Low equivalent weight short-side-chain perfluorosulfonic acid ionomers in fuel cell cathode catalyst layers

► Low equivalent weight short-side-chain Aquivion™ ionomer in the cathode catalyst layers. ► 20 wt% Aquivion as the optimal loading in the cathode catalyst layer. ► Lowered ORR kinetics in Aquivion™-based MEAs at 100% RH due to the large mass transport resistance. ► Improved fuel cell performance under operating conditions of 95 °C and RH values of 30, 50 and 70%.