The Effect of Start/Stop Strategy on PEM Fuel Cell Degradation Characteristics

Abstract

Fuel cells hold the ability to fulfill the objectives of an energy production that is effective, virtually free from green house gas emissions and independent from locally existing raw materials. The most promising type of fuel cell for lightweight vehicles and small scale energy production is the PEM fuel cell, due to its short start-up times and low operating temperatures. The development in the last decade has enabled satisfying power limits of the PEM fuel cell, which has resulted in an aim to reduce the price and receive a prolonged durability. Conditions during start and stop events result in a severe degradation of the fuel cell, which makes strategies to mitigate the impact important. Two protective strategies have been developed and evaluated, one for start-up and one for shutdown. The strategy tests were performed in laboratory where the fuel cells were subjected to repetitive start/stop cycles. The performance reduction was measured at 0.5 A/cm² for each cycle and the degradation was analysed with electrochemical in situ methods. The start-up strategy resulted in a potential loss, at 0.5 A/cm², of 69.7 µV/cycle. The corresponding potential loss for the shutdown strategy was 92.5 µV/cycle. The degradation analysis showed that the electrochemically active platinum surface area was reduced after the preformed cycles, for both of the strategies.