In the present study, anode degradation of a direct dimethyl ether fuel cell (DDFC) has been investigated after a 70.5 h discontinuous galvostatic operation at 60 degrees C under ambient pressure. Cyclic voltammetry and electrochemical impedance spectroscopy show that the anode performance decreases after the durability test. Characterizations of XRD and TEM confirm the growth of Pt particles (from 3.0 nm to 5.5 nm) during durability test, which causes the loss of anode electrochemical active surface (EAS). Cyclic voltammetry reveals that poisoning of catalyst by absorbed DME oxidation intermediates species is another cause of anode degradation. And the dissolution of anode Pt is not observed through energy dispersive analysis of X-ray (EDAX) during the durability test. In a companion article (Part II), the effect of cathode degradation on the long-term performance of DDFC is investigated. (C) 2011 Elsevier B.V. All rights reserved.