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

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.