An overview of platinum-based catalysts as methanol-resistant oxygen reduction materials for direct methanol fuel cells

Low-temperature fuel cells, with either hydrogen or methanol as the fuel, represent an environmentally friendly technology and are attracting considerable interest as a means of producing electricity by direct electrochemical conversion of hydrogen/methanol and oxygen into water/water and carbon dioxide. Platinum has the highest catalytic activity for oxygen reduction of any of the pure metals and when supported on a conductive carbon serves as state of the art cathode material in low-temperature fuel cells. Regarding the direct methanol fuel cells (DMFCs), one of the major problems is the methanol crossover through the polymer electrolyte. The mixed potential, which results from the oxygen reduction reaction and the methanol oxidation occurring simultaneously, reduces the cell voltage, generates additional water and increases the required oxygen stoichiometric ratio. This problem could be solved either by using electrolytes with lower methanol permeability or by developing new cathode electrocatalysts with both higher methanol tolerance and higher activity for the oxygen reduction reaction than Pt. Pt alloyed with first-row transition elements is proposed as cathode material with improved methanol tolerance for direct methanol fuel cells. In the light of the latest advances on this field, this paper presents an overview of platinum-based catalysts as methanol-resistant oxygen reduction materials for direct methanol fuel cells. (C) 2007 Published by Elsevier B.V.