An adapted rotating disk electrode setup to test non-standard-disk electrodes: On the enhanced hydrogen evolution performance of model dewetted Pt nanoparticles vs. Pt thin films under hydrodynamic conditions

A common approach to test electrocatalyst nanoparticles for electrolyzers and fuel cells is to deposit catalyst particles (e.g., Pt/carbon) onto standard disk electrodes (e.g., glassy carbon) by making use inks based on binders (ionomers such as Nafion). In recent years, physical or chemical vapor deposition have garnered interest to deposit catalyst films or particles on electrode surfaces, to circumvent the complications associated with the use of inks. Samples prepared this way are often incompatible with standard equipment (rotating disk electrodes, RDEs) to assess the effect of mass transport on the electrode performance. Herein, we present a custom-built adapter designed to test samples prepared by physical deposition methods in a rotating disk electrode (RDE) setup. Using an outer-sphere redox probe (K4Fe(CN)6), we demonstrate that the custom-built adapter provides mass transport conditions comparable to those obtained with a standard disk electrode in a classic RDE setup. We then use the adapter to investigate the hydrogen evolution reaction (HER) activity of model Pt electrodes, i.e., sputter-deposited Pt thin films and thermally “dewetted” Pt NPs, in acid electrolytes. Under both hydrostatic and hydrodynamic conditions, the Pt NPs show significantly higher HER kinetics compared to Pt thin films. The results indicate that the enhanced HER activity observed for dewetted Pt NPs is intrinsic and of a kinetic nature, likely linked to catalyst/support interactions, and it is not a consequence of mass transport effects.