Attribution of H+ Transportation of Nafion-Film on Different Substrates Using Planar Inter-Digitated Electrodes

Abstract

In-plane proton transport property of Nafion thin-film on carbon and quartz was investigated in N2 environment by electrochemical impedance spectroscopy (EIS) using interdigitated electrodes (IDEs) of platinum on quartz substrate. The Pt IDEs with and without carbon pad were fabricated with precise geometry and excellent current-voltage (I-V) response in few hundreds femtoampere (fA). The morphology of spin-coated Nafion thin-film over IDEs was confirmed to adapt the geometry of IDE structure. The EIS impedance response of Nafion thin-film consists of single semi-circular component in either IDEs. Since Pt-C IDE has both ionomer/quartz and ionomer/carbon interface therefore H+ conductivity at quartz and carbon was estimated from the quantitative attribution of H+ transport resistance. The estimated H+ conductivity at quartz from Pt-C IDE and Pt-Q IDE shows comparable conductivity values except the high relative humidity (RH) and indicates that H+ transport resistance at carbon substrate in Pt-C IDE is absent in N2 environment.