Accurate determination of catalyst loading on glassy carbon disk and its impact on thin film rotating disk electrode for oxygen reduction reaction.

Thin film-rotating disc electrode (TF- RDE) experiment provides a fast research platform for screening of newly developed electrocatalysts for oxygen reduction reaction (ORR) activity, however, precise estimation of their performance parameters is necessary to avoid wastage of resources in the testing of otherwise unpromising electrocatalyst in actual fuel cells. Here the importance of accurate amount of catalyst (e.g. Pt) on GC disk of RDE in TF-RDE experiment is presented by characterizing the inks based on commercial catalysts for their electrocatalysis performance (ORR activity) and while estimating the performance parameters. The amount Pt loadings estimated using literature based (conventional) scheme as well as, the proposed, X-ray fluorescent (XRF) based scheme is presented. A parameter defined as ‘catalyst-density-of-the-ink’, which is based on estimated Pt-loadings using conventional and XRF based scheme, is used to correlate the variation observed in the estimated performance values and the amount of Pt on GC disk of RDE. The investigation suggests that the actual Pt loading on GC disk of RDE varies with the ink-conditions, which is considered constant in the conventional scheme, might be leading to irreproducibility of the data obtained by TF-RDE experiments. The XRF based scheme, which is simple and direct, can have the potential to replace conventional scheme for accurate catalyst loading estimation, improve experimental reproducibility and open many other possibilities (e.g. catalyst loading determination after tests) in electrocatalysis studies.