| Summary: | 碩士 === 國立中央大學 === 材料科學與工程研究所 === 106 === Direct ethanol fuel cells (DEFCs) have been attracted much attention recently because ethanol can be produced from biomass through various methods including fermentations. However, owing to poisoning by adsorbed intermediates such as COad and CHxad, the electro-oxidation of ethanol is sluggish. In order to enhance the ethanol oxidation reaction (EOR) performance, carbon-supported Pt-based nanorods (NRs) catalysts, including PtAu, PtSn, PtPdSn and PtAuSn have been prepared via formic acid method (FAM). The lattice structures, surface compositions, chemical compositions, morphologies and electrochemical properties of prepared catalysts are characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), inductively coupled plasma-optical emission spectrometer (ICP-OES), high resolution transmission electron microscopy (HRTEM), and electrochemical measurements, respectively.
This study is divided into two parts. In the first part, carbon-supported Pt-based binary and ternary NRs are prepared and their activity and durability performance have the same order PtAuSn20 > PtPdSn > PtSn > PtAu. With the third elements addition, PtAuSn20 NRs not only have the high oxophilicity that can activate the dissociative adsorption of ethanol on Pt surface, but also have synergies effect through electronic modification effect and bi-functional mechanism. Besides, PtAuSn20 with the Pt core/Au sublayer/Sn shell structure has the best stability.
In the second part, the effect of compositions on the EOR performance of PtAuSn NRs has been investigated. PtAuSn NRs with Pt/Au/Sn ratios of 70/5/25, 70/10/20 and 70/20/10 have been prepared (named as PtAuSn25, PtAuSn20 and PtAuSn10, respectively). According to XPS results, Au/Sn ratios of PtAuSn25, PtAuSn20 and PtAuSn10 are closed to 1/4, 1/2 and 1/5, respectively. The EOR activity of PtAuSn20 with the largest Au/Sn ratios is the highest, which can be contributed to the tensile strain provided by Au. Otherwise, CA tests have the same order of Sn and SnO2 contents, which is PtAuSn25 (50%) > PtAuSn10 (43%) > PtAuSn20 (38%). Based on the above results, we have demonstrated that by tuning the Sn and Au ratio, the EOR performance can be promoted effectively.
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