JPH07161359A - Gas diffusion electrode - Google Patents

Abstract

PURPOSE:To collectively absorb electrolyte and dirt leaked in a gas diffusion layer during electrolytic operation so as to prevent the decrease in gas supply capacity and drastically increase electrode life by providing a continuous specific hydrophilic part on a part of the surface of the gas diffusion layer. CONSTITUTION:For example, a sheet formed by spraying mixture of hydrophile carbon block and PTFE in a lattice shape on a reaction layer of 0.1mm in width, a gas diffusion layer of 0.4mm in width, current collecting mesh, and a diffusion back sheet of 0.2mm in width is put in a jig and hot pressed so as to form a gas diffusion electrode having continuous hydrophile property on a part of a surface of the gas diffusion layer. The contact angle of hydrophilic part with water is set to small, 30 degree or less. Therefore electrolyte and dirt leaked during electrolytic operation are absorbed so as to prevent any decrease in gas supply capacity and resultanty increase electrode life drastically.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to improvements in gas diffusion electrodes.

[0002]

2. Description of the Related Art Conventionally, in a gas diffusion electrode composed of a reaction layer and a gas diffusion layer, the surface of the gas diffusion layer on the gas supply side has uniform water repellency over the entire surface. For this reason, when used for long-term electrolysis, the surface of the gas diffusion layer will have reduced water repellency due to electrolyte leakage, dirt adhesion, etc., and water droplets will adhere and gas supply will be impeded, resulting in electrode life. There was a problem that was short.

[0003]

Therefore, the present invention is intended to provide a gas diffusion electrode having a long electrode life, which is free from leakage of electrolyte and adhesion of dirt to the gas diffusion layer, does not deteriorate in gas supply ability. To do.

[0004]

The gas diffusion electrode of the present invention for solving the above problems is characterized in that a continuous hydrophilic portion is provided on a part of the surface of the gas diffusion layer on the gas supply side. It is what

[0005]

As described above, in the gas diffusion electrode of the present invention, the hydrophilic portion having a continuous contact angle with water of 30 degrees or less is provided on a part of the surface of the gas diffusion layer on the gas supply side. During the electrolysis operation, leakage of electrolyte and dirt are absorbed by the hydrophilic portion, and the water repellency of the water repellent portion is less likely to decrease. Further, even if water drops adhere to the electrode surface due to fluctuations during the electrolysis operation, the water drops are quickly absorbed by the hydrophilic part. Therefore, unlike the conventional gas diffusion electrode, there is no obstruction of gas supply due to the growth of water droplets, and the life of the electrode is significantly extended.

[0006]

EXAMPLE An example of the gas diffusion electrode of the present invention will be described. On a reaction layer having a thickness of 0.1 mm, a gas diffusion layer having a thickness of 0.4 mm, a current collecting network, and a gas diffusion backing sheet having a thickness of 0.2 mm, , Put a sheet in which a mixture of hydrophilic carbon black and PTFE (polytetrafluoroethylene) is sprayed in a grid pattern into a jig,
Hot pressing was performed to prepare a gas diffusion electrode having a continuous hydrophilic portion on a part of the surface of the gas diffusion layer. In addition, another embodiment will be described. A water-repellent sheet having a thickness of 2 mm and a thickness of 0.5
mm hydrophilic sheets are stacked alternately to make a thickness of 120 mm,
This was vertically sliced to a width of 0.2 mm to prepare a gas diffusion backing sheet having a thickness of 0.2 mm. This gas diffusion backing sheet was laminated with a 0.1 mm thick reaction layer, a 0.4 mm thick gas diffusion layer, and a current collecting net on top of it in a jig in the same manner as in the above example, and hot pressed to remove the gas. A gas diffusion electrode having a continuous hydrophilic portion on a part of the surface of the diffusion layer was prepared. Further, another example will be described. A Nafion solution (surfactant) was sprayed on the surface of a gas diffusion layer in a gas diffusion electrode composed of a reaction layer and a gas diffusion layer at a width of 1.0 mm at intervals of 3 mm, A heat treatment was carried out at 200 ° C. for 30 minutes to prepare a gas diffusion electrode having a continuous hydrophilic portion on a part of the surface of the gas diffusion layer. These gas diffusion electrodes and conventional gas diffusion electrodes are
When it was used as an oxygen reduction electrode in aOH and the electrode performance was measured, the conventional gas diffusion electrode showed a decrease in battery voltage of 60 mV in 1000 hours, but the gas diffusion electrode of each example was 1700.
Almost no change in battery voltage was observed even after the lapse of time.

[0007]

As described above, since the gas diffusion electrode of the present invention has a continuous hydrophilic portion on a part of the surface of the gas diffusion layer,
During the electrolysis operation, the electrolytic solution and dirt that have leaked to the gas diffusion layer on the gas supply side are concentrated on the hydrophilic part, and the gas supply capacity does not decrease, so the electrode life is greatly extended.

Claims (1)

[Claims] 1. A gas diffusion electrode, wherein a part of the surface of the gas diffusion layer on the gas supply side of the gas diffusion electrode is provided with a hydrophilic portion having a continuous contact angle with water of 30 degrees or less. .