ION EXCHANGE MEMBRANE

Abstract

Disclosed is a cell comprising an anode, a cathode and a membrane located between the anode and the cathode, wherein the membrane comprises an aqueous medium and a film comprising amyloid fibers. The invention further relates to said film, stacks of said cells, an electrolyte membrane, and the use of these various devices.

Claims

1. A fuel cell comprising: an anode; a cathode; and a membrane located between the anode and the cathode, said membrane comprising an aqueous liquid and a film comprising amyloid fibers.

2. The fuel cell according to claim 1, wherein said membrane is a proton exchange membrane.

3. The fuel cell according to claim 1, wherein said film has a thickness chosen from a range varying from 10 nm to 1 mm.

4. The fuel cell according to claim 1, wherein the amyloid fibers comprise, or consist of, at least one protein such as α-lactalbumin or lysozyme.

5. The fuel cell according to claim 1, wherein said film further comprises an additive selected from the group consisting of ions, plasticizers, and crosslinking agents.

6. The fuel cell according to claim 1, wherein said cell further comprises two plates: a first plate for distributing a reducing fuel, for example dihydrogen, and a second plate for distributing the oxidant and, possibly, for discharging the water.

7. (canceled)

8. (canceled)

9. A fuel cell comprising a stack of at least two fuel cells as described in claim 1.

10. (canceled)

11. An electrical device comprising a fuel cell described in claim 1.

12. A method of manufacturing a film or membrane based on amyloid fibers, comprising forming a gel of amyloid fibers, and spreading and drying the gel so as to form said film or said membrane.

13. The method according to claim 12, wherein said gel of amyloid fibers is formed by contacting protein(s) and/or polypeptides with water under conditions allowing formation of amyloid fibers.

14. The method according to claim 13, wherein said protein is α-lactalbumin or lysozyme.

15. The fuel cell according to claim 5, wherein the crosslinking agents are selected from glutaraldehyde, antioxidants, radical traps, or UV stabilizers.

16. An electrical device comprising a fuel cell described in claim 9.

17. The method of claim 12, wherein the gel is spread and dried on a solid support.

Description

BRIEF DESCRIPTION OF THE FIGURES

[0047] The invention will be better understood upon reading the description which follows, given solely by way of example and with reference to the appended drawings in which:

[0048] FIG. 1 is a schematic and partial representation of the PEMFC-type cells of Examples 3 (example according to the invention) and 5 (comparative example).

[0049] FIG. 2 shows the polarization and power curves for a PEMFC based on a conventional membrane from Nafion™ and a PEMFC based on a membrane based on α-lactalbumin (α-LAC).

[0050] FIG. 3 shows the polarization curves and power curve for a PEMFC based on an α-lactalbumin (α-LAC) membrane and for a PEMFC based on a 95/5 lysozyme/methylcellulose membrane.

EXAMPLES OF IMPLEMENTATION

Example 1: Production of a Film Based on α-Lactalbumin According to the Invention

[0051] The α-lactalbumin (of bovine origin, CAS number 9051-29-0) was obtained from the company DAVISCO (US) with a purity greater than 90%. These proteins were diluted at a rate of 40 g/L in an aqueous solution of 50 mM hydrochloric acid HCl, to obtain a final pH equal to 2. This suspension was incubated for several days (typically 3 days) at 45° C. with moderate agitation until amyloid fiber formation, which is manifested in the case of α-lactalbumin by the formation of a thixotropic hydrogel. The presence of amyloid fibers was verified by electron microscopy. 0.8 g of the solution was poured dropwise onto a support made of glass fibers coated with PTFE (Techniflon 208 A, 80 μm thick, 53% PTFE by mass, 107 g/m.sup.2). Drying was carried out at room temperature in air for 24 hours to form a self-supporting film (20 μm thick).

Example 2: Production of a Lysozyme-Based Film According to the Invention

[0052] Lysozyme (avian origin, CAS number 12650-88-3) from chicken egg white was obtained from Sigma-Aldrich (ref. L-6876) with a purity of approximately 95%. These proteins were diluted at a rate of 40 g/L in an aqueous solution of hydrochloric acid HCl for a final pH of 2.7 containing 90 mM of NaCl. This suspension was incubated for several days (typically 3 days) at 60° C. with moderate agitation until amyloid fiber formation, which is manifested in the case of lysozyme by the formation of a hydrogel. The presence of amyloid fibers was verified by electron microscopy. In this example, 5% by mass of a methylcellulose solution in HCl (pH 3) is added to the lysozyme solution in order to improve the mechanical properties (stability, elasticity) of the film obtained after drying.

[0053] 0.8 g of the solution was poured dropwise onto a support made of glass fibers coated with PTFE (Techniflon 208 A, 80 μm thick, 53% PTFE by mass, 107 g/m.sup.2). Drying was carried out at room temperature in air for 24 hours to form a self-supporting film (20 μm thick).

Example 3: Production of Fuel Cells

[0054] Cells according to the invention were each produced with the membranes of Examples 1 and 2. For each cell, a membrane 30 was detached from its respective support and was positioned between two electrodes 20 of a conventional test fuel cell (hydrogen) from the company Paxitech (France). In summary, a hydrogen/air fuel cell having 5 cm.sup.2 of active surface.

[0055] Commercial gas diffusion electrodes are placed on a Sigracet 29 BC brand gas diffusion layer (purchased from Fuelcellstore (USA)). It is a non-woven carbon paper with a microporous layer (MPL) treated with 5% by weight PTFE. It has a total thickness of 235 μm (microns). The electrodes thus comprise a 0.5 mg.Math.cm.sup.−2 platinum charge on a carbon powder support of the Vulcan type deposited on carbon fiber paper (Sigracet 29BC).

[0056] The electrodes themselves are positioned on outer graphite plates 10 machined with a serpentine gas flow. That is, the active surface comprises a serpentine shaped recess 1 mm wide by 1 mm deep (not shown).

[0057] PTFE gaskets and sub-gaskets are used to prevent gas leakage and to ensure adequate electrical insulation.

Example 4: Battery Performance According to the Invention

[0058] In operation, the hydrogen (H.sub.2) enters through the plate 10 on the left in FIG. 1. Once it has arrived at the anode, the hydrogen dissociates (oxidation) in H.sup.+ ions and in electrons according to: 2H.sup.2=4H.sup.++4e.sup.−. The ions then pass through the membrane 30, but the electrons, blocked, are forced to take the external circuit, which generates current. At the cathode, the hydrogen ions, electrons and oxygen (pure or from air) meet to form water according to the reaction: 4H.sup.++4e.sup.−+O.sub.2=2H.sub.2O. The water and oxygen pass through the right plate 10. This reaction will also produce heat that can be recovered.

[0059] FIG. 3 shows the polarization and power curves that were obtained by galvanostatic discharges of 30 s at room temperature under atmospheric pressure with humidified gases (minimum relative humidity of 60% RH) (H.sub.2 and air) with respective flow rates of 20 mL min-1 for a membrane based on lysozyme and α-lactalbumin.

[0060] These results show that a membrane comprising a film of amyloid fibers is also a good proton conductor. The lysozyme-based membrane compared to α-lactalbumin leads to slightly lower performance (7 mW cm.sup.−2 at 0.4 V). Polarization curves and power curve for a PEMFC based on an α-lactalbumin (α-LAC) membrane and for a PEMFC based on a 95/5 lysozyme/methylcellulose membrane. The discharges were carried out at 1 atm in H.sub.2 and air at a humidity level of 60%.

Comparative Example 5: Production of a Cell with Nafion™ Membrane

[0061] To demonstrate the advantages of the membranes according to the invention, comparative tests were carried out. The only difference between the devices is the use of a membrane 30 with the following characteristics (DUPONT Nafion™ NRE212, thickness 50 μm—CAS No. 31175-20-9) instead of a membrane (30) according to the invention. The tests were carried out under conditions identical to those described above except that the discharges were carried out at a humidity level of 100% and not of 60%.

[0062] FIG. 2 shows the polarization curve (black) and the power curve (blue) the PEMFC batteries based on a conventional membrane made from Nafion™ and a PEMFC based on an α-lactalbumin (α-LAC). The discharges were carried out at 1 atm in H.sub.2 and air at a humidity level of 60% for α-lactalbumin and 100% for Nafion™.

[0063] The performances obtained at 25° C. (22 mW cm-2 at 0.4 V) show that the α-LAC-based membrane is an excellent proton conductor and is able to approach the performance of Nafion™ (32 mW cm-2 at 0.4 V) under these conditions (25° C., RH 60%).

Example 6: Production of a Crosslinked Film Based on α-Lactalbumin and Glutaraldehyde According to the Invention

[0064] The self-supported protein membranes were also subjected to a chemical crosslinking step in the presence of glutaraldehyde vapor (Supplier Sigma-Aldrich, 50% (by mass) in water). The protein film of Example 1, once dried, is subjected to glutaraldehyde vapors for 30 min at 25° C.

[0065] This crosslinking step allows the self-supported film to be resistant in solution in water at acidic pH (tested pH=3) and up to 80° C. In PEMFC operation, this step therefore allows the cell to operate over a wide temperature range. Its temperature resistance goes from 35° C., without chemical crosslinking, to at least 60° C. after chemical crosslinking, or even more. In addition, a PEMFC comprising such a membrane does not lose its performance after several days of operation.

[0066] The invention is not limited to the embodiments described here, and other embodiments will become clearly apparent to a person skilled in the art. It is in particular possible to consider the use of peptides capable of forming amyloid fibers that organize themselves into hydrogels. It is also possible to use the membranes according to the invention on any type of PEMFC. It can be used not only for hydrogen fuel cells, but also direct methanol fuel cells (DMFC).