1 The Ionic Conductivity and Catalyst Activity Effects of Acetonitrile on Proton Exchange Membrane Fuel Cells Yunfeng Zhai  , Junjie Ge a and Jean St-Pierre Hawaii Natural Energy Institute, University of Hawaii – Manoa, Honolulu, Hawaii 96822, USA Abstract The effect of trace levels of acetonitrile, an airborne pollutant, on proton exchange membrane fuel cells (PEMFCs) membrane/electrode assemblies (MEAs) was investigated in situ and ex situ using electrochemical impedance spectroscopy, cyclic voltammetry and polarization with a fuel cell and a membrane conductivity cell. In situ test results indicate that acetonitrile depresses electrode activity and decreases MEA ionic conductivity. Ex situ tests demonstrate that acetonitrile does not affect the membrane ionic conductivity, indicating the role for an acetonitrile reduction product (ammonium cation). Keywords: PEMFC, Contaminants, Acetonitrile, Oxygen reduction, Ionic conductivity. 1. Introduction Fuel cell vehicles are currently being deployed (Toyota Mirai, etc). However, the risks associated with air pollution have not yet been eliminated or minimized. Pollutants adversely impact cell performance and durability. Most of the 200 airborne pollutants that have been identified are volatile organic compounds (VOCs), and most have not been characterized [1-2] for their effect on air filter effectiveness and cell performance. Such conditions extend to real-life operations. The effects of duty cycling and contaminant mixtures [3] on fuel cell stacks [4] have  Corresponding author: 1680 East West Road, POST 109, Honolulu, HI 96822, USA; Email: yunfeng@hawaii.edu a Currently at Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun, Jilin 130022, China. © 2016. This manuscript version is made available under the Elsevier user license http://www.elsevier.com/open-access/userlicense/1.0/