Dependence of catalytic activity of gas diffusion electrode on the particle size of catalyst for PEFCs

Dependence of catalytic activity of gas diffusion electrode on the particle size of platinum catalyst was measured using highly-active catalyst for polymer electrolyte fuel cells. The catalyst was prepared using trinitro-diammine Pt complex solution as a precursor. An average particle size of the platinum catalyst ranged in more than 1.2 nm. The catalytic activity of the platinum was evaluated using specific power density, i.e., power density pet a unit weight of loaded platinum. At loading amount of Pt catalyst of 0.06 mg/cm(2), the specific power density reached 6.7 W/mg-Pt. Also, mass activity of platinum catalyst was calculated. At the cathode potential of 0.9 V, the mass activity increased as the particle size decreased down to 1.5 nm. The linear relationship was observed between the mass activity and platinum surface area up to 150 m(2)/g. The specific activity obtained from the relationship between the mass activity and the surface area of platinum was estimated at 0.95 A/m(2)-Pt at 90 degrees C and under 5.84 atm. Consequently, the catalytic activity of platinum was kept for the ultra-fine particle such as platinum catalyst particle of 1.5 to 2 nm for PEFCs.