Direct dimethyl ether fuel cells (DDMEFCs) were investigated using proton-conducting Sn0.9In0.1P2O7 as an electrolyte at intermediate temperatures between 150 and 300 C. Fuel cell operation at intermediate temperatures allowed a Pt/C anode to achieve excellent CO tolerance and high catalytic activity for the anode reaction of DME. The catalytic activity of the Pt/C anode was further improved by the addition of Ru to Pt, especially at elevated temperatures. The anodic overpotential and anode product measurements revealed that the H-2 produced by the reforming reaction of DME was electrochemically oxidized at the PtRu/C anode, which proceeded in parallel with the direct oxidation reaction of DME. As a result, DDMEFCs with the PtRu/C anode achieved a peak power density of 31, 52, and 78 mW cm(-2) at 200, 250, and 300 degrees C, respectively. (c) 2007 The Electrochemical Society.