A Study on Structural Property of Ionomer as a Model for Catalyst Layer: Relationship between Thickness and Proton Conduction for Ionomer Thin Film on Different Substrate

To study the property of proton conduction for electrolyte thin film inside catalyst layer, model ionomer thin films were prepared on different surfaces such as carbon and platinum substrates. An atomic force microscopy coupled with electrochemical technique (e-AFM) demonstrated that proton conduction reduced with film thickness, and abruptly decreased when film thickness was less than 10 nm for both carbon and platinum substrate. This indicates that number of active proton conductive pathway and/or connectivity of proton path network change with film thickness, and is though that the morphology of thin film is essentially different from that of a bulk membrane.