Electro-oxidation of dimethyl ether (CH3OCH3, denoted as DME below) on Pt polycrystalline electrode has been investigated by electrochemical and in situ infrared (IR) measurements in acid solutions. A reaction intermediate species, (CH3OCH2-)(ad), has been observed in the low potential region as an initial product for dehydrogenation process of DME on Pt electrode surface. This species is subsequently decomposed to adsorbed carbon monoxide (CO) and finally oxidized to carbon dioxide (CO2) in higher potential region. The time-resolved IR measurement is employed to follow the transient process of the formation and decomposition of the intermediate on Pt electrode surface. Based on these electrochemical and IR spectroscopic results, a reaction scheme for DME electro-oxidation process is proposed. (C) 2008 Elsevier Ltd. All rights reserved.