Preliminary studies on the influence of PtRu electrodeposits upon the rate of ethanol oxidation have shown a promoting effect with increasing concentrations of ruthenium up to a Pt:Ru atom ratio of 40%. Ethanol oxidation at Pt-based catalysts occurs via parallel pathways producing CO2, acetaldehyde and acetic acid. The yields of these products are studied as a function of the atomic composition of PtRu electrodeposits. Based on the results of the previous work, five significant Pt:Ru electrodeposits were prepared and ethanol electrooxidation products were monitored in situ, using FTIR spectroscopy. The results indicate that the pathway producing acetic acid is responsible for the maximum activity observed at Ru contents around 40%. (c) 2005 Elsevier B.V. All rights reserved.