JP2848726B2 - Gas diffusion electrodes for fuel cells - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a gas diffusion electrode for a fuel cell in which platinum is supported by a specific method.

[0002]

2. Description of the Related Art As a technique for supporting platinum on a gas diffusion electrode for a fuel cell, for example, Journal of Power
Power Sources, vol. 29 (1.
990) 367-387 describes the chemical loading of platinum.
It describes that a mixture of the same amount of ethanol in a 0.05 MH ₂ SO ₄ solution containing 1% of H ₂ PtCl ₆ is brushed on the electrode surface. As shown in this paper, the application of a platinum solution has conventionally been performed in air.

[0003]

As described above, since the conventional application of the platinum solution to the gas diffusion electrode for a fuel cell has been performed in the atmosphere, the platinum solution is applied to the micropores in the gas diffusion electrode. There was a problem that the activity of the platinum catalyst was low due to insufficient permeation and the fact that adsorbed substances adsorbed on the gas diffusion electrode in the air hindered contact between platinum and the gas diffusion electrode. .

[0004]

SUMMARY OF THE INVENTION In order to solve the problems of the conventional gas diffusion electrode for a fuel cell impregnated with platinum, the present invention provides a method of degassing in a vacuum and maintaining the vacuum. After impregnation with a platinum solution or introduction of an inert gas, the pressure is reduced again to provide a gas diffusion electrode for a fuel cell impregnated with and supported by a platinum solution.

A method for manufacturing a gas diffusion electrode for a fuel cell according to the present invention will be described with reference to the drawings.

FIG. 1 shows a specific example of an apparatus used for producing a gas diffusion electrode for a fuel cell employed in the present invention.
1 is a vacuum chamber for performing a platinum loading process,
Reference numeral 102 denotes a gas diffusion electrode for carrying platinum.
108 is a vacuum pump for evacuating the vacuum chamber, and 104 is a vacuum exhaust valve. 10
Reference numeral 3 denotes a heater for raising the temperature of the gas diffusion electrode 102. Reference numeral 106 denotes a platinum solution reservoir for temporarily holding the platinum solution 107, and reference numeral 105 denotes a platinum solution introduction valve for introducing the platinum solution 107 into the vacuum chamber 101.

In order to support platinum on the diffusion electrode 102 using the apparatus shown in FIG. 1, first, the platinum solution introduction valve 1 shown in FIG.
05 is closed, the evacuation valve 104 is opened, and the vacuum pump 108 is operated to evacuate the vacuum chamber 101.

Next, when the pressure in the vacuum chamber reaches a predetermined pressure or less (eg, 1 Torr or less), the heater 103
To the gas diffusion electrode at a predetermined temperature range (for example, 100 to 300 ° C., preferably 190 to 220 ° C.).
℃). At this time, the adsorbed substance adsorbed on the gas diffusion electrode is desorbed.

When the degree of vacuum is lower than a predetermined pressure (for example, 0.0
When the pressure reaches 1 Torr or less, or after a lapse of a predetermined time (for example, 4 hours), the power supply to the heater is stopped.

When the gas diffusion electrode is at a predetermined temperature (for example, 40
(° C.) or less, the platinum solution 107 is added to the platinum solution reservoir 106, the platinum solution introduction valve 105 is gradually opened, and the platinum solution is introduced into the vacuum chamber 101 while preventing air from entering the vacuum chamber. .

When the inert gas is introduced, after the vacuum desorption process is completed, the inert gas introduction valve 109 is opened to introduce the inert gas into the vacuum chamber. Thereafter, the vacuum is applied again and the platinum solution introduction valve 105 is opened to introduce the platinum solution into the vacuum chamber 101.

[0012]

Next, the present invention will be described specifically with reference to examples.

A sheet of acetylene black mixed with PTFE having a thickness of 400 μm as a gas diffusion electrode is placed in a vacuum chamber, evacuated at room temperature for 15 minutes, and then electric power is supplied to a heater. Was raised to 190-220 ° C. and held at that temperature for 3 hours.

Thereafter, the power supply to the heater was stopped and the temperature was cooled to room temperature. Then, the vacuum evacuation valve was closed, and a platinum solution [0.05 mol / dm ^{3 of} chloroplatinic acid ethanol solution] was introduced into the vacuum chamber. The platinum solution was immersed in the diffusion electrode and left for 5 minutes to allow the platinum solution to permeate the gas diffusion electrode.

Thereafter, the gas diffusion electrode was taken out of the vacuum chamber and dried with hot air (70 to 90 ° C.).

Next, this gas diffusion electrode was left at 140 ° C. for 5 hours in a hydrogen atmosphere to reduce platinum. The amount of the platinum catalyst was 0.45 mg / cm ² .

On the surface of this gas diffusion electrode, Nafion (Naf)
ion) solution (Aldrich Chemical) 0.016 ml
/ Cm ² and vacuum-dried at 70 ° C., and then press the side coated with the nafion solution against a proton conductor membrane (Nafion 117: manufactured by DuPont) and hot-press at 130 ° C. and 120 kg / cm ² for 60 seconds. Then, a joined body of a gas diffusion electrode and a proton conductor membrane was produced.

FIG. 2 shows the performance of this assembly as a fuel cell.
Shown in FIG. 2 also shows, as a comparative example, the performance of a joined body using a gas diffusion electrode in which a platinum solution is immersed and carried in air.

The operating conditions are as follows.
%, Hydrogen pressure 1 atm, oxygen on the air electrode side 100%, oxygen pressure 1 atm, and cell temperature was 55 ° C.

As shown in FIG. 2, at each current density, the joined body using the gas diffusion electrode of the present invention has a higher output voltage over the entire current range than the conventional example.

[0021]

As described above, the performance of a fuel cell can be improved by producing a gas diffusion electrode carrying platinum by impregnating the gas diffusion electrode with a platinum solution in a vacuum. The gas diffusion electrode of the present invention is effective when used for a gas diffusion electrode used in a solid polymer electrolyte fuel cell or the like.

[Brief description of the drawings]

FIG. 1 is a specific example of an apparatus for manufacturing a gas diffusion electrode for a fuel cell according to the present invention.

FIG. 2 is a graph showing the performance of a solid polymer electrolyte fuel cell using a gas diffusion electrode of the present invention and the performance of a solid polymer electrolyte fuel cell using a conventional gas diffusion electrode.

[Explanation of symbols]

101: vacuum chamber, 102: gas diffusion electrode, 10
3 ... Heater, 104 ... Vacuum exhaust valve, 105 ... Platinum solution introduction valve 106 ... Platinum solution reservoir, 107 ... Platinum solution, 108 ... Vacuum pump 109 ... Inert gas introduction valve

──────────────────────────────────────────────────続 き Continuation of front page (56) References JP-A-58-166647 (JP, A) JP-A-61-96668 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) H01M 4/86-4/98

Claims (2)

(57) [Claims] 1. A gas diffusion electrode for a fuel cell, wherein a platinum solution is impregnated and supported while maintaining a vacuum after degassing in a vacuum. 2. A gas diffusion electrode for a fuel cell, wherein after degassing in a vacuum, an inert gas is introduced, the pressure is reduced again, and a platinum solution is impregnated and supported.