Analysis of Oxygen Transport Resistances in the Catalyst Layers with Different Carbon Supports in PEFC

For efficient use of Pt catalyst in polymer electrolyte fuel cells, the oxygen transport resistances with different carbon supports, Vulcan and Ketjen black, in the cathode catalyst layer (CL) were evaluated by experiments and model analysis. To distinguish the contributions of resistance components for oxygen transport, in the CL pores, at the interface between gas and ionomer, and in ionomer near the Pt surface, CLs with different structures were fabricated and oxygen transport resistance of these CLs were measured. The results showed that Pt particles are arranged outside the carbon in the CL with Vulcan, and the oxygen transport resistance at the Pt surface is reduced than in the CL with Ketjen black. However, the porosity of the Vulcan CL becomes lower, and the diffusion resistance in the CL pores increases. These suggest that achieving higher porosity with Vulcan is effective to reduce the oxygen transport resistance in the CL.