Benchmarking proton exchange membrane fuel cell cathode catalyst at high current density: A comparison between the rotating disk electrode, the gas diffusion electrode and differential cell

Abstract

The intrinsic activity of oxygen reduction reaction (ORR) electrocatalysts for proton exchange membrane fuel cell (PEMFC) is usually evaluated with the rotating disk electrode (RDE), an easy-to-use technique requiring little amount of electrocatalyst. However, the liquid environment of the RDE implies strong limitation of O2 mass-transport and the intrinsic activity is only accessible on a narrow potential range (from 0.95 to 0.85 V vs. RHE) that is not relevant for the PEMFC operating conditions. This work compares results obtained with the RDE (0.2 cm2), the gas diffusion electrode (GDE, 0.07 cm2) and a small unit PEMFC (DC, 1.8 cm2). Three widely used ORR electrocatalysts are compared: Pt/Vulcan carbon, PtCo/Vulcan carbon and Pt/graphitized carbon, catalytic layers being prepared with a loading of 20 μgPt cm−2 and characterized at 25–30 °C and full hydration. The results show that all setups have their own advantages and drawbacks. Regardless the electrocatalyst nature, the GDE allows to assess the intrinsic activities on a large potential range (from 0.9 to 0.6 V), in agreement with the results obtained in RDE for high potential and with the DC for lower potential. The GDE is therefore promising, enabling easy high current density measurements with little amount of electrocatalyst.