33b Deposition of PtxRu1-X Catalysts for Methanol Oxidation In Micro Direct Methanol Fuel Cells

William Mustain, Hyea Kim, Shruti Prakash, and Paul Kohl. Chemical and Biomolecular Engineering, Georgia Institute of Technology, 311 Ferst Dr., Atlanta, GA 30332

Micro fuel cells can power small devices (e.g. wireless sensors) because they can contain possess very high energy-density fuels, such as methanol. However, in order to utilize concentrated methanol and operate efficiently at low-power, the electrode structure needs to be optimized for low-mass and minimum cross-over.

In this work, the electrode structure was changed for low-power fuel cell applications. Platinum-ruthenium electrodes (PtxRu1-x) have been prepared by electrochemical and electroless deposition and investigated as catalysts for the oxidation of methanol in acidic solutions. PtxRu1-x deposits were electrochemically deposited from acidic chloride electrolytes at potentials between -0.46 and 0.34 V (vs. NHE). The composition of the electrodeposit was estimated by energy dispersive x-ray spectroscopy and is a strong function of the electrode potential. An empirical model for the deposition process is presented and kinetic parameters are estimated and discussed. Also, the methanol oxidation activity of the PtxRu1-x catalysts was characterized by cyclic voltammetry in 1.0 M CH3OH, 1.0M H2SO4 solutions.

Electroless PtxRu1-x samples were prepared in a modified Leaman bath with hydrazine dihydrochloride as the reducing agent. The kinetic results for the electrochemical deposition of PtxRu1-x were directly applied and the deposition potential was estimated as approximately 0.40 V.