The reactivity of the Ru(0 0 0 1) electrode towards the adsorption and electrooxidation of CO and methanol has been studied by variable-temperature in situ FTIR spectroscopy in both perchloric acid and sodium hydroxide solution, and the results interpreted in terms of the surface chemistry of the Ru(0 0 0 1) electrode. Both linear (COL) and threefold hollow (COH) binding CO adsorbates (bands at 1970-2040 and 1770-1820 cm(-1), respectively) were observed on the Ru(0 0 0 1) electrode in both 0.1 M HClO4 and 0.1 M NaOH solutions from the CO adsorption. In the acid solution, COL was detected as the main adsorbed species on Ru(0 0 0 1) surface over all the potential region studied. In contrast, in the alkaline solution, more COH than COL was detected at lower potentials, whilst increasing the potential resulted in the transformation of COH to COL. At higher potentials, the oxidation of the adsorbed CO took place via reaction with the active (1 x 1)-O oxide/hydroxide. It was found that no dissociative adsorption or electrooxidation of methanol took place at the Ru(0 0 0 1) at potentials below 900 mV vs Ag/AgCl in perchloric acid solution at both 20 and 55 degreesC. However, in the alkaline solution, methanol did undergo dissociative adsorption, to form linearly adsorbed CO (COL) with little or no CO adsorbed at threefold hollow sites (COH) at both 20 and 55 degreesC. Increasing the temperature from 20 to 55 degreesC clearly facilitated the methanol dissociative adsorption to COL and also enhanced the electrooxidation of the COL. At the higher potentials, significant oxidation of methanol to CO2 and methyl formate in acid solution and to bicarbonate and formate in alkaline solution, was observed, which was attributed to the formation of an active RUO2 phase on the Ru(0 0 0 1) surface, in agreement with our previous studies. (C) 2003 Elsevier Ltd. All rights reserved.