Membrane electrode assembly with ultra low platinum loading for cathode electrode of PEM fuel cell by using sputter deposition

Abstract

Cathode electrodes of proton exchange membrane fuel cells were fabricated by using Pt sputter deposition to increase the gravimetric power density (WmgPt-1) with reduced Pt loading. Ultra low Pt-based electrodes having Pt loading in between 0.0011 and 0.06 mgPtcm-2 were prepared by a radio frequency (RF) sputter deposition method on the surface of a non-catalyzed gas diffusion layer (GDL) substrate by changing the sputtering time (20, 90, 180, 1050 s). The effect of cathode Pt loading on the performance of membrane electrode assembly were investigated using polarization curve, impedance, H2 crossover and cyclic voltammetry techniques. The effect of backpressure on PEMFC performance was also investigated. Sputter1050 (0.06 mgPtcm-2) exhibited the best power density at 80°C cell temperature and without backpressure for H2/O2, 100 %RH (297 mWcm-2 and 5 WmgPt-1 at 0.6 V). On the other hand sputter90 (0.005 mgPtcm-2) showed the peak gravimetric power density (15 WmgPt-1 and 75 mWcm-2 at 0.6 V). The Pt utilization efficiency increased as the Pt loading decreased. Sputter20 and sputter90 electrodes yielded insufficient electrochemical surface area (ECSA), higher charge transfer and ohmic resistance, but sputter180 and sputter1050 yielded sufficient ECSA and lower charge transfer and ohmic resistance.