Effects of Cathode Inlet Relative Humidity on PEMFC Durability during Startup-Shutdown Cycling I. Electrochemical Study

This work investigated the effect of cathode inlet relative humidity (RH) on the durability of proton exchange membrane fuel cells (PEMFCs) during startup-shutdown cycling via single-cell experiments. Electrochemical techniques, including measurements of polarization curves, electrochemical impedance spectroscopy (EIS), cyclic voltammetry (CV), and linear sweep voltammetry, were performed to examine the effect of cathode inlet RH on the degradation of PEMFCs. The performance was better for PEMFCs cycled at a lower cathode inlet RH than for those cycled at a higher cathode inlet RH on the order of 0 > 50 > 100%. The CV and EIS results showed that as the cathode inlet RH increased, the loss of electrochemically active surface area and the increase in the charge-transfer resistance (R(ct)) were faster during the startup-shutdown cycling. However, changes in ohmic resistance (R(ohm)) and hydrogen crossover current density were not detectable, revealing that severe membrane degradation did not occur regardless of the cathode inlet RH during startup-shutdown cycles. (C) 2009 The Electrochemical Society. [DOI:10.1149/1.3254170] All rights reserved.