JPS6153831B2 - - Google Patents

Description

[Detailed description of the invention]

[Technical field to which the invention pertains] The present invention relates to a method for manufacturing a fuel cell electrode formed by laminating a carbon catalyst layer and a sintered nickel layer. [Prior art and its problems] In order to prevent fuel or oxidant gas that comes into contact with the carbon catalyst layer made of activated carbon, carbon black, or graphite from blowing through to the electrolyte side, such an electrode is used as a liquid-side layer for electrolysis. It has a porous sintered nickel layer that is easily wetted by liquid, and the three-phase interface where the reaction proceeds (the surface where gas, electrolyte, and catalyst come into contact with each other) is fixed within the catalyst layer. .
Bonding between the carbon catalyst layer and the sintered nickel layer is carried out by mixing polytetrafluoroethylene resin in the catalyst layer and hot pressing it together with the nickel layer.In this case, increasing the binder content Much of the catalyst surface is covered with binder, reducing catalyst performance.
On the other hand, if the binder content is reduced, interlayer peeling will occur after long-term discharge, resulting in a decrease in electrode performance. [Object of the Invention] In contrast, an object of the present invention is to provide a method for manufacturing a fuel cell electrode that firmly binds a carbon catalyst layer and a sintered nickel layer without using a large amount of binder. [Summary of the Invention] According to the present invention, this object is achieved by laminating and pressing a layer of a mixture of nickel powder and resin and a layer of a mixture of powder and resin whose sintering temperature is higher than that of nickel. Sintering is performed at a temperature higher than the sintering temperature of the granules and lower than the sintering temperature of the granules, and the adhered granules are removed to create a sintered nickel layer having an uneven surface with granule traces, and the unevenness of the nickel layer is This is achieved by stacking a carbon catalyst layer containing a binder on the surface and press-molding it at high temperature. [Embodiments of the Invention] The present invention will be described below with reference to Examples and figures. <Example> Nickel powder and polyvinyl acetate resin are kneaded and formed into a 0.3 mm thick sheet. Also, carbon powder is used as the granules whose sintering temperature is higher than that of nickel, and the carbon powder and polyvinyl acetate resin are kneaded and similarly formed into a 0.3 mm thick sheet.
Next, both sheets are stacked and formed again into a sheet with a thickness of 0.3 mm. When this sheet is heat-treated at 900°C for 1 hour in a hydrogen stream, the resin in the sheet is decomposed and volatilized, and the nickel powder layer is sintered. However, since the carbon powder layer is not sintered at this temperature, the powder is weakly attached to the sintered nickel layer as a layer of agglomerated secondary particles. Therefore, by scrubbing off the adhered secondary particles of carbon powder with a brush while cleaning the surface of this sintered nickel layer, the secondary particles of carbon powder are crushed and removed from the sintered nickel layer.
On the other hand, on the surface of the sintered nickel layer that was in contact with the carbon powder, unevenness is formed due to a large number of particle marks corresponding to the roughness of the secondary particles of the carbon powder, and the cross section of these unevenness is similar to that of the secondary particles of the nickel powder. After the particles are intricately entangled with the secondary particles of carbon powder at the interface and sintered,
The secondary particles are crushed and removed, resulting in a HOOK shape. Here, the term "hook shape" refers to a shape in which the tip of the convex part protrudes laterally to narrow the opening of the concave part. In the above process of manufacturing a sintered plate, multiple layers of nickel and carbon are alternately stacked and thinned using rolls, and carbon powder is bitten into each nickel layer to simultaneously form multiple layers of nickel powder. Creating one is advantageous in terms of work efficiency. Further, instead of carbon powder, inorganic powder such as silica powder or alumina powder, or metal powder having a sintering temperature higher than the nickel sintering temperature can also be used. As shown in FIG. 1, a carbon catalyst layer 2 is placed on the uneven surface of the sintered nickel layer 1 thus obtained. The carbon catalyst layer 2 is made by mixing activated carbon powder containing 20 parts of silver with 20 parts of polytetrafluoroethylene resin as a binder and forming it into a sheet shape. The electrode 3 is obtained by pressure molding. In the electrode created in this manner, the powder of the carbon catalyst layer is embedded in the unevenness of the grain traces of the sintered nickel layer, and a strong bond is obtained at the boundary due to the so-called wedge effect. Table 1 compares the bonding strength between the electrode body obtained in this example and an electrode in which a carbon catalyst layer containing the same amount of binder as in the example was bonded to a sintered nickel layer with a smooth surface. and show. It can be seen from this that the embodiment of the present invention is superior.

〔Effect of the invention〕

As described above, in the present invention, a sintered nickel layer having irregularities of particle traces is created in advance on the surface, and the carbon catalyst layer is bonded to the irregular surface, so that the powder of the catalyst layer bites into the recesses. , which obtains a strong bond between the nickel layer and the catalyst layer through the wedge effect, and there is no need to increase the amount of binder, so the catalyst performance is not impaired and the characteristics remain stable even after long discharges. An excellent fuel cell electrode can be obtained.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view of an electrode according to an embodiment of the present invention;
FIG. 2 is a diagram showing changes in potential during long-term discharge between the electrode shown in FIG. 1 and the conventional electrode. 1... Sintered nickel layer, 2... Carbon catalyst layer.

Claims (1)

[Claims] 1 After laminating and pressurizing a layer of a mixture of nickel powder and resin and a layer of a mixture of powder and resin whose sintering temperature is higher than that of nickel, the sintering temperature of the granules is set to a temperature higher than that of nickel. sintered at a lower temperature,
The adhering particles are removed to create a sintered nickel layer with unevenness of particle traces on the surface, and a carbon catalyst layer containing a binder is overlaid on the uneven surface of the nickel layer, followed by pressure molding at high temperature. A method for manufacturing a fuel cell electrode characterized by: