| Summary: | 碩士 === 明道大學 === 材料暨系統工程研究所 === 96 === United Regenerative Fuel Cell (URFC) is a device which combines an electrolyzer and a fuel cell. It has the advantage of low cost, weight, and volume in comparison to Regenerative Fuel Cell (RFC). There are two main operation where the URFC is used. The first is a water electrolysis operation where hydrogen and oxygen are generated. The second is during a fuel cell operation, where hydrogen oxidation and oxygen reduction take place, as a result of this a current is produced.
In this study, a new formula to improve the stardard Impregnation-reduction (IR) method is proposed to prepare an nanometer-sized Iridium catalyst and a Platinum/Iridium catalyst particle layer on the surface of a Nafion®membrane. A novel Platinum/Iridium catalyst structure on the surface of a Nafion®membrane is expected to improve oxidation activity for the oxygen electrode in the URFC. In addition, the IR process can produce a good binding for both the Nafion®membrane and the catalyst used, with the result of a more stable URFC is obtained. Scanning Electron Microscopy (SEM), X-ray Diffraction (XRD), Electron Probe X-ray Micro-Analysis (EPMA), X-ray Photoelectron Spectrometer (XPS), and Transmission Electron Microscope (TEM) were used to analyse the microstructure, phase, amount, particle size of the resulted catalyst, the deepness and thickness of catalyst on the PEM surface as well as the ratio of obtained alloy. Fourier-Transform Infrared Spectrometer (FTIR) was adopted to ensure the sample did not have any remaining alcohols. A potentialstat was used to test the water oxidation ability of the resulted catalyst.
The results show that some alcohol was added during the impregnation process to let the IrCl62- become more positive to ion-exchange with the proton in PEM. Furthermore, the effective deposition of Ir particle on the surface of PEM required the reduction reaction temperature up to 80℃ and the pH of the solution from 2 to 3 during the reduction process. The resulting catalyst thickness is controlled by the amounts of precursor ion implants in the PEM, the amount of alcohol, the reduction time and the pH of solution.
In order to get a higher oxidation performance for the oxygen electrode, we used a novel method to dope Ir in Pt layer. The atomic ratio of Pt over Ir is 9:1 with the resulting thickness of 1.5μm. The oxidation potentail of the obtained Pt/Ir is higher than that of Pt catalyst with 0.11V. Based on this criterion, the oxidation abilty of Pt/Ir catalyst is worse then that of pure Pt catalyst.
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