LAUSR

Abstract Improvements in polymer electrolyte fuel cell (PEFC) electrode performance have primarily focused on catalyst and ionomer developments, marginalizing the importance of catalyst ink formulation. Herein, the effect of ink formulation is examined across a series of cathodes comprised of PtCo supported on high surface area carbon (PtCo/ HSC ) and Nafion ionomer using an array of in situ electrochemical and ex situ characterization techniques. In contrast to prior work on Pt/Vu systems, ink water content had little effect on the electrochemically determined ionomer coverage for the PtCo/HSC electrocatalyst examined here. Characterization using nano-scale resolution X-ray computed tomography (nano-CT) demonstrated that water-rich ink formulations lead to a reduction in aggregate size (ionomer + PtCo/HSC), improving local O2 transport. This understanding, combined with the use of a commercially-available electrocatalyst was used to produced state-of-the-art membrane electrode assemblies with Pt loadings of 0.03/0.08 mgPt/cm2 on the anode and cathode respectively, having; i) > 1 A/mgPt (0.9 ViR-free, 150 kPa, 80 °C, 100% RH, H2/O2), ii) 320 mA/cm2 at 0.8 V, 150 kPa, 80 °C, 100% RH, H2/Air), and iii) > 1 W/cm2elec at rated power (0.67 V, 250 kPa, 94 °C, 65% RH, H2/Air) or