Author

Bo Ma

Date of Graduation

Fall 2012

Degree

Master of Science in Materials Science

Department

Physics, Astronomy and Materials Science

Committee Chair

Lifeng Dong

Keywords

direct methanol fuel cell, direct ethanol fuel cell, anode catalysts, electrochemical impedance spectroscopy, negative resistance, equivalent circuit

Subject Categories

Materials Science and Engineering

Abstract

In this work, platinum (Pt) and platinum-ruthenium (Pt+Ru) nanoparticles were synthesized on carbon black (CB) and single-walled carbon nanotubes (SWCNTs) and studied with scanning electron microscopy (SEM). Electrocatalytic activities of these catalysts (CB-Pt, CB-Pt+Ru, SWCNT-Pt, and SWCNT-Pt+Ru) for methanol and ethanol oxidations were investigated with cyclic voltammetry and electrochemical impedance spectroscopy (EIS). Effects of supporting materials (CB and SWCNTs) on electrochemical activity and tolerance of carbon monoxide (CO) poisoning of Pt and Pt+Ru nanoparticles in methanol and ethanol solutions were studied comparatively and possible mechanisms were discussed. Semicircles in the second quadrant of the Nyquist diagram were observed for both methanol and ethanol oxidations under various potentials for different catalytic nanoparticles, indicating the occurrence of negative resistance during electrocatalytic methanol and ethanol oxidations. The electrocatalytic characteristics of all catalysts were analyzed further by using equivalent circuits. We found that low intermediate coverage occurs on the catalyst surface during interfacial methanol and ethanol oxidation reactions, and thereby, the real component of impedance can be a negative value due to the electrochemical oscillation during methanol and ethanol oxidations. Therefore, methanol and ethanol oxidations on Pt and Pt+Ru surface can be explained as a rate determined step, and the efficiency of different catalysts for methanol and ethanol oxidations are also discussed.

Copyright

© Bo Ma

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