Pulsed vs. galvanostatic accelerated stress test protocols: Comparing predictions for anode reversal tolerance in proton exchange membrane fuel cells

Fuel starvation events occur in proton exchange membrane fuel cells (PEMFCs) when the flow fields become blocked by ice or dust/debris from the environment. When this occurs, the electrons at the anode catalyst layer (ACL) must be generated by either water oxidation or carbon corrosion which forces the cell into a ‘reversal’ event. Such events rapidly degrade the anode catalyst layer, but can be mitigated through the use of reversal tolerant catalysts (RTCs) such as IrOx. While widely used in industry, this topic has not received significant attention in the literature. At the membrane electrode assembly (MEA)-level, there are two main approaches to evaluate reversal tolerance: 1) Galvanostatic and 2) Pulsing. In galvanostatic accelerated stress tests (ASTs), the current is held at a constant value until the cell voltage reaches a predetermined value. For pulsing ASTs, the MEA is put through short term ‘reversal’ conditions before going back to normal operating mode. These ASTs are in fact quite different in terms of the stress they put on the ACL. Here, we directly compare these two ASTs, showing that, when normalized for the same amount of total reversal time, the pulsing experiments result in more severe anode damage than galvanostatic testing.