(638b) Altering the Interfacial Chemical Makeup to Manipulate the Distribution of Ion Conduction Environment across Ionomeric Materials

The behavior of ionomers in a bulk membrane separator and a catalyst binder layer of an electrochemical device can be drastically different. This is because ion conduction and other behaviors of sub-micron thick ionomer films are dominated by a range of interfacial phenomena. We have developed a fluorescence confocal laser scanning microscopy (CLSM)-based technique to unravel the distribution of ion conduction environment across ionomeric thin-to-thick materials. What we saw is that a weakly proton-conducting zone can propagate up to half the thickness of the ionomer film starting from the substrate interface. This suppressed ion transport was primarily attributed to interfacial chain orientation and multimodal interactions. We then became more interested to see what happens if the interfacial composition and ionomer chain orientation were altered in a controlled manner. We adopted surface chemistry approaches to alter the chemical structure of the interfaces and explored its effect on the distribution of the ion conduction environment from the substrate to the air interface using CLSM and other complementary techniques. Such approaches can critically contribute to the future design of catalyst-ionomer interfaces to deal with both ion and mass transport limitations in fuel cell electrodes.