Challenges and limitations of accelerated stress testing in GDE half-cell set-ups

Abstract

Commercialisation of proton exchange membrane fuel cells (PEMFCs) depends on accurate and high throughput durability testing at the laboratory scale. With the rotating disk electrode method (RDE) unable to mimic the three-phase boundary scenario in the membrane electrode assembly (MEA), gas diffusion electrode half-cells were proposed for fundamental catalysis research. However, durability testing in such half-cell setups under realistic operational conditions has been limited, and in particular, not yet validated against RDE or FC data. In this paper, an attempt is made to fill part of this knowledge gap by performing accelerated stress tests in thin films, gas diffusion electrodes and membrane electrode assemblies. The results are compared for two selected catalysts with different Pt loading, expected to show broad variations in their degradation behaviour. Accelerated stress tests (ASTs) were performed with various start/stop potentials and load cycles, and the oxygen reduction reaction (ORR) performance studied before and after the AST protocols. The internal resistance of the half-cell was found to be influenced most significantly by gas coverage and temperature changes on the working electrode and must be compensated accordingly. The applied vertex potentials for ASTs after compensation have to be accurate in order to induce the intended degradation phenomena.