroethylene with an average particle size of 0.3 μ are mixed in a 7:3 reaction layer 2 having a length of 1201 m and having a fine hydrophilic part and a hydrophobic part.
A gas diffusion layer 3 having a thickness of 0.51 mm and having a ratio of Add 5μ of Pt5 to
As shown in FIG.
It is made by joining a steel current collector material 7 braided with 5 mm in width and 1201 m in length.

(Example 2) In the gas diffusion electrode 8 shown in FIG. 3, the thickness of the gas diffusion layer 3 is Q.
, a reaction layer 2 made of the same material and the same dimensions as above except for 3 mm.
and the gas diffusion layer 3, and on the surface of the gas diffusion layer 3 opposite to the reaction layer 2, as shown in FIG.
A current collector 14 consisting of 80 wires 13 made of a clad wire 11 made of Cu%%9 coated with Ti1O with a thickness of 0.1 mm and a wire 13 coated with 2 μm of RuOz12 is 1.5 mm in the width direction as shown in FIG. It is embedded in the interval.

These gas diffusion electrodes 1.8 and a conventional gas diffusion electrode of the same dimensions as shown in FIG. 1, which is a cloth with a width of 12On+ and a length of 120U, in which the current collecting material is braided with carbon fibers with a diameter of 8μ, were each mixed with an electrolyte of ZnC7! 01 on 2+! When used in a +NaCβ secondary battery, the current collecting material made of carbon of the conventional gas diffusion electrode is such that Cβ2 gas generated by the reaction during charging diffuses through the gas diffusion layer 3 together with water vapor, and HC6 is generated. Although it is not corroded by I-(Ce), the current collecting current was as low as 50 mA/cal due to the large electrical resistance, whereas current collecting material 7.1 of gas diffusion electrode 1.8 in Example
4, even though the C12 gas generated by the reaction during charging diffuses and permeates through the gas diffusion layer 3 together with water vapor to generate HCff, it is not corroded by the HCl, and the electric resistance is small, so the current collecting current is 500 m. High A/cA,
Even after the passage of time, there was almost no significant difference and the value remained high.

In addition, when 25% NaCl was electrolyzed at 90°C using a gas diffusion electrode with the same dimensions and the same material as in Example 1 and the conventional example, except for carrying RuO□ in the reaction layer, as the chlorine generating electrode for salt electrolysis, The electrode of the present invention enables electrolysis with a low overvoltage of 35 mV at a current density of 2 A/crA and is stable with no change over time, whereas the conventional gas diffusion electrode is stable without any change over time. However, 0.5A/
At an electrode density of c+a, the overvoltage was as high as 200 mV.

In addition, in the above-mentioned Example 1, an example was described in which a single mesh was used as the current collecting material, but the invention is not limited to this. For example, it is possible to use multiple meshes stacked on top of each other, or to use a plate-like material to reinforce the electrode itself. It is also possible to do so.

(Effects of the Invention) As can be seen from the above explanation, the gas diffusion electrode of the present invention has acid resistance because the current collector bonded or embedded in the surface of the gas diffusion layer has acid resistance. When used in commercial reactors, various electrolytic anodes, plating anodes, etc., the current collected does not decrease over time because it is not corroded by the generated acid, and the electrical resistance of the current collecting material is Since it is small, a large current can be collected, and its practical effects are extremely large.

[Brief explanation of drawings]

FIG. 1 is a partially cutaway perspective view showing an embodiment of a gas diffusion electrode according to the present invention, FIG. 2 is an enlarged cross-sectional view of a wire forming a current collector in the gas diffusion electrode, and FIG. 3 is a cross-sectional view of a wire material according to the present invention. FIG. 4 is a partially cutaway perspective view showing another embodiment of the gas diffusion electrode, and FIG. 4 is an enlarged cross-sectional view of a wire forming a current collector in the gas diffusion electrode. Applicant: Tanaka Kikinzoku Kogyo Co., Ltd. Figure 2 7... Roasted material Figure 4

Claims (1)

[Claims] A hydrophobic gas diffusion layer made of carbon black and polytetrafluoroethylene on a reaction layer having fine hydrophilic parts and hydrophobicity made of a platinum group metal or its oxide or both, carbon black, and polytetrafluoroethylene. are joined,
On the surface of the gas diffusion layer opposite to the reaction layer, at least the gas diffusion layer is a braided net made of wire made of Ti or Ta or Ti or Ta-coated Cu, or a plate having a large number of wires or a large number of through holes. A gas diffusion electrode in which a current collector coated with a platinum group metal, its oxide, or both is bonded or embedded in the part in contact with the metal.