Electrocatalytic Oxidation Of Hydrazine On Pd Catalyst

The direct hydrazine fuel cell (DHFC) is a potential candiate for portable applications due to easiness of fuel transport and fuel storage, high energy and high energy conversion efficiency. In this work, multi-walled carbon nanotubes (MWNTs) supported Pd nanoparticles (Pd/MWNT) catalysts were prepared complexation-reduction reaction and homogeneous precipitation reduction reaction. Moreover, the electrooxidation of hydrazine on Pd/MWNT catalysts was investigated systematically. As these issues to be addressed, the following researches have been carried out.1. Purified multi-walled carbon nanotubes (MWNTs) were treated with concentrated HNO3 or mixed acid (V HNO3:V H2SO4=1:1) at 50℃for 5 h, respectively. After 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. After MWNTs were treated in mix acid solution (VHNO3:VH2SO4=1:1), 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..2. Pd nanoparticle catalysts supported by multiwall carbon nanotubes (Pd/MWNTs) prepared using a complexation-reduction method were used in this study for the electrochemical determination of hydrazine. The physico-chemical properties of the Pd/MWNT catalyst were characterized by X-ray diffraction analysis (XRD), transmission electron microscopy (TEM) and scanning electron microscopy physico-chemical (SEM). These structural analyses revealed that the Pd/MWNTs-modified glassy carbon electrode possessed a three-dimensional network structure in which the Pd nanoparticles, with an average size of 5 nm, are uniformly distributed on the surface of the MWNTs. After Nafion solution was coated on the surface of the Pd/MWNT layer, the resulting Pd/MWNT-Nafion modified electrode retained the three-dimensional network structure. Electrochemical measurements showed that the oxidation peak current of hydrazine decreased with increasing pH. Under optimum conditions, the Pd/MWNT-Nafion-based hydrazine sensor exhibited a broad linear calibration range (2.5-700μM) and a low detection limit of 1.0μM for hydrazine..3. Pd/MWNTs catalysts were prepared through complexation-reduction reaction and homogeneous precipitation-reduction reaction method. XRD and TEM measurements show that the particle size of Pd/MWNTs catalyst was strongly dependent on preparation method. Compared with complexation-reduction reaction method, Pd/MWNTs catalyst prepared via homogeneous precipitation-reduction reaction method showed a higher catalytic activity and stability for the hydrazine electrioxidation in strong acidic solution conditions.