Synthesis and Caracterization of ZrO2/PANI Composite As Electrocaltalyst Support for Direct Alcohol Fuel Cells

Abstract

Carbon Vulcan has been widely used as electrocatalyst support despite its susceptibility to electrochemical corrosion. Zirconium oxides are a promising alternative due to its corrosion resistance in acid and alkaline media, the main drawback of these materials are their low conductivity and surface area. Therefore, an alternative to overcome this is, to develop a composite with conducting polymers (CPs) like polyaniline. conducting polymers fulfill the main requirements for fuel cell application: high surface area, to obtain high metal dispersion, suitable porosity, high electrical conductivity, and high stability under fuel cell operational conditions. In this work Pt as electrocatalyst was supported by chemical reduction onto nanostructured ZrO2 followed by chemical deposition of PAni. Every element of the composite was characterized individually. Zirconium oxide was synthesized by sol-gel technique, using different calcination temperatures (300 and 350 °C), TEM analysis shows that zirconia has a particle size between 100 and 1000nm in a disperse pattern with some agglomerates, the X ray diffraction pattern correspond to an amorphous structure. The surface area was determined by nitrogen adsorption and goes from 60 and 160m2/g depending on calcination temperatures. PAni was synthetized by chemical method and showed different morphology depending on incubation temperature and with different corresponding conductivity capacities. When the bath temperature was at -16°C a notorious microfibrillar pattern could be seen by SEM analysis, but the sample color was not characteristic of emeraldine (conductor PAni salt). However, when bath temperature was 2 and 20°C, the color allowed to confirm that emeraldine was the PAni phase presented but with porous nanoparticular morphology. From previous experimental work it is clear that Pt/ZrO2 has a superior performance towards methanol oxidation reaction than Pt/C (20%), especially on alkaline conditions. In this work, the synthesis of PAni over Pt/ZrO2 does not affect the electrocatalytic activity neither in acid or alkaline conditions. Therefore, the low surface area of zirconium could be properly compensated with this conductive polymer. However, stability tests are necessary to consider this composite as adequate substitute for carbon based electrocatalysts supports in direct alcohol fuel cells.