To find a more durable anode with high performance for direct ethanol fuel cells (DEFCs), the present study investigates a series of quaternary electrocatalysts, Pt30Ru30Ir40-xSnx/C (wt.%), for the ethanol electro-oxidation reaction (EOR). The carbon-supported Pt30Ru30Ir40-xSnx/C electrocatalysts were prepared by a known impregnation-reduction (borohydride) method. The microstructure and chemical composition were determined by X-ray diffraction (XRD), energy dispersive X-ray spectroscopy (EDX) and transmission electron microscopy (TEM). The activity of the electrocatalysts for EOR was compared to commercial Pt67Ru33/C (HISPEC5000) using linear sweep voltammetry (LSV) based on similar Pt loading. The results of this study show that electrocatalyst composition with 10 and 20% It (wt.%) exhibit higher electrocatalytic activity than the commercial PtRu electrocatalyst. The single fuel cell testing at 90 degrees C comparing Pt30Ru30Ir40-xSnx/C to commercial Pt67Ru33/C and Pt83Sm2/C anodes showed an enhancement of Pt activity (normalized to Pt loading) in the following order: Pt30Ru30Ir10Sn30 > Pt30Ru30Sn40 >= Pt30Ru30Ir40 >= Pt83Sn17 > Pt67Ru33. After a long-term performance test, the activity changed to the following order: Pt30Ru30Ir10Sn30 > Pt3oRu301r40 > Pt30Ru30Sn40 > Pt83Sn17 > Pt62Ru33. Pt30Ru30Ir10Sn30/C exhibited both a higher performance with a specific power density of 29 mWmg(Pt)(-1) without O-2 backpressure at the cathode and an excellent long-term stability in a DEFC operating at 90 degrees C. Crown Copyright (C) 2010 Published by Elsevier B.V. All rights reserved.