Beyond RDE characterisation – Unveiling IrRu/ATO OER catalyst stability with a GDE setup

In this study, we have investigated the stability of antimony-doped tin oxide (ATO) supported IrRu nanoparticles, as catalyst for the oxygen evolution reaction (OER). Conventional stability tests using a rotating disc electrode (RDE) are demonstrated to lead to distorted results, a fact typically addressed to the massive formation of O2 gas bubbles which block the catalytic active sites. In agreement with previous results, our investigations suggest that the observed decay in current density is not to be confused with catalyst degradation. To mitigate the limitations of the RDE approach, a gas diffusion electrode (GDE) setup was used instead for the stability measurements. Using a carbon gas diffusion layer (GDL) as substrate for the catalyst film, similar beginning-of-life (BoL) and end-of-life (EoL) activities were observed in the low current density region; however, large disparities were found at larger current densities. For meaningful degradation studies, the carbon GDL had to be replaced by a titanium-based substrate. This way a more accurate assessment of the catalyst stability is demonstrated. Although at steady-state conditions the tested IrRu/ATO catalyst exhibited a slight decrease in current densities with time, the BoL and EoL activities are nearly identical.