Yields were determined for the CO2 produced upon the electrochemical oxidation of 1.0 M methanol in 0. 1 M HC1O(4) at the following four fuel cell catalyst systems: Pt black, Pt at 10 wt.% metal loading on Vulcan XC-72R carbon (C/Pt, 10%), PtRu black at 50 at % Pt, 50 at % Ru (PtRu (50:50) black), and PtRu at 30 wt.% Pt, 15 wt.% Ru loading on Vulcan XC-72R carbon (C/PtRu, 30 wt.% Pt, 15 wt.% Ru). Samples were electrolyzed in a small volume (50 mul) arrangement for a period of 180 s keeping the reactant depletion in the cell below M. The dissolved CO, produced was determined ex situ by infrared spectroscopy in a micro-volume transmission flow cell. For the PtRu materials, the efficiencies for CO2 formation were near 100% at reaction potentials in the range between 0.4 V (versus the reversible hydrogen electrode (RHE), V-RHE) and 0.9 V-RHE. At the Pt catalysts, the yields Of CO2 approached 80% between 0.8 and 1.1 V-RHE and declined rapidly below 0-8 V-RHE. (C) 2003 Elsevier Ltd. All rights reserved.