Temperature dependence of kinetics of methanol electro-oxidation on PtSn alloys

The temperature dependence of methanol electro-oxidation properties has been investigated for Pt and PtSn alloys by high-pressure rotating disk electrode (RDE) measurements. The methanol oxidation reaction (MOR), which is the anodic reaction in direct methanol fuel cells (DMFCs), has been studied in the temperature range 25-140degreesC. Linear sweep voltammograms of MOR can be measured up to temperatures above the boiling point of methanol as well as water. The PtSn alloy shows superior electrocatalytic properties as compared with pure Pt. For example, the MOR current density at a PtSn electrode at 140 degreesC is about five times higher than that on pure Pt and eight times larger than that on the same material at room temperature. However, the anodic onset potential of MOR remarkably decreases with the increase of operating temperatures. Moreover, the potential of the PtSn electrode is approximately 0.2 V smaller than that on Pt over a wide temperature range. This paper suggests that the RDE electrochemical characterizations at elevated temperatures provide useful basic electrode properties for an efficient DMFC at higher operating temperature, which has recently been recognized as an option for this technology. (C) 2003 The Electrochemical Society.