Study On Pd-based Catalytic Materials For Ethanol Anode

:Pd-based catalysts for the ethanol anode in direct ethanol fuel cell (DEFC) were studied in this work. Pd/C, Pd-MxOy/C (M=Mo,Zn) and Pd-Rh-(MoO2)/C were prepared by ultrasonic dispersion combined with microwave heating-glycol reduction method. XRD pattern and TEM images showed that the size of these catalytic particles prepared was very small and distributed uniformly on the XC-72support. The effects of the additives MoO2, ZnO and noble metal Rh on the performance of Pd catalyst were evaluated using half-cell measurements and single cell discharging tests.The experimental results showed that Pd/C catalyst using carbon black as support had the best performance for ethanol oxidation reaction (EOR) in alkaline media. MoO2and ZnO added in Pd/C catalyst improved significantly the catalytic performance of Pd for EOR. It was found from the cyclic voltammograms (CV) recorded that the ethanol oxidation peak potentials for Pd-MoO2/C and Pd-ZnO/C electrodes were shifted negatively by0.10V and0.21V, and the peak current density were increased respectively by110mA cm-2and50mA cm-2in comparison with that of Pd/C under the same condition. In single cell discharging tests carried out at room temperature, the anode with Pd-ZnO/C catalyst showed more active and stable than that with Pd-MoO2/C.A different characteristic was observed from the CV recorded on the Pd-Rh/C electrode prepared comparing with that on Pd/C, which may be attributed to a difference of EOR mechanism at Pd-Rh/C and Pd/C electrodes. The presence of Rh in Pd-Rh/C may improve the completive oxidation of ethanol towards CO2. The Pd-Rh/C showed better catalytic performance than Pd/C. MoO2added in Pd-Rh/C improved further the performance.Single cells were constructed using air cathode and the ethanol anode investigated. Discharging tests were performed at room temperature. On the cell with Pd-ZnO/C anode, stable voltages of0.55V,0.46V and0.41V were obtained at10mA cm-2,20mA cm-2and30 mA cm-2and the voltages were still stable after3hours. An assembled cell was constructed with four single cells (in series), and its voltage reached1.3V at10mA cm-2. The cell worked continuously loading with a2.5V0.3A bulb.