Patent Application
20100201021
The present invention relates to a membrane electrode assembly (MEA); more particularly, relates to forming two flat catalyst electrode layers (CEL) on two surfaces of a proton exchange membrane (PEM) separately and controlling a thickness of CEL on the MEA.
A prior art of fabricating an MEA of a fuel cell by printing comprises the following steps:
(a) An ion exchange membrane, an anode catalyst solution and a cathode catalyst solution are prepared.
(b) A desired size of the ion exchange membrane is cut out and put upon a base plate of screen printer.
(d) The ink of a catalyst is evenly screen printed on the ion exchange membrane by using a scraper.
(f) After the ion exchange membrane is laid flat, a catalyst layer is formed on the ion exchange membrane.
Although the prior art forms an anode or cathode catalyst layer on the ion exchange membrane, the ion exchange membrane may easily be wrinkled on touching the anode or cathode catalyst ink. Thus, a catalyst coated PEM layer obtained in this way is wrinkled, not flat. Additional processes for getting rid of the wrinkle are usually required. And, so, processes of printing and wrinkle-removing are repeated for times on coating a thick catalyst layer. Hence, the prior art does not fulfill all users' requests on actual use.
The main purpose of the present invention is to form flat MEA with a CEL thickness controllable.
To achieve the above purpose, the present invention is a method for fabricating a membrane electrode assembly, comprising steps of preparing, inputting a material, forming, changing side, inputting a material again and forming again, where a temperature-controllable suction plate, which is on the inlet of a vacuum device, is used to suck-flat a PEM; a hollow of a template deposed on the PEM is filled with designed amount of the ink (or said slurry) of catalyst material and then keeps the temperature of the suction plate at the binding temperature for the slurry of catalyst material and the PEM; a convex part of a pressing plate is correspondingly pressed into the hollow of the template to form the first CEL on a surface of the PEM; after cooling down of the suction plate, the PEM is turned over; the slurry of another catalyst material is poured in and a binding temperature is reached; and the convex part of the pressing plate is correspondingly pressed into the hollow of the template to obtain a second CEL′ on another surface of the PEM. Accordingly, a novel method for fabricating a MEA is obtained.
The present invention will be better understood from the following detailed description of the preferred embodiment according to the present invention, taken in conjunction with the accompanying drawings, in which
The following description of the preferred embodiment is provided to understand the features and the structures of the present invention.
Please refer to
Please further refer to
(a) Preparing 1: A vacuum facility 71 is obtained, which is not heated up; or is heated up with a temperature controlled. A suction plate 72 which is set on the inlet of the vacuum facility 71, is made of a drilled plate, a framed plate, a plate of screens, or a sintering material or any combination of the above. A PEM 73 is set on the suction plate 72. The PEM 73 is horizontally fixed on the suction plate through a vacuum effect. Then a template 74 with a hollow 741 is set on the PEM 73.
(b) Inputting material 2: A slurry of anode or cathode catalyst material 8,8a is poured into the hollow 741 of the template 74 in the MEA chamber 7. A temperature-controllable heater 721 in the vacuum facility 71 is activated to heat the suction plate, to raise a temperature to bind the slurry of anode or cathode catalyst material 8,8a and the PEM 73. (If the binding is processed in a room temperature, the temperature is not raised.)
(c) Forming 3: The temperature of the MEA chamber 7 is kept at the binding temperature. Then a pressing plate 74 having a convex part 741 is correspondingly pressed into the hollow 741 of the template 74 to obtain a first CEL 81 on a surface of the PEM 73.
(d) Changing side 4: After the first CEL 81 is obtained on the surface of the PEM 73, the MEA chamber 7 is cooled down; the ventilation effect of the vacuum facility 71 is stopped; and the template 74 is taken out and the PEM 73 is turned over. The ventilation effect of the vacuum facility 71 is activated again to fix the PEM 73 on the suction plate 72, and then the template 74 is deposed on another surface of the PEM 73.
(e) Inputting material again 5: A slurry of anode or cathode catalyst material 8,8a is poured into the hollow 741 of the template 74 again. The temperature-controllable heater 721 in the vacuum facility 71 is activated to heat the suction plate, to raise a temperature to bind the slurry of anode or cathode catalyst material 8,8a and the PEM 73. (If the binding is processed in a room temperature, the temperature is not raised.)
(f) Forming again 6: The temperature of the MEA chamber 7 is kept at the binding temperature. Then the pressing plate 74 having the convex part 741 is correspondingly pressed into the hollow 741 of the template 74 to obtain a second CEL (CEL′) 82 on a surface of the PEM 73. Thus, a MEA having three layers (MEA-3-layer) of CEL 81+PEM 73+CEL′ 82 is obtained.
If gas diffusion layers (GDL and GDL′) are added separately before two times of pressing by the pressing plate 74, a MEA having five layers (MEA-5-layer) of GDL+CEL 81+PEM 73+CEL′ 82+GDL′ is obtained. The GDL is made of a conductive-carbon-contained fabric, a non-woven fabric or a carbon paper.
For defining the first CEL 81 or the second CEL′ 82 as an anode or a cathode, a slurry of anode or cathode catalyst material 8,8a is poured in steps of inputting a material 2 and inputting the material again 5. If the first CEL 81 or the second CEL′ 82 is to be defined as an anode, a slurry of anode catalyst material 8 is used, which is a mixture of a Pt/Ru/C carrier and a Nafion solution. If the first CEL or the second CEL′ 82 is to be defined as a cathode, a slurry of cathode catalyst material 8a is used, which is a mixture of a Pt/C carrier and a Nafion solution.
For obtaining a thickness of the first CEL 81 or the second CEL′ 82, the depth for the convex part 751 of the pressing plate 75 to be correspondingly pressed into the hollow 741 of the template 74 is controlled to obtain the thickness of the first CEL 81 or the second CEL′ 82.
To sum up, the present invention is a method for fabricating a membrane electrode assembly, where two flat CELs are formed on two surfaces of a PEM separately and a thickness of CEL on the MEA is under control.
The preferred embodiment herein disclosed is not intended to unnecessarily limit the scope of the invention. Therefore, simple modifications or variations belonging to the equivalent of the scope of the claims and the instructions disclosed herein for a patent are all within the scope of the present invention.
