An Adapted Rotating Disk Electrode Setup to Test Nonstandard‐Disk Electrodes: On the Enhanced Hydrogen Evolution Performance of Model Dewetted Pt Nanoparticles Versus Pt Thin Films under Hydrodynamic Conditions

A common approach to test electrocatalyst nanoparticles (NPs) 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 of inks based on binders (ionomers such as Nafion). In recent years, physical and 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 might be incompatible with standard equipment, e.g., rotating disk electrodes (RDEs) to assess the effect of mass transport on the electrode performance. Herein, a custom‐built adapter is presented to test samples prepared by physical deposition methods in a RDE setup. Using an outer‐sphere redox probe (K 4 Fe(CN) 6 ), it is demonstrated that the custom‐built adapter provides mass transport conditions comparable to those obtained with a standard disk electrode in a classic RDE setup. Theadapter is used to investigate the hydrogen evolution reaction (HER) activity of model Pt electrodes, that is, 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 is not a consequence of mass transport effects.