Reaction mechanisms of ethanol decomposition on Rh(1 1 1) were elucidated by means of periodic density functional theory (DFT) calculations and kinetic Monte Carlo (KMC) simulations. We propose that the most probable reaction pathway is via CH(3)CH(2)O* on the basis of our mechanistic study: CH(3)CH(2)OH* -> CH(3)CH(2)O* -> CH(2)CH(2)O* -> CH(2)CHO* -> CH(2)CO* -> CHCO* -> CH* + CO* -> C* + CO*. In contrast, the contribution from the pathway via CH(3)CHOH* is relatively small, CH(3)CH(2)OH* -> CH(3)CHOH* -> CH(3)CHO* -> CH(3)CO* -> CH(2)CO* -> CHCO* -> CH* + CO* -> C* + CO*. According to our calculations, one of the slow steps is the formation of the oxametallacycle CH(2)CH(2)O* species, which leads to the production of CHCO*, the precursor for C-C bond breaking. Finally, the decomposition of ethanol leads to the production of C and CO. Our calculations, for ethanol combustion on Rh, the major obstacle is not C-C bond cleavage, but the C contamination on Rh(1 1 1). The strong C-Rh interaction may deactivate the Rh catalyst. The formation of Rh alloys with Pt and Pd weakens the C-Rh interaction, easing the removal of C, and, as expected, in accordance with the experimental findings, facilitating ethanol combustion. (c) 2010 Elsevier B. V. All rights reserved.