The Non-platinum Nano-catalyst Materials Used In Direct Ethanol Fuel Cell Anode

Low noble metal Ru,Pd show good electrocatalytic activity and stability for oxidation of ethanol due to their unfilled valence d orbital similar with Pt. Thus, they has gradually becomed electrocatalyst materials to replace the noble metal Pt for ethanol electro-oxidation. The synthesis of carbon supported nano-composite materials using polyvinyl-pyrrolidone (PVP) as protection agent was studied. The electrocatalysts containing Ru and Pd as the main active ingredient were characterized by electrochemical measurements.With this method, catalysts with high activity were obtained. The result showed that the Ru-PVP-C composite catalytic materials were spherical nanoparticals with diameter varying from 5 to 7 nm and had a well distribution and morphology. To optimize the preparation, the influence factores for catalytic activity were studied. In the process to add carbon carrier, various PVP/Ru molar ratio and Ru/carbon weight ratio were examined. The highest catalytic activity for oxidation of ethanol was found at the electrode with Ru content of 3.6%, the mole ratio PVP/Ru of 5:1. The optimal reduction temperature was observed in the range from 60～40℃. The Ru/CeO2 molar ratio of 1:1 in the catalysts were optimised to give the better performance. The result revealed that the addition of low-cost transition metal Mn, Co, Ni into Ru-PVP-C composite catalytics could significantly improve the electrode performance for ethanol oxidation and decrease the amount of low noble metal Ru.In alkaline solutions, a single metal Pd-PVP-C composite catalytic material show excellent electrocatalytic activity and stability for oxidation of ethanol. The TEM and XRD measurements indicated that the sample with average diameter ranging from 5 to 6 nm had a well dispersi-on and the Pd nanoparticles were face-centered cubic metallic. The addition of Ni into Pd catalysts could significantly dicrease the particle size and improve the performance. XRD analyses confirmed the formation of face-centered cubic crystalline Pd, Ni and Ni(OH)2. TEM showed that the PdNi-PVP-C particles were quite uniformly distributed on the surface of the carbon carrier with an average particle size of 4-5 nm. The highest catalytic activity and the poisoning resistance was found at 1:1.5 Pd/Ni mole ratio and 1.50% Pd/carbon weight ratio.Finally, the cells were assembled respectively by M-PVP-C as negative electrode, gas diffusion electrode as positive one,6 mol·L-1 C2H5OH+6 mol·L-1 KOH as the negative electrolyte and 6 mol·L-1 KOH as positive one with homogeneous membrane between the anode and cathode zones. The cell showed good performance with platform stability.