Fuel Cells

Abstract

A fuel cell. A membrane electrode assembly includes a proton exchange membrane, a cathode electrode, and an anode electrode. The proton exchange membrane is disposed between the cathode and anode electrodes. A cathode porous current collector is disposed on the cathode electrode. An anode porous current collector is disposed on the anode electrode and opposite the cathode porous current collector. A cathode water-absorptive layer is disposed on the cathode porous current collector, absorbing or guiding water at the cathode electrode.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

The invention can be more fully understood by reading the subsequent detailed description and examples with references made to the accompanying drawings, wherein:

FIG. 1 is a schematic cross section of a conventional monopolar fuel cell;

FIG. 2 is a schematic cross section of a fuel cell of a first embodiment of the invention;

FIG. 3 is a schematic cross section of a fuel cell of a second embodiment of the invention; and

FIG. 4 is a schematic partial cross section of a fuel cell of a third embodiment of the invention.

DETAILED DESCRIPTION OF THE INVENTION

The following description is of the best-contemplated mode of carrying out the invention. This description is made for the purpose of illustrating the general principles of the invention and should not be taken in a limiting sense. The scope of the invention is best determined by reference to the appended claims.

Referring to FIG. 2, a fuel cell 100 comprises a membrane electrode assembly 110, a cathode porous current collector 120, an anode porous current collector 130, a cathode water-absorptive layer 140, and a frame 150. The frame 150 fixes the membrane electrode assembly 110.

The membrane electrode assembly 110 comprises a proton exchange membrane 111, a cathode electrode 112, and an anode electrode 113. The proton exchange membrane 111 is disposed between the cathode electrode 112 and the anode electrode 113. Specifically, the cathode electrode 112 comprises a cathode catalyst layer 112a and a cathode gas diffusion layer 112b, and the anode electrode 113 comprises an anode catalyst layer 113a and an anode gas diffusion layer 113b. The proton exchange membrane 111 is disposed between the cathode catalyst layer 112a and the anode catalyst layer 113a. The cathode gas diffusion layer 112b is disposed on the cathode catalyst layer 112a. The anode gas diffusion layer 113b is disposed on the anode catalyst layer 113a.

The cathode porous current collector 120 is disposed on the cathode electrode 112. Specifically, the cathode porous current collector 120 is disposed on the cathode gas diffusion layer 112b of the cathode electrode 112.

The anode porous current collector 130 is disposed on the anode electrode 113. Specifically, the anode porous current collector 130 is disposed on the anode gas diffusion layer 113b of the anode electrode 113 and opposite the cathode porous current collector 120.

The cathode water-absorptive layer 140 is disposed on the cathode porous current collector 120. Compared to the cathode porous current collector 120, the cathode water-absorptive layer 140 is hydrophilic and can rapidly absorb water or guide water to other areas, preventing the water from being accumulated at the cathode porous current collector 120 or cathode electrode 112. The cathode water-absorptive layer 140 may comprise porous hydrophilic material, such as a hydrophilic thread, a lampwick, woven fabrics, non-woven fabrics, paper, foam sponge, or foaming PU. The porous hydrophilic material, such as foaming PU, may be directly attached to the cathode porous current collector 120 by coating. Specifically, disposed in the exterior of the cathode porous current collector 120, the cathode water-absorptive layer 140 does not adversely affect electrical contact between the cathode porous current collector 120 and the cathode gas diffusion layer 112b. Thus, the total resistance in the fuel cell 100 is not increased. Moreover, the cathode water-absorptive layer 140 is provided with sufficient capillary surface area. Small size and a large amount of capillary surface are preferred. To effectively promote permeability of air, the size of the capillary surface or through holes is determined by surface energy provided by the cathode water-absorptive layer 140 without formation of any water film, such that oxygen can easily enter the cathode electrode 112. Specifically, the radius of the capillary surface or through holes must exceed the thickness of the cathode water-absorptive layer 140, such that water droplets on the edges thereof do not connect to each other and form water films to clog up the capillary surface or through holes.

Second Embodiment

Elements corresponding to those in the first embodiment share the same reference numerals.

Referring to FIG. 3, in this embodiment, the cathode porous current collector 120 of the fuel cell 100′ is pressed and fixed by a press board 121 with high rigidity, such that contact resistance between the cathode porous current collector 120 and the cathode gas diffusion layer 112b is reduced. The cathode water-absorptive layer 140 is disposed on the press board 121, enhancing contact of the cathode water-absorptive layer 140 and the water at the cathode electrode 112. Moreover, the press board 121 may comprise porous hydrophilic material, absorbing or removing the excess water from the cathode electrode 112.

Structure, disposition, and function of other elements in the fuel cell 100′ are the same as those in the fuel cell 100, and explanation thereof is omitted for simplicity.

Third Embodiment

Elements corresponding to those in the first embodiment share the same reference numerals.

Referring to FIG. 4, in this embodiment, the cathode water-absorptive layer 140 of the fuel cell 100″ guides the water produced at the cathode electrode 112 to a water storage 160 by capillarity or gravity. The water storage 160 may comprise water-absorptive material (such as foam sponge) or be a tank, storing the water from the cathode electrode 112. Additionally, a fluid transportation device 170, such as a pump or a compressor, is connected to the water storage 160. The fluid transportation device 170 transports the water stored in the water storage 160 to the anode electrode 113 or a recycling area (not shown) within a proper or predetermined time period, mixing with methanol. For example, when the water storage 160 is higher than the anode electrode 113, the fluid transportation device 170 may be an electromagnetic valve, a one-way valve, or a guide pipe. The water in the water storage 160 flows to the anode electrode 113 by gravity and is applied thereby.

Structure, disposition, and function of other elements in the fuel cell 100″ are the same as those in the fuel cell 100, and explanation thereof is omitted for simplicity.

Accordingly, in the fuel cell 100″, the excess water at the cathode electrode 112 and adversely affecting the redox reaction is effectively recycled or transported to the anode electrode 113 for reaction. Thus, the fuel cell 100″ can provide long-term operation.

While the invention has been described by way of example and in terms of preferred embodiment, it is to be understood that the invention is not limited thereto. To the contrary, it is intended to cover various modifications and similar arrangements (as would be apparent to those skilled in the art). Therefore, the scope of the appended claims should be accorded the broadest interpretation so as to encompass all such modifications and similar arrangements.

Claims

1. A fuel cell, comprising: a membrane electrode assembly comprising a proton exchange membrane, a cathode electrode, and an anode electrode, wherein the proton exchange membrane is disposed between the cathode and anode electrodes;a cathode porous current collector disposed on the cathode electrode;an anode porous current collector disposed on the anode electrode and opposite the cathode porous current collector; anda cathode water-absorptive layer disposed on the cathode porous current collector, absorbing or guiding water at the cathode electrode.

2. The fuel cell as claimed in claim 1, wherein the cathode water-absorptive layer comprises porous hydrophilic material.

3. The fuel cell as claimed in claim 2, wherein the porous hydrophilic material comprises a hydrophilic thread, a lampwick, woven fabrics, non-woven fabrics, paper, foam sponge, or foaming PU.

4. The fuel cell as claimed in claim 1, wherein the cathode water-absorptive layer is coated or printed on the cathode porous current collector.

5. The fuel cell as claimed in claim 1, further comprising a press board disposed on the cathode porous current collector, fixing the cathode porous current collector.

6. The fuel cell as claimed in claim 5, wherein the cathode water-absorptive layer is disposed on the press board.

7. The fuel cell as claimed in claim 5, wherein the press board comprises porous hydrophilic material.

8. The fuel cell as claimed in claim 1, further comprising a water storage connected to the cathode water-absorptive layer, wherein water at the cathode electrode is guided to the water storage from the cathode water-absorptive layer.