Improvement of Cell Performance in Low-Pt-Loading PEFC Cathode Catalyst Layers with Pt/Ta-SnO2 Prepared by the Electrospray Method

Abstract

To reduce the Pt loadings in cathode catalysts for polymer electrolyte fuel cells, we focused on the catalyst material and catalyst-layer (CL) fabrication method, and prepared low Pt loading CLs with Pt/Ta-SnO2 by the electrospray (ES) method. Two CLs were prepared by the ES method with different mass ratios of ionomer binder to support material (I/S), I/S = 0.7 and 0.2, and are compared to that prepared by the pulse-swirl-spray (PSS) method. Both ES CLs have higher porosity than that for the PSS CL, and have improved ionomer coverage and increased electrochemically active surface area (ECA) and mass activity at 0.85 V. In particular, that for the ES with I/S = 0.2 has high porosity and remarkably increased cell performance. The improvement obtained by use of the ES method can be explained on the basis that the coverage and uniformity of ionomer are increased due to the small droplet size. The performance of the ES cells is high, particularly under high backpressure conditions, because of the improved transport of both O2 and protons. ES is an attractive method for the reduction of the Pt loading while improving cell performance.