22. Study of evaluation methods for non-platinum oxygen reduction catalysts prepared by a spray drum drying method and a closed vessel

Abstract

Rotating ring disk electrode methods - which have been used as an evaluation method for catalysts for polymer electrolyte fuel cells - , have poor reproducibility especially in the region of diffusion limiting current. The aim of this study is to analyze the factors such as oxygen concentration in solution and catalyst dispersion state on a disk electrode that cause the poor reproducibility. Under the condition of oxygen replacement for 30 minutes, the uncertainty of oxygen concentration accounted for 30.1% of the total uncertainty. When catalyst inks were dispersed by ultrasonic irradiation, the diffusion limit current derived from the oxygen reduction current increased with the increase of the ultrasonic irradiation time and reached a maximum at 30 minutes. On the other hand, when the catalyst ink was prepared by ultrasonic irradiation (30 s)-shaking (19 h)-ultrasonic irradiation (90 s), the maximum diffusion limiting current was obtained.