Effect of Added Graphitized CB on Both Performance and Durability of Pt/Nb-SnO2 Cathodes for PEFCs

The single cell performances of polymer electrolyte fuel cells (PEFCs) using Pt catalyst supported on Nb-SnO2 (Pt/Nb-SnO2) with/without graphitized carbon black (GCB) were compared with that of a cell using Pt/GCB. The Pt-mass specific power of the Pt/Nb-SnO2 cathode under low humidity conditions was superior to that of the Pt/GCB cathode, because the hydrophilic SnO2 support helped to increase the proton conductivity of the ionomer, which led to high Pt effectiveness. The addition of GCB to the Pt/Nb-SnO2 cathode improved the cell performance under high humidity, and the Pt-mass specific power value reached more than 10 kW gPt−1. The improvement conditions was attributed to the formation of gas diffusion paths by adding the hydrophobic GCB. The Pt/Nb-SnO2 cathodes, with/without GCB, had greater durability than that of the Pt/GCB cathode during the startup / shutdown potential sweep evaluation. The migration of Pt particles on the Nb-SnO2 support was suppressed by the high stability of Nb-SnO2 and strong orientation between Pt and Nb-SnO2 support. The degradation of GCB in the Pt/Nb-SnO2 cathode was smaller than that in the Pt/GCB cathode because of the absence of Pt on the added GCB. Therefore, the added GCB was still able to provide gas diffusion paths even after extensive cycling.