The Studies of Anode Impedance and CNT-supported Pt-Ru Catalyst for Direct Methanol Fuel Cells

• Main Authors: Ning-Yih Hsu, 許寧逸
• Other Authors: 顏溪成
• Format: Others
• Language: en_US
• Published: 2006
• Online Access: http://ndltd.ncl.edu.tw/handle/49570158877608800562

博士 === 國立臺灣大學 === 化學工程學研究所 === 94 === Abstract In this work, electrochemical impedance was used to analyze the reaction kinetics and interfacial characteristics of an anode in a direct methanol fuel cell (DMFC). An advanced equivalent-circuit model is proposed. The new model incorporates constant phase elements (CPEs) rather than conventional capacitors in the equivalent-circuits taking into account the porous structure of the anode, particularly that in the catalyst layer and at the anode/membrane interface. It effectively simulated the electrochemical characteristics of a DMFC porous anode. The impedance model incorporates the interface factor, resulting in excellent matches between the simulation results and the experimental data in the Nyquist and the Bode plots over a wide range of frequencies. In addition, the differences among methanol electrooxidation reaction kinetics at various operating potentials are clearly observed and satisfactorily explained using electrochemical impedance spectroscopy and the CPE-based equivalent-circuit model. The performance of a single-cell direct methanol fuel cell (DMFC) using carbon nanotube-supported Pt-Ru (Pt-Ru/CNT) as an anode catalyst has been investigated. In this study, the Pt-Ru/CNT electrocatalyst was successfully synthesized using a modified polyol approach with a controlled composition very close to 20wt%Pt-10wt%Ru, and the anode was prepared by coating Pt-Ru/CNT electrocatalyst on a wet-proof carbon cloth substrate with a metal loading of about 4 mg cm-2. A commercial gas diffusion electrode (GDE) with a platinum black loading of 4 mg cm-2 obtained from E-TEK was employed as the cathode. The membrane electrode assembly (MEA) was fabricated using Nafion