Carbon Supported PdSn Catalysts For Formic Acid Electrocatalytic Oxidation

In this thesis the preparation of PdSn/C catalysts and electrocatalytic oxidation of formic acid on PdSn/C were investigated. The X-ray diffraction (XRD) spectroscopy, transmission electron microscope (TEM), energy disperse spectroscopy (EDS) and the measurement of the electrochemically active surface area (ESA) were used to characterize the catalysts. The cyclic voltammetry (CV), linear sweeping curves (LSV) and chronoamperometry (CA) were used to measure the electrocatalytic performances of the catalysts for the oxidation of formic acid.The PdSn/C catalysts prepared in ethylene glycol (EG) system, microwave-assisted and reduced by formic acid exhibited greater eletrocatalytic activity and stability for the oxidation of formic acid. The particle size of the Pd/C catalysts in this method is about 8 nm.The experiment results indicate that Sn/C without obviously eletro-catalytic activity for formic acid electrochemical oxidation, however, the eletro-catalytic activity and stability of Pd/C catalyst for formic acid oxidation were improved evidently by adding metal Sn into the Pd/C catalyst. The electrocatalytic performance of the PdSn/C catalyst with the atomic ratio of 3:1 is best.Kinetic study of formic acid oxidation on carbon supported PdSn catalysts found that the oxidation of formic acid on PdSn/C electrode is a completely irreversible kinetic process. The diffusion coefficient, Tafel slope, reaction order, transfer coefficient and apparent activation energy of formic acid oxidation on the PdSn/C electrode were also investigated. The oxidation current densities increased with the increasing of the temperature in the range of 20～60℃. The activation energy of the oxidation of formic acid is almost constant when the potential between 0.2 and 0.6 V and significantly increased above 0.6 V, indicating that formic acid oxidation is more sensitive to temperature at relatively higher potential.