Effect of idling temperature on high temperature polymer electrolyte membrane fuel cell degradation under simulated start/stop cycling conditions

Start/stop cycling are dynamic durability tests designed to simulate the fuel cell system shut-down and restarting that occurs in actual system operation. In the present work, commercial PBI-based MEAs were evaluated in a start/stop cycling test designed for combined heat and power application. Moreover, the start/stop cycling strategy has not been conducted under protective conditions that mitigate degradation of fuel cell materials over cycles. Instead, start/stop of the fuel cell has been conducted on a daily basis until completing 60 cycles or reaching end-of-life. Two idling temperatures after shutdown have been investigated: 25 and 100 degrees C. Thus, the effect of idling temperature has never been studied before in this fuel cell technology. Polarization curves, electrochemical impedance spectroscopy, cyclic, linear sweep voltammetry and mu-CT were utilized for MEA characterization. It was observed that system temperature during idling periods played an important role for HT-PEM MEAs lifetime. The test performed at the highest idling temperature exhibited larger degradation (-57 mu V/h or -2.4 mV/cycle) than that at lower idling temperature (-13 mu V/h or 0.6 mV/cycle). Thus, it was found that performance was mainly reduced due to catalyst deactivation and increased mass transfer limitations. Besides, electrochemical investigations showed both anode and cathode catalyst deterioration and mu-CT images also confirmed anode catalyst layer local thinning. (C) 2016 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.