Development of fuel-cell catalysts for elevated temperature applications requires electrochemical techniques that simulate these conditions. A pulsed reactant electrochemical flow cell (PREFC) technique has been developed, capable of independent half-cell measurements of methanol electro-oxidation current and poisoning adsorbate charge on Pt/C-Nafion catalyst layers over a wide range of temperatures (25-100degreesC) and pressures while maintaining potential control at all times. The cell was fabricated from Pyrex and silicon using standard microfabrication techniques and exhibits adequate corrosion resistance to the sulfuric acid electrolyte for accurate electrochemical measurements up to 100degreesC. Thin Pt/C-Nafion catalyst layers of 50-100 mug Pt/cm(2) were prepared at roughly 100% catalyst utilization, as determined independently by in situ hydrogen voltammetry and ex situ transmission electron microscopy analysis. Increasing the temperature from 50 to 100degreesC at 0.35 V-PdH resulted in a substantial increase in methanol electro-oxidation rates with an activation energy of 70 kJ/mol. This kinetic enhancement is not due to thermal desorption of the poisoning adlayer, as determined by experiments showing the adlayer to be stable in flowing electrolyte at 95degreesC for durations up to 15 min. These results also show that the technique is able to perform the methanol oxidation and poisoning adlayer determinations without any significant effects of oxygen or other homogeneous contamination.