METHOD AND APPARATUS FOR THE PRODUCTION OF AN ION-CONDUCTING MEMBRANE

1 . A method for the production of an ion-conducting membrane for a water electrolyser or a fuel cell, the ion-conducting membrane comprising at least one membrane layer, the method comprising the steps of:

(a) mixing a first liquid stream comprising an ion-conducting polymer and a second liquid stream comprising a cerium-containing compound in-line to form a coating composition; and

(b) depositing the coating composition onto a substrate to form a membrane layer.

2 . A method according to claim 1 , wherein the first liquid stream comprises a dispersion of an ion-conducting polymer in a mixture of water and a polar solvent other than water.

3 . A method according to claim 1 , wherein the second liquid stream comprises the cerium-containing compound in the form of a colloidal sol.

4 . A method according to claim 1 , wherein the cerium-containing compound is a doped or undoped oxide of cerium.

5 . A method according claim 1 , wherein the substrate is selected from a backing sheet, a second membrane layer, or a catalyst layer on a backing sheet.

6 . A method according to claim 1 , wherein the in-line mixing in step (a) is carried out using a using a static mixer.

7 . A method according to claim 1 , wherein ratio of the flow rate of the first liquid stream to the flow rate of the second liquid stream is in the range of and including 7:1 to 15:1.

8 . A method according to claim 1 , further comprising step (c) drying the membrane layer.

9 . A method according to claim 1 , further comprising the steps:

(d) depositing the coating composition onto the membrane layer to form an additional membrane layer; and

(e) drying the additional membrane layer.

10 . A method according to claim 9 , wherein steps (d) and (e) are repeated between 1 and 6 times.

11 . A method according to claim 1 wherein the ion-conducting membrane is a proton-exchange membrane.

12 . A method of manufacturing a catalyst-coated membrane, the method comprising the steps of:

(i) providing an ion-conducting membrane produced according to claim 1 , the membrane comprising a first face and a second face; and

(ii) forming a catalyst layer on the first and/or the second face of the membrane.

13 . A method according to claim 12 further comprising the step of applying a seal material to the first face and/or the second face of the catalyst-coated membrane.

14 . A method according to claim 12 further comprising the step of applying a gas diffusion layer and/or a porous transport layer onto the first and/or second faces of the catalyst-coated membrane.

15 . An apparatus for the production of an ion-conducting membrane for a fuel cell or an electrolyser, the apparatus comprising:

(i) a first source for providing a first liquid stream comprising an ion-conducting polymer;

(ii) a second source for providing a second liquid stream comprising a cerium-containing compound;

(iii) an in-line mixing device which is in fluid communication with the first source and the second source, the in-line mixing device configured to mix the first liquid steam and the second liquid stream to form a coating composition; and

(iv) a coating apparatus configured to receive the coating composition from the in-line mixing device and to coat a substrate with the coating composition to form an ion-conducting membrane layer.

16 . An apparatus according to claim 15 , wherein the in-line mixing device is a static mixer.

17 . An apparatus according to claim 15 , wherein the coating apparatus is a slot-die coater, a bar coater, an inkjet printer or a gravure printer.

18 . An apparatus according to claim 15 , further comprising an analytical device for the analysis of the cerium content in the membrane layer as the membrane layer is produced.

19 . An apparatus according to claim 18 wherein the apparatus is configured such that the flow rate of the second liquid stream is adjusted automatically based on the cerium content detected in the membrane layer by the analytical device.

20 . An apparatus according to claim 15 , wherein the apparatus is configured such that the transit time of the coating composition between the outlet of the in-line mixing device and the inlet of the coating apparatus is less than 60 seconds, such as less than 30 seconds, or less than 10 seconds.