External Reinforcement of Hydrocarbon Membrane By Combining Toughened Catalyst Layers and Interlocking Interfaces for High Mechanical Robustness of PEMFC

Abstract

For decades, in polymer electrolyte membrane fuel cell (PEMFC) field, hydrocarbon (HC) membranes have been constantly studied to replace perfluorinated sulfonic acid membranes owing to their low cost and high fuel efficiency. However, adopting HC membranes to practical PEMFCs has been not successful due to their poor mechanical stability which causes a mechanical failure with generating pin-hole under repeated volume expansion/shrinkage during cell operation. Conventionally, the problem has been addressed by inserting a porous mechanical supporter in HC membrane which is denoted as ‘internal reinforcement’. However, the introduction of the inert support decreases proton conduction and increases membrane cost. Here we present an external reinforcement of HC membrane as a new strategy to enhance mechanical durability of HC membrane. It features the incorporation of mechanically tough porous fibrous network into catalyst layers and the strong connection of HC membrane and the toughened catalyst layers with introducing an interlocking interface. The mechanically toughened catalyst layers and interfaces can effectively mitigate the volume change of HC membrane, lowing the membrane failure. Under an accelerated humidity cycling test, the externally reinforced HC membrane exhibits an enhanced durability compared to un-reinforced counterpart. Furthermore, contrary to the internal reinforcement, the external reinforcement strategy does not cause any loss of proton conductivity of HC membrane. Therefore, the external reinforcement coupled with toughed catalyst layers and interfaces can provide an effective way to enhance durability with preserving the proton conductivity of pristine HC membrane.