Purified multi-walled carbon nanotubes (MWNTs) were treated with concentrated HNO₃ or mixed acid [V(HNO₃)∶V(H₂SO₄)＝1∶1], respectively. When MWNTs were treated in concentrated HNO₃ solution, suitable amount of hydrophilic O-containing surface groups would be formed. So the average size of the Pd nanoparticles deposited on the surface of the pretreated MWNTs is small and uniform, leading to the good electrocatalytic performance of the resulting Pd/MWNTs catalyst for the hydrazine electrooxidation. If purified MWNTs were untreated, the pristine surface of MWNTs prevented deposition of Pd nanoparticles on the surface of MWNTs, which lead to the aggregation of Pd nanoparticles. When MWNTs were treated in mix acid solution, the amount of the hydrophilic O-containing surface groups formed on MWNTs was abundant, which also resulted in the agglomeration of Pd nanoparticles. Consequently, the resulting Pd/MWNTs catalysts displayed the low electrocatalytic performance for the hydrazine electrooxidation.

Key words: carbon nanotube, Pd nanoparticle, hydrazine, electrocatalytic oxidation, fuel cell