A Novel Accelerated Stress Test for a Representative Enhancement of Cathode Degradation in Direct Methanol Fuel Cells

Abstract

Performance decay of direct methanol fuel cells hinders technology competitiveness. The cathode electrochemical surface area loss is known to be a major reason for performance loss and it is mainly affected by cathode potential and dynamics, locally influenced by water and methanol crossover. To mitigate such phenomenon, novel materials and components need to be developed and intensively tested in relevant operating conditions. Thus, the development of representative accelerated stress tests is crucial to reduce the necessary testing time to assess material stability. In the literature, the most diffused accelerated stress tests commonly enhance a specific degradation mechanism, each resulting in limited representativeness of the complex combination and interaction of mechanisms involved during real-life operation. This work proposes a novel accelerated stress test procedure permitting a quantifiable and predictable acceleration of cathode degradation, with the goal of being representative of the real device operation. The results obtained with a 200 h accelerated stress test are validated by comparing both in situ and post mortem measurements with those performed during a 1100 h operational test, demonstrating an acceleration factor equal to 6.25x and confirming the development of consistent cathode degradation.

Keywords

• accelerated stress test
• degradation
• direct methanol fuel cell
• electrochemical active area loss
• electrochemical impedance spectroscopy