| Summary: | 碩士 === 國立中興大學 === 材料科學與工程學系所 === 100 === Direct methanol fuel cell (DMFC) is a device converting fuel into electric energy and usually used for portable electronic applications. Pt-Ru catalysts are widely used to solve the problem caused by carbon monoxide (CO) which is the intermediate during methanol oxidation. In this study, two kinds of iron-contained phosphate porous microspheres were prepared as the supports for Pt catalysts to improve the performance in fuel cells and prevent the CO poisoning.
As-synthesized iron phosphate microspheres were synthesized by chemical precipitation method and used as one kind of supports. Vivianite, (Fe3(PO4)2‧8H2O), was transformed into dehydrated amorphous iron phosphate from 100 °C to 500 °C, and crystalized into FePO4, Fe3PO7, and Fe2O3 above 600 °C, identified by thermal gravimetric analysis/differential scanning calorimetry (TGA/DSC) and X-ray diffraction (XRD). The iron phosphate porous microsphere was composed of plates and the diameter was about 10μm. The particle size of Pt supported on vivianite (Pt/V) is around 4.2 nm. The cyclic voltammetry indicated that the electrochemical surface area (ECSA) ranges from 128 to 155 m2 g-1. The mass activity of Pt/V was 8.98 A/gPt at 0.2 V vs. Ag/AgCl for methanol oxidation reaction. No forward or reverse current peak was observed, indicating scarce CO poison effect.
FeHAp microspheres are used as the other kind of support for Pt. The Pt particle size is around 4.4 nm analyzed by XRD and 3.41 nm observed by TEM. The cyclic voltammograms of Pt/FeHAp catalysts exhibit the characteristics of Pt (110) with desorption peak potential at -0.128 V (vs. Ag/AgCl) similar to Pt/vivianite. The ECSA of Pt20/FeHAp (200 m2 g-1) is greater than those of Pt33/FeHAp and Pt50/FeHAp. However, Pt33/FeHAp shows the greatest mass activity (190.4 A/gPt, at 0.81 V vs. Ag/AgCl) of methanol oxidation, although the IF/IR ratio is just 1.18.
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