Analysis of Low Platinum Loading Thin Polymer Electrolyte Fuel Cell Electrodes Prepared by Inkjet Printing

Thin, low Platinum loading polymer electrolyte fuel cell (PEFC) electrodes fabricated by inkjet printing are investigated. Catalyst coated membranes (CCMs) with Pt loading of 0.026 mgPt/cm2, catalyst layer thickness between 1.5 and 2 μm and varying Nafion loadings (NL) on the cathode electrodes of 10, 20, 30, 40 and 50 wt% are analyzed. Ex-situ scanning electron microscopy (SEM) visualization shows that the layers are porous and composed of Pt/C aggregates binded by ionomer. In-situ electrochemical testing shows that the Tafel slope of these electrodes is relatively large, i.e., 120 mV/dec. Further, at 80 °C and varying relative humidities, the CCMs are not sensitive to Nafion loading changes within the 20 wt% - 40 wt% range. Proton transport limitations are only observed at low NL of 10 wt% while transport losses are only observed at high currents for CCM with 50 wt% NL. Comparing conventional and thin, low loading, inkjet printed electrodes, the inkjet printed electrodes show a much higher sensitivity to oxygen partial pressures. These results suggest that macro-scale oxygen and proton transport are not limiting the electrode at the 20 wt% - 40 wt% Nafion range. Pt mass activity for the inkjet CCM at ambient pressure was observed to be 196 A/mgPt (12.4 kW gPt−1), i.e., 10 times higher than a spray coated CCM, due to its reduced CL thickness and thereby reduced transport losses in the macro-scale. The Pt utilization at 2 bar gauge pressure is 47.6 kW gPt−1 and represents one of the highest utilization values reported for low Pt loading electrodes.