Evaluation of Palladium-based electrocatalyst for oxygen reduction and hydrogen oxidation in intermediate temperature polymer electrolyte fuel cells

A carbon-supported Palladium electrocatalyst was investigated for oxygen reduction and hydrogen oxidation in a polymer electrolyte fuel cell operating at intermediate temperatures (80-110 degree C) and with low relative humidity (33%). A 30% Pd/C was synthesized by a colloidal method and subsequent carbothermal reduction. A mean particle size of 4.0 nm and a homogeneous dispersion of Pd particles on the support were obtained. The performance of the Pd catalyst was compared to those obtained with a 50% Pt/C catalyst and a 50% Pt sub(3)Co sub(1)/C as anode and cathode, respectively. The Pd/C catalyst showed low overpotential for hydrogen oxidation whereas its performance as cathode was significantly lower than the benchmark Pt sub(3)Co sub(1) catalyst. The main limiting effects for the Pd-based electrocatalyst appeared to be associated to a larger mean particle size compared to the benchmark Pt catalysts and to the modification of the carbon support during the synthesis procedure. These effects led to a stronger activation control, a slight increase of the series resistance and some diffusion constraints.