Proton-conducting polymer membrane comprising sulfonic acid-containing polyazoles, and use thereof in fuel cells

An electrode having a proton-conducting polymer coating which is based on polyazoles and is obtainable by a process comprising the steps:

• A) mixing one or more aromatic or heteroaromatic tetraamino compounds with one or more aromatic or heteroaromatic carboxylic compounds in polyphosphoric acid to form a solution or dispersion, wherein the carboxylic compounds contain at least two groups selected from acids, esters, acid halides or acid anhydrides, with at least part of the tetraamino compounds or the carboxylic compounds comprising at least one phosphonic acid group;
• or
• mixing one or more aromatic or heteroaromatic diaminocarboxylic compounds in polyphosphoric acid to form a solution or dispersion, wherein the diaminocarboxylic compounds contain a group selected from acids and esters, wherein at least a part of said diaminocarboxylic compounds comprises sulfonic acid groups;
• B) heating the solution or dispersion obtained according to step A) under inert gas to temperatures of up to 350° C. to form polyazole polymer;
• and
• C) applying a layer using the mixture from step B) to an electrode, thus forming a membrane on the electrode;
• or
• D) applying the solution or dispersion from step A) to an electrode, thus forming a membrane on the electrode;
• and
• E) heating the membrane formed in step D) under inert gas to temperatures of up to 325° C. to form polyazole polymers;
• and
• F) partially hydrolyzing the polyphosphoric acid moieties of the electrode membrane formed in step C) or step E),
• wherein the concentration of phosphoric acid in the membrane of step (F) is from 10 to 80 mols of phosphoric acid per mol of a repeating unit of the polyazole polymer.

A membrane-electrode unit comprising at least one electrode having a proton-conducting polymer coating which is based on polyazoles and is prepared by the following steps:

• A) mixing one or more aromatic or heteroaromatic tetraamino compounds with one or more aromatic or heteroaromatic carboxylic compounds in polyphosphoric acid to form a solution or dispersion, wherein the carboxylic compounds contain at least two groups selected from acids, esters, acid halides or acid anhydrides, with at least part of the tetraamino compounds or the carboxylic compounds comprising at least one sulfonic acid group;
• or
• mixing one or more aromatic or heteroaromatic diaminocarboxylic compounds in polyphosphoric acid to form a solution or dispersion, wherein the diaminocarboxylic compounds contain a group selected from acids and esters, wherein at least a part of said diaminocarboxylic compounds comprises sulfonic acid groups;
• B) heating the solution or dispersion obtained according to step A) under inert gas to temperatures of up to 350° C. to form polyazole polymer;
• C) applying a layer using the mixture from step B) to an electrode, thus forming a membrane on the electrode;
• or
• D) applying a solution or dispersion from step A) to an electrode, thus forming a membrane on the electrode;
• and
• E) heating the membrane formed in step D) under inert gas to temperatures of up to 325° C. to form polyazole polymers;
• and
• F) partially hydrolyzing the polyphosphoric acid moieties of the electrode membrane formed in step C) or step E) until the membrane is self-supporting,
• wherein the concentration of phosphoric acid in the membrane of step (F) is from 10 to 80 mols of phosphoric acid per mol of a repeating unit of the polyazole polymer.