For FePc/CNT ORR measurement, 2 mg of catalyst was dispersed in 1 mL of solution containing 0.882 ml of ethanol and 0.098 ml of water and 20 μL of 5 wt.% Nafion solution, which was sonicated for 1 h to form a homogeneous catalyst ink. All the catalysts were cast onto the RDE (diameter 5 cm) with a loading amount of 0.2 mg/cm 2 .