Bridging Fundamental Electrochemistry with Applied Fuel Cell Testing: A Novel and Economical Rotating Disk Electrode Tip for Electrochemical Assessment of Catalyst-Coated Membranes

A novel rotating disk electrode (RDE) tip capable of characterizing catalyst coated substrates and compatible with commercial RDE systems is presented. The RDE tip, which uses a top-oriented Ti-based current collector, is demonstrated with Pt foil and commercial catalyst coated membranes (CCM). The specific activity of the platinum foil for oxygen reduction reaction is about 1.55 mAkinetic cmPt−2 in 0.1 M HClO4 at room temperature (20°C), which is in agreement with the measurements reported for polycrystalline Pt. The Ti-based current collector leads to a very small (≈ 5.6%) loss in the electrochemical surface area (ECSA). Hydrodynamic calculations and oxygen reduction measurements confirm that even at the fastest rotation speeds used in this type of measurement (i.e., 1600 rpm), the laminar flow regime (Re ≈ 56) is maintained, allowing one to apply classical RDE analysis. Repeatable and high quality cyclic voltammograms (CVs), oxygen reduction curves, and mass and specific activities for commercial CCMs were obtained in 0.1 M HClO4 at room temperature (20°C). The activities determined from these experiments are in agreement with those of the H2/O2 fuel cell measurements under equivalent operating conditions. Degradation of the CCM's catalyst during a 30,000 potential cycling accelerated degradation test (ADT) is performed using a 0.4 mgPt cm−2 commercial CCM and shows an ECSA loss of ≈ 0.0010 m2 gPt−1 cycle−1 and a mass activity loss of ≈ 1.8 × 10−6 A mgPt−1 cycle−1. Details of the design, implementation, and results of this economical and novel approach for characterization of CCMs are presented and discussed.