ABSTRACT: Mid-December 2014 is set to be the historical launch of the first commercial fuel-cell vehicle, heralding a transition from fossil-fueled vehicles to cleaner hydrogen-fed vehicles. Despite this significant milestone in making, there is an aggressive approach for further reduction in the cost of the polymer electrolyte fuel cell (PEFC) stacks while maintaining/ improving its electrochemical performance.
Both the cost and the performance of PEFCs are tightly linked to its catalyst layer, which is a porous composite of ion-conducting polymer (e.g. Nafion) and precious platinum catalyst supported on carbon (Pt/C). The ionomer in the conventional PEFC catalyst layer exists as an ultra-thin film coating the Pt/C aggregates. The thickness of these films is arguably 10 nm of less. The primary functionalty of the ionomer is to transport protons to the catalyst site. However, as a polymer film covering the catalyst, it also acts as a barrier to the transport of oxygen and hydrogen in the cathode and anode, respectively. The characteristics of such confined ionomer films is not fully understood. We have an ongoing research program to unravel the structure and properties of ultra-thin Nafion films. The talk will focus largely on self-assembled, 4-300nm thick Nafion films on planar substrates. The presentation will discuss the characterization of the structure and transport properties of these films by various techniques including atomic force microscopy (AFM), ellipsometry, grazing incidence small angle x-ray scattering (GISAXS), contact angle, impedance spectroscopy, and proton NMR.
Bio-sketch: Dr. Karan is currently an Associate Professor of Chemical and Petroleum Engineering at the University of Calgary, Canada. Previously, he was at Queen’s University, Kingston, Canada where he co-founded the Queen’s-RMC Fuel Cell Research Centre serving as its Associate Director. Dr. Karan’s core research interest is in unraveling of the fundamental understanding of nano-/micro-scale reaction-transport phenomena in fuel cell electrodes. He has made notable contributions in PEFC catalyst layer models and a significant focus of his current research is on the nano-scale structure-property of ultra-thin ionomer films. Dr. Karan has authored/co-authored 65 peer-reviewed journal publications and has 2 patents to his record. He has delivered plenary and keynote lectures at international conferences and at prominent academic and industrial research groups. In recognition of his past contributions and promising research, he received The Early Researcher’s Award from the province of Ontario.