MEMBRANE ELECTRODE ASSEMBLY FOR USE IN ELECTROCHEMICAL DEVICES

摘要

The invention relates to a membrane electrode assembly (MEA) for use in electrochemical devices, especially membrane fuel cells. Said membrane electrode assembly has a semi-coextensive design and comprises an ion-conducting membrane, two catalyst layers, and differently sized gas diffuser substrates on the front and back. The first gas diffuser substrate covers a smaller two-dimensional area then the ion-conducting membrane while the second gas diffuser substrate has substantially the same area as the ion-conducting membrane, thereby leaving the ion-conducting membrane with a front surface that is not supported by a gas diffuser substrate. Due to its specific design, the membrane electrode assembly has a stable, easy-to-handle structure, has good electrical properties and is advantageous in sealing the reactive gases from each other. In particular, the invention allows for a substantial reduction of hydrogen permeation currents. The invention also relates to novel methods for producing the inventive MEAs, especially heat-pulse welding methods. The membrane electrode assembly is used in PEM fuel cells, direct methanol fuel cells, electrolyzers and other electrochemical devices.