Membrane electrode assemblies (MEAs) with PtRu/C and Pt/C as both sides electrocatalysts have been fabricated and used in a mixed-reactant alkaline fuel cell without bipolar plate. It has been found that the reactant selectivity of the electrocatalyst is tunable by changing the electrode hydrophobicity. The measurement on a three-cell stack with MEAs using a more hydrophobic PtRu/C electrode and a more hydrophilic Pt/C electrode in an ethanol/oxygen mixed solution shows that the PtRu/C electrode serves as a cathode and Pt/C electrode performs as an anode. The steady-state power density of 31 mW cm(-2) is achieved in an ethanol solution by continuously bubbling oxygen at ambient temperature and atmosphere pressure. (c) 2007 Elsevier B.V. All rights reserved.