Particle-Size Effect of Pt Anode Catalysts on H 2 O 2 Production Rate and H 2 Oxidation Activity at 20 to 80 °C

Abstract

Polymer electrolyte membranes (PEMs) for fuel cells are chemically degraded by ·OH radicals, generated from H 2 O 2 , which is produced by a reaction of hydrogen adsorbed on the Pt anode with O 2 diffusing through the PEM. In order to obtain a clue for designing the anode catalyst with low production rate of H 2 O 2 and high activity for the hydrogen oxidation reaction (HOR), we have examined the H 2 O 2 production rate at Pt catalysts as a function of particle size d Pt ranging from 2 nm to 20 nm over a practical temperature range between 20 and 80 °C in 0.1 M HClO 4 . The H 2 O 2 production rate [per geometric area with 1.5 to 2-layer height of catalyst layer] was found to decrease with increasing d Pt , accompanied by a penalty of decreased mass activity for the HOR. The use of Pt skin-covered PtCo/C is shown to be an attractive potential solution, providing a breakthrough in simultaneously achieving low H 2 O 2 production and high HOR activity.